Arachnoid cyst of middle cranial fossa and ipsilateral subdural haematoma: diagnostic and therapeutic implications in three cases.

We describe three cases of arachnoid cyst of the middle cranial fossa with associated intracystic and subdural haematomas. In all of the patients the diagnosis was made before surgical treatment. No bleeding could be attributed to ruptured bridging veins. In two cases the source of bleeding was identified at the interface between the dura mater and the outer membrane at the temporal skull base. We suggest that, even if wide outer membrane membranectomy is probably not indicated, careful coagulation of the membrane at the skull base is necessary to avoid bleeding within the cyst.