Abstract
Neurosurgeons have 2 established approaches for the anterior communicating artery aneurysm (ACoAn): pterional (PT) and interhemispheric (IH). To elucidate which approach best suits various types of ACoAn, we studied angiograms from 202 consecutive operated cases. ACoAn can be classified into 4 groups by the direction of neck protrusion: anterior/inferior (AI: 43%), superior (SUP: 23%), posterior/superior (POST: 2%) and lateral (LAT: 32%). The LAT type is a peculiar aneurysm defined as protruding its neck and the dome sideways contralateral to the dominant A1. It is hard to recognize this type well on lateral projection angiogram because its neck and the dome are superimposed on the A1-A2 corner that the aneurysm arises from. In LAT, the dominant A1 is overwhelmingly on the left side (73.8%), while in the other types, the left A1 predominance is not observed (the left A1 dominant in 31.4%, the right A1 dominant in 32.8% and epui-A1 in 35.8%). Ninety percent of AI were operated on by PT. For the SUP type, both PT (48%) and IH (41%) were employed, depending on the size and shape of the dome and height of the neck from the frontal base. The LAT and POST type were clipped safely by IH (75.4 and 75.0%, respectively). Though LAT can be clipped by PT from the side of the neck protrusion getting over the dome (16%), this is apparently more difficult and risky than by IH. We present typical cases operated on both by PT or IH in each ACoAn type with annotations concerning surgical indications and techniques.
