Anatomical and technical correlates in endoscopic anterior skull base surgery: a cadaveric analysis.

OBJECTIVE: The objectives of this study were to 1) evaluate anatomical relationships and 2) develop technical correlates for endoscopic anterior skull base (ASB) surgery.

STUDY DESIGN: Cadaver study.

SETTING: Minimally invasive surgery laboratory.

SUBJECTS AND METHODS: Ten adult fresh-frozen cadaver heads were dissected from December 2006 to December 2007. The endoscopic trans-cribriform, trans-ethmoid approach to the anterior cranial base was refined over these consecutive dissections. Endoscopic orientation along the ventral axis was assessed with 0 degrees , 30 degrees , and 70 degrees rigid telescopes. Anatomical dimensions of the ASB window were measured in the anteroposterior (posterior table of frontal sinus to planum sphenoidale) and transverse (orbit-to-orbit) dimensions at the anterior ethmoid artery (AEA) and posterior ethmoid artery (PEA).

RESULTS: Endoscopic cadaveric dissections confirmed technical feasibility of ASB surgery and greatly enhanced understanding of ASB anatomical concepts. The 30 degrees rigid endoscope provided the most optimal view from the frontal sinus to the planum sphenoidale with the least distortion, relative to 0 degrees and 70 degrees scopes. Careful identification of the AEA and PEA was requisite for proper orientation at the ASB. The posterior one third of the ASB was thickest and always required drilling for resection. The mean boundaries of the ASB window were 33.7 mm (anterior to posterior) and 23.5 and 19.1 mm at the AEA and PEA (orbit to orbit), respectively.

CONCLUSION: This prospective cadaveric study outlined key correlates for endoscopic ASB surgery. It serves to highlight the requisite technical steps and anatomical dimensions when the trans-nasal endoscopic route is employed for ASB pathology.