The Retrolabyrinthine Presigmoid Approach to the Anterior Cerebellopontine Region: Expanding the Limits of Trautmann Triangle.

Abstract

The anatomic area exposed through exposure of Trautmann triangle may not be sufficient. We studied the additional exposure provided by skeletonizing the sigmoid sinus (SS). In 5 human cadaveric heads, thin-cut computed tomography images of 2 sides of the temporal bone were obtained for a total of 10 sides. The estimated surgical working angle was calculated based on the relationship of the SS to the posterior semicircular canal (PSC), superior petrosal sinus, and jugular bulb on imaging. Mastoidectomy was performed, and heads with and without SS skeletonization were remeasured. Working angle calculated on computed tomography was 56° ± 11.3. Skeletonization of the SS increased the distance between the PSC and SS by 5 mm (P= 0.01) and between the lateral semicircular canal and SS by 4 mm (P= 0.01). Skeletonization and retraction of the SS significantly increased the distance between the PSC and lateral semicircular canal to the SS. On images obtained after mastoidectomy, skeletonizing the SS helped improve anterior visibility on most samples that had an SS that was lateral to the PSC on axial imaging. In samples in which the SS was medial to the PSC or had only minimal lateral displacement, skeletonizing the SS did not markedly improve visibility of the retrolabyrinthine space. Working area and visibility improved as the PSC and SS approached the same plane on axial imaging. Preoperative evaluation of the laterality of the SS to the PSC may assist a surgeon in determining the need for skeletonizing the SS and avoiding possible vascular injuries.