前大脳動脈解離性動脈瘤の1例

A case of anterior cerebral artery dissecting aneurysm

I．はじめに

　頭蓋内の解離性動脈瘤は嚢状動脈瘤に比較して発生頻度は著しく少ない^{9,13,15,19）}．脳血管造影検査の普及により，頭蓋内の解離性動脈瘤の症例報告も増えつつある^{9,13-15,18）}．しかしそれらの多くは内頸動脈，中大脳動脈，椎骨動脈に発生している^1,9,13,15）．前大脳動脈に限局して発生した解離性動脈瘤の症例報告はわれわれが文献を渉猟した限りでは16例のみであった^{1,2,4-16,18）}．今回われわれは右前大脳動脈のA2に限局した解離性動脈瘤の1症例を経験したので，文献的考察を加え報告する．

The incidence of intracranial dissecting aneurysms is lower than that of berry aneurysms. Following the re-cent spread of the use of cererbral angiography, howev-er, the number of patients identified as having this type of aneurysm has been increasing. In a majority of cases of intracranial dissecting aneurysms, the aneurysm afflicted the vertebral and basilar arteries. After these, the internal carotid artery and the middle cerebral artery are the next most frequently affected. It is very rare that this type of aneurysm develops in the anterior cerebral artery.According to our search of the litera-ture, only 17 cases of dissecting aneurysm of the anter-ior cerebral artery have been reported to date (including the case to be presented here). The case we recently encountered was that of a 52-year-old male. On Octber 25, 1994, the man suddenly developed a headache and strong paresis of the left leg while performing clerical work. The plain head CT, taken next clay, revealed low density in the area sup-plied by the right anterior cerebral artery. An angio-gram taken 6 days after onset disclosed characteristic signs of dissecting aneurysm (i.e., double lumen, etc.) at the A2 segment of the right anterior cerebral artery, as well as the presence of non-ruptured berry aneurysms at the bifurcation of the right middle cerebral artery. The non-ruptured berry aneurysms were treated by neck clipping, while the dissecting aneurysms were tre-ated conservatively. The patient was discharged on March 21, 1995, without needing any assistance to walk.

We analyzed the 17 reported cases of dissecting aneurysms of the anterior cerebral artery. The cause of this aneurysm was often hypertension, and only 3 of the 17 cases were rated as being idiopathic cases. The site of this aneurysm was often the pericallosal artery (segments A2, A3, etc.). Of the 17 patients, 11 were middle-aged or elderly (over 40). The male-to-female ratio was 13: 4, indicating a predominance of males. The incidence did not differ significantly between the right and left hemispheres. The number of ischemic cases was more than double that of hemorrhagic cases. Most ischemic cases had a good prognosis, even when treated conservatively. All 3 patients with the hemor-rhagic type, who were treated conservatively, died.