About 90% of the population suffer from

DEGENERATIVE DISEASES OF THE LUMBAR SPINE

 

About 90% of the population suffer from low back pain at some time and 30% of these will develop leg pain due to lumbar spine pathology.

The critical factor in assessing patients with low back pain is whether there are also features of lumbosacral nerve root compression, such as leg pain or focal signs of neural compression in the lower limbs. In general, neurosurgeons are principally concerned with lumbar spine pathology that causes nerve root compression. Sciatica is the clinical description of pain in the leg due to lumbosacral nerve root compression which is usually in the distribution of the sciatic nerve. Sciatica was first mentioned in an Egyptian manuscript dated 2500–3000 BC. In 1934 Mixter and Barr established that a prolapsed lumbar intervertebral disc was commonly the cause of sciatica.

Alumbar disc prolapse can occur at any age in adults but is uncommon in teenagers..

 

Sciatica

Aetiology

The most common cause of sciatica is a lumbar disc prolapse causing nerve root compression. Sciatica-type pain may also occur as a result of bony compression of the nerve root, usually by an osteophyte, and is often associated with lumbar canal stenosis or spondylolisthesis. Narrowing of the ‘lateral recess’ of the spinal canal may also occur in conjunction with lumbar canal stenosis, and may cause compression of a nerve root. Sciatica may occasionally be caused by tumours of the cauda equina or by pelvic tumours, such as spread from carcinoma of the rectum.

Anatomy and pathology

Nearly 75% of the lumbar flexion–extension and of total spinal movement occurs at the lumbosacral junction, 20% of lumbar flexion–extension occurs at the L4/5 level and the remaining 5% is at the upper lumbar levels. Consequently, it is not surprising that 90% of lumbar disc prolapses occur at the lower two lumbar levels; the most frequently affected disc is at the L5/S1 level. The lumbar disc consists of an internal nucleus pulposus surrounded by an external laminar fibrous container, the annulus fibrosus. A disc prolapse may consist of the nucleus pulposus bulging, with the annulus being stretched but intact. Alternatively, the nucleus may rupture through the annulus and sequestrate as a free fragment under the posterior longitudinal ligament or lie in the extradural space. Prolapse of the disc is usually in a posterolateral direction, as the posterior longitudinal ligament prevents direct posterior herniation. Less frequently the disc may herniate laterally to trap the nerve in the neural foramen.

Fig. 13.1 The diagram shows (a) a posterolateral lumbar disc proplapse causing compression of lumbar nerve root passing across the disc to enter the neural canal below the pedicle and (b) a lateral disc prolapse causing compression of the nerve root passing beneath the pedicle above the disc prolapse.

 

A prolapsed intervertebral disc causes compression of the nerve which runs along the posterior aspect of the disc and down under the pedicle of the vertebra below (Fig. 13.1). Consequently, an L4/5 posterolateral intervertebral disc prolapse will usually compress the L5 nerve root, which runs caudally across the disc to enter the neural foramen below the L5 pedicle. Similarly, a lumbosacral (L5/S1) disc prolapse will usually affect the S1 nerve root. The less common lateral disc prolapse will cause compression of the nerve root at one level higher than expected (e.g. L4 nerve root compression due to L4/5 lateral disc prolapse). In the case of a large disc prolapse, there may be evidence of more than one nerve root compression.

Cauda equina compression may result if the disc herniation is sufficient to rupture the posterior longitudinal ligament and produce a posterior central disc prolapse.

Patient assessment

The patient suffering from sciatica will be in obvious discomfort, which will be reflected by movements and posture when lying supine. The patient lies tilted, usually to the side opposite to the sciatica, with the affected hip and knee slightly flexed taking pressure off the stretched nerve. The pain is worse on movement, coughing, sneezing or straining. Although back pain may be present, the important feature is the pain which radiates down the leg in the distribution of the affected nerve. The pain usually radiates into the buttock, along the posterolateral aspect of the thigh and calf into the foot (S1 nerve root); it may extend into the dorsum of the foot and great toe (L5 nerve root). An L3/4 disc herniation may produce pain in the posterior thigh but, as with an L2/3 disc prolapse, the pain is frequently along the anterior aspect of the thigh. L4 root pain frequently radiates into the anterior aspect of the lower leg. Depending on the degree of nerve root compression, the patient may complain of sensory disturbance such as numbness or tingling in the leg or foot, and weakness may be present. The history must include an assessment of sphincter function, as a large disc prolapse may cause cauda equina compression.

Examination of the neurological disability should proceed in an ordered fashion. Initially a search is made for ‘wasting’ in specific muscle groups, particularly the quadriceps, calf muscles, extensor digitorum brevis muscle and the small muscles of the foot. The patient is then examined for weakness in each of the muscle groups (Tables 13.2). Weakness of dorsiflexion of the foot and extension of the great toe (extensor hallucis longus) is most commonly caused by a prolapsed L4/5 intervertebral disc with involvement of the L5 nerve root; severe cases may result in a complete foot drop.

Plantar flexion weakness is caused by compression of the S1 nerve root, usually due to a prolapsed lumbosacral disc. However, plantar flexion is a very strong movement and any weakness may be difficult to elicit unless tested by asking the patient to stand on the toes of the affected side. Alarge prolapsed disc at the L4/5 level may result in some plantar flexion weakness because of compression of the S1 nerve root, and similarly a large lumbosacral disc prolapse may be associated with dorsiflexion weakness due to L5 nerve root compression.

The deep tendon reflexes should be carefully tested as they provide objective evidence of nerve root compression. The ankle jerk is depressed or absent when the S1 nerve root is compressed, usually by a lumbosacral disc prolapse. Sensation should be tested in the foot and leg (Fig. 13.2).

Fig. 13.2 Segmental distribution of nerves of the lumbar and sacral plexuses to the skin of the anterior and posterior aspect of the lower limb.

 

At the end of the examination the patient should be turned prone so that the buttocks can be inspected for atrophy of the gluteal muscles, sensation can be tested along the back of the legs and in the perianal region, and anal tone can be assessed. A rectal examination should be performed if there are clinical features suggestive of a pelvic tumour.

Summary of clinical features

Clinical localization of the disc prolapse should be possible in the majority of patients with sciatica. The following features are typical (but not invariable) of disc herniation.

L5/S1 prolapsed intervertebral disc

• Pain along the posterior thigh with radiation to the heel

• Weakness of plantar flexion (on occasion)

• Sensory loss in the lateral foot

• Absent ankle jerk.

L4/5 prolapsed intervertebral disc

• Pain along the posterior or posterolateral thigh with radiation to the dorsum of the foot and great toe

• Weakness of dorsiflexion of the toe or foot

• Paraesthesia and numbness of the dorsum of the foot and great toe

• Reflex changes unlikely.

L3/4 prolapsed intervertebral disc

• Pain in the anterior thigh

• Wasting of the quadriceps muscle

• Weakness of the quadriceps function and dorsiflexion

of foot

• Diminished sensation over anterior thigh, knee and medial aspect of lower leg

• Reduced knee jerk.

Management

Most patients with sciatica achieve good pain relief with simple conservative treatment and less than 20% will require surgery. The likelihood of symptomatic relief without surgery is related to the pathology of the disc prolapse. A‘bulging’ disc is likely to settle with simple conservative measures, but sciatica due to a nucleus pulposus that has herniated out of the disc space and ‘sequestrated’ outside the annulus will probably need surgery for satisfactory relief of symptoms.

Conservative treatment

Most patients achieve good pain relief following bed rest, usually for a period of about 7–10 days, and the use of simple analgesic agents and non-steroidal anti-inflammatory medication. Although traction is sometimes recommended it probably has only limited benefit and may result in lower leg complications. Resolution of the pain is probably due to a combination of some resorption of the prolapsed disc material, the oedema of the nerve decreasing and possible adaptation of the pain fibres to pressure. Spinal manipulation is not recommended and the concept that a disc prolapse can be ‘reduced’ by manipulation is a myth. Initially, the only necessary investigations are a plain lumbar spine X-ray and an erythrocyte sedimentation rate (ESR). The lumbar spine X-ray will diagnose an associated spondylolisthesis which may contribute to the sciatica, and it also helps to exclude sinister pathology, such as metastatic tumour involving the spinal vertebrae. The ESR will also exclude systemic disease.

Some clinicians advocate the use of high-dose corticosteroids in the conservative management of sciatica due to lumbar disc prolapse. Whilst steroid therapy may help to give transient pain relief, the limited benefit is probably outweighed by the possible complications of corticosteroid treatment.

Chemonucleolysis has, in the past, been advocated as a treatment for lumbar disc prolapse. It involves the intradiscal injection of a proteolytic enzyme, such as chymopapain, which dissolves disc material. Chymopapain was first isolated in 1941 and has been used intermittently since 1963 in clinical studies. There is a small risk of serious anaphylactic reaction following intradiscal injection. Although chymopapain dissolves the normal nucleus pulposus it has a high failure rate in the treatment of prolapsed disc, as it fails to affect the extruded disc material, and further nerve compression may occur following chemonucleolysis from the disc dissolving and collapsing, resulting iarrowing of the intervertebral neural foramen. The procedure is not recommended for use at this time.

Indications for surgery

Pain. The most common indication for surgery in patients with disc prolapse is pain in the following situations.

• Incapacitating pain despite 7–10 days of bed rest.

• Continuing episodes of recurrent pain when mobilizing despite adequate relief with bed rest. In this group of patients physiotherapy and a limited trial of a spinal brace might be tried, but they usually have only limited success.

Neurological deficit. A significant weakness or increasing amount of weakness is an indication for early investigation and surgery.

Central disc prolapse. Patients with bilateral sciatica or other features indicating a central disc prolapse, such as sphincter disturbance and diminished perineal sensation, should be investigated promptly. An acute central disc prolapse may lead to acute, severe, irreversible cauda equina compression and should be investigated and treated as an emergency.

Tumour. Surgery is indicated if the clinical features suggest that a tumour could be the cause of sciatica.

Investigations

Lumbar myelography (Fig. 13.3) was the timehonoured investigation for lumbar disc prolapse. The use of water-soluble non-ionic contrast material avoids the risk of the postmyelogram arachnoiditis previously seen with the oil-based mediums. Although myelography is now much safer, there is a very small risk of reaction to the contrast medium, particularly epileptic seizures. Some patients suffer headaches following the myelogram. These are due to the lumbar puncture and/or the effects of the contrast material.

Fig. 13.3 Lumbar myelogram using water-soluble contrast medium showing (a) posterolateral L4/5 disc prolapse and (b) complete block due to a large central L5/S1 disc protrusion.

 

High-quality computerized tomography scanning (Figs 13.4 and 13.5) and magnetic resonance imaging (Fig. 13.6) have largely superseded myelography for the diagnosis of lumbar disc prolapse. The MRI is especially helpful in showing the size, configuration and position of the disc prolapse, as well as any associated nerve root or thecal compression. In addition the MRI will also demonstrate pathology at other discs, such as degenerative changes as evidenced by decreased signal in the disc on the T2-weighted scans.

 

Fig. 13.4 (a) CT scans of lumbar spine showing posterolateral disc prolapses. (b) CT scan of left posterolateral disc prolapse after intrathecal contrast.

 

                                                                                            Fig. 13.6 MRI of lumbar disc prolapse.

 

Operative procedure for lumbar disc prolapse

The operation involves excision of the disc prolapse with decompression of the affected nerve root.

In the past the operation usually entailed a complete or partial laminectomy, identification of the compressed nerve root, its mobilization off the disc prolapse and excision of the herniated disc. However, with improvements in instrumentation and magnification, e.g. the operating microscope, most disc prolapses can be excised with minimal disturbance to the normal bony anatomy and with the removal of only a small amount of bone, usually from the adjacent laminae on the side of the prolapse.

Afull laminectomy may occasionally be necessary prior to the disc excision of a large central disc prolapse causing cauda equina compression.

A percutaneous lumbar discectomy to remove the nucleus pulposus is sometimes advocated for the ‘bulging’ lumbar disc. However, if the disc is ‘bulging’ the sciatica will nearly always settle with conservative treatment and surgery is not necessary. A percutaneous discectomy of the intradiscal contents will fail to relieve the sciatica if the disc has ruptured through the annulus, because it will not remove the herniated disc material causing the nerve root compression.

Postoperative mobilization

Most patients commence walking the day after surgery and are discharged from hospital on day 2 or 3 following the operation. Agently graduated mobilizing programme should be carefully explained to the patient, often with the help of a physiotherapist. Gentle back strengthening exercises commence after 10 days, and the patient should avoid prolonged periods of sitting, lifting and straining for the first 4 weeks. A graduated active exercise programme can commence after the first month.

Prognosis following surgery

The results following lumbar disc surgery are directly related to the accuracy of the preoperative clinical evaluation. Excellent results can be achieved if:

• there is a good history of sciatica

• there are good signs of nerve root irritation

• the investigations show evidence of a herniated disc

• at surgery the nerve root is stretched by a disc prolapse

• the patient is well motivated.

If any of the above criteria are absent the results following surgery are disappointing.

Recurrent sciatica following surgery occurs in about 10% of cases and is usually due to further disc prolapse, either at the same level or at another level. The principles of management are similar to those described for the initial treatment of sciatica. Recurrent sciatica is sometimes due to adhesions developing around the nerve root causing perineural fibrosis. The treatment is conservative, with judicious use of bed rest followed by gentle mobilizing exercises, simple analgesic medication and non-steroidal anti-inflammatory agents. Surgery to excise the adhesions is successful in relieving the pain in less than 60% of patients.

Rarely, recurrent sciatica is due to intradural arachnoiditis. Treatment is conservative and surgery to divide the intradural adhesion is rarely successful.

 

 

Lumbar canal stenosis

The patient with lumbar canal stenosis usually complains of pain radiating diffusely into the legs, particularly when standing or walking. The pain may be a diffuse ache, or is sometimes described as having a ‘burning’ quality; it is usually relieved with sitting and patients often adopt a posture of bending the body forward when walking to help relieve the discomfort. The pain may be similar to that described by patients with vascular occlusive disease, although a key feature is the presence of pain when standing only. On occasions there may be features of sciaticalike pain in association with the diffuse pain of lumbar canal stenosis due to entrapment of a nerve root by an osteophyte or within the ‘lateral recess’ of the canal.

The patient often complains of a subjective feeling of weakness and of a diffuse ‘numbness’ and ‘tingling’ radiating down the legs. Sphincter difficulties may occur if the stenosis is particularly severe.

Fig. 13.7 CT scan of lumbar spine showing severe lumbar canal stenosis.

 

Examination findings

The examination of the lower limbs and back often reveals little or no abnormality. Focal wasting may occur in the lower limbs if the compression is severe, and the ankle jerks may be depressed or absent. Definite sensory disturbance or weakness occur only in the most severe cases. The peripheral pulses should be checked as the symptoms may mimic those due to peripheral vascular disease.

Pathology and anatomy

The stenosis of the lumbar canal may involve reduction of the sagittal diameter of the canal, narrowing of the ‘lateral recess’ and stenosis of the neural foramen. The pathology is frequently due to a combination of congenital canal stenosis and degenerative pathology, such as lumbar spondylosis with hypertrophy of the facet joints and ligamentum flavum, osteophyte formation and thickening of the laminae causing further narrowing of the canal and bulging of the discs such that the space for the neural elements becomes compromised.

The most frequently affected levels are L4/5 and L3/4. The lumbosacral level may be involved, but this is less common. The stenosis may also be related to a degenerative spondylolisthesis, particularly at the L4/5 level.

Management

The clinical diagnosis of lumbar canal stenosis is usually straightforward, but it should be confirmed by radiological investigations. Highquality CT scanning (Fig. 13.7) and MRI (Fig. 13.8) have replaced the need for myelography (Fig. 13.9). All these radiological studies demonstrate the canal stenosis. The myelogram will show marked indentation of the contrast column and, if the stenosis is severe, there may be a complete block to the flow of contrast. The MRI will show the extent and severity of the stenosis as well as other pathology related to the lumbar discs such as degenerative disease and prolapse. The clinical features of lumbar canal stenosis

do not respond favourably to conservative treatment, and surgery is almost invariably successful in relieving the symptoms. The operation consists of a decompressive lumbar laminectomy extending over the whole region of the stenosis with decompression of the lumbar theca and nerve roots.

 

Fig. 13.8 MRI showing severe canal stenosis.

 

Fig. 13.9 Lumbar myelogram showing lumbar canal stenosis.

 

The patient can be mobilized promptly after the operation and a course of gently graduated active exercises prescribed, usually with the help of a physiotherapist.

 

 

Back pain

Low back pain without leg pain or signs of nerve root compression is a common problem. The usual presentations are:

• acute low back pain, often following minor trauma

• chronic or recurrent low back pain.

Acute sudden-onset back pain, following a recognized episode of trauma, is usually due to soft tissue strain. If the injury was severe it may have caused a fracture or disc herniation. The management of patients with an acute onset of back pain following trauma involves:

• history and examination to exclude symptoms and signs of nerve root compression

• radiological evaluation to exclude fracture or disc herniation (if severe trauma)

• conservative management with initial bed rest followed by gentle mobilization and simple analgesic medication.

Most of the pain and stiffness should settle after a few days, although mild discomfort may linger for some weeks.

The more difficult problem is chronic or recurrent back pain, where the patient gives a history of less severe or even trivial trauma. In some cases no pathological cause will be found. The most common aetiology is degenerative disease which includes:

• lumbar spondylosis

• spondylolisthesis

• degenerative disc disease.

Other uncommon but important causes of low back pain which, in the early stages, may present without pain radiating into the legs or radicular signs, include:

• spinal tumours

• thoracic disc prolapse

• spinal abscess

• arteriovenous malformation

Lumbar spondylosis, a degenerative disease involving the vertebral column, is the most common demonstrable cause of low back pain. The arthritic process may involve any of the spinal joints and be associated with degenerative disc disease. Low back pain, without features of sciatica, is only rarely caused by disc prolapse, and then only if the prolapse is large and central.

Spondylolisthesis

Spondylolisthesis is a subluxation of one vertebral body on another, usually involving the L4 or L5 levels, and may be due to congenital defects involving the neural arch or to degenerative changes. Spondylolysis describes a defect in the pars interarticularis, often the precondition for spondylolisthesis (Fig. 13.10).

Fig. 13.10 Lumbar spondylolysis with bilateral defects in the pars interarticularis.

 

Various classifications have been used to categorize spondylolisthesis; most subdivide the forms into those of congenital and those of degenerative origin.

The congenital dysplastic variety results from congenital deficiencies of the superior facets of the sacrum or the inferior facets of the 5th lumbar vertebra. The lumbosacral junction is incapable of withstanding the truncal forces imposed by the erect stance and there is gradual forward slippage of the 5th vertebral body. This is frequently associated with spina bifida occulta of L5 or S1.

The congenital isthmic category involves a defect of the pars interarticularis, either a lytic fatigue fracture or, rarely, when the interarticularis fracture occurs following severe trauma. Afurther subtype is when the pars is elongated  but intact.

Degenerative spondylolisthesis, also known as pseudospondylolisthesis, results from severe localized arthritis of the facets (apophyseal joints) of the slipped vertebrae.

Radiological investigations, including plain Xrays, CT scan and MRI, will show the type of spondylolisthesis, the amount of slippage and the associated narrowing of the neural canals (Fig. 13.11). The degree of subluxation is commonly described by the percentage of slip (Taillard method) or assigned a grade (I–IV) based on the number of quarters of the adjacent body spanned by the slip.

Fig. 13.11 CT scan showing lumbar spondylolisthesis

 

Clinical presentation

The presenting features involve back pain and leg pain. The initial symptom is usually back pain, which may radiate into the buttocks, but patients often complain of a ‘tight’ feeling in the upper thighs. Symptomatic children and adolescents often have a gait disturbance, the so-called ‘tight hamstring’ syndrome.

The vertebral slippage may produce compression of the lumbar nerve roots in the neural foramen. This causes sciatica, the symptoms of which may be indistinguishable from those due to disc prolapse. Narrowing of the bony canal may result in clinical symptoms of ‘lumbar canal stenosis’.

Treatment

Children and adolescents

In the majority of children and adolescents symptomatic spondylolisthesis responds to conservative treatment. The following indications are guidelines for lumbar fusion.

• Pain unrelieved by conservative measures.

• Progression of subluxation on serial radiological studies.

• Subluxation of greater than 30%.

• Tight hamstring gait.

The usual surgical procedure is a spinal fusion. Only rarely is a laminectomy necessary, and it should never be performed unless the spine is fused as there will be a progressive slip.

Adults

In most patients conservative therapy involving short periods of bed rest during exacerbations of discomfort, gentle mobilizing exercises, simple analgesic medication and non-steroidal anti-inflammatory medication will be sufficient. If some pain persists following bed rest a period with a  properly fitted lumbar brace may be of value.

Surgery involves either a laminectomy to decompress the neural structures and/or a spinal fusion to prevent instability. The indications for laminectomy include:

• symptomatic spinal canal stenosis (that is, symptoms of lumbar canal stenosis)

• clinical features of nerve root compression (e.g. sciatica) unrelieved by conservative therapy.

A laminectomy decompresses the lumbar theca and nerve roots, usually with satisfactory relief of lower limb symptoms. However, a laminectomy may increase the instability and some surgeons prefer to combine a decompressive laminectomy with a spinal fusion. An intertransverse fusion between the transverse processes has been the traditional method of fusion, but more recently internal pedicle screw fixation and/or interbody ‘cages’ placed in the emptied disc space between the vertebral bodies have become the preferred method.

Spinal fusion, without laminectomy, is occasionally indicated and should be considered in patients with the following conditions.

• Incapacitating low back pain unrelieved by conservative treatment, where the radiological findings show a relative absence of degenerative disease as a cause for the pain. This is an uncommon situation since, in most cases, it is not possible to identify that the spondylolisthesis is the sole cause of the back pain.

• Documented progressive subluxation. This is uncommon in adults but is a definite indication for spinal fusion.

In general, the treatment of symptomatic grade I spondylolisthesis by fusion and fixation remains controversial and should be considered on an individual basis. Symptomatic patients with a grade II slip usually benefit from surgery, and symptomatic patients with grade III or IV benefit greatly.

 

 

 

CERVICAL DISK HERNIATION AND SPONDYLOSIS

 

Cervical disc prolapse

Prolapse of an intervertebral disc is less common in the cervical region than in the lumbar area. The disc herniation occurs most frequently at the C6/7 level and slightly less commonly at the C5/6 level. Disc herniation above these levels and at the C7/T1 level is much less common. The predominant frequency of disc prolapse at C6/7 and C5/6 is due to the force exerted at these levels which act as a fulcrum for the mobile spine and head.

Anatomy and pathology

The structure of the cervical disc is essentially the same as in the lumbar region and consists of an internal nucleus pulposus surrounded by the external fibrous lamina, the annulus fibrosus. The role of trauma in the degenerative process and disc herniation is not clear. It is probable that repetitive excessive stresses do exacerbate the normal ageing process and cause disc degeneration. Although it is frequently possible to identify some minor episode of trauma prior to the onset of an acute disc prolapse, a readily identifiable episode of more major trauma as the precipitating event is much less frequent.

The cervical disc prolapse is usually in the posterolateral direction, because the strong posterior longitudinal ligament prevents direct posterior herniation. The posterolateral disc herniation will cause compression of the adjacent nerve root as it enters and passes through the intervertebral neural foramen. Unlike the lumbar region, the nerves pass directly laterally from the cervical cord to their neural foramen, so that the herniation compresses the nerve at that level (Fig. 14.1). The arrangement of the cervical nerve roots and the relationship to the vertebral bodies differ from the lumbar region—the C1 nerve root leaves the spinal canal between the skull (the foramen magnum) and the atlas, and the C8 root, for which there is no corresponding numbered vertebra, passes

through the C7/T1 foramen.

Fig. 14.1 Posterolateral cervical disc prolapse causing compression of the adjacent nerve root.

 

Occasionally a cervical disc may herniate directly posteriorly, causing compression of the adjacent cervical spinal cord which is a neurosurgical emergency.

Clinical presentation

The characteristic presenting features of a patient with an acute cervical disc herniation consist of neck and arm pain and the neurological manifestations of cervical nerve root compression. Although the pain usually begins in the cervical region it characteristically radiates into the periscapular area and shoulder and down the arm (brachial neuralgia). The neck pain commonly regresses while the radiating arm pain becomes more severe. It is usually described as a ‘deep’, ‘boring’ or ‘aching’ pain and the patient is usually severely distressed and debilitated by the discomfort. The distribution of the pain is widespread and conforms to sclerotomes (segmental distribution to muscle and bone) rather than to dermatomes. The patient frequently complains of sensory disturbance, particularly numbness or tingling in the distribution of the dermatome affected. The location of the sensory disturbance is more useful than the pain as an indication of root level: thumb (and sometimes index finger) in C6 lesions, middle finger (and sometimes index finger) in C7 lesions, and little and ring fingers in C8 lesions. The patient may notice weakness of the arm, particularly if the C7 root is affected, as this causes weakness of elbow extension and the movement has only very little supply by other nerve roots (C8). A severe C5 root lesion may cause weakness of shoulder abduction and the patient may complain of difficulty in elevating the arm.

Examination features

Cervical spine movements will be restricted and the head is often held rigidly to one side, usually moderately flexed, and tilted towards the side of the pain in some patients but occasionally away from it in others. Lateral tilt relaxes the roots on the side of the concavity but diminishes the intervertebral foraminae, and flexion slightly separates the posterior part of the intervertebral space and lessens the tension in the prolapse. If the disc herniation is long standing there may be wasting in the appropriate muscle group, particularly the triceps in a C7 root lesion. The patient is then examined for weakness in each of the muscle groups (Tables 14.1 and 14.2). Weakness of elbow extension and finger extension is most commonly caused by a C6/7 prolapse with compression of the C7 nerve root. Less commonly, disc herniation with compression of the C5 root will cause weakness of shoulder abduction, compression of the C6 root will cause mild weakness of elbow flexion, and compression of C8 may cause weakness of the long flexor muscles, triceps, finger extensors and intrinsic muscles.

 

Fig. 14.2 Upper limb dermatome distribution

 

The deep tendon reflexes provide objective evidence of nerve root compression in the following distribution.

• Biceps reflex C5

• Brachioradialis (supinator) reflex C6

• Triceps reflex C7

Sensation should be tested in the arm and hand and the sensory loss will be characteristic for the nerve root involved (Fig. 14.2) although there may be some overlap.

A full neurological examination must be performed and particular care taken to assess the presence in the lower limbs of long tract signs, such as increased tone, a pyramidal pattern of weakness, hyperreflexia or an upgoing plantar response. If there is a cervical disc herniation these features will indicate that it is compressing the spinal cord.

Summary of clinical features

Clinical localization of disc prolapse is possible in most patients with brachial neuralgia due to cervical disc prolapse. The following features are typical (but not invariable) for disc herniation:

C6/C7 prolapsed intervertebral disc (C7 nerve root)

• Weakness of elbow extension

• Absent triceps jerk

• Numbness or tingling in the middle or index

finger.

C5/6 prolapsed intervertebral disc (C6 nerve root)

• Depressed supinator reflex

• Numbness or tingling in the thumb or index finger

• Occasionally mild weakness of elbow flexion.

C7/T1 prolapsed intervertebral disc (C8 nerve root)

• Weakness may involve long flexor muscles, triceps, finger extensors and intrinsic muscles

• Diminished sensation in ring and little finger and on the medial border of the hand and forearm

• Triceps jerk may be depressed.

Differential diagnosis

The clinical features of an acute cervical disc prolapse, with severe neck and arm pain and commonly diminished sensation in the dermatome of the affected cervical root, are so characteristic that in the vast majority of cases the diagnosis is self-evident. The most common cause of radiating arm pain, other than acute prolapse, is spondylosis but, as has been indicated, disc prolapse and spondylosis are aspects of one continuing degenerative process and, in the cervical region, the distinction between them becomes blurred. Other unlikely but possible differential diagnoses include:

• cervical nerve root compression by a spinal tumour (e.g. meningioma, neurofibroma)

• thoracic outlet syndrome

• Pancoast’s tumour infiltrating the roots of the brachial plexus

• peripheral nerve entrapments, such as carpal tunnel syndrome, mediaerve entrapment in the cubital fossa and tardy ulnar palsy

 

Management

Most patients with arm pain due to an acute soft cervical disc herniation achieve good pain relief with conservative treatment. This should include bed rest, a cervical collar, simple analgesic medication, non-steroidal anti-inflammatory medication and muscle relaxants. Manipulation of the neck is potentially hazardous and is contraindicated.

The following are indications for further investigation and surgery.

1 Pain:

(a) continuing severe arm pain for more than 10 days without benefit from conservative therapy

(b) chronic or relapsing arm pain.

2 Significant weakness in the upper limb that does not resolve with conservative therapy.

3 Evidence of a central disc prolapse causing cord compression—this should be investigated urgently.

Radiological investigations

High-quality MRI is now the investigation of choice and has almost completely replaced both myelography and CT (Fig. 14.3). The cervical myelogram using water-based non-ionic iodine contrast material was a most useful investigation for determining the presence and site of the disc herniation (Fig. 14.4). CT scanning by itself is frequently not helpful, but if performed following intrathecal iodine contrast it will demonstrate a disc herniation, and smaller volumes of intrathecal contrast are necessary than with myelography (Fig. 14.5).

Fig. 14.3 MRI of cervical disc prolapse. (a) Cervical axial T1-weighted image (arrow shows disc prolapse). (b,c) Sagittal MRI showing disc prolapse compressing the spinal theca and distorting the cervical cord.

Fig. 14.4 Cervical myelogram showing a posterolateral cervical disc protrusion with compression of the cervical nerve root.

 

Fig. 14.5 CT myelogram showing a posterolateral cervical disc protrusion.

 

Operative procedure

The two most commonly performed operations for cervical disc prolapse are:

1 Cervical foraminotomy with excision of the disc prolapse.

2 Anterior cervical discectomy, with subsequent fusion.

Cervical foraminotomy. This involves fenestration of the bone posteriorly, to provide direct access to the cervical nerve root and disc prolapse. Asmall amount of bone from the lateral margins of the adjacent lamina and articular facets is removed to identify the nerve root in the foramen. Further bone can then be removed from around the nerve root to enlarge the neural canal. The nerve root is gently retracted and the disc herniation excised. The major advantages of the technique are that the nerve is directly decompressed both by removal of the disc herniation and by enlargement of the foramen, and cervical fusion is not necessary. The major disadvantage is the possibility of recurrent disc herniation, but this is very uncommon. In general, the results of the procedure are very satisfactory, with excellent relief of arm pain and, provided the nerve has not been irreparably damaged by long-standing disc herniation, return of full strength to the arm.

Anterior cervical discectomy. This involves an anterior approach to remove the cervical disc and the prolapse. Some surgeons perform formal fusion at the level using bone taken from the iliac crest, bovine bone, artificial bone, or an intervertebral cage, usually filled with bone chips. The fusion may be supplemented by a metal (usually titanium) plate screwed onto the anterior vertebral surface, bridging the disc space. Some surgeons do not perform a formal fusion, as spontaneous fibrous or bony fusion will occur across the disc space provided all the disc has been excised. The major disadvantage is that the fusion will result in additional stress at the adjacent cervical levels, thereby rendering them more prone to degenerative disease.

An anterior approach with disc excision is mandatory for a central disc protrusion.

Postoperative care

Whatever approach is used, the patient is encouraged to mobilize the day after surgery. Asoft cervical collar may be useful in the first week after a foraminotomy to minimize the neck pain. Afirm collar is usually worn for the first 4–6 weeks after anterior discectomy, or until there is evidence of fusion.

The prognosis for pain relief following the operation is excellent provided the diagnosis has been accurate and the nerve decompressed.

 

 

Cervical spondylosis

Cervical spondylosis is a degenerative arthritic process involving the cervical spine and affecting the intervertebral disc and zygapophyseal joints. Radiological findings of cervical spondylosis are present in 75% of people over 50 years of age who have no significant symptoms referable to the cervical spine.

Pathological changes

The degenerative process resulting in cervical  spondylosis and its progression occur in most cases largely as a result of the inevitable stresses and traumas that occur to the cervical spine as a result of the normal activities of daily living. It is probable that the process is aggravated by repetitive or chronic trauma, as may occur in some occupations, and as a result of an episode of severe trauma.

The process principally involves the intervertebral discs and zygapophyseal joints. Reduced water content and fragmentation of the nuclear portion of the cervical discs are natural ageing processes. As the disc degenerates there is greater stress on the articular cartilages of the vertebral end-plates and osteophytic spurs develop around the margins of the disintegrating end-plates, projecting posteriorly into the spinal canal and anteriorly into the prevertebral space.

The degenerative process involving the zygapophyseal joints will also lead to osteophyte formation. The intervertebral foramen may be narrowed by these osteophytes, so causing compression of the nerve root. The osteophyte formation that causes compression of the nerve in the neural foramen, and which is seen around a bulging annulus, is sometimes called a ‘hard disc protrusion’, as distinct from the acute ‘soft’ cervical disc herniation.

The spondylitic process may cause narrowing of the spinal canal as a result of osteophyte formation, particularly the formation of hypertrophic bony ridges at the anterior intervertebral spaces of the spinal canal and hypertrophy of  the ligamenta flavum. This may result in compression of the underlying cord. Such compression is maximal during hyperextension of the neck and may cause cervical myelopathy.

Presenting features

There are three major manifestations of cervical spondylosis, depending on whether there is compressionof a cervical nerve root or the spinal cord.

1 Neck pain.

2 Radiating arm pain.

3 Cervical myelopathy.

Neck pain. This is the most common clinical manifestation of cervical spondylosis and its onset may be precipitated by minor trauma. The pain usually settles over a period of a few days or weeks but frequently recurs and is associated with increasing stiffness of the neck.

Radiating arm pain. Brachial neuralgia (radiating arm pain) results from a nerve root being compressed in the neural foramen by osteophyte formation, with subsequent narrowing of the bony canal. The patient frequently has a history of intermittent neck pain as a result of cervical spondylosis for some months or years, and the onset of the arm pain may be precipitated by an episode of minor trauma. The clinical features are similar to the neuralgia caused by an acute soft disc prolapse, in that the pain radiates diffusely into the periscapular area and shoulder, and into the upper limb in a scleratomal distribution. There may be other features of nerve root compression, including numbness and tingling in the appropriate dermatome distribution, and weakness of the arm. Although the clinical features may be almost indistinguishable from those due to an acute soft disc prolapse, the process is usually not as acute and the patient often has a history of intermittent or chronic pain. Wasting of a muscle group in the appropriate nerve root distribution is more common because of the longer history, but the examination findings will otherwise be similar to those seen with an acute soft disc protrusion.

Cervical myelopathy. This may result from cervical spondylosis causing narrowing of the spinal canal with compression of the underlying spinal cord. The features of progressive weakness and sensory disability are described in.

Radiological findings

Plain cervical spine X-rays (Fig. 14.6) show:

• narrowing of the disc space (the C5/C6 and C6/C7 levels are the most commonly affected)

• osteophyte formation with encroachment into either the spinal canal or neural foramen

• reduced mobility at positions of fusion and increased mobility at adjacent levels.

Fig. 14.6 Cervical spondylosis. There is narrowing of the C5/6 and C6/7 disc spaces, osteophyte formation and a subluxation at the C4/5 level

 

The indications for further radiological investigations depend on the clinical presentation. Although CT scan will clearly show the bony changes seen on the plain cervical spine X-rays, it is not indicated for the investigation of cervical spondylosis which is causing only neck pain. Nerve root entrapment, causing arm pain, is best visualized by high-quality MRI. A CT scan following intrathecal contrast or a cervical myelogram with water-based non-ionic iodine contrast will also show the nerve root compression, but are now only rarely necessary as MRI provides such excellent visualization of the pathology and nerve root compression. The radiological assessment of cervical myelopathy is discussed in

Differential diagnosis

Neck pain

There are numerous possible causes of neck pain, depending on the mode of clinical presentation and the presence of neurological signs in the limbs. The most common cause of neck pain is a minor muscular or ligamentous strain which usually follows minor trauma. If there has been a major injury then a fracture dislocation or acute disc herniation should be considered and excluded. Other rare causes of neck pain are spinal tumours or spinal abscess.

 

Management

Neck pain due to cervical spondylosis

The pain usually resolves with simple conservative measures, including the use of non-steroidal anti-inflammatory medication and simple analgesics. During an acute episode the patient may be more comfortable in a soft cervical collar. As the pain subsides the patient should be encouraged to perform simple mobilizing exercises which may be best undertaken with the supervision of a physiotherapist. If the episodes become frequent and severe the patient may need to consider a change of lifestyle, particularly work practices and recreational behaviour, which might be aggravating the cervical spondylosis.

Arm pain

The symptoms frequently settle with the management described above. The following are indications for surgery.

• Severe pain that does not settle with conservative treatment over 2–3 weeks.

• Chronic or recurrent pain.

• Progressive weakness in the arm which causes functional disability. The most frequently involved nerve root producing significant functional weakness is the C7 root, but the C8 or C5 roots may also result in functional disability as a result of long-standing root compression.

The choice of surgical procedure is similar to that for an acute soft disc prolapse. Cervical foramenotomy, with decompression of the nerve root, excision of the osteophytes and enlargement of the neural foramen, is an effective surgical technique. As the spondylitic process is often at multiple levels, two roots ofteeed to be decompressed. Some surgeons favour an anterior

approach and cervical discectomy with excision of the osteophyte extending into the neural foramen. The decompression is followed by a fusion as described in the previous section on cervical disc prolapse.

 

  

SUBARACHNOID HEAMORRHAGE

 

The sudden onset of a severe headache in a patient should be regarded as subarachnoid haemorrhage until proven otherwise.

Subarachnoid haemorrhage occurs when bleeding is primarily within the subarachnoid space rather than into the brain itself. It represents about 5–10% of all non-traumatic intracranial haemorrhage with an incidence of approximately 15 per 100000 population.

Apoplectic death has been mentioned in the earliest medical writings but its relationship to intracranial haemorrhage and cerebral aneurysm was not established until the latter part of the seventeenth century. The introduction of cerebral angiography by Moniz and Lima in Lisbon in 1927 allowed the diagnosis of cerebral aneurysm to be made in living patients who had sustained subarachnoid haemorrhage. Pioneering surgery in the 1930s and 1940s, by Krayenbuhl in Switzerland and Dandy in North America, showed that aneurysms could be treated operatively, although at that time with considerable morbidity and mortality. Consequent improvements in microsurgical techniques and neuroanaesthesia have considerably improved the safety of surgery.

 

Causes of subarachnoid haemorrhage

The most common cause of subarachnoid haemorrhage in adults is rupture of a berry aneurysm (70%). Subarachnoid haemorrhage in children is much less common than in the adult population and the most common paediatric cause is rupture of an arteriovenous malformation. Rare causes of subarachnoid haemorrhage include bleeding from a tumour, bleeding disorders, blood dyscrasias and rupture of a spinal arteriovenous malformation The aetiology of subarachnoid haemorrhage remains undiscovered in approximately 15% of cases after thorough clinical and radiographic study. These patients often have associated intracranial vascular atherosclerosis and hypertension.

 

Subarachnoid haemorrhage— presenting features

Headache

The sudden onset of a severe headache of a type not previously experienced by the patient is the hallmark of subarachnoid haemorrhage. A relatively small leak from an aneurysm may result in a minor headache, sometimes referred to as the ‘sentinel headache’, as this may be the warning episode of a subsequent major haemorrhage from the aneurysm. Naturally, recognition of a possible minor ‘warning’ haemorrhage is essential to avert a possible later catastrophic bleed, although many are only recognized in retrospect.

Diminished conscious state

Most patients have some deterioration of their conscious state following subarachnoid haemorrhage. This varies from only a slight change when the haemorrhage has been minor to apoplectic death resulting from massive haemorrhage. It is a common cause of sudden death in young adults.

Meningism

Blood in the subarachnoid cerebrospinal fluid will cause the features of meningism—headache, neck stiffness, photophobia, fever and vomiting. Irritation of the nerve roots of the cauda equina, which occurs when the blood extends down to the lumbar theca, may result in sciatica-type pain and low back discomfort.

Focal neurological signs

Focal neurological signs may occur in subarachnoid haemorrhage due to concomitant intracerebral haemorrhage, the local pressure effects of the aneurysm itself, or cerebral vasospasm. A cerebral aneurysm usually lies within the subarachnoid cisterns but the aneurysm may become adherent to the adjacent brain parenchyma due to adhesions, frequently resulting from previous leakage of blood. A haemorrhage from an aneurysm in these circumstances may also extend into the brain and the position of the intracerebral haematoma will determine the type of neurological deficit. A middle cerebral artery aneurysm frequently ruptures into the temporal lobe, resulting in hemiparesis and aphasia if the dominant hemisphere is involved (Fig. 9.1). Anterior communicating artery aneurysms may haemorrhage into the frontal lobes with subsequent akinetic mutism (Fig. 9.2). Defective conjugate ocular movement may result from haemorrhage into a frontal lobe, persistent deviation usually being towards the side of the lesion and purposeful gaze defective away from that side.

Fig. 9.2 Frontal intracerebral haematoma with blood in the Sylvian fissure and ventricles from a ruptured anterior communicating artery aneurysm.

 

Occasionally, an aneurysm may also rupture into the subdural space, resulting in a subdural haematoma and brain compression causing lateralizing neurological signs. An arteriovenous malformation usually lies at least partially within the brain parenchyma, so that when it ruptures intracerebral bleeding is frequently associated with the subarachnoid haemorrhage. Focal neurological signs may result from the position of the aneurysm itself. An aneurysm arising from the internal carotid artery at the origin of the posterior communicating artery (known as a posterior communicating artery aneurysm) may cause pressure on the 3rd cranial nerve. Patients with an enlarging aneurysm in this position may present with features of a 3rd cranial nerve palsy (ptosis, pupil dilatation, extraocular

muscle palsy) prior to a subarachnoid haemorrhage. It is vital that the correct diagnosis of an enlarging cerebral aneurysm is made in this situation, so as to avoid the possible catastrophic effects of subarachnoid haemorrhage. The major differential diagnosis of the aetiology of an apparently isolated 3rd cranial nerve palsy is an ischaemic lesion such as those resulting from diabetes mellitus or atherosclerosis. Pupil size is a useful guide in differentiating between these causes. The pupil is usually dilated, with an expanding aneurysm which compresses the superior aspect of the nerve that contains the parasympathetic pupillary fibres arising from the nucleus of Edinger–Westphal in the midbrain. An expanding aneurysm usually results in more pain than the ischaemia associated with diabetes mellitus, although this is an unreliable guide. If there is any doubt about the cause of the 3rd nerve palsy then angiography must be performed expeditiously. In a patient with impaired conscious state, or in one with other abnormal neurological signs suggesting a massive haemorrhage, 3rd cranial nerve palsy may be secondary to temporal lobe herniation. A giant aneurysm (defined as larger than 2.5 cm in diameter) may cause compression of adjacent neural structures resulting in focal signs (Fig. 9.3). A large aneurysm of the internal carotid artery or anterior communicating artery will cause compression of the optic nerve or chiasm, respectively, resulting in visual failure. Large vertebrobasilar aneurysms may cause brainstem compression.

Cerebral vasospasm following subarachnoid haemorrhage does not usually result in clinical manifestations for 2 or 3 days after the initial bleed so that, although it may be the cause of subsequent focal signs resulting from brain ischaemia, it is not the cause of focal signs immediately after the haemorrhage.

Optic fundi

Mild papilloedema is common within the first few days of haemorrhage because of the sudden elevation of intracranial pressure resulting from hydrocephalus or cerebral oedema. A transient communicating hydrocephalus often occurs after subarachnoid haemorrhage due to blood blocking the arachnoid villi. In about 10% of cases the hydrocephalus persists and is severe enough to require a CSF shunt.

Ophthalmoscopy may reveal fundal haemorrhages, particularly in severe subarachnoid haemorrhage. Small, scattered retinal haemorrhages usually resolve satisfactorily, although the large subhyaloid haemorrhages may break into the vitreous, resulting in permanent visual defect.

 

Clinical assessment

The diagnosis is usually obvious when the history is obtained from the patient, relative or friend. The classic sudden onset of severe headache with features of meningism and decreased conscious state is characteristic of a subarachnoid haemorrhage. However, difficulty may occur when the haemorrhage has been minor and, tragically, a subarachnoid haemorrhage may be misdiagnosed as either migraine or tension headache. A full neurological examination should be performed with particular attention given to the presence of neck stiffness, altered conscious state, pupillary status and fundal haemorrhage. Clinical grading systems have been based on the severity of the headache and neck stiffness and on the level of conscious state. The two major systems are the Hunt and Hess classification and the World Federation of Neurological Surgeons (WFNS) system (Table 9.3).

 

Investigations

The major differential diagnosis is meningitis, although a minor haemorrhage is often misdiagnosed as migraine. Confirmation of the clinical diagnosis of subarachnoid haemorrhage should be undertaken as soon as possible. Computerized tomography (CT) scanning (Fig. 9.4) is the best initial investigation as it will confirm the diagnosis in over 85% of cases. It will also provide additional information on associated pathology such as intracerebral haemorrhage and hydrocephalus, and on the position of the haemorrhage, which is helpful if there is more than one aneurysm. Arteriovenous malformation causing subarachnoid haemorrhage can frequently be diagnosed on the CT scan. If there is any doubt that subarachnoid blood is present on the CT scan, as may occur following more minor haemorrhages, a lumbar puncture is essential. The presence of xanthochromia (yellow staining) in the CSF will confirm subarachnoid haemorrhage.

 

Fig. 9.4 Blood in the Sylvian fissure and basal cisterns indicative of subarachnoid haemorrhage.

 

Cerebral angiography will confirm the cause of the subarachnoid haemorrhage and will determine the subsequent treatment. Intra-arterial digital subtraction angiography has considerably reduced the risks of conventional angiography and should be undertaken as soon as the diagnosis has been confirmed and it is clear that the patient will survive the initial haemorrhage.

 

Cerebral aneurysm

Cerebral aneurysms are the most common cause of subarachnoid haemorrhage in the adult population, with a maximal incidence in the 4th and 5th decades of life, although they can occur at any age.

Surgical anatomy

The great majority of aneurysms arise at the branch points of two vessels, usually at an acute angle, and are situated mainly on the circle of Willis and the trunks of the large arteries which supply it. Afew arise from its immediate branches but aneurysms on peripheral vessels are rare (Fig. 9.5). The majority of aneurysms occur in constant positions on the circle of Willis and about 85% occur on the anterior half of the circle. Aneurysms arise at approximately equal frequency from the internal carotid artery, anterior communicating artery and middle cerebral artery. Those associated with the internal carotid artery most frequently arise at the origin of the posterior communicating artery (the so-called posterior communicating artery aneurysm), less frequently at the terminal bifurcation, and occasionally at the origin of the ophthalmic artery, the anterior choroidal artery or in the cavernous sinus. Middle cerebral artery aneurysms arise from the middle cerebral artery at its bifurcation or trifurcation in the Sylvian fissure (Fig. 9.6). Less commonly an aneurysm may arise from the pericallosal artery at the genu of the corpus callosum.

Fig. 9.5 Usual sites of cerebral aneurysms.

 

   

Fig. 9.6 (a) Anterior cerebral artery aneurysm. (b) Middle cerebral artery aneurysm. (c) Posterior communicating artery aneurysm. (d) Terminal internal carotid artery aneurysm.

 

Approximately 15% of aneurysms arise from the posterior half of the circle of Willis, the most common position being the basilar artery, most frequently at the terminal bifurcation into the posterior cerebral arteries. However, an aneurysm may arise from any of the main branches of the vertebral or basilar arteries, in particular the posterior inferior cerebellar artery, anterior inferior cerebellar artery or superior cerebellar artery (Fig. 9.7).

  

Fig. 9.7 (a) Terminal basilar artery aneurysm. (b) Aneurysm arising from junction of basilar artery and superior cerebellar artery. (c) Posterior inferior cerebellar artery aneurysm.

 

Multiple aneurysms occur in more than one position in approximately 15% of cases.

Pathogenesis of cerebral aneurysms

The common type of cerebral aneurysm resulting in a subarachnoid haemorrhage is a saccular aneurysm, which is also known as a berry or congenital aneurysm. Fusiform aneurysms occur in the intracranial circulation, particularly the vertebrobasilar arteries or internal carotid arteries, and are due to diffuse atheromatous degeneration of the arterial wall, frequently associated with hypertension. Mycotic aneurysms result from septic emboli. They may be situated on peripheral vessels, are frequently multiple and have a high risk of haemorrhage. The saccular or berry aneurysm arises at the junction of vessels where there is a congenital deficiency in the muscle coat. The elastic layer in cerebral arteries, in contrast with arteries elsewhere, is limited to the internal lamina, making these vessels more susceptible to weakening effects of degeneration. Fragmentation and dissolution of the internal elastic membrane occurs at the site of aneurysm development. The combination of the muscle defect and the discontinuity of the underlying internal elastic membrane is probably necessary for the formation of a saccular aneurysm. Other factors that increase the risk of aneurysm formation include atheroma and hypertension. There is an increased incidence of atheroma in the vessels of the circle of Willis and hypertension in patients with ruptured aneurysms. It is probable that these factors play a role in the growth of the aneurysm and its subsequent rupture in some patients.

Related diseases

There is no definite hereditary basis to the development of intracranial aneurysms, although an epidemiology study has shown an increased incidence of approximately seven-fold in first-degree relatives of patients who have had an aneurysmal subarachnoid haemorrhage, with a lifetime risk of 2–5% of developing an aneurysmal subarachnoid haemorrhage. Aneurysms do occur in association with hereditary syndromes such as Ehlers–Danlos syndrome, coarctation of the aorta and polycystic kidney disease.

Management of ruptured cerebral aneurysm

The management of patients following rupture of a cerebral aneurysm is determined by three major factors.

1 Severity of the initial haemorrhage.

2 Rebleeding of the aneurysm.

3 Cerebral vasospasm.

Severity of the initial haemorrhage

About 30% of all patients suffering a subarachnoid haemorrhage from a ruptured aneurysm either have an apoplectic death or are deeply comatose as a result of the initial haemorrhage.

Rebleeding

This occurs in about 50% of patients within 6 weeks and 25% of patients within 2 weeks of the initial haemorrhage. About half the patients that have a subsequent haemorrhage will die as a result of the rebleed. After the first year the risk of a further haemorrhage from the aneurysm is about 2–3% per year.

The only certain way to prevent an aneurysm rebleeding is to exclude it from the circulation. Antifibrinolytic agents (such as epsilon amino caproic acid or tranexamic acid) decrease the risks of rebleeding but, as they are associated with increased incidence of thrombosis (such as deep vein thrombosis and pulmonary embolus) and an increased risk of cerebral thrombosis associated with vasospasm, these agents are now rarely used.

Cerebral vasospasm

Angiographic vasospasm (Fig. 9.8) occurs in about 50% of patients following subarachnoid haemorrhage and in 25% it results in serious neurological complications. There is a direct correlation between the amount of blood noted in the basal cisterns on the CT scan, the risk of developing vasospasm and its severity. Although the spasm may principally affect the vessels most adjacent to the ruptured aneurysm, generalized vasospasm occurs frequently. The clinical manifestations resulting from vasospasm will be determined by the vessels which are most severely affected. Spasm of the internal carotid artery and middle cerebral arteries produces hemiparesis and aphasia in the dominant hemisphere. Vasospasm of the anterior cerebral vessels causes paralysis of the lower limbs and akinetic mutism. Severe vasospasm may cause widespread cerebral ischaemia so that the patient may become obtunded; if the vasospasm is sufficiently severe it will result in death. Vasospasm does not usually occur until 2 or 3 days after the initial haemorrhage and its onset is rarely delayed beyond 14 days.

Fig. 9.8 Spasm of the anterior and middle cerebral arteries following subarachnoid haemorrhage from an anterior communicating artery aneurysm. (initial angiogram, on the 3^rd day and after treatment)

 

Until recently there has beeo satisfactory treatment for established cerebral vasospasm. If the aneurysm has been surgically occluded from the circulation then hypertensive therapy combined with hypervolaemia may overcome the hypoperfusion due to narrowing of the cerebral blood vessels and reverse the ischaemic effects. Calcium channel blocking agents such as nimodopine and nifedipine are frequently used in subarachnoid haemorrhage to prevent and treat vasospasm, although there is still doubt as to their effectiveness.

Following the angiogram that confirms a cerebral aneurysm, a decision is then made as to the definitive treatment of the aneurysm. This will involve either:

• surgery with clipping of the aneurysm or

• endovascular obliteration of the aneurysm.

Surgery for ruptured aneurysm

The timing of the operation is critical in obtaining optimal results following subarachnoid haemorrhage. Although better operative results may be achieved when the surgery is delayed, the longer the operation is deferred the greater the risk that the aneurysm will rebleed. In general, the operation is performed as soon as possible after the cerebral angiogram. In the past surgery was avoided when the patient had clinical or angiographically severe vasospasm, but it is now recognized that it is best to clip the aneurysm even in the presence of clinical or radiological vasospasm as with the aneurysm excluded from the circulation the spasm can be treated using hypertensive hypervolaemic therapy and endovascular techniques.

Surgery is usually not performed on patients who are comatosed or have features of decerebrate posturing response, unless the CT scan shows a large intracerebral haematoma resulting from the ruptured aneurysm which needs to be evacuated, or hydrocephalus as a cause of the poor neurological state.

Preoperative management

In those patients in whom it has been elected for some reason to delay surgery, the management should include careful attention to the following.

• Posture. The patient should lie flat in a quiet room with subdued lighting. Every attempt should be made to avoid environmental situations which could cause sudden elevation of the patient’s blood pressure and thus increase the risk of rupture of the aneurysm. Sedation usingbarbiturates or diazepam may be necessary if the patient is agitated.

• Blood pressure control. The blood pressure is frequently elevated immediately after the haemorrhage and should be carefully controlled. Initially this should be done using intravenous medication and utilizing vasodilating agents (such as hydralazine or glyceryl trinitrate) and betablockers. Although it is essential to control high blood pressure, as this may lead to rupture of the aneurysm, hypotension may result in cerebral ischaemia, particularly when vasospasm is present. The appropriate desirable blood pressure will depend upon the premorbid level.

• Fluids and electrolytes. Correct hydration is essential to avoid electrolyte disturbance; in addition, overhydration may precipitate cerebral oedema and insufficient fluids may increase the risk of cerebral thrombosis associated with vasospasm. Electrolyte disturbances may also occur following subarachnoid haemorrhage due to inappropriate antidiuretic hormone (ADH) secretion, which results in hyponatraemia.

• Pain relief. Simple analgesic medication or codeine phosphate is best used for controlling the headaches resulting from subarachnoid haemorrhage.

Surgical procedures

The surgical procedures available are:

• occlusion of the neck of the aneurysm

• reinforcement of the sac of the aneurysm

• proximal ligation of a feeding vessel.

Haemorrhage from an aneurysm is due to rupture of the fundus of the aneurysmal sac. Therefore, the best surgical procedure is to occlude the neck of the aneurysm, thereby isolating the aneurysm from the circulation.

In brief, the operation involves a craniotomy which is usually based on the pterion (pterional craniotomy) for aneurysms of the anterior circulation. This type of craniotomy may also be used for aneurysms arising from the terminal basilar artery, although some surgeons prefer an approach under the temporal lobe via a temporal craniotomy. Microsurgical techniques, utilizing the operating microscope and microneurosurgical instruments, are employed. Access to the basal cisterns may be aided by withdrawing CSF either using a ventricular drain or from the lumbar theca. The arachnoid around the basal cisterns is opened, the neck of the aneurysm identified and dissected and a clip placed across the neck to exclude the aneurysm from the circulation. During the dissection of the aneurysm it is essential that vital adjacent vessels, including the perforating arteries, are not injured, as damage to these vessels may result in severe neurological disability. Occasionally it is not possible to safely place a clip across the neck of the aneurysm, usually as a result of branches of the parent vessel either arising from the aneurysm or being inseparable from the fundus. In this case the wall of the aneurysm may be reinforced by a number of techniques, including wrapping the wall with crushed muscle, gauze or cotton wool or a combination of these. Rapidly solidifying polymer (aneurysm cement) may be poured around the aneurysm to provide it with a solid covering.

Postoperative management

The usual postcraniotomy operative management applies, with special attention to be given to the neurological state, hydration, posture, oxygenation and blood pressure. Anticonvulsant medication is recommended for 3 months to 1 year. Steroid medication is sometimes used in the initial postoperative course to control cerebral oedema, although its effectiveness is not proven. The major specific postoperative problem results from delayed cerebral vasospasm. As indicated previously, prophylactic calcium channel blocking agents may be of use in preventing this complication. The transcranial Doppler, utilizing non-invasive ultrasound, may give useful information on the degree of intracranial vasospasm. Symptomatic vasospasm can be treated using hypervolaemic hypertensive therapy. This treatment entails careful monitoring and requires the transfer of the patient to an intensive care unit. Recently, endovascular techniques to dilate the vessels in spasm or administer intra-arterial papaverine into the intracranial vessels have been used to treat cerebral vasospasm postoperatively with some success.

Endovascular procedures for ruptured aneurysms

Over the past 10 years endovascular techniques (using detachable coils) have been used to obliterate cerebral aneurysms. These have been investigated in international trials, and have proven to be effective in excluding the aneurysm from the circulation.

The technique is usually performed by a specialist interventional radiologist, and almost always under general anaesthesia. As with surgery, it is recommended that the aneurysm is ‘coiled’ as soon as possible after the angiogram has been performed to confirm the presence of an aneurysm (Fig. 9.9).

  

Fig. 9.9 (a) coils for endovascular treatment of internal carotid artery aneurysm. Figure (c) shows the aneurysm excluded from the circulation following the endovascular insertion of coils.

 

The recent ISAT trial showed the possible superiority of endovascular coiling over surgery, although there has been some debate as to these findings. The decision as to whether an aneurysm should be ‘clipped’ by a surgeon or ‘coiled’ by an interventional neuroradiologist is best made jointly by the treating specialist, cerebrovascular neurosurgeon and neuroradiologist. The interventional neuroradiologist will base his decision on

• the access to the aneurysm and

• the configuration of the aneurysm.

Access to the aneurysm may be impaired by stenosis or tortuosity within the carotid artery (for anterior circulation aneurysms) and vertebrobasilar artery (for posterior circulation aneurysms). The ‘dome to neck’ ratio is an important consideration in deciding whether the configuration of the aneurysm is appropriate for coiling. In general, most neuroradiologists prefer the ratio to be 2 : 1 or greater. New techniques in interventional radiology including the use of stents and three-dimensional coils have increased the number of aneurysms that can be treated by endovascular techniques. At present, over 80% of terminal basilar aneurysms can be treated by endovascular techniques, but only about half of the anterior circulation aneurysms are amenable to ‘coiling’. Most interventional radiologists do not coil middle cerebral artery aneurysms, as there is difficulty in obliterating the aneurysm whilst maintaining patency of the vessels.

Management of an unruptured aneurysm

Multiple aneurysms occur in 15% of patients who present following subarachnoid haemorrhage. In general, an unruptured aneurysm will be clipped at the same time as the surgery for the ruptured aneurysm, provided it can be performed through the same craniotomy. The indications for surgery are controversial for an unruptured aneurysm occurring in a patient who has suffered a subarachnoid haemorrhage from another aneurysm, or for an unruptured aneurysm found incidentally. The debate regarding the optimal management of patients with an unruptured aneurysm revolves around the relative risk of rupture of the aneurysm vs. the risk of treatment, by either surgery or an endovascular approach. In the past  the risk of haemorrhage from an unruptured aneurysm was usually quoted at 2–3% per year.

However, in 1998 the New England Journal of Medicine published a large study of the natural history of unruptured intracranial aneurysms which indicated that the risk of haemorrhage was very much lower, particularly for aneurysms less than 10 mm in diameter and those arising from the middle cerebral artery. There has been considerable debate in the neurosurgical literature regarding the veracity of the so-called ISUIA (International Study of Unruptured Intracranial Aneurysms) study, with some experts questioning the methodology. In general, the risk of rupture will depend on the size of the aneurysm, on the configuration of the aneurysm, in particular if there is a ‘daughter sac’ attached to the fundus, on a positive family history for aneurysmal subarachnoid haemorrhage and on the age of the patient. Symptomatic aneurysms of all sizes should be considered for treatment.

 

 

Arteriovenous malformation

 

The arteriovenous malformation is the most common vascular malformation. Although it accounts for approximately 60% of all subarachnoid haemorrhage in children, by the 3rd decade it is responsible for 20% and by the 5th decade for less than 5%.

Clinical presentation

Haemorrhage. This is the most frequent first symptom of an arteriovenous malformation and, although the bleeding may be subarachnoid, there is commonly an intracerebral component. The arteriovenous fistulous communication results in the development of aneurysms within the lesion, enlargement of the arteries which feed the malformation and, consequently, the possible secondary development of saccular aneurysms on the major feeding vessels. The haemorrhage associated with an arteriovenous malformation may quite often be due to rupture of a saccular aneurysm on the feeding vessel.

Epilepsy. This is the second most common presenting manifestation of an arteriovenous malformation.

Headache. Migraine characteristics are particularly associated with headache due to arteriovenous malformation.

Progressive neurological deficit. For example, a slowly progressive hemiparesis may occur in a large malformation due either to local ischaemia induced by the shunt or to increasing size of the lesion.

Surgical anatomy

Most arteriovenous malformations are situated in the cerebral hemispheres, although they may occur in the posterior fossa involving either the cerebellum or brainstem and they show considerable variation in size. The malformations involving the cerebral hemispheres frequently form a pyramidal mass, the base of which may reach the cortical surface with the apex pointing towards the lateral ventricle. There are frequently multiple, enlarged arteries feeding the malformation and arterialized draining veins extend superficially to the superior sagittal sinus or transverse sinus or deeply into the deep cerebral venous system.

Radiological investigations for arteriovenous malformations (Figs 9.10–9.12)

An arteriovenous malformation is often apparent on the CT scan because of the vivid enhancement of the enlarged feeding vessel and arterialized draining veins after intravenous contrast. Cerebral angiography is best performed using digital subtraction angiographic techniques and is essential for adequate evaluation of the malformation. Precise determination of the position of the major feeding and draining vessels is vital prior to surgery. Magnetic resonance imaging is a valuable aid in determining the exact position of the arteriovenous malformation and the vessels. Preoperative occlusion of accessible major feeding vessels close to the malformation by an interventional radiologist may be useful if the procedure is technically feasible. Aflow-directed catheter is positioned in the artery, which is occluded using cyanoacrylate glue or a polymerizing collagen mixture.

  

Fig. 9.10 (a) The arteriovenous malformation enhances vividly on the CT scan after intravenous contrast and the major dilated feeding vessels can be seen. (b) The MRI shows the position of the malformation in coronal and axial planes and further information about the feeding vessels and draining veins (c).

 

Fig. 9.11 Cerebral angiography (digital subtraction angiogram) demonstrates the vascular anatomy of the arteriovenous malformation. (a) The major feeding vessels are shown on the arterial phase. (b) The draining veins are demonstrated on the venous phase.

 

Management

As with cerebral aneurysms the aim of treatment is to avoid either an initial haemorrhage or rebleed from the malformation. There has been controversy over the risk of haemorrhage and the morbidity and mortality associated with rupture of an arteriovenous malformation. Recent studies have shown that the chance of haemorrhage for both ruptured and unruptured arteriovenous malformations is about 3% each year and that the combined morbidity and mortality of each haemorrhage is at least 40%. However, unlike cerebral aneurysms, haemorrhage from an arteriovenous malformation rarely causes symptomatic vasospasm.

Surgical excision, provided it is technically feasible and would not result in a disabling neurological deficit, should be performed if the malformation has haemorrhaged. Unruptured arteriovenous malformations should be considered for excision if surgery is unlikely to produce significant neurological deficit.

Surgery for arteriovenous malformations

The principles of the operation involve isolation and occlusion of the principal feeding arteries followed by meticulous dissection of the malformation, with occlusion and division of the numerous small feeding vessels. The draining veins should be ligated only after all the feeding vessels have been occluded, since premature obstruction to the arterialized venous outflow will result in a precipitous swelling and rupture of the vascular mass.

The surgical management of giant arteriovenous malformations is fraught with considerable risk. The lesions may be surrounded by chronically ischaemic brain ‘steal’ by the malformation and abrupt occlusion of the shunt through the malformation has led in some cases to oedema and haemorrhage in the adjacent brain, a phenomenon first described by Spetzler and which was called the ‘normal perfusion pressure breakthrough’ theory. Methods that have been employed to avoid this complication include preoperative and intraoperative embolization and staged excision of the malformation.

The use of radiosurgical techniques, involving either the gamma knife (a highly focused cobalt source of irradiation) or stereotactic radiosurgery using a linear accelerator, has been advocated for the treatment of small (less than 3 cm diameter), unruptured and surgically inaccessible arteriovenous malformations with complete angiographic obliteration in greater than 80% of lesions with a diameter of 3 cm or less at 3 years after radiation. However, as the radiotherapy effect is slow, the patient remains at risk from haemorrhage for some years.

 

Vein of Galen malformation

This unusual malformation results when arteries feed directly into the vein of Galen and produces distinct clinical syndromes depending on the age at which the disease presents.

• Neonates present shortly after birth with cyanosis and heart failure due to the shunt through the malformation.

• Infants and young children present with seizures and hydrocephalus due to obstruction of the cerebral aqueduct.

• Adults may present with multiple subarachnoid haemorrhage.

 

 

 

STROKE

 

Stroke is the third most common cause of death in most Western countries and the commonest cause of chronic adult disability. In many Western countries, there has been an impressive fall in population-based stroke mortality over the past few decades, averaging 4–5% each year. This has been chiefly attributed to the more effective recognition and treatment of hypertension and other risk factors. Despite this progress, with the increasing life expectancy of the population, a marked increase in stroke prevalence has been predicted. Stroke is generally a disease of ageing, but young adults are also affected, with a somewhat different pathogenetic spectrum. The overall approach to stroke has undergone a dramatic change in recent years, with important recent advances in prevention strategies, the widespread introduction of acute stroke units, the application of new imaging technologies and the introduction of thrombolysis for selected patients with acute ischaemic stroke.

The term ‘stroke’ is used to describe a suddeeurological deficit of vascular aetiology lasting more than 24 hours. A transient ischaemic attack (TIA) indicates a transient neurological deficit of vascular origin lasting less than 24 hours, although many patients with TIAs lasting more than minutes have in fact suffered some neuronal damage and this time definition has been recently challenged. Stroke is classified as cerebral infarction or ischaemic stroke, signifying ischaemic brain damage, or cerebral haemorrhage, where the primary pathology involves vascular rupture and extravasation of blood into the surrounding tissues. The term ‘haemorrhagic infarction’ is used to describe an infarct into which there has been a secondary extravasation of blood. Although subarachnoid haemorrhage (SAH) may not be associated with a focal neurological deficit, it is usually categorized as a stroke subtype.

Stroke prevention

Stroke prevention involves primary and secondary strategies. Primary prevention includes lifestyle modification and treatment of risk factors in individuals who have not experienced cerebrovascular symptoms. Risk factor management can be categorized into the high risk approach (detecting and treating patients at high risk of stroke, such as those with atrial fibrillation or hypertension) and the mass or population approach (such as reducing salt intake and hence attempting to lower blood pressure in the entire population).

Secondary prevention involves the use of strategies in a symptomatic individual after a stroke or TIA, generally tailored to the specific type of cerebrovascular pathology. Most stroke prevention studies have focused on a reduction in the incidence of stroke, neurological disability and other vascular endpoints. Recently, prevention of vascular dementia has also been recognized as an important additional goal.

Primary prevention

Primary prevention strategies target the modifiable risk factors for stroke (Table 10.1).

 

Secondary prevention

Secondary prevention strategies after stroke or TIA, unlike the primary prevention techniques, are tailored to the underlying stroke pathology. The range of secondary prevention strategies continues to expand (Table 10.2). These include the introduction of a number of new antiplatelet strategies, proof of the efficacy of warfarin ion-valvular atrial fibrillation, clarification of the indications for carotid endarterectomy and the introduction of cerebral angioplasty/stenting.

 

Carotid endarterectomy

Two large trials (the North American Symptomatic Carotid Endarterectomy Trial—NASCET and the European Carotid Surgery Trial—ECST) showed major benefits for carotid endarterectomy over optimal medical therapy in patients with greater than 70% carotid stenosis and either TIA or non-disabling stroke. In the NASCET study, an absolute risk reduction of 17% over 18 months was achieved, indicating that one stroke could be prevented for every six patients.

   

carotid endarterectomy

 

Cerebrovascular angioplasty/stenting

Percutaneous transluminal angioplasty is increasingly used for symptomatic and asymptomatic carotid stenosis, usually combined with endovascular stenting. However, there is limited proof of efficacy and safety compared with endarterectomy. One trial showed that the benefits and risks of surgery and angioplasty/stenting were approximately equivalent. Large trials are now being conducted in patients with symptomatic carotid stenosis, comparing stenting with endarterectomy. Distal protection devices, which trap embolic debris at the time of the procedure, represent an important advance. Stenting has also been used in small series of patients with symptomatic intracranial stenoses, in whom optimal medical therapy has failed.

 

Acute stroke

The spectrum of transient ischaemic attacks and stroke

Transient ischaemic attacks (TIAs) and completed cerebral infarcts are caused by similar pathological mechanisms, most commonly large vessel atherosclerotic disease, cardioembolism and small vessel lacunar disease. Patients with TIAs and completed infarcts, whether large or small, have a similar prognosis, with a 5–10-fold annual increase in stroke risk. Both conditions should be regarded as medical emergencies. While TIAs by convention last less than 24 hours, most last only minutes. The majority of TIAs lasting more than 1–2 hours produce tissue damage on sensitive brain imaging techniques, such as magnetic resonance imaging. The old 24-hour definition is therefore increasingly criticized and is not clinically useful. The recognition of patients with minor ischaemic deficits presents a vital opportunity for prevention of major stroke. Patients with TIAs should be urgently evaluated within 24 hours of the episode. Investigations would typically include a CT or MR scan to detect infarction or non-vascular pathology, carotid duplex Doppler to diagnose major carotid disease, and ECG, sometimes followed by echocardiography, to diagnose atrial fibrillation or another cardioembolic source.

Carotid-territory TIAs

These are due to transient ischaemia in the retina or cerebral hemisphere. Transient monocular blindness (‘amaurosis fugax’) is due to a transient reduction in retinal perfusion produced by embolism or haemodynamic failure. The patient often describes a shade pulled down over one eye. In clinical practice it is vital to determine whether a visual disturbance is truly monocular, indicating retinal ischaemia, or binocular, often implicating the vertebrobasilar circulation. Hemispheric symptoms most commonly consist of transient dysphasia and varying degrees of hemiparesis or hemisensory disturbance, either singly or in combination.

Vertebrobasilar TIAs

These are often more complex than carotid territory events and usually include two or more of the following symptoms:

• binocular visual disturbance

• vertigo

• diplopia

• ataxia

• bilateral weakness or paraesthesiae

• deafness

• tinnitus

• amnesia.

These symptoms are produced by transient ischaemiaof the brainstem, occipital and medical temporal lobes and upper spinal cord.

Classification and pathogenesis of stroke

Cerebral infarction (ischaemic stroke)

Cerebral infarction accounts for approximately 80% of stroke patients and may be classified according to anatomical location or pathogenesis. It is useful to incorporate both classifications when considering stroke in a particular patient.

Anatomical classification

The anatomical location refers to the specific arterial territory (e.g. internal carotid vs. vertebrobasilar, anterior cerebral vs. middle cerebral) or specific location within the brain (e.g. lateral medullary syndrome, ventral pontine infarction or internal capsular infarction). Infarction most commonly occurs in the middle cerebral arterial territory and can be classified as cortical or deep (subcortical). The cortical middle cerebral syndromes depend on whether a small branch has been occluded, or whether one or both of the main two divisions of the middle cerebral artery is involved, the superior or inferior division. Subcortical infarcts occur in the territory of the deep perforating vessels supplying the internal capsule, thalamus, basal ganglia and brainstem. The occlusion of a single perforating vessel produces a small deep infarct, less than 1.5 cm in diameter, called a lacunar infarct, particularly if associated with one of the five classical clinical syndromes (see below). The obstruction of the origins of several of the deep perforating branches can produce a larger subcortical infarct termed a striatocapsular infarct.

Pathogenetic classification

Greater emphasis is now placed on the pathogenesis of cerebral infarction, as this is useful for the selection of secondary prevention therapies. This classification is often referred to as the TOAST system, after the TOAST trial.

1 Large artery atherosclerosis.

2 Cardiogenic embolism.

3 Lacunar infarction.

4 Rare causes (e.g. dissection, vasculitis, prothrombotic states).

5 Unclassified:

• despite adequate investigation

• due to inadequate investigation.

Large artery atherosclerosis (Figs 10.1–10.3)

The development of extracranial atherosclerotic plaque produces a progressive arterial stenosis. Subsequent plaque complications include ulceration, intraplaque haemorrhage and superimposed platelet–fibrin thrombus formation. Stroke is most often due to the development of thrombus (Fig. 10.4) followed by propagation and distal thromboembolism into the intracranial vessels, sometimes embolism composed of atheromatous debris, or haemodynamic failure due to the reduction of cerebral perfusion in the arterial border zones (borderzone or watershed infarction). Primary intracranial atherosclerosis and atherothrombosis is rare in Caucasian populations, but more common in African, African-American and Asian stroke patients (Fig. 10.5).

Clinical features include demonstration of relevant arterial pathology with 50% or greater stenosis and the absence of a cardiac source. Anterior circulation infarcts typically involve the cerebral cortex. Prodromal TIAs in the same arterial territory are another pointer

.

Fig. 10.1 Arterial digital subtraction angiogram demonstrating severe, proximal internal carotid artery stenosis .

 

 

Fig 10.2. carotid duplex ultrasound: high-grade stenosis (a) and occlusion (b) of internal carotid artery

 

Fig. 10.3 Diffusion-weighted imaging scan (left image) showing large acute middle cerebral artery (MCA) cortical infarct. Magnetic resonance angiography (right image) shows lack of flow in the left MCA.

 

Cardiogenic embolism

Avariety of cardiac diseases affecting the cardiac walls, valves or chambers can lead to cerebral embolism. These include:

 • non-valvular atrial fibrillation (the most common)

• valvular heart disease

• myocardial infarction with ventricular thrombus formation

• post-cardiac surgery (valvular surgery or coronary artery bypass grafts)

• prosthetic cardiac valves

• infective endocarditis

• atrial myxoma

• cardiomyopathy

• septal defect with paradoxical embolism.

Clinical features include delineation of a cardiac source and lack of evidence of large artery disease. Similarly, the cerebral cortex is usually involved.

Lacunar infarction (Fig. 10.7)

The occlusion of single deep perforating arteries supplying the internal capsule, basal ganglia or brainstem can lead to the development of small lacunar infarcts. These are most commonly the result of hypertensive disease, which produces localized arterial wall pathology, termed lipohyalinosis, in these small penetrating arteries, or localized microatheroma. Lacunar infarcts are less often due to embolism from a proximal source such as extracranial atherosclerosis or intracardiac thrombus.

Fig. 10.7 Diffusion-weighted imaging scan showing acute left thalamic lacunar infarct (hyperintense lesion).

 

Classical lacunar syndromes include pure motor hemiparesis, pure sensory stroke, sensorimotor stroke, ataxic hemiparesis and the dysarthria/clumsy hand syndrome. Clinical pointers include clinical diagnosis of one of the classical syndromes, usually exclusion of a large artery or cardiac source and ideally neuroimaging confirmation of a small, deep infarct.

Oxfordshire classification

Another commonly used stroke classification, termed the Oxfordshire classification, divides ischaemic stroke into TACI (total anterior circulation infarction), PACI (partial anterior circulation infarction), POCI (posterior circulation infarction) and LACI (lacunar infarction). This classification is also useful and the subtypes correlate with prognosis.

 

 

Cerebral haemorrhage (haemorrhagic stroke)

 

Cerebral haemorrhage is generally classified into intracerebral and subarachnoid haemorrhage.

Intracerebral haemorrhage (Figs 10.9–10.10)

Non-traumatic (primary) intracerebral haemorrhage is most commonly due to hypertension, which leads to rupture of deep perforating arteries in the putamen, thalamus, central white matter, brainstem and cerebellum. The precise mechanism of this vascular rupture is uncertain, but may be related to the development of small Charcot–Bouchard microaneurysms on the vessel walls of these end-arteries, or direct rupture of vessels affected by lipohyalinosis.

Fig. 10.9 CT scan showing hypertensive putaminal haemorrhage.

 

 Fig. 10.10 CT scan showing frontal and occipital lobar haemorrhages in a patient with amyloid angiopathy.

 

‘Lobar’ haemorrhage refers to superficial vascular rupture within the cerebral lobes, outside these deep arterial territories. It is sometimes due to an underlying structural lesion, such as an arteriovenous malformation, cerebral aneurysm, tumour, vasculopathies or coagulation disorders. Amyloid angiopathy is an important cause of lobar cerebral haemorrhage in elderly patients and is due to amyloid deposition in the walls of the cerebral arteries. These haemorrhages may be multiple and typically occur in patients who are normotensive and may show features of Alzheimer’s disease.

Clinical clues to ICH include the features of a sudden rise in intracranial pressure with depressed conscious state, headache and vomiting. The mortality is much higher than in ischaemic stroke. However, patients with ICH may be surprisingly alert and well looking. Conversely, patients with ischaemic stroke may have early depression of conscious state. Hence, neuroimaging, usually with CT, is mandatory in all cases to rapidly diagnose ICH.

Subarachnoid haemorrhage  is classified according to pathological cause and site. The two most important identifiable causes include rupture of a berry aneurysm and arteriovenous malformation, but in up to 15% of cases no bleeding can be identified at angiography. Some of these idiopathic bleeds are due to perimesencephalic haemorrhage.

 

Modern principles of acute stroke management

Key principles of acute stroke management include:

1 Urgent recognition of stroke symptoms by the patient or their carer.

2 Urgent ambulance transport to a hospital with adequate diagnostic facilities and organized stroke care.

3 Urgent triage and investigation in the emergency department including CT brain scanning.

4 Assessment for acute stroke therapy, particularly thrombolysis.

5 Admission to a specialized stroke unit.

Clinical assessment of stroke

The following questions should be considered in the management of any patient with a presumed stroke.

• Is it a stroke?

• Is it an infarct or haemorrhage?

• Is the patient eligible for thrombolytic therapy or other urgent intervention?

• What is the arterial or anatomical localization and pathogenesis?

Stroke and pseudostroke

Non-vascular pathologies (‘pseudostroke’) such as cerebral tumour, subdural haematoma, abscess, migraine, metabolic disturbances and epilepsy can mimic the stroke process. All patients with suspected stroke require an urgent CT or MR scan to exclude non-cerebrovascular disorders, as well as to differentiate between infarct and haemorrhage (Figs 10.8 and 10.9). Lumbar puncture is reserved for those cases where meningitis is considered (usually after a CT scan) or where the diagnosis of subarachnoid haemorrhage is still contemplated after a normal CT scan.

The distinction between infarct and haemorrhage

The distinction between cerebral haemorrhage and infarction is vital, as some haemorrhages are considered for surgical evacuation, while patients with ischaemic stroke may be considered for thrombolysis or anticoagulation. While there are clinical pointers (see above) this differentiation is usually based on CT scan findings. Although CT scanning remains the workhorse for acute stroke assessment, recent studies indicate that MRI is at least as sensitive for intracerebral haemorrhage as CT and far more sensitive for acute ischaemia. Patients with ischaemic stroke often have early infarct changes on CT, although these may be subtle. MRI with diffusionweighted imaging (DWI) is increasingly used as this technique allows a sensitive diagnosis of cerebral ischaemia (Figs 10.3 and 10.7).

Is the patient eligible for thrombolysis?

The thrombolytic agent tissue plasminogen activator (tPA) has now been licensed in most parts of the world as the first proven stroke drug therapy, given intravenously within 3 hours of stroke onset in selected patients with ischaemic stroke. The approval of this acute therapy followed the positive results of a two-part pivotal trial, conducted in the USA. Other European trials testing tPAup to 6 hours have shown a marked trend to benefit over risk, and meta-analysis confirms the 3-hour window for tPA. Use of tPA increases the risk of symptomatic haemorrhagic complications by three- to fourfold. Major early infarct changes on CT, for example greater than one-third of the area of the middle cerebral artery, are associated with a higher risk of haemorrhagic transformation. Up to 10% of ischaemic stroke patients can be treated in well-organized centres. In contrast to the tPAtrials, three trials evaluating the role of intravenous streptokinase produced negative results, chiefly linked to the substantial risk of intracerebral haemorrhage associated with the drug.

Direct infusion of thrombolytics via intra-arterial catheters has been shown to be effective in one trial up to 6 hours after middle cerebral artery occlusion. There is interest in experimental mechanical devices which can break up thrombi, with a much lower risk of cerebral haemorrhage.

Location and pathogenesis of infarction

Cortical infarcts (Fig. 10.3). Based on the clinical examination, a distinction should be made between an infarction in the carotid or in the vertebrobasilar territory. With regard to carotid territory infarction, the presence or absence of cortical signs—dysphasia, apraxia, anosognosia (unawareness or denial of the stroke), sensory, motor or visual agnosia (inattention), acalculia, right/left confusion, dysgraphia or cortical sensory loss (loss of two-point discrimination, astereognosis, dysgraphaesthesia)—suggests an embolic source from either the extracranial vessels or the heart, rather than lacunar infarction.

Subcortical infarcts (Fig. 10.7). As indicated earlier, lacunar infarcts (less than 1.5 cm in diameter) rely on diagnosis of one of the classical lacunar syndromes. Cortical signs are not present. Lacunar syndromes reflect small vessel occlusions in the internal capsule, thalamus and brainstem.

Haemorrhage

Intracerebral haemorrhage (Fig. 10.9). As previously discussed, the rapid onset of a stroke with early depression of conscious state favours the diagnosis of a primary intracerebral haemorrhage. Primary intracerebral haemorrhage and aneurysmal subarachnoid haemorrhage can overlap in their clinical presentations. For example, a berry aneurysm can rupture primarily into the brain parenchyma, presenting as an intracerebral haemorrhage, whereas a primary brain haemorrhage can rupture directly into the ventricular system and present with marked meningeal features due to subarachnoid blood.

 

Urgent assessment in the emergency department

Rapid triage of suspected stroke patients should be performed in an emergency department, with skilled medical evaluation and urgent investigations. These involve blood tests, including a blood glucose measurement to exclude hypoglycaemia (which can mimic acute stroke), and an ECG to diagnose atrial fibrillation or acute myocardial infarction, which can reveal the cause of cerebral embolism. Most importantly, a CT brain scan must be performed urgently in all patients to differentiate between cerebral infarction and cerebral haemorrhage. In addition, CT scanning is essential to exclude the other brain pathologies that can simulate stroke. As noted above, many centres are now using acute MRI with DWI and magnetic resonance angiography (MRA). Computed tomographic angiography (CTA) is another useful tool. Duplex Doppler scanning is of value in the diagnosis of large vessel atherosclerosis, while echocardiography (usually less urgent) can aid in the diagnosis of intracardiac thrombi and valvular or cardiac wall kinetic abnormalities. Transoesophageal echocardiography is superior to transthoracic echocardiography.

Acute stroke units

One of the most important developments in acute stroke management in recent years has been the proven value of stroke units, based on the results of clinical trials which have compared organized expert care in a special unit to the management of patients in general medical wards. The usual stroke unit model involves a geographical area in the hospital, incorporating a skilled multidisciplinary stroke team, led by a neurologist or other physician with expertise in stroke management. Vascular surgeons and neurosurgeons should be readily available for consultation and intervention in selected cases. In a systematic overview of the benefits of stroke units, it was shown that mortality could be reduced by about 25%, also with evidence of reduced disability. In addition, stroke units have been found to reduce bed stay and hence hospital costs.

The components of team management in the stroke unit include:

1 Acute medical, surgical and nursing care.

2 Diagnosis of the pathological mechanism of the stroke and the institution of tailored secondary prevention strategies.

3 Prevention, early detection and treatment of complications such as aspiration pneumonia, pressure sores, hyperglycaemia, seizures and sepsis.

4 Use of measurement instruments and stroke registers.

5 Early integrated neurorehabilitation with evaluation of premorbid status and therapy goals.

6 Involvement, education, and support for patient and family.

7 Early, coordinated discharge planning.

Acute medical care

Three key, evidence-based advances include the use of tPA, aspirin (see below) and stroke unit care. In the acute phase, close monitoring of vital and neurological signs is paramount, given that about a third of stroke patients deteriorate after admission to hospital. Cardiac monitoring is useful for many acute stroke patients. Initial clinical evaluation should involve assessment of the patient’s function and clinical state before the stroke, the stroke type and pathogenesis, documentation of the nature and severity of neurological deficits, and comorbid diseases. Early mobilization, range of motion exercises for hemiplegic limbs, frequent turning, fluid and nutritional maintenance, dysphasia management, avoidance of aspiration, prevention of deep venous thrombosis (DVT) and pneumonia, management of incontinence, treatment of urinary tract infections and other causes of fever, and maintenance of skin integrity are all key planks in the team treatment of the acute stroke patient.

Patients should have oximetry, but there is no evidence of the value of routine supplemental oxygen by mask or nasal prongs. Patients should be well hydrated using normal saline rather than glucose-containing solutions, because of the hazards of even mild degrees of hyperglycaemia. In general, blood pressure should not be acutely lowered, because this can compromise cerebral perfusion in acute stroke. Hypertension is usual in acute stroke and this usually settles spontaneously over 2–3 days. We routinely use compression stockings and usually low-dose heparin, or low molecular weight heparin or heparinoid, in DVT prophylaxis. Airway assessment should be an urgent priority to avoid aspiration pneumonia. We generally use nasogastric feeding after 24–48 hours if the patient’s bulbar function is compromised.

Adverse prognostic factors include advancing age, depression of conscious state, severity of neurological deficit, conjugate gaze palsy and early urinary incontinence. Causes of mortality in stroke patients are predominantly neurological (transtentorial herniation) in the 1st week, and due to secondary systemic factors in the 2nd and 3rd weeks such as pneumonia, pulmonary embolism and cardiac causes.

Progressing stroke

A deteriorating neurological deficit is seen in about one-third of stroke patients. Cerebral oedema, with progressive elevation of intracranial pressure, is an important cause of death. However, this oedema is generally cytotoxic and clinical trials have demonstrated that corticosteroids are of no value in either cerebral infarction or haemorrhage. Intravenous mannitol and glycerol are sometimes empirically used, but their value has not been proven. In highly selected young patients with severe, early brain oedema, surgical decompression with hemicraniectomy should be considered.

Heparin

Heparin has been the most widely used unproven therapy in most countries. The International Stroke Trial (IST) evaluated unmonitored, subcutaneous heparin up to 48 hours after stroke onset and showed that a slight reduction in recurrent stroke was offset by an increased risk of haemorrhagic transformation. The rate of early, recurrent embolism in patients with atrial fibrillation was much lower in recent trials than in a number of earlier clinical studies.

Systematic overview of the available evidence leads to the conclusion that heparin is not generally indicated for most patients with acute ischaemic stroke, but heparin should be considered for selected patients with nondisabling ischaemic stroke and a very high risk of recurrent embolism.

Acute aspirin

Two large trials (the International Stroke Trial and the Chinese Acute Stroke Trial) both showed that, as for acute myocardial infarction, aspirin administered within 48 hours of stroke onset produced a modest improvement in outcomes at 6 months. Hence, aspirin should be used routinely in acute ischaemic stroke, unless thrombolysis is being used.

Neuroprotective therapies

A complex cascade of biochemical changes occurs in stroke, secondary to the initial ischaemia. Ischaemic brain injury is associated with elevated levels of the excitatory neurotransmitters glutamate and aspartate. These lead to excessive stimulation of the N-methyl D-aspartate (NMDA) receptor on the cell surface. This activation is followed initially by an influx of sodium and water into the cells and secondly by a sudden rise in intracellular calcium. Arange of neuroprotective compounds has been designed to inhibit various points in the excitotoxic cascade. These include calcium channel and NMDAantagonists, glutamate release inhibitors, glycine antagonists, free radical scavengers, inhibitors of the neutrophil influx into the ischaemic region and various growth factors. To date, none of these compounds have proven effective in adequately powered, Phase III clinical trials, but there are several ongoing studies. Other approaches include the combination of thrombolysis with neuroprotective drugs.

Cerebral hemorrhage

While routine surgical evacuation of haematoma is unproven, we consider evacuation in selected patients with cerebral haemorrhage, particularly in the cerebellum, as well as younger patients with lobar haemorrhage. The general principles of acute stroke management apply equally to intracerebral haemorrhage as to infarction.

Prevention of recurrent stroke—secondary stroke prevention

Patients with symptomatic high-grade carotid stenosis should be considered for subacute carotid endarterectomy. While surgery is awaited, or if endarterectomy is inappropriate, antiplatelet therapy should be instituted. In cardioembolic stroke, there is uncertainty as to the optimal timing of anticoagulation, particularly in patients with atrial fibrillation. Our approach is to employ heparin acutely if the patient has a mild deficit and there is a high risk of recurrent embolism. Many patients with atrial fibrillation are commenced on warfarin 7–10 days after onset, without prior heparin, because of the risk of haemorrhagic transformation. Lacunar infarcts are less commonly embolic and generally have a good prognosis.

 

 

 

 

 

 

FACIAL PAIN SYNDROMES

 

 

Facial pain may result from local pathology involving the face, mouth, jaw, temporomandibular joint, paranasal sinuses or salivary glands, or it may be due to distinct pain disorders such as trigeminal neuralgia, glossopharyngeal neuralgia and postherpetic neuralgia. These specific pain entities are relatively uncommon but the clinical manifestations are stereotyped so that a diagnosis should be apparent.

Trigeminal neuralgia

Trigeminal neuralgia consists of excruciating paroxysmal pain, which lasts for seconds to minutes, in the distribution of the 5th cranial nerve. It was described by Avicenna 900 years ago and the term ‘tic douloureux’ was applied by André in 1756. Charles Bell demonstrated the anatomical basis for sensation in the face in the 1820s and distinguished the sensory component of the trigeminal

nerve from the motor function of the facial nerve, consequently defining an anatomical basis for trigeminal neuralgia. It is estimated that it occurs in about 1 in every 70 000 people.

Aetiology

There is some controversy concerning the precise aetiology of trigeminal neuralgia. The microvascular compression theory is popular and postulates that the 5th cranial nerve is compressed at the brainstem junction by a vascular loop. In 1934 Dandy first proposed that trigeminal neuralgia was caused by the nerve being compressed and distorted by the superior cerebellar artery, andthis theory of microvascular compression was extended by Gardner, at the Cleveland Clinic, to form the basis of hemifacial spasm due to pressure on the 7th cranial nerve. The concept has been popularized by Jannetta, who proposed that trigeminal neuralgia is the result of compression of the root entry zone, which is a junctional area between the central and peripheral myelin on the nerve adjacent to the brainstem. However, others suggest that the pain is due to central dysfunction in the brainstem in structures related to the nucleus of the 5th nerve, or pathology within the gasserian ganglion.

Trigeminal neuralgia may occasionally present as a symptom of multiple sclerosis, which should therefore be considered as a cause in patients under 40 years of age.

In approximately 3% of cases there may be a mass, such as a meningioma, epidermoid or arteriovenous malformation, in the posterior fossa. This mass distorts the nerve and produces pain similar to trigeminal neuralgia

 

Clinical features

The main clinical feature is the sudden, severe pain that lasts for a moment and then goes, leaving nothing behind—except the fear of its return. Shaving, talking, eating, washing or even a cold wind may disturb the skin and trigger a paroxysmof pain which is so severe that the patient is immobilized in agony.

The particular characteristics of trigeminal neuralgia are as follows.

• The pain is strictly limited to one or more branches of the trigeminal nerve. It most commonly affects the 2nd and/or 3rd division.

• The pain is sudden and short lived, usually lasting seconds, or at the most, minutes.

• The pain is frequently provoked by light mechanical stimuli within the trigeminal area. In particular, it is often ‘triggered’ by touching the side of the face, or is brought on by facial movement, such as chewing. These patients are often unable to shave and they shield their faces when outside in the wind.

• There is no detectable abnormality of trigeminal nerve function.

The incidence of trigeminal neuralgia reaches its maximum between the ages of 50 and 70 years, is very rare below the age of 25 and is uncommon under the age of 35. The pain affects the territory of the 2nd and 3rd divisions of the trigeminal nerve with equal frequency, and may involve both territories simultaneously. The area of the 1st division of the trigeminal nerve is involved less frequently. In about 5% of cases the neuralgia affects both sides of the face, but not usually simultaneously, so that each bout of pain remains strictly unilateral. Bilateral trigeminal neuralgia occurs more commonly in patients with multiple sclerosis.

Remissions of the pain are frequent and may last for months or even years; occasionally complete freedom from the pain occurs. There are no physical signs. The patient may present with a scarf shielding the head and will talk from the corner of the mouth so as not to precipitate a spasm of pain. If the pain has been very severe the patient may be emaciated and dehydrated from being unable to eat or drink and the face may be dirty and unshaven from fear of precipitating an attack of pain.

Investigations

MRI of the brain should be performed to exclude a mass in the cerebellopontine angle in the posterior fossa or intrinsic brainstem lesion such as demyelination, especially in younger patients.

Differential diagnosis

The pain of trigeminal neuralgia is characteristic but must be differentiated from:

• atypical facial pain

• pain of dental origin, such as malocclusion or dental abscess

• pain from the temporomandibular joint

• postherpetic neuralgia

• migrainous neuralgia (cluster headache).

Treatment

Management of a patient with trigeminal neuralgia may involve the use of a number of treatment modalities including:

• drugs

• local procedures on peripheral branches of the trigeminal nerve

• percutaneous procedures involving the trigeminal ganglion or the retrogasserian rootlets

• posterior fossa craniotomy procedures.

Drugs

Carbamazepine initially relieves the pain in the great majority of patients although doses of 200-mg tablets up to 4–5 times a day are ofteecessary for adequate pain control. However, the patients frequently have a relapse of pain and need further treatment. In addition, many patients are unable to tolerate the side-effects of carbamazepine which occur at the doses necessaryto control the discomfort. The most frequent adverse reactions are dizziness, drowsiness, unsteadiness, nausea and vomiting. Haemopoietic complications due to bone marrow depression occur rarely. Other drugs that can be tried include phenytoin, baclofen and clonazepam, although they are not as effective.

Procedures involving peripheral branches of the trigeminal nerve

Infraorbital or supraorbital nerve section may be performed in the uncommon situation of the pain being localized to the area in the distribution of these nerves. However, the pain frequently recurs and these procedures should probably be limited to the elderly frail patient.

Percutaneous thermocoagulation

Percutaneous thermocoagulation of the retrogasserian rootlets or ganglion of the trigeminal nerve can result in analgesia in selected areas of the trigeminal distribution. In this procedure a needle is passed percutaneously, under X-ray control, through the foramen ovale into the ganglion and nerve roots just behind the ganglion in Meckel’s cave. The nerve rootlets and ganglion are heated with a radiofrequency current, which results in a differential loss of pain sensation but retention of light touch sensation. Alternatively, glycerol may be injected into Meckel’s cave so as to bathe the retrogasseriaerve rootlets. Although these procedures have a high initial success in relieving pain, they may produce facial numbness and the trigeminal neuralgia frequently recurs. The procedures may be repeated when the pain recurs or alternative treatments may be considered.

Posterior fossa craniotomy procedures

Total or partial trigeminal nerve section. Trigeminal root section, by either a posterior fossa craniotomy or a middle cranial fossa approach (Frazier’s operation), used to be a common procedure for trigeminal neuralgia but is now almost obsolete. Section of the nerve results in facial numbness and the morbidity may be quite disabling, particularly if the ophthalmic division supplying the cornea is affected. However, a partial section of the posterior half of the nerve causes only relatively minor disturbance of facial sensation and may result in lasting pain relief for trigeminal neuralgia involving the 2nd and/or 3rd divisions. An uncommon, but feared, disabling complication of nerve section is a painful dysaesthesia of the face, ‘anaesthesia dolorosa’, for which there is no treatment. Anaesthesia dolorosa only rarely results from percutaneous radiofrequency rhizotomy.

Microvascular decompression. This is now the procedure of choice. The operation is performed via a small retrosigmoid posterior fossa craniotomy using the operating microscope. The compressive vessel, most commonly the superior cerebellar artery, is dissected away from the 5th cranial nerve at the brainstem entry junction and the nerve is then shielded from the vessel by a small patch of sponge. Over 90% of patients have an initial complete relief of pain, although about 10–15% have some relapse of trigeminal neuralgia over the next 5 years.

Summary of treatment

There are a number of methods of treating trigeminal neuralgia and the treatment chosen will frequently depend on the patient’s preference when the various options are explained. In general, carbamazepine is used first. If the medication is not tolerated, or when the pain relapses, the main choice is between a radiofrequency percutaneous rhizotomy or a posterior fossa craniotomy and microvascular decompression. Unless the patient is elderly and very frail, microvascular decompression is the preferred option, as it has the greatest chance of producing permanent relief of pain with no facial numbness.

 

Glossopharyngeal neuralgia

Glossopharyngeal neuralgia is much less common than trigeminal neuralgia, there being approximately one case for every 50 of trigeminal neuralgia. It was first defined as a clinical entity by Harris in 1921. It is characterized by intense attacks of pain in the distribution of the glossopharyngeal nerve and the auricular and pharyngeal branches of the vagus nerve.

Aetiology

The precise cause of glossopharyngeal neuralgia is unclear, although Janetta proposed the theory of microvascular compression of the 9th nerve, as for trigeminal neuralgia and the 5th cranial nerve.

Presenting features

The patient presents with attacks of severe pain involving the throat, tongue or ear. The pain may start anywhere in the territory of the glossopharyngeal nerve or auricular and pharyngeal branches of the vagus nerve. The tonsil, root of the tongue and ear are common sites and the pain often extends into the base of the jaw and the neck. At times the pain may be confined to the throat and occasionally only the ear is involved. In some patients the pain involves the area of the mandibular division of the trigeminal nerve, which may lead to a wrong diagnosis. The attacks are frequently induced by talking, swallowing or chewing, and consequently, in severe cases, the patient may become cachectic. Occasionally, an episode of throat pain precipitated by swallowing may be associated with bradycardia, hypotension and syncope.

Differential diagnosis

The distribution of the pain will distinguish glossopharyngeal neuralgia from trigeminal neuralgia. Geniculate neuralgia, described by Hunt, is rare and involves the sensory component of the facial nerve (nervus intermedius). Geniculate neuralgia has two major forms, one affecting the ear, with secondary radiation into the deep structures of the face, the other involving primarily the deep facial structures.

Treatment

Patients with glossopharyngeal neuralgia may derive benefit from treatment with carbamazepine, although with less effect than for trigeminal neuralgia. However, surgery for glossopharyngeal  neuralgia is straightforward and effective. The operation involves a small posterior fossa craniotomy with section of the 9th nerve and the upper 10% of the fibres of the vagus nerve. The sensory loss resulting from these nerve sections results io disability. Some surgeons advocate microvascular decompression as for trigeminal neuralgia, but the nerve section operation is effective and the microvascular decompression may require manipulation of the lower cranial nerves resulting in morbidity.

 

Postherpetic neuralgia

Herpes zoster may involve the distribution of the trigeminal nerve, particularly the ophthalmic division. In a manner similar to shingles involving the trunk or limbs, postherpetic neuralgia occurs more frequently in elderly patients. The pain, usually in the distribution of the ophthalmic division, is severe, constant and unremitting, and is described as ‘burning’ or a ‘crawling’ sensation under the skin. The diagnosis is usually obvious by the herpetic rash. Occasionally, however, the rash may be minor and barely noticeable. There is no surgical treatment for postherpetic neuralgia of the trigeminal nerve and sensory root section is of no benefit. Carbamazepine may alleviate some of the discomfort, although unfortunately its benefit is usually limited. There is some evidence that the early use of steroids and acyclovir in patients presenting with herpes zoster may reduce the risk of postherpetic neuralgia.

 

Atypical facial pain

Facial pain which has no pathological basis is relatively common and most frequently affects middle-aged females. The pain presents a diagnostic problem which can often only be solved after underlying pathology has been excluded by clinical and radiological investigations. The pain is usually situated in the central portions of the face or cheek and is described as boring, dull or aching. The lancinating paroxysms of pain characteristic of trigeminal neuralgia and glossopharyngeal neuralgia are absent. Dental malocclusion and pain from the temporomandibular joint, Costen’s syndrome, should be excluded.

 

 

Hemifacial spasm

Hemifacial spasm is a facial disorder that is not painful, but its proposed aetiology is so similar to trigeminal neuralgia that. The condition is characterized by unilateral spasms of the facial muscles supplied by the facial nerve.

Aetiology

The aetiology is similar to that proposed for trigeminal neuralgia and the microvascular compression theory postulates that the 7th cranial nerve is compressed at the brainstem junction by a vascular loop, usually an artery. Gardner advocated this theory in the 1960s and it has been popularized by Jannetta who proposed that, as for trigeminal neuralgia and the 5th cranial nerve, hemifacial spasm is due to pulsatile compression at the root exit zone of the 7th cranial nerve, which is a junctional area between the central and peripheral myelin where the 7th nerve leaves the brainstem. Very uncommonly, hemifacial spasm is associated with a compressive mass such as an epidermoid, aneurysm or meningioma. Occasionally, hemifacial spasm and trigeminal neuralgia may coexist in the same patient (known as ‘tic convulsif’).

Clinical features

The onset of hemifacial spasm usually commences in middle or old age and there is a slight female predominance. The spasms usually commence around the orbicularis oculi muscles and subsequently spread down the face to involve the other facial muscles innervated by the facial nerve. The spasms are episodic and are frequently precipitated by emotional distress, chewing, talking or laughing. The condition causes the patient considerable social embarrassment and the spasms of the orbicularis oculi result in eye closure, making driving difficult. In contrast to trigeminal neuralgia, where there is no clinical evidence of 5th cranial nerve dysfunction, there is frequently minor facial weakness between the episodes of spasm. Otherwise, there are no neurological findings.

Management

The diagnosis is self-evident, with the spasms being located on one side of the face. In the very early stages hemifacial spasm needs to be differentiated from simple blepharospasm, but this is confined to the muscles around the eye and is usually bilateral. An MRI should be performed to exclude the unlikely possibility of a posterior fossa mass lesion causing the condition. There is currently no lasting effective medical treatment. Injections of botulinum toxin into the  affected muscles have limited, transient success, but need to be repeated every few months.

At present the only long-term effective treatmentis surgical and the operation is a microvascular decompression of the 7th cranial nerve. However, as the condition is benign and painless the principal indication for operation is social embarrassment. In many patients the hemifacial spasm is so annoying and socially distressing that they are keen to proceed with an operation, bearing in mind its possible risks. Surgery is definitely inappropriate if the patient is not troubled by the spasm.

The microvascular decompression is performed through a small posterior fossa craniotomy and, using the operating microscope, the vessel, often the anterior inferior cerebellar artery, compressing the 7th nerve at the brainstem  junction is carefully mobilized away from the nerve. The nerve is then protected from the vessel by a small patch of sponge. The operation is usually highly effective in relieving the spasm. There is a small risk of unilateral hearing loss due to the proximity of the 8th nerve and its blood supply. As the operation involves a craniotomy, often in elderly patients, there is a small risk of serious complication, mostly as a result of cerebrovascular complications. This possibility should temper an obvious enthusiasm for an effective operation.

 

 

 

 

SURGERY OF PAIN

 

 

Pain is the most common symptom in patients presenting to a neurosurgeon; in fact it is often the only symptom that the patient will complain of. The features of the pain are often characteristic of the particular underlying disease; these features include:

• mode of onset

• pattern of the pain—continuous or intermittent

• duration

• position of the pain

• quality of the pain

• features that alleviate or exacerbate the pain.

There are three major clinical groups of pain problems.

1 Benign specific pain syndromes.

2 Benign non-specific pain syndromes.

3 Cancer pain.

Mechanisms of pain

There is no ‘pain centre’ in the brain—such a concept would be quite inadequate to account for the complexity of pain. There are three major psychological–anatomical–physiological components to pain which aid in the understanding of the mechanisms of pain and in treating patients. These are:

1 sensory–discriminative

2 motivational–affective

3 cognitive–evaluative.

Fig. 19.1 Pathways that mediate pain and temperature.

 

Sensory–discriminative dimension

The sensory–discriminative dimension involves the spatial, temporal and magnitude properties of pain and is subserved mostly by neospinothalamic projections to the ventrobasal thalamus and then to the somatosensory cortex (Fig. 19.1). The pain pathways are described in  The receptors for pain consist of unencapsulated endings of peripheral nerves. The neural responses are mediated through the myelinated A-delta and unmyelinated C fibres. Pain may be felt as two waves, separated by a very short interval. The first is sharp and localized, with conduction along group A fibres. The second wave, which is rather diffuse and more disagreeable, depends on the slower conduction of group C fibres. The cell bodies are in the dorsal root ganglia. Their axons traverse the dorsal roots and enter the dorsolateral fasciculus (tract of Lissauer) of the spinal cord, in which ascending and descending branches travel for one or two segments. These fibres, which give off many collateral branches in their short course, terminate in the substantia gelatinosa of the dorsal grey horn. The substantia gelatinosa consists of Golgi type II neurones whose axons are either confined to the nucleus or run for short distances in the tract of Lissauer, connecting adjacent regions of the substantia gelatinosa. Axons of the tract cells in the chief nucleus of the dorsal horn cross the midline in the ventral commissure and then course rostrally in the lateral spinothalamic tract. Fibres are continually being added to the ventromedial aspect of the lateral spinothalamic tract. At the upper cervical levels fibres from the sacral segments are dorsolateral, followed by fibres from lumbar and thoracic segments, while fibres from the cervical segments are in the ventromedial position. The fibres ascend through the brainstem, supplying inputs to the reticular formation and the superior colliculus, before terminating in the nuclei of the thalamus, particularly the intralaminar, ventral posterolateral (VPL) and posterior nuclear complex. There is a somatotopic representation of the opposite side of the body in the lateral portion of the thalamic nucleus. Tertiary neurones then project to the primary and secondary sensory area in the cerebral cortex.

Pain fibres from the head enter the pons through the sensory root of the trigeminal nerve and turn caudally in the trigeminal spinal tract, the spinal tract of V, which extends to the upper cervical levels. Terminals of the spinal tract of V form synapses in the adjacent nucleus, the spinal nucleus of V. Axons of the spinal nucleus of V cross to the opposite side and ascend as the ventral trigeminothalamic tract to the ventral posteromedial (VPM) nucleus of the thalamus, as well as to the intralaminar nuclei. The fibres then pass to the somatosensory cortex. There is a spatial arrangement of fibres in the sensory root and spinal tract corresponding to the divisions of the trigeminal nerve. Ophthalmic fibres in the sensory root are dorsal, mandibular fibres are ventral and the maxillary fibres are between these. Because of rotation of fibres as they enter the pons, the mandibular fibres are dorsal and the ophthalmic fibres ventral in the trigeminal spinal tract. The dorsal part of the spinal trigeminal tract includes pain and temperature fibres from the facial, glossopharyngeal and vagus nerves, which may supply areas of the external ear, lining of the auditory canal, tympanic membrane, posterior tongue, pharynx and larynx.

Motivational–affective dimension

The motivational–affective dimension component of pain is involved with the aversive quality of pain, which provides the unique, distinctly ventromedial position. The fibres ascend through the brainstem, supplying inputs to the reticular formation and the superior colliculus, before terminating in the nuclei of the thalamus, particularly the intralaminar, ventral posterolateral (VPL) and posterior nuclear complex. There is a somatotopic representation of the opposite side of the body in the lateral portion of the thalamic nucleus. Tertiary neurones then project to the primary and secondary sensory area in the cerebral cortex.

Pain fibres from the head enter the pons through the sensory root of the trigeminal nerve and turn caudally in the trigeminal spinal tract, the spinal tract of V, which extends to the upper cervical levels. Terminals of the spinal tract of V form synapses in the adjacent nucleus, the spinal nucleus of V. Axons of the spinal nucleus of V cross to the opposite side and ascend as the ventral trigeminothalamic tract to the ventral posteromedial (VPM) nucleus of the thalamus, as well as to the intralaminar nuclei. The fibres then pass to the somatosensory cortex. There is a spatial arrangement of fibres in the sensory root and spinal tract corresponding to the divisions of the trigeminal nerve. Ophthalmic fibres in the sensory root are dorsal, mandibular fibres are ventral and the maxillary fibres are between these. Because of rotation of fibres as they enter the pons, the mandibular fibres are dorsal and the ophthalmic fibres ventral in the trigeminal spinal tract. The dorsal part of the spinal trigeminal tract includes pain and temperature fibres from the facial, glossopharyngeal and vagus nerves, which may supply areas of the external ear, lining of the auditory canal, tympanic membrane, posterior tongue, pharynx and larynx.

Motivational–affective dimension

The motivational–affective dimension component of pain is involved with the aversive quality of pain, which provides the unique, distinctly afferent stimulation can influence pain perception is accepted. The theory proposes that neural mechanisms in the dorsal column of the spinal cord act like a ‘gate’, which can either increase or decrease the flow of nerve impulses from the periphery to the central nervous system. The input from the sensory nerve fibres can be modulated by the gate before evoking the perception of pain and the person’s response. The relative activity of the large diameter A-beta fibres and the smaller diameter of the A-delta and C fibres influence the gate to either increase or decrease the sensory transmission (Fig. 19.2).

Fig. 19.2 The gate control theory of pain as proposed by Melzack and Wall. Excitatory (white circle) and inhibitory (black circle) links extend from the substantia gelatinosa (SG) to the transmission cells (T) as well as descending inhibitory control from the brainstem systems. All connections are excitatory except the inhibitory link from SG to T. The round knob at the end of the inhibitory link implies that its action may be presynaptic, postsynaptic or both.

 

To this proposed mechanism of pain can be added the central pathways that relate to the three major dimensions of pain. In addition, the midline raphe nuclei of the brainstem have connections with the periventricular and periaqueductal areas and their axons descend to the spinal cord through the dorsolateral fasciculus. These axons terminate in the dorsal horn, where they modify the responses to painful stimuli. Opioid peptides (endorphins) are the neurotransmitters involved in these mechanisms.

 

Benign specific pain syndromes

There are numerous benign pain syndromes that have a specific, well-recognized pathological basis. The more common syndromes presenting ieurological and neurosurgical practice are:

• Head pain. Headache due to raised intracranial pressure, dural irritation, migraine or occipital neuralgia.

• Facial pain due to trigeminal neuralgia, disorders of the temporomandibular joint or sinusitis.

• Upper limb pain, most commonly due to cervical nerve root compression from a cervical disc prolapse, carpal tunnel syndrome or thoracic outlet syndrome.

• Pain involving the trunk in a dermatome distribution due to thoracic nerve root inflammation or compression, due to shingles (herpes zoster) or tumour.

• Lower limb pain due to sciatica or lumbar canal stenosis.

These clinical problems are discussed in the relevant chapters. The treatment is specific and, in general, effective. The success of the treatment depends on an accurate diagnosis and appropriate management.

There are two specific benign pain syndromes that present to neurosurgeons: causalgia (reflex sympathetic dystrophy) and phantom limb pain. These problems have perplexed neuroscientists and neurosurgeons as to the aetiology of the pain and its treatment. Both are types of deafferentiation pain, in which the pain occurs as a result of injury to an afferent nerve.

Reflex sympathetic dystrophy syndrome

Reflex sympathetic dystrophy (RSD) is also known as complex regional pain syndrome (CRPS), and is a multisymptom pain syndrome that usually affects one or more extremities. The pain syndrome follows injury to a nerve which may be so slight that the patient may not even recall having received an injury. For reasons poorly understood, the pain develops due to aberrent functioning of the sympathetic nervous system. Although the syndrome may follow a very minor nerve injury, first symptoms may also develop following major nerve damage, as documented clinically, the condition has been known as causalgia. The terms complex regional pain syndrome (CRPS) type 1 and type 2 have been in use since 1995, when the International Association for the Study of Pain (IASP) considered that the names ‘reflex sympathetic dystrophy’ and ‘causalgia’ were not sufficient to represent the full spectrum of the symptoms and signs of the syndrome.

The diagnosis of RSD/CRPS is made in the context of a history of trauma to the affected area, associated with pain that is disproportionate to what would be expected from the trauma plus one or more of the following:

• abnormal function of the sympathetic nervous system

• swelling

• movement disorder

• changes in tissue growth (dystrophy and atrophy).

The clinical features of RSD/CRPS include the following.

• Pain, which is described as severe and persistent, often with a burning and pleasant quality, and which spreads beyond the territory of the injured nerve or nerves. It is aggravated by physical and emotional stimuli. Pain usually involves the hand or foot, but may spread through the affected limb.

• Changes to the skin, which appears shiny, dry or scaly. The patient may have a sensation of warmth or coolness in the affected limb (vasomotor changes) and the skin may show increased sweating (pseudomotor changes).

• Swelling with pitting or hard oedema, that is usually diffuse and localized to the painful region.

• Movement disorder, due to the patient havingdifficulty moving the limb because of the pain; in addition there appears to be a direct inhibitory effect of RSD/CRPS on muscle contraction.

Initially the RSD/CRPS symptoms are generally localized to the site of injury, but as time progresses the features become more diffuse. X-rays may show wasting of the bone (patchy osteoporosis).

The mechanism by which an injury triggers abnormal function of the sympathetic nervous system is unclear. There is no laboratory test constituting definitive proof of the syndrome, but sympathetic block can be helpful both in confirming the diagnosis and as a therapeutic option.

Treatment

Treatment involves the following.

• Education and encouraging normal use of the limb using physical therapies, including the useof a TENS (transcutaneous electrical nerve stimulation) machine.

• Minimizing pain with medications that include non-steroidal anti-inflammatory agents, antidepressants, anticonvulsants (e.g. carbamazepine, gabapentin, sodium valproate) and simple analgesic agents. Oral opioids have been advocated, but are not recommended due to potential hazards including addiction.

• Asympathetic nerve block may be therapeutic, providing either a permanent cure or partial remission and will also help in confirming the diagnosis.  If there is a significant decrease in pain following the sympathetic block a definitive sympathetic ablation can be undertaken.

Other therapeutic measures are controversial but include the use of spinal cord stimulation.

 

Phantom limb pain

Phantom limb pain is the perception of a painful sensation in an extremity that has been amputated.

Virtually all amputees have phantom sensations but only a small percentage have disabling pain in the phantom limb. Pain in the stump of the limb due to local factors is common and must be differentiated from true phantom limb pain, although they may be related.

The cause of phantom limb pain is unknown. It may develop immediately after the injury or at any stage up to some years later. The pain may result from deafferentation of the dorsal horeurones and more rostral structures, although environmental and affective factors do play a role in the patient’s pain behaviour and influence the disability.

The management of this problem is particularly difficult. It involves a careful assessment of the environmental and psychological factors that may affect the patient. Numerous treatments have been tried, including various types of physical therapies, analgesic medication, antidepressants, minor tranquillizers, anticonvulsants (carbamazepine) and psychological treatments including hypnotherapy and psychotherapy.

Many neurosurgical ablative procedures, such as cordotomy, dorsal rhizotomy, neurectomy and sympathectomy, have been tried without success.

The dorsal root entry zone (DREZ) operation has been used with some initial success in the treatment of phantom pain. The operation involves destruction of the zone where the dorsal root fibres enter into the spinal cord, usually by thermocoagulation.

 

Benign non-specific pain syndromes

Patients with chronic pain that does not have an underlying specific pathological cause are frequently referred to a neurosurgeon for assessment and management. The pain problems may involve any region of the body but there are a number of particularly common types of clinical presentation.

• Head—headache.

• Face—atypical facial pain.

• Upper limb—non-specific arm pain.

• Spine—non-specific neck, thoracic or low back pain.

• Lower limb—diffuse leg pain.

Many of the patients who present may have a structural, organic basis for a component of the pain problem, but the clinical manifestations are far more extensive than can be explained by any pathological changes that can be demonstrated by either clinical or radiological findings. In some cases the presenting pain problem may just be a marked exaggeration of a true organic problem. In others, the presenting features will bear no relationship at all to any recognized clinical abnormality. Detailed questioning may reveal that the patient ‘gains’ from the pain and that this gain may be either psychological or involving definite material benefit for the patient. Unfortunately, pending litigation is a real and often powerful conscious or subconscious motive for the continuation or exaggeration of symptoms.

Management

The management of these patients generally involves the following.

• Exclude an organic basis for the complaint. This will involve detailed history and examination and radiological investigations. It is absolutely vital that the clinician should objectively assess the patient thoroughly. Patients with neurological disorders will often present with atypical clinical manifestations early in the disease process. It is wise, and very helpful, to reassess the patient at a subsequent examination to be certain there is not an organic basis for the presenting complaint. It is important not just to dismiss a patient as being disagreeable, eccentric or having an odd personality, as they may also have an organic problem which may or may not bear relationship to their underlying personality trait.

• The clinician should assess the possibility of any psychological origins for the pain and the ocial background of the patient. Reassurance is often all that is necessary. For example, frequently a patient may present with chronic headaches and, if it becomes apparent that a friend or relative died recently from a brain tumour, all the patient requires is reassurance that they do not have a tumour. Unfortunately many of the problems are not this simple and more detailed counselling or psychiatric advice may be necessary.

• Maintain a positive mental attitude. Chronic, non-specific benign pain problems are debilitating for the patient and the various doctors involved. It is all too easy just to dismiss the patient and hope the problem will fade away as the patient disappears from sight. The patient has often sought numerous opinions and usually has a negative attitude about themself, their pain and the medical profession. It is helpful if the doctor can give positive advice, reassure the patient there is no serious underlying disease, encourage

a positive mental attitude and be optimistic that the pain will resolve.

• Never use addictive medications. In particular it is essential never to resort to the use of narcotic analgesia, as this will inevitably make a difficult problem disastrous.

 

 

Cancer pain

The successful relief of pain in a patient suffering from cancer is one of the major challenges of neurosurgery.

For many patients not only is the diagnosis of cancer associated with an enormous sense of grief and anxiety, but their greatest fear is that they will suffer severe pain during the illness. The two common misconceptions are that all cancer is painful and that cancer pain cannot be relieved. It is essential that the patients are reassured early in their illness that any pain they develop will be relieved.

The basic principles of the management of cancer pain are:

• Explanation, reassurance and counselling.

• Modification of the pathological process. Bone metastases are the main cause of pain in the majority of patients with carcinoma of the kidney and thyroid and in multiple myeloma. Modification of the pathology by surgery (e.g. oöphorectomy for carcinoma of the breast, orchidectomy for carcinoma of the prostate), radiotherapy, chemotherapy or hormonal treatment should be considered in consultation with an oncologist.

• Elevation of the pain threshold. Reduction of anxiety and improvement of a depressed mood will help to elevate the pain threshold. Considerable benefit may result from admission to hospital or a specialized unit (palliative care unit or hospice unit), even for a short time. Adequate assessment and control of pain may permit patients to return home. A feeling of security leads to reduced anxiety which can lessen pain and improve other symptoms.

• Appropriate analgesic medication.

• Neurosurgical techniques.

Pharmacological agents in cancer pain  management

There is a concept of an ‘analgesic ladder’, which involves moving from weak to strong analgesic drugs, with appropriate adjuvant therapy wheecessary, until pain is controlled. These adjuvants, or coanalgesics, which may include antiemetics, antidepressants and corticosteroids, can be of great value in potentiating the primary analgesics. However, they may at the same time compound the side-effects, either by interfering with the pharmacology of the primary analgesics or by exacerbating a primary side-effect, such as sedation, of these analgesics.

The first choice is aspirin or an aspirin-like drug. These drugs provide excellent analgesic, anti-inflammatory and antipyretic effects. An alternative to aspirin is paracetamol, which has a similar antipyretic and analgesic activity but only a weak anti-inflammatory effect. The major advantage of both these drugs is the absence of unwanted side-effects, such as those exerted by the opiates on the CNS.

Codeine phosphate is a popular, short-acting, mild narcotic which may be useful in pain not adequately controlled by simple analgesics. The aim of the use of narcotic analgesics is to control the pain with a minimum of side-effects, preferably by the oral route. The narcotic should be ‘titrated’ to a dose that will alleviate the pain. Morphine is the most commoarcotic drug. Oral morphine is very satisfactory, provided the dose is carefully adjusted to suit the individual  patient. Its oral bioavailability is approximately one-third that of the parenteral use and this must be taken into consideration when changing patients from one route to the other. Oral medication should be a regular 4-hourly dose. Longer-acting forms of slow-release oral morphine that can be administered twice daily are often the preferred narcotic for patients with debilitating cancer pain.

The major disadvantage of oral or parenteral narcotic medication is the side-effects, particularly drowsiness and nausea.

Oxycodone hydrochloride can be administered in a shortor long-acting form and is especially useful for bone pain, and in those patients not tolerating morphine. Antiepileptic drugs such as sodium valproate and gabapentin are effective in the treatment of neuropathic pain.

 

Neurosurgical techniques for pain control

Neurosurgical procedures will interfere with one or more of the psychological–anatomical–physiological pathways described previously. Although, in general, neurosurgical procedures are only performed when the patient has continuing unrelieved pain despite the best medical treatment, some techniques are simple and are worth undertaking so that the dose of analgesia can be diminished.

The major neurosurgical techniques are:

• Nerve section. This is the time-honoured neurosurgical tool, although it has only a limited place in the control of cancer pain. Occasionally it may be of use when the tumour infiltrates a peripheral nerve. Section of the cranial nerves in the posterior fossa may relieve the pain of an infiltrating head and neck tumour, although these patients are often severely debilitated and the necessary multiple nerve section may further increase the morbidity.

• Spinal cordotomy. Cordotomy involves section of the lateral spinothalamic tract and can be performed either by open operation or percutaneously at the C1/2 level. Although a high cervical cordotomy may initially control pain in the upper limb the effect is often transient. Unfortunately it has only a limited place in the control of cancer pain, as it will control pain satisfactorily on only one side of the body, usually in the lower limb. Unfortunately, it is rare for cancer pain to be this well localized. Bilateral cordotomy has a high morbidity and will not control pain if it is diffuse.

• Spinal cord stimulation. Epidural spinal cord stimulation has been used for the treatment of non-malignant chronic pain syndromes for nearly 30 years. The effectiveness of the technique is controversial, but has been especially used for management of chronic back and extremity pain. The exact mechanism by which spinal cord stimulation works is unclear but it has been postulated that the large fibres (tactile positions and vibratory sensation) have a lower threshold of activation and can be recruited selectively by electrical stimulation, thereby closing  the ‘gate’ for pain signals originating from the peripheral nervous system (as proposed by Melzack and Wall). An electrode array is implanted extradurally and attached to an implanted pulse generator. The potential effectiveness of the technique can be trialled for each particular patient by implanting a temporary electrode prior to insertion of the definitive system.

• Sympathectomy. A percutaneous chemical or surgical sympathectomy is a potent method of relieving pancreatic pain due to carcinoma but it is disappointing for benign pancreatic pain.

• Intracerebral procedures. Cerebral procedures, such as deep brain stimulation, thalamotomy and leukotomy, are now only rarely indicated in the control of pain.

• Deep brain stimulation (DBS) is a treatment of last resort for a highly selected population of patients with chronic pain but has been used with some success in the treatment of central and deafferentation pain including phantom pain, thalamic pain and anaesthesia dolorosa. It has also been used for peripheral neuropathic pain and nociceptive pain. DBS does not work well for recurring acute pain and is not generally effective for cancer pain, but may have a small role for cancer pain in sites which are difficult to treat by destructive procedures.

The preferred targets for deafferentation pain are sensory thalamus (ventroposteromedial (VPM) and ventroposterolateral (VPL), or the internal capsule (IC)); and for peripheral nociceptive or neuropathic pain the periaqueductal grey matter (PAG) or periventricular grey (PVG). However, there is cross-over of effect between these two sites. Two electrodes can be placed through the same burr hole, contralateral to the main pain, or on the non-dominant side for bilateral pain. Unilateral PVG or PAG stimulation may control bilateral pain, but if thalamic (or internal capsule) stimulation is required for bilateral pain then bilateral electrodes may be required. Ahigh response rate for pain of peripheral origin and for deafferentation pain of up to 60% has been reported but a long-term overall success rate of only around 30%.

Chronic electrical stimulation of the septal area, the Kölliker–Fuse nucleus and the motor cortex has also been used to treat central supraspinal pain and trigeminal neuropathic pain with promising results, although these techniques remain experimental. Chronic electrical stimulation of the trigeminal nerve root has been tried for intractable facial pain, including anaesthesia dolorosa, with about 50% of patients reporting at least a 50% reduction in pain. The use of DBS for pain may decrease in the future, as a greater understanding of the neuropharmacologyof pain has resulted in improved pharmacotherapy for chronic pain.

• Subarachnoid opiate administration. Most cancer pain can be effectively controlled with oral, suppository or subcutaneous infusion administration of opiates. Lumbar intradural subarachnoid administration of morphine is particularly useful in patients with terminal cancer pain whose pain is unrelieved by oral, subcutaneous or suppository administration, or who do not tolerate the side-effects of the high doses of narcotics necessary to control the pain. The technique allows very small doses of narcotic to be given directly into the subarachnoid space and avoids many of the unpleasant side-effects of high-dose narcotic administration. Opiate receptors have been identified in the brain and spinal cord. The receptor density is high in the periventricular structures such as the amygdala, caudate, putamen, medial thalamus and habenular, in the periaqueduct grey matter, and in the floor of the 4th ventricle. The greatest concentration of receptors in the spinal cord is in the substantia gelatinosa. These receptors are the likely synaptic site of action for local terminals, which release endogenous compoundswith actions similar to opioid alkaloids (endorphins), and also for the injected subarachnoid morphine.

The basic technique of lumbar intradural opiate administration involves the insertion of a catheter into the subarachnoid space of the lumbar theca. The catheter is threaded subcutaneously to the anterior abdominal or chest wall, where it is connected to a subcutaneous reservoir. The morphine can be injected directly into the reservoir, using meticulous sterile technique because of the risk of infection. Alternatively, infusion pumps can be implanted subcutaneously, filled with morphine and joined to the spinal catheter. Their major disadvantage is the expense of the pump.

Injection of morphine through the lumbar catheter will result in pain relief in most sites of the body, although it is less successful for pain involving the head, neck and upper limbs. In these situations an intraventricular catheter, with a subcutaneous reservoir, can be inserted for morphine administration.

There is a small risk of respiratory depression and the patient should be observed closely following the initial doses. If a subcutaneous reservoir is implanted the treatment regime usually commences with 0.5 mg morphine twice daily. The patient should fill in a pain chart which will document the level of pain throughout the day; the intrathecal morphine can be increased as necessary. The pain is usually satisfactorily controlled with a dose of morphine of between 1 and 10 mg/day. Supplementary oral narcotic or non-narcotic medication can also be used. The major complications are infection of the catheter, which may lead to meningitis, and blockage of the catheter.