椎骨解離性脳動脈瘤の興味あるMRI所見

A Characteristic Magnetic Resonance Image of a Dissecting Aneurysm in the Vertebrobasilar System

I．はじめに

　近年，解離性脳動脈瘤に対する認識が高まるにつれ，後頭蓋窩くも膜下出血の1／3を占めるとまで報告されるようになってきた．

　解離性脳動脈瘤は，本来，内膜—中膜又は，中膜—外膜の間に解離がおこり，前者では，虚血症状，後者では，くも膜下出血がおこるとされ，椎骨脳底動脈領域において重要な位置を示すようになった．原因としては．atheromatous change, minor trauma，congenital, degenerative vascular ano—malyが考えられる．

　最近，angiography等の診断技術の向上により多く発見されneurologicaletiologyに関する文献も散見されるようになった．

　今回われわれは，right lateral pon—tomedullary syndromeを呈した解離性脳動脈瘤の1例を経験し，特にMRIにてdouble lumenを示唆するintramuralhematomaをとらえるという興味深い所見を得たので若干の文献的考察を加え報告する．

Recently several reports of dissecting aneurysm in the vertebrobasilar system have been published.

We report the effectiveness of MRI for the detection of a dissecting aneurysm in the vertebrobasilar distribu-tion system. A 47 year-old female was admitted to our hospital due to right occipitalgia and the right Wallen-berg's syndrome.

Computed tomography disclosed no abnormalities.

Cerebral angiogram showed the pearl and string sign of the right vertebral artery, which suggested a dissect-ing aneurysm.

MRI exhibited the infarct area at the right dorsolateral part of the medulla oblongata, which corresponded to right Wallenberg's syndrome.

It disclosed high intensity ring-like findings circum-scribing a low intensity spot of the lumen of the right vertebral artery.

This high intensity was thought to be the hematoma between the intima and the media at the subacute stage. Its high intensity corresponded to the site of the dissecting aneurysm and of Wallenberg's syndrome. These findings are thought to be useful in the diagnosis of a dissecting aneurysm of the vertebral artery.