末梢性中大脳動脈瘤の特徴および手術アプローチ

抄録

Distal middle cerebral artery (MCA) aneurysms are relatively rare, and only few reports deal with treatment strategies. The present study retrospectively investigated the characteristics of and surgical approaches to distal MCA aneurysms. The subjects were 10 patients with distal MCA aneurysms selected from among 452 patients with cerebral aneurysms treated with neck clipping between September 2006 and August 2016. Sixteen distal MCA aneurysms were identified, with 13 (81.3%) located on the M2 segment. All the patients showed multiple cerebral aneurysms, and the total number of cerebral aneurysms was 37, representing a mean of 3.7 aneurysms per patient. The multiplicity of the aneurysms appeared markedly higher than the previous study findings in patients with distal MCA aneurysms. Evaluation with preoperative neuroimaging therefore appears important from this perspective. Of the 3 patients with ruptured distal MCA aneurysm, all the aneurysms were embedded in surrounding parenchyma with cerebral hemorrhage. This finding suggests the necessity to expose aneurysms from the surrounding parenchyma to obtain a wide surgical field for neck clipping. As for surgical approaches, anatomically, the M3 segment begins at the circular sulcus after turning 180° from the M2 segment and courses over a narrow space between the frontoparietal and temporal opercula. We therefore recommend the following: aneurysms located on M2 or M2-M3 segments above the limen insulae are accessible by using a distal sylvian approach, whereas aneurysms located from the M3 segment within the narrow and complicated structure of the opercular space need to be approached from sulci beyond the aneurysms.