末梢性前大脳動脈瘤

ANEURYSMS OF THE DISTAL ANTERIOR CEREBRAL ARTERY

I．はじめに

　くも膜下出血の主なる原因は脳動脈瘤の破裂であり，この脳動脈瘤形式の原因としてはさまざまのものが挙げられているが，まだ完全に究明されたとはいえない。一応先天性，細菌性，外傷性，動脈硬化性などに分けられているが⁵），日常われわれがみるものは嚢状動脈瘤で，よく先天性動脈瘤といわれるものである。しかしこの先天性ということに疑問を持つ人も多く，最近は脳血管壁の変性を重視する意見が強い^{7,19,27,36）}。

　脳動脈瘤はWillis輪を形成する血管の分岐部，中大脳動脈の主幹分岐部に多く，それらより末梢部に発生するものは比較的少ない。

　われわれは熊本大学脳神経外科開設以来，144例（169個）の脳動脈瘤を経験したが，そのうち前大脳動脈の末梢部動脈瘤は11症例，12個である。これら動脈瘤症例には前大脳動脈の破格を伴なつたものが多いのでここに報告し，脳動脈の原因について考察する。

Aneurysms of the distal anterior cerebral arteryare relatively uncommon and consist of about 4%of the intracranial aneurysms.

In this paper 11 aneurysms of the distal anteriorcerebral arteries in 10 patients, 6.7% of the intra-cranial aneurysms experienced in our Departmentin past 5 years, were reported. 10 of them weresaccular and one was fusiform. All of them arosefrom the pericallosal artery at the genu of thecorpus callosum.

The patients with these aneurysms had higherincidence of coexisting anomalies of the anterior cerebral artery than the ordinary stastical incidencesreported from the angiographies and autopsies.

The azygos anterior cerebral artery was seen in2 cases, the supreme anterior communicating artery(Laitinen) with a saccular aneurysm on it in onecase, the defective horizontal portion of the anteriorcerebral artery on one side in 2 cases, the hypo-plastic pericallosal artery on both sides in one case,and two aneurysms of one irregular and hypoplasticpericallosal artery in one case. Two cases had otheraneurysms in the middle cerebral artery respectively.Only 3 cases showed normal features of the bilateralanterior cerebral artery.

These anomalies with the saccular aneurysmssuggested that the developemental defect inthis artery might play an important role in theformation of this aneurysm.

In analyzing clinical course of these patientscharacteristic clinical symptoms and signs suggest-ing the rupture of this aneurysm were not present.

Clipping or ligation of the aneurysm was per-formed in 7 cases and removal of the aneurysmalsac in one case with the fusiform aneurysm. Ananeurysm of the supreme anterior communicatingartery disappeared spontaneously. One patient re-fused operation. Thus 8 cases were operated with-out operative mortality.

At operation a unilateral or bilateral frontal ex-posure may be employed although a unilateralfrontal flap is adequate in the majority of casesand the aneurysm is easily found when it is ap-proached through interhemispheric fissure.