Theme: Hereditary
neuro-muscular diseases:
primary myodystrophies (Erb-Rot, Duchenne, Dejerine),
neurogenic amyotrophies
(Werdnig-Hoffmann, Kugelberg-Velander, Aran-Duchenne,
Charcot-Marie-Tooth),
Thomson myotonia, paroxysmal myoplegia, Myasthenia Gravis
Hereditary - degenerative diseases with dominant lesion of
pyramidal (Schtrumpel’s paraplegia), extrapyramidal (Parkinson’s disease,
Hepatolenticular degeneration (Wilson’s disease), Torsion dystonia (spasm),
Huntington’s chorea) system and cerebellum (Friedreich’s and Mary ataxias)
All the hereditary diseases of nervous system are
divided into:
1. Diseases
with involvement of nervous – muscle
synapse:
A. Myasthenia
B. Myasthenic
syndromes
2. Hereditary
diseases with involvement of pyramidal
system:
A. Spastic
paraplegia of Shtrumpel
B. Family
spastic paralysis with amyotrophy, oligophrenia, retina degeneration (described
by Kellin)
C. Family
spastic paralysis with ichthyosis and oligophrenia
3. Diseases
with involvement of extrapyramidal
system:
A. Hepato
– cerebral degeneration
B. Dystonia
C. Double
athetosis
D.
E. Parkinson
disease
F. Myoclonus
– epilepsy
G. Tourette
syndrome
H. Hereditary
trembling
I. Rulph
seizure
J. Palpebral
– mandibular synkinesis
4.
Hereditary
ataxia
A. Spinal
ataxia of Fridreich
B. Hereditary
cerebellar ataxia of Pier – Mary
C. Olivo
– ponto – cerebellar degeneration
D. Refsum
disease
E. Rusi
– Levina disease
F. Marinesku
– Shagrena disease
G. Lichtenshtein
– Knorr disease
5. Diseases
with involvement of neuro – muscular
junction:
I.
Progressive
muscular dystrophy
A. Dushen
pseudo – hypertrophic muscle dystrophy
B. Late
Bekker pseudo – hypertrophic muscle dystrophy
C. Myodystrophy
Emeri – Dreiphus
D. Family
visceral myopathy
E. Shoulder
– scapula – facial form of Landuzi – Degerina
F. Scapula
– peroneal form of Davidenkova
G. Erba
dystrophy
H. Ophthalmoplegic
myopathy
I. Dystal
myopathy of Wallender
J. Inborn
nonprogressive forms of myopathy
II. Amyotrophy as a result of peripheral neuron
lesion
A. Spinal
amyotrophy of Werding – Hoffman
B. Proximal
amyotrophy of Kukelberg – Welander
C. Kennedy
amyotrophy
D. Sharkot
– Marie – Tooth disease
E. Hypertrophic
neuritis
6. Family
– hereditary myotonia:
A. Myotonia
Tomsena
B. Atonic
myotonia
C. Paramyotonia
of Alenburg
D. Chondro
– dystrophic myotonia
7. Hereditary
diseases with paroxysmal states:
A. Paroxysmal
family myoplegia
B. Episodic
hereditary adynamia
C. Mac
– Ardel disease
D. Episodic
myotonic adynamia of Bekker
Myasthenia
Myasthenia
gravis (MG) is caused by a defect of neuromuscular
transmission due to an antibody-mediated attack on nicotinic acetylcholine
receptors (AchR) at neuromuscular junctions. It is characterized by fluctuating
weakness that is improved by inhibitors of cholinesterase.
Incidence
MG is a common disease. An
apparent increase in the incidence of the disease in recent years is probably due
to improved diagnosis. According to Phillips and Torner (1996), the prevalence
rate is 14 per 100,000 (or about 17,000 cases) in the United States. Before age
40 years, the disease is three times more common in women, but at older ages
both sexes are equally affected.
There
are few familial cases of the disease, but disproportionate frequency of some
HLA haplotypes (B8, DR3, DQB1) in MG patients suggests that genetic
predisposition may be important. Other autoimmune diseases also seem to occur
with disproportionate frequency in patients with MG, especially hyperthyroidism
and other thyroid disorders, systemic lupus erythematosus, rheumatoid
arthritis, pernicious anemia, and pemphigus.
Pathogenesis
The
polyclonal IgG antibodies to AChR are produced by plasma cells in peripheral
lymphoid organs, bone marrow, and thymus. These cells are derived from B cells
that have been activated by antigen-specific T-helper (CD4+) cells. The T-cells
have also been activated. In this case by binding to AChR antigenic peptide
sequences (epitopes) that rest within the histocompatibility antigens on the
surface of antigen-presenting cells.
The
AChR antibodies react with multiple determinants, and enough antibody
circulates to saturate up to 80% of all AChR sites on muscle. A small
percentage of the anti-AChR molecules interfere directly with the binding of
ACh, but the major damage to endplates seems to result from actual loss of
receptors due to complement-mediated lysis of the membrane and to acceleration
of normal degradative processes (internalization, endocytosis, lysosomal
hydrolysis) with inadequate replacement by new synthesis. As a consequence of
the loss of AChR and the erosion and simplification of the endplates, the
amplitude of miniature endplate potentials is about 20% of normal, and patients
are abnormally sensitive to the competitive antagonist curare. The
characteristic decremental response to repetitive stimulation of the motor
nerve reflects failure of endplate potentials to reach threshold so that
progressively fewer fibers respond to arrival of a nerve impulse.
Most
AChR antibodies are directed against antigenic determinants other than the ACh
binding site. Nevertheless, the summed effects of the polyclonal anti-AChR
antibodies with differing modes of action result in destruction of the
receptors. Physiologic studies indicate impaired postsynaptic responsiveness to
ACh, which accounts for the physiologic abnormalities, clinical symptoms, and
beneficial effects of drugs that inhibit acetylcholinesterase.
Clinical features
The typical sign
of myasthenia is muscles weakness. One of the most specific features of this
weakness is its increasing with movements. The disease develops at the age of
20 – 30 years old. Before age 40 years, the disease is three times more common
in women, but at older ages both sexes are equally affected. The disease is
developed subacutely or chronically in most cases.
According to the course of the disease
there are such forms:
1. Progressive
2. Stationary
3. Mysthenic
episodes
|
Clinical forms:
1. Ophthalmic
2. Bulbar
3. Skeletal
4. General
Ophthalmic The most
common signs are ptosis, diplopia and eyes movement disturbances. Typical
features:
1. Asymmetric
lesion
2. Dynamic
symptoms (the signs increase in the evening)
Ophthalmoplegia is a very common
symptom. The other ones are:
- Weakness of mimic muscles – especially oral muscles.
- Weakness of chewing muscles.
- Weakness of pharyngeal, laryngeal muscles and muscles
of tongue
- Tongue muscles function disorders
- Breathing
disturbances
- Extremities
function disturbances (especially proximal parts)
- Neck muscles weakness
– hanging of the head
- Body muscles
weakness that leads to duck – like gait
Sensory and pelvic disorders usually are
not observed.
Diagnosis
1. Complains
on general weakness that increases in the evening
2. Early symmetric
lesion of external eyes muscles
Tests for this disease revealing
The patient is asked to look upwards or inside during 30
seconds in order to cause ptosis. He is asked to read text aloud in order to
cause dysarthria. The patient is asked to make 100 chewing movements in order
to reveal the weakness of these muscles.
Proserine test. Proserine is
introduced in dose 1.5 – 3 ml s/c, sometimes Atropinum is used in order to
prevent side effects. In 20 – 40 min all the signs of myasthenia disappear. In 2
– 3 hours all the symptoms appear again.
EMG – myasthenic
reaction. Test is positive in 85% of patients with skeletal form.
Muscle
biopsy – muscle atrophy and signs of degeneration.
CT reveals
timoma signs. In 90% of all patients antibodies to ACHR are found.
X-rey
examination
Differential
diagnosis
§
Botulism
§
Neurasthenia
§
LAS
§
Polineuropathy
§
Muscles dystrophy
§
Inflammatory myopathy
§
MS
§
Stroke in v/b region
§
Brain stem tumor
Treatment
1. Compensation
of neuro – muscular transference
2. Thymus
influence
3. Correction
of immune disorders
1. Anticholinestherase
medicines –
Caliminum
– 30 mg 3 times per day.
Proserinum
– 0.5 – 1.5 mg s/c
2. K drugs 3 –
3. Corticoids
– we start from 15–20 mg a day, than
increase gradually on 5 mg every 3 day
4. Anabolics
– Retabolil 50 mg once every 3 days, 5 – 6 injections.
5. Immune
suppressors – Asatioprinum in dose 50 – 150 – 200 mg per day
6. Plasmapheresis - at acute and progressive form
7. Radiation
therapy of thymus
8. Methabolic
drugs
At myasthenia crisis:
§
Plasmapheresis
§
Ig i/v (
§
Corticoids (100 mg prednisonum)
§
Proserinum 1 – 2 ml i/v
§
SLV, oxygen
§
Halloperidolum at excitation
Cholinergic crisis
There
fasciculations, seizures, bradycardia, salivation, hyperhydrosis and abdominal
pain.
Treatment
– Atropinum 1 ml 0.1 % s/c or i/v.
DISORDERS OF THE NEUROMUSCULAR
JUNCTION
Myasthenia Gravis
Definition
Myasthenia gravis is characterized by progressive muscular weakness on exertion, followed by
recovery of strength after a period of rest. It is an autoimmune condition in
which there is an antibody-mediated autoimmune attack directed against acetylcholine receptors at neuromuscular junctions.
The
In physiological muscle contraction, the impulse
generated in the motor neuron reaches the presynaptic
membrane, causing depolarization, which results in a coordinated release
of acetylcholine. The acetylcholine diffuses across the cleft in
sufficient quantity to produce a wave of depolarization that is propagated down
the muscle fiber. The propagated electrical discharge produces changes in the sarcoplasmic reticulum of the muscle fiber,
with release of calcium ions, which promotes fiber contraction. There is an
ample reserve of acetylcholine receptors
sufficient in number to allow repetitive depolarization of the membrane and
repeated muscle fiber contraction.
Etiology and Pathology
The postsynaptic membrane
is abnormal in myasthenia gravis. There
is a loss of secondary folds, which reduces the surface area available for
binding of acetylcholine, and there is a
decreased number of acetylcholine receptors.
The decrease is due, in part, to the blocking of acetylcholine binding sites of the acetylcholine
receptor by blocking antibodies. In addition, there is an accelerated
degradation of receptors, because antibodies cross-link the receptors, which
are drawn together in clusters, internalized by endocytosis, and degraded.105
The antibodies vary in their capacity to block receptor binding sites or
accelerate degradation, but increasing activity of antibodies appears to be
associated with increasing
severity of the myasthenic response. During repetitive
stimulation of the nerve, the available acetylcholine
receptors are quickly saturated and remain refractory. This results in
a state of receptor insufficiency in which there is not a sufficient number of
receptors available to bind acetylcholine and
produce depolarization. Therefore, repetitive stimulation will result in a
decrease in the number of muscle fibers that are able to respond, as each neuromuscular junction reaches a state of receptor
insufficiency. Clinically, this is characterized by a progressive weakness.
The antibodies, which are of the IgG class, are
probably produced by B lymphocytes, although T lymphocytes from patients with myasthenia gravis respond to stimulation with acetylcholine receptors, and the production of acetylcholine receptor antibodies. The
autoimmune response probably arises in the thymus,
because 70 percent of patients with myasthenia
gravis have hyperplasia or thymomas, which are of microscopic size in rare
cases, and thymectomy is an effective
treatment in most cases. The normal and myasthenic
thymus contains myoid (muscle-like)
cells with surface
acetylcholinic receptors.
These cells may be particularly susceptible to an immune
reaction, possibly triggered by a viral infection, resulting in changes to the
myoid cells and the surrounding lymphocytes within the thymus, and an autoimmune response. One possible mechanism is molecular
mimicry, in which there is an immune response to an infectious agent such as
herpes simplex virus, which contains a peptide sequence
homologous to a sequence on the acetylcholine receptor
subunit.
However, not all myasthenics
show detectable levels of antibodies to acetylcholine
receptors, implying that myasthenia
gravis is not a homogenous disorder, and that other, as yet undetected,
antibodies may occur in some cases.
Clinical Features
Myasthenia gravis is uncommon, with a prevalence of about 1/10,000. The disease is more
common among women than men, with a ratio of 2:1. The mean age of onset is 26
years in women and 31 years in men. The incidence in men does not show a smooth
distribution. The peak incidence in the early thirties declines through middle
age, but there is a second peak between 60 and 78 years of age in men. Why this
does not occur in women is unknown. The disease can occur at any age and has
been reported in the newborn. There is no significant family occurrence and no genetic
pattern has been identified.
Myasthenia gravis can be classified into four groups, or types:
Group 1. Ocular myasthenia.
Group 2. Mild generalized myasthenia.
Group 3. Severe generalized myasthenia.
Group 4. Crisis.
Ocular
Myasthenia In this form of myasthenia gravis, the symptoms and signs are
confined to the extraocular muscles. The
paient develops diplopia and ptosis, usually toward the end of the day.
Ocular myasthenia remains localized to
the extraocular and eyelid muscles in about
15 percent of cases, but about 85 percent of patients develop generalized myasthenia within a period of 18 months.
Nevertheless, ocular myasthenia differs
from generalized myasthenia because of
male preponderance, low antibody titers, and
different histocompatibility and antigen
association. Symptoms consist of unilateral or bilateral ptosis and diplopia.
The degree of ptosis is variable
and may present on one side or the other at different times. There may be quick
lid retraction or twitching of the levator palpebrae
elicited by having the patient rapidly redirect the gaze from a downward to a
neutral position. Eye movements may be saccadic,
jerking, or quivering, with gaze-evoked nystagmus.
Mild Generalized Myasthenia Mild generalized myasthenia may be preceded by ocular myasthenia or may present with symptoms of
mild weakness involving the extraocular muscles
and other muscle groups. There is usually some involvement of the facial
muscles, muscles of mastication, and the proximal limb-girdle muscles, while
the extraocular muscles are frequently
but not invariably involved. This may present with some difficulty in diagosis,
particularly when the proximal limb-girdle musculature is the sole site of
presentation. When mild generalized myasthenia develops
into the severe generalized form of the disease, the transition usually occurs
within a period of 18 months.
Severe Generalized Myasthenia In the severe generalized form of myasthenia
gravis, there is sufficient weakness of the bulbar and limb girdle musculature to produce marked restriction
in activity. Exercise tolerance is reduced, the patient has a sedentary
existence, and there is a constant risk of respiratory insufficiency,
respiratory infection, or respiratory failure.
Crisis Myasthenic crisis
may be defined as myasthenia gravis with
respiratory failure. This is a life-threatening situation that develops in
patients with severe generalized myasthenia. The
onset is often sudden, and crisis is often precipitated by an infection. This
usually takes the form of an upper respiratory tract infection that progresses
to severe bronchitis or pneumonia.
The stages of myasthenia
are not fixed, and it is not unusual for progression to occur from one
stage to another within a period of 18 months. Remission can occur in any of
the first three stages of myasthenia gravis. However,
remission usually occurs within
the first 18 months of the disease and is rare at a
later stage. Spontaneous remission can be expected in about 25 percent of cases
but lasts no longer than 2 years"
At the initial interview, the patient with myasthenia gravis should receive a full generalized
physical examination, which helps to exclude a number of conditions known to
be associated with myasthenia gravis, particularly
thyrotoxicosis. This is followed by a
full neurological examination, with careful documentation of the degree of muscle
involvement. The examiner should attempt to demonstrate progressive weakness of
the affected muscles. In the patient with ptosis,
the examiner measures the widths of the palpebral
fissures, and the patient is then asked to sustain upward gaze. This will
produce an increasing degree of ptosis, which
can be observed and measured. Similarly, patients with diplopia can be asked to sustain gaze in the direction of the pull
of the involved muscle, and the examiner may observe increasing deviation of
the ocular axis while the patient complains of progressive diplopia and further separation of the two
images. Patients with weakness of the masseters can be asked to bite down on a
tongue blade while the examiner attempts to withdraw it. This maneuver will produce
fatigue of the masseters, and biting will not be sustained after a short period
of time. The patient with a generalized form of the disease may show
increasing weakness on stressing any of the muscles involved in the disease
process. When the hands are involved, it is possible to obtain a quantitative
measure of weakness using a dynamometer.
Diagnostic Procedures
1. Edrophonium
(Tensilon) test. Edrophonium is a
rapidly acting anticholinesterase inhibitor
that blocks the action of acetylcholinesterase. Hydrolysis
of acetylcholine is prevented, thus
allowing more time for an attachment of acetylcholine
molecules to receptor sites. The test is performed as follows:
The examiner selects a weak muscle. For example, if
the patient has ptosis, the width of the palpebral fissure can be measured. If the
patient has diplopia, the degree of
deviation of the ocular axis can be estimated; or if the patient has weakness
on chewing, the time that the patient is able to sustain biting of the tongue
blade can be recorded. The examiner then draws 10 mg (1 mL) edrophonium into a syringe. The test begins
with the intravenous injection of 2 mg (0.2 mL) edrophonium
into a vein in the forearm. The examiner then waits 30 s to make sure
that the patient does not have any muscarinic reaction
to edrophonium. This usually consists of bradycardia, hypertension, lacrimation,
sweating, or abdominal colic. If this does not occur, the remaining 8 mg (0.8
mL) edrophonium is injected. If the test
is positive, there will be a dramatic response, with increasing strength of
the paretic muscle within a period of 30
s. This increasing strength usually lasts about 2 min, then disappears.
However, the patient will usually express an appreciation of the increasing
strength of the weakened muscle, and the examiner will be able to observe this
effect. The test is safe to perform, and adverse effects are unusual. If severe
muscarinic adverse effects occur, they
can be rapidly resolved by intravenous injection of 0.4 mg atropine.
2. Electromyography and
repetitive nerve stimulation. Needle electrode myography
is performed in patients with suspected myasthenia
gravis or in those who have disorders affecting the neuromuscular junction, which may mimic or
coexist with myasthenia gravis, including
Lambert-Eaton myasthenic syndrome,
drug-induced myasthenic syndrome,
peripheral neuropathies, or myopathies, all
of which may present with progressive fatigue on exertion. This is
particularly valuable when the Tensilon test
is equivocal but should also be performed when it is positive. In myasthenia gravis, the electromyogram shows
variation in amplitude of motor unit action potentials measured on an
oscilloscope on sustained voluntary contraction. This is a result of
intermittent failure of synaptic transmission
of some of the muscle fibers involved in the motor unit action potential. The
abnormality is reversed by administration of edrophonium
in patients with myasthenia gravis.
Conventional electromyography
should be followed by repetitive nerve stimulation. Cholinesterase
inhibitors should be discontinued for at least 12 h before testing. Repetitive
nerve stimulation at rates of 3 to 5 Hz, and a
supramaximal stimulus of 25 to 50 percent greater than the stimulus
intensity necessary to activate all muscle fibers, should be used. In myas-
thenia gravis, the result is a decremental response greater than 10 percent to trains
of 3 to 5 Hz stimuli, indicating abnormal neuromuscular
transmission.111 Maximal voluntary contraction for 30 to 60 s
may be followed by partial repair of the decremental response, followed by
postcontraction exhaustion 3 to 4 min later.
3. Elevated
levels of antibodies to acetylcholine
receptors occurs in most cases. Titers do
not provide a measure of the severity of the disease but can be used to monitor
the effect of treatment on an individual basis.
Failure to detect antibody levels occurs in about 10
to 15 percent of cases, with a generalized form of myasthenia in about 50 percent of cases with ocular myasthenia.
Patients with the generalized form of myasthenia gravis and negative serum
antibodies, who fail to respond to repetitive nerve stimulation, often have abnormal
response to single fiber electromyography. This
technique can also be applied to the extraocular
muscles for the diagnosis of ocular myasthenia
gravis.112
4. Muscle
biopsy should be performed when the diagnosis is uncertain, and there is a
suspicion that there may be an underlying myopathic
process with myasthenic features,
such as polymyositis. Techniques for immunohistologic study
of motor end plates, and quantification of acetylcholine receptors, are available.
After a diagnosis of myasthenia
gravis has been established, a series of tests should be performed to rule
out associated diseases. These include: (1) a CT scan or MRI scan of the chest
should be obtained to eliminate the possibility of a thymic tumor, which occurs in about 18 percent of cases with myasthenia gravis, particularly in elderly men;
(2) thyroid function tests should be performed to eliminate the possibility
of hyperthyroidism. Thyrotropin-binding
inhibitory immunoglobulin determination
is indicated in myasthenia gravis patients
with exophthalmus and normal thyroid function"1; (3) an associated
collagen vascular disease should be ruled out by appropriate testing, including
antinuclear antibodies (ANA), anti-DNA antibodies, anticardiolipin, SSA and SSB
antibodies, rheumatoid factor, and complement C3, C4, and CH-50. This will
tend to eliminate collagen vascular diseases such as systemic lupus erythematosus,114 myxedema,
thyrotoxicosis, or rheumatoid arthritis; (4) patients with a severe
generalized form of the disease should have respiratory function tests
performed as soon as the diagnosis is suspected, and every 12 h during
treatment, or whenever respiratory insufficiency is suspected. Tests include
determination of respiratory muscle strength by testing maximal expiratory
pressure (PEmax), maximal inspiratory
pressure (PImax), and vital capacity. PEm]n and PEmax
are more sensitive indicators of early respiratory muscle weakness than
vital capacity. However, in general, elective endotracheal
intubation is performed when the vital capacity is less than 10 to 15
mL/kg. Although respiratory impairment is usually attributed to weakness of the
diaphragm and chest wall muscles, upper airway obstruction should also be
considered and can be demonstrated by inspiratory
and expiratory flow volume loop determination.
Arterial blood gases are not a reliable method of
monitoring patients with myasthenia gravis because
the carbon dioxide level can remain deceptively normal until just before
respiratory failure.
Differential Diagnosis
1. Polymyositis. The patient with polymyositis may have symmetrical proximal
limb-girdle muscle weakness. Some patients show a positive response to edrophonium and the diagnosis can be
established only by electromyography and
muscle biopsy.
2. Thyrotoxicosis.
Thyroid myopathy presents
as a proximal limb-girdle muscle weakness. The association of myasthenia gravis and thyrotoxicosis is not unusual, and the presence of myasthenia gravis in a patient with thyrotoxicosis can be suspected if improvement
is seen following the edrophonium test. Patients
with thyroid myopathy usually do not show
improvement following the intravenous administration of edrophonium.
3.
Exophthalmic ophthalmoplegia may
be progressive and may resemble myasthenia
gravis in the early stages. There is progressive weakness of the extraocular muscles, with replacement of
muscle by fat and marked fatty infiltration of the orbit, producing
ex-ophthalmus. The response to edrophonium is
absent,
but thyrotropin-binding inhibitory immunoglobulin determination is positive and
particularly indicated in myasthenia gravis patients
with exophthalmus and normal thyroid function. Exophthalmic ophthalmoplegia and myasthenia gravis can coexist, in which case the response to edrophonium may be positive.
4. Myasthenic syndrome
(Lambert-Eaton syndrome). This condition is rare and occurs in association with neoplasia. The muscle weakness involves the
proximal limb-girdle muscles and the diagnosis can be established by the
characteristic findings on electromyography (see
p. 649).
5. Mitochondrial myopathies (see p. 649) including
chronic progressive external ophthalmoplegia, presenting
with ptosis and weakness, increasing with
exertion, will occasionally respond to anticholinesterase
therapy. Such cases have appropriate responses on electrophysiological testing, including
single fiber electromyographic studies. However, anti-acetylcholinesterase antibodies
are negative. Muscle biopsy will
confirm the presence of mitochondrial myopathy in
seronegative cases.
6. There may
be more than a chance but rare association between myasthenia gravis and sarcoidosis.
7. The
association of myasthenia gravis in lymphoma has been reported.
8. Myasthenia gravis might be one of the neuromuscular complications of HIV infection.
9. Periodic
paralysis.
10. Botulism.
11.
Miscellaneous (penicillamine,
acetylcholinesterase agents, particularly
organophosphorous compounds).
Table 20-3
Drugs Which May Induce or Exacerbate Myasthenia
Gravis
Antibiotics |
|
ampicillin |
kanamycin |
ciprofloxacin |
lincomycin |
clindamycin |
neomycin |
colistin |
polymyxin |
erythromycin |
streptomycin |
imipenem |
tobramycin |
Anesthetics |
|
ether |
ketamine |
halothane |
methoxyflurane |
Anticonvulsants |
|
phenytoin sodium |
trimethadione |
Antiarrthymics |
|
beta adrenergic receptor |
Other agents |
blockade |
procainamide |
acebutolol |
quinidine sulfate |
oxprenolol |
verapamil |
practolol |
|
propranolol |
|
timolol |
|
Anticholinergics |
|
trihexyphenidyl HC1 |
|
Antirheumatic |
|
chloroquine |
D-penicillamine |
Immunosuppressives |
|
corticosteroids |
interferon alpha |
Psychotropics |
|
amphetamines |
bromperidol |
amitriptyline |
haloperidol |
barbiturates |
imipramine |
chlorpromazine |
lithium |
Miscellaneous |
|
Anticoagulants |
|
amantadine |
procaine |
carnitine |
radiocontrast media |
chlorine gas |
a) iothalamic acid |
levonorgestrel |
b) diatrizoate megulmine |
methocarbamol |
magnesium citrate |
nicotine transdermal |
|
Modified from Wittbrodt
ET: Drugs and
myasthenia gravis. An update. Arch Intern Med 157:399, 1997.
Treatment
Group 1 and group 2 patients may be treated as outpatients.
Group 3 patients should be admitted to the hospital. Certain drugs may induce
or exacerbate myasthenia gravis (Table
20-3).
1. The anticholinesterase drugs were the first
effective treatment for myasthenia gravis and
are still widely used. Some evidence suggests that anticholinesterase drugs may increase damage to the postsynaptic membrane, and there is a present
trend to restrict the use of anticholinesterase drugs
to those with mild disease who show good response.
Patients with mild myasthenia
should be given pyridostigmine bromide
(Mestinon) 30 mg q4-6 h or neostigmine
bromide (Prostigmin) 15 mg over the same time period. Pyridostigmine bromide time-tablets (180 mg)
have a longer duration of action and may be used at night. At the next outpatient
visit, a Tensilon test should be
performed immediately before the next dose of the anticholinesterase preparation. If the test is positive, the
physician has the option of increasing the dosage or decreasing the time
between administration of the anticholinesterase
drugs. In this way, the optimum dose of pyridostigmine
or neostigmine can be calculated
for each patient. The response to anticholinesterase
drugs is good in about 50 percent of patients. Administration of anticholinesterase drugs may be limited by the
development of cholinergic side effects,
including colic, diarrhea, blurred vision, and bradycardia.
Care is needed in administration of anticholinesterase
drugs to the elderly because accumulation of acetylcholine at receptor sites in the heart may result in bradycardia, nodal rhythm, atrial fibrillation, or flutter. Hypotensive syncope has also been recorded.
Patients with group 3, or the severe generalized form
of myasthenia, should always be admitted
to the hospital for treatment. Following admission, an intravenous catheter
should be placed; this facilitates the performance of the Tensilon test. The patient is then given 60 mg pyridostigmine orally. The Tensilon test is performed just before the next
dose is due, and the dose of medication is increased if the test is positive.
Again, this method allows the development of the optimum dose for the patient.
2. Corticosteroids
are widely used in the treatment of myasthenia
gravis and probably act as an immunosuppressant,
suppressing the action of B lymphocytes. All patients scheduled to
receive corticosteroids should be
screened for tuberculosis, and those with oropharyngeal
involvement or respiratory impairment should be treated with plasmapheresis until there is improvement in
muscle strength. At that point, prednisone 100
mg/day (methylprednisolone 96 mg/day) is started and maintained for 10 days,
followed by alternate-day therapy at the same dose, which is monitored until
the maximum benefit is ob tained. The dose is gradually decreased until the patient
shows signs of weakness, then increased by a small amount. This is the
maintenance dose, which can be continued indefinitely in most cases. Anticholinesterase drugs can be reduced or
eliminated in many cases, and the morbidity of thymectomy
is reduced, particularly following surgery.
Remission or marked improvement can be expected in 75
percent of cases treated with high-dose oral corticosteroids.
Nevertheless, about 30 percent of patients show temporary worsening,
lasting about 6 days, during the first 3 weeks of high-dose therapy.This
complication can usually be managed with anticholinesterase
drugs or can be avoided by introducing steroids in low dosage (prednisone 10 to 25 mg/day) and gradually
increasing by 10-mg increments every 5 days until maximum improvement occurs.
The dose can then be decreased, using an alternate-day regimen, as described
above, until the maintenance dose is established.
Adverse effects of corticosteroid
therapy are inevitable if high-dose therapy is prolonged. The adverse
effects include cushingoid appearance, weight gain, hypertension, cutaneous
striae, diabetes melli-tus, cataracts, peptic ulcer, osteoporosis, and aseptic
necrosis of the femoral head. A weight maintenance diet with low sodium and
supplementary calcium is indicated. At the patient's first complaint of
gastritis, H2 antagonists should be used to prevent the development
of peptic ulcer.
3. Thymectomy is recommended for patients between the ages of
puberty and 60 years or those who have generalized myasthenia gravis. Thymectomy is usually delayed until after
puberty because of the significant role of the thymus
in the development of the immune system. The results of thymectomy are better in those with nonneoplastic thymic hyperplasia than in those
with thymoma, but the latter should always
be removed, because of the propensity for local invasion, including spread into
the lungs.
The surgical approach to thymectomy involves splitting the sternum and exploring the
anterior mediastinum. This permits the removal of the thymus (or thymoma) and any ectopic thymic tissue in the mediastinum or
lower cervical area. The alternative methods of cervical thymectomy and transcervical
thymectomy carry less morbidity but may fail to detect
ectopic thymic tissue. This is less likely with newer fiberoptic technology (thoracoscopy) or visual-assisted thoracoscopy, which provides complete visualization
of the thorax. The midline sternotomy is
necessary when the thymus is large or
when a thymoma is adherent to vascular
structures.
Recurrence of thymoma is
rare, the reoperative rate reported as 3.6 percent. Thymectomy may be followed by a drug-free remission or by marked reduction
in the need for anticholinesterase drugs
or other therapies. In some cases, improvement is delayed for months or years
after thymectomy, suggesting the
presence of residual thymic tissue. This
is often ectopic thymic tissue which was
not removed during surgery.
4. Immunosuppressant drugs. Azathioprine (Imuran)
acts predominantly on T cells and is useful in patients with myasthenia gravis when corticosteroids are ineffective or contraindicated. Treatment begins
with a first dose of a 50 mg tablet daily for 1 week. If there are no adverse
reactions to the drug, the dose can be increased gradually to 3.0 mg/kg per day
if necessary. This is usually effective, but the response is slow, and
improvement may not occur for many months.
Adverse effects include an influenza-like reaction in
about 10 percent of cases. Other adverse effects include leukopenia, anemia, thrombocytopenia, increase in liver enzyme levels, and
gastrointestinal upset. Azathioprine is often used in conjunction with corticosteroids and has a steroid-sparing
action, delaying the development of steroid side effects. Many patients require
lifelong azathioprine therapy, and any attempt to withdraw the drug without
introducing another therapy results in clinical relapse in approximately 50
percent of cases. A short course of corticosteroids
or plasmapheresis can be used to
control symptoms in such patients, while azathioprine is reintroduced.
5. Plasmapheresis acts by reducing circulating antibodies
against acetylcholine receptor and is an
accepted method for treating patients with myasthenia
gravis when other treatments have been ineffective.126 Plasmapheresis is effective alone or in
combination with azathioprine. The patient will show a good response to plasmapheresis within a short period of
treatment, and this response may be maintained for as long as 6 months. At
present, it seems that this form of therapy may have to be repeated at
intervals varying from 3 weeks to 6 months.
Plasmapheresis carries a risk of anaphylactic reaction
and viral infections, which can be eliminated by immunoadsorption. This
technique selectively removes acetylcholine receptor
antibodies by adsorption from the plasma, with reinfusion of fluid in the system
at the end of the procedure, thus eliminating the need for infusion of plasma
proteins used in plasmapheresis.
6. Intravenous immunoglobulin (IVIG). Improvement in myasthenia has been reported following a high
dose of intravenous human immunoglobulin 2
g/kg over 2 to 5 days, with increased muscle strength lasting several weeks.
Adverse effects including headaches, chills, fever, impaired renal function,
cerebral infarction, and aseptic meningitis have been reported. All patients
should be screened for impaired renal function before contemplating therapy.
7. Other
therapies. Antilymphocytic globulin and antithymocytic globulin have produced
improvement in some patients with myasthenia. Aminopy-ridines,
particularly 4-amino pyridine, facilitate
transmitter release at central and peripheral synapses, and may be of benefit
in refractory cases.
Treatment of Myasthenic
Crisis
Myasthenic crisis
should be regarded as a medical emergency. The condition generally results from
gradual failure of response to anticholinesterase
drugs. This failure may be precipitated by an upper respiratory tract infection,
pneumonia, extreme fatigue, or alcoholic intoxication. The artificial division
of patients into myasthenic crisis and cholinergic crisis is no longer tenable. The
patient who develops respiratory failure (vital capacity less than 10 to 15
mL/kg) should be diagnosed as crisis and treated as follows.
1. The
patient should be intubated, receive
mechanical ventilation, and be treated in an intensive care unit.
2. All
medications should be discontinued.
3. Because myasthenic crises are precipitated by
infection, a diligent search should be made for an infectious process. A chest
film should be taken to rule out pneumonia or atelectasis.
Infection requires prompt treatment with appropriate antibiotic therapy.
4. The
patient should be instructed to suction secretions from the mouth and pharynx
using a soft plastic catheter. In cases of extreme weakness, this must be done
regularly by those in attendance.
5. The
patient should be turned q2h in bed to prevent atelectasis
and encourage the flow of secretions from the lungs. This also helps to
prevent the development of decubiti.
6. When
patients are free from infection, or when infection is controlled by
appropriate antibiotics, corticosteroid therapy
can be commenced with 100 mg mefhylprednisolone intravenously piggyback daily. Corticosteroid therapy should be supplemented
by antacid therapy. The corticosteroids occasionally
produce increasing weakness beginning on the second or third day after therapy
is started, reaching a maximum effect on the fifth day. This is followed by
rapid recovery of strength. Some patients show an increase in strength
immediately following the administration of corticosteroids,
and in other patients, there may be no response for as long as 3 weeks.
When improvement occurs, the dosage of corticosteroids
can be converted to an alternate-day basis and then gradually reduced
once the patient shows good response to therapy.
7. The
patient should have respiratory function tests performed at the bedside at
least twice a day. The determination of vital capacity is often all that is
necessary, and the patient should be removed from the mechanical ventilator and placed on a T-bar with oxygen
when the vital capacity reaches 10 mL/kg.132
8. Once the
patient is extubated, treatment should be continued for a severe generalized
form of myasthenia gravis.
9. An
alternative form of treating patients in crisis is to perform plasmapheresis, which reduces the circulating acetylcholine receptor antibodies and often
produces dramatic improvement.
10. The
treatment of myasthenia gravis has
improved dramatically following the introduction of corticosteroids, immunosuppressants, plasmaphere sis, and IVIG. The
prognosis of crisis has improved following the widespread use of mechanical
ventilators and the wide range of drug therapies available.
DRUG-INDUCED MYASTHENIA SYNDROME
Drug-induced myasthenia
is characterized by reversible myasthenic
symptoms associated with a particular drug. Several drugs have been
reported to cause a reversible myasthenic syndrome
(see Table 20-3).
Lambert-Eaton Syndrome (Myasthenic
Syndrome)
Definition Lambert-Eaton
syndrome is believed to represent failure of
release of acetylcholine at the neuromuscular junction.
Etiology
The syndrome represents an autoimmune condition
associated with a number of neoplasms, more than 50 percent of which are
small-cell carcinoma of the lung. Noncancerous Lambert-Eaton
syndrome occurs in about one-third of cases and is associated with other
autoimmune disorders, including multiple sclerosis, rheumatoid arthritis, scleroderma, psoriasis, asthma, and ulcerative colitis. The syndrome is believed to
be due to the binding of an IgG antibody to voltage-gated calcium channels in
the nerve terminal. These channels fail to function when depolarization occurs,
leading to failure of fusion of acetylcholine-containing vesicles within the
nerve terminal membrane, and reduction and release of acetylcholine into the synaptic cleft.
Clinical Features
The disorder is characterized by proximal muscle
weakness, hyporeflexia, and autonomic dysfunction.
The weakness affects the proximal lower limb-girdle muscles, with minimal
involvement of the upper extremities and the ocular and facial muscles.
Autonomic dysfunction
results in sluggish pupillary reaction to light and photophobia, dryness of the mouth and failure of erection in
men. Hypo-hidrosis, orthostatic hypotension,
and bladder dysfunction may occur in some cases. Spontaneous respiratory
failure has been reported and there may be prolonged apnea or hypoventilation after
anesthesia.
Diagnostic Procedures
1. On electromyography, there is a low-amplitude
response to single stimulation and further decrease occurs with low rates of
stimulation. Higher rates of stimulation, such as 50 evoked potentials per
second, produce a marked increase in amplitude of the evoked motor unit
potential.
2. Between 50
and 60 percent of patients show antibodies directed at voltage-gated calcium
channels in the nerve terminal.
3. Chest MRI
and CT scans to reveal small-cell carcinoma of the lung are indicated in all
new cases of Lambert-Eaton syndrome.
Treatment
1. Remission
will occur in some cases, after removal of the neoplasm, but others remain symptomatic
despite tumor removal. Resumption of symptoms
after tumor removal
indicates tumor recurrence.
2. There may
be some improvement
in strength with anticholinesterase medication
such as pyridostigmine, but the response
is usually less effective therapy than in myasthenia
gravis.
3.
4-Aminopyridine, a potassium channel-blocking agent, enhances acetylcholine release and improves muscle
strength in Lambert-Eaton syndrome.
Seizures may occur with doses necessary to produce improved
strength. 3-4-Diaminopyridine,
with more potent action at the neuromuscular junction
and less convulsant properties, can be used alone or in combination with pyridostigmine and anticonvulsant medication, if necessary.
4. Immunosuppressant
therapy using prednisone or
azathioprine, singly or in combination, is effective in some cases.
5. Plasmapheresis or IVIG may be effective, but
the benefits are usually temporary.
6. Guanidine hydrochloride 25 mg tid, increasing slowly up
to 35 mg/kg per day, can be used as a last resort, because of adverse effects
including nausea, colic, renal and hematological
complications.
Congenital Myasthenic Syndromes
These rare disorders usually present in infancy or
childhood, but symptoms may be delayed in mild cases until adult life. There are
several conditions included in the syndrome, which should be suspected in
individuals showing progressive weakness on exertion, who have a negative
intravenous edrophonium test, and absence
of acetylcholine receptor antibodies. Electromyography, including single fiber
electromyogram, and muscle biopsy with electron microscopy are required to
establish the diagnosis.
Tick Paralysis
Definition
Tick paralysis is an acute onset of muscle weakness
proceeding to generalized paralysis associated with injection of venom through
the skin by a gravid female tick of Dermacentor andersoni, Der-macentor variabilis, and Dermacentor occidentalis
in North America and Ixodes holocyclus
or Ixodes cor-nuatis in
Etiology and Pathology
The condition appears to be caused by the absorption of
a toxic substance that prevents depolarization of the neuromuscular junction. There are no described pathological
changes.
Clinical Features
Tick paralysis has been reported in children of both
sexes, and there may be a history of exposure to ticks by playing in infested
grass or woods. The symptoms appear 3 to 5 days after the tick attaches itself
to the skin and are often preceded by malaise, irritability, and diarrhea. Weakness
begins in the lower extremities and spreads rapidly, so that the child shows
complete symmetrical paralysis of all voluntary muscles within 24 h. Bulbar or respiratory muscle involvement can
occur, and assisted ventilation may be necessary. Examination reveals the
presence of a tick that is attached to the skin and frequently obscured by hair
on the scalp of the patient.
Diagnostic Procedures
1. The history
of possible exposure to ticks may be obtained.
2. The
diagnosis is established by finding the tick.
Treatment Improvement
occurs when the tick is removed. This can be accomplished by the application
of petroleum jelly and removal some 20 min later, with forceps pressed down on
either side of the mouth parts, to grasp the hypostome of the tick, the gentle
detachment by lifting or an upward levering action.
Parkinsonism
Parkinsonism
– is a chronic progressive neurodegenerative syndrome that is characterized
by motor disorders as a result of extrapyramidal system involvement.
Parkinson disease (PD) – is a chronic progressive
degenerative disease of CNS that manifest as voluntary movements disorders. PD was
described by James Parkinson for the first time in 1817 as shaking paralysis.
Epidemiology The
prevalence of PD is 133 per 100 000 people. This disease is considered to be
one of the most common ones among old people after dementia, epilepsy, cerebral
vascular diseases. The beginning of the disease is at the age of 55. The most
common factors that lead to the disease are – old age, inheritance, toxic
agents.
Old age Every 10
years the person looses 8% of all neurons. But the symptoms of PD manifest only
when 80% of all neurons will be lost.
Inheritance The
inheritance of the disease can be proved by:
·
Association of PD with dementia
·
Rapid progress of the disease
Toxins There
are a lot of toxic substances that can provoke PD.
The
other reasons of PD development are:
·
Viral infections
·
Cerebral vessels sclerosis
·
Severe cranial trauma
·
Long lasting usage of neuroleptics,
reserpinum medicines
Pathogenesis The core
biochemical pathology in parkinsonism is decreased dopaminergic
neurotransmission in the basal ganglia. Degeneration of the nigrostriatal
dopamine system results in marked loss of striatal dopamine content.
Drug-induced parkinsonism is the result of blockade of dopamin receptors or
depletion of dopamine storage. It is not known how hydrocephalus or abnormal
calcium metabolism produces parkinsonism. Physiologically, the decreased
dopaminergic activity in the striatum leads to disinhibition of the subthalamic
nucleus and the medial globus pallidus, which is the predominant efferent
nucleus in the basal ganglia. Understanding the biochemical pathology led to
dopamine replacement therapy; understanding the physiologic change led to
surgical interventions, such as pallidotomy, thalamotomy, and subthalmic
nucleus stimulation.
Clinical
features The main signs of PD are:
1. Hypokinesia
2. Rigidity
3. Resting
trembling
4. Loss of
postural reflexes.
|
The
clinical features of tremor, rigidity, and flexed posture are referred to as positive
phenomena as reviewed first; bradykinesia, loss of postural reflexes, and
freezing are negative phenomena. In general, the negative phenomena are the
more disabling. Rest tremor at a frequency of 4 to 5 Hz is present in
the extremities, almost always distally; the classic "pill-rolling"
tremor involves the thumb and forearms Rest tremor disappears with action but
reemerges as the limbs maintain a posture. Rest tremor is al: common in the
lips, chin, and tongue. Rest tremor of the hands increases with walking and may
be early sign when others are not yet present. Stress worsens the tremor.
Rigidity is an increase of muscle tone that is
elicited when the examiner moves the patient's limbs, neck or trunk. This
increased resistance to passive movement is equal in all directions and usually
is mat by a ratchety "give" during the movement. This so-called
cogwheeling is caused by the underlying tremor even in the absence of visible
tremor. Cogwheeling also occurs in patients with essential tremor. Rigidity of
the passive limb increases while another limb is engaged in voluntary active
movement
The flexed posture commonly begins in the arms and
spreads to involve the entire body . The head is bowed, the trunk is bent
forward, the back is kyphotic, the arms are held in front of the body, and the
elbows, hips, and knees are flexed. Deformities of the hands include ulnar
deviation of the hands, flexion of the metacarpal-phalangeal joints, and
extension of the interphalangeal joints (striatal hand). Inversion of the feet
is apparent, and the big toes may be dorsiflexed (striatal toe). Lateral
tilting of the trunk is common.
Akinesia is a term used interchangeably with
bradykinesia and hypokinesia. Bradykinesia (slowness of movement,
difficulty initiating movement, and loss of automatic movement) and hypokinesia
(reduction in amplitude of movement, particularly with repetitive
movements, so-called decrementing) are the common features of parkinsonism,
although they may appear after the tremor. Bradykinesia has m; facets,
depending on the affected body parts. The face loses spontaneous expression
(masked facie: hypomimia) with decreased frequency of blinking. Poverty
of spontaneous movement is characterized by loss of gesturing and by the
patient's tendency to sit motionless. Speech becomes soft (hypophonia, and
the voice has a monotonous tone with a lack of inflection (aprosody). Some
patients do not enunciate clearly (dysarthria) and do not separate
syllables clearly, thus running the words together (tachyphemia). Bradykinesia
of the dominant hand results in small and slow handwriting (micrographia and
in difficulty shaving, brushing teeth, combing hair, buttoning, or applying
makeup. Playing mi instruments is impaired. Walking is slow, with a shortened stride
length and a tendency to shuffle; swing decreases and eventually is lost.
Difficulty rising from a deep chair, getting out of automobiles and turning in
bed are symptoms of truncal bradykinesia. Drooling saliva results from failure
to swallow spontaneously, a feature of bradykinesia, and is not caused by
excessive production of saliva. The patients can swallow properly when asked to
do so, but only constant reminders allow them to keep swallowing. Similarly,
arm swing can be normal if the patient voluntarily and, with effort, wishes 1
have the arms swing on walking. Pronounced bradykinesia prevents a patient with
parkinsonism fir driving an automobile; foot movement from the accelerator to
the brake pedal is too slow.
Bradykinesia
is commonly misinterpreted by patients as weakness. Fatigue, a common complaint
in parkinsonism, particularly in the mild stage of the disease before
pronounced slowness appears, may be related to mild bradykinesia or rigidity.
Subtle signs of bradykinesia can be detected even in the early stage of
parkinsonism if one examines for slowness in shrugging the shoulders, lack of
gesturing, decreased arm swing, and decrementing amplitude of rapid successive
movements. With advancing bradykinesia, slowness and difficulty in the execution
of activities of daily living increase. A meal normally consumed in 20 minutes
may be only half eaten in an hour or more. Swallowing may become impaired with
advancing disease, and choking and aspiration are concerns.
Loss
of postural reflexes leads to falling and eventually to inability to stand unassisted.
Postural reflexes are tested by the pull-test, which is performed by the
examiner, who stands behind the patient, gives a sudden firm pull on the
shoulders, and checks for retropulsion. With advance warning, a normal person
can recover within one step. The examiner should always be prepared to catch
the patient when this test is conducted; otherwise, a person who has lost
postural reflexes could fall. As postural reflexes are impaired, the patient collapses
into the chair on attempting to sit down (sitting en bloc). Walking is
marked by festination, whereby the patient walks faster and faster, trying to
move the feet forward to be under the flexed body's center of gravity and thus
prevent falling.
The freezing phenomenon (motor block) is transient inability to perform active movements. It
most often affects the legs when walking but also can involve eyelid opening
(known as apraxia of lid opening or levator inhibition), speaking
(palilalia), and writing. Freezing occurs suddenly and is transient, lasting
usually no more than several seconds with each occurrence. The feet seem as if
"glued to the ground" and then suddenly become "unstuck,"
allowing the patient to walk again. Freezing typically occurs when the patient
begins to walk ("start-hesitation"), attempts to turn while walking,
approaches a destination, such as a chair in which to sit
(destination-hesitation), and is fearful about inability to deal with perceived
barriers or time-restricted activities, such as entering revolving doors,
elevator doors that may close, and crossing heavily trafficked streets (sudden
transient freezing). Freezing is often overcome by visual clues, such as having
the patient step over objects, and is much less frequent when the patient is
going up steps than when walking on a level ground. The combination of freezing
and loss of postural reflexes is particularly devastating. When the feet
suddenly stop moving forward, the patient falls because the upper part of the
body continues in motion as a result of the inability to recover an upright
posture. Falling is responsible for the high incidence of hip fractures in
parkinsonian patients. Likely related to the freezing phenomenon is the
difficulty for parkinsonian patients to perform two motor acts simultaneously.
1.
Trembling
2.
Rigidity
3.
Mixed
Severity
stages:
I – loss of activity, but that doesn’t influence
on professional activity and working ability
II – moderate loss of professional activity
III – the patients need someone to look after him
Treatment
Treatment of parkinsonism in general is based on the treatment of PD. At
present, treatment is aimed at controlling symptoms because no drug or surgical
approach unequivocally prevents progression of the disease. Treatment is
individualized because each patient a unique set of symptoms, signs, response
to medications, and a host of social, occupational, and emotional needs that
must be considered. The goal is to keep the patient functioning independently
long as possible. Practical guides are the symptoms and degree of functional
impairment and the expected benefits and risks of therapeutic agents.
1. Synthetic
holinolytics : Cyclodolum
( 0.01, 0.005 ), Romparkin, Parkopan ( 0.001, 0.002 )
Stimulators of dophamine secretion
2. Amantadine
medications increase sensation of dophamine receptors to
dophamine, excite dophamine receptors. Midantan ( 0.1 3 times per day ),
Amantadinum.
3. Inhibitors
of MAO ( Jumex ) - 5 mg 1 – 2 times per day.
4. Stimulators
of dophamine receptors – Bromcriptine, Akineton, Norakin (
0.001 – 0.002).
5. Medications
that decrease converse catch of dophamine. Amitriptilinum, Amipraminum,
Melipraminum.
6. Substitutional
therapy . Sinemet 3 – 6
tablets per day. Nacom - 3 – 6
tablets per day.
7. In
order to decrease tremor we use b – adrenoblockers : Anaprilinum 10 mg 3 times
per day, Amitriptilinum 25 mg 3 times per day.
8. In
order to decrease muscle tonus Midocalm, Baclofen are used.
9. Nootrops
10. Physiotherapeutic methods.
Hereditary diseases with involvement of pyramidal system
Spastic
paraplegia of Shtrumpel
This disease
is the result of pyramidal tracts and cerebellar connections degeneration.
The disease is genetically recessive in most
cases but in some families it show dominant inheritance.
Clinical
features. The first signs of the disease are observed at the age
of 10–15. The typical signs of the disease are lower spastic paraplegia with
increased muscle tonus, high stretch reflexes, pathological reflexes. Usually
the lesion of lower extremities is symmetrical. Sometimes motor disorders can
be developed in upper extremities. In some cases pseudobulbar symptoms are
joined.
The typical
signs of the disease:
·
The dominance of spastic tonus over
motor disorders
·
Well preserved abdominal reflexes
·
The absence of pelvic disorders
The typical
clinical picture of spastic paraplegia is often associated with cerebellar
symptoms and symptoms of posterior spinal columns. The progress of the disease
is slow.
Recessive form of spastic paraplegia differs by
early beginning and much more severe course of the disease. In some families
this disease is observed in men only.
Differential
diagnosis
·
LAS
·
Multiple sclerosis
·
Vascular myelopathy
·
Cerebral palsy
Hepatocerebral
dystrophy (HCD)(
This disease
is connected with disorders of ceruloplasminum metabolism. Ceruloplasminum is a
blood protein responsible for Cu transport. It is produced in liver.
Pathologically there is accommodation of Cu in subcortical ganglions
(especially n. Lenticularis), brain cortex, cerebellum, liver, spleen, iris.
The disease
is genetically autosomal – recessive. And it is observed in male and female
with the same frequency.
Clinical
signs of the disease
The first signs of the disease
are observed in early childhood. There are neck stiffness, different
hyperkinesis and psychiatric changes. Sometimes seizures can be observed. There
is also liver enlargement. One of the most specific changes is Kaizer –
Fleishner ring in the iris.
According to the Konovalov classification there are 4
main neurological types of the disease:
1.
Rigid – arythmokinetic
2.
Trembling – rigid
3.
Trembling
4.
Extrapyramidal – cortical
Sometimes the
disease manifests only as liver insufficiency and neurological signs are joined
later.
Diagnosis
·
Family history
·
The typical signs of the disease –
Kaizer – Fleishner ring, lesion of liver, low quantity of ceruloplasminum in
the blood, increased quantity of Cu in urine.
Differential
diagnosis
·
·
MS
·
Chronic stage of epidemic
encephalitis
Torsion
dystonia
The pathology
of the disease includes degenerative changes of subcortical ganglions, subthalamic
nuclei and n. Dentatus of cerebellum as a result of neuromediators production
and metabolism disturbances.
Hyperkinetic
form of the disease has autosomal – dominant type of inheritance. Rigid form of
the disease is characterized by autosomal – recessive type of inheritance.
Clinical
features of the disease The disease begins in early childhood
and it is characterized by permanent progression. The typical signs of the
disease are hyperkinesis that increases with every movement. The hyperkinesis
may have a look of tonic body and extremities muscle straining. Spastic
torticollis is usually one of the earliest symptoms of the disease. There are
no mental disorders in typical cases. There are generalized form of the disease
and local ones, such as spastic torticollis and chirospasm.
Diagnosis Family history and the evaluation of pathological
process dynamics are necessary for the diagnosis putting.
Differential diagnosis
·
Atypical form of Economo encephalitis
Huntington
disease
It is a
progressive hereditary disorder that usually appears in adult life. It is the
result of systemic degeneration of extrapyramidal structures and brain cortex.
It has autosomal – dominant type of inheritance.
Clinical
features of the disease The disease usually appears in adult
life and it is very rare in children. Male and female can suffer from this
disease.
The main clinical symptoms of classic form are:
·
Choreic movements
·
Extrapyramidal rigidity
·
Slowly progressive dementia
Rare forms are:
·
Akinetic – rigid syndrome
·
Extrapyramidal immobility in children
·
Epileptic attacks
·
Myoclonia
Diagnosis
1.
Clinical and genetic analysis
2.
CT and MRI of brain (atrophic changes
of brain hemispheres)
3.
EEG
4.
DNA – analysis
Differential
diagnosis
1.
Chorea
2.
Hepato – cerebral degeneration
Double atetosis
The typical sign of the disease are involuntary movements in face, body and
extremities muscles.
The disease has autosomal – dominant type of inheritance. Both – male and
female suffer from this disease.
Clinical picture of the disease The typical sign of the disease
are slow warm – like movements in fingers and toes. Usually the lesion is
bilateral. But sometimes hemiatetosis can be observed. Spasmus molibilis is
also one of the typical sign of the disease. The signs of the disease are
developed usually just after birth and are preserved during the whole life of
the patient.
Diagnosis
·
Peculiarities of clinical picture.
·
Family anamnesis
Differential diagnosis
·
Hepato-cerebral dystrophy
·
Huntington disease
Generalized
Tourette tic
The disease is characterized by local face, larynx muscles. That causes
gait disorders and complex movements. Sometimes mental disorders can be
observed.
The genetic base of the disease is still being studied.
Clinical features The disease develops in childhood and
progresses gradually.
Diagnosis
·
Anamnesis
·
The results of complex neurological
examination
·
Emotional state evaluation
·
Dynamic changes of clinical changes
Differential diagnosis
·
Torsion dystonia
·
Huntington disease
Essential tremor
of Minor (hereditary trembling)
The most earliest symptom is hands’ trembling, which is preserved while
resting and increases at emotional stress. Sometimes head trembling is
associated. There are no other neurological signs of the disease. Sometimes
there are some of extrapyramidal disorders – rigidity, gait disorders.
The disease is inherited according to the autosomal – dominant type.
Clinical features The disease begins at the age of 50. Men
suffer much more often than women from this disease.
Differential diagnosis
·
Parkinson disease
·
Huntington disease
·
Tireotoxic tremor
Hereditary ataxias
Spinal Fridreich ataxia
The disease is characterized by spinal cord degeneration and degenerative –
dystrophic changes in posterior and lateral columns.
The disease is characterized by autosomal – recessive
type of inheritance.
|
Clinical features of the disease The
disease begins at the age of 10 – 12 and then slowly progresses. The main
clinical signs are sensitive – cerebellar ataxia, nystagmus, muscle hypotonia
and areflexia, gait disorders. At the beginning of the disease there is deep
sensation disorders according to the conductive type on lower extremities. In
the course of the disease coordination disorders, scan speech, body and upper
extremities ataxia appear. The disease is characterized by some bone
abnormalities, cardiomyopathy, mental disorders and the symptoms of lesion of
pyramidal tracts.
Differential diagnosis
·
MS
·
Neurosyphilis
Hereditary
cerebellar ataxia of Pier – Mary
The main
signs of the disease are:
·
The beginning at the age of 30 – 50
·
Cereballar ataxia
·
Dysarthria
·
Hyperreflexia
·
Spastic muscle hypertonia
The inheritance of the disease is autosomal – dominant.
Clinical feature of the disease The disease begins gradually with
gait disorders, disorders of coordination, nystagmus, dysarthria. There are
high reflexes, increased muscle tonus according to spastic type (mainly in
lower extremities), pathologic reflexes. Eye movements disorders are often
observed in such patients. There are mental, memory and emotional disorders.
The course of the disease is progressive.
Differential diagnosis
·
Olivo-ponto-cerebellar degeneration
·
MS
Olivo-ponto-cerebellar
degeneration
It is the group of the diseases that are connected by system lesion of
cerebellar cortex, pons and lower olives. Sometimes the neurons of anterior
horns of the spinal cord and basal ganglia are involved.
The inheritance of the disease is autosomal – dominant.
Clinical features of the disease The disease begins at the age of
15 – 20, sometimes 30 years. Cerebellar symptoms dominate in clinical features.
There are also extrapyramidal and pyramidal symptoms, peripheral
polineuropathy. Sometimes retina is involved in pathological process. Mental
disorders are often observed.
There are several types of olivopontocerebellar degeneration
·
Olivopontocerebellar degeneration of
Mentsel. The disease begins at the age of 20 – 25. There are cerebellar ataxia,
bulbar disoders, extremities paresis, high reflexes and pathological reflexes.
·
Olivopontocerebellar degeneration of
Degerina – Tomas. It develops at the age of 7 – 12. There are cerebellar
disorders, distal hyperesthesia, areflexia, ptosis, convergence disturbances.
·
Olivopontocerebellar degeneration of
Holms. It develops at the age of 20 – 25. It is characterized by cerebellar
ataxia, dementia, ophthalmoplegia.
·
Olivopontocerebellar degeneration with
macular degeneration. It develops at the age of 20 – 25 with progressive
decreasing of visual acuity, central scotoma. In several years ataxia,
intention, choreic hyperkinesis and spastic lower paraparesis are developed.
Differential diagnosis
·
Ataxia of Fridreich.
Step I: Aim:
to determine the clinical diagnosis. Definition
of the clinical form of genetically - degenerative disease with a lesion of
pyramidal, extrapyramidal system and cerebellum. It is necessary:
1.
To examine patient (genetic anamnesis, somatic status);
2.
To conduct differential
diagnostic according to algorithm of the differential diagnosis of genetically
- degenerative diseases with a lesion propulsion systems;
3. To formulate
the clinical diagnosis.
Step II: Aim: To prescribe
treatment. It is necessary to use the principle of pathogenetic correction of
disorders at:
à) Parkinson’s disease - cholynolitics, dofaminergical drugs, relaxants,
tranquilizers and antihistaminics;
á) Hepatolenticular degeneration (Wilson’s disease) -
Cuprenilum (Ä-penicylaminum), Unithiolum, diet, poor on brass, by liver therapy
â) Huntington’s chorea - Reserpinum (dopegitum),
Haloperidolum, small tranquilizers, Triphtazinum.
Step III: Aim: Medical
genetic consultation. It is necessary, taking into account a mode of
inheritance and penetrance of a gene, to evaluate probability of birth of the
ill child.
Diseases with involvement of neuro – muscular junction:
a.
Progressive muscular dystrophy (Myopathies)
Myopathies are
conditions in which the symptoms are due to dysfunction of muscle with
progressive weakness, impaired relaxation (myotonia), cramps or contracture (in
McArdle disease), or myoglobinuria. Dystrophies are myopathies with four
special characteristics:
1.
They are inherited.
2.
All symptoms are due to weakness.
3.
The weakness is progressive.
4.
There are no abnormalities in muscle
other than degeneration and regeneration, or the reaction to these changes in muscle
fibers (infiltration by fat and connective tissue), and there is no storage of
abnormal metabolic products.
Etiology.
These inherited diseases are separated from each other on the basis of clinical
and genetic criteria, but the inherited biochemical abnormality has not been
identified in any of them. Therefore, the pathogenesis of these disorders is
not known.
Pathology.
In the majority of the cases, the significant pathological findings are
confined to the muscles. There may be a few degenerative changes in the ventral
horn cells or a slight reduction in their number, but as a rule the peripheral
and central nervous systems are normal. In the early stages of the disease, the
muscle fibers are rounded and enlarged to more than twice their normal size.
With
progress of the disease, there is a longitudinal splitting of some of these
large fibers with resulting admixture of fibers of various sizes. This
splitting of the fibers is accompanied by hyaline degeneration of the
myoplasma, evidence of regeneration, an increase in the number of sarcolemmal
nuclei and replacement of the muscle substance by fat and connective tissue.
Classification.
They divide the cases into sach groups:
a.
Dushen pseudo – hypertrophic muscle
dystrophy
b. Late
Bekker pseudo – hypertrophic muscle dystrophy
c.
Shoulder – scapula – facial form of
Landouzy – Degerina
d. Erba
dystrophy
|
Clinical features of all myopathies.
Symptoms. The symptoms are essentially those due to the muscular
weakness. In the majority of cases the proximal musculature is more severely
affected than that of the distal parts of the extremities. The child is clumsy
in walking and has difficulty in climbing up and down stairs. Toe walking is a
common early symptom. The weakness of the shoulder proximal muscles makes it
difficult for the child to raise the arms over the head or lift heavy objects.
The weakness of the pelvic proximal muscles gives rise to the characteristic
waddling gait and attempts to turn result in much commotion but little
progression because the knees cannot be raised properly. The boy may fall
frequently and then has trouble rising without assistance.
|
Signs. Cardiac failure as the result of involvement of
the heart muscles has been reported in a few cases. In the majority of cases,
the dystrophy is limited to the muscles of the trunk and extremities. The gait
and posture are characteristic. There is an advanced degree of lumbar lordosis
as a result of weakness of the trunk muscles. There is a stoppage, waddling
gait. Movements of the arm may be accompanied by winging of the scapula.
Weakness of the shoulder proximal muscles causes the child to slip through the
hands when attempts are made to lift
him by placing the hands in the axillar.
Another
characteristic and diagnostic feature of the disease is the manner in which the
patient rises from the supine to the erect position (Gower's sign). The patient
first turns over onto the abdomen and raises the trunk to the crawling
position. He then places the feet firmly on the floor with the aid of his arms
and gradually elevates the upper part of the body by "climbing up his own
trunk" with the arms. With progression of the weakness, the patient is
able to rise from the floor only by pulling himself up with his hands on a
chair or some other fixed object.
On palpation
the hypertrophic muscles feel firm and rubbery. The wasted muscles are often
difficult to feel on account of the overlying fat. Pseudohypertrophy may
precede the onset of wasting, or it may affect muscles which have never
hypertrophied. The involvement of the musculature is usually symmetrical. There
are some variations in the degree of weakness on the two sides but involvement
limited entirely to one side does not occur. Abnormal movements and fibrillary
twitchings of the muscles are not present.
The sensory examination is normal and there are no
sphincter disturbances. The deep reflexes may be lost early in the course of
the disease or they may persist in wasted muscle. The knee jerks usually
disappear before the ankle jerks. Cutaneous reflexes are preserved and the
plantar responses are usually flexor.
|
Duchenne Muscular Dystrophy
Definition
Duchenne muscular dystrophy is the most common form of
muscular dystrophy and is seen almost exclusively in young males, with a prevalence
of
Dushen pseudo – hypertrophic muscle dystrophy occurs
entirely in males and the onset is usually in the first four years of life.
The transmission is as sex-linked
recessive trait and the mutation rate is high. The rate of progression is
relatively rapid, with death in the second or third decade. A milder form of
X-linked recessive dystrophy was described by Becker. The clinical features are
similar to those of Duchenne dystrophy but the onset is later in childhood or
adolescence and the rate of progression is much slower, so that survival into
adult years is common.
In Duchenne dystrophy the child is
clumsy in walking and has difficulty in climbing up and down stairs. Toe
walking is a common early symptom. There are no cerebral symptoms, but mental
retardation seems to be unduly common in the Duchenne type. In Duchenne
dystrophy, pseudohypertrophy is present
in some muscles of the extremities and in others it is entirely absent. More
often, there is wasting of some muscle groups and pseudohypertrophy in others.
The gastrocnemius, deltoid and triceps are most frequently affected by the
pseudohypertrophy.
Table 20-1
Distinguishing Characteristics of Myopathic and Neurogenic
Disorders
Myopathic |
Neurogenic |
Signs and
symptoms Proximal weakness and wasting |
Distal weakness and wasting ± Sensory signs and
symptoms ± Fasciculations, increased tone, extenser plantar responses |
Serum muscle enzymes Increased |
|
Nerve condition velocities |
|
|
Slowed |
Electromyography |
|
Low-amplitude polyphasic motor unit potentials of
brief duration |
Increased insertion activity Fibrillations, fasciculations
Positive sharp waves |
Muscle biopsy Variation in fiber diameter Internal nuclei
Degeneration of fibers Increased endomysial connective tissue |
Angular fibers, target fibers Pyknotic clumping Type grouping Type I
fibers: small Type II fibers: hypertrophied |
Etiology and Pathology
Duchenne muscular dystrophy is characterized by an
absence of the protein dystrophin in the
muscle fiber. Dystrophin is normally
located in the muscle surface membrane and is part of the membrane cytoskeleton,
acting as a stabilizing factor in membrane function. The absence of dystrophin affects the function of
dystrophin-associated proteins, which provide a link between dystrophin and the extracellular matrix
protein, laminin, the major component of the extracellular matrix. Dystrophin-associated protein
dysfunction leads to an increased susceptibility to muscle fiber
degradation.
Muscle biopsy shows abnormal variation in muscle fiber
size. Other changes include central displacement of nuclei into the muscle
fiber, splitting of fibers, fragmentation of the cytoplasm, focal vacuolization, hyalinization and shrinking of
the sar-colemmal sheath. There are clusters of necrotic
fibers, evidence of regeneration, extensive proliferation of perimysial and endomysial connective tissue,
and replacement of muscle fibers by fat.
Clinical Features
Affected children appear normal at birth and may be
extremely placid. There is normal achievement of early milestones, but there is
delay in standing and walking. The child then develops a clumsy, waddling gait
and pseudohypertrophy of the calf
muscles, associated with difficulty climbing stairs and rising from a chair.
Older children have a pronounced lumbar lordosis
caused by weakness of the pelvic musculature and the erector spinae.
This results in forward tilting of the pelvis, protrusion of the abdomen, and
compensatory backward arching of the upper thoracic spine and shoulders. The
affected child has difficulty rising to a standing position. He must first roll
to a prone position, pull himself to his hands and knees, push with his arms
until only his hands and feet are on the floor, and finally, "walk"
up his lower extremities until he can extend his trunk and stand. This method of
assuming a standing position in the presence of severe proximal weakness has
been termed Gower's sign. Eventually the child can no longer ambulate and
becomes confined to a wheelchair by the age of 10. Multiple contractures, deformities and severe scoliosis, and distal weakness and wasting are
prominent features in the latter stages of the disease. Typically, the patient
is bedridden in the teens and dies in the late teens or early twenties. The
absence of dystrophin in cardiac muscle
results in a primary progressive cardiac dystrophic
process.5 There is a steady decline in cardiac reserve, but
heart failure is rare, probably because the patient leads a sedentary
life-style. Many develop gastrointestinal hypomotility because dystrophin is absent in smooth muscle. Acute
gastric dilatation or fatal intestinal obstruction may occur in advanced
cases.
Absence of dystrophin in
the brain results in mild impairment of intellectual-cognitive functioning in a
subset of patients with Duchenne muscular dystrophy. Lack of dystrophin increases susceptibility to neuronal damage, suggesting that mental
impairment may be the result of ischemic insults
during fetal life or parturition. Because this is an X-linked, recessive
disease, males carrying the abnormal dystrophic mutation
express Duchenne muscular dystrophy and females are usually nonexpressing
carriers. Occasionally females carrying one copy of the abnormal mutation
exhibit a milder form of Duchenne muscular dystrophy, and muscle biopsy
demonstrates a mosaicism of dystrophin expression. The disease may also
result from inactivation of the normal X chromosome in some female cases, or
an X chromosome translocation, disrupting
the dystrophin gene, with selective
inactivation of the nontranslocated X chromosome.
Diagnostic
Procedures
1. Muscle
enzymes. Serum creatine kinase (CK) is elevated and may be abnormal before the onset
of clinical signs and symptoms. There are increased serum levels or other
muscle enzymes, including aspartate
transaminase (AST), alanine
transaminase (ALT), lactic dehydrogenase (LDH),
and aldolase. The elevation is high in
early cases and declines with progression of the disease. Creatinuria and
myoglobulinuria may also be present.
2. The
electrocardiogram is abnormal at an early age. The initial tachycardia is
followed by increased R-wave voltage and eventually development of right
bundle branch block and deep Q waves.
3. The
electromyogram is abnormal, with myopathic features.
Motor unit potentials are reduced in duration
and amplitude, and
there is increased polyphasic wave activity and early
recruitment.
4. Between
2.5 and 10 percent of female carriers of the mutated dystrophin gene have clinical evidence of muscle weakness.
5. In
asymptomatic carriers, mutation detection can be performed on lymphocytic genomic DNA obtained from a single
blood specimen, using several methods, including Southern blot analysis, field
inversion gel electrophoresis, or polymerase chain reaction exon amplification
assays. Muscle biopsy can be omitted when mutation detection is positive.
6. Muscle
biopsy was the definitive method of diagnosis before the development of genetic
diagnostic techniques. Standard
light and electron
microscopy can be augmented by immunohistochem-istry and the use of
antidystrophin antisera.
Differential
Diagnosis
1. Other forms
of dystrophy.
2. Neurogenic muscular atrophy.
3. Polymyositis and dermatomyositis, which
are characterized by inflammatory changes on muscle biopsy.
4. Polyneuropathy differentiated by its more rapid
onset slow nerve conduction velocities and muscle and nerve biopsy.
5. Benign
congenital myopathies (see below).
Treatment
1. There is
no specific treatment
for Duchenne muscular dystrophy.
2. A physical
therapy program will help to delay the development of joint contractures. Obesity should be avoided.
Splinting, bracing, and surgical procedures to prevent or treat deformities can
prolong the ability to walk.11
3. Joint contractures can be relieved by tendon release
procedures.
4. Severe scoliosis can be stabilized or reversed by
orthopedic surgical techniques.
5. Mild upper
respiratory infections are potentially lethal in advanced disease and should
be treated with appropriate antibiotics. A decline in respiratory function
with difficulty in clearing secretions can be relieved by intermittent
continuous positive airway pressure.12 Nocturnal hypoventilation based on hypoxia hypercapnia measured by blood gas determination
requires intermittent noninvasive ventilator
support using a nasal mask. Permanent ventilator support usually occurs when
forced vital capacity declines below
6. A
lessening of the emotional impact of the disease on the patient and family, and
the development of optimal living conditions, can be achieved by a combined
effort of the neurologist, physiatrist, psychologist, and social worker.
7. Corticosteroids
decrease the rate of muscle loss. Prednisone
0.75/kg daily can be given for as long as 6 months.
8. Newer techniques of gene therapy using myoblast transplantation or gene transfer by
reduplication defective retroviruses,
adenoviruses, or herpesviruses are
currently under investigation. Results have been equivocal.
9. Genetic counseling should be provided. It is
important to advise the family regarding the likelihood of involvement in a
subsequent pregnancy. Carriers of Duchenne dystrophy may have elevated serum
CK levels. Carrier detection or prenatal mutation diagnosis is readily
established by DNA diagnostic testing.
Prognosis
Duchenne muscular dystrophy is a steadily progressive,
incapacitating disease until death in the late teens or early twenties. A
better understanding of pulmonary problems and improved treatment of
respiratory infections has significantly increased the life span in Duchenne
muscular dystrophy and other muscle diseases affecting muscle function.
Shoulder – scapula – facial
form of Landouzy – Degerina (Facioscapulohumeral
Muscular Dystrophy (FSH)) type
occurs in both sexes. The onset of symptoms may be at any time from early
childhood to late adult life. There are many mildly affected abortive cases.
Transmission is by an autosomal
dominant gene. This
is an autosomal dominant form of muscular
dystrophy with a frequency of
Pathology The
muscle changes are typically those of dystrophy, but inflammatory changes are a
common feature.
Clinical Features
Symptoms and signs of FSH occur in adolescence, with
95 percent penetrance by age 20. There is
initial weakness and atrophy of the facial and shoulder girdle muscles with
later progression to the abdominal and pelvic girdle muscles, and foot
extensors. Clinical expression shows marked variation, ranging from almost
asymptomatic to quadriparesis. Hearing loss occurs in 50 percent of cases and
can be severe. Retinal vascu-lopathy consisting of telangiectasias and microaneurysms has
been recognized by fluorescein angiography.
Diagnostic Procedures
1. Serum CK
levels are elevated in the active phase of the disease.
2. Electromyographic findings are compatible with a myopathy but may be normal.
3. Muscle
biopsy will establish the diagnosis.
Treatment
There is no specific treatment for this disease.
Supportive measures are indicated as the disease progresses, with emphasis on
control of upper respiratory infections in advanced cases.
When the facial muscles are affected in
the Landouzy-Dejerine type, the expression is mask-like, the lips are
prominent, the eyes are imperfectly closed in sleeping and facial movements are
absent in laughing or crying as well as on voluntary efforts in whistling and
the like. Involvement of the masticator, palatal and pharyngeal muscles may
occur, but is rare.
Limb-Girdle Muscular Dystrophy (Erba dystrophy) occurs in
either sex and the onset of symptoms is usually in the first three decades of
life. There are various modes of inheritance, but it is commonly transmitted as
an autosomal recessive trait.
Definition
This is a heterogenous group
of dystrophic muscle diseases, usually
sporadic but occasionally inherited as an autosomal
recessive trait that maps to chromosome 2pl3-16 or inherited as an autosomal dominant trait linked to chromosome
15q.l5.1-q21.1 with preferential involvement of truncal
and proximal limb girdle muscles.
Pathology
There is variation in muscle fiber size, with the
presence of small, angular, and hypertro-phied fibers showing internally placed
nuclei. Fiber necrosis and regeneration are present, with replacement of
fibers by fibrous and adipose tissue in advanced cases. Motheaten and
tabulated fibers occur in most cases. The sarcolemma shows positive staining
with antidystrophin antibodies.
Clinical Features
The earliest symptoms consist of weakness of the
pelvic girdle or proximal lower limb muscles, which presents at any age from
childhood to adulthood, with a mean age of onset of 21 years. The autosomal dominant form of the disease presents
in adults and exhibits a slower progression of weakness. The initial symptoms
are followed by involvement of upper limb-girdle muscles, then by progressive
weakness of truncal or more distal limb
muscles, with loss of walking ability 10 to 20 years after onset. Cardiomyopathy is rare and usually
asymptomatic, but cardiac failure has been reported.
Examinations.
Routine examinations of the blood, urine and cerebrospinal fluid are normal.
The excretion of creatinine is decreased in proportion to the amount of loss of
muscle substance, in a similar manner to that occurring in other diseases
accompanied by muscular wasting. There is an increase in the amount of creatine
excreted in the urine, and there is impairment of the ability of the body to
store ingested creatine. The significance of the creatinuria is not known.
There is no consistent or specific pattern of amino acid excretion.
Increased serum levels of aldolase,
lactic dehydrogenase, phosphohexoisomerase, transaminase and creatine
phosphokinase have been reported. Serum enzyme levels are most consistently elevated in the early stages of the Duchenne
variety of muscular dystrophy. Detection of the disease in the preclinical
stage of this form of the dystrophy can be made by determination of the serum
enzymes, and detection of the carrier state in unaffected females is manifested
by an increase in the serum of creatine phosphokinase. When the serum CPK is
definitely increased in a potential carrier of the Duchenne gene, it is likely
that the woman is a carrier, but borderline or normal values do not exclude
this possibility because even in known carriers (for instance, a woman with
both an affected brother and an affected son), CPK is abnormal in only about
80% of the cases. A mild degree of degenerative change in the muscles has also
been found in some asymptomatic carriers.
Among the biochemical abnormalities
that suggest an abnormality of surface membranes in Duchenne dystrophy are
impaired responses of adenyl cyclase to epinephrine and fluoride in muscle, and
several abnormalities of erythrocyte membranes, including sodium-potassium
ATPase, membrane phosphorylation, osmotic fragility, and some morphological
characteristics.
Ultrastructural study of muscle has
revealed gaps in the plasma membrane of muscle. In contrast to normal surfaces,
these gaps seem to be permeable to large molecules such as the protein,
horseradish perioxidase, or a dye, procion yellow. Additionally,
freeze-fracture studies showed decreased numbers of membrane particles. These
abnormalities bear upon theories of pathogenesis, but have not yet had an
impact on diagnosis of individual cases.
The
electromyogram is of considerable value in diagnosis. The pattern of voluntary
effort recorded by means of concentric needle electrodes is characterized by
disintegration of motor unit potentials, many of which become polyphasic and of
short duration.
Course.
There
is considerable variation in the course of these diseases. The prognosis is
most favorable when the onset of symptoms occurs after the second decade of
life. As a rule, there is a gradual increase in the weakness of the muscles
which are first involved and a slow progress of the wasting to unaffected
muscles. The small muscles of the hands and feet are usually last to be
affected.
Contractures
may appear and atrophic changes in the bones have been reported in a few cases.
Formes frustes with preservation of general good health to old age are not rare
in facioscapulohumeral dystrophy, and it is not unusual to find patients who
have suffered with the disease for four and five decades but are still able to
walk. In the Duchenne form it is common for the disease to progress within a
period of five to fifteen years to the stage where the patient is confined to a
bed or a wheel-chair. Death may occur from intercurrent infection or from
involvement of the respiratory musculature.
Diagnosis.
The diagnosis of Duchenne dystrophy can
usually be made without difficulty by the onset of muscular weakness in childhood,
the presence of pseudohypertrophy of the muscles, the characteristic
distribution of the weakness, the family history and the increased serum
enzyme activity. When the onset is relatively late in life, as in limb-girdle
or facioscapulohumeral forms, the diagnosis is made by the distribution of the
weakness, the loss of deep reflexes and the absence of evidence of involvement
of the spinal cord or peripheral nerves. Determination of the serum enzymes,
electromyography and biopsy of the muscles are of value in establishing the
diagnosis.
Differential diagnosis.
Progressive muscular dystrophy must be distinguished from the diseases of
infancy and childhood which are accompanied by muscular wasting. Limb-girdle
and facioscapulohumeral dystrophy must be distinguished from diseases of adult
life which are accompanied by muscular wasting:
1.
myotonic muscular dystrophy
2.
proximal spinal muscular atrophy
3.
peroneal muscular atroph
4.
amyotrophic lateral sclerosis
5.
atypical forms of polyneuritis
6.
syringomyelia and myositis.
The differential diagnosis between
named diseases and progressive muscular dystrophy can be made by the lack of
family history, much more rapid course, inflammatory response in muscle.
Genetic analysis has shown that there is an X-linked dystrophy, the Becker
type, less severe than the Duchenne type; recognition of Becker cases is
facilitated by the recognition of other affected individuals in the same family
who are still walking after age twenty, but in sporadic cases, the separation
of Becker cases from either Duchenne or limb-girdle cases may be difficult.
In
polyneuritis, particularly the Guillain-Barre form, the muscular weakness may
occasionally be greatest in the girdle muscles. The acute onset of the
symptoms, the increased protein content in the cerebrospinal fluid and the
subsequent regression of symptoms should serve to establish the diagnosis.
Pseudohypertrophy
of the muscles may occasionally be seen in syringomyelia but the other features
of the disease should leave no doubt in regard in the diagnosis.
Treatment.
There is no treatment which has proven to be effective in arresting the course
of the disease. Stretching of contractures, bracing and tendon-lengthening
operations are advocated with varying degrees of enthusiasm in different
centers. When known carriers of the Duchenne gene become pregnant, fetal sex
determination permits interruption of pregnancy for boys, but there is no way
of identifying
Becker Muscular Dystrophy
This condition is a milder expression of a disease
caused by mutation of the dystrophin gene
at Xp21. Patients have an abnormal but functioning dystrophin, reduced in size. There is a wide range of presenting
symptoms, varying in severity from a slightly milder form of disease resembling
Duchenne muscular dystrophy to asymptomatic elevation of CK.
The affected individual appears to be normal at birth
and shows normal developmental milestones; the mean age of onset is 11 years.
The initial symptoms often consist of muscle cramps on exercise. Progression
is slower than Duchenne muscular dystrophy and patients may walk with bracing
until the late twenties or early thirties. Asymptomatic cardiac involvement is
not unusual. Symptomatic cardiac involvement is unusual. Hypertrophic cardiomyopathy is rare. Because
genetic analysis cannot determine the correct diagnosis in 35 percent of cases,
endomyocardial biopsy specimens can be
stained by immunostaining techniques in patients with cardiomyopathy suspected to be the result of Becker muscular
dystrophy.
Diagnostic Procedures
Diagnostic procedures have been discussed under
Duchenne muscular dystrophy.
Treatment
The most severe cases of Becker muscular dystrophy
should be treated as Duchenne mus cular dystrophy. Physical therapy measures
may maintain ambulation in some cases, up
to the age of 30 or more, and many patients survive into their forties.
Occasional patients are reported with survival into the seventh decade.25
Congenital Muscular Dystrophies
Definition This
heterogeneous group of muscular dystrophies is inherited as an autosomal recessive trait characterized by dystrophic changes on muscle biopsy.
Etiology and Pathology
The congenital muscular dystrophies are the result of
deficient components in the dystrophin-glycoprotein
complex. This complex has a structural role in muscle and probably anchors
muscle cells to the extracellular matrix. This attachment stabilizes the
sarcolemmal membrane and protects it from stressors
that develop during muscle contraction. Disruption of this linkage leads
to sarcolemmal instability and muscle cell necrosis. Dystrophin, which is localized to the sarcolemma, is completely
absent in Duchenne muscular dystrophy. Absence of other proteins in the dystrophin-glycoprotein complex have been
identified in other forms of congenital muscular dystrophy. A merosin-negative
condition and an adhalin deficiency have been described.
Clinical Features
There is profound hypotonia
and muscle weakness at birth, with arthrogryposis
developing in the first year of life. The clinical course is nonprogressive or slowly progressive.
Intellectual development is usually normal, and the condition may stabilize in
adolescence. A variant designated as severe childhood autosomal recessive muscular dystrophy, with adhalin deficiency
(Fukayama type), in which there are cerebral abnormalities and mental retardation
and epilepsy, has been recognized.
Scapuloperoneal Muscular Dystrophy and the Scapuloperoneal Syndrome
Definition This
is a slowly progressive syndrome of weakness involving the scapuloperoneal
musculature.
Etiology and Pathology
There are several distinct forms of the disease, a myopathic or neurogenic
form inherited as an autosomal dominant
trait, and a sex-linked recessive myopathic form
in which the affected muscles show dystrophic changes.
Clinical Features
Weakness begins in the peroneal
muscles with lesser involvement of the scapula, shoulder, and upper arm
musculature, and occasional mild involvement of the facial and laryngeal muscles. The dystrophic form can be accompanied by joint contractures, cardiac conduction abnormalities and cardiomyopathy. The rate of progression varies,
and disability can be severe two decades from the time of onset.
The neurogenic condition
can occur with or without sensory change, and both axonal and de-myelinating variants have been described. The mild
facial weakness can lead to an inaccurate diagnosis of facioscapulohumeral dystrophy.
Diagostic Procedures
1. Serum CK
levels are elevated.
2. Electromyography is consistent with an active,
chronic myopathy.
3. Dystrophic changes are present in the muscle
biopsy.
4. A normal dystrophin staining pattern on muscle biopsy
excludes Duchenne and Becker-type muscular dystrophy.
Treatment Prevention of contractures and
bracing to maintain mobility is required in more advanced cases.
Oculopharyngeal Muscular Dystrophy
Definition
This rare muscular dystrophy is inherited as an autosomal dominant trait characterized by late
onset of chronically progressive ptosis and
dysphagia.
Clinical Features
Most patients are of French Canadian descent, but the condition has been
described in other ethnic groups.
Symptoms consist of chronically progressive ptosis and dysphagia
beginning in the mid forties or fifties. The ptosis is a result of progressive weakness of the levator palpebrae, and there is preservation of
orbicularis oculi function and
Diagnostic Procedures
Electromyography and muscle biopsy are compatible with a muscular dystrophy, and the
muscle biopsy shows granular degeneration of muscle fibers, progressive loss
of fibers, and replacement by fibrous tissue. Manometric studies are useful to
assess swallowing abnormalities.
Treatment
Surgical treatment of ptosis
is successful in most patients. Dysphagia
may require myotomy or dilatation
of the oropharyngeal sphincter.
Distal Muscular Dystrophy
There are at least four distinct forms of inherited
distal myopathy. Each is characterized
by initial weakness in a distal muscle group with progressive involvement of
more proximal muscles.
1. Late
onset, type 1 (Welander)—autosomal dominant;
onset age 40 to 60 years; begins in the small muscles of the hands and spreads
proximally. There is late involvement of the anterior tibial and calf muscles.
2. Late adult
type 2 (Markesbery)—an autosomal dominant,
late onset form beginning with tibialis anterior
weakness with slow progression and spread to the calf muscles, and later
involvement of the upper limbs.
3. Early
adult type 1 (Nonaka)—an autosomal recessive
condition with early adult onset, beginning in the tibialis anterior with later spread to the calf muscles, then upper
limbs.
4. Early
adult type 2 (Miyoshi)—an autosomal recessive
type beginning at age 15 to 30 years with involvement of the gastrocnemius and sparing the anterior
compartment muscles. There is later involvement of thighs and buttocks and
mild involvement of the upper limbs.
Amyotrophy as a result of peripheral
neuron lesion
A. Spinal
amyotrophy of Werding – Hoffman
B. Proximal
amyotrophy of Kukelberg – Welander
C. Sharko
– Mary – Tooth disease
Spinomuscular Atrophies
Definition
The spinomuscular atrophies are a group of diseases of
unknown etiology that result from degeneration of motor neurons in the spinal
cord and occasionally in the brainstem.
Etiology and Pathology
The etiology is unknown. In most cases, the condition
is inherited as an autosomal recessive
trait, and rarely as an autosomal dominant
condition, with linkage to chromosome 5. Major deletions of 5ql 1.2-13.3 have
been described in severe infantile spinal muscular atrophy, unlike patients
with mild disease who have smaller deletions. Genes for neuronal apoptosis inhibitory protein and the spinal muscular
atrophy motor determining gene also map to 5ql3 and one or both of these genes
may be implicated in spinomuscular atrophy.
The primary pathological process appears to be
degeneration and atrophy of the anterior horn cells. However, chromatolytic
changes with enhanced mitochondrial and oxidative activity in surviving neurons suggest
that the primary change may be distal in the axons.
The muscle shows evidence of denervation atrophy with atrophic motor
units surrounded by normal-appearing muscle fibers. However, histochemical
studies show that the surrounding fibers are all of one histochemical fiber
type, because of reinnervation of denervated fibers by sprouting collaterals
from axons of surviving anterior horn cells.
Other helpful findings include the presence of angular fibers and target or
targetoid fibers.
Clinical Features
There are four clinical forms based on age and onset
of signs and symptoms.
Infantile Form
(Werdnig-Hoffman)
The condition is present at birth and the mother
frequently reports diminution of the child's movements in utero in the
later weeks of pregnancy. The infant is weak at birth and shows progressive
muscular weakness and hypotonia (floppy
infant). This produces a characteristic "frog" position when the baby
is prone. The arm is abducted at the shoulder and flexed at the elbow, and the
lower limbs are abducted and externally rotated at the hips and flexed at the
knees. There is progressive weakness of respiratory muscles, paradoxical
respirations leading to respiratory insufficiency, pneumonia, and death within
12 to 18 months.
Infantile
muscular atrophy (Werding
– Hoffman) is recognized by its onset in infancy, the presence
of fibrillations and the rapidly fatal course.
Late Infantile Forms
These children have normal movements at birth but
develop progressive muscle weakness and hypotonia
within 2 months. The lower limbs are weaker than the upper limbs and the
child is never able to stand or crawl. Fascicula-tions of the tongue occur in about 50 percent of cases. Death
usually occurs within 2 years, but some children survive for several years.
Childhood Form
Children with this form of spinomuscular atrophy develop
normally up to or beyond the first birthday and are able to stand and crawl.
Many are able to walk for a short period of time, but progressive weakness,
wasting, hypotonia, and hy-poreflexia,
with proximal or distal preponderance, impose increasing restriction of
activities. Fasciculations are unusual in limb muscles but may be present in
the tongue. Focal or even diffuse muscle hypertrophy can occur due to
hypertrophy of surviving motor units. There may be a fine asynchronous tremor
of the outstretched hands due to the firing of large motor units; this results
from reinnervation of denervated muscles by surviving nerve fibers. Voluntary
contraction fas-ciculation, which disappear on relaxation, may be present.
Palpation of the contracting muscle may yield a vibration-like sensation.
Auscultation may reveal a low-pitched rumbling. Late changes include joint contractures and scoliosis. Severe scoliosis may
lead to spinal cord compression and result in hyper-reflexia and extensor
plantar responses. The combination of scoliosis
and respiratory muscle involvement can produce severe respiratory
insufficiency.
Adolescent Form (Familial
Spinal Muscular Atrophy—Kugelberg-Welander Syndrome)
This is a more benign form of spinomuscular atrophy
that is inherited as an autosomal dominant
or autosomal recessive trait and begins
at about 2 years of age. Wasting and weakness may be confined to the proximal
limb-girdle musculature. There may be fas-ciculations in the limb-girdle
muscles and the tongue, and some hypertrophy of muscles can occur. Both
hy-poreflexia and hyperreflexia are reported. The disease is often confused
with the limb-girdle type of muscular dystrophy but can be distinguished by
muscle biopsy. This is the most benign form of generalized spinomuscular
atrophy. The patient survives into adult life, at which time there is slowing
or apparent arrest of the muscle weakness.
Focal forms of the disease present with:
1. Scapulohumeral distribution. This form is
usually benign but may present as a rapidly progressive disease in adults, with
death from respiratory failure within 3 years.
2.
Scapuloperoneal distribution. This form also occurs in adolescents and
adults. The atrophy involves muscles of the scapular and periscapular region
and the anterior compartment of the leg.
3. Ocular and
facial muscle involvement. This form occurs in children and adults and
constitutes one of the conditions in the syndrome of
"oculomy-opathy."
4. Bulbar involvement (Fazio-Londe disease). This
rapidly progressive form of muscular atrophy involves bulbomotor neurons and
begins in early childhood. The atrophy is most marked in the bulbar musculature with weakness and wasting
of the extraocular facial and pharyngeal muscles. Death occurs from
respiratory insufficiency and pneumonia.
Diagnostic Procedures
1. It is
possible to produce fasciculations in suspected cases by intramuscular
injection of 1 mg Prostigmin.
2. The EMG may
show the presence of fasciculations and fibrillations.
3. Muscle
biopsy with histochemistry is abnormal.
The findings are
outlined under etiology
and pathology.
Treatment
The infantile form of spinomuscular
atrophy runs a rapid course, with death from respiratory failure 12 to 18
months after birth. Patients with the more chronic forms of the disease should
receive:
1. Treatment
directed toward maintaining ambulation as
long as possible. This includes physical therapy, orthopedic consultation,
bracing, and surgical procedures.
2. Prompt
treatment of all respiratory tract infections that may lead to pneumonia,
pulmonary insufficiency, and death.
3. The
intelligence is not affected and patients benefit from an appropriate
education.
Prognosis The
life span is reduced in all forms of generalized spinomuscular atrophy, but a
normal life span is possible in some patients, with focal forms of the
disease.
Juvenile
muscular atrophy (Kugelberg-Welander)
may be suspected if fasciculations are seen in a patient who otherwise seems to
have limb-girdle or facioscapulohumeral dystrophy because of proximal limb
weakness. In some patients, however, fasciculations are not clinically visible
and motor neuron disease is identified only by electromyography and muscle
biopsy. This distinction is of some importance because, in general but not
always, the prognosis of juvenile neurogenic disease is less serious.
Hereditary
neuropathies
Peroneal
muscular atrophy. Peroneal muscular atrophy (Charcot-Marie-Tooth
syndrome) includes several genetic disorders of the peripheral nervous system that
most severely affect the peroneal and other distal muscles of the legs.
Inheritance
is usually autosomal dominant and, less frequently, autosomal recessive.
Foot deformities are frequent and may
be the only apparent feature of the disease in mildly affected family members.
Impairment of sensation in a stocking-and-glove distribution is usually
present, though sensation is preserved in some families. Achilles reflexes are
absent and other tendon reflexes may be diminished.
Clinical features. The pathologic changes are of three types. There are:
1. Demyelination of the peripheral
nerve with axonal loss and some hypertrophy of the Schwann cells, producing
hypertrophic neuropathic changes. In Type I Charcot-Marie-Tooth syndrome, symptoms
begin in the first or second decade of life with foot-drop and a stoppage gait.
Distal muscle atrophy produces a "stork leg" deformity; intrinsic
hand muscle atrophy develops later. Distal tendon reflexes are diminished or
absent and a stocking-and-glove sensory defect is present. Scoliosis and high
pedal arches or club feet are common. Peripheral nerves are often palpably
enlarged. Tremor is prominent in some patients; the clinical constellation of
Charcot-Marie-Tooth syndrome with tremor is termed the Roussy-Levy syndrome.
2. Neuronal loss of anterior horn
cells and posterior nerve root ganglion neurons in the lumbar and sacral
segments (hereditary motor and sensory neuropathy, Type II). The first symptoms
of peroneal muscular atrophy often appear in adult life, but foot deformities
may be evident much earlier. The progression is slow with muscle weakness and
wasting confined to the feet and sometimes involving the leg muscles. The
involvement may be asymmetric. Atrophy and weakness of distal muscles,
stocking-and-glove sensory impairment is minimal or absent, and depression of
tendon reflexes in the lower limbs but normal in the arms. Deficits are usually
less severe and nerves are not palpably enlarged.
3. Anterior horn cell involvement
with secondary axonal loss and demyelination of motor fibers.
Examinations.
1. Lumbar
puncture. CSF protein content is frequently elevated in
Type I Charcot-Marie-Tooth syndrome, but is normal in Type II. The CSF is
otherwise normal, as are blood and urine.
2. Nerve conduction velocities. Motor
and sensory nerve velocities are very slow in the peripheral nerve
demyelinating type but are normal or only slightly delayed in the other two
types.
3. Nerve biopsy. Nerve biopsy is
normal and should differentiate the three types of the disease.
Differential diagnosis. Peroneal muscular atrophy is considered when there
is atrophy of the peroneal muscles, foot deformity, and a positive family
history. Even if family history is reported to be negative, relatives should be
examined because some affected individuals are asymptomatic, or deny mild
symptoms.
1.
Friedreich
ataxia should be considered if distal neuropathy and a
positive family history are accompanied by nystagmus, dysarthria, ataxia, or
Babinski signs.
2.
Familial
amyloidosis may resemble peroneal muscular atrophy, and can
be recognized by sural nerve biopsy.
3.
Dejerine-Sottas
syndrome also resembles peroneal muscular atrophy, but onset is earlier, nerve
hypertrophy is more prominent, the elevation in CSF protein content is greater,
and nerve conduction rates are slower than in Type I Charcot-Marie-Tooth
syndrome.
4.
The distal motor and sensory deficits
in Refsum disease are associated
with deafness, retinitis pigmentosa, scaly skin, and elevated serum phytanic
acid.
5.
Lipomas
and other masses in the lumbosacral canal may cause neurogenic foot deformities
and distal weakness, but sensory loss is in a radicular pattern, the arms are
spared, and the family history is usually negative.
6.
Myotonic
muscular dystrophy may present with a similar pattern
of distal atrophy and is a dominantly inherited disorder, but is distinguished
from Charcot-Marie-Tooth syndrome by the presence of myotonia, cataracts,
frontal balding, the absence of sensory abnormalities, and by the results of
EMG studies.
Course and Treatment.
The progression of disability is slow in Type I Charcot-Marie-Tooth syndrome
and very slow in Type II. Death does not occur as a result of this syndrome and
complete incapacitation is rare. There is no specific treatment. Braces for
correction of the foot-drop and hand deformities can be helped ambulatory by
splinting and orthopedic procedures.
Hereditary sensory neuropathy. These genetic disorders affect sensory fibers in peripheral
nerve and sometimes autonomic fibers as well. Dominantly inherited, or Type I,
hereditary sensory neuropathy causes progressive sensory loss beginning in the
first or second decade. There is progressive loss of pain, thermal sensibility,
light touch, and proprioception. Tendon reflexes are lost. Ulcerations may
develop on the feet and fingers owing to unperceived injuries. The disorder is
the result of a selective degeneration of sensory neurons in the dorsal root
ganglia.
Other
types of hereditary sensory neuropathy include an autosomal recessive form that
resembles the dominantly inherited disorder, congenital sensory neuropathy with
anhydrosis, hereditary sensory neuropathy with spastic paraparesis, and
familial dysautonomia (Riley-Day
syndrome). Familial dysautonomia is an autosomal recessive condition most
common in Jews, and may be a result of an inherited defect in synthesis of
nerve growth factor. It presents in infancy with lack of pain and temperature
sensibilities, gastrointestinal dysfunction, poor regulation of blood pressure,
and absence of fungiform papillae on the tongue.
Myotonic
muscular dystrophy is distinguished from the cases of muscular dystrophy of
relatively late onset by the distal weakness, myotonia, and the other
characteristic features of the disease, i.e., cataracts, testicular atrophy
and early baldness.
MUSCLE DISEASES ASSOCIATED WITH MYOTONIA
Myotonia is
a sustained contraction of muscles that may be induced by voluntary
contraction, percussion, or electrical stimulation. The primary failure of myotonia is a delayed relaxation due to
increased excitability of muscle demonstrated on electromyography, which records discharges of repetitive action
potentials following muscle contraction. Myotonia
occurs in myotonia congenita,
paramyotonia congenita, myotonic dystrophy, and hyperkalemic periodic paralysis.
Myotonia Congenita
Definition
Myotonia congenita is an hereditary condition
characterized by myotonia, a condition of delayed relaxation
following voluntary muscle contraction.
Etiology and Pathology
Myotonia congenita is caused by a genetically determined abnormality in the voltage gated
chloride channel. This results in a blocking of membrane chloride conductance
and action potentials can be triggered by a smaller than normal current,
resulting in a train of impulses that are self-maintaining, following
termination of the stimulating pulse.
Clinical Features
Myotonia congenita occurs in a mild form that is inherited as an autosomal dominant trait (Thomsen myotonia)
or a more severe form (Becker myotonia) inherited
as an autosomal recessive trait.
Symptoms of myotonia first appear in infancy
or childhood and consist of inability to relax a muscle following contraction.
The symptoms tend to increase during childhood and adolescence but may lessen
in severity in adult life. Myotonia occurs
only in skeletal muscle, and the patient has difficulty initiating movement
and making certain movements. Once repetitive movements are initiated, they can
be continued without difficulty. Sudden movements may initiate a sustained
contraction sufficient to throw the patient off balance. On grasping an object,
the patient is often unable to release the object for as long as 60 s. Patients
with myotonia congenita have a
well-developed musculature and have been described as herculean in appearance.
Percussion of an affected muscle produces percussion myotonia, a dimpling of the skin, and sustained contraction.
Percussion may also be followed by local swelling of muscle, termed myedema.
Diagnostic Procedures
The diagnostic procedure of choice is electromyography. There is marked increased
activity after insertion of the needle electrode. Traction or percussion of the
muscle produces a series of prolonged potentials that persist when the patient
is instructed to relax the contracted muscle. Contraction and relaxation of the
muscle produces a typical sound on electromyographic
examination, which has been termed the "dive bomber" effect.
Treatment
1. Mexiletine
150 mg ql2h, increasing to a maximum of 300 mg q8h, is the drug of choice to
reduce myotonia. An electrocardiogram
should be obtained before initiating therapy to exclude cardiac conduction abnormalities.
2.
Phenytoin (Dilantin) beginning 100
mg ql2h and increasing the dose until the serum levels are within
therapeutic range is also an effective treatment.
3. A number
of other drugs known to be effective in myotonia
include procainamide HC1
(Pro-nestyl) 50 mg/kg/day given in divided dosage four times a day and quinine
10 mg/kg/day in divided dosage. Quinine should always be followed by regular
visual and audiometric tests because of the risk of optic or otic neuritis.
4. Intractable
cases may respond to acetazol-amide
(Diamox) 8 to
30 mg/kg/day in
divided dosage.
cally relieved by acetazolamide. The clinical presentation
resembles the Thomsen type of myotonia congenita,
but the muscle stiffness is painful.
Sodium channel myotonias
respond to mexiletine therapy and acetazolamide. Other medications such
as phenytoin are less effective.
Chondrodystrophic Myotonia
This condition is inherited as an autosomal recessive trait and is characterized
by myotonia, short stature, blepharospasm, muscle hypertrophy, and skeletal
deformities. The affected infant presents with hip contractures or dislocation. This is followed by other joint contractures, progressive growth failure, and myotonia. There is a puckering of the mouth, blepharospasm, and small palpebral fissures. Intelligence is normal. Electromyographic findings are typically those
of myotonia. Muscular atrophy can occur
in older children. The myotonia responds
to mexiletine or acetazolamide.
Sodium Channel Myotonias
The following conditions are related to sodium channel
mutations.
1. Hyperkalemic
periodic paralysis.
2. Paramyotonia congenita.
3. Myotonia fluctuans.
4. Myotonia permanens.
5.
Acetazolamide-responsive myotonia.
Myotonia Fluctuans
This condition appears in adolescence and is
characterized by the appearance of myotonia of
delayed onset after exercise. The myotonia increases
following potassium loading but is unaffected by cold.
Myotonia Permanens
Symptoms are similar to myotonia fluctuans, but the myotonia
is permanent and more severe. There is continuous myotonic activity on electromyography and respiratory exchange may be affected by muscle
stiffness.
Acetazolamide-Responsive Myotonia As suggested by its
name, this form of myotonia is dramati-
Myotonic Dystrophy
Definition
Myotonic dystrophy is a multisystem disorder
inherited as an autosomal dominant trait
through a locus on chromosome 19.49 The disease is characterized by
progressive muscular weakness, myotonia, cataracts,
cardiac abnormalities, hypogonadism, and
frontal balding.
Etiology and Pathology
Myotonic dystrophy
is the product of an expanded CTG repeat in the 3' untranslated region of a
gene that encodes a protein kinase DM-PK
on chromosome 19ql3.3. There is an expansion of the repeat sequence in myotonic dystrophy and a positive correlation
between repeat size and clinical severity.50 Protein kinases phosphorylate neurotransmitters to achieve a physiological response on specific target
cells. Failure of protein kinase activity
may cause ion channel dysfunction in myotonia. Expression
is maximal in cardiac muscle in myotonic dystrophy
but is also present in skeletal muscle and brain.
Affected muscles show evidence of fibronecro-sis and
degeneration with areas of phagocytosis and increased endomesial connective
tissue. Surviving fibers show loss of
striations and a characteristic ring fiber has been described. Histochemical
studies reveal that degeneration is confined to type 1 muscle fibers and that
there may be some increase in the size of type 2 fibers.
Clinical Features
The signs and symptoms appear at any time from birth
to age 40 years. Hydrops fetalis has been
reported in congenital myotonic dystrophy
in a newborn infant who presented with hypertonia,
edema, pleural effusion, and
respiratory distress. Weakness tends to be nonprogressive
in the congenital form of myotonic dystrophy
but is slowly progressive in the noncongenital type of the disease. Myotonia is usually the first symptom and
affects the hand with later involvement of other muscles, particularly those
of the lower limbs. Muscle wasting also affects the hands first then spreads to
the facial muscles, muscles of mastication, the sternocleidomastoids,
the flexors and extensors of the forearm, the quadriceps, and the
dorsiflexors of the feet. The facial appearance is characteristic, with
bilateral ptosis and wasting, which has
been termed "hatchet face."
Patients with myotonic dystrophy
usually have involvement of other organ systems. These include:
1.
Cardiac abnormalities. Prolapsed
mitral valve and atrial flutter54
sometimes occur in the early stages of the disease. More advanced cases with severe
cardiac fibrosis suffer cardiac
arrhythmias. Syncopal attacks may occur.
Subclinical cardiac involvement is not
uncommon and may be responsible for sudden death in some cases.55
The number of CTG repeats in the myotonic dystrophy gene appears to be a
significant predictor of cardiac dysfunction in myotonic
dystrophy.
2. Brain involvement.
Neuropsychological testing
indicates functional impairment in the majority of patients with myotonic dystrophy. Mental retardation occurs
in about 70 percent of cases of congenital
myotonic
dystrophy but is
rarely severe. Progressive
dementia occurs in 75 percent of adults with
noncongenital disease. Magnetic
resonance imaging (MRI) shows cerebral atrophy and areas of increased
signal intensity in the white matter in most adults with myotonic dystrophy. However, there is no
correlation between the
extent of white
matter changes and neuropsychological impairment.
3.
Ophthalmic abnormalities. Subcapsular lens
opacities, which enlarge and eventually impair vision, are present in most
patients.
4. Endocrine
abnormalities. Primary gonadal failure
and gonadal atrophy occur in both sexes.
Impotence, loss of libido, and testicular atrophy
occur in the male. Mild diabetes mellitus may be present in both sexes.
5. Skin and
skeletal abnormalities. Frontal balding
occurs at an early stage in the male. A high-arched palate may be present.
6. Smooth
muscle abnormalities. There is impairment of mobility in the gastrointestinal
tract, with dilatation of the colon in advanced cases.
7.
Respiratory abnormalities. Respiratory insufficiency, which has been
associated with neuronal loss in the
medulla, resulting in hypoventilation is
a feature in the late stages of the disease when there is an increased risk of
aspiration pneumonia.
8. Hearing
loss. There is a high incidence of sensorineural
hearing loss in myotonic dystrophy.
9. Peripheral
neuropathy of axonal type is responsible
for the areflexia, distal sensory impairment, and fasciculations seen in some
cases.
Children born to mothers with myotonic dystrophy may present with congenital myotonic dystrophy in the neonatal period. This
condition is characterized by hypotonia, facial
diplegia, dysphagia, mental retardation,
a high-arched palate, and tented lips. Myotonia
develops later in the course of this condition.
Diagnostic Procedures
1. DNA analysis using a DNA probe allows direct
identification of the myotonic dystrophy
mutation in DNA extracted from peripheral blood lymphocytes. Southern blot
analysis can be used to detect abnormally large DNA fragments with expanded
gene repeats. The polymerase chain
reaction will detect small expansions of the unstable DNA sequence. DNA
testing can also be used for prenatal diagnosis of myotonic dystrophy, as well as detection of carriers.
2. The effect
of temperature change. Myotonia may be
difficult to demonstrate in some cases. Submersion of the hands in cold water
for several minutes may facilitate the appearance of myotonia.
3. The
electromyogram is characteristic with an increase in insertional activity and
typical myotonic discharges following
voluntary contraction of muscle.
4. Cardiac
involvement affects predominantly the conduction system in the heart. Atrial fibrillation, atrial flutter, a prolonged PR interval, and various conduction
defects may be present.
5. Slit lamp
examination reveals the characteristic lens opacities.
6. Serum
tests. There are abnormally low levels
of IgG, an abnormal glucose tolerance test, and low follicle-stimulating
hormone levels in most cases.
7. The MRI
and computed tomography (CT) scans and chest and skull x-rays. Thickening of
the calvarium and enlargement of the frontal sinuses are often present on skull
x-rays. Microcephaly, calcification of the basal ganglia, and cerebral atrophy
may be demonstrated by CT scan. The MRI shows the presence of increased signal
intensity in the white matter.
8. Pure tone screening
and impedance audiometry will detect sensorineural hearing loss.
9. The
diagnosis can be established by a muscle biopsy, which shows characteristic
findings of a dystrophic process.
Treatment
1. The relief
of myotonia is discussed under myotonia congenita.
The calcium channel blocking agent, nifedipine, which has no effect on cardiac conduction, decreases myotonia in doses of 10 to 20 mg q8h.
2. In the
latter stages, when the risk of aspiration
pneumonia increases, respiratory
infection should be treated with appropriate antibiotics, postural
drainage, and chest percussion.
3. Muscle
weakness can be severe in those with marked expansion of CTG repeats. These
patients need supportive care, including splinting and use of an electric cart
or wheelchair.
4.
Cardiac involvement is often
the main complication. Patients
require regular evaluation of cardiac function and appropriate treatment for arrhythmias.
5. Preoperative and postoperative care and intraoperative monitoring are requred to avoid
complications of anesthesia, which carry increased morbidity and may be
lethal in myotonic dystrophy.
6. Pregnancy
and delivery carry a high risk of complications in mothers with myotonic dystrophy and their offspring. Consequently,
mothers should be monitored for increased muscle weakness involving respiratory
muscles, reduced fetal movements and hydramnios, and prolonged, often
ineffective labor. There is also
an increase of spontaneous abortion earlier in pregnancy.
Obstetric complications include retained placenta,
placenta previa, and neonatal death.
Prognosis
Myotonic dystrophy
is a chronic condition with progressive deterioration in most cases. In
noncongenital forms of the disease, death occurs between ages 40 and 60 years
due to cardiac or respiratory dysfunction.
In congenital muscular dystrophy, there is a 25
percent chance of death before 18 months of age, and a 50 percent chance of
survival until the mid-thirties.
Proximal Myotonic
Myopathy
This rare variant of myotonic
dystrophy is inherited as an autosomal dominant
trait in which there is no abnormal enlargement of the CTG repeat in the gene
for myotonic dystrophy.
Clinical Features
Symptoms are present in adults with complaints of
stiffness in the thigh muscles followed by a more generalized myalgia, which
can be severe in the thighs. Cataracts can occur at an early stage, and grip myotonia is prominent in most cases. Muscle
weakness is often delayed and fluctuates in intensity. Electromyography is abnormal and demonstrates myotonic discharges. The condition is probably
compatible with a normal
life span because severe cardiac
involvement has not been demonstrated.
Treatment Supportive. There is no specific treatment for these conditions.
Benign Congenital Myopathies
The benign congenital myopathies
are a heterogenous group of rare
disorders. Most congenital myopathies are
mild, slowly progressive or nonprogressive, infantile
or adolescent conditions associated with specific structural alterations in
muscle fiber.
Nemaline myopathy usually
presents at birth or in infancy, but symptoms may be delayed until adolescence
or adult life. The condition is inherited as an autosomal
dominant or recessive trait and presents with generalized muscle hypotonia and weakness from birth or infancy,
high-arched palate, long face, pigeon chest, scoliosis,
and pes cavus. The severity varies
from mild weakness to wheelchair dependency or even use of a mechanical
ventilator.
Central core disease is a mild myopathy inherited as an autosomal dominant
trait, presenting in infants. The condition is nonprogressive,
with proximal muscle weakness and pes cavus.
Type I muscle fibers contain central cores of myofilaments
lacking mitochondria.
Myotubular myopathy presents
as a severe myopathy in infancy, with hypotonia, respiratory failure, and death.
Milder cases can occur with survival and these patients present with hypotonia, muscle weakness, delayed psychomotor development, and mental
retardation. Muscle biopsies show small myotube-like fibers with central nuclei
dispersed between normal-sized fibers.
Vacuolated myopathy is a rare condition of juvenile onset, slow progression, and
predominantly proximal muscle weakness. Muscle biopsy shows vacuolated muscle fibers, which probably
represent superficial muscle fiber injury associated with sarcolemmal invagination, the result of deposition of
complement membrane attack complex on the damaged cell surface membrane.
Diagnostic Procedures
The diagnosis may be established by a muscle biopsy,
which indicates a myopathic process. In
many cases, a definitive diagnosis requires electron microscopy.
Prognosis In
the majority of cases, the congenital myopathies
are slowly progressive conditions; in some cases, the process appears to
become arrested in adolescence or adult life. Other cases show a slow
deterioration requiring the eventual use of a wheelchair. There is an increased
risk of respiratory infection, which may be fatal unless treated promptly.
Muscle Carnitine Deficiency
This condition is a proximal myopathy with onset in childhood and exhibiting a slowly
progressive course. Cardiac muscle involvement and myoglobinuria occur in some cases. Muscle biopsy shows a severe vacuolar myopathy affecting type 1 fibers, with
vacuoles staining positive for lipid. The condition results from impaired carnitine transport into muscle; serum carnitine levels are normal or occasionally
low, but muscle carnitine content is
reduced.
Zidovudine (AZT)
therapy may induce a similar myopathy by
depletion of mitochondrial DNA, reduced
muscle carnitine levels, and lipid storage in muscle fibers.
A systemic form of carnitine
deficiency can result from many inborn errors of metabolism. All are
associated with deficiency in free carnitine resulting
in the limited entry of low-chain fatty acids into mitochondria. Affected
children have recurrent attacks of encephalopathy
resembling Reye syndrome and later development of myopathy, hepatomegaly, and cardiomyopathy.
DISORDERS CHARACTERIZED BY STIFFNESS AND SPASMS
Stiff-Person Syndrome (Stiff-Man Syndrome)
Definition
The stiff-person syndrome is a rare disorder characterized
by persistent muscle contraction, spasms, and muscle cramps, which disappear
during sleep.
Etiology and Pathology
The condition is believed to be the result of an
autoimmune reaction where antibodies are directed against glutamic acid decarboxylase
(GAD), an intracellular enzyme in y-aminobutyric
acid (GABA)-containing neurons. This leads to destruction of these
neurons, with a lack of inhibitory influence by the GABA motor neuron system,
resulting in continuous motor neuron activity and clinical rigidity.
Clinical Features
The patient initially experiences muscle aches and
pains followed by stiffness of the muscles of the trunk, limbs, and neck.
Voluntary movements are slowed. Emotional or sensory stimuli may exacerbate the
stiffness and produce painful spasms. On examination, the muscles are
contracted and the patient is unable to relax them. The disorder is progressive
and eventually results in considerable disability. Misdiagnosis of a psychogenic movement
disorder is not unusual.
A congenital form of the disorder has been reported.
In these cases, stiffness is present at birth and gradually resolves, so that
by age 3, the tone is almost normal. Later, in adolescence or adulthood, the
stiffness reappears in a milder form.
Diagnostic Procedures
Electromyography reveals persistent contractions of muscle fibers and bursts of motor
unit potentials during spasm.
Treatment
The stiffness and spasm improve with diazepam (Valium) 20 to 200 mg/day, or clonazepam, or valproic
acid. Baclofen (Lioresal), which
reduces spasticity by activating GABA-b
receptors in the dorsal horn of the spinal cord, reduces muscle contractions
and spasms. The use of the baclofen pump
is a most effective form of therapy, but pump failure may be associated with acute
autonomic disturbances, a
life-threatening situation.
Acquired Neuromyotonia (Isaac Syndrome)
Neuromyotonia is a syndrome associated with a known
neuropathic process such as a hereditary neuropathy or an acquired disorder,
with or without an associated neuropathy. The syndrome is characterized by myokymia (muscle twitching at rest), cramping
of muscle often induced by muscle contraction, impaired muscle relaxation,
muscle weakness, increased sweating, and an elevated CK level. Neuromyotonia is
believed to be an autoimmune disease where antibodies are directed against
potassium channels in motor neurons proximal to the terminal branches.83
Electromyography reveals neuromyotonic
discharges characterized by bursts of motor unit action potentials firing at
150 to 300 Hz for several seconds, or occasionally, myokymic discharges of
motor unit action potentials recurring regularly at rates up to 60 Hz. Motor
nerve conduction studies may demonstrate a peripheral neuropathy in some cases.
Most patients show excellent response to phenytoin or
carbamazepine. Refractory patients should be treated with plasmapheresis.85
FAMILIAL PERIODIC PARALYSIS
There are three types of familial periodic paralysis,
all of which are inherited as an autosomal dominant
trait.
Hypokalemic Periodic Paralysis
Definition Hypokalemic periodic paralysis
is an inherited condition of episodic
muscle paralysis associated with hypokalemia.
Etiology and Pathology
Familial hypokalemic periodic
paralysis has been linked to a mutation in chromosome lq31-32. This area is the
site of the gene for the alpha: subunit of the skeletal muscle,
DHP-sensitive calcium channel. Mutation in this gene modifies the function of
the DHP receptor by altering calcium channel current in hypokalemic periodic paralysis.
Muscle biopsy shows the presence of vacuoles, containing glycogen, in muscle fibers, which are present during an attack, and
which may decrease in number immediately after an attack. Other features include
tubular aggregates derived from sarcoplasmic
reticulum, variations in fiber size, and increased internal nuclei.
Clinical Features
Hypokalemic periodic
paralysis is more common in men and occurs predominantly during the teens and
twenties. Attacks begin at night and the patient awakens with weakness of all
skeletal muscles except those involved in respiration and speech. However,
there are reports of respiratory involvement and some deaths from respiratory
failure, but this is a rare complication. Involved muscles are firm and tender
to palpation. The neurological examination is normal, with sparing of muscles
supplied by cranial nerves and those involved in respiration and speech. The
attacks last from several hours to days. Several factors have been reported to
precipitate attacks. These include large meals with a high carbohydrate
content; exertion; trauma; heavy alcohol ingestion;
upper respiratory tract infection; cold weather; and administration of
insulin, thyroid hormone, steroids, epinephrine,
thiazides, or licorice. Permanent muscle weakness of the proximal
musculature, but spreading later to a more diffuse involvement, can occur.
Diagnostic Procedures
1. The
movement of potassium, sodium chloride, phosphate, ions, and water into the
muscle fibers during an attack is reflected in decreased serum potassium level
below 3.5 mEq/L.
2. Urinary
excretion of potassium and sodium is decreased.
3. Electromyography shows decreased amplitude,
number, and duration of motor unit potentials or electrical silence during
periods of paralysis. Muscle fiber velocity is reduced between attacks.
4.
Provocative tests to induce hypokalemia, using
glucose and insulin, require close monitoring by electrocardiography because hypokalemia
may induce cardiac arrhythmia. A 10-min bicycle exercise test is a
safer alternative. Patients with hypokalemic periodic
paralysis experience a minimal increase in serum potassium levels 10 and 30 min
after exercise, compared to a control population where the increase is
significant.
5. Corticotropin 80
to 100 IU intravenously can be used in suspected periodic paralysis of either
hypo- or hyperkalemic type. Corticotropin will
induce an attack of paralysis with appropriate changes in serum potassium
concentration in each condition.
Treatment
1. Attacks may
be terminated by oral or parenteral administration
of potassium and may be prevented by oral administration of potassium 130
mEq/day.
2.
Acetazolamide 125 mg q.o.d., increasing by increments to achieve an optimum
dosage, to a maximum of 500 mg ql2h orally, is the drug of choice to prevent
attacks.
3. Spironolactone 100 mg daily or bid is effective
in reducing the number of attacks.
4. Other drugs
that may be of benefit include the carbonic anhydrase inhibitor
dichlorphenamide, the calcium channel blocking
agent, verapamil, or lithium.
5. Predisposing
factor should be avoided.
Secondary Hypokalemic Periodic
Paralysis
A number of disorders with associated hypokalemia may develop symptoms of periodic paralysis
resembling hypokalemic paralysis. This
syndrome occurs in thyrotoxic periodic
paralysis, which is seen predominantly in men of Asian extraction and is rare
in the
Diagnostic Procedures
Primary hypokalemic periodic
paralysis and thyrotoxic periodic
paralysis may be distinguished from nonthyrotoxic secondary hypokalemic periodic paralysis by a prolonged
exercise test.
Treatment
Intravenous propranolol
may terminate an attack in patients with thyrotoxic
periodic paralysis, who fail to respond to potassium therapy. The
underlying cause of secondary hypokalemic periodical
paralysis should be identified and treated.
Hyperkalemic Periodic Paralysis
Definition Hyperkalemic
periodic paralysis is a condition inherited
as an autosomal dominant trait, where
periodic paralysis is associated with elevation of serum potassium levels.
Etiology and Pathology
The disease has been linked to allelic defects in a gene that encodes for the alpha subunit of the
tetrodotoxin-sensitive skeletal muscle sodium channel, localized to chromosome
17q23 1-25.3.10° There is non-inactivation of this channel during an
episode of paralysis, with influx of sodium resulting in sustained membrane
depolarization.
Muscle biopsy may be normal or may show some
nonspecific features, such as large variation in fiber size and central nuclei,
increased subsarcolemmal glycogen and the
presence of vacuoles in some cases.
Clinical Features
Attacks begin in childhood and occur during the day,
usually while resting after exercise. Each attack may be preceded by a
sensation of heaviness and stiffness in the muscles and paresthesias in the face and extremities. Episodes usually last 1
h. In addition to exercise, paralysis can be precipitated by exposure to cold,
hunger, administration of potassium, emotional stress, and pregnancy. Attacks
may be prevented by eating a carbohydrate after exercise.
Muscle weakness affects the lower extremities predominantly,
but upper extremity and neck muscles can be involved. Mild myotonia can be experienced during muscle
weakness. Permanent muscle weakness is an occasional complication. Cardiac
arrhythmias have been reported in a few cases.
Diagnostic Procedures
1. Serum
potassium levels are increased during an attack, but normal potassium levels
have been recorded in some cases, giving
rise to so-called normokalemic periodic paralysis.
2. Serum
sodium levels decrease as sodium enters muscle fibers.
3. Urinary
potassium increases during an attack, resulting in a drop in serum potassium
levels and recovery.
4. Electromyography may reveal electrical silence
during paralysis or fibrillations, positive sharp waves, and myotonic discharges during paresis. Motor unit
potentials are decreased in number and duration.
5.
Provocative test with administration of 2 to
Treatment
Attacks can be prevented by thiazide diuretics—hydrochlorothiazide
25 to 75 mg/day. Acetazolamide, albuterol,
and metaproterenol are also effective.
Paramyotonia Congenita
Definition
This is a familial condition characterized by muscle
stiffness induced by exposure to cold or by exercise, followed by muscle
weakness. The condition is inherited as an autosomal
dominant trait.
Etiology and Pathology
Paramyotonia congenita, like hyperkalemic periodic paralysis, is the product of a defect in the
skeletal muscle sodium channel. Linkage has been established between paramyotonia congenita and the gene encoding
the alpha subunit of the muscle sodium channel localized to chromosome 17q20
231-225.3.
Muscle biopsy may be normal or show nonspecific
changes.
Clinical Features
The symptoms are present at birth. Babies develop
mask-like facies on exposure to a cold environment. This is followed by
paradoxical muscle stiffness that increases with exercise. Attacks of weakness
are delayed until adolescence and often last several hours or days. The
weakness has an upper limb predominance; respiratory muscle involvement is
rare. Symptoms can be more severe during pregnancy. Permanent weakness does
not occur.
Diagnostic Procedures
1. Muscle
cooling results in symptoms of weakness and reduced compound muscle potentials
on electromyography.
2. Electromyography
demonstrates myotonic discharges
at room temperature, enhanced by cooling, but myotonic
discharges may decrease or disappear with the onset of paralysis.103
Treatment
1. Avoid
exposure to a cold environment, which can precipitate an attack.
2. Mexiletine,
a cardiac antiarrhythmic drug, is effective
in reducing both myotonia and weakness.
Diseases of the Basal Ganglia
Progressive Supranuclear
Palsy
Definition
Progressive supranuclear palsy
(PSP) is a chronic progressive brain disease characterized by supranuclear ophthalmoplegia affecting chiefly
vertical gaze, pseudobulbar palsy,
prominent neck dystonia, behavioral and
cognitive disturbances, parkinsonism, axial
dystonia, gait disturbances, impaired
equilibrium and falls.
Etiology and Pathology
The etiology is unknown, but the condition may be
related to exposure to an exogenous toxin.
The brain shows evidence of atrophy. There is
decreased pigment in the substantia nigra and
locus ceruleus and loss of neurons in the basal ganglia, brainstem and cerebellum. Neurofibrillary tangles are present in the
cerebral cortex, caudate nucleus, puta-men, globus
pallidus, subthalamic nucleus, brainstem, and cerebellum.
Clinical Features
The prevalence of PSP is 1.4 cases per 100,000, with
an annual incidence of 3 to 4 per million. The disease is usually sporadic, but
familial cases have been described, suggesting an autosomal dominant trait. The symptoms begin in the early sixties
and are seen in all ethnic groups. Sur vival following the onset of overt
symptoms is from 6 to 9 years. Early symptoms consist of bradykinesis and supranuclear gaze palsy, with voluntary down
gaze less than 15°, impaired optokinetic nystagmus,
stimulus downward, and horizontal square wave jerks. This is followed by the
development of rigidity affecting the axilla muscles more than the limb muscles,
in the lower limbs more than the upper limbs. Parkinsonian
features, including paucity of blinking and a fixed facial expression,
occur early in the course of the disease. Progressive dysarthria, increased reflexes, and extensor plantar responses are
constant features. The head and neck are held in extension, and there are
frequent falls in a patient with a relatively well-preserved gait. Torticollis,
blepharospasm, and stuttering speech
have been described. The dementia associated with PSP is often mild, with
cognitive slowing, but almost all patients suffer from apathy and disinhibition
occurs in about one-third of cases.69 Eventually the patient becomes
bedridden and dies from intercurrent infection.
Diagnostic
Procedures
The diagnosis depends largely on clinical
presentation and the characteristic progression of the disease.
The MRI scan shows diffuse brain atrophy, including cerebellar atrophy, atrophy of the midbrain, a widening of the posterior third
ventricle, and increased signal intensity in the periaqueductal region in the T2-weighted images.
Differential
Diagnosis
In the early stages of PSP, the condition is frequently misdiagnosed as Parkinson disease. Other
conditions that might be considered include multisystem atrophy, including
striatonigral degeneration, Shy-Drager syndrome, and olivopontocerebellar atrophy.
Treatment
Carbidopa-levodopa therapy may produce some improvement in the early stages of the disease
and at relatively high doses. Levodopa content
up to 1500 mg 24 h can be used without producing adverse effects.
Amitriptyline beginning at 10 mg q.h.s. and increased by 10 mg q5d, up to 100
mg q.h.s., is of established benefit. Amantadine
and selegiline may produce
temporary improvement.
Multiple System Atrophy
Multiple system atrophy (MSA) is a sporadic,
progressive adult-onset disorder characterized by autonomic dysfunction, parkinsonism,
and ataxia in any combination.
MSA encompasses conditions described previously under the heading of
striatonigral degeneration (SND), sporadic olivopontocerebellar
atrophy (OPCA), and Shy-Drager syndrome (SDS), presenting with any
combination of extrapyramidal corticospinal
cerebellar and autonomic signs and
symptoms.
Etiology
and Pathology
The etiology is unknown. Pathological changes consist of neuronal loss and gliosis in the striatal, nigral, and
olivopontocerebellar systems, with the
presence of oligodendroglial and neuronal intracytoplasmic
and intranuclear argyrophilic inclusions containing accumulations of tubular
structures.
Clinical
Features
Initial symptoms consist of parkinsonism (SND type), or cerebellar
ataxia (OPCA type), or autonomic dysfunction
(SDS).
Parkinsonism consisting
of akinesia and rigidity is an early feature
of SND, accompanied by a jerky irregular tremor in some cases. Cerebellar signs with intention tremor or
heal-to-shin ataxia occur in the early
stages of OPCA, with later development of postural instability and gait ataxia.
Autonomic failure
is a feature of SND and OPCA or SDS and may be the presenting symptom or
develop later in the course of the disease. Symptoms consist of impotence,
mild-to-moderate postural hypotension, urinary incontinence or retention, and syncopal episodes. Corticospinal tract involvement, with increased tendon reflexes and
extensor plantar responses, are usual, but spasticity
and lower limb weakness are uncommon.
Many patients develop nystagmus, saccadic eye movements, and dysarthria, which can be severe in some cases.
Upward, downward, or horizontal gaze may be limited. Respiratory stridor is a later feature, and
stimulus-sensitive myoclonus occurs in
about one-third of cases. Sensory changes are minor, with some impairment of
vibration and position sense in the toes.
Patients presenting with prominent autonomic dysfunction and labeled SDS
ultimately develop parkinsonism or cerebellar dysfunction, or both. Consequently,
SDS is probably a variant of MSA, with later development of the features of SND
or OPCA.
Diagnostic
Procedures
An MRI scan may show brainstem
and cerebellar atrophy in the
later stages of OPCA.
Treatment
Parkinsonism responds
to lev-odopa preparations in about
one-third of cases. Response to dopamine agonists
is poor.
Orthostatic hypotension
often responds to head uptilt at night, elastic support stockings, or an
elastic leotard and an increased salt intake. When syncope is a feature,
additional treatment is indicated.
Prognosis
Life expectancy is reduced to a considerable degree.
The mean survival time is approximately 10 years.
Olivopontocerebellar
Atrophy
Definition The OPCAs are a group of inherited
degenerative disorders characterized by a predominant involvement of the brainstem and cerebellum.
Etiology
and Pathology
The disorders may be inherited as an autosomal
dominant or autosomal recessive
trait and have in common neuronal degeneration
and gliosis in the cerebellum, brainstem, spinal cerebellar tract, and dorsal columns. Histopatholog-ical changes
typical of MSA have been described in some cases, indicating a close
relationship between inherited OPCA and MSA. However, the inclusion bodies of
MSA are usually absent in inherited OPCA.
Clinical
Features
One of the characteristics of olivopontocerebellar degeneration is the wide variety of
presenting symptoms. Affected members of the same family may present with a
totally different clinical picture. Eventually, however, the affected members
of the family will develop ataxia, nystagmus,
intention tremor, and titubation of the head. There may be generalized
rigidity and parkinsonian features in
some cases. The speech becomes severely dysarthria
The tendon reflexes may be hyperactive or hypoactive, and there is a
bilateral extensor plantar response. Some patients develop signs of dementia as
a late feature of the disease. Others have prominent autonomic symptoms, with incontinence and orthostatic hypotension and can be regarded as a form of multiple
system disease. Sleep disorders, including hyposom-nia, rapid eye movement
sleep without atonia, and sleep apnea are
present in some cases.
Diagnostic
Procedures
Magnetic resonance imaging and CT scanning may show
atrophy of the brainstem and atrophy of
the cerebellum with enlargement of the fourth ventricle, ambiens, and
pre-pontine cisterns.
Treatment Treatment is symptomatic. Sleep apnea may respond to trazodone 50 mg q.h.s.
Prognosis There is typically a relentless progression
of the disease with death occurring from intercurrent
infection approximately 20 years after the development of initial
symptoms.
Familial Spinocerebellar
Ataxias
The autosomal dominant
spinal cerebellar ataxias (SCAs) are a
heterogeneous group of multisystem neurodegenerative
diseases that have been mapped to five chromosomes.
The clinical features, pathological changes, and gene
location are listed in Table 14-4.
Families diagnosed with SCA-3 may be examples of
Machado-Joseph disease, exhibiting the type 2 phenotype.
Treatment
No therapeutic measures are available to treat these diseases. Patients
require aids to maintain ambulation and
prevent falling.
Table 14-4
Familial spinocerebellar
ataxias
Type |
Clinical features |
Pathology |
Gene location |
SCA-I |
Ataxia, optic
atrophy, ophthalmoplegia, corticospinal tract
involvement, extrapyramidal features |
Neuronal loss,
Purkinje cells, pontine nuclei,
inferior olivary nuclei |
6p23-24 |
SCA-2 |
Ataxia, slow
saccades, ophthalmoplegia, peripheral
neuropathy |
Neuronal loss,
Purkinje cells, inferior olivary nuclei, substantia
nigra, degeneration of posterior columns of spinocerebellar tracts |
12q23-24 |
SCA-3 |
Ataxia, nystagmus,
corticospinal tract involvement, dystonia, hyporeflexic tendon reflexes ankles |
Neuronal loss,
molecular layer cerebellum, pontine nuclei |
14q24-q32 |
SCA-4 |
Ataxia, sensory
axonal neuropathy, corticospinal tract involvement |
Unknown |
16q24ter |
SCA-5 |
Benign ataxic course,
later appearance of corticospinal tract
involvement |
Unknown |
11 |
SCA-7 |
Ataxia, macular dystrophy, retinal degeneration |
Unknown |
3p14-21.1 |
Machado-Joseph disease Type 1, early onset |
Ataxia, ophthalmoplegia Plus dystonia corticospinal tract
involvement |
Lost neurons, substantia
nigra, subthalamic nuclei, pontine nuclei,
dentate nuclei, |
14q32.1 |
Type 2, onset middle age Type 3, onset fifth decade |
Corticospinal tract involvement
Amotrophy |
anterior horn cells, posterior root ganglia,
degeneration, Clarke's column, spinocerebellar
tract |
|
Dentatorubropallidoluysian atrophy |
Ataxia, choreoathetosis,
myoclonus, epilepsy, dementia |
Lost neurons, dentate nucleus, red nucleus, globus pallidus, subthalamic nucleus, Purkinje cells, brainstem tegmentum, corticospinal tracts |
12p12ter |
Friedreich's
Ataxia
Definition
Friedreich's ataxia is a degenerative disease of childhood and early adult life that primarily
involves the long tracts of the spinal cord. The disease is inherited as an autosomal recessive trait in which the Friedreich's ataxia gene has been mapped to the
proximal long arm of chromosome 9 (9ql3-q21). This mutation consists of an
unstable expression of GAA repeats in the first intron of the frataxin gene on chromosome 9, which encodes a
protein of unknown function. Larger GAA expansions correlate with earlier age
of onset and shorter time to loss of ambulation.
Pathological changes consist of atrophy with
demyelination involving the posterior columns and the spinocerebellar, and corticospinal tracts
of the spinal cord. The areas of degeneration show a loss of axons and myelin with secondary gliosis. The degenerative changes begin in the neurons of the
dorsal root ganglia and are followed by a dying back of axons of large myelinated fibers
in the peripheral nerve and in the posterior columns of the spinal cord. Similar
neuronal changes eventually involve the
nucleus gracilis and cuneatus, with
degenerative changes in the medial lemniscus. The
dorsal and ventral spinocerebellar tracts
are similarly involved. The corticospinal tract
shows demyelination with increased involvement in a caudal direction. Loss of
Purkinje cells in the cerebellum and degeneration of the dentate nucleus with axonal loss and demyelination of the superior cerebellar peduncle also occur.
Cardiac hypertrophy and diffuse myocardial fibrosis with degeneration of
cardiac muscle cells are an invariable finding.
Clinical Features
The first symptoms of ataxia and
easy fatigability develop before 10 years
of age in about half the cases, and the majority have well-established signs
before the age of 20. The ataxia is
progressive, beginning in the lower limbs and gradually involving the trunk and
upper limbs. Cranial nerve examination reveals reduced visual acuity in some cases,
horizontal nystagmus, saccadic pursuit
eye movements, hearing loss, dysarthria, and
dysphagia. The motor system shows wasting
of muscles and weakness of all four limbs. Rapid alternating movements are
slowed, with overflinging and past pointing on finger-to-nose testing and
bilateral intention tremor. The gait is wide based due to a combination of
posterior column dysfunction, spasticity, and
cerebellar ataxia. Involvement is
symmetrical in most cases, but some asymmetry is not unusual. Sensation is
abnormal, with preservation of touch but impairment of temperature, vibration,
and position sense in hands and feet. Tendon reflexes are depressed or absent,
but there is a bilateral extensor plantar response. Early onset ataxia with cardiomyopathy
and retained reflexes has been described.83d The fully
developed syndrome is characterized by a mild degree of dementia. Optic
atrophy with visual failure is not unusual and many patients have a
progressive hearing loss. Speech is slow, staccato, and explosive in more
developed cases but may eventually become unintelligible in the later stages
of the disease.
Examination of the spine shows scoliosis in the majority but not all cases and there is deformity
of the feet with pes cavus and extension
of the metacarpophalangeal joints and
flexion of the interphalangeal joints in about 90 percent of patients.
Cardiomyopathy occurs in about two-thirds of the cases and electrocardiographic (ECG) abnormalities can occur early in the
disease and are present in most cases. Death from congestive heart failure or
cardiac arrhythmia is common.
Diagnostic Procedures
1. Clinical
diabetes mellitus due to insulin-resistant B cell deficiency and type 1
diabetes are present in about 20 percent of cases.
2. Serum bilirubin levels are frequently elevated.
3. Pulmonary
function tests show progressive impairment due to progressive kyphoscoliosis.
4. The ECG is
abnormal and many patients have obstructive hypertrophic
cardiomyopathy.
5. The EEG
shows mild nonspecific abnormalities in most cases.
6. Motor nerve
conduction velocities are normal, but sensory conduction velocities are
prolonged or absent in the lower limbs.
7. Somatosensory evoked potentials recorded after peroneal nerve stimulation are abnormal,
indicating spinal cord involvement.
Differential Diagnosis
1. Other forms
of spinal cerebellar degeneration. The
characteristic finding of moderately rapid progression and
cardiac involvement differentiate Friedreich's
ataxia from other spinocerebellar degenerations.
2. Congenital
abnormalities. The Arnold-Chiari malformation, platybasia, and odontoid
compression can be excluded by MRI studies.
3. Arteriovenous (AV) malformation of the spinal
cord. Increased tone and hyperreflexia occur only below the level of the
malformation. There are progressive urgency of micturition and a sensory level.
The AV malformation can be demonstrated by MRI scanning.
4. Syphilis.
Syphilitic pachymeningitis is rare. The
condition is associated with a CSF pleocytosis and increased protein content.
The serological test for syphilis is
positive.
5. Subacute combined degeneration can cause confusion
if it occurs before overt signs of pernicious anemia. Serum vitamin B12
levels are depressed.
6. Spinal cord tumors
tend to cause pain, particularly nerve root pain. There is progressive spasticity below the level of the lesion and
progressive urgency of micturition. Examination shows a sensory level. The
diagnosis can be established by MRI scanning.
7. Multiple
sclerosis. The spinal cord form of multiple
sclerosis can cause
some confusion with Friedreich's
ataxia. There tends to be a relapsing and remitting course in multiple
sclerosis, with bladder involvement and patchy sensory loss. Visual evoked potentials
and auditory evoked potentials may be abnormal in multiple sclerosis. The CSF
may show an elevated protein, increased gamma globulin content, and the
presence of oligoclonal bands in the CSF, which are not present in the serum.
An MRI scan of the brain is usually abnormal.
8. Vitamin E
deficiency is a condition closely resembling Friedreich's
ataxia. Serum vitamin E levels are normal in Friedreich's ataxia.
Treatment The
treatment is symptomatic. Cardiac and pulmonary complications should receive
prompt attention in advanced cases because they are frequently fatal.
Prognosis The
disease runs a progressive course and most patients are unable to walk 5 years
after the appearance of symptoms. Death occurs 10 to 20 years after onset from pulmonary
or cardiac complications.
Familial Spastic Paraplegia
Definition This is a slowly progressive spastic paraparesis, without involvement of other cerebrospinal or cerebellar systems.
Etiology
and Pathology
The condition is inherited as an autosomal
dominant or autosomal recessive
trait but occasionally appears to be a sex-linked recessive trait and occurs
more frequently in males.
In some cases, the disease may represent a forme
fruste of an inherited spinocerebellar degeneration.
Clinical
Features
The first symptoms begin in the first two decades of life, although a
rare form with later onset has been described. There is a slowly progressive
spastic paraparesis evolving to spastic
paraplegia, with increasing weakness and spasticity
of the lower limbs, increasing tendon reflexes and extensor plantar
responses.
Treatment
It is important to rule out compressive conditions
of the spinal cord, particularly cervical spondylosis
in all cases. Because the condition is slowly progressive, most cases
are not associated with the reduction of a normal life span.
There is no definitive treatment for this condition.
The use of a baclofen pump should be
considered in those with advanced disease and severe spasticity.
Familial Episodic Ataxia
This uncommon condition is characterized by episodic ataxia, which occurs in two distinct forms,
familial episodic ataxia with interictal myokymia (EA1) and familial episodic ataxia with interictal nystagmus (EA2). In EA1,
the result of a genetic defect located on chromosome 12pl3, the attacks are
brief, lasting no more than several minutes. EA2, the result of a genetic
defect on chromosome 19p, is characterized by longer episodes of ataxia of several hours' duration. In EA2,
symptoms vary from pure ataxia to signs
suggesting involvement of the cerebellum, brainstem,
and cerebral cortex, and some individuals exhibit a progressive ataxia indistinguishable from dominantly inherited
spinal cerebellar ataxia. About 50
percent of patients with EA2 experience basilar migraine
or hemiplegic migraine, the latter linked to a genetic defect on chromosome
HEREDITARY DISEASES OF WHITE MATTER
The Leukodystrophies
The leukodystrophies are
a rare group of genetically determined conditions characterized by metabolic defects
in the formation or breakdown of myelin (Table 14-5). Metachromatic leukodystrophies are the most frequently encountered
in this group of rare metabolic disorders.
Metachromatic Leukodystrophy
Definition
Metachromatic leukodystrophy is
characterized by a degeneration of myelin in the central and peripheral
nervous systems due to lack of the enzyme arylsulfatase A. The condition is transmitted
as an autosomal recessive trait and the
mutated gene is located on chromosome 22.
Etiology
and Pathology
There is a disturbance of the sphingolipid metabolism in which
galac-tosyl-3-sulfate ceramide (sulfatide) is metabolized. The decreased activity
of arylsulfatase A in metachromatic
leukodystrophy leads to accumulation of sulfatide in the central and
peripheral nervous systems.
The brain is normal in size and weight. The white
matter is firm and brownish in appearance, with occasional cavitation. Microscopic abnormalities include
loss of myelin sheaths, axonal degeneration, loss of oligodendrocytes, and accumulation of lipid lying free within macrophages and
neurons. The peripheral nerves show myelin degeneration and axonal loss, with accumulation
of lipid. Lipid deposits are also present
in the Kupffer cells of the liver and the renal tubules. The ganglion cells of
the retina are heavily involved.
Clinical Features
There are three clinical forms of metachromatic leukodystrophy:
Late Infantile Form
This form has its onset at 12 to 18 months of age,
with progressive weakness of the lower limbs. The gait is abnormal because of spasticity and ataxia
or hypotonia due to peripheral
neuropathy. There is progressive visual loss and optic atrophy. Occasionally, macular degeneration and a "cherry-red
spot" appearance occur. Progressive dementia, loss of speech, ataxia, spasticity and tremors are seen.
Seizures occur in about 50 percent of cases. The condition progresses to severe
dementia, blindness, and spastic tetraplegia, with
decerebration in the terminal stages. Death occurs 2 to 10 years after onset.
Table 14-5
Disorders of sphingomyelin
metabolism
Disease |
Inheritance |
Enzyme deficiency |
Metabolite that accumulates |
Metachromatic leukodystrophy |
Autosomal recessive |
Sulfatidase |
Sulfatide |
Globoid cell leukodystrophy (Krabbe) |
Autosomal recessive |
Galactocerebroside-β-galactosidase |
Galactocerebroside |
GM1 gangliosidoses (generalized) |
Autosomal recessive |
Ganglioside GM^ /3-galactosidase |
Ganglioside GM1 |
Tay-Sachs disease (infantile) |
Autosomal recessive |
Hexosaminidase A |
Ganglioside GM2 |
Tay-Sachs disease (juvenile) |
Autosomal recessive |
Hexosaminidase B |
Ganglioside GM2 |
Tay-Sachs disease (Sandhoff-Jatzkewitz) |
Autosomal recessive |
Hexosaminidase
A, B |
Ganglioside GM2 |
Fabry disease |
X-linked recessive |
Ceramidetrihexoside-α-galactosidase |
Ceramidetrihexoside |
Gaucher disease |
Autosomal recessive |
Glycocerebroside β-galactosidase |
Glucocerebroside |
Niemann-Pick disease |
Autosomal recessive |
Sphingomyelinase |
Sphingomyelin |
Juvenile Form
In this form, symptoms do not appear until 5 to 10 years
of age. The initial symptoms consist of a declining performance in school,
behavioral changes, and gait disturbance. Older children show cognitive decline
and abnormal behavior before the gait is affected. The early symptoms are
followed by progressive spasticity, rigidity,
and ataxia with a somewhat slower
progression than the late infantile form of the disease. Peripheral neuropathy
may develop but is usually mild. Seizures occur in 80 percent of patients.
Life expectancy is 3 to 15 years from time of onset.
Adult Form
Symptoms begin in the early twenties with mental
deterioration and behavior abnormalities, followed by ataxia. The disease is slowly progressive, with the development of
dementia and polyneuropathy progressing
to death after several years. Psychiatric illness with psychosis, personality
change, emotional lability, abnormal behavior, and dementia occur in the late
teens. Neurological find ings are similar to the younger onset types but evolve
slowly. The course is prolonged, with eventually profound dementia, but
survival into the fifth or sixth decades is possible. An adult pseudodeficiency
of arylsulfatase A, with progressive neurological and psychiatric symptoms, has
been described, in which arylsulfatase A levels are low, but there is no accumulation
of sulfatides in the nervous system or in other organs.
Diagnostic Procedures
1. Metachromatic bodies can be seen in frozen sections
of the sural nerve after biopsy.
2. Metachromatic bodies or abnormal urinary lipids can be demonstrated in the urine.
3. A deficiency
of arylsulfatase A can be demonstrated in the urine and leukocytes and in
cultured skin fibroblasts.
4. Visual, brainstem, auditory, and somatosensory evoked responses are abnormally
prolonged or absent.
5. Peripheral
nerve conduction velocities are slowed to less than 30 m/s.
6. The MRI scan
shows cortical atrophy, ventricular enlargement, and abnormal signal intensity
in the periventricular white matter on T2-weighted
images. CT scanning shows scattered areas of decreased attenuation in the
central white matter or decreased white matter attenuation near the frontal and
occipital horns.
7. The CSF
protein is elevated in 90 percent of patients, sometimes greater than 2000
mg/dL.
8. The
diagnosis should be confirmed by leukocytic
genomic DNA analysis.
9. Prenatal
diagnosis is possible by demonstrating lack of arylsulfatase A in the amniotic fluid.
Treatment A
bone marrow transplant may slow the progression of the disease in some patients
with the infantile form of the disease, but treatment is usually symptomatic.
Globoid Cell Leukodystrophy
Definition
Globoid cell
leukodystrophy is a rare demyelinating disorder
of the central and peripheral nervous systems in which there is a deficiency
of the lysosomal enzyme
galactosylceramide-P-galacto-side. The disorder is inherited as an autosomal recessive trait that maps to
chromosome 14q31.
Etiology and Pathology
The deficiency of the enzyme leads to an abnormal accumulation of galactosyl sphingosine, which is cytotoxic to oligodendrocytes
resulting in impaired myelin formation
in the brain (see Table 14-5). The brain is small and there is a diffuse loss
of myelin. Microscopic examination shows
the presence of multinucleated histiocyte
(globoid) cells in the white matter. The globoid
cells contain galactosyl sphingosine.
The cortex remains remarkably normal in appearance, despite isolation from subcortical centers and loss of
interhemispheric connections.
Clinical Features
Globoid cell
leukodystrophy usually occurs in the
infantile form. Rare juvenile and adult variants have been described. In the
infantile form, there is loss of ability to sit, hold up the head, and
reach other developmental milestones. Hyperirritability, hyperesthesia, and episodic fever occur. There
are gradual development of optic atrophy, deafness, and progression to hypotonic or spastic quadriparesis. Seizures
may occur. Terminal decere-bration and death occur within a year of onset.
Diagnostic Procedures
1. There is
diminished activity of the enzyme galac-tosylceramide-3-galactosides in
leukocytes or cultured fibroblasts.
2. The MRI scan
shows areas of increased signal intensity in T2-weighted images in the white
matter of the cerebral hemispheres and cerebellum and occasionally in the thalamus and posterior limb of the internal
capsule and corona radiata.
3. The CT scan
will show areas of low attenuation in the white matter in similar areas.
4. Nerve
conduction velocities are slowed.
5. The CSF
protein may be elevated.
6. Antenatal
diagnosis can be made by amniocentesis and
demonstration of deficient galactosylceramide-β-galactoside in cultured amniotic fluid cells.
Treatment
Treatment is symptomatic.
Adrenoleukodystrophy
Definition
Adrenoleukodystrophy is a sex-linked recessive
disorder owing to a mutation of a gene located in Xq28 that encodes a peroxisomal transporter protein of unknown
function. The disorder is characterized by degeneration of myelin and adrenal insufficiency.
Etiology
and Pathology
The etiology is unknown. There is accumulation of
very long chain fatty acids, particularly hexacosanoate in the tissues. There
is symmetrical demyelination of the cerebrum, brainstem,
cerebellum and spinal cord. Microscopic examination shows sudanophilic lipids within macrophages
lying in the perivascular spaces
of the white matter. The adrenal glands are atrophic
and contain balloon cells with eccentric nuclei.
Clinical
Features The
disease presents in three forms:
Diagnostic
Procedures
1. Elevated
plasma concentrations of long chain fatty acids can be demonstrated in some,
but not all, cases of adrenoleukodystrophy.
2. An MRI scan
shows diffuse areas of increased signal intensity in the white matter cerebrum
and spinal cord. They appear as areas of decreased attenuation in the CT scan.
3. An EMG and nerve
conduction studies are compatible with a primary axonal degeneration in peripheral nerves.124
4. The EEG shows
symmetrical slowing that increases
as the disease progresses.
5. The corticotropin infusion test is abnormal, indicating
primary adrenal insufficiency.
6. The CSF
protein content may be elevated.
7. Adrenocortical biopsy will reveal the
characteristic balloon cells and establish the diagnosis.
Cerebral Form
This is the most common phenotype, occurring in 45
percent of cases and presenting in boys aged 5 to 12 years. There is progressive
failure of academic achievement in school, followed by progressive
deterioration of vision. Ataxia and spasticity develop, and seizures may occur.
There is deterioration to decorticate and decerebrate
states. Death occurs 1 to 4 years after onset.
Adrenomyeloneuropathy
Some 35 percent of cases of adrenoleukodystrophy
present as adrenomyeloneuropathy, which occurs in young adults and involves
the spinal cord and peripheral nerves. Symptoms consist of progressive spastic
paraparesis, peripheral sensory loss
compatible with a peripheral neuropathy, and impaired function of the adrenal
cortex and testes.123
Leukodystrophy with Diffuse Rosenthal Fiber
Formation (Alexander Disease)
Definition Leukodystrophy with
diffuse Rosenthal fiber formation is a
sex-linked recessive disorder characterized by demyelination and progressive
deterioration.
Etiology and Pathology
The etiology is unknown. Rosenthal fibers
are inclusion bodies within the astrocytes in
which stress protein inclusions consisting of a-B-crystallin and small heat
shock protein, HSP-27, are formed as part of a chronic stress response to an
unknown stimulus. The brain is normal in size or enlarged. There is diffuse
demyelination, occasionally accompanied by cavitation,
with proliferation of astrocytes containing
granular eosinophilic deposits within astrocytic processes and cell bodies.
Clinical Features There are three clinical forms of presentation of this disorder.
Infantile Onset
This form occurs in boys and is characterized by
progressive psychomotor retardation, spasticity, megalocephaly, and seizures at approximately
6 months of age. Death occurs by age 3.
Juvenile Onset
This form of the disorder occurs equally in boys and
girls; it begins in late childhood and is characterized by progressive paresis,
bulbar signs, and hyperreflexia. The
patient dies in the late teens.
Adult Onset
The adult-onset form may resemble multiple sclerosis130
presenting with a remittent course with ataxia,
nystagmus, and spastic paraparesis or
quadriparesis.
Sensory symptoms are not significant in any of the
clinical presentations.
Diagnostic Procedures
The diagnosis is established by brain biopsy or autopsy, with demonstration
of a profusion of refractile Rosenthal fibers
within astrocytes.
Treatment
Treatment is symptomatic.
Spongy Degeneration (Canavan)
Spongy degeneration is an autosomal recessive disorder that occurs predominantly in Ashkenazi
Jewish families and is characterized by demyelination and progressive deterioration,
caused by the deficiency of aspartoacy-clase (ASPA). The human ASPA gene has
been localized to chromosome 17.
Clinical Features
The etiology is unknown. There is progressive megalencephaly spasticity and developmental delay. The disease
runs a progressively deteriorating course with death in childhood.
Diagnostic Procedures
1. There are high levels of JV-acetylaspartic acid in the urine, serum, and CSF and absence
of ASPA activity in fibroblasts.
2. The MRI and
CT scans show findings compatible with leukodystrophy.
3. DNA analysis
of amniotic cells is probably a reliable
method for prenatal diagnosis.
4. Screening for
the mutation is warranted among Ashkenazi Jewish couples.
Step I: Aim:
to determine the clinical diagnosis. It is necessary:
1. To
examine the patient (history, somatic-neurological state).
2. To
use the results of the laboratory investigation (general and biochemical blood
and urine analyses, EEG, craniography, tomography).
3. Make
the differential diagnosis using the algorithm.
Step II.
To prescribe treatment. It is necessary to use a principle of the pathogenic correction:
1. treatment of myodysthrophias:
a) diet;
b) drugs – protein remedies, amino acids, vitamins,
macroerges, biostimulators, spasmolytics, ganglioblocators, anticholinesterase
drugs, CAMP-regulators;
c) physiotherapeutic methods – electrophoresis,
massage, remedial gymnastics, mineral wax (ozocerite), bathes;
d) provide facilities in health reports.
2. treatment of Thomson’s myotonia:
a) diet;
b) drugs – quinine in the dose of 0,3 to
c) phonophoresis, faradizations, massage.
3. treatment of myasthenia:
a) drugs – anticholinesterase remedies (Prostigmin,
Mestinon), kalium salts, glucocorticoids, anabolic hormones, immunosuppressive
therapy;
b) surgical treatment: thymectomia;
c) X-ray treatment;
d) the treatment of the crisis is in the “Drug therapy
of the urgent neurological clinical cases”.
4. treatment of paroxysmal myoplegia:
a) if there is a type of hypokaliemia: cilium
chloride, verospirone, amyloride, diet rich of cilium.
b) if there is a type of hyperkaliemia: hypothiazide,
calcium, gluconate, insulin with glucose and kalium free diet.
Step III. Aim:
medical genetic consultation and prevention. Taking on account a heredity type ans
gene’s penetration to estimate a probability of a sick child birth.