Glioma of the Spinal Cord

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What is Glioma of the Spinal Cord?

Glioma of the Spinal Cord presents as tumours within the spinal cord.

The spinal cord forms part of the central nervous system. It is a cylindrical continuation of the brainstem, commencing from the medulla (at the level of the foramen magnum at the base of the skull) and extending to the conus medullaris at the level of the L2 vertebra. It is located within the vertebral canal - the bony tube formed by the vertebral foramina. Below the level of L2, the remaining contents of the spinal canal are known as the cauda equina - the bundle of nerve rootlets in the subarachnoid space. Within the vertebral canal run the spinal cord, the spinal meninges, the cerebrospinal fluid, associated vessels and loose connective and fatty tissue.

Arising from the spinal cord are 31 pairs of spinal nerves that are the neural connections between the peripheries and the central nervous system. They attach to the spinal cord through ventral and dorsal roots and have both afferent and efferent properties. That is, the spinal cord acts as the main pathway for communication between the brain and the rest of the body.

Tumours of the spinal cord can be either primary or metastatic. The vast majority of spinal cord tumours are metastatic deposits from other primary sites. Tumours of the spinal cord can be divided into three groups, based on the anatomical location of the tumour mass. Firstly, they are divided by their relationship to the spinal meninges, with tumours being classified as intradural or extradural. Furthermore, intradural tumours can be subdivided into those arising within the substance of the spinal cord itself - intramedullary tumours - or those arising in the subarachnoid space (extramedullary).

Extradural tumours most commonly represent metastases and usually arise within the vertebral bodies. These tumours most commonly cause spinal compression through extrinsic mass effect but can on occasion do so through intradural invasion. Symptoms from these tumours tend to be the slowly progressing features of spinal cord compression with initial predominantly motor loss followed by progressive sphincter dysfunction and ascending sensory loss. Extradural tumours represent the vast majority of spinal cord tumours.

Intradural extramedullary tumours tend to be nerve sheath tumours (neurofibromas) or meningiomas. They commonly present with nerve root involvement consisting of pain and progressive dysfunction due to spinal cord compression from the expanding tumour mass.

Intramedullary tumours usually represent gliomas - ependymomas or astrocytomas - but metastatic deposits within the spinal cord itself are increasingly recognised. These tumours result in a diffuse swelling of the spinal cord, often over several segments, characterised by loss of local function, pain and eventual loss of spinal cord function below the level of the lesion. A cyst may form in the spinal medulla, giving rise to a clinical picture of syringomyelia (predominant loss of spinothalamic function - pain and temperature sensation - and blunted reflexes at the level of the lesion). Sacral sparing is a very late feature of intramedullary tumours but is pathognomonic.

Who gets Glioma of the Spinal Cord?

It is is rare. The incidence of primary spinal cord tumours is less than 1.5 per 100 000 and of these less than 25% are gliomas. The vast majority of gliomas of the spinal cord are ependymomas and occurs in all age groups. In children, central nervous system gliomas occur primarily in the brain (less than 10% occur in the spinal cord), whilst in adults more than 75% of gliomas occur in the spinal cord with sex incidence being approximately equal. Myxopapillary ependymomas, however, are more common in males.

Geographically, the tumour is found worldwide.

Predisposing Factors

Predisposing factors in the development of spinal cord gliomas remain to be identified. Multiple spinal ependymomas have been found in patients with neurofibromatosis type 1 (von Recklinghausen's disease). Genetic changes are associated with the development of sporadic ependymomas, with the most common abnormality being a monosomy of chromosome 22. Familial clustering has been reported in a few cases.

It was thought that infection with simian virus 40 T antigen (as occurred with contamination of polio vaccine) was associated with the subsequent development of spinal ependymomas, but population studies have failed to identify a link.

Progression

This type of tumour spreads by local invasion and dissemination through cerebrospinal fluid with central nervous system seeding.

Ependymomas have a long natural history and a relatively benign course over many years. Extensive local extension may occur with time including erosion of adjacent bony structures. Dissemination to other areas within the central nervous system can occur with spread through cerebrospinal fluid. This is uncommon and occurs in less than 10% of cases of ependymoma.

Astrocytoma is associated with a greater tendency for local invasion and CSF seeding than are ependymomas.

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