Complete Resection of an Intradural Extramedullary Foramen Magnum Cavernous Malformation.

Only few case reports of intradural extramedullary-located cavernous angiomas are available. This report describes an extra-axial hemorrhagic lesion located on the lateral surface of the medulla oblongata at the foramen magnum. Follow-up magnetic resonance imaing clearly demonstrated growth of the lesion, probably due to repetitive intralesional hemorrhaging. Initially, a right vertebral artery aneurysm or an arteriovenous malformation was suspected. Digital subtraction angiography excluded these differential diagnoses, although doubt remained concerning the possibility of a thrombosed aneurysm. Preoperatively, the lesion did not had the typical macroscopical aspect of a cavernoma and appeared rather as an expansive encapsulated multicystic vascular lesion. Nevertheless, pathologic analysis confirmed the diagnosis of a cavernous hemangioma. Complete microsurgical resection was obtained without neurologic impairment.