2021 Volume 49 Issue 6 Pages 419-425
Surgical treatment of aneurysms in the M1 segment of the middle cerebral artery (MCA) is associated with a high risk of ischemic stroke in the territory of the lenticulostriate artery (LSA). We retrospectively studied 38 consecutive patients with M1 aneurysms to evaluate the clinical characteristics and surgical outcomes with the background of routine use of indocyanine green (ICG) videoangiography and motor evoked potential (MEP). Between 2011 and 2019, 38 procedures were performed in 38 patients with M1 aneurysms. Of the 38 patients, 12 were men and 26 were women, and the mean age was 60.7 years. The mean size of aneurysm was 5.3 mm. Seventeen aneurysms were located at the origin of the early frontal branch (EFB), 10 at the LSA, and 11 at the anterior temporal artery (ATA). All of the EFB and 7 of the LSA aneurysms showed superior projections, 3 of the LSAs showed posterior projections, and all of the ATA aneurysms showed inferior projections. Seventeen patients (44.7%) had multiple aneurysms, which were most commonly ipsilateral MCA aneurysms. Surgery was performed using the transsylvian approach, with a wide opening of the Sylvian fissure from the distal part to the carotid cistern. More than 70% of the EFB and LSA aneurysms were embedded in the brain, and subpial dissection was necessary in approximately 60% of these cases. Proximity to the LSA was present in 9 of 17 EFB and all LSA aneurysms. Dissection of the LSA was infeasible in four patients, and wrapping was performed in one. A decrease in MEP amplitude was observed in 3 of 36 procedures with MEP monitoring, but it fully recovered after re-adjustment (n=2) or removal (n=1) of the clips. None of the 38 patients developed neurological deficits associated with the surgery. Postoperative diffusion-weighted imaging showed high intensity in the LSA territory in four patients, but the lesions were asymptomatic. Provided that a sufficient operative field is obtained to allow full direct inspection of the aneurysm from multiple angles and careful clipping technique is utilized under appropriate monitoring, surgical clipping of the M1 aneurysm is associated with a very low risk of surgical complications.
