• Thomas A Ostergard, Chad A Glenn, Simone E Dekker, Jonathan R Pace, and Nicholas C Bambakidis.
• Department of Neurosurgery, University Hospitals Cleveland Medical Center, Case Western Reserve University, Cleveland, Ohio, USA. Electronic address: Thomas.ostergard@uhhospitals.org.
• World Neurosurg. 2018 Nov 1; 119: 176-182.

ObjectiveThe transtentorial extension of the retrosigmoid approach allows for improved visualization of the brainstem and petroclival region. This approach is an important tool in the skull base surgeon's armamentarium for pathologies involving the petroclival region. It has been shown that the addition of tentorial transection improves the exposed surface area of the brainstem. However, no data have been reported regarding the depth of the additional anterior and medial exposure. The goal of the present study was to describe the additional depth of exposure gained by performing tentorial transection. This information allows surgeons to preoperatively estimate the amount of operative exposure gained by this technique.MethodsFive preserved cadaveric heads were dissected using frameless image guidance. A standard retrosigmoid craniotomy was performed, followed by tentorial transection. The boundaries of the surgical exposure and depth of the surgical field were compared before and after tentorial transection.ResultsAfter transection, we found a 20.1-mm increase in anterior exposure (P < 0.01) and a 13-mm increase in medial exposure (P < 0.01). No significant difference was found in the extent of the superior (P = 0.32) or lateral (P = 0.07) exposure. The surgical working distance increased significantly from 68.8 to 90.3 mm (P < 0.01).ConclusionsWhen performing retrosigmoid craniotomy, the addition of tentorial transection allows for a significant increase in anterior and medial exposure with no significant increase in superior or lateral exposure.Copyright © 2018 Elsevier Inc. All rights reserved.

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