Blister-likeからSaccular typeへと変化した内頸動脈前壁動脈瘤の1手術例

A Successfully Treated Case of a Ruptured Anterior Wall Aneurysm of the Internal Carotid Artery (C2) which Changed in Form from Blister-Like to Saccular Type

　Ⅰ．はじめに

内頸動脈前壁動脈瘤は内頸動脈C₂部の前壁に血管分岐とは無関係に生じる動脈瘤を指し，その頻度は全内頸動脈瘤の0.9～6.5％と報告されている^9,11)．一般に内頸動脈前壁動脈瘤は通常の囊状動脈瘤のようなneckがなく形態的にはチマメ型またはblister type aneurysmと表現され，動脈瘤壁が脆弱であることより直達手術のリスクが高く，根治術も困難とされている^9,10)．

　今回われわれは，初回脳血管撮影にてblister-like aneurysmの形状を認めたが，経過中に囊状増大様の変化を呈し，待機的にネッククリッピングを行い得た内頸動脈前壁動脈瘤の1例を経験した．そこで本症例の経時的な形態変化と治療方針を中心に文献的考察を加えて報告する．

　We successfully treated a case of ruptured anterior wall aneurysm of the ICA (C₂) which changed in form from blister-like to saccular type. A 46-year-old woman developed subarachnoid hemorrhage on July 12,2002. Cerebral angiogram demonstrated a blister-like aneurysm located in the left C₂ portion of the internal carotid artery,but which didn't affect the arterial branches. Because of the risk of premature rupture during early surgery,delayed surgery was scheduled and the patient underwent serial study of the aneurysm. During 2 weeks of follow-up,the shape and size of the aneurysm changed in form blister-like to an enlarged saccular type aneurysm. On the day 18th,a left epi-subcombined approach,after insertion of a balloon catheter into the cervical ICA,was attempted and the aneurysm projecting antero-medially under the left carotid artery was exposed. The aneurysm had a distinct neck and its wall was not fragile. There was no macroscopic evidence of dissection of the ICA and the aneurysm was successfully clipped by conventional manipulation. Because of the difficulty in determining by angiographic evidence alone,whether an anterior wall aneurysm is a blister type or saccular type,careful follow-up is needed and if the shape or size changes,immediate appropriate treatment becomes mandatory. Intraoperative observation will determine the final diagnosis,as in this uncommon case.