Olfactory Function Outcomes Following Endoscopic Endonasal Transsphenoid Approach for Skull Base Surgery: A Systematic Review and Meta Analysis

Background: Endoscopic endonasal transsphenoid (EETS) approach has become a mainstay surgical technique for sellar and parasellar tumors. Although the approach necessitates significant manipulation of the olfactory system, including risk to the olfactory epithelium, the extent of its impact on olfactory function is incompletely defined. Methods: A systematic search was performed on PubMed. Studies that assessed olfactory outcomes following endoscopic endonasal transsphenoid surgery were inquired. Cohort studies that utilized standardized olfactory function assessment tools were included for a qualitative summary. Studies with pre- and postoperative cohort level summary data for the most prevalent assessment tools were included in a random-effects meta-analysis of mean differences in pre- and postoperative olfactory function. Results were summarized as pooled mean differences (MD). Results: 41 studies encompassing a total of 2501 patients were identified for qualitative review. The most common lesions were pituitary adenomas, craniopharyngiomas, sellar meningiomas, and Rathke’s cleft cysts. The most commonly utilized olfactory assessment tools included the University of Pennsylvania Smell Identification Test (UPSIT) and Sniffin’ Sticks (10 studies each), followed by the Connecticut Chemosensory Clinical Research Center (CCCRC) test (5 studies), and lastly the Cross-Cultural Smell Identification Test (CC-SIT), T&T olfactometer, and Smell Diskettes Olfaction Test (3 studies each). The average follow-up time after surgery was 4.3 months. Eight studies using the UPSIT test were eligible for meta-analysis, and pooled mean differences between pre-op and post-op cohorts were calculated. There was no statistically significant difference between pre- and postoperative olfaction as measured by UPSIT, both for patients with a 3 month or less follow-up as well as for patients with a 6 month or longer follow-up time. Conclusion: Overall, the EETS approach is not associated with a consistent decline in olfactory function as shown by a lack of significant change when comparing pre-op and post-op UPSIT results. Future studies may clarify these findings by stratifying outcomes by surgical technique, such as the use of septal flaps, tumor location, and pathology. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany