Anterior interhemispheric approach for distal anterior cerebral artery aneurysm surgery: preoperative analysis of the venous anatomy can help to avoid venous infarction

Background. The anterior interhemispheric approach is a well-known operative technique for a distal anterior cerebral artery (ACA) aneurysm. However, a frontal parasagittal bridging vein is occasionally sacrificed in this approach, creating a risk of postoperative venous infarction. Method. To evaluate the risk of venous infarction, the current study investigated the venous phase of preoperative angiograms and postoperative CT scans for 20 patients in whom a parasagittal bridging vein had been sacrificed during the anterior interhemispheric approach. The draining territory index of the sacrificed bridging vein (DTISBV), draining territory index of the adjacent collateral ascending draining veins (DTIADV), and drainage impediment index (DII) were all calculated, plus the development of the superficial Sylvian vein (SSV) was evaluated. Findings. Extensive postoperative venous infarction occurred in two of four patients with an aplastic SSV, for whom the DTISBVs were 41% and 43%, and the DIIs 26% and 37%. Among 16 patients with a normal SSV, two patients suffered postoperative venous congestion, and their DTISBVs were 40% and 50%, and their DIIs 21% and 30%. The other 14 patients without any postoperative venous drainage problems had a lower DTISBV and DII, where the DTISBV was 22.3+/-6.8% (mean+/-SD) and the DII 4.3+/-8.1%. Conclusions. The present results suggest that the venous phase of a preoperative angiogram should be carefully evaluated before distal ACA aneurysm surgery. In particular, a DTISBV and DII over 50% and 30%, respectively, in patients with a normal SSV and over 40% and 25%, respectively, in patients with an aplastic SSV were found to be critical to the production of postoperative venous infarction.