Petrous apex cholesterol granulomas: Endonasal versus infracochlear approach

Objectives/Hypothesis: The aim of this study was to investigate and compare the surgical anatomy of two different routes to access and drain petrous apex (PA) cholesterol granulomas: the expanded endonasal approach (EEA) and the transcanal infracochlear approach (TICA). Study Design: Anatomic and radiologic study. Methods: The EEA and TICA to the PA were performed in 11 anatomic specimens with the assistance of imaging guidance. The PA was categorized into three zones: superior PA, anterior-inferior PA, and posterior-inferior PA. The maximum drainage window achieved by each approach was calculated using the imaging studies of each anatomic specimen. Results: The EEA was able to reach superior PA and anterior-inferior PA in all specimens and posterior-inferior PA in 90%. The TICA did not provide access to superior PA in any case. The TICA was suitable to reach anterior-inferior PA in 80% of specimens and posterior-inferior PA in 60%. Based on the radiologic study, the EEA provided a drainage window three times larger than the TICA. Conclusions: The transnasal approach provides reliable access to the PA when combined with internal carotid artery exposure and allows for large drainage window. The transcanal approach is less versatile and more limited than the transnasal approach but provides access to the most posterior and inferior portion of the PA without Eustachian tube transection. Here we propose a new surgical classification that may help to decide the most suitable approach to the PA according to the location and extension of the lesion.