SECTION IV LOCALISED NEUROLOGICAL DISEASE AND ITS MANAGEMENT B. SPINAL CORD AND ROOTS

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.

Clinical features

These depend on the site and level of the compressive lesion.

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.

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

MYELOGRAPHY

If MRI is unavailable or contraindicated e.g. pacemaker, myelography is used to screen the spinal cord and the cauda equina. This will identify the level of a compressive lesion and indicate its probable site i.e. intradural, extradural.

Even with an apparent ‘complete’ block, sufficient contrast medium may be ‘coaxed’ beyond the lesion to determine its upper extent. If not, a cervical puncture may be necessary.

Lesions in the lumbar and sacral regions require a ‘radiculogram’, outlining the lumbosacral roots.

CT SCAN/CT MYELOGRAPHY

It is impractical to use this as a screening investigation for cord compression, but if the level of interest is known, CT scanning may provide additional information.

CSF ANALYSIS

This is of limited value in cord compression. Abnormalities frequently occur, but lumbar puncture may precipitate neurological deterioration, presumably due to the creation of a pressure gradient.

Plain CT with axial cuts will clearly demonstrate bone erosion, osteophytic outgrowth and thickened facet joints causing narrowing of the spinal canal or intervertebral foramen. Axial cuts will also demonstrate disc herniation, the relationship of vertebral bone destruction to a paraspinal mass (e.g. metastatic tumour) and the extraspinal extent of an intraspinal lesion (e.g. neurofibroma).

CT myelography with axial cuts (CT performed either 6–12 hours after routine myelography or immediately after intrathecal injection of just a few ml of contrast) demonstrates clearly the degree of spinal cord or nerve root compression.

If cord compression is suspect then lumbar puncture and CSF analysis should await imaging.

CSF protein: often increased, especially below a complete block.

CSF cell count: a marked leucocyte count suggests an infective cause – abscess or tuberculosis.

CSF cytology may reveal tumour cells

SPINAL CORD AND ROOT COMPRESSION

TUMOURS

Incidence: The table below shows the approximate incidence of spinal tumours extracted from large series, but excludes tumours of the vertebral column and lymphoma. Spinal metastasis is by far the most common spinal tumour occurring in about 2–3% of all patients with cancer, but the incidence is an underestimate since not all undergo autopsy.

Pathology: The pathological features of spinal tumours match those of their intracranial counterparts (see page 303).

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

MANAGEMENT SCHEME

All patients require steroids and biopsy if no prior diagnosis exists.

Factor supporting:

Decompressive surgery (plus radiotherapy)	Radiotherapy
• Preferably ambulant, but not paraplegic > 4 hours • Radio-resistant tumour • Single-level disease • Instability at the affected level • Life-expectancy > 4 months • Deterioration following previous radiotherapy.	• Radio-sensitive tumour • Multi-level disease • Life-expectancy < 4 months • Stable neurological disease.

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.