Anterior Inferior Petrosectomy: Defining the Role of Endonasal Endoscopic Techniques for Petrous Apex Approaches

Objective: Historically, surgery to the petrous apex has been addressed via craniotomy and open microscopic anterior petrosectomy (OAP). However, with the popularization of endoscopic approaches, the petrous apex can further be approached endonasally by way of an endoscopic endonasal anterior petrosectomy (EAP). EAP is a relatively new approach, and has not been compared anatomically to OAP. We hypothesized that EAP and OAP approach different portions of the petrous apex, and therefore may have different applications.

Methods: 4 cadaver heads were utilized. OAP was performed on one side and EAP was performed on the contralateral side; the limits of bony resection were defined. The extent of boney resection was then evaluated by pre-disection and post-dissection thin slice CT scans. The comparative resection was then reconstructed with 3D modeling on Brainlab© workstations. We further provide a case example of a chondrosarcoma, in which a combination of the two approaches was required to achieve a complete radiographic resection, demonstrating the clinical utility both approaches.

Results: Average Resection volumes for EAP and OAP were 0.297 cm3 and 0.649 cm3 respectively, representing a comparative percentage of 46% (EAP/OAP). EAP and OAP achieved resection of 29% and 64% of the total petrous apex volume respectively. Indeed, EAP more completely addressed the inferior portion of the petrous apex, adjacent to the petroclival suture than OAP, where 45% of the bone overlying the petroclival suture (petroclival angle to the jugular foramen) was resected with EAP, while 0% was resected with OAP.

Conclusions: In anatomically normal cadavers, OAP achieved nearly a 50% larger volumetric resection than EAP. Further, while OAP appears to completely address the superior portion of the petrous apex, EAP appears to have a niche in approaches to lesions in the inferior petrous apex as detailed in our case example. Given these results, we propose that OAP be redefined as the superior anterior petrosectomy, and EAP be referred to as the inferior anterior petrosectomy, which more clearly defines the role of each approach in anterior petrosectomy.