脳動静脈奇形の定位放射線治療後に発生した囊胞に対し囊胞─腹腔シャントを施行した1例

Cyst Formation after Radiosurgery for Brain Arteriovenous Malformation Treated with Cystoperitoneal Shunt

Ⅰ．は じ め に

　脳動静脈奇形に対する定位放射線治療は，外科手術，血管内治療とならび有効な治療法として知られている．しかし治療原理の違いから，定位放射線治療の合併症には放射線壊死や囊胞形成など，ほかの治療法にはない特殊な病態が含まれる．なかでも囊胞形成は定位放射線治療後に起こる合併症としてよく知られるようになってきたが，麻痺症状を呈する報告例は多くはない．

　今回われわれは脳動静脈奇形に対する2回の放射線治療後に発生した囊胞により神経症状を呈し，これに対してcystoperitoneal（C-P）シャント術が奏功した症例を経験したので報告する．

　Gamma knife and CyberKnife radiosurgery are well established and less invasive treatments for arteriovenous malformation. Delayed cyst formation is a rare but well-known complication of radiosurgery for arteriovenous malformations. The optimal treatment of cysts forming after radiosurgery remains debatable.

　We present a case of cyst formation after radiosurgery for brain arteriovenous malformation that was treated with a cystoperitoneal shunt (C-P shunt). A 36-year-old woman presented with left hemiparesis and numbness. Computed tomography (CT) revealed intracranial hemorrhage in the right basal ganglia. Digital subtraction angiography revealed arteriovenous malformation in the brain. Intravascular embolization was performed three times and radiosurgery was performed twice, whereby complete obliteration of the nidus was achieved. Six and a half years later, routine follow-up magnetic resonance imaging revealed cyst formation, and the patient gradually developed left hemiparesis. First, we performed stereotactic cyst aspiration. This initially resulted in a reduction in the size of the cyst and disappearance of left hemiparesis, but within a short time, the cyst increased in size again and there was recurrence of hemiparesis. Therefore, an Ommaya reservoir was established; aspiration of the cyst through this reservoir brought about an initial reduction in cyst size and alleviation of symptoms; however, no further reduction in cyst size or improvement in symptoms could be achieved. Twenty months after the placement of the Ommaya reservoir, we performed a C-P shunt operation. After the operation, further reduction in the cyst size and complete symptomatic recovery were observed.