A rare intracranial fusiform thrombosed aneurysm of the distal middle cerebral artery: A case report

BACKGROUND: Intracranial aneurysms of the distal middle cerebral artery are rare, and most etiologies are infection or dissection. We present an extremely rare intracranial fusiform thrombosed aneurysm of the distal middle cerebral artery with histopathological confirmation of a pseudoaneurysm. CASE DESCRIPTION: Our patient, a 68-year-old female, was previously healthy and had no history of infection or trauma. A fusiform thrombosed aneurysm of the distal middle cerebral artery was detected incidentally. The patient was treated successfully with trapping and resection of the aneurysm followed by superficial temporal artery to middle cerebral artery anastomosis. Xanthochromic and hypertrophic arachnoid membranes around the aneurysm were noticed, and a thrombus was detected inside the lesion. The aneurysmal wall had hyalinized connective tissue incompletely surrounded with intima, with no media or adventitia. Pathologically, it was a pseudoaneurysm. CONCLUSION: We report an extremely rare case of a pseudoaneurysm of the distal middle cerebral artery. We discuss the etiology of the lesion, with a literature review, and propose that the appearance and increase of the pseudoaneurysm was followed by microbleed of an aneurysm unrelated to the branching zone.