Clinical Experience of Aneurysms Arising at the M1 Portion of the Middle Cerebral Artery Treated by Clipping

Abstract

Among middle cerebral artery aneurysms, those at the M1 portion of the middle cerebral artery have a lower incidence of occurrence. We retrospectively analyzed and reported the clinical features and management of 12 M1 aneurysms in 12 patients treated with direct clipping. Aneurysms arising at the M1 portion were mostly smaller in size and prevalent in older women, on the left side, with more intracerebral hematoma and less accompanied than those at the bifurcation. Ruptured aneurysms comprised 80% of the aneurysms and were larger than 5 mm in size, while 14.3% of those smaller than 5 mm in size were unruptured. Aneurysms were located in the upper (n=5), downward (n=5), anterior (n=1), and posterior (n=1) directions. Of the five aneurysms in the upper direction, three were in the early frontal branch, one was in the early temporal branch, and one was in the lenticulostriate artery. Two of the aneurysms in the upper direction had an intracerebral hematoma (ICH) in the frontal and temporal lobes, while one aneurysm in the downward direction had an ICH in the temporal lobe. The preoperative clinical grade of M1 aneurysms with ICH was worse than that of bifurcation aneurysms; however, the outcome was equal to that of bifurcation aneurysms.Aneurysms arising at the M1 portion should be treated with a preoperative meticulous investigation for their anatomical complexity, not only with direct clipping but also with endovascular techniques.