脳梁出血で発症した一側性内頸動脈形成不全症―1例報告と文献的考察

Aplasia of the Right Internal Carotid Artery Presenting with Callosal Hemorrhage : Case Report and Review of the Literature

Ⅰ．はじめに

　内頸動脈欠損・形成不全は稀な先天性の血管奇形で，脳血管撮影で0.004％⁸⁾，剖検で0.01％以下¹³⁾の頻度でみられ，脳循環動態の異常によって血行力学的負荷が生じ，脳動脈瘤を高率に合併する⁶⁾．脳動脈瘤の破裂によるくも膜下出血，脳出血や脳虚血発作などで発症する例と無症候性例が存在する．今回，われわれは内頸動脈形成不全に伴い形成された前大脳動脈 （anterior cerebral artery；ACA）の側副血行路から脳梁出血を起こした高齢者の1例を経験したので，文献的考察を加えて報告する．

A 73-year-old woman without a history of cerebral ischemia suffered from sudden onset headache. Brain computed tomography (CT) showed intracerebral hemorrhage in the corpus callosum with intraventricular hemorrhage and thin subarachnoid hemorrhage in the basal cistern.

　Cerebral angiography showed narrowing of the right internal carotid artery just distal to its origin in the neck and abrupt occlusion just after branching of the ophthalmic artery with moyamoya-like vessels. The right A2 segment showed irregular dilatation and stenosis. The right middle cerebral artery was supplied from the basilar artery via the right posterior communicating artery. There was neither aneurysm nor arteriovenous malformation.

　Thin-slice bone-window CT of the skull base revealed hypoplasia of the right carotid canal. Aplasia of the right internal carotid artery was diagnosed. The origin of the hemorrhage was thought to be the irregularly opacified right A2 segment,which had been subjected to long-standing hemodynamic stress as collateral vessel.