前大脳動脈の解離性脳動脈瘤の経験

An Experience of Dissecting Cerebral Aneurysm of the Anterior Cerebral Artery

I．はじめに

　頭蓋内の解離性脳動脈瘤（以下DCA）は比較的稀な疾患と考えられてきたが，脳血管造影の普及により報告例が増加してきた^22,24）．本症は脳梗塞の素因の少ない健康な若年者に多く，中大脳動脈（以下MCA）や椎骨脳底動脈（以下VA-BA）に発生しやすいと考えられている^19）．しかし前大脳動脈（以下ACA）に発生したDCAの報告は少なく文献上渉猟し得た症例は14例であった^{1,3,7,11,12,14,22,26）}．最近われわれはACAに発生し良好な経過を示したDCAの1例を経験したので，若干の考察を加えて報告する．

Intracranial dissecting aneurysms have been reported occasionally in recent years. However, excluding dissect-ing aneurysms which extend from the proximal intracra-nial carotid artery, dissecting aneurysms arising merely in ACA are found only rarely.

We are reporting here a case of a 42 year-old gentle-man who did not present any particular causative etiolo-gy such as trauma or other basic diseases causing arte-ritis. Our patient is the 8th case, as far as we could find in the literature, in which the dissection of the arterial wall originated at the ACA. The patient was thought to have a tiny saccular aneurysm at the A 1-2 junction of the right ACA associated with vasospasm in the distal ACA on the angiogram. The patient had motor weakness on the left side and headache as well as a low density area in the territory of the ACA on the CT scan. A craniotomy was performed verifying the aneurysm to be dissecting in type without any sign of recent subarachnoid hemor-rhage in the surrounding structures. No aggressive surgic-al treatment such as trapping of the aneurysm was done because the collateral blood circulation in that territory of the distal right ACA seemed to he poor and the pa-tient no longer had neurological deficit at the time of op-eration. The patient was treated successfully with anti-platelet therapy. On the follow-up angiogram performed 3.5 months after the onset of the illness, we noted the disappearance of the abnormal angiographical findings of the dissecting aneurysm and distal arterial narrowing (pearl and string sign).

Our impression is that dissecting aneurysms arising at the ACA evolve with a less severe clinical course than that of dissecting aneurysms in the intracranial carotid artery or middle cerebral artery.