Incidental unruptured aneurysm of the distal M2 segment: Case report and review of literature

Aneurysms of the Middle cerebral artery (MCA) are more common at the bifurcation. Distal MCA aneurysm in M2, M3 and M4 segments are rare. Here, we discuss an incidental distal M2 segment aneurysm and its management along with a brief literature review. Fifty-one-year-old male, presented to us with a history of the giddiness of 1-week duration. During the evaluation for giddiness, his computed tomography (CT) brain plain showed a small well-defined hyperdense rounded lesion in the left Sylvian fissure. CT angiogram was done and it showed a saccular aneurysm measuring 7.7 mm × 7.3 mm and had a narrow neck of 1.5 mm arising from the distal M2 segment of MCA. The aneurysm was directed superiorly in the distal MCA. Digital subtraction angiogram showed a 6.4 mm × 6.9 mm distal M2 segment bilobed aneurysm with a neck of 3.8 mm and projecting superiorly. Surgical clipping of the aneurysm was done. Perioperative period was uneventful and the patient is doing well at 3 months follow-up. Review of the literature showed that the incidence of distal MCA aneurysm was low. Intra-operative CT angiogram, neuro-navigation, indocyanine green video angiography (ICGV) are some of the useful tools in improving outcomes in surgical clipping of these aneurysms. Distal MCA aneurysms are less frequently encountered. Surgical clipping is the treatment of choice in these cases. Challenge arises in localising these aneurysms and adjuncts such as intraoperative CT angiogram, neuro-navigation, ICGV can be useful to overcome that challenge.