くも膜下出血にて発症した頭蓋頚椎移行部の動静脈瘻に関する検討

Characteristics and Treatment of Dural and Perimedullary Arteriovenous Fistula at the Craniocervical Junction Presenting with Subarachnoid Hemorrhage

Ⅰ．はじめに

　脊髄動静脈奇形，動静脈瘻の分類は，動静脈短絡の局在部位から，髄内に動静脈短絡，nidusを有する髄内動静脈奇形（intramedullary arteriovenous malformation），nidusはほとんどなく脊髄表面に動静脈瘻を有する脊髄辺縁部動静脈瘻（perimedullary arteriovenous fistula：perimedullary AVF），根動脈が直接シャントする硬膜動静脈瘻（dural AVF）に分類されている^12,15-17)．

　脊髄dural AVFは脊髄血管奇形の中で最も頻度の高い疾患であり，そのうち頭蓋頚椎移行部のdural AVFは，胸・腰髄でのdural AVFが進行性対麻痺を呈することが多いのに比べて，くも膜下出血や静脈うっ滞による脊髄症状で発症することが多い^5,13)．

　治療は，頭蓋内dural AVFでは血管内治療を第一選択とする場合が多い．その一方で頭蓋頚椎移行部のdural AVFの場合は，塞栓すべき静脈洞がなく，流入動脈は椎骨動脈が主体でシャントまでの距離が非常に近く，脳幹・脊髄梗塞などの合併症発生率が高いため，外科的治療が一般的とされている^11,20)．

　頭蓋頚椎移行部は頭蓋内と脊髄，二者の病態が混在する部位であり，診断や治療に難渋することが多い．今回，われわれは頭蓋頚椎移行部のdural AVFおよびperimedullary AVFによるくも膜下出血を5例経験したので，その病態と治療方法に検討を加え報告する．

　Dural and perimedullary arteriovenous fistula (AVF) at the craniocervical junction tend to cause subarachnoid hemorrhage (SAH). However,their natural history and clinical manifestations still remain to be elucidated. From 2003 to 2009,we encountered 5 cases of dural and perimedullary AVF presented with SAH. They were all male,ranging in age from 53 to 85 year-old (mean: 68 year-old). Rebleeding occurred in 1 patient on day 11. Outcome estimated by modified Rankin Scale did not change remarkably from 2.6 on admission to 2.4 at 3 months later on average. Cerebral angiography and 3D-CT angiography disclosed feeders originating from radicular or intracranial vertebral arteries which drained into the epidural venous plexus or spinal meningeal veins. One patient died of systemic complication during his clinical course. Thus we performed open surgery in the remaining 4 patients. Of these,we failed to occlude feeders completely in the initial surgery without intraoperative digital subtraction angiography (DSA) in 2 patients. Following this treatment we performed coil embolization and repeated open surgery with the aid of intraoperative DSA,respectively. In 1 patient out of the remaining 2 patients,we utilized intraoperative DSA to confirm complete disappearance of AVF composed of multiple feeders. These observations show that SAH caused by dural and perimedullary AVF at the craniocervical junction should be mainly treated by open surgery with the aid of intraoperative DSA in order to accomplish obliteration of the feeders because,otherwise,we might fail to confirm complete disappearance of AVF.