海綿状血管腫に対する定位放射線治療の現状

Stereotactic Radiosurgery for Intracranial Cavernous Malformations

はじめに

　海綿状血管腫（cavernous malformations：CMs）はcavernous angiomas，cavernomas，cryptic vascular malformationsとしても知られており，また従来angiographically occult vascular malformations（AOVMs）と分類されていたもののほとんどが海綿状血管腫であったと言われている^1）。中枢神経系海綿状血管腫は先天性脳血管奇形の一種として分類され，真の腫瘍性病変とは異なりその多くが臨床的におとなしい性格の病変と考えられている。しかし，新規に（de novo）病変が出現することや^2－4），経過中に増大・出血・退縮などのdynamicな変化を見せる病変でもあり，それに伴い頭痛，痙攣，脳出血，神経局所症状を呈する^2－5）。一部の症例では繰り返す出血のために不良の転帰をたどることもある^6，7）。近年MRIなど検査機器の急速な普及により，無症候性で発見される頻度が高くなっており^8，9），本疾患の自然歴を解明し，それに基づく適切な治療方針を決定することの必要性が高まっている。近年いくつかの重要なレビューが相次いで報告され^10－12），海綿状血管腫の自然歴や定位放射線手術の有用性について包括的に理解する機会をわれわれに与えてくれることとなった。本稿では，これらを参考に解説を行っていきたい。

Abstract

　Cavernous malformations (CMs) consist of dilated vascular channels that have a characteristic appearance on MRI.　They can present with seizures,neurological deficits due to lesion hemorrhage,or as incidental findings on neuroradiological studies.　Treatment options include conservative therapy; medical management of seizures; surgical intervention; and in selected cases,stereotactic radiosurgery.　The role of radiosurgery in the treatment of CMs remains controversial,in part,because of the absence of neuroimaging criteria to gauge their successful obliteration as well as its higher complication rates.　Radiosurgery is recommended only for symptomatic lesions that are surgically inaccessible or located in eloquent brain.　We reviewed previously published papers on CMs with respect to hemorrhage rates,seizure control,and radiation-induced morbidity in order to better understand the balance of benefits and risks associated with the radiosurgical treatment for CMs.　The data in this review provides convincing evidence that stereotactic radiosurgery is a relatively safe procedure with acceptable risks of morbidity and that its use could reduce the rebleeding rate and the frequency of seizures caused by for CMs located in the high-surgical-risk regions of the brain.　We also present our experience of treating for 16 patients with CMs and show that our results were comparable to those previously reported.