Completely Thrombosed Distal Middle Cerebral Artery Aneurysm Mimicking a Cavernous Angioma: Case Report and Review of the Literature

BACKGROUND: Distal middle cerebral artery (MCA) aneurysms originate from branches of MCA distal to its main bifurcation or the peripheral branches. Distal MCA aneurysms are uncommon compared with saccular aneurysms, which develop along the proximal trunks of MCA. However, thrombotic aneurysms, characterized by organized intraluminal thrombus and solid mass, are frequently in the large and giant size range, whereas complete thrombosis of non-giant MCA aneurysms is very rare. CASE PRESENTATION: We present the clinical case of a 53 years-old woman with a completely thrombosed medium distal MCA aneurysm mimicking a cavernous angioma. She came to our emergency department after the onset of tinnitus and persistent headache. Magnetic resonance imaging performed subsequently showed a nodular mass surrounded by edema located in the temporal lobe with a homogeneous peripheral contrast enhancement. Furthermore, angiography showed regular flow in the MCA and confirmed the diagnosis of cavernous angioma. The patient underwent surgery, and the lesion was found to be a thrombosed aneurysm originating from the distal temporal branch of the left MCA (M2 segment). CONCLUSIONS: To our knowledge, this is the first report of a thrombosed distal medium MCA aneurysm that mimicked a cavernous angioma. The completely thrombosed aneurysm can be confused with intracranial lesions or cavernous malformations, which can have similar radiographic features without angiographic anomalies, so it is mandatory to consider the possibility of a thrombosed aneurysm for a correct differential diagnosis.