Early bifurcationに発生した中大脳動脈瘤の手術  [in Japanese] Surgical Treatment of Middle Cerebral Artery Aneurysms with Early Bifurcation  [in Japanese]

中大脳動脈瘤の80-85%はbifurcationに発生し, 到達するということに関しては脳表に近いという点で最も容易である. しかしprebifurcation M1の短い, いわゆるearly bifurcationの症例では, 術前予想したより動脈瘤への到達に手間取ったり, 瘤の全周を十分に露出するのが困難なことがある. その理由は動脈瘤がsylvian fissureの比較的深部に位置したり, sphenoid ridgeやdeep sylvian veinに囲まれて術野の展開がしにくいことにある. 成書や論文の写真では明らかにそれと考えられる所見が提示されているが, early bifurcationの動脈瘤の特徴的な手術所見に関する報告は渉猟しえた範囲ではない. 著者らは最近の経験からearly bifurcationに発生した中大脳動脈瘤の手術における注意について報告する. 対象と方法 1. Early bifurcationの定義 early bifurcationの明確な定義はないが, 分岐部までのM1の長さの平均は15-16mm, 17.92mmとされている.

We report surgical treatment of 12 aneurysms located at early bifurcation of middle cerebral artery (MCA). The incidence of these aneurysms was 19.4% among 62 MCA aneurysms if the length of prebifurcation MI of 15 mm or less was designated as the early bifurcation. Eight aneurysms were unruptured, and 4 patients presented with subarachnoid hemorrhage (SAH). The maximum diameter of aneurysms was less than 10 mm in 8 cases and 10 mm to 15 mm in 4 cases. The aneurysms were classified into 2 types: those buried deep in the sylvian fissure (Type I, 8 cases) and those projected anteroinferiorly and caged by deep sylvian veins and the sphenoid ridge (Type II, 4 cases). Small bridging veins were sacrificed in 6 cases to allow wide exposure and safe manipulation, and no venous infarction was encountered postoperatively. Surgical results were excellent in all but 1 patient with SAH where post-SAH hydrocephalus brought about some mental dysfunction. The patient was the only one who developed intraoperative aneurismal rupture. To accomplish proximal arterial control and optimal neck clipping, meticulous dissection of sylvian fissure was important for Type I cases, whereas extensive but careful drilling of sphenoid ridge and the making of working space around the caged aneurysm were necessary in Type 11 cases. For the purpose, some small bridging veins were reluctantly sacrificed.