前交通動脈瘤と前交通動脈の奇形

ANTERIOR COMMUNICATING ARTERY ANEURYSMS ACCOMPANIED WITH ANOMALIES OF ANTERIOR COMMUNICATING ARTERY

I．はじめに

　脳動脈瘤の大半はWillis輪前半部に発生する。しかも，それらの症例においてはWillis輪の奇形ないし血流動態異常を伴うものが多いことが指摘されている^{1,13,14,17）}。我々は既に前交通動脈瘤例におけるWillis輪前半部の奇形または血流動態異常が約73％に認められ，そのうち94％は一側前大脳動脈A₁部の形成不全であることを指摘した^8,9）。しかも，前交通動脈瘤例においては脳血管写上優勢側のA₁と前交通動脈との分岐部に動脈瘤のoriginを有するものが非優勢側に比して3倍以上多かつた^10）。また，前交通動脈には奇形が多いといわれており，これらの奇形が血流動態の異常を起こし，その血流の強く当る血管分岐部，すなわち血管の弱点から動脈瘤が発生^12）するものと考えられている。既に前大脳動脈A₁形成不全と前交通動脈瘤との関係については報告^8〜10）してあるので，今回は前交通動脈の奇形を合併した前交通動脈瘤について検討を加えた。

The investigation was carried out on arterial anomalies complicated with 296 cases of single aneurysm of anterior communicating artery and on the etiological significance of the anomalies in the development of cerebral aneurysms.

Either the fenestration in anterior communicating artery or the presence of more than 2 anterior communicating arteries was observed in 17 cases (5.7%), and abnormal vessels of anterior communi-cating arterial origin, such as a median artery of the corpus callosum, were observed in 13 cases (4.4%). As the anomaly was duplicated in some of these cases, the total number of cases with anomalies of anterior communicating artery became to be 26 cases (8.8%) out of 296 cases investigated. This occurrence rate was not higher than those observed in other cerebral aneurysmal cases and the control cases, which were reported previously. There was no significant difference as to the oc-currence rate of the hypoplasia of the A₁ portion between the cases whose aneurysms of anterior communicating artery were complicated with arterial anomalies and the cases without the arterial anomalies.