Anatomy of the nerves to the lower extremity. (From Goldberg S: Clinical Anatomy Made Ridiculously Simple. Miami, MedMaster, 2002; with permission.)

What is meralgia paresthetica? Commonly found in obese individuals, it is a numbness over the lateral thigh that results from compression of the lateral femoral cutaneous nerve where it runs under the inguinal ligament.

Which nerve supplies the perineum? The pudendal nerve (S2, 3, 4). Parasympathetic branches of S2, 3, 4 supply the bladder and are critical in bladder emptying. Sympathetic fibers to the bladder (from Til to L2) promote retention of urine, but severing of sympathetic fibers to the bladder does not significantly affect bladder function.

SPINAL CORD

Name the five major divisions of the spinal cord. Cervical, thoracic, lumbar, sacral, and coccygeal.

Spinal cord

Where does the spinal cord end? About the level of vertebrae Ll-2. How many nerves exit the spinal cord? There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each spinal nerve is the fusion of a dorsal and ventral nerve root.

What are the coverings (meninges) of the spinal cord? The meninges surround the entire CNS and consist of the pia, which hugs the spinal cord and brain; the arachnoid membrane; and the dura, which is closely adherent to bone.

Where do you find the cauda equina? The cauda equina ("horse's tail") is the downward extension of spinal cord roots at the inferior end of the spinal cord.

MOTOR AND SENSORY PATHWAYS

What are the major motor pathways to the extremities? Corticospinal tract (pyramidal tract): extends from the motor area of the cerebral frontal cortex (Brodmann's areas 4, 6) through the internal capsule, brainstem, and spinal cord, crossing over at the junction between the brainstem and spinal cord at the level of the foramen magnum.

Therefore, lesions to the corticospinal tract above the level of the foramen magnum result in con-tralateral weakness, whereas lesions below the level of the foramen magnum result in ipsilateral weakness.

Rubrospinal tract: connects the red nucleus of the midbrain with the spinal cord Tectospinal tract: connects the tectum of the midbrain with the spinal cord Reticulospinal tract: connects the reticular formation of the brainstem with the spinal cord Vestibulospinal tract: connects the vestibular nuclei of the brainstem with the spinal cord

What distinguishes an upper motor neuron lesion from a lower motor neuron lesion? An upper motor neuron lesion generally refers to an injury to the corticospinal tract. The corticospinal pathway synapses in the anterior horn of the spinal cord just before leaving the cord. A lower motor neuron lesion is an injury to the peripheral motor nerves or their cell bodies in the gray matter of the anterior horn on which the corticospinal tract synapses.

Upper MN Defect Lower MN Defect

Spastic paralysis Flaccid paralysis

No significant muscle atrophy Significant atrophy

No fasciculations or fibrillations Fasciculations and fibrillations present

Hyperreflexia Hyporeflexia

Babinski reflex may be present Babinski reflex not present

How do the effects of corticospinal tract injuries differ from those of cerebellar and basal ganglia injuries? All of the injuries produce motor problems. Corticospinal tract injuries cause paralysis. Cerebellar injuries are characterized by awkwardness of movement (ataxia), not paralysis. The awkwardness is on intention—i.e., at rest, the patient shows no problem, but ataxia becomes noticeable when the patient attempts a motor action. There may be awkwardness of posture and gait, poor coordination of movement, dysmetria, dysdiadochokinesia, scanning speech, decreased tendon reflexes on the affected side, asthenia, tremor, and nystagmus. Basal ganglia disorders, like cerebellar disorders, are characterized by awkward movements rather than paralysis. The movement disorder, however, is present at rest, including such problems as parkinsonian tremor, chorea, athetosis, and hemiballismus.

Name three major sensory pathways in the spinal cord.

1. Pain-temperature—spinothalamic tract

2. Proprioception-stereognosis*—posterior columns (*Proprioception is the ability to tell, with the eyes closed, if a joint is flexed or extended. Stereognosis is the ability to identify, with the eyes closed, an object placed in one's hand.)

3. Light touch—spinothalamic tract and posterior columns

BRAIN STEM AND CRANIAL NERVES

Name the three parts of the brain stem. Midbrain (most superior), pons, and medulla (most inferior).

Functions of the cranial nerves.

CN1 (olfactory): smell

CN2 (optic): sight

CN3 (oculomotor): constricts pupils, accommodates, moves eyes

CN4 (trochlear), CN6 (abducens): move eyes

CN5 (trigeminal): chews, feels front of head

CN7 (facial): moves face, taste, salivation, crying

CN8 (vestibulocochlear): hearing, regulates balance

CN9 (glossopharyngeal): taste, salivation, swallowing, monitors carotid body and sinus

CN10 (vagus): taste, swallowing, lifts palate; communication to and from thoracoabdominal viscera to the splenic flexure of the colon

CN11 (accessory): turns head, lifts shoulders

CN12 (hypoglossal): moves tongue

It is Homer's syndrome. Horner's syndrome is ptosis, miosis, and anhydrosis (lack of sweating) from a lesion of the sympathetic pathway to the face. The lesion may lie within the brainstem or the superior cervical ganglion or its sympathetic extensions to the head.

Which cranial nerves exit from the three parts of the brainstem? Midbrain—CN3, CN4 Pons—CN5, CN6, CN7, CN8 Medulla—part of CN7 and CN8, CN9, CN10, CN12

CN11 exits from the upper cervical cord, goes through the foramen magnum, touches CNs 9 and 10, and then returns to the neck via the jugular foramen. The optic nerve lies superior to the brain stem. The olfactory nerve lies in the cribriform plate of the ethmoid bone.

What CNS areas connect with the brain stem? The midbrain connects with the diencephalon above. The medulla connects with the spinal cord below. Each section of the brain stem has two major connections (right and left) with the cerebellum: two superior cerebellar peduncles connect with the midbrain, two middle cerebellar peduncles connect with the pons, and two inferior cerebellar peduncles connect with the medulla.

What are the two pigmented areas of the brain stem? The substantia nigra, which lies in the midbrain, and the locus coeruleus, which lies in the pons.

What is the red nucleus? The red nucleus lies in the midbrain. It receives major output from the cerebellum via the superior cerebellar peduncle. It has major connections to the cerebral cortex as well as to the spinal cord via the rubrospinal tract.

What is the medial longitudinal fasciculus (MLF)? The MLF is a pathway that runs through the brain stem and interconnects the ocular nuclei of CNs 3,4, and 6 and the vestibular nuclei. It plays an important role in coordinating eye movements with head and truncal posture.

What is the Edinger-Westphal nucleus? It is the parasympathetic nucleus of the third cranial nerve in the midbrain. It supplies motor fibers responsible for pupillary constriction and lens accommodation.

What is an Argyll-Robertson pupil? One of the classic signs of tertiary syphilis. The pupil constricts on accommodating but does not constrict to light. The lesion is believed to be in the midbrain.

Describe the pathway for vision. Optic nerve fibers extend from the retina to the optic nerve, to the optic chiasm, to the optic tract, to the lateral geniculate body, and to the visual area of the brain via the optic radiation. Optic radiation fibers that extend through the parietal lobe end up superior to the calcarine fissure in the occipital lobe. Optic radiation fibers that extend through the temporal lobe end up inferior to the calcarine fissure in the occipital lobe.

What causes a left homonymous hemianopsia? Bitemporal hemianopsia? Superior quadrantanopsia?

Left homonymous hemianopsia: a lesion to the right optic tract, right lateral geniculate body, right optic radiation, or right occipital lobe.

Bitemporal hemianopsia: a lesion to the optic chiasm, generally from a pituitary tumor.

Superior quadrantanopsia: a lesion in the inferior aspect of the optic radiation.

What is most peculiar about the exit point of CN4 from the brain stem? CN4 is the only cranial nerve to exit on the posterior side of the brain stem. In addition, it crosses over the midline before continuing on its course.

If a child has a head tilt, how do you know if it is due to a CN4 palsy or a stiff neck? Cover one eye. If the head straightens out, then the tilt is due to a CN4 palsy. The child tilts the head in a CN4 palsy to avoid double vision. Covering one eye eliminates double vision, so the head straightens out.

Which CNs exit at the pontomedullary junction? CN6 exits by the midline; CNs 7 and 8 exit laterally.

Where do the motor and sensory branches of CNS exit the brain stem? Both exit the brain stem at the same point, in the lateral aspect of the pons.

What are the sensory branches of CNS?

VI—ophthalmic

V2—maxillary

V3—mandibular

Which cranial nerve nucleus extends through all sections of the brain stem? The trigeminal sensory nucleus. Its mesencephalic nucleus (facial proprioception) lies in the midbrain. Its main nucleus (facial light touch) lies in the pons. Its spinal nucleus (facial pain/temperature) lies in the medulla and upper spinal cord.

Cranial nerve nucleus

What is the function of CN 7? CN7 innervates the muscles of facial expression; supplies parasympathetic fibers to the lacrimal, submandibular, and sublingual glands; receives taste information from the anterior two-thirds of the tongue; and receives a minor sensory input from the skin of the external ear.

How does the facial weakness that results from a CN7 lesion differ from that due to a lesion of the facial motor area of the cerebral cortex? A CN7 lesion (as in Bell's palsy of CN7, which occurs in the facial nerve canal) results in ip-silateral facial paralysis, which includes the upper and lower face. A cerebral lesion results in contralateral facial paralysis, confined to the lower face.

What is Mobius syndrome? A congenital absence of both facial nerve nuclei, resulting in bilateral facial paralysis. The abducens nuclei may also be absent.

What are the nucleus ambiguus, nucleus solitarius, and salivatory nucleus? The nucleus ambiguus, which lies in the medulla, is a motor nucleus (CN 9 and 10) that innervates the deep throat, i.e., the muscles of swallowing (CN 9, 10) and speech (CN10).

The nucleus solitarius is a visceral sensory nucleus (CNs 7,9,10) that lies in the medulla. It receives input from the viscera as well as taste information. It is a relay in the gag reflex.

The salivatory nucleus, which contains superior and inferior divisions, innervates the salivary glands (CNs 7 and 9) and lacrimal glands (CN7).

What does CN9 do? CN9, the glossopharyngeal nerve, innervates the stylopharyngeus muscle of the pharynx and the parotid gland. It receives taste information from the posterior one-third of the tongue, sensory tactile input from the posterior one-third of the tongue and the skin around the external ear canal, and sensory input from the carotid body and sinus.

Which side does the tongue deviate to if CN 12 (hypoglossal nerve) is injured? The tongue deviates to the side of the lesion. Imagine you are riding a bicycle and your left hand becomes paralyzed. When you push on the handle bars, the wheel will turn to the left. The genioglossus muscle, which is innervated by CN12 and pushes out the tongue, operates on a similar principle.

CEREBRUM

What does the frontal lobe do? Motor areas of the frontal lobe control voluntary movement on the opposite side of the body, including eye movement. The dominant hemisphere, usually the left, contains Broca's speech area, which when injured results in motor aphasia (language deficit). Areas of the frontal lobe anterior to the motor areas are involved in complex behavioral and executive activities. Lesions here result in changes in judgment, abstract thinking, tactfulness, and foresight.

What does the parietal lobe do? It receives contralateral light touch, proprioceptive, and pain sensory input. Lesions to the dominant hemisphere result in tactile and proprioceptive agnosia (complex receptive disabilities). There may also be confusion in left-right discrimination, disturbances of body image, and apraxia (complex cerebral motor disabilities, caused by cutting off impulses to and from association tracts that interconnect with nearby regions).

What effects do temporal lobe lesions have? Occipital lobe lesions? Temporal lobe lesions in the dominant hemisphere result in auditory aphasia. The patient hears but does not understand. He speaks but makes mistakes unknowingly, due to an inability to understand his own words. Lesions may result in alexia and agraphia (inability to read and write).

Destruction of an occipital lobe causes blindness in the contralateral visual field. Lesions that spare the most-posterior aspect of the occipital lobe do not cause blindness, but cause difficulty in recognizing and identifying objects (visual agnosia). A region of the occipital lobe also controls involuntary eye movements to the contralateral side of the body.

CEREBRAL CIRCULATION

Define the terms anterior and posterior cerebral circulation. The anterior circulation is the distribution of the internal carotid artery to the cerebrum via the anterior and middle cerebral arteries. The posterior circulation is the distribution of the vertebral arteries to the brainstem, cerebellum, and cerebrum via the basilar artery and posterior cerebral artery.

Which brain region is supplied by the anterior cerebral artery? The midline of the cerebrum, specifically the frontal and parietal lobes and the superior portions of the temporal and occipital lobes.

Which brain region is supplied by the middle cerebral artery? The lateral surface of the cerebrum. Specifically, the frontal and parietal lobes and the superior portions of the temporal and occipital lobe (as is the case for the anterior cerebral artery)

Which region is supplied hy the posterior cerebral artery? The medial and lateral surface of the cerebrum. Specifically, the inferior portions of the temporal and occipital lobes.

What is the first branch of the internal carotid artery? The ophthalmic artery.

Where does the brain stem get its blood supply? From the posterior circulation—namely, branches from the vertebral arteries (to the medulla) and branches from the basilar artery (to the pons and midbrain).

What blood vessels supply the cerebellum? The cerebellar blood supply comes from branches of the basilar artery: the superior cerebel-lar, the anterior inferior cerebellar, and the posterior inferior cerebellar arteries.

What is the blood supply of the thalamus and internal capsules? From branches of the circle of Willis, including the lenticulostriate and choroidal arteries.

Which vessels comprise the circle of Willis? The anterior communicating artery, the two anterior cerebral arteries, the two middle cerebral arteries, the two posterior communicating arteries, and the two posterior cerebral arteries.

The circle of Willis. (From Goldberg S: Clinical Neuroanatomy Made Ridiculously Simple. Miami, MedMaster, 2000; With permission.)

Where does the spinal cord derive its blood supply? The anterior spinal artery supplies the anterior two-thirds of the spinal cord. Two posterior spinal arteries supply the posterior third. Also, there are rich anastomoses from branches of the vertebral artery and aorta, so a stroke of the spinal cord is rare.

CEREBROSPINAL FLUID

Cerebrospinal fluid

Where is the CSF produced? It is produced by the choroid plexus, which may be found in the four ventricles of the brain.

How much CSF is produced daily? About 500 ml.

How does the CSF flow through the brain? The CSF flows from the two lateral ventricles (in the cerebral hemispheres), to the single mid-line third ventricle (between the right and left thalamus and hypothalamus), to the single midline fourth ventricle (which overlies the pons and medulla), through the foramina of Magendie and Luschka (in the fourth ventricle), to the subarachnoid space (the space between the pia and arachnoid membranes), which lies outside the brain. CSF leaves the subarachnoid space by filtering through the arachnoid granulations of the superior sagittal sinus, where the CSF joins the venous circulation.

How do communicating and noncommunicating hydrocephalus differ? In hydrocephalus, there is elevated CSF pressure and dilation of the ventricles secondary to obstruction to CSF flow. In communicating hydrocephalus, the obstruction lies outside the ventricular system, beyond the foramina of Magendie and Luschka. In noncommunicating hydrocephalus, obstruction occurs within the ventricular system before the foramina of Magendie and Luschka.

Where is spinal fluid extracted during a spinal tap? From the subarachnoid space between vertebrae L2 and S2. Normally, the fluid is extracted about vertebra level L4-5.

PHYSIOLOGY OF THE PERIPHERAL AND CENTRAL NERVOUS SYSTEMS

As a rehabilitation clinician, why do I need to know about basic neurophysiology? Rehabilitation assesses function and treats disability. Because the lost function of many disabilities is a result of structural or physiologic impairment, all rehabilitation clinicians must have a basic understanding of normal anatomy and physiology. The more one understands about normal physiology and the pathophysiology of the nervous system, the better one can appreciate the neurophysiologic mechanisms of disability and adaptation and the better one can be prepared to develop strategies for treating the disability. In Mountcastle's famous words, "Physiology is what transforms structure into action."

Name the basic elements of the neuron.

Neuron

A typical vertebrate neuron gives rise to tow types of processes: dendrites and axons. The dendrite receives stimulatory input from other nerve cells and carries that input to the cell body. The axon is the transmission process that carries action potentials to points distant from the cell body. The action potential that travels down the axon is initiated at the axon hillock. Each neuron may communicate with up to 1000 other neurons through contact via synapses.

What is the basic function of the neuron? Neurons come in many different shapes and configurations, but their basic function is to integrate activity impinging on the neuron and transmit this information from one place to another. Some neurons function primarily as processing elements in a network (e.g., the interneurons in the spinal cord gray matter), while others conduct information from one place to another along a long cylindrical cellular projection called the axon (e.g., corticomotorneurons projecting into the corticospinal tract).

How do neurons integrate and transmit information? Via chemicals that are released at the synapses. These chemicals, called neurotransmitters, either excite the postsynaptic neuron by depolarizing its membrane and thus creating an excitatory postsynaptic potential, or inhibit the neuron by hyperpolarizing the membrane and thus producing an inhibitory postsynaptic potential. Any particular neuron is constantly bombarded through the synaptic inputs to its dendritic tree by both excitatory and inhibitory influences, which are integrated and then control the overall state of excitation of the neuron, determining when and how frequently it will become excited enough to generate an action potential. That action potential can then be conducted along the neuron's axon to other neurons via synaptic junctions. This continual, dynamic process of integration of inputs by the neuron is the basis of computation within the nervous system. All the "action" that takes place in the neuron occurs at its membrane and involves transient local changes in the electrical properties of the nerve cell membrane, or neurolemma.

Explain what is meant by resting membrane potential. All cellular membranes have ATP-dependent ion-exchange pumps that are used to control the movement of sodium and potassium ions between the intracellular and extracellular spaces. The electrical voltage in the intracellular space of all cells, by virtue of the high intracellular concentration of nondiffusable anions together with the action of the ion-exchange pump, is relatively negative (by just under 100 mV) compared to the extracellular space. The membrane is thus said to be "polarized," with its inside surface being relatively negative at rest compared to its outside surface. This is an important fact since all excitable tissue phenomena in muscle and nerve cells assume a resting membrane potential that keeps the excitable cell quiescent in the presence of a lack of excitation. However, this is not really a "resting" condition since it is actively maintained.

What is an ectopic membrane potential? Any problem with the membrane-based ion-exchange pump or the relative permeability of the membrane to any of the major ionic species can result in a major fluctuation of the resting membrane potential in nerve and muscle fibers. This fluctuation can lead to unconstrained depolarization of the membrane to the threshold level, resulting in spontaneous excitation and discharge of the membrane with the production of an aberrant, or ectopic, action potential. This is one of the main physiologic ways that excitable cells respond to pathologic conditions and is the basis for ectopic discharge in excitable tissues, producing such phenomena as muscle fiber fibrillation and motor unit fasciculation.

How does the voltage-dependent ion channel work in this system? In neuronal and muscle membrane (the neurolemma and sarcolemma, respectively), voltage-dependent ion channels, primarily for sodium and potassium, pop open transiently when the intracellular voltage drifts positive (i.e., the membrane depolarizes). At the threshold voltage, an explosive electrochemical process is initiated in which voltage-dependent sodium channels open in rapidly increasing numbers, and the transmembrane voltage rises sharply as sodium ions rush into the cell from higher concentration in the extracellular space to lower concentration in the intracellular space, producing a further rise in intracellular voltage and further depolarization of the cell membrane. This regenerative explosion is the basis of the sharp upswing of the nerve action potential. The voltage eventually levels off as the sodium channels become less sensitive (i.e., less likely to open) to the increased voltage and as voltage-dependent potassium channels open allowing potassium to move out of the cell. The transmembrane voltage reverses, dropping toward the resting level. It actually overshoots the resting level, and the membrane becomes hyper-polarized for a short period called the refractory period, during which it is resistant to excitation.

Discuss the role of membrane refractoriness in conducting action potentials. Postexcitatory refractoriness is a critical aspect of neural network dynamics that helps to constrain the excitatory phenomena in the nervous system. The duration of the refractory period determines how quickly a nerve can be repetitively excited and restricts the effective "bandwidth," or information-carrying capacity, of the neuron. This refractory mechanism produces an asymmetry of excitability around the area of depolarized membrane conducting the action potential. The membrane in front of the action potential remains excitable and ready to "fire up," while the membrane behind the action potential becomes transiently inexcitable and resistant to rebounding excitatory influence. This asymmetry prevents "backfiring" of the cell membrane and ensures that the action potential travels as a wave in one direction down the length of the fiber.

Where do calcium ions operate in the action potential? A transient "spike" of membrane depolarization is conducted from the cell body of the neuron down the axon as a wave of excitation. When it reaches the distal end of the axon at the presynaptic terminal, the depolarization spike initiates the flow of calcium ions into the presy-naptic terminal through voltage-dependent calcium channels concentrated in the membrane of the presynaptic terminal. This leads to release of neurotransmitter from the presynaptic terminal, leading to excitation or inhibition of the postsynaptic cell.

What are fibrillation and fasciculation? In the mature neuromuscular system, a muscle fiber should normally generate an action potential and contract only when "it is told to" by a motor neuron. However, in muscle fibers with defective membranes that "leak" sodium ions from the extracellular to the intracellular space, spontaneous membrane depolarization leads to the spontaneous generation of a muscle fiber action potential and the autonomous contraction of the fiber. This autonomous contraction of a muscle fiber occurs in the presence of pathologic conditions that either remove the normal neural control over the muscle fiber or directly damage the muscle fiber membrane. This pathologic autonomous muscle fiber contraction is called a fibrillation, an invisible tiny twitch of an individual muscle fiber.

A similar type of electrical destabilization of the membrane of the motor neuron and motor axon leads to spontaneous generation of an ectopic nerve action potential, which is conducted through the terminal branching of the fiber to all muscle fibers innervated by the motor neuron. This results in a synchronous autonomous contraction of all the fibers in the motor unit, producing a significant, visible twitch of the muscle called a fasciculation. Both phenomena are physiologic results of the loss of normal constraint over the excitation of nerve and muscle fibers that can occur in various neuromuscular disorders.

What is a neural network? What does it do? A neural network is a set of neurons that are interconnected in a specified pattern. Through the conduction of activity from one place to another within the network and through the convergence and divergence of activity in different parts of the network as it is dynamically active, patterns of activation emerge. A network may be considered to have a set of inputs impinging on input neurons, a set of outputs generated by output neurons, as well as a set of neurons that mediate activity back and forth between input and output neurons. The general structure of a neural network includes input neurons that convey afferent (i.e., in-flowing) information from the periphery and output neurons that convey efferent (i.e., out-flowing) information to the periphery. These two general flows of information can interact at multiple levels, allowing an efferent flow to modulate an afferent flow and an afferent flow to modulate an efferent flow. These interactions help control what moves along the pathway from the periphery to more central structures to eventually enable perception to occur, and what moves along the pathway from central structures to the periphery to generate movement.

What is muscular co-contraction and what does it accomplish? High-force output motor units cannot be immediately accessed but can only be recruited after low-force output motor units have first been activated. To obtain the rapid deployment of a large amount of force, the muscle may need to be "preloaded" so that it is already operating up in the range in which the high-force output units are starting to be recruited. Agonist-antagonist muscle groups will sometimes oppose each other in a co-contraction in order to "bias" a muscle into its higher output range, which enables more immediate access to the large-amplitude, fast-fatigable motor units and facilitates rapid production of large bursts of muscular force.

Muscle co-contraction is also important for the stabilization of proximal joints during more distal movement and also for situations in which forces across a joint must be absorbed through muscle contraction. Co-contraction is also used to stabilize a limb in anticipation of a dynamic load whose exact direction of force cannot be predicted.

On the other hand, in many gross motor activities, gravity acts as a sustained force that serves as the primary propulsive force, which is then controlled by low-grade, sustained, eccentric muscle contractions. In this case, the muscles operate in their low range where the slow-ox-idative, low-amplitude units predominate and co-contraction just adds an unnecessary and wasteful burden. In such instances, agonist-antagonist interaction is controlled with patterns of reciprocal inhibition that produce a "push-pull" alternating interaction between muscles to produce opposing forces. Mechanisms for controlling the interaction of agonist-antagonist pairs of muscles in either co-contraction or reciprocal inhibition relationships are programmed to a great extent at the spinal segmental level.

How does a muscle fiber contract? A twitch of mechanical energy is produced through the transient shortening of a muscle fiber whenever an action potential travels along the sarcolemma (i.e., muscle fiber cell membrane).

The actual shortening of muscle is produced by the coordinated, relative movement of thin (actin) and thick (myosin) filaments within the myofibrils (see figure). Two factors are necessary for the contraction to develop: a supply of high-energy phosphate bonds for metabolic support of contraction (usually provided by ATP) and a supply of calcium ions. The movement is driven by cross-bridge molecules originating in the thick filaments and bridging across to the thin filaments. The binding of ATP to a cross-bridge causes it to release its contact with the actin-binding site on the thin filament. The ATP then splits, forming a high-energy state of the crossbridge which extends and binds itself to another binding site on the thin filament. The cross-bridge moves from a high-energy state to a low-energy state in the process of bending and shortening, thus moving the thin filament in toward the center of the thick filament and drawing the Z lines on the sarcomeres closer together. A new ATP molecule then must bind to the cross-bridge in order to facilitate its dissociation from the binding site on the thin filament. The dissociated cross-bridge is then cocked and ready to attach to another binding site on the thin filament. This cycle repeats itself over and over as long as there is ATP present to drive the process.

What role does calcium play in muscle contraction? The forming of a cross-bridge can only occur when there are receptor-binding sites available on the thin filament for the cross-bridge to attach. In the presence of calcium ions, there is a conformational change in the thin filament that exposes the binding sites. When calcium is not present in the myofibril, contraction cannot occur because the binding sites are retracted. Thus, control of the contractile process reduces to controlling the concentration of calcium ions in the myofibril. The spreading excitation of the muscle fiber causes a release of calcium into the myofibril through voltage-dependent calcium channels that open in the membranes of the sar-coplasmic reticulum as the wave of depolarization spreads down the fiber. Calcium ions flow into the myofibril and activate the contractile process. Calcium ions are then rapidly and efficiently pumped out of the myofibril and back into the sarcoplasmic reticulum as the muscle fiber relaxes.

This then is the basic process whereby the electrical phenomenon of transmitted membrane depolarization along the length of a muscle fiber is transformed into the mechanical phenomenon of muscle fiber shortening and muscle contraction.

Outline the sequence of events in muscular contraction.

Excitation-contraction coupling

1. Depolarization of sarcolemma with conduction of muscle fiber action potential

2. Internal fiber depolarization through transmission along T-tubule system

3. Release of Ca²⁺ from sarcoplasmic reticulum

4. Ca²⁺ diffuses into sarcomeres

Contraction

5. Ca²⁺ binds to troponin

6. Troponin-Ca²⁺ complex removes tropomyosin blockage of actin-binding sites

7. Myosin heads containing high-energy myosin-ADP-P_z. complex attach to actin-binding sites and form cross-bridges between thick and thin filaments

8. Conformational energy-releasing changes occur in high-energy myosin heads that cause them to swivel, producing relative motion of the thick and thin filaments, releasing ADP and P. and returning the myosin head to its low-energy state

9. A new ATP molecule binds to the myosin head, allowing the release of the head from the actin-binding site

10. ATP splits to ADP and P_r producing a high-energy myosin-ADP-P. complex

11. Return to Step 7 with repeating of cycle of steps 7-10 as long as actin-binding sites remain available for attachment

Relaxation

12. Ca²⁺ pumped back into sarcoplasmic reticulum

13. Ca²⁺ around thin filaments diffuses back toward the sarcoplasmic reticulum

14. Ca²⁺released from troponin-Ca²⁺complex

15. Troponin permits return of tropomyosin to blocking position

16. Myosin-actin cross-bridges break with addition of ATP to the myosin head, but new cross-bridges cannot form because the actin-binding sites are no longer available because of blocking action of tropomyosin

What is spasticity? Describe its neurophysiologic basis. Spasticity is most often used to refer to abnormalities of movement in a limb in which there has been damage to centers that modulate the activity of the motor unit. A number of things go wrong with motor control and the process of voluntary activation of the motor units when centers above the level of the spinal segment are damaged. When motor control is dysfunctional, events can be viewed as "negative" phenomena, where activity that should normally be present is not or where normal activity patterns become abnormally attenuated, of "positive" phenomena, where activity patterns that are normally not present appear (e.g., pathologic reflex patterns) or where activity patterns that are normally present become abnormally exaggerated and distorted.

List the six major descending tracts from the brain.

The circuits in the spinal cord at the segmental level are controlled by descending tracts from the brain.

1. Corticospinal tract (including lateral and ventral tracts) projecting from the cerebral cortex

2. Vestibulospinal tract projecting from the vestibular nuclei in the pons

3. Medial reticulospinal tract projecting from the pontine reticular formation

4. Lateral reticulospinal tract projecting from the medullary reticular formation

5. Rubrospinal tract projecting from the red nucleus in the midbrain

6. Tectospinal tract projecting from the superior colliculus in the tectum of the midbrain

How do each of the different descending tracts affect muscle tone? Each of the descending pathways has a different influence on the background tone and dynamic activation of motor neuron pools and interneuronal circuits in the spinal cord.

The vestibulospinal and reticulospinal tracts are involved in the postural biasing of muscles and anticipatory postural adjustments that precede voluntary movements. The vestibulospinal and reticulospinal output neurons are generally excitatory to extensor motor neurons innervating extensor muscles in the arms and legs and are under inhibitory control from the cortical level. The loss of cortical inhibitory control over these pathways tends to facilitate extensor tone in the arms and legs, resulting in decerebrate rigidity.

The rubrospinal and corticospinal tracts both tend to balance the extensor drive by facilitating drive to flexor muscles. The rubrospinal tract in humans extends only into the cervical cord and thus can counteract extensor drive in the arms but not the legs. Thus, the decorticate rigidity in humans with large cerebral hemisphere lesions is primarily one of net facilitation of flexors in the arms and extensors in the legs. This is because loss of descending control from the cerebral cortex releases unopposed excitatory extensor drive from the vestibular and reticular formation areas to the lower limb extensor muscles, while flexor facilitation is released from the red nucleus to upper limb flexor muscles in projections in the rubrospinal tract.

What is the upper motor neuron syndrome? When there is dysfunction of the descending inputs to the spinal cord, there is a degrading of the dynamic control of the motor neurons, and the patterns of activation of muscles in a limb that form the basis of normal limb function become disordered. This combination of findings— changes in response to passive sustained and dynamic stretch, disinhibition of antigravity postural subroutines, and disordering of voluntary patterns of muscle activation—depends on the exact way in which the descending pathways have been affected by the damage. This combination of changes can be thought of as a type of disordered motor control or as a syndrome, the upper motor neuron syndrome (UMNS), where the term "upper motor neuron" refers to any neuron in the central neuraxis which projects down to the spinal cord through one of the descending pathways.

The disorder of function associated with UMNS may be due to a wide variety of possible mechanisms, which could include altered response (usually exaggerated excitation) to passive stretch, an inability to generate voluntary activation of a muscle (i.e., decreased drive), or an inability to dynamically coordinate the activation of a set of different muscles in the limb. Additionally, over time in the paretic limb, there are changes in the fibrous architecture of the muscle that lead to changes in the passive viscoelastic properties of the muscle of an affected limb. Thus limitation of movement in chronic UMNS may be due to fixed contracture or may be exaggerated by a loss of distensibility of the fibrous matrix of the muscle.

What parts of the nervous system are involved in the control of voluntary movement? The motor cortex is the cortical strip of the precentral gyrus. It is a somatotopically organized, electrically excitable region of the cerebral cortex that is involved in the execution of detailed aspects of voluntary fine movement, especially rapid, finely coordinated, "fractionated" movements of the fingers and toes.

Areas in the parietal cortex and frontal cortex (in the "premotor" cortex) are involved in translating the intent to act into more global aspects of the task, such as its timing, sequential linkage of different subtasks, trajectory through extrapersonal space, and coordination of the postural stabilization and distal limb control in movement.

Muscle contraction

and movement

Sensory consequences of movement

Levels of organization of the motor system.

The cerebellum receives two inputs and has one output. This input, from the cerebral cortex and from the spinal cord, keeps the cerebellum informed about what is going on in the limbs, particularly with muscle and tendon stretch information. The cerebellum generates output back to the cerebral cortex that can then influence the ongoing outflow of activity from the cortex. There is thus a circular loop involved in cerebellar circuitry, called a re-entrant loop, since the output re-enters the general part of the nervous system (the cerebral cortex) from which input originated.

The basal ganglia consist of the striatum (the caudate and putamen nuclei), the pallidal nuclei (the external and internal segments of the globus pallidus), and a set of nuclei in the mid-brain including the substantia nigra and subthalamic nucleus. The basal ganglia constitute a second, but differently connected, re-entrant loop with the cerebral cortex. Both the cerebellum and the basal ganglia reconnect to the cerebral cortex by way of distinct thalamic nuclei in the ventral region of the thalamus.

What is the role of the cerebellum in the control of voluntary movement?

The cerebellum is an important "meta-system" in voluntary motor control that enables the refinement and fine-tuning of motor performance through dynamic modulation of outflows from the motor cortex. This is done by correcting errors detected between the sampled outflow from the motor cortex, which conveys the details of the intended movement, and the sensory input from the periphery, which conveys the details of the actual movement.

The cerebellum can be viewed as being responsible for the discrete timing relationships within a pattern of muscle activations and may have some type of dynamic clocking function. The cerebellum rapidly performs precise adjustments of the dynamics of the sensorimotor linkage and muscle activation patterns to allow for progressively more rapid and accurate performance of a motor task as it is being practiced. As such, the cerebellum is an important site for motor learning and for the development of procedural memories (i.e., motor engrams). The automatization of motor skill performance frees up the cerebral cortex from the attentional load involved in taking care of all the details of execution.

What motor dysfunction is associated with cerebellar damage?

Deficient movement execution and coordination with the appearance of oscillations (ataxic tremor), inaccurate endpoint acquisition (past-pointing), and impairment of the timing of muscle activation in dynamic alternation and rhythmic movements (dysdiadochokinesis). There is a lack of precision in the timing of activation of bursts of EMG activity in agonist and antagonist muscle pairs, particularly for rapid "ballistic" movements which cannot be controlled with continuous feedback. A delay in the development of the braking effect of the antagonist burst that follows the acceleration produced by the initial agonist burst results in overshoot of the target, or past-pointing. This effect is exaggerated when movement speed increases, since the timing precision demands of the task become more severe. Errors are reduced by slowing down performance of the task and by focusing more attention on performance.

In the presence of cerebellar impairment, patients tend to try to simplify the problem of performing multijoint movements by focusing on the movement of one joint at a time in sequence, rather than attempting to move all joints simultaneously. The cerebellum adjusts stretch reflex gains to allow for appropriate dynamic load compensation necessary, for example, when an unexpected loading of the limb occurs. In the presence of cerebellar damage, load compensation responses are reduced or delayed, the gain of the stretch reflexes is reduced with resulting hypotonia, and the result is*an underdamped limb that is prone to oscillation and overshoot.

What role does the basal ganglia play in voluntary movement? Whereas the cerebellum is involved in the control and coordination of precise timing relationships between bursts of activity in different muscles firing within a pattern, the basal ganglia seem to be involved in the more global control of the timing of the pattern as a whole—i.e., its relative expansion or compression in time. This may be closely related to the clocking of internal ultradian rhythms. The striatum receive widespread input from all over the cerebral cortex, and the output of the globus pallidus goes to a limited area of the thala-mus that interacts with a very limited region of the premotor and supplementary motor areas. The striatum appears to be subdivided into segregated modules, each of which receives inputs from different subregions of the cerebral cortex, suggesting a highly modularized system of re-entrant loops.

The basal ganglia may play a role in selecting specific motor patterns to be chosen from a vast repertoire of potential patterns based on current cortically processed sensory context. This probably occurs through a process of selective facilitation of a small subset of modular loops and massive inhibition of the remaining loops that allows only limited modules of the striatum to be allowed to inhibit regions of the globus pallidus, which then projects inhibitory output to the thal-amus. Thus, the basal ganglia can be viewed as a selective filter of information flow converging on motor preparation regions of the cerebral cortex. They may therefore be involved in the process of selecting motor engrains to be activated in a certain context or setting up critical perceptuomotor linkages.

How does dopaminergic failure in the basal ganglia present clinically? Dysfunction of the dopaminergic system within the basal ganglia results in problems with slowness of movement, impairment of initiation, and overall constriction of movement. Dopamine acts as a promotor and energizer of movement by playing a role in the selective facilitation of specific movements. It may also serve a role as a controlling influence on an internal sense of time. Thus, patients with dopaminergic insufficiency associated with parkinsonism have problems with estimating time intervals and accurately reproducing time intervals presented to them.

Explain the roles of different parts of the cerebral cortex in the planning and control of movement.

The cerebral cortex plays an important role in assuring that movements are integrated, coordinated, and contextually appropriate. Through emerging techniques, such as positron-emission tomography (PET) and functional MRI, that allow the activity of different parts of the brain to be imaged in the active human subject, we are able to learn more about the functional networks in the cerebral cortex that participate in conscious perception and volition.

One theory relates to how different parts of the cerebral cortex have evolved. The medial part of the cortex has evolved from the hippocampus, while the lateral part of the cortex has evolved from the primitive olfactory complex. This suggests that structures on the medial surface of the hemisphere, such as the anterior cingulate cortex and the supplementary motor area, are involved in the initiation and control of movements that are internally based, while the areas on the lateral surface of the brain, such as the ventrolateral frontal lobe and the lateral parietal regions, are involved in the detection and registration of external information and the integration of external cues into action control. In fact, the anterior cingulate cortex on the medial surface of the brain, just above the corpus callosum, appears to be part of an important executive attention network that is associated with conscious volition, while the lateral structures appear to be important elements of a perceptual orienting network and a vigilance network that focuses on external events. The cerebellum appears to be more closely associated with the lateral system, while the basal ganglia are most closely associated with the medial system. These different "premotor" systems, the medial and lateral, appear to relate to each other through reciprocal inhibition. Activation of the anterior circulate region and the executive attention network appears to be associated with the subjective experience of awareness or effort directed to performance—attention for action.

Cerebral cortex

Structure and organization of the medial premotor system (MPS) on the medial surface of the hemisphere and the lateral premotor system (LPS) on the lateral surface of the hemisphere. In the MPS, the supplementary motor area (SMA) and the anterior cingulate cortex (ACC) project in topographically ordered fashion to the primary motor cortex (PMC). These areas are also in close relationship with the basal ganglia (BG). In the LPS, the arcuate premotor area (APA) on the lateral surface of the monkey brain projects similarly to PMC. The cerebellum (Cb) with the cerebellar cortex (CbCtx) and the deep cerebellar nuclei (DCbN) is part of the LPS and projects through the thalamus back to APA and PMC.The cerebellar cortex also receives direct af-ferents from the spinal cord by way of the spinocerebellar tract (SpnCbT). The BG receive input from broadly distributed regions of the cerebral cortex projecting to the striatum and project output back from the globus pallidus to the SMA and ACC via the VA and VLo nuclei of the thalamus. Outflow from the PMC, SMA, ACC, and APA projects to the spinal cord by way of the corticospinal tract (CSpT). Projections to the PMC influence the "gain" of sensorimotor "transcortical loops" that link sensory input to the PMC to the efferent projects from the PMC into the CSpT.

STROKE

How many people suffer a stroke? Who is typically affected? Stroke is a very common clinical problem. Recent estimates have placed the incidence at about 700,000 new strokes per year in the U.S., which is approximately 150,000-200,000/year more than past estimates. It is believed that better epidemiological assessments, rather than a true increase in the number of new strokes, accounts for the recent increase in reported incidence. About 150,000 die each year within 1 month after the stroke, making stroke the third leading cause of death in the U.S. It is estimated that about 4 million people are alive today who sustained a stroke at some time in the past, and a substantial proportion (perhaps one-half to two-thirds) of these survivors have varying degrees and types of neurologic impairments and functional disabilities. Stroke is the second most frequent cause of disability (second only to arthritis), the leading cause of severe disability, and the most common diagnosis among patients on most rehabilitation units.

Men have a 30-80% higher incidence than do women, and African-Americans have a 50-130% greater incidence than do whites. The incidence is age-related, with the rate increasing nine-fold between the ages of 55 and 85. About two-thirds of all stroke patients are over age 65.

RISK FACTORS

MODIFIABLE WITH BEHAVIOR CHANGE

RISK FACTORS MODIFIABLE WITH MEDICAL CARE

UNMODIFIABLE RISK FACTORS

Hypercholesterolemia

Hypertension

Age

Obesity

Diabetes

Gender

Sedentary lifestyle

Heart disease

Race

Cigarette smoking

Transient ischemic attack

Family history

Alcohol abuse

Significant carotid artery stenosis

Cocaine use

History of prior stroke

List the risk factors for stroke.

How can subsequent strokes be prevented in patients who have survived a first stroke?

Risk factor modification

Antiplatelet agents—aspirin, ticlopidine, and clopidogrel

Anticoagulation—warfarin

Carotid endarterectomy

Surgical procedure to correct cerebral aneurysm or arteriovenous malformation.

What is a stroke? A stroke is an acute neurologic dysfunction of vascular origin, with relatively rapid onset, causing focal or sometimes global signs of disturbed cerebral function lasting for > 24 hours.

What are the different types of strokes? Stroke types are generally divided into two broad etiologic categories: ischemic (65-80% of the total) and hemorrhagic (15-25% of the total). The cause of a few strokes (up to 10% of the total) is either unknown or more unusual.

______________TYPE OF STROKE__________% OF THE TOTAL______

Ischemic strokes

Thrombotic brain infarction 45-65%
Embolic brain infarction 10-20%

Hemorrhagic strokes

Intracerebral (intraparenchymal) hemorrhage 5-15%
Subarachnoid hemorrhage 5-10%

Other strokes 0-10%

What are the common impairments caused by stroke and their relative frequencies?

IMPAIRMENT

ACUTE (%)

CHRONIC (%)

Any motor weakness

Right hemiparesis

Left hemiparesis

Bilateral hemiparesis

Ataxia

Hemianopsia

Visuoperceptual deficits

Aphasia

Dysarthria

Sensory deficits

Cognitive deficits

Depression

Bladder incontinence

Dysphagia

What are lacunar strokes? Accounting for about 15% of all strokes, lacunar strokes are caused by small deep infarctions located in the deeper portions of the brain and brainstem, resulting from occlusion of the deep penetrating cerebral arteries. Risk factors for lacunar stroke include hypertension and diabetes. Because the cerebral lesions are small, they usually do not cause severe impairment or disability. Because they are caused by deeper cerebral lesions, they usually do not impair higher cortical functions.

The most common lacunar syndromes are pure motor hemiplegia, hemimotor-hemisensory syndrome, pure sensory stroke, dysarthria-clumsy hand syndrome, and hemiparesis-hemiataxia.

What is locked-in syndrome? Locked-in syndrome is a severely disabling condition, characterized by the combination of complete quadriplegia, facial paralysis, and anarthria. It is caused by interruption of the bilateral corticospinal and corticobulbar tracts that occurs with bilateral infarction of the ventral pons.

What is pseudobulbar palsy? Pseudobulbar palsy is the combination of emotional lability, dysphagia, dysarthria, and hyperactive brainstem reflexes.

Describe the usual course of natural recovery after the onset of hemiplegia. Natural spontaneous recovery of motor function follows a relatively predictable sequence of stereotyped movement events for most (but not all) patients who recover from stroke-induced hemiplegia. The pattern of recovery is most consistent in patients with cerebral infarction in the middle cerebral artery distribution. Lower-extremity function recovers earliest and most completely, followed by upper-extremity and hand function. Tone usually returns before voluntary movement, volitional control over the proximal limb before the distal limb, and mass movement isynergy) patterns before specific isolated coordinated volitional motor functions. Most exceptions to these patterns occur in patients with stroke types other than cerebral infarctions and with lesion locations other than middle cerebral artery distribution.

The relative uniformity of these phases of recovery was first studied and documented systematically by Twitchell in 1951 and later formalized into a series of stages by Brunnstrom in 1970. Describe the features of each of the Brunnstrom stages of motor recovery in hemiplegic patients.

Stage I

Flaccidity

Phasic stretch reflexes absent

No volitional or reflex-induced active movement

Stage II

Spasticity, resistance to passive movement

Basic limb synergy patterns

Associated reactions

Movement patterns stimulated reflexively

Minimal voluntary movement Stage III

Marked spasticity

Semivoluntary

Volitional initiates movement of involved limbs, resulting in synergy

Usually flexion synergy in arm and extension synergy in leg

Stage IV

Spasticity reduced

Synergy patterns still predominant

Some complex movements deviating from synergy

Stage V

Spasticity declines more, but still present with rapid movements

More difficult movement patterns deviating from synergy

Voluntary isolated environmentally specific movements predominate

Stage VI

Spasticity disappearing

Coordination improves to near normal

Individual joint movements possible

Still have abnormal movement and faulty timing during complex actions

Stage VII:

Restoration of normal variety of rapid complex movement patterns with normal timing, coordination, strength, and endurance

Name the components of the limb synergy patterns. Synergy patterns are the stereotyped mass movement patterns that characterize limb activity after injury to the cerebral voluntary motor system. The affected upper and lower extremities each can assume a flexion or an extension synergy pattern. In the following list, the predominant movement in each pattern is marked with an asterisk.

Upper Extremity Flexion Synergy Pattern Upper Extremity Extension Synergy Pattern
Scapular retraction Scapular protraction

Scapular depression Scapular depression

Shoulder external rotation Shoulder internal rotation

Shoulder abduction Shoulder adduction

Forearm pronation Forearm pronation

*Elbow flexion Elbow extension

Wrist flexion Wrist extension

Finger flexion Finger flexion

Lower Extremity Flexion Synergy Pattern Lower Extremity Extension Synergy Pattern

Pelvic protraction Pelvic retraction

Pelvic depression Pelvic elevation

*Hip flexion Hip extension

Hip abduction Hip adduction

Hip external rotation Hip internal rotation

Knee flexion *Knee extension

Ankle dorsiflexion Ankle plantarflexion

Foot inversion Foot inversion

Toe dorsiflexion Toe plantarflexion

Great toe extension Great toe extension

What are the most common causes of death in stroke survivors? During the first month after a stroke, the major causes of death, arranged in order of descending frequency, are:

• The stroke itself, with progressive cerebral edema and herniation

• Pneumonia

• Cardiac disease (myocardial infarction, sudden death arrhythmia, or heart failure)

• Pulmonary embolism

After the first month, cardiac disease is the most common cause and stroke is the second most common cause of death in stroke patients.

How common are venous thromboemolic phenomena in stroke patients? Deep venous thrombosis (DVT) has been reported to occur in 22-73% of stroke survivors, with the best estimates of incidence of 40-50%. The incidence of pulmonary embolism in stroke is about 10-15%. Peak incidence is during the first week after stroke, but the risk of venous thromboembolism persists thereafter. Clinical features of DVT or pulmonary embolism are present in less than one-half of patients with these problems, making laboratory diagnosis necessary for most patients suspected of having these conditions.

Can venous thromboembolic complications be prevented? Because of the high risk of venous thromboembolism, DVT prophylaxis is recommended for all patients with stroke who have muscle weakness and who undergo inpatient rehabilitation. Methods of prophylaxis include repeated doses of low-dose subcutaneous heparin or low-molecular-weight heparin compounds, external pneumatic calf-compression boots, and other physical methods. The optimal duration of prophylaxis is not known, but persistence of severe muscle weakness and lack of ambulatory ability are considered indicators of increased DVT risk.

How common are dysphagia, aspiration, and pneumonia after stroke, and what can be done about them? The incidence of dysphagia in stroke patients is between one-third and one-half. Although dysphagia can be associated with cortical, subcortical, or brain stem lesions, the highest incidence is in patients with brainstem strokes.

One third of stroke patients with dysphagia will have aspiration, defined as entrance of material into the airway below the level of the true vocal folds. Of those who aspirate, 40% will do so silently, without cough or other clinical manifestations of difficulty. Aspiration usually results from disturbances in the pharyngeal phase of swallowing related to reduced laryngeal closure, pharyngeal paresis, or reduced pharyngeal peristalsis. In order to establish the dysphagia diagnosis and aspiration risk, a clinical evaluation of swallowing function and videofluoroscopic swallowing study can be done.

Complications of stroke-induced dysphagia include pneumonia, malnutrition, and dehydration. Pneumonia occurs in about one-third of all stroke patients, and the major cause of pneumonia is dysphagia with aspiration. Other factors that increase the risk of pneumonia are cognitive deficits, inadequate hydration and nutrition, impaired cough and gag reflexes, immobility, and the decreased ability to cough resulting from expiratory muscle weakness, altered chest wall movement patterns, chest wall spasticity, and contracture.

Interventions to treat dysphagia include changes in posture and head position; oral motor exercises for the tongue and lips to increase strength, range of motion, velocity, and precision; use of thickened fluids and soft or pureed foods in smaller boluses; tactile-thermal application of cold stimuli; practice in proper eating techniques; and the use of alternative feeding routes such as nasogastric, gastrostomy, or jejunostomy tubes.

Describe the major bladder problems caused by stroke. What can be done to treat them? The incidence of urinary incontinence is 50-70% during the first month after stroke and about 15% after 6 months, a figure comparable to that in the general population. Incontinence may be caused by the brain damage itself (resulting in an uninhibited spastic neurogenic bladder with a synergic sphincter), urinary tract infection, impaired ability to transfer to the toilet or remove clothing, aphasia, or cognitive-perceptual deficits that result in lack of awareness of bladder fullness. Bowel impaction and some medications may exert an adverse effect. Urinary incontinence can cause skin breakdown, social embarrassment, and depression, and it increases the risk of institutionalization and unfavorable rehabilitation outcomes.

The most important therapeutic approach to the stroke-induced neurogenic bladder is the implementation of a timed bladder-emptying schedule. Other important management strategies include treatment of urinary tract infection, regulation of fluid intake, transfer and dressing skill training, patient and family education, and (rarely) medications.

Urinary retention is less common but can occur in the presence of diabetic autonomic neuropathy or prostatic hypertrophy. Urinary retention may cause urinary tract infections requiring treatment with catheterization, medication, and attention to the primary genitourinary cause.

What is the incidence of bowel dysfunction in stroke? How can it be treated? The incidence of bowel incontinence among stroke patients is 31%. While this problem usually resolves within the first 2 weeks after stroke, persistent bowel incontinence may reflect severe brain damage. Bowel continence may be adversely affected by infection resulting in diarrhea, inability to transfer to the toilet or to manage clothing, or inability to express toileting needs. The more common bowel complications are constipation and impaction, resulting from inactivity, inadequate fluid intake, and psychologic disturbances.

Management of bowel dysfunction emphasizes a timed toileting schedule; use of dietary fiber; adequate fluid intake; use of stool softeners, suppositories, or enemas; training in toilet transfers and communication skills; and judicious use of laxatives.

Explain the motor facilitation approaches frequently used in physical therapy with stroke patients.

Each of the neuromuscular facilitation exercise approaches commonly used in stroke survivors has a neurophysiologic basis and a somewhat unique focus.

The neurodevelopmental treatment method, developed by the Bobaths, is currently the most widely used approach for the treatment of hemiplegia resulting from stroke. This method emphasizes inhibition of abnormal tone, postures, and reflex patterns, while facilitating specific automatic motor responses that will eventually allow the performance of skilled voluntary movements.

The Brunnstrom treatment method uses the reflex tensing and synergistic patterns of hemiplegia to improve motor control through central facilitation.

The Rood method relies on the peripheral input of cutaneous sensory stimulation, in the form of superficial brushing and tapping, to facilitate or inhibit motor activity.

Proprioceptive neuromuscular facilitation, introduced by Kabat and Knott, uses such mechanisms as maximum resistance, quick stretch, and spiral diagonal patterns to facilitate normal movement.

The more recently-developed motor relearning program of Carr and Shepherd emphasizes functional training, practice, and repetition in the performance of specific tasks, and carry-over of those motor skills into functional activities.

Only a few studies have investigated the relative effectiveness of these methods; results are inconconclusive, but no single method has been found to be more effective than any other to improve outcome after stroke. A common clinical practice is to incorporate elements of several methods.

What is the "forced-use paradigm" of treatment after stroke? In the forced-use intervention, also known as constraint-induced movement therapy, the non-hemiplegic limb is restrained in an attempt to force the individual to rely on the use of the hemi-plegic limb for functional activities. Based originally on the observation that some of the disability in stroke survivors resulted in part from the patient's lack of use of the affected limb (as opposed to neurologically induced weakness of the limb itself) and also supported by favorable results derived from animal studies, this method was found in recent human studies to improve recovery of ADL function and also brain activity among individuals with hemiplegia resulting from stroke.

Describe the common treatment approaches used for spasticity caused by stroke. Hemispheric strokes affect motor activity in several ways, causing weakness and synergy patterns as well as spasticity. Typically causing more functional impairment in the upper extremity than in the lower limb, spasticity is usually (but not always) less severe in patients with cerebral lesions than in those with spinal cord lesions. Treatment of spasticity relies most heavily on proper positioning, orthotics, and aggressive, consistent stretching exercises to maintain and improve ROM. Other management strategies include casting, pharmacologic injection blocks of motor points or peripheral nerves (using phenol or botulinum toxin), therapeutic exercise other than stretching, casting, oral medications, and surgical release, the latter of which may be very effective in selected patients. The efficacy of medications remains controversial, but dantrolene sodium (Dantrium) is probably the drug of choice for patients with cerebral spasticity. Most recently, selective local intramuscular injection of low doses of botulinum toxin A (Botox) has been found to be effective in reducing local muscle tone for about 3-6 months, resulting in improved function and decreased pain sensation in some patients.

Describe common shoulder problems in stroke survivors and what can be done about them. Approximately 70-80% of patients with stroke and hemiplegia have shoulder pain, contrac-ture, or another form of dysfunction, making it one of the most common secondary complications of stroke. Causes of hemiplegic shoulder dysfunction are many and can include glenohumeral sub-luxation, adhesive capsulitis (frozen shoulder), impingement syndromes, rotator cuff tears, brachial plexus traction neuropathies, complex regional pain syndrome ("shoulder hand syndrome," present in up to 25% of patients), bursitis and tendinitis, and central pain. Often, there is either a history or radiographic evidence of a preexisting or long-standing shoulder problem, and it is likely that the abnormal mechanical forces resulting from the stroke either exacerbate or make manifest the chronic problem. In some patients, pain and loss of ROM are associated with improper positioning or handling, weakness of the shoulder girdle muscles, or spasticity. Shoulder dysfunction has been found to be present significantly more frequently in patients with spastic upper limbs than in those with flaccid upper limbs. Pain and glenohumeral subluxation may occur together or independently, and the extent to which there is a causal relationship between pain and subluxation is unclear.

Treatment of shoulder dysfunction is individualized and may consist of arm supports, shoulder slings, arm troughs, lap boards, medications, physical modalities, proper positioning and staff handling, and, most importantly, aggressive and consistently performed ROM exercises. The use of shoulder slings is controversial, but if subluxation is the main cause of the shoulder dysfunction, then slings may be helpful. Ensuring consistent performance of stretching exercises is the major clinical task.

What is central post-stroke pain syndrome? Previously known as thalarnic pain or Dejerine-Roussy syndrome, central post-stroke pain syndrome occurs in less than 5% of stroke survivors. It causes severe and disabling pain, which usually is described by patients as diffuse, persistent, and refractory to many treatment attempts. The most common descriptions of the pain are "burning and tingling", although many experience "sharp, shooting, stabbing, gnawing," and more rarely, "dull and achy". The dysesthesias are often associated with hyperpathia, which is an exaggerated pain reaction to mild external cutaneous stimulation. Only about 50% of the patients have thalamic strokes; the remainder have cerebrovascular lesions in a variety of locations.

Treatment methods include:

Medical and nursing care

Prevention and treatment of bladder, bowel, and skin problems

Prevention and treatment of other medical problems such as infection

ROM exercises

Mobility exercises

Psychologic methods

Relaxation, imagery

Biofeedback

Hypnosis

Psychotherapy

Preoccupation/distraction

Medications

Analgesics

Antidepressants

Anticonvulsants

Surgical techniques (rarely used)

Describe the common types of aphasia that occur after stroke. Global aphasia: loss of both expression and comprehension abilities. Patients have non-fluent or absent speech.

Broca's aphasia: reduction in expressive, and therefore repetition, abilities, but with preservation of comprehension. Speech is nonfluent.

Wernicke's aphasia: reductions in comprehension and repetition, but with preservation of expression. Speech is fluent but often nonsensical.

Transcortical motor aphasia: expressive dysfunction with intact comprehension and repetition.

Transcortical sensory aphasia: loss of comprehension ability with intact expression and repetition.

Conduction aphasia (relatively rare): isolated loss of repetition, while expression and comprehension remain intact.

What is melodic intonation therapy? How does it work? Melodic intonation therapy is a direct form of aphasia treatment that utilizes the patient's relatively unimpaired ability to sing, which can facilitate spontaneous speech in some patients. Therapy starts with the therapist and patient chanting simple phrases and sentences in unison to melodies that resemble natural intonation patterns. This progresses to a level at which the patient is able to chant answers to simple questions, and in some cases, the patient makes the transition off intoned speech and into normal prosodic speech patterns. This method is most successful in patients with good auditory comprehension and limited verbal expression. It is thought that the effectiveness of this method derives from the reliance on the unimpaired musical functions of the right hemisphere to support the damaged motor speech function in the left hemisphere.

What is hemispatial neglect and how can it be treated? Unilateral hemispatial inattention, or neglect, is the lack of awareness of a specific body part or external environment. Neglect usually occurs in patients with right (nondominant) hemisphere cortical strokes; these patients ignore or have muted responses to visual, auditory, or tactile stimuli on the left side of the body or environment. Patients with severe hemi-inattention deny that they have an illness or that neglect is a problem, or they may not recognize their own body parts. Neglect can improve spontaneously but can impede performance of functional tasks and complicate rehabilitation efforts.

Treatment methods emphasize retraining, substitution of intact abilities, and compensatory techniques. Specific treatment strategies include providing visuospatial cues, fostering awareness of deficits, using computer-assisted training, visual scanning skill training, caloric stimulation, Fresnel prism glasses, eye patching, dynamic stimulation, and optokinetic stimulation.

What is Gerstmann's syndrome? Gerstmann's syndrome occurs following damage to the left parietal region of the brain, which causes the four findings of dyscalculia, finger agnosia, right-left disorientation, and dysgraphia.

What are the apraxias?

The term apraxia is applied to a group of complex cognitive disorders that adversely affect motor function, usually characterized by difficulty in planning, organizing, sequencing, and executing learned voluntary movements, in the absence of weakness, ataxia, or extrapyramidal dysfunction. Several specific types of apraxias have been identified:

Motor or ideomotor apraxia: Patient can perform a particular movement automatically or spontaneously, but cannot repeat the movement when asked.

Ideational apraxia: Failure to hold onto ideas and plans necessary to perform an activity.

Constructional apraxia: Disturbance in the organization of individual spatial elements such that the patient is unable to synthesize the elements into a whole. Inability to put together an object from separate parts or to draw a picture of an object.

Apraxia of speech: Deficit in motor programming of speech. Often associated with Broca's aphasia.

Dressing apraxia: Inability to dress self despite adequate motor ability.

Apraxia of gait: Difficulty in initiating and maintaining a normal walking pattern when sensory and motor functions are otherwise unimpaired. Usually associated with frontal lobe lesions.

How common is post-stroke depression? What can be done about it? The incidence of depression after stroke ranges between 10% and 70%, with the best estimates at around 30%. Major depression is present in about one-third of all of those with depression. Depression may result from a biologic effect of the brain damage itself, a reaction to the losses caused by the stroke, effects of certain medications, manifestations of certain medical conditions, or a combination of these factors. Depression may adversely affect both participation in rehabilitation and functional outcomes.

The choice of treatment depends on the cause and severity of the symptoms. Review of medications and treating intercurrent medical illnesses are important first steps. A rehabilitation program that includes therapy for physical and cognitive disabilities, interaction with others, and attention and encouragement from family and staff is often extremely helpful. Many patients respond favorably to more intensive psychotherapy or to the use of antidepressant medications, which have been demonstrated in at least three randomized controlled clinical trials to be effective in treating post-stroke depression and in improving functional abilities.

What are some of the typical functional outcomes after stroke? It is estimated that only about 1 in 10 stroke patients are functionally independent at the time of stroke and that nearly one-half are independent at 6 months. Results of the Framingham Study provide estimates for the types and frequencies of long-term disabilities in stroke survivors:

______TYPE OF DISABILITY____________%____________

Decreased vocational function 63

Decreased socialization outside home 59

Limited household tasks 56

Decreased interests and hobbies 47

Decreased use of transportation 44

Decreased socialization at home 43

Dependent ADL 32

Dependent mobility 22

Living in institution 15

The frequencies for all of these disabilities were significantly greater than those in age- and gender-matched controls in that study. Estimates for disabilities in some specific activities after 6 months post-stroke are as follows:

______TYPE OF DISABILITY____________%____________

Unable to walk 15

Needs assistance to transfer 20

Needs assistance to bathe 50

Needs assistance to dress 30

Needs assistance to groom 10

List the commonly cited predictors of unfavorable functional outcome after stroke.

Prior stroke Unemployed

Urinary incontinence Cardiac disease

Bowel incontinence Coma at onset

Depression Inability to perform ADL (most important)

Visuospatial perceptual deficits Poor sitting balance

Cognitive deficits Large cerebral lesions

Delayed acute medical care Dense hemiplegia

Delayed rehabilitation (Homonymous hemianopsia)

Low functional score on admission (Aphasia)

to rehabilitation program (Increased age)

Poor social supports (Medical comorbidity)

Unmarried

Describe some of the unique considerations in rehabilitation of older adults with stroke. Because a substantial proportion of stroke survivors are over age 65 years, consideration of issues that tend to be more common among older adults assumes prominence in the care of stroke survivors. Some of the most important of these problems are the increased frequency of preexisting medical conditions and prior stroke, increased risk of secondary post-stroke medical complications, increased likelihood of recurrent stroke, and slower recovery from secondary intercurrent medical illnesses. Many of these problems result from reduced endurance and limited physiologic reserve among older adults. Older adults are at greater risk for falls with injuries, adverse drug reactions, and neurologic changes resulting in altered cognitive, sensory, and motor functioning.

For many older patients, the problem that is more significant than medical comorbidity is a relative lack of family, economic, and social resources. Spouses and other caregivers are often either not available or not able to provide post-rehabilitation care for the older stroke survivor. Institutional discharges tend to be more common among older adults.

Mechanotherapy

These problems may delay or inhibit participation in the therapeutic exercise program, complicate the rehabilitation course, and prolong hospitalization. It is important to note, however, that studies have shown that older adults are able to make functional improvements in amounts that are similar to those of younger stroke patients. Compared to younger individuals, older adults tend to have lower functional ratings on admission (and therefore at discharge), primarily because of the greater frequencies of comorbidities and prior strokes and also because of greater stroke severities among older patients.

Describe some of the unique considerations in rehabilitation of younger adults with stroke. Approximately one-third of all strokes occur in individuals who are under age 65 years. The distribution of various diagnostic etiologies of stroke differ for this group. Hemorrhagic strokes tend to be more common in younger adults, accounting for about one-third of all strokes, and infarctions are caused by atherosclerosis (about 20% of all infarctions), cardiogenic embolism (about 20%), cerebral vasculitis with or without systemic collagen vascular diseases (about 10%), coagulopathy (about 10%), and other causes.

Rehabilitation and long-term care issues that are more relevant for younger adults than for others include employment, sexuality, child care, instrumental ADLs (e.g., meal preparation, shopping, housekeeping), psychological aspects of life-role changes, spousal and other relationship changes, financial management, driving, leisure planning and hobbies, and socializing. As a consequence, specialized rehabilitation training efforts focused in these areas for these patients, together with psychological counseling, community reentry training, and social programs, can help to enhance the quality of life for young adults with stroke.

MULTIPLE SCLEROSIS

What are the demographics of multiple sclerosis (MS)? One-quarter to one-half million people in the U.S. have MS, and about 8,000 new cases are diagnosed each year. Symptoms begin between ages 20-50 in 90% of cases; the peak age is 33. MS is twice as common in whites and females. Residing in a temperate climate is also an associated factor. Identical twin concordance is 30%. The lifetime risk of a female child whose mother has MS is 5% (50-fold higher than general population).

Describe the pathophysiology of MS. MS is a very complex disease characterized by recurrent plaques scattered throughout the brain, spinal cord and optic nerves. Plaques are demyelinated white matter of the CNS with lymphocytic invasion. New evidence suggests there is also axonal damage and brain atrophy. Discrepancies in the numbers of MRI lesions and clinical presentation may exist.

Many environmental and genetic factors have been implicated in the cause of the disease: human herpesvirus 6, Chlamydia pneumonias, and the hepatitis B vaccine have been implicated as possible factors in triggering the disease. In short, the development of MS is determined by a number of genetic and environmental factors.

What patterns of disease are seen in MS? There are typically four patterns. Relapsing-remitting MS, the most common pattern (40-60%), involves episodic relapses approximately once per year with recovery and a stable phase between relapse. Recovery may be incomplete, and disability accumulates over time. Ten percent of patients have a benign course with no or mild disability. Half of patients with relapsing-remitting MS change patterns after 10-20 years to secondary progressive MS (gradual neurologic deterioration without acute relapses). These two patterns account for 85% of MS patients. Ten to 15% have primary progressive MS; this pattern shows gradual but continuous neurologic deterioration. Progressive relapsing MS occurs in less than 5% of cases and involves gradual but continuous neurologic deterioration with superimposed relapses. Death may occur in weeks to months.

What is a pseudoexacerbation? An MS patient can have transient worsening of neurologic symptoms that is caused by an acute medical problem, usually a febrile illness. For instance, a urinary tract infection may cause worsening spasticity, which may mimic an exacerbation.

What are important prognostic signs in MS? Unfortunately, a poor prognosis is easier to predict than a good prognosis. Signs associated with poor prognosis include being male, over age 35, initial motor or cerebellar dysfunction, a rapid progression of disease, and initial symptoms being polysymptomatic. Better prognostic factors include being female, age < 35, initial sensory signs or optic neuritis, sudden onset with good recovery and long remissions, and complete and rapid remission of initial symptoms.

Describe the MRI and evoked potential findings that are seen in MS. Using standard MRI, 80-90% of patients diagnosed with MS have evidence of plaques. These hyperintense lesions are most common in periventricular white matter, corpus callosum, brainstem, optic nerves, and spinal cord. Standard MRI alone cannot make the diagnosis of MS. Enhanced FLAIR MRI promises to improve differentiation of plaques from normal structures. Magnetic transfer imaging (MTI) is more sensitive and specific for MS lesions. MTI may detect white matter lesions in those patients who have a negative MRI.

Interocular latency difference on visual evoked potential testing is the most sensitive indicator of optic nerve dysfunction. The most common somatosensory evoked potential abnormality with MS is increased interpeak latencies.

What clinical outcome measures of impairment and disability are used for MS? Kurtzke introduced a 10-step Disability Status Scale for MS in 1955. It was revised in 1961 to describe more detailed neurophysiologic involvement relative to functional status. Currently, the most widely used MS clinical outcome measure is the Expanded Disability Status Scale (EDSS). It divides the original 10 levels in half to increase the sensitivity for functional status. Criticisms of the scale are that it is an impairment scale rather than a measure of disability, it is insensitive to small changes, and it has poor inter-rater reliability. Additionally, it focuses on am-bulation as the primary functional activity.

To overcome this limitation, a new outcome measure has been proposed. The Multiple Sclerosis Functional Composite (MSFC) consists of three objective quantitative tests of neurologic function, encompassing arm, leg, and cognitive function. Studies have found that MSFC predicted subsequent change in the EDSS, suggesting that the MSFC is more sensitive to change. Other scales developed for MS patients include the Minimal Record of Disability, Inability Status Scale, Environmental Status Scale, and Scripps Neurologic Rating Scale.

Is inpatient or outpatient rehabilitation useful in treating multiple sclerosis? Studies show that inpatient rehabilitation has an effect on disability and handicap despite no change in impairment. In addition, there are improvements in health-related quality of life perception. After discharge, as the neurologic status worsens, benefits may last for over 6 months but diminish without ongoing therapies.

Outpatient therapies therefore play an important role in this progressive disease. DiFabrio studied a group of patients with chronic progressive MS treated with an extended outpatient rehabilitation program. After 1 year of outpatient treatment, patients had reduced fatigue and a lower rate of decline in physical function than subjects in a control group not receiving ongoing therapy.

Can MS patients benefit from exercise? Caution must be taken when prescribing physical activity. Symptoms can temporarily worsen on exposure to heat or physical exercise. Programs are designed to activate working muscles but avoid overload. Exercise evaluation and prescription must account for fatigue, spasticity, ataxia and incoordination, as well as neurologic deficits seen in MS. Emphasis should be maintenance of general conditioning. Maximizing passive and active ROM is critical. Aerobic training improves fitness and quality of life. In addition, studies show aquatic therapy in cooler water results in strength gains.

How can fatigue be assessed and treated in MS? Fatigue is the most common symptom impairing ADLs and the most common complaint by MS patients. Several different scales, such as the Fatigue Severity Scale, Fatigue Descriptive Scale, and Fatigue Impact Scale, are used for assessment. In evaluating the patient, ensure that he or she is getting enough sleep, and rule out medical problems such as hypothyroidism or infection. Nonpharmacologic management is generally the most effective treatment. Both physical and occupational therapists will be helpful to train the patient in energy conservation techniques and work simplification. An evaluation should be made for adaptive equipment needs. Amantadine and pemoline (Cylert) are common pharmacologic treatments used and are each effective in about 50% of patients treated. Other pharmacologic treatments include SSRls, calcium channel blockers, methylphenidate, amphetamines, and selegeline.

What is Uhthoff's phenomenon? Fatigue worsened by heat. Fatigue is usually less in the morning and more in the afternoon. It is worsened by physical exertion and heavy meals that may increase core temperature. Therapies should be scheduled with this in mind. A cooling vest may decrease core temperature 0.5-1°C which may improve the ability to exercise.

How is spasticity managed in MS? Spasticity is seen in about 55% of MS patients. It can cause pain, disrupt sleep, and impair volitional movement and daily activities. Conversely, spasticity may play a role in ability to transfer, stand, and ambulate, and, therefore, the decision to treat spasticity must consider the problems and benefits. Causes for an increase in tone must be determined prior to initiating treatment. The most common cause of exacerbation of spasticity is a urinary tract infection, but other sources of noxious stimuli must be excluded.

The first line of treatment involves splinting, positioning, stretching, and cooling the muscles. Baclofen is usually used first when oral agents are needed. It is started at 5 to 10 mg/day, with the dose titrated every 5-7 days. Other oral medications include dantrolene, diazepam, clonidine, clonazepam, tizanidine, gabapentin, and cycloheptadine. Botulinum toxin injections and phenol blocks are most effective for focal spasticity. Intrathecal baclofen is an option when other medications are ineffective. It is most effective for lower-extremity spasticity.

What types of bladder dysfunctions occur and how can they be treated? Symptomatic bladder dysfunction occurs in most patients with MS. The severity of dysfunction is not related to the age of the patient or duration of disease, but urologic complaints are strongly related to the degree of disability. Bladder hyper- and hyporeflexia may occur. The most common urodynamic lesion found in MS is detrusor hyperreflexia. Unfortunately, symptoms do not differentiate between failure to store and failure to empty. In addition, bladder dysfunction may change over the course of the disease. Periodic urodynamics should be considered.

Intermittent catheterization is recommended for patients with failure to empty. Nighttime bladder dysfunction can be treated with low-dose intranasal antidiuretic hormone (desmopressin). Detrusor hyperreflexia can be treated with oxybutynin (Ditropan) or tolterodine (Detrol).

How is incoordination treated? Incoordination is a common problem in MS and ranges from mild tremor to severe ataxia. Cerebral outflow tremors are the most common type. Therapy is aimed at compensatory strategies. Weighted cuffs to dampen incoordination may diminish the amplitude of tremor but are not well tolerated. Frankel's exercises, originally described to treat tabes dorsalis, are used to treat incoordination and ataxia. They require a high degree of concentration and frequent repetition and therefore may not be appropriate for all MS patients. Carbamazepine has been reported to reduce the severity of tremors at doses of 400-600 mg/day. Isoniazid, propanolol, primidone, and clonazepam have all been used with varying success. Stereotactic ventrolateral thalamotomy has had benefit in select patients.

How is ambulation impairment treated in MS? Seventy-five percent of MS patients have varying degrees of ambulatory impairment. Treatment requires a comprehensive evaluation. Weakness, fatigue, spasticity, and incoordination may all contribute to ambulation impairment and may require treatment. Gait evaluation should be made on varying terrains, elevations, and stairs. Evaluation of deficiencies will guide the therapy prescription. The need for orthotics and assistive devices should be considered. Increasing the width of the ambulatory-base with a cane or lightweight walker often improves the safety of ambulation.

What affective disorders are seen in MS? Affective symptoms range from mania to depression. Depression is an important consideration when patients complain of fatigue. The frequency of depression ranges from one-quarter to greater than one-half of patients. The risk of suicide in the MS population is 7-14 times greater than in the normal population. Incidence of depression appears to be correlated with gender, age, education, and a history of previous depression. Surprisingly, it does not appear to be related to disease severity, or the physical and cognitive status of the patient. Selective serotonin-reuptake inhibitors (SSRIs) are effective but can precipitate spasticity and require close evaluation. Amitriptyline or SSRIs can be used for excessive laughing or crying. Clonazepam and buspirone are useful for anxiety.

What cognitive changes are seen with MS? Jean-Marie Charcot first recognized an association between cognitive deficits and MS over 100 years ago. Varying degrees of cognitive impairment are seen in MS, even early in the disease, and it appears to be more significant in chronic progressive than relapsing-remitting MS. Approximately half of MS patients are affected, and up to 7% are severely impaired. There is no correlation between disease duration or extent of physical disability and cognitive impairment; however, Bone and colleagues demonstrated a correlation between plaques load and dementia. Feinstein documented progressive MR imaging changes correlating with change on several psychometric tests.

The most frequent cognitive deficits seen in MS are in short-term memory, abstract reasoning, executive functions, and delayed processing. Frontal lobe dysfunction is commonly seen, including initiation, insight, and planning. Prefrontal disconnection may exhibit itself as inappropriate behavior, excessive talking, and poor judgment. Neuropsychological assessment should be offered to MS patients with cognitive decline. Subsequent counseling and cognitive rehabilitation are important to reduce the effects of cognitive deficits on ADLs.

What speech and language problems are seen in MS? Voice, articulation, and swallowing disorders are a significant problem in greater than one-third of MS patients, particularly those with brain stem involvement. Aphasia, anomia, and apraxia are seen in less than 1% of patients. Cognitive impairment also plays a significant role in language disorders.

Speech therapists teach compensatory techniques for dysarthria, such as slowing the rate of speech and emphasizing key words. Evaluation for dysphagia often includes a videofluoroscopic swallowing study. Changing food consistency, eating smaller more frequent meals, chin-tuck while swallowing, and monitoring the rate of eating are compensatory strategies.

Is GI dysfunction a significant problem in MS? Bowel dysfunction in MS (especially constipation) is relatively common (> 50%) and poorly studied. Bowel dysfunction has multiple causes. Reduced colonic transit and disorders of defecation can cause constipation. Fecal incontinence can be due to loss of sensation in the rectum and reduced voluntary anal sphincter contractions. MS-related spinal cord involvement seems to be less important for bowel dysfunction than for neurogenic bladder dysfunction. Treatment involves the common medications for constipation but is usually not very successful.

Mechanotherapy

What type of pain is seen in MS? Not very long ago, MS was considered a painless disease! We now know that more than half of all MS patients experience pain, that there are different types of pain, and that all types of pain can be severe. Acute types of pain in MS are trigeminal neuralgia, episodic facial pain, paroxysmal pain in arms and legs, and headache. Two percent of MS patients experience trigeminal neuralgia. It occurs 400 times more often in MS than in the general population. Treatment of trigeminal neuralgia and episodic/paroxysmal pain involves carbamazepine, baclofen, phenytoin, gabapentin, or lamotrigine. Chronic pain of neurogenic origin is common in MS patients and is described as burning, tingling, or tickling. Older tricyclic antidepressants, in particular amitripty-line, are effective in many patients, often in combination with TENS. Gabapentin up to or above 2400 mg is usually well tolerated and effective. Spasms and cramps can also be very painful. Treatment is the same as for spasticity.

How does MS affect pregnancy and vice versa? MS does not appear to affect a woman's fertility, risk of spontaneous abortion, or congenital malformations. However, caution should be taken by women considering pregnancy because many medications taken for MS are or may be teratogenic. The consensus on risk of relapse during pregnancy is that it is not increased and may be decreased in the third trimester. The relapse rates in the 6 months after pregnancy, however, may be two to three times the nonpregnant rate. Pregnancy does not appear to have an adverse effect on long-term outcome and disability.

Explain the relationship between optic neuritis and MS. The Optic Neuritis Study Group followed > 400 optic neuritis patients for > 5 years. Those who were more likely to develop MS were white, female, had a history of vague neurologic symptoms at the time of presentation with the optic neuritis, had a family history of MS, or had a positive MRI. Fifty-one percent of those with three or more lesions on MRI at the time of the original presentation developed MS.

What is the scoop on the new MS medications? Corticosteroids remain the mainstay for the treatment of acute exacerbations of MS. They shorten the duration of exacerbation, but do not appear to affect the long-term course of the disease. ACTH may also be used.

There are many medications used to prevent the exacerbations seen in relapsing-remitting MS. The three most commonly used are interferon-(31b (Betaseron), interferon-(3la (Avonex), and glatiramer acetate (Copaxone). Both of the interferons are well tolerated, with interferon-pla generally being tolerated better than Interferon-(31b. The most common side effect is flu-like symptoms. Interferon-pla is the only medication that has been shown to reduce the number of exacerbations and lesions on MRI and to reduce the risk of disability progression. Glatiramer acetate is usually used when there is a treatment failure with the interferons. There is no documented benefit of hyperbaric oxygen or other alternative medicine approaches.

NEUROMUSCULAR STIMULATION

Neuromuscular stimulation has been used in stroke and spinal cord injury rehabilitation to improve function. The bulk of the discussion focuses on the use of elec trical stimulation in musculoskeletal injuries. Neuromuscular stimulation is used for overcoming reflex inhibition after an injury to allow the establishment of appropriate motor engrams. By programming appropriate engrams, the injured individual is less likely to use inappropriate muscle substitution patterns that may lead to future injury. Muscle stimulation also may be used to counteract immobilization atrophy, improve range of motion, break down adhesions in the muscle, and assist in relieving pain and muscle spasm. Athletic trainers may use muscle electrical stimulation at the end of a season to counteract fatigue and less voluntary effort during workouts. It has also been marketed for improving abdominal muscle tone without having to do sit-ups. After nerve injuries such as brachial plexopathy from a football stinger, electrical stimulation has been used to maintain muscle viability.

Apparatus for electrical stimulation

Physiologic contraction of muscle occurs in a grade fashion, with the smaller, fatigue-resistant motor units type I, being recruited first followed by larger and larger motor units. With electrical stimulation, the larger diameter Type II fatigable fibers are recruited first. Muscle tension decreases as the fibers fatigue, unless the unit is turned up. Excessive fatigue can occur but can be limited by giving adequate rest periods between contractions and limiting the duration and frequency of the contractions. Criticism of the nonphysiologic muscle contraction produced by direct muscle electrical stimulation has led to a replacement of electrical stimulation with active assisted range-of-motion exercises by the athlete.

Apparatus for electrical stimulation

Electrical Parameters

Symmetric, biphasic square waveforms have demonstrated better patient tolerance compared with other waveforms. This waveform also allows generation of a larger muscle contraction compared to a monophasic waveform. Asymmetric, biphasic waveforms are used particularly with smaller muscles but have a greater incidence of burns and skin irritation owing to the accumulation of charge under one electrode. Amplitude intensity is set as tolerated by the patient up to 100 mA. The greater the intensity, the greater the force generated by the muscle contraction. Pulse duration varies from 0.2-0.4 msec and allows adjustment for patient tolerance when coupled with variable amplitude intensity. A pulse duration greater than 1.0 msec is associated with stimulation of pain afferents. Low frequencies are associated with incomplete muscle contraction. At 30 Hz, the muscle demonstrates tetanized contractions. Duty cycle is the ratio of on time (pulse train duration) to total time (on and off time) expressed as a percentage. For orthopedic problems, a 25% duty cycle has been suggested. If fatigue is a factor, then the duty cycle can be reduced. Most units have a ramp feature. Ramping is a parameter that allows a gradual increase to peak intensity that is over 2 seconds. After the peak amplitude is maintained for a specified period, the intensity is ramped down. This parameter theoretically allows an approximation of a normal muscle contraction and greater patient comfort. Indications and contraindications for neuromuscular electrical stimulation are listed in Table 2. Adverse reactions typically occur with skin allergies to the electrodes, mechanical irritation from the electrodes and occasionally itching or skin burn due to accumulation of charge under one electrode.¹⁴

Clinical Uses

Neuromuscular electrical stimulation use is ubiquitous with musculoskeletal injuries in athletes. After an injury, pain and joint effusion can lead to inhibition or partial inhibition of muscular contraction. This is particularly common in the initial phases of rehabilitation. Muscles near the joint are more commonly affected.

Table 3. Physiology of TENS

	Sample Size	Random	Controls	Blind	Hz	Amp	Time (min)	Tx Period	Outcome
Chapman¹⁰	24 Healthy vol human	No	Saline	Yes	2	44.7 mA	> 20	1 session	Naloxone blocked
Sjolund⁷⁷	10 Chronic pain human	No	Saline	Yes	50-100	2-3xPT	> 10	3 Months	0/10 +naloxone block
	10 Chronic pain human	No	Saline	Yes	2	3-5xPT	qd—QID	3 months	6/10 +naloxone block
Abram¹	15 Chronic pain human	No	Saline	Yes	58	12-20 mA	20	1 month	0/15 +naloxone block
Sluka⁷⁹	122 Arthritic rats	No	No	No	100	at PT	20	1 Session	High dose +naloxone block
					4	atPT	20	1 Session	Low dose +naloxone block
Hughes³⁸	10 Healthy vol human	Yes	Sham TENS	No	off	off	30	1 Session	No change endorphins
	9 Healthy vol human	Yes		No	104	32 mA	30	1 Session	Increase beta endorphins	pi
	12 Healthy vol human	Yes		No	4	57 mA	30	1 Session	Increase beta endorphins	n
Salar⁷⁵	13 no pain neuro pts	No	No	No	40-60	40-80 mA	20-90	1 Session	Incr CSF endorphins	can
Almay³	18 Chronic pain human	No	No	No	80-100	2-3xPT	15-30	I Session	Incr CSF endorphins & subst P	o
Han³⁵	17 Neuro pts	Yes	No	No	100	26-30 mA	30	I Session	Incr CSF dynorphin A	P- EL
	20 Neuro pts	Yes	No	No	2	26-30 mA	30	1 Session	Incr CSF enkephalin	ities
Woolf⁹⁵	25 Rats/thermal threshold	No	Own	No	50-100	10-15V	30	1 Session	40-70% relief, +Naloxone	5'
			control						block	p
Woolf⁹⁴	Ischemic	No	Yes	No	100	above PT	30	1 Session	Deer VAS, Incr Pain Tol	c
Roche⁷⁴	Ischemic	No	No	No	100	4-14.2 V	> 10	1 Session	Incr Pain tol & endurance
					5	3.7 V	10	1 Session	Incr Pain tol & threshold	1
Walsh⁹¹	32 NI Human/ischemic	Yes	No TENS/	Yes	110	above PT	22	2 Sessions	No difference	2
			sham TENS		4	above PT	22	2 Sessions	Significant deer VAS	EL
Sluka⁷⁸	21 Rats/arthritic	Yes	No TENS	No	100	Below me	20	1 Session	Incr in thermal threshold
					4	Below me	20	1 Session	Incr in thermal threshold
Walsh⁹³	50 Healthy humans	Yes	No TENS	Yes	110	above PT	45	1 Session	No difference	ain
					4	above PT	45	1 Session	No difference	S
Deer, decrease; Incr, increase; me, muscle contraction; mA, milliamperes;					Neuro, neurologic; NI, normal; PT, paresthesia threshold				; Pts, patients; Subst, sub-	:dic:
stance; Tol,	tolerance; VAS, visual analog scale; V,		volt; Vol, volunteer.							ine