Proximal(M1 Segment) Middle Cerebral Artery Aneurysms: Clinical Features, Surgical Treatment and Comparison with Middle Cerebral Artery Bifurcation Aneurysms.

Chung, Young Seob; Oh, Chang Wan; Han, Dae Hee

Original Article

Journal of Korean Neurosurgical Society 1997;26(8): 1094-1102.

Young Seob Chung, Chang Wan Oh, Dae Hee Han

Department of Neurosurgery, College of Medicine, Seoul National University, Seoul, Korea.

ABSTRACT

The authors report a series of 26 patients with proximal(M1) middle cerebral artery aneurysms who underwent surgery. To determine whether M1 aneurysms are especially problematic, these were compared with those at the bifurcation of the middle cerebral artery(MCA). The incidence of M1 aneurysms was 3.0% among 862 patients who underwent surgery for intracranial aneurysms and 13.4% among 194 patients with MCA aneurysms : 166 patients suffered MCA bifurcation aneurysms, and six patients had both types. In M1 aneurysms, there was a greater female preponderance(1 : 2.3), and the incidence of multiple aneurysms(50%) was much higher than in MCA bifurcation aneurysms(1 : 1.2, 26%). Fifteen patients(58%) had ruptured M1 aneurysms, and these ruptured in 3(23%) of 13 patients with multiple aneurysms. Depending on their location, M1 aneurysms were classified into two types : the superior wall type(7 cases), arising at the origin of the lenticulostriate artery, and the inferior wall type(17 cases), arising at the origin of early temporal branches. Fusiform aneurysms occurred in two patients. It was noted, though was not significant statistically, that the superior wall type was more frequently associated with multiple aneurysms(57.1% vs 47.1%), and the inferior wall type was more prone to rupture(70.6% vs 42.9%). In 15 patients with ruptured M1 aneurysms, intracerebral hematomas were seen in only three(20%). This incidence was relatively low, but was similar to the incidence of 22.5%(31/138) with ruptured MCA bifurcation aneurysms. In eleven patients, besides using the medial trans-sylvian approach, we clipped the neck of M1 aneurysms using the superior temporal gyrus approach, generally used for MCA bifurcation aneurysms. Nineteen(73%) of 26 patients made a useful recovery. Two patients, who were grade II preoperatively, became severely disabled(hemiparesis and aphasia, hemiparesis) after surgery. For this to be successful, special attention to the preservation of the lenticulostriate arteries is therefore essential. Comparing the two groups of patients, however(M1 vs MCA bifurcation aneurysms), we found no difference between either preoperative Hunt-Hess grade or surgical outcome(useful recovery, 75% vs 81%).

Key Words: M1 segment; Proximal middle cerebral artery; Aneurysm; MCA bifurcation; Treatment outcome; Multiple aneurysms