Subarachnoid Hemorrhage From a Distal Middle Cerebral Artery Aneurysm Possibly Related to Segmental Arterial Mediolysis.

Abstract

Distal middle cerebral artery aneurysm (DMCAAn) is rare, and the clinical features and the etiology are not well understood. Segmental artery mediolysis (SAM) is a pathologic entity that affects the media of the muscular artery and can cause arterial dissection and a hemorrhagic event. Subarachnoid hemorrhage (SAH) due to SAM in the vertebral artery has been documented. However, SAH from a ruptured DMCAAn due to SAM has not yet been described. A 49-year-old woman presented with a headache and vomiting. Computed tomography (CT) revealed SAH, and CT angiography showed a DMCAAn, which was treated by trapping and resection. Histopathologic studies showed loss of the media and reparative changes in the arterial wall including intimal hyperplasia and increased vasa vasorum in the adventitia. These findings were indicative of SAM in the reparative phase. She did not show any other possible etiologies of DMCAAn including infectious endocarditis and vasculitis, and CT angiography of the trunk did not show any other vascular lesions. She was discharged from the hospital approximately 3 weeks after the surgery without any apparent neurological deficits. Our case suggests that SAM can also occur in the middle cerebral artery and result in DMCAAn.