Sylvian subarachnoid and extra-pial cavernous angioma.

Cavernous angiomas are one of the four types of vascular malformations of the central nervous system. Lesions situated subarachnoidally are rare although some cases with an infratentorial localization have been reported. Our case represents an unusual localization of a subarachnoid cavernous angioma. A 35- year-old patient was admitted to our department with signs of subarachnoid hemorrhage. A 1 cm hyperdense lesion placed at the right Sylvian fissure was distinguished by CT-scan examination and no arterial supply was revealed on cerebral angiography. Surgical intervention showed a lesion placed extra-pial and totally encased in the subarachnoid space in the superficial part of the Sylvian cistern. This case represents a radiologically visible supratentorial extra-pial subarachnoidal cavernous angioma. This case provides confirmation of one of the supposed causes of subarachnoid hemorrahage ''sine materia''.