2004 Volume 32 Issue 6 Pages 408-415
The surgical treatment of the middle cerebral artery (M1-2 bifurcation) aneurysm (MCA AN) employs the pterional approach and comprises much of aneurysm surgeries. But the surgical management of MCA AN remains a technically challenging problem especially for inexperienced neurosurgeons. This is largely caused by the difficulty of securing the M1 artery as the parent artery before exposing the whole aneurysm.
In this study, we retrospectively analyzed the relationship between the approaches and operative difficulties in 90 MCA ANs in 86 of our patients operated on by the same neurosurgeon (K.U.). The variations of the MCA ANs were classified according to the following 3 points: the length of M1, M1 configuration on the angiogram (antero-posterior view), and the aneurysmal dome direction to M2. We subdivided the pterional approach into the following 4 groups: 1) the proximal approach (PA) to secure the proximal M1 after having controlled the internal carotid artery, 2) the distal approach (DA) to secure the distal M1 in the space between M2 arteries after having opened the distal sylvian fissure, 3) the superior approach (SA) to secure the distal M1 after having opened the distal sylvian fissure and followed the medial surface of M2 superior trunk, and 4) the inferior approach (IA) to secure the distal M1 after having opened the distal sylvian fissure and followed the lateral surface of M2 inferior trunk.
The PA is effective in the cases of short M1 but in the cases of long M1 the DA is effective. The PA is safe for the cases in which the direction of the aneurysm is at the medial side of M2 arteries. On the other hand, in the cases in which the direction of the aneurysm is lateral to the M2 arteries, DA and SA are safe. In view of the results, we designed a scoring system to indicate the difficulties of securing M1 as the parent artery regarding the above-mentioned 3 points. Using these scores, we were able to decide the optimum approach preoperatively. To secure the parent artery is indispensable to safe aneurysm surgery. Comparing the points of each approach to the aneurysm with this scoring system, we were able to construct a better and safer micro-dissection plan with the goal of securing the parent M1 artery, and perform the operation by following the pre-operative plan. Surgical success or failure is determined by preoperative planning.
