椎骨動脈—後下小脳動脈解離性動脈瘤Trapping術後，Hyperperfusion Pressure Breakthroughによる小脳出血を来たしたと考えられる1症例

Postoperative Hemorrhage due to Normal Pressure Hyperperfusion Breakthrough after a Trapping of VA-PICA Dissecting Aneurysm

I．はじめに

　解離性動脈瘤の破裂によるsubarachnoid hemor-rhage（SAH）の頻度は，近年digital subtraction angiography（DSA）や3 dimension computed tomography（3D-CT），magnetic resonance im-ages（MRI）等の検査機器の進歩普及によって増加している．一般的に椎骨動脈系の解離性動脈瘤ではSAHにて発症する症例が多く，内頸動脈系では血管閉塞による脳梗塞で発症する場合が多いと言われている^16,17）．その治療方法は，最近では血管内治療による報告も散見されるが^11），明らかな頸部を持たない解離性動脈瘤の場合，一般的にはproximal clippingもしくはtrappingが有効であると思われる．

　今回われわれはSAHにて発症し，右椎骨動脈—後下小脳動脈分岐部（VA-PICA）よりdistalのVAに発生した解離性動脈瘤に対してtrapping術を施行し，その翌日病側PICA領域に出血を来たした症例を経験したので，その発生原因について若干の文献的考察を加えて報告する．

We described a case of cerebellar hemorrhage after trapping of a vertebral artery dissecting aneurysm. A forty-eight-year-old man had suffered from severe headache, vomiting and disturbance of consciousness. He was transferred to our hospital in an ambulance. Emergency CT scan showed subarachnoid hemor-rhage in the posterior fossa predominantly, intraventricular hemorrhage and hydrocephalus change. Chest X-ray showed radiological evidence of pulmonary edema. The initial blood-gas determinations demon-strated a marked reduction in PaO₂ and increased PaCO₂. Five days after admission, the patient's condi-tion was improving. Cerebral angiography was performed using the Seldinger method. It revealed a right vertebral artery dissecting aneurysm just distal to the posterior inferior cerebellar artery. We performed an operation to trap the VA dissecting aneurysm. Blood pressure was well controlled under 140mmHg during the operation and he recovered from anesthesia completely. On the day after the operation, suddenly the patient's consciousness began to deteriorate. Emergency CT scan was performed and it showed SAH, cere-bellar hemorrhage and diffuse swelling of the cerebellum on the same side as the operation. We suspected rebleeding of the aneurysm due to a clip's having slipped. Reoperation was performed, but the clip was not displaced and there were no definite bleeding vessels on the operative field. Consequently only external de-compression and resection of the right cerebellum were performed. We discuss pathogenesis of the occur-rence of hemorrhage in this particular case after trapping. We also review the relevant literature.