Introduction: The anatomical area exposed through the exposure of Trautmann’s triangle may not be sufficient. We studied the additional exposure provided by skeletonizing the sigmoid sinus.

Methods: Human cadaver heads were subjected to a thin temporal bone CT scan for a total of 10 sides. The estimated surgical working angle was calculated based on the relationship of the sigmoid sinus to the posterior semicircular canal, superior petrosal sinus and jugular bulb on imaging. The heads were then subjected to a mastoidectomy and remeasured with and without sigmoid sinus skeletonization.

Results: The working angle calculated on CT was 56 ± 11.3 degrees. Skeletonization of the sigmoid sinus increased the distance between the PSC to SS by 5 mm (p = 0.01), and LSC to SS by 4 mm (p = 0.01). Skeletonization and retraction of the SS significantly increased the distance between the PSC and LSC to the SS. On post mastoidectomy images, skeletonizing the sigmoid sinus helped improve anterior visibility on the majority of our samples that had a SS that was lateral to the PSC on axial imaging. In samples in which the SS is medial to the PSC or only has minimal lateral displacement, skeletonizing the SS did not markedly improve visibility of the retrolabyrinthine space.

Conclusions: Working area and visibility improve as the PSC and SS approach 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.

Patient Care: A subset of patients can undergo surgery to the CP angle without the need for sigmoid sinus skeletonization. This has the potential to reduce vascular injuries.

Learning Objectives: 1. In temporal bones in which the sigmoid sinus is medial to the posterior semicircular canal or only has minimal lateral displacement, skeletonizing the sigmoid sinus does not significantly improve visibility of the retrolabyrinthine space. 2. Working area and visibility improve as the posterior semicircular canal and the sigmoid sinus approach the same plane on axial imaging. 3. A subset of temporal bones that can be easily identified through imaging may not need to undergo skeletonization of the sigmoid sinus in order to gain access to the cerebellopontine angle.

References: see manuscript