When is posterolateral orbitotomy useful in a pterional craniotomy? A morphometric study.

Adding posterolateral orbitotomy to pterional craniotomy allows greater exposure of the anterolateral skull base. However, there is a paucity of literature quantifying the relative benefit of adding posterolateral orbitotomy for various surgical targets. Our study is a step to address this issue. We performed dissections of five cadaveric heads (10 sides). The anterior communicating artery (A-Com) complex, posterior chiasm (anterior third ventricular region), ipsilateral optic canal, and ipsilateral supraclinoid internal carotid artery (ICA) bifurcation were chosen as targets. A pterional craniotomy was performed and the targets were morphometrically analyzed. Subsequently, posterolateral orbitotomy was done and analysis repeated. The field of view and measurements quantifying the angle of attack were compared. Addition of orbitotomy to pterional craniotomy increased the angle of exposure to ICA bifurcation, anterior third ventricular region, and A-Com complex by average of 15%, 29%, and 50%, respectively. Our study shows the addition of a posterolateral orbitotomy to the pterional craniotomy improves the angle of attack to the anterior third ventricular region and the A-Com complex, thus supporting the use of orbitopterional craniotomy for suprasellar lesions extending into anteroinferior third ventricle and A-Com aneurysms that point superiorly/posteriorly.