Most occur in the cerebellar hemispheres but they are also found in the brainstem and spinal cord. Other locations have been described but are extremely rare. They arise from cells within the nervous system called stromal cells and are characterised by rich networks of blood vessels making up the tumour. Abnormal connections develop between the arterial and venous sides of the circulation and these tumours acts as small vascular malformations. Two distinct types are recognised:
These account for approximately 60% of cases. The cyst does not have a true, cellular wall of its own and removal of the nodule of solid tumour contianed therein will be sufficient to completely treat the lesion. Symptoms are often precipitated by an increase in the size of the cyst.
Accounting for 40% of the total these can provide more of a diagnostic as well as a therapeutic challenge, if the patient is not known to have Von Hippel-Lindau disease. Endovascular embolisaiton is occasionally helpful with these lesions to limit peri-operative blood loss although we use it very selectively becuase of associated risks of tumoural swelling. It has been our experience that if similar surgical technique is deployed as when removing an arteriovenous malformation, these lesions may be removed with very little blood loss. Stereotactic radiosurgery offers an alternative for inoperable lesions although without the benefit of confirming the tissue diagnosis.
Approximately 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 short 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 manaifestations by age 40. VHL causes tumours to develop in various locations throughout the body:
Central Nervous System (cerebellum/brainstem/spinal cord- see left)
Eyes (retinal angioma)
Head and Neck (Endolymphatic sac tumour (ear), paraganglioma)
Lungs (Pulmonary haemangioma)
Kidneys (Renal haemangioblastoma, Renal carcinoma, renal cysts)
Adrenal gland (Phaeochromocytoma)
Pancreas (Pancreatic haemangioblastomas and cysts)
Reproductive Organs (Broad ligament cystadenoma, Epididymal cystadenoma)
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. Because these tumours exhibit staccato growth were one to operate on every tumour that grew a little on a scan a great deal of unnecessary surgery would be the result.
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