Willis 動脈輪前半部の動脈瘤の手術

Abstract

Operation of the aneurysm at the anterior part of Willis ring is one of the most common surgeries in the neurosurgical field and a large number of excellent textbooks or articles about this surgery have been published. From my personal experience of 485 cases, I have noticed several ways to rapidly complete clipping-surgery. Rapid surgery never means hasty surgery, but precise step-by-step surgery will lead to rapid surgery. Thus, no procedure should ever be done hastily. I offer the following four tips: 1) The surgeon should ensure complete hemostasis at each surgical step, which will make the following microscopic dissection smoother. 2) The surgeon should be aware of the appropriate steps of arachnoid dissection. The different steps should be considered based on the aneurysm's location. In the case of internal carotid (IC) aneurysm, the chiasmatic cistern should first be dissected to preserve the proximal IC for possible premature rupture. The proximal Sylvian fissure is then be opened, and finally the neck of the aneurysm should be carefully dissected. In the pterional approach for the anterior communicating aneurysm, the Sylvian fissure should first be opened widely, which will make the frontal lobe relaxed against the following surgical retraction. The proximal IC, chiasmatic cistern, and interhemisphric fissure should then be dissected in order. As for the middle cerebral (MC) aneurysm, I prefer to approach from the distal side, since the initial dissection of the proximal MC may sometimes be difficult behind the aneurysmal dome. 3) The appropriate method of arachnoid dissection should be practiced. The most important point is for the left hand to make the arachnoid membrane tensional for the correct observation of the dissecting plane. 4) The operative field should be properly expanded. For this purpose, the microscope and self-retractor should frequently be replaced. With the use of these techniques, the overall outcome of my department has improved a great deal. Although approximately 40 percent of the patients with subarachnoid hemorrhage belong to WFNS Grade IV or V in my clinic, the ratio of independent patients (Glasgow Outcome Scale; GR+MD) has significantly increased from 61.7%to 69.7%in the past four years. Since the number of neurosurgeons in Japan is increasing greatly, neurosurgeons are experiencing less surgery. Thus, these surgical tips should be helpful for inexperienced neurosurgeons.