[Lipoma of the cerebral convexity and refractory focal epilepsy]

Intracranial lipomas make up approximately 0.1% of all cerebral tumours. They are considered to be congenital malformations, caused by poor differentiation and abnormal persistence of the primitive meninges, which has become adipose tissue during the development of the subarachnoid space. They are usually found in the midline, often in the cisterna pericallosa. It is very unusual for them to be in the fissure of Sylvius and cerebral convexity. Most cerebral lipomas are aymptomatic. Epileptic seizures are the commonest symptom, and are sometimes refractory to treatment.

A 20 year old man with no previous clinical history. From the age of three years he had frequent senso-motor seizures of the lower half of the right side of his body, which were resistant to anti-epileptic drugs. On magnetic resonance there was an extra axial lesion in the left posterior parietal and parasagittal convexity. This was hyperintense in T(1) sequences, not seen in STIR sequences, and was compatible with fatty tissue. Subtotal removal of the tumour was carried out and the histopathological diagnosis was lipoma. The patient had no seizures in the year after operation.

Lipomas of the cerebral hemispheres are very uncommon. The usual symptoms are focal epileptic seizures, as a result of the cortical irritation caused by close adherence of the lipoma to the cerebral cortex or associated cortical or vascular dysplasias. They have easily recognized characteristics on computerized axial tomography and magnetic resonance. Treatment should be conservative unless it is associated with refractory epilepsy, in which case careful resection may be considered, although this is rarely complete.