Intrinsic tumours of the spinal cord occur infrequently. In the Glasgow series (Table, page 383) almost all were slowly growing astrocytomas (grades I and II) although other series report an equal incidence of ependymomas. 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 track 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.
Straight X-rays occasionally show widening of the interpedicular distance or 'scalloping' of the vertebral bodies. Myelography confirms the presence of an intramedullary lesion, but MRI provides most information, differentiating tumour from syringomyelia, and identifying the extent of the lesion and the presence of any associated cysts.
Tl weighted sagittal MRI showing intramedullary lesion
When an intrinsic cord tumour is suspected, an exploratory laminectomy is required. An attempt is made to obtain a diagnosis either through a longitudinal midline cord incision or by needle biopsy. Cystic cavities within a tumour or an associated syringomyelia may benefit from aspiration. With some ependymomas and benign lesions, a plane of cleavage is evident and partial or even total removal is possible. Attempted removal of low grade astrocytomas carries less encouraging results and operation is contraindicated in malignant tumours. After tumour biopsy or removal, radiotherapy is often administered, but its value is uncertain.
Over 50% of spinal ependymomas occur around the cauda equina and present with a central cauda equina syndrome (page 380). Operative removal combined with radiotherapy usually gives good long-term results, although metastatic seeding occasionally occurs through the CSF.
SPINAL CYSTIC LESIONS
Enterogenous cysts: cysts with a mucoid content are occasionally found \ r lying ventral or dorsal to the cord. They \| are often associated with vertebral malformation or other congenital abnormality, and are thought to arise from remnants of the ncuroenteric canal.
Epidermoid/dermoid cysts: may be of developmental origin or may follow implantation from a preceding lumbar puncture procedure.
Intramedullary cystic lesion:
syringomyelia (see over) or cystic cavitation within a glioma.
. Arachnoid cysts: arachnoid pouches filled with contrast medium are occasionally found incidentally during myelography. These may seal off, producing CSF filled cysts. They occur predominantly in the thoracic region and sometimes cause cord compression. Children with extradural arachnoid cysts frequently develop kyphosis; the causal relationship remains unknown. In ankylosing spondylitis lumbosacral cysts produce a cauda equina syndrome.
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 367) or downwards as far as the filum terminale.
The cavitation appears to develop in association with obstruction:
- usually around the foramen magnum in conjunction with the Chiari malformation.
- also secondarily to trauma or arachnoiditis.
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.
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