The surgical strategy of exposing M1 segment in the clipping of the middle cerebral artery bifurcation aneurysms

Abstract

Objective To explore the strategy of exposing M1 segment safely in the craniotomy clipping surgery of the middle cerebral artery bifurcation(MCBIF) aneurysms. Methods The clinical data of sixty patients with sixty-five MCBIF aneurysms performed surgical management between March 2012 and March 2018 in Shanxi Dayi Hospital were retrospectively analyzed, including 29 males and 31 females, with the onset age ranging from 35 to 65(40±0.5) years old. There were 3 cases in level 0, 13 cases in levelⅠ, 13 cases in level Ⅱ, 16 cases in level Ⅲ, 7 cases in level Ⅳ, 8 cases in level Ⅴ by aneurysm bleeding Hunt-Hess classification in admission. The MCBIF aneurysms were divided into projecting superiorly (27), projecting laterally (22) and projecting inferiorly (16) according to the coronal planes of MIP. Meanwhile the length of M1 segment was measured and the curvature of M1 segment was observed in the ipsilateral middle cerebral artery of the aneurysm. Reconstructed images to simulate the pterional approach. The sylvian fissure was splitted by proximal or distal approach. The M1 segment was exposed from its upward side for the aneurysm that projecting inferiorly and laterally. Alternatively, the M1 segment was exposed from its downward side for the aneurysm that projecting superiorly. The right clips should be selected to occlude the aneurysms. All patients were followed up to observe aneurysm reappear. Glasgow outcome score (GOS) was used for prognosis evaluation. The difference in prognosis of aneurysm with different projection was compared. Results The length of M1 segment was 8.2-16.5(13.5±0.3) mm. Projection of the aneurysms depended on the curvature of M1 segment: the projection superiorly with the downward curvature, the projection inferiorly with the upward curvature and the projection laterally with straight M1 segment. The anatomic relationship between the aneurysm and its parent artery in the 3D-CTA image of simulated pterional approach was in accordance with the actual condition in operation. All aneurysms were clipped and didn't reappear in 6 months after surgery. The follow-up period was 6 to 36 months(Mean 18.0±2.5 months). The GOS was 5 in 37 cases, 4 in 10 cases, 3 in 4 cases, 2 in 3 cases, and 1 in 6 cases according to the last follow-up. There was no statistically significant difference in the favorable prognosis rate of the aneurysms with different projection. (P>0.05). Conclusions We should make full use of the technology of 3D-CTA to identify the projection of the aneurysm and both the length and curvature of M1 segment, assess accurately the orientation of the aneurysm and M1 segment in sylvian fissure. In this way, we can avoid the dome of aneurysm, take the appropriate strategy to expose M1 segment and accomplish effectively the proximal control of the parent artery. These strategies are the reliable guarantee for the operation safety. Key words: Middle cerebral artery; Intracranial aneurysm; Imaging, three dimensional; Computed tomography angiography; Surgical strategy