Completely thrombosed middle cerebral artery aneurysm mimicking cavernous malformation: illustrative case report with operative video and review of the literature

Complete aneurysmal thrombosis is a rare occurrence in which a combination of thrombus and plaque contributes to the complete obliteration of the lumen of an aneurysm, rendering it occult on angiographic imaging. To date, there is a paucity of information in the literature describing the clinical/radiographic presentation and operative management of complete thrombosed aneurysms of the middle cerebral artery. A focused literature review was performed to identify previously reported cases of complete MCA aneurysm thrombosis. Five cases meeting these criteria were identified, of which four underwent open microsurgical management and one was treated endovascularly. We report a clinical case of a 35-year-old female who presented with severe exacerbation of baseline headaches. Radiographic features were suggestive of a ruptured cavernous malformation. In the operating room, a large and completely thrombosed aneurysm of the superior M2 was encountered. The aneurysm was treated with ultrasonic evacuation of the thrombus and plaque, followed by definitive clip reconstruction. Completely thrombosed aneurysms are rare entities that can masquerade cavernous malformations (CCM) and/or intra-axial neoplasms. Following a literature review, we highlight nuances of diagnosis and discuss pearls of surgical management along with the inclusion of a narrated, operative video.