前大脳動脈dolichoectasiaの1症例

A Case Report of Dolichoectasia of the Anterior Cerebral Artery

Ⅰ．はじめに

　Dolichoectasiaは稀な病態であり，罹患動脈のほとんどは脳底動脈や内頚動脈である．とりわけ，前大脳動脈のdolichoectasiaは極めて稀である^1,24)．Dolichoectasiaによって引き起こされる病態に関しては，虚血性・出血性イベントに加え，周囲構造への直接的圧迫による脳神経麻痺などが報告されており，以前にもいくつか報告例はあるものの^5,7,19)，dolichoectasia自体によって引き起こされる脳循環動態の変化に関する報告はわれわれが渉猟し得た限りではそれほど多くない^7,15,18)．

　今回われわれは，前大脳動脈のdolichoectasiaにおいて，その灌流領域に脳血流低下を呈した症例を経験したので文献的考察を加え報告する．

　Dolichoectasia of the intracranial arteries is a rare condition,and the vertebrobasilar system and the internal carotid artery is most commonly involved. We describe a rare case of a 60-year-old man with dolichoectasia of the anterior cerebral artery (ACA). The patient presented with continuous vertigo and nausea. CT and MR imaging showed a prominent serpentine structure with calcification and flow void in the region of the interhemispheric fissure,findings which were suspicious for arteriovenous malformation (AVM) or fistula (AVF). A cerebral angiogram demonstrated an extensive dilatation of the ACA above the level of the anterior communicating artery. There was no evidence of AVM or AVF. Although SPECT study revealed a decrease of cerebral blood flow (CBF) in the right frontal lobe,cerebrovascular reserve,as demonstrated by acetazolamide challenge was sufficient for maintenance. Decrease of CBF may have resulted from diaschisis or selective neural cell elimination by old cerebral infarction. The patient was treated with an anti-platelet agent conservatively and the symptoms gradually improved. Cerebral angiography may be needed for definitive diagnosis because cerebral dolichoectasia may mimic CT and MR imaging findings of AVF or AVM. Cerebral hemodynamics must be examined strictly in addition to demonstrating vascular disease by angiography,and SPECT study may play a role in the detection of hemodynamic change induced by dolichoectasia.