SPINAL CORD AND ROOTS

Disorders localised to the spinal cord or nerve roots are detailed below, but note that many diffuse neurological disease processes also affect the cord (see Section V, e.g. multiple sclerosis, Friedreich’s ataxia).

SPINAL CORD AND ROOT COMPRESSION

As the spinal canal is a rigidly enclosed cavity, an expanding disease process will eventually cause cord and/or root compression.

Causes

Manifestations of cord or root compression depend upon the following:

Site of lesion within the spinal canal: an expanding lesion outside the cord produces signs and symptoms from root and segmental damage.

ROOT – lower motor neuron (l.m.n.) and sensory impairment appropriate to the distribution of the damaged root.

Lesions within the cord (intramedullary) produce segmental signs and symptoms.

SPINAL CORD AND ROOT COMPRESSION

Level of the lesion: a lesion above the L1 vertebral body may damage both the cord and its roots. Below this, only roots are damaged.

Vascular involvement: neuronal damage from mechanical stretching is of less importance than the vascular effects. At first venous obstruction leads to vasogenic oedema, but eventually impaired arterial flow causes irreversible spinal cord infarction. Clinical findings may suggest cord damage well beyond the level of compression, implying a distant ischaemic effect from vessel compromise at the lesion site.

Speed of onset: speed of compression effects the clinical picture. Despite producing upper motor neuron damage, a rapidly progressive cord lesion often produces a ‘flaccid paralysis’ with loss of reflexes and absent plantar responses. This state is akin to ‘spinal shock’ seen following trauma. Several days or weeks may elapse before tone returns accompanied by the expected ‘upper motor neuron’ signs.

SPINAL CORD AND ROOT COMPRESSION – NEUROLOGICAL EFFECTS

LATERAL COMPRESSIVE LESION

Root/segmental damage

MUSCLE WEAKNESS in groups supplied by the involved root and segment with LOWER MOTOR NEURON (l.m.n.) signs: – wasting; – loss of tone; – fasciculation; – diminished or absent reflexes. N.B. motor deficit is seldom detected with root lesions above C5 and from T2 to L1.

SENSORY DEFICIT of all modalities or hyperaesthesia in area supplied by the root, but overlap from adjacent roots may prevent detection.

Long tract – signs and symptoms Partial (Unilateral) cord lesion

(Brown-Séquard syndrome)

MOTOR DEFICIT – dragging of the leg. In high cervical lesions weakness of finger and hand movements are noted on the side of the lesion.

UPPER MOTOR NEURON (u.m.n.) signs (maximal on side of lesion):

– weakness in a ‘pyramidal’ distribution, i.e. arms – extensors predominantly affected; legs – flexors predominantly affected.

– increased tone, clonus; – increased reflexes;

– extensor plantar response.

SENSORY DEFICIT – numbness may occur on the same side as the lesion and a burning dysaesthesia on the opposite side.

– joint position sense and accurate touch localisation (two point discrimination) impaired on side of lesion.

– Pinprick and temperature sensation impaired on opposite side.

In practice, cord damage is seldom restricted to one side. Usually a mixed picture occurs, with an asymmetric distribution of signs and symptoms.

Damage to sympathetic pathways in the T1 root or cervical cord causes an ipsilateral Horner’s syndrome (page 145).

BLADDER symptoms are infrequent and only occur when cord damage is bilateral. Precipitancy or difficulty in starting micturition may precede retention.

Long tract damage – complete cord lesion

MOTOR DEFICIT: the speed of cord compression affects the clinical picture. Slowly growing lesions present with difficulty in walking; the legs may ‘jump’ at night. Examination reveals u.m.n. signs often with an asymmetric distribution. Rapidly progressive lesions produce ‘spinal shock’ – the limbs are flaccid, power and reflexes diminished or absent and plantar responses absent or extensor.

SENSORY DEFICIT: involves all modalities and occurs up to the level of the lesion.

BLADDER: patient first notices difficulty in initiating micturition. Retention follows, associated with incontinence as automatic emptying occurs. Constipation is only noticed after a few days. Some patients develop priapism (painful erection).

CENTRAL CORD LESION

Segmental damage: A central lesion initially damages the second sensory neuron crossing to the lateral spinothalamic tract; pain and temperature sensations are impaired in the distribution of the involved segment – a suspended sensory loss. As the lesion expands, anterior horn cells are also involved and a l.m.n. weakness occurs.

Long tract effects: further lesion expansion damages the spinothalamic tract and corticospinal tracts, the most medially situated fibres being involved first. With a lesion in the cervical region, the sensory deficit to pain and temperature extends downwards in a ‘CAPE’-like distribution. As the sacral fibres lie peripherally in the lateral spinothalamic tract, SACRAL SPARING can occur, even with a large lesion. Involvement of the corticospinal tracts produces u.m.n. signs and symptoms in the limbs below the level of the lesion. The bladder is usually involved late.

In the cervical cord, sympathetic involvement may produce a unilateral or bilateral Horner’s syndrome.

LOWER CORD (CONUS) CAUDA EQUINA LESIONS

VERTEBRAL COLUMN

If a spinal cord or root lesion is suspected look for:

SPINAL CORD AND ROOT COMPRESSION – INVESTIGATIONS

MRI

This is now the investigation of choice for spinal disease, whether this lies within or outwith the dura or the spinal cord. Clinical examination and straight X-rays may suggest the level of the lesion, but for suspected metastatic disease, a sagittal MRI should cover the whole spine since more than one site may be involved and the site of compression may lie many segments higher than the clinical signs indicate. The examination must involve both T1 and T2 weighted images, the former often repeated with gadolinium enhancement.

On displaying an abnormality at a particular site, coronal views and axial views at selected levels may provide additional information.

MRI differentiates a syrinx (page 401) or a cystic swelling within the spinal cord from a solid intramedullary tumour (page 400).

SPINAL CORD AND ROOT COMPRESSION

METASTATIC TUMOUR

Occurs in 5% of all cancer patients and accounts for 50% of adult acute myelopathies.

Primary site: Usually breast, lung, prostate, kidney or myeloma (see below).

Metastatic site: Thoracic vertebrae most often involved, but metastasis may occur at any site and may be multiple.

Clinical features: Bone pain and tenderness are common features usually preceding limb and autonomic dysfunction.

Investigations: Plain radiology may be diagnostic as osteolytic lesions or vertebral collapse are present in most cases. MRI will identify extradural compression and help exclude or confirm multiple level disease.

Management

In earlier years, numerous patients were subjected to a ‘decompressive’ laminectomy followed by radiotherapy. Since metastatic tumour usually involves the vertebral body and pedicles, removal of the spinous processes and lamina increases instability. Not surprisingly results were extremely poor and led to a swing towards radiotherapy alone. A recent randomised trial in patients with radioresistant tumours affecting one site comparing decompressive surgery plus radiotherapy against radiotherapy alone showed that surgery increased the percentage of patients who remained ambulant and who regained the ability to walk. This has led to a revival of decompressive procedures in such patients. Surgical treatment aims to establish a histological diagnosis, to decompress the spinal cord and to provide stability if instability causes pain.

Techniques

Major operative treatment is inappropriate in the elderly, when paraplegia persists for > 48 hours and in those with a dismal prognosis. In such patients, if medication fails to control pain, a palliative course of radiotherapy may help.

Prognosis: Outcome depends on the nature of the primary tumour. Median survival is 3–6 months. Early diagnosis is important to ensure that the majority of patients remain ambulant. Good prognostic factors include – ambulant before or after treatment, a radiosensitive tumour and only one level of involvement.

MYELOMA

This malignant condition usually affects older age groups. It is often multifocal, involving the vertebral bodies, pelvis, ribs and skull, but solitary tumours may occur (‘plasmacytoma’). Spinal cord compression occurs in 15% of patients with myeloma and rarely without vertebral body involvement due to intradural deposits. If suspect, look for characteristic changes in the plasma immunoglobulins and for Bence-Jones protein in the urine. An isotope bone scan may be less informative than a radiological skeletal survey. Bone marrow shows infiltration of plasma cells. Serum calcium levels may be high.

Management is as for metastatic tumour with additional chemotherapy. The prognosis is variable but patients may survive many years with a solitary plasmacytoma.

MENINGIOMA

Spinal meningiomas tend to occur in elderly patients and are more common in females than in males. They usually arise in the thoracic region and are almost always intradural. Slow growth often permits considerable cord flattening to occur before symptoms become evident. MRI or CT myelography will identity the lesion.

The operative aim is complete removal. Results are usually good, but if the tumour arises anteriorly to the cord, excision of the dural origin is difficult, if not impossible, and recurrence may result.

SCHWANNOMA/NEUROFIBROMA

Schwannomas are slowly growing benign tumours occurring at any level and arising from the posterior nerve roots. They lie either entirely within the spinal canal or ‘dumbbell’ through the intervertebral foramen, on occasions presenting as a mass in the thorax or posterior abdominal wall.

Neurofibromas are identical apart from their microscopic appearance (page 304) and their association with multiple neurofibromatosis (Von Recklinghausen’s disease NF1 – see page 561) – look for café au lait patches in the skin.

Schwannomas tend to occur in the 30–60 age group. Typically they present with root pain. Root signs and/or signs of cord compression may follow.

MRI or CT myelography identifies an intradural/extramedullary lesion. Axial views will delineate any extraspinal extension (see page 395). Complete operative removal is feasible but the nerve root of origin is inevitably sacrificed. Overlap from adjacent nerve roots usually minimises any resultant neurological deficit.

INTRAMEDULLARY TUMOURS

Intrinsic tumours of the spinal cord occur infrequently. In adults, ependymomas occur more frequently, but in children low grade astrocytomas are by far the most common. Cystic cavities may lie within the tumour or at the upper or lower pole. Benign lesions include haemangioblastoma, lipoma, epidermoid, tuberculoma and cavernous angioma.

Clinical features

The onset is usually gradual. Segmental pain is common. Interruption of the decussating fibres of the lateral spinothalamic tract causes loss of pain and temperature sensation at the level of the involved segments.

Tumour expansion and involvement of the anterior horn cells produces a lower motor neuron weakness of the corresponding muscle groups; corticospinal tract involvement produces an upper motor neuron weakness below the level of the lesion. The sensory deficit spreads downwards bilaterally, the sacral region being the last to become involved.

EPENDYMOMA OF THE CAUDA EQUINA

Over 50% of spinal ependymomas occur around the cauda equina and present with a central cauda equina syndrome (page 394). Operative removal combined with radiotherapy usually gives good long-term results, although metastatic seeding occasionally occurs through the CSF.

SPINAL CYSTIC LESIONS

SYRINGOMYELIA

Syringomyelia is the acquired development of a cavity (syrinx) within the central spinal cord. The lower cervical segments are usually affected, but extension may occur upwards into the brain stem (syringobulbia, see page 381) or downwards as far as the filum terminale.

The cavitation appears to develop in association with obstruction:

The syrinx may obliterate the central canal leaving clumps of ependymal cells in the wall. In contrast HYDROMYELIA is the congenital persistence and widening of the central canal.

Syringomyelia should be distinguished from cystic intramedullary tumours, although both pathologies may coexist.

Clinical features

– Dissociated sensory loss (i.e. loss of pain and temperature sensation with retention of other senses) occurring in a cape-like distribution. Painless burns are a classic sign.

– Wasting and weakness of the small muscles of the hand and winging of the scapula from anterior horn cell involvement. Scoliosis often results.

– Long tract signs follow.

– Brain stem signs may appear, either from syringobulbia or an associated Chiari malformation.

– Hydrocephalus occurs in 25% but is usually asymptomatic.

SPINAL INFECTION

ACUTE EPIDURAL ABSCESS

Tend to occur in debilitated patients – diabetes, malignancy, liver or renal failure, intravenous drug abuse and alcoholism.

Organism: Staphylococcus aureus is the most common agent (90% of cases).

Spread: Haematogenous, e.g. from a boil or furuncle, or direct from vertebral osteomyelitis.

Site: Usually thoracic, but may affect any level and be extensive. Cord damage occurs either from direct compression or secondary to a thrombophlebitis and venous infarction.

Clinical features: Develops over several days mimicking a rapidly progressive extradural tumour or haematoma with bilateral leg weakness, a sensory level and urinary retention, but distinguishing features are:

As the abscess extends upwards, the sensory level may rise.

Investigations: Straight X-ray may or may not show an associated osteitis or discitis.

Management: Urgent decompressive laminectomy and abscess drainage combined with intravenous antibiotic therapy over some weeks provide the best chance of recovery of function. In the cervical spine, anterior collections may be drained through the disc space.

SPINAL TUBERCULOSIS (Pott’s disease of the spine)

In developing countries, spinal TB is mostly a disease of childhood or adolescence. In Britain it usually affects the middle aged and is particularly prevalent in immigrant populations and in the immunocompromised. The incidence is now increasing, probably due to the development of antibiotic resistance.

The lower thoracic spine is commonly involved and the disease initially affects the intravertebral disc and spreads to adjacent vertebral bodies.

DISC PROLAPSE AND SPONDYLOSIS

Intervertebral discs act as shock absorbers for the bony spine.

Discs degenerate with age, the fluid within the nucleus pulposus gradually drying out. Genetic factors may play a role. Disc collapse produces excessive strain on the facet joints, i.e. the superior and inferior articulatory processes of each vertebral body, and leads to degeneration and hypertrophy.

LUMBAR DISC PROLAPSE

A congenitally narrowed spinal canal increases susceptibility to the development of nerve root compression. Here the spinal canal diameter is considerably diminished and minor disc protrusion or mild joint hypertrophy may more readily compress the nerve root.

Posterolateral disc herniations usually compress the nerve root exiting through the foramen below the affected level, e.g. an L4/5 disc lesion will compress the L5 nerve root, but large disc protrusions or a free fragment may compress any adjacent root.

Lumbar disc lesions may occur at any level but L4/5 and L5/S1 are the commonest sites (95%).

CLINICAL FEATURES

Posterolateral disc protrusion

Injury: A history of falling, or lifting heavy weights; associated back pain often precedes the onset of leg symptoms.

Leg pain: Root irritation or compression produces pain in the distribution of the affected root and this should extend below the mid-calf. Coughing, sneezing or straining aggravates the leg pain which is usually more severe than any associated backache. If compression causes severe root damage the leg pain may disappear as neurological signs develop.

Sensory symptoms: Numbness or paraesthesia occur in the distribution of the affected root.

‘MECHANICAL’ SIGNS: Spinal movements are restricted, scoliosis is often present and is related to spasm of the erector spinae muscles, and the normal lumbar lordosis is lost.

Straight leg raising: L5 and S1 root compression causes limitation to less than 60° from the horizontal and produces pain down the back of the leg.

Dorsiflexion of the foot while the leg is elevated aggravates the pain. Elevation of the ‘good’ leg may produce pain in the other leg.

(If in doubt about the veracity of a restricted straight leg raising deficit, sit the patient up on the examination couch with the legs straight. This is equivalent to 90° straight leg raising.)

Reverse leg raising (femoral stretch)

Tests for irritation of higher nerve roots (L4 and above)

NEUROLOGICAL DEFICIT: Depends on the predominant root involved:

L4 – Quadriceps wasting and weakness; sensory impairment over medial calf; impaired knee jerk.

L5 – Wasting and weakness of dorsiflexors of foot, extensor digitorum longus and extensor hallucis longus; wasting of extensor digitorum brevis; sensory impairment over lateral calf and dorsum of foot.

S1 – Wasting and weakness of plantar flexors; sensory impairment over lateral aspect of foot and sole; impaired ankle jerk.

Root signs cannot reliably localise the level of disc protrusion due to variability of the anatomical distribution.

Central disc protrusion

Symptoms and signs of central disc protrusion are usually bilateral, although one side is often worse than the other.

Leg pain: Extends bilaterally down the back of the thighs. Pain may disappear with the onset of motor loss.

Paraesthesia: Occurs in the same distribution.

Sphincter paralysis: Loss of bladder and urethral sensation with intermittent or complete retention of urine occurs in most patients. Anal sensation is usually impaired and accompanies constipation.

Severe pain associated with lateral disc protrusion may inhibit micturition. In this instance, strong analgesia should allow normal micturition; the presence of normal perineal sensation excludes root compression as the cause of the retention.

Sensory loss: Extends over all or part of the sacral area (‘saddle’ anaesthesia) and confirms a neurogenic cause for the sphincter disturbance.

Motor loss: Usually presents as foot drop with loss of power in the dorsiflexors and plantarflexors of both feet.

Reflex loss: The ankle jerks are usually absent on each side.

LUMBAR SPINAL STENOSIS

Congenital narrowing of the lumbar spinal canal, or secondary narrowing due to hypertrophic facet joints, may predispose to root compression from a herniated disc, but in addition may produce ‘neurogenic claudication’. Symptoms of root pain, paraesthesia or weakness develop after standing or walking and may be relieved by sitting, bending forwards or lying down. Straight leg raising is seldom impaired, in contrast to patients with disc protrusion. Objective neurological findings may only appear after exercise. In some patients this condition only affects one side – the ‘unilateral facet syndrome’.

Plain X-rays may show thickened joints, but MRI or CT scanning, is required to establish the diagnosis.

Treatment: Decompression of the nerve root canal either through bilateral fenestrations or via a laminectomy usually produces good results with relief of symptoms. Implants available to distract the spinous processes at the affected level may help symptoms, but await full evaluation.

SPONDYLOLISTHESIS

Treatment: usually conservative, but if signs of root compression are present, then decompression of the root canal is necessary. Occasionally fusion is required, especially if back pain predominates.

THORACIC DISC PROLAPSE

This occurs rarely (0.2% of all disc lesions) due to the relative rigidity of the thoracic spine.

CERVICAL SPONDYLOSIS

The mobile cervical spine is particularly subject to osteoarthritic change and this occurs in more than half the population over 50 years of age; of these approximately 20% develop symptoms. Relatively few require operative treatment.

PATHOGENESIS

Resultant damage to the spinal cord may arise from direct pressure or may follow vascular impairment. The onset is usually gradual. Trauma may or may not predispose to the development of symptoms.

CLINICAL FEATURES

Radiculopathy

Root signs:

– Sensory loss, i.e. pin prick deficit in the appropriate dermatomal distribution.

– Muscle (l.m.n.) weakness and wasting in appropriate muscle groups, e.g. C5, C6 … biceps, deltoid: C7 … triceps.

– Reflex impairment/loss, e.g. C5, 6 … biceps, supinator jerk: C7 … triceps jerk.

– Trophic change: In long-standing root compression, skin becomes dry, scaly, inelastic, blue and cold.

Myelopathy

Arms: l.m.n. signs and symptoms, as above, at the level of the lesion

and/or

u.m.n. signs and symptoms below the level of the lesion, e.g. C5 lesion: deltoid and biceps weakness and wasting; reduced biceps reflex; increased finger reflex. C3/4 lesions produce syndrome of numb clumsy hands (reflecting posterior column loss).

Legs: u.m.n. signs and symptoms, i.e. difficulty in walking due to stiffness; ‘pyramidal’ distribution weakness, increased tone, clonus and extensor plantar responses; sensory symptoms and signs are variable and less prominent.

Sphincter disturbance is seldom a prominent early feature.

N.B. Involved segments may extend above or below the level of compression if the vascular supply is also impaired.

CERVICAL DISC PROLAPSE

In contrast to cervical spondylosis, cervical ‘soft disc’ protrusion is uncommon. This tends to occur acutely in younger patients and relate to a sudden twist or injury to the neck. The protrusion usually occurs posterolaterally at the C5/C6 or C6/C7 level causing a radiculopathy rather than a myelopathy. Sagittal and axial MRI will clearly outline the disc protrusion. Operative removal through an anterior approach may be required for intractable pain or neurological deficit and gives good results

SPINAL TRAUMA

Approximately 2 per 100 000 of the population per year sustain a spinal injury. Of these, 50% involve the cervical region.

At impact, spinal cord damage may or may not accompany the bony or ligamentous damage. After impact, stability at the level of injury plays a crucial part in further management. Injudicious movement of a patient with an unstable lesion may precipitate spinal cord injury or aggravate any pre-existing damage.

MECHANISMS OF INJURY

The mechanism of injury helps determine the degree of stability:

Initial assessment

The possibility of spinal injury must be considered at the scene of the accident and all movements and transportation of the patient undertaken with extreme caution especially when comatose. Most spinal injuries occur in conscious patients who complain of pain, numbness or difficulty with limb movements.

Examination may reveal tenderness over the spinous processes, paraspinal swelling or a gap between the spinous processes, indicating rupture of an interspinous ligament.

Neurogenic paradoxical ventilation (indrawing of the chest on inspiration due to absent intercostal function) may occur with cervical cord damage.

Bilateral absence of limb reflexes in flaccid limbs, unresponsive to painful stimuli, indicates spinal cord damage (unless death is imminent from severe head injury.)

Painless urinary retention or priapism may also occur.

SPINAL TRAUMA – INVESTIGATIONS

SPINAL TRAUMA – INVESTIGATIONS/MANAGEMENT

If straight X-rays are difficult to visualise or if clinical suspicion of cord injury persists despite normal X-rays, then a CT scan or MRI should be performed.

SPINAL TRAUMA – MANAGEMENT

Management of injury at specific sites

Management of the paraplegic patient

After spinal cord injury, transfer to a spinal injury centre with medical and nursing staff skilled in the management of the paraplegic patient provides optimal daily care and rehabilitation.

Important features include:

1. Skin care – requires meticulous attention. Two-hourly turning should prevent pressure sores. Attempt to avoid contact with bony prominences or creases in the bed sheets. Air or water beds or a sheepskin may help.

2. Urinary tract – long-term catheter drainage or intermittent self-catheterisation is required. Infection requires prompt treatment. Eventually, training may permit automatic reflex function (in cord lesions) or micturition by abdominal compression (in root lesions). In some, urodynamic studies may indicate possible benefit from bladder neck resection.

3. Limbs – intensive physiotherapy helps prevent flexion contractures (in cord injury) and plays an essential role in rehabilitation.

OUTCOME FOLLOWING SPINAL CORD OR ROOT INJURY

VASCULAR DISEASES OF THE SPINAL CORD

Blood supply to the spinal cord is complex; the main vessels are the anterior and posterior spinal arteries.

SPINAL CORD INFARCTION

Anterior spinal artery syndrome

The level at which infarction occurs determines symptoms and signs.

Characteristic features include:

– Radicular pain at onset

– Sudden para/quadraplegia

– Flaccid limbs days spastic

– Areflexia days hyper-reflexia and extensor plantar responses

– Sensory loss to pain and temperature up to the level of cord damage

– Preserved vibration and joint position sensation (dorsal columns supplied by the posterior spinal arteries)

– Urinary retention

When only penetrating branches are involved, long tract damage may be selective and sensory loss may be minor.

Spinal cord ischaemia due to aortic atheroma evolves slowly and preferentially affects anterior horn cells.

A pure conus syndrome (page 394) occasionally occurs.

Investigative approach

– Exclude other causes of acute para/quadriplegia – cord compression, Guillain-Barré syndrome – by appropriate imaging or neurophysiology

– Confirm spinal ischaemia by MRI (T2 weighted imaging showing hyperintense signal changes)

– Explore possible sources of spinal ischaemia

Small vessel diseases

diabetes – random or fasting blood glucose

vasculitis – see pages 267–269

neurosyphilis – CSF VDRL, FTA and TPI tests (see page 499)

endarteritis secondary to – CSF meningeal infection or granulomatous disease

aortic (large) vessel diseases

atheromatous – vascular risk factor e.g. cholesterol

embolic – echocardiography, blood cultures

thrombotic – coagulation screen

dissection/aneurysm – transoesophageal echo (TOE) angiography

hypotension – ECG, cardiac enzymes

Treatment is symptomatic and the outcome variable.

Posterior spinal artery syndrome

This is rare as white matter structures are less vulnerable to ischaemia. The dorsal columns are damaged and ischaemia may extend into the posterior horns.

Clinical features:

– Loss of tendon reflexes/motor weakness

– Loss of joint position sense.

Venous infarction

A rapid ‘total’ cord syndrome with poor outcome often associated with pelvic sepsis.

SPINAL ARTERIOVENOUS MALFORMATION (Angiomatous malformation)

Arterio-venous malformations (AVMs) are abnormal collections of blood vessels. Arteries communicate directly with veins, bypass the capillary network and create a ‘shunt’. The AVM appears as a mass of convoluted dilated vessels.

Site

Intradural AV malformations occur in younger patients at any age in either sex and are most likely congenital. Dural AV fistulae are most common in males between 40–70 years. They are probably acquired and related to trauma.

Clinical features

SUDDEN ONSET (10–15%)

A bruit may be heard overlying a spinal AVM and occasionally midline cutaneous lesions – haemangiomas, naevi or angiolipomas – are found. (Note that cutaneous angiomas are not uncommon and do not necessarily imply an underlying lesion.)

Investigation

MRI will demonstrate abnormal signal from the lesion or from draining veins. Myelography will also demonstrate abnormal draining veins. Selective angiography is required to delineate arterial feeders.

Management

Untreated, 50% of patients with gradual onset of symptoms would be unable to walk within 3 years. Treatment should prevent progression and may well improve a gait or bladder disturbance. Delay may result in irreversible cord damage.

Techniques:

Embolisation

– may successfully obliterate dural AVMs, particularly when fed by one or two dural arteries – may aid subsequent operative treatment – or may produce symptomatic improvement in inoperable lesions.

  Surgery

– It is important to identify and divide the feeding vessel and excise the shunt. Total excision of all the dilated veins is unnecessary and hazardous. Operative risk for most dural A-V fistula is low and excision provides an alternative to embolisation. In contrast, when an AVM lies within the cord substance and/or ventral to the cord, operative risks are high. Staged pre-operative embolisation may help, but in some, a conservative approach may be appropriate.

Spinal Epidural and Subdural Haematomas: These may present with a rapid onset of paraplegia. Epidural or less commonly, subdural haematoma may occur due to rupture of a spinal AVM, after minor trauma or lumbar puncture, or spontaneously in patients with a bleeding disorder, liver disease or on anticoagulant therapy. MRI (or myelography) clearly demonstrates the lesion. Urgent decompression is required after correcting any coagulation deficit, without waiting for spinal angiography. Pathological examination of the haematoma may reveal angiomatous tissue; in other patients, there is no evident cause.

SPINAL DYSRAPHISM

SPINAL DYSRAPHISM: This term encompasses all defects (open or closed) associated with a failure of closure of the posterior neural arch.

Embryology

Site: 80% occur in the lumbosacral region.

Incidence: 2/1000 births in the UK, but geographical variation exists (0.2/1000 in Japan) and the incidence is declining. A familial incidence increases the risk (5% if a sibling is affected). Both genetic factors and teratogens, e.g. sodium valproate, have a role. Folic acid before and during pregnancy provides some protection.

Associated abnormalities: Hydrocephalus, Chiari type II, aqueduct forking.

Clinical assessment

Myelomeningocele: This lesion should be carefully examined for the presence of neural elements. Transillumination of the sac may help. Observation of movement in the limbs and in specific muscle groups, occurring spontaneously and in response to pain applied both above and below the level of the lesion, helps determine the degree and level of neurological damage. Also note the presence of a dilated bladder and a patulous anal sphincter. Look for any associated congenital anomalies, e.g. hydrocephalus, scoliosis, foot deformities.

Meningocele: Patients with this lesion seldom show any neurological deficit.

Investigations

Ultrasound or MRI maydetect neural elementsextending into the sac.

Management

Myelomeningocele: Advances in both orthopaedic and urological procedures have considerably improved the long-term management of the associated disabilities in most patients. Active treatment, however, in patients with gross hydrocephalus, complete paraplegia and other multiple anomalies as well as the spinal dysraphism, may merely prolong a painful existence and in such patients, some adopt a conservative approach.

Treatment within a few days involves closure and replacement of the neural tissues into the spinal canal to prevent infection. This initial step provides time to consider the wisdom of embarking on further active management.

Meningocele: In the presence of a CSF leak, urgent excision is performed; otherwise this is deferred, perhaps indefinitely if the lesion is small.

Spina bifida occulta: Treatment may not be required, although patients with a cutaneous abnormality or with neurological signs, should undergo ultrasound or MRI to exclude an intraspinal anomaly.

Antenatal diagnosis

Screening the maternal serum/amniotic fluid for alpha-fetoprotein and acetylcholinesterase, fetal ultrasonography and contrast enhanced amniography in high risk patients (e.g. with an affected sibling) provides an effective method of detecting neural tube defects and offers the possibility of therapeutic abortion. Intrauterine surgery to repair the myelomeningocele is currently under evaluation and may reduce the severity of associated defects, e.g. Chiari II.

TETHERED CORD: in some patients the conus medullaries lies well below its normal level (L1), ‘tethered’ by the filum terminale. Since vertebral growth proceeds more rapidly than growth of the spinal cord, tethering may produce progressive back pain or neurological impairment as the cord is stretched.

DIASTOMATOMYELIA: A congenital splitting of part of the spinal cord by a bony, fibrous or cartilaginous spur. This usually lies at the upper lumbar region and extends directly across the spinal canal in an antero-posterior direction. The split cord does not always reunite distal to the spur (diplomyelia).

Investigation: MRI is the investigation of choice in spinal dysraphism, but straight X-ray may reveal associated congenital abnormalities: spina bifida occulta, fused or hemivertebrae. CT scanning may help demonstrate the presence of a bony spur.

Management: Although some recommend prophylactic division of the tethered filum terminale in the absence of neurological impairment, most reserve operative treatment for those who present with a neurological deficit, especially if there is evidence of progression, or prior to correction of any spinal deformity. In contrast, prophylactic removal of the spur in patients with diastomatomyelia is usually performed, even in the absence of neurological impairment.

CONGENITAL DERMAL SINUS TRACT/DERMOID CYST