The characteristics of the anterior communicating artery aneurysm complex by three-dimensional digital subtraction angiography.

To elucidate the three-dimensional structure of the anterior communicating artery complex, we performed three-dimensional digital subtraction angiography in anterior communicating (Acom) aneurysm cases. Eighteen patients (six male and 12 female) with Acom aneurysms were studied. The total number of aneurysms was 18, of which three were unruptured and 15 were ruptured. Aneurysmal sizes and angles between the parent artery and each of the two daughter arteries were measured. Two types were defined, based on the daughter arteries. When the sizes of the two daughter arteries were the same, they were defined as AA' type, and when different, they were defined as AB type. Furthermore, aneurysms were classified into two types based on neck location. Thus, when the neck was located on the extension of the midline of the parent artery, it was defined as classical neck type, and when it was not, it was defined as deviating neck type. There were 11 cases of AA' type and seven of AB type. In AA' type all cases were of the classical neck type, and in AB type three cases were of the classical neck type and three were of the deviating neck type. In the deviating neck type, the necks were deviated to the smaller daughter arteries in all cases.