前下小脳動脈圧迫による外転神経麻痺に対して微小血管減圧術が奏効した1例

Microvascular Decompression to Treat Abducens Nerve Paralysis Caused by Compression of the Anterior Inferior Cerebellar Artery:A Case Report

Ⅰ．はじめに

　微小血管減圧術（microvascular decompression：MVD）は，顔面痙攣や三叉神経痛などに対して効果的であるが，外転神経麻痺における報告は少なく，診断や治療方針に苦慮することがある．今回，前下小脳動脈（anterior inferior cerebellar artery：AICA）圧迫による外転神経麻痺に，右椎骨動脈（vertebral artery：VA）—後下小脳動脈（posterior inferior cerebellar artery：PICA）動脈瘤を合併した症例を経験し，外転神経麻痺に対してAICA transpositionによるMVD，VA-PICA動脈瘤に対して右後頭動脈（occipital artery：OA）-PICA bypass＋VA近位部とPICA起始部のclippingを一期的に施行し，外転神経麻痺の著明な改善を認めた．診断と治療方法に関して文献的考察を加えて報告する．

　Microvascular decompression（MVD）is an effective treatment for hemifacial spasm and trigeminal neuralgia. However, there are few reports regarding its use with abducens nerve palsy. Here, we report the case of a 77-year-old male who presented with diplopia and was admitted to our facility for right abducens nerve palsy. MRI constructive interference in steady-state（CISS）showed that the right anterior inferior cerebellar artery（AICA）was curved in a posterior-superior direction at the beginning of the region of origin, causing compression of the root exit zone of the right abducens nerve. In addition, MRI showed an unruptured fusiform aneurysm（5.3mm×7.1mm）of the vertebral artery（VA）involving the posterior inferior cerebellar artery（PICA). However it was not related to abducens nerve paralysis. The aneurysm was successfully treated with an occipital artery-posterior inferior cerebellar artery（OA-PICA）bypass and clipping of the proximal VA and PICA origin. The position of the offending artery was moved using a Teflon^® felt fibrin glue and the retrosigmoid transcondylar fossa approach. The patient recovered from abducens nerve paralysis with no new neurological deficit. We emphasize the importance of choosing an appropriate approach as this increases the possibility of treating abducens nerve paralysis in a timely manner.