Petrous Apex Pneumatization

Objective: Endoscopic nasal surgery is expanding to include complex approaches to the skull base, including the petrous apex and pre-pontine space. Possible approaches to this region depend largely on individual anatomy, which in the sphenoid sinus is highly variable due to pneumatization patterns. Similarly, the pneumatization of the petrous apex is the subject of attempts to characterize those patients with anatomy that would permit an endoscopic transnasal approach, for example, to cholesterol granulomas. In this study, we explore skull base anatomy in a random population to characterize the pneumatization of the sphenoid and its relation to that of the petrous apex. We postulate that a pneumatized lateral recess of the sphenoid in conjunction with a well pneumatized petrous apex provides an optimal path for an anterior or transnasal trans-osseous pathway to the petrous apex and pre-pontine space. We therefore present an analysis regarding the pneumatization of this anatomical region, and whether a developmental process of petro-sphenoid co-pneumatization can be inferred.

Study Design: Retrospective chart review.

Methods: Over 450 maxillofacial CT scans obtained for trauma purposes were reviewed. The sphenoid sinus was examined for presence or absence of a pneumatized lateral recess. Likewise, the degree of pneumatization of the petrous apex was determined. The results were then analyzed to determine the most commonly encountered patterns of pneumatization, as well as the correlation between pneumatization of the sphenoid sinus and the petrous apex.

Results: Degree of pneumatization closely correlates between the left and right sides of individual patients. The most frequently encountered pattern was that of both non-pneumatized petrous apex and non-pneumatized lateral recess of the sphenoid sinus. There was a statistically significant correlation between a pneumatized sphenoid lateral recess and well pneumatized petrous apex (co-pneumatization), although this represented only 5% of the study population.

Conclusion: This anatomic study demonstrates that there is a subset of patients with a particularly favorable pneumatization pattern of the skull base that would facilitate endoscopic transnasal access to the petrous apex. Preoperative imaging and utilization of a standard grading system can identify those patients who may have lesions amenable to a transnasal approach, thus offering endoscopic alternatives to lateral or open approaches to this region.