Extended approach or usage of nasoseptal flap is a risk factor for olfactory dysfunction after endoscopic anterior skullbase surgery: Results from 928 patients in a single tertiary center

Background: The aim of this study was to compare olfactory function change in patients who underwent endoscopic skull-base surgery. Methodology: A total of 928 patients were included in this retrospective study. Olfactory function was measured using the non-validated Likert scale (0–100), the Cross-Cultural Smell Identification Test (CC-SIT) and the butanol threshold test (BTT). Patients were divided into two groups: an endoscopic trans-sellar approach group (ETA, n = 768) and an extended endoscopic endonasal approach group (EEEA, n = 160). The ETA group was sub-divided into Nasoseptal flap (NSF) and no NSF groups. Results: Non-validated olfactory function significantly worsened in the EEEA and ETA-NSF groups compared with that in the ETA-no NSF group for at least 6 months post-operatively. Validated olfactory impairment (BTT and CC-SIT) was also significantly worse in the EEEA and NSF groups compared with that in the ETA-no NSF group 3 months post-operatively. Additionally, the degrees of non-validated and validated olfactory deterioration were not significantly different between the EEEA and ETA-NSF groups. We also found that CC-SIT score changes were significantly impaired in tuberculum sellae meningioma patients than in craniopharyn-gioma patients. Conclusions: We conclude that NSF was the key factor that led to olfactory impairment after endoscopic skull-base surgery.