Anatomy of the transarcuate approach to the petrous apex

Abstract

Objective: Determine the dimensions of the approach to the petrous apex through the crura of the superior semicircular canal (SSC). Study Design: Measurements obtained from high-resolution computed tomography (HRCT) images. Subjects and Methods: One hundred ninety-two HRCTs were screened and 58 temporal bones with pneumatized posterior petrous apex cell tracts in 39 patients were identified and reviewed. Measurements were obtained with the assistance of the standard PACS (picture archiving and communication system) software. Results: The mean anterior-posterior (AP) dimension of the intercrural space of the SSC was 4.88 ± 0.49 mm. The mean superior-inferior (SI) dimension of this space was 4.90 ± 0.62 mm. When air cells were present in the intercrural space, the dimensions of the approach increased to 5.27 ± 0.50 mm for the AP dimension ( P = 0.014) and 5.27 ± 0.70 mm for the SI dimension ( P = 0.056). Conclusion: The subarcuate approach is a potential route for the drainage of petrous apex cholesterol granulomas with minimal risk to the SSC, as demonstrated on HRCT measurements.