Quantitative analysis of endoscopic endonasal approaches to the infratemporal fossa

Objectives/Hypothesis: The operative management of infratemporal skull base lesions is challenging. Expanded endonasal approaches to this area can decrease surgical morbidity. Access lateral to the natural nasal corridor can be achieved via a middle meatal antrostomy, medial maxillectomy complemented by a septotomy, or anteromedial maxillotomy (i.e., Denker's approach). We sought to compare the access to the infratemporal fossa offered by these endoscopic endonasal approaches. Study Design: Software-enabled CT scan measurements. Methods: Axial CT scans obtained with submillimeter cuts through the skull base were examined. All calculations were performed on axial images obtained at the level of the sphenoid floor using Kodak Carestream Image Software (Rochester, NY) measuring tools. Results: Fifty sides were examined. A medial maxillectomy increased the exposure on average by 18.5 degrees (SD = 4.28), when compared to maxillary antrostomy. When we augmented the access with an ipsilateral Denker's approach, an additional 33.5 degrees (SD = 4.81) of exposure were obtained (P <.0001). The addition of a 1-cm anteromedial maxillotomy accessed the entire posterior maxillary wall in 54% of cases. Equivalent access was obtained via a contralateral approach with a septotomy at 1.56 cm from the columella. To access the entire posterior maxillary wall the average anterior maxillotomy should be 1.1 cm (SD = 0.42). In contrast, to access the entire posterior maxillary wall using a contralateral approach the average septotomy position should be 1.52 cm (SD = 0.39) from the columella. Conclusions: This radioanatomic study provides objective support for the use of an ipsilateral Denker's approach to augment an endoscopic endonasal approach to the infratemporal fossa.