Bihemispheric ACA分岐部に発生した破裂脳動脈瘤の1例

Ruptured Aneurysm of Bihemispheric Anterior Cerebral Artery Bifurcation： Case Report

Ⅰ．はじめに

　遠位部前大脳動脈（distal anterior cerebral artery；DACA）に発生する脳動脈瘤は，動脈瘤全体の2.0～9.0％とされており比較的稀である^3-5,7-14)．その中でもsupracallosal portion （A4-A5）に発生する脳動脈瘤は，DACA動脈瘤全体の約6％と極めて稀である⁹⁾．また，DACA動脈瘤の特徴として，azygos ACA，bihemispheric ACA，third A2などの前大脳動脈（anterior cerebral artery; ACA）の走行異常を伴うことが多いとされているが，その大部分はazygos ACAに合併した例である^1,5,10,15)．

　今回，われわれは，bihemispheric ACAの分岐部に発生したDACA脳動脈瘤破裂によりくも膜下出血を来した1例を経験したので文献的考察を加えて報告する．

It is well known that distal anterior cerebral artery (ACA) aneurysms are often associated with the anomalies of the ACA,of which azygos ACA and triple ACA have frequently been described. In this report,we present a rare case with a ruptured aneurysm arising from the bifurcation of the bihemispheric ACA,a rare anomaly of the ACA. A 63-year-old male suddenly developed severe headache,consciousness disturbance,and left hemiparesis,and was admitted to our hospital. Plain CT scans revealed subarachnoid clots that were densely distributed in the supracallosal cistern. Cerebral angiography demonstrated that the left pericallosal artery supplied blood flow to the bilateral parietal lobes through the bihemispheric arteries. A saccular aneurysm was found at their bifurcation. He underwent clipping surgery through interhemispheric approach. Postoperative course was uneventful. Special care should be taken not to occlude the bihemispheric arteries supplying to the bilateral parietal lobes during surgery.