[A case of anterior cerebral artery dissecting aneurysm]

The incidence of intracranial dissecting aneurysms is lower than that of berry aneurysms. Following the recent spread of the use of cerebral angiography, however, 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 literature, only 17 cases of dissecting aneurysm of the anterior 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 October 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 day, revealed low density in the area supplied by the right anterior cerebral artery. An angiogram 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 treated 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 hemorrhagic type, who were treated conservatively, died.