Abstract
We performed clipping surgeries for patients with unruptured middle cerebral artery (MCA) bifurcation aneurysms and used preoperative magnetic resonance (MR) imaging (T2-weighted image; T2WI) and MR angiography (MRA), intraoperative findings, and postoperative computed tomographic scans to investigate 1) whether the subfrontal approach (SFA) with frontal lobe retraction or the transsylvian approach (TSA) can secure a minimum surgical field by less invasive procedures and 2) which site in the Sylvian fissure (SyF) is it the most effective for entering via TSA. TSA is classified into 1) the transproximal Sylvian approach (proximal TSA) by opening the proximal SyF, 2) transmiddle Sylvian approach (middle TSA) by opening the middle SyF, and 3) transdistal Sylvian approach (distal TSA) by opening the distal SyF. Determinants of selecting each approach are not only the length of the horizontal portion of the MCA (M1) and size and location of aneurysms in the deep SyF, but also the width of the anterior operculoinsular compartment (A-OpIC) of the SyF exposed by resection of the sphenoidal ridge and deep sphenoidal compartment (SphC) of the SyF. In conclusion, 1) the SFA is speculated to be appropriate for cases wherein M1 is hidden by aneurysms deeply located inside the narrow SphC; 2) the proximal TSA, for cases wherein M1 and aneurysms are located at the border of the wide SphC and A-OpIC; 3) the middle TSA, for cases wherein M1 and aneurysms are located at the lateral part of the wide A-OpIC; and 4) the distal TSA, for cases wherein long M2 and aneurysms are located in the OpIC.
