Intradural Spinal Tumours

Spinal tumours may be classified into those arising from or involving the tissues outside the dural covering of the nervous system-extradural. Those arising intradurally may be subdivided into those developing within the spinal cord itself (intramedullary) or from the dura or emerging spinal nerves (intradural extramedullary). ost of the tumours dealt with at our practice are intradural.

Intramedullary Tumours- glioma, ependymoma, haemangioblastoma

Intramedullary tumours are a rare group of tumours arising within the spinal cord itself and occur in both children and adults. They are notroriously difficult to diagnose because the symptoms they produce are frequently non-specific, slowly progressive and more easily explicable by common, non-tumour pathologies.

In children they most commonly present with spinal deformity or loss of function in the extremities. In adults axial spinal or nerve pain is the most common symptom followed by altered sensation or loss of function in the extremities.

Intramedullary tumours are generally name for the cell-type giving rise to them and amongst the more common are:

  • Ependymoma- the commonest intramedullary tumour in adults
  • Astrocytoma- a glial tumour which is the commonest intramedullary tumour in children. Approximately 75% are diffuse fibrillary astrocytoma (WHO grade II). These may upgrade to more agressive types over time.
  • Haemangioblastoma- 30% of patients who present with an intramedullary haemangioblastoma will have Von Hippel-Lindau disease.
  • Metastasis- spread of a primary cancer to the spinal cord is a rare and late development affecting approximately 5% of patients with a disseminated malignancy. It is an extremely rare first presentation of a cancer.

Other tumours are possible including benign entities such as dermoid tumours. All are however capapable of producing signifincant and irreversible disability as they grow. Surgery for an intramedullary tumour carries significant risks but also too carries the best prospects for short and medium term control of tumours that are causing progressive disability. The surgery serves two functions. firstly to establish the precise nature of the tumour and therefore to direct subsequent managment. The second role is attempted cure or medium term control of the tumour. Some low grade intramedullary tumours (haemangioblastoma, ependymoma) may be completely cured by removal albeit sometimes at the cost of short term neurological worsening. Others which are more diffusely spread within the cord e.g. diffuse fibrillary astrocytoma may not be possible to remove completely but reducing their bulk can be enough to slow the progression of disability significantly.

Intradural Extramedullary Tumours- Schwannoma, Neurofibroma

cauda_equina_tumourThese tumours arise usually from the dural covering itself (Meningioma) or from the cells forming the outer sheath of the spinal nerves. Less common are benign cysts in the arachnoid layer of the meninges (arachnoid cyst) or dermoid cysts (benign growths containing cell types native to the skin). Tumours of the non functional terminal part of the spinal cord - the Filum Terminale- may also be considered in this group e.g. Myxopapillary Ependymoma. If symptomatic these tumours are usually very amenable to removal with a good safety profile.

If occurring in isolation then prospects for cure are usually good. Spinal nerve sheath tumours develop in more than 40% of patients affected by Neurofibromatosis type 1 but perhaps only about 2% of those tumours cause symptoms that warrant treatment. For many patients with NF1 watchful waiting with clinical and radiological surveillence is appropriate given the propensity to develop tumours on multiple nerves over time. There is also an 8-13% lifetime risk that a patient with NF1 will develop malignant change in a previously benign nerve sheath tumour.

Neurofibromastosis and Schwannomatosis

Neurofibromatosis type 1 is a condition which results from a mutation in a gene on chromosome 17. It affects approximately 1 in 3000 people. The gene is called NF1 and codes for a protein called neurofibromin. It is a tumour supressor gene meaning that when it is not functioning the following can develop:

  • Discolouration in the skin (cafe au lait spots) or freckling in the armpit
  • Cutaneous and subcutaneous benign masses called neurofibroma
  • Benign nerve sheath tumours on nerves arising from the spinal cord and nerves elsewhere in the body
  • Malignant nerve sheath tumours (8-13% lifetime risk in patients with NF1)
  • Benign hamartomas in the iris (Lisch Nodules)
  • Glioma particularly of the optic pathways in the brain
  • Bone dysplasias
  • Peripheral neuropathy
  • Hypertension
  • Scoliosis

Neurofibromatosis type 2 is a genetically and clinically quite distinct disease to the above. It is less common affecting aproximately 1:35000 individuals. All develop vestibular schwannomas and in most these are bilateral. Other tumours assosciated with this condition include schwannomas of other cranial nerves, meningioma and spinal cord ependymoma. The gene mutation in NF2 is on chromosome 22 and its gene prodict is the Merlin protein. Juvenile cataracts may be the earliest detectable evidence of the disease.

Schwannomatosis is a related condition to the above with a predisposition to developing schwannomas on the spinal nerves but never on the vestibular nerves of the ear as in NF2. Schwannomatosis usually affects males in middle age and they are usually the only member of their family to be so affected. Meningiomas occur very rartely. The gene abnormalities are distinct from the NF2 gene abnormality and at least two implicated genes have been identified on chromosome 22 close to the NF2 gene. (SMARCB1 and LZTR1)

Von Hippel-Lindau Disease (VHL)

spinal cord haemagioblastomaApproximately 20% of central nervous system haemangioblastomas occur in patients affected by Von Hippel-Lindau disease(VHL). This is a condition resulting from mutation of a gene on the shrt arm of chromosome 3. The mutation is inherited in 80% of cases but occurs de-novo in 20%. Someone with a parent harbouring the defective gene will have a 50% chance of inheriting the gene.

The disease itself does not usually appear in childhood. Most patients will develop one of its manifestations by age 40. VHL causes tumours to develop in various locations throughout the body. For more infromation about VHL please click here.

Patients with VHL benefit from genetic counselling and from regular screening for the development of new tumours. New tumours developing within the nervous system do not always require immediate intervention. Growth in such haemangioblastomas is not always assosciated with the development of symptoms. Surgery is not indicated for asymptomatic growth although the development of oedema around the tumour foreshadowing the development of a cyst may indicate that intervention could be beneficial.