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Preoperative Disease Severity at Sites of Subsequent Skull Base Defects after Endoscopic Sinus Surgery

Background Skull base (SB) injury is a known complication of endoscopic sinus surgery (ESS). Risk factors for SB injury include poor visualization, low-lying SB, and SB asymmetry. Anecdotal evidence indicates that many SB defects occur in areas with minimal mucosal disease adjacent to the SB. We evaluated preoperative computed tomography (CT) scans to determine the degree of mucosal disease present at the site of subsequent SB defects caused by ESS. Methods Retrospective review of patients with SB injury as a result of ESS. Preoperative and postoperative CT films were reviewed for extent of overall sinus disease and disease at the site of the subsequent SB defect and presence of risk factors for SB injury. Results Preoperative and postoperative CT scans were obtained for 22 patients with 23 defects, who underwent 21 primary and 1 revision ESS. Fifteen (65%) patients had no disease, 2 (9%) patients had minimal disease, and 6 (26%) patients had complete opacification at the site of subsequent SB injury. SB defects occurred in the ethmoid roof (15 patients, 65%), lateral lamella (5 patients, 22%), cribriform plate (2 patients, 9%), and sphenoid sinus (1 patient, 4%). Risk factors for SB injury were only identified in 6 patients. Conclusion SB injuries resulting from ESS occurred in SB regions with minimal or no mucosal disease in over two-thirds of cases. Explanations for this may include thinner bone and mucosa in areas without chronic disease that is easier to injure and less resistance to dissection in minimally diseased areas. Caution should always be exercised in ESS, but especially in minimally diseased areas.