M1、M2：さようならの時間です！

Progress in the field of transcatheter thrombectomy for acute stroke has come up against the hurdle of scarce data about occlusions in the terminal divisions of the middle cerebral artery and their branches in the lateral sulcus. This unhappy state of affairs can be traced to the practice of grouping these occlusions as lesions of the M2 segment of middle cerebral artery. An alternative way of characterizing them is proposed: it is based only on anatomic features that are likely to be of clinical relevance and represents information that is already available to the treating physician. Adopting it for presenting results of endovascular treatment of acute stroke could go at least some way toward filling the knowledge gap facing researchers in the field.