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J Neurol Surg B Skull Base 2012; 73 - A077
DOI: 10.1055/s-0032-1312125

Second Stage in Predicative Measure for Transnasal Transsphenoidal Approach to Petrous Apex Cholesterol Granuloma

Angela M. Donaldson 1(presenter), Nael Shoman 1, Jeffrey Ksiazek 1, Myles L. Pensak 1, Lee A. Zimmer 1
  • 1Cincinnati, USA

Objective: This study is the second stage in a three-stage study, which aimed to identify the narrowest petrous angle that would allow a transsphenoidal approach for treatment of cholesterol granulomas based on our operative experience.

Study Design: Retrospective review.

Setting: University of Cincinnati Medical Center.

Subjects and Methods: Patients in the study were seen in our tertiary care center from 2000–2010 with isolated petrous cholesterol granulomas on noncontrast orbital/sella/internal auditory canal CT images of the temporal bone. The angle between the medial-most aspect of the vertical portion of petrous internal carotid artery (ICA), vomer, and occipital protuberance was measured. The distance between the posterior sphenoid wall (SW) and the medial aspect of the cholesterol granuloma (CG) was measured.

Results: Seventeen patients had radiographically evident isolated petrous CGs, and 17/18 or 94% of the CGs abutted the posterior sphenoid wall (SW), as defined by a sphenoid wall to medial aspect of CG distance of 5 mm or less. In our study, a petrous angle of 10 degrees with SW to CG distance of 7 mm was the narrowest angle for which the transsphenoidal approach was successful.

Conclusion: The first study in our three-stage study looked at 400 normal CT scans of the temporal bone and found that the majority of patients had a petrous angle—the angle between the medial aspect of the petrous ICA, the vomer, and the occipital protuberance—between 10 and 20 degrees. This was the second study that looked at a quantitative predictive measure of feasibility of the transsphenoidal approach using three consistent landmarks. We found that the majority of petrous apex CGs in our practice had an angle between 10 and 20 degrees. We determined that a petrous angle of 10 degrees and a SW to CG of less than 10 mm is a reasonable cutoff for performing incision and drainage of petrous apex CGs in the hands of an experienced surgeon.