Background: The aim of this study was to determine the ideal point for a ventricular puncture in pterional craniotomies.
Methods: Using a circle that had its center around the junction of the columns of the fornix and conforming to the surface of the frontal lobe on an axial computed tomography scan 2.5 cm superior to the lateral orbital roof, we simulated the introduction of a catheter perpendicular to the cortex by drawing the radii of the circle in 70 patients with an acute subarachnoid hemorrhage. The cortical point at which perpendicular puncture provides the best trajectory for ventricular access, traversing the least brain tissue and avoiding important brain structures, such as the head of the caudate nucleus, anterior limb of the internal capsule, and Broca's cortex in the dominant hemisphere, was measured.
Results: The new landmark was located at the point 44 +/- 4 mm anterior to the sylvian fissure on the level of 2.5 cm superior to the lateral orbital roof and was consistent regardless of the ventricular dimensions and sex. Clinical trial of the ventriculostomy in 32 patients with a ruptured aneurysm approved the new landmark.
Conclusions: An intraoperative ventriculostomy can be performed safely and reliably using the new landmark 2.5 cm superior to the lateral orbital roof and 4.5 cm anterior to the sylvian fissure in aneurysm surgery using a pterional craniotomy.