内頚動脈海綿静脈洞部巨大・大型動脈瘤の治療戦略

Strategy for the Treatment of Large-giant Aneurysms in the Cavernous Portion of the Internal Carotid Artery

Ⅰ．はじめに

　内頚動脈海綿静脈洞部巨大・大型動脈瘤は，直達手術が困難であるため内頚動脈閉塞術が行われる^3,4,7,10,26)．その際，遠位部の局所的脳虚血を予防するために，血行再建術を行う場合がある．血行再建術の必要性については，普遍的もしくは選択的の2つの考え方があるが，後者では術前のバルーン閉塞試験（balloon occlusion test：BOT）の所見により決定されることが多い^3,9,32)．BOTは，主幹動脈の一時遮断や永久閉塞の可否を評価する術前試験であるが，方法は各施設によって異なるのが現状である．本試験自体の合併症や偽陰性の問題もあり^15,18,19)，試験結果に基づいた治療結果に関する分析は，一定の見解が得にくい．今回われわれは，自験例の海綿静脈洞部内頚動脈瘤における術前BOTの結果と治療結果に関して検討し，BOTと血行再建術の意義について文献的考察を加え報告する．

　The treatment of a large-giant aneurysm in the cavernous portion of an internal carotid artery（ICA）requires occlusion of the ICA, with or without extracranial-intracranial（EC-IC）bypass surgery. Although a balloon occlusion test（BOT）is used to determine the need for bypass surgery and select the bypass type, the criteria are not well established. In this study, we retrospectively analyzed 10 consecutive patients（11 sides）with cavernous large and giant aneurysms treated during the past 8 years. Therapeutic strategies for each patient were selected according to the results of neurological and radiological examinations, and regional cerebral oxygen saturation. A total of 6 high-flow bypasses were placed before ICA occlusions. Three patients had STA-MCA bypasses before ICA occlusions, and two underwent endovascular ICA occlusion without bypass surgery. Favorable outcomes were obtained in all cases with respect to cranial nerve palsy, but one patient had insufficient ipsilateral cerebral blood flow postoperatively, and hemiparesis was revealed. An emergent STA-MCA bypass was performed in this case, which minimized the hemiparesis. Despite radiological evaluation during the BOT procedures, we had one false negative result. This indicates that the BOT requires increased sensitivity and specificity, and that a safety margin should be adopted when determining indications for bypass surgeries.