Olfactory function after nasoseptal flap reconstruction in skull base surgery: a systematic review and meta-analysis.

Abstract

Endoscopic skull base surgery is widely used for various skull base pathologies. The nasoseptal flap (NSF) is considered the gold-standard reconstructive technique to reduce postoperative cerebrospinal fluid (CSF) leaks. However, its impact on olfactory function remains unclear. To systematically compare olfactory outcomes between NSF and no-NSF reconstruction following skull base surgery. PubMed, Embase, and Cochrane databases were searched for randomized controlled trials and observational studies comparing olfactory function in patients undergoing skull base surgery with NSF versus no-NSF reconstruction. Outcomes included: (1) number of patients with any degree of postoperative decline in olfaction at ≥ 6 months, (2) mean olfactory scores at 3 months, and (3) mean olfactory scores at ≥ 6 months. Heterogeneity was assessed using I² statistics. Seven studies (n = 1,289) were included; 392 patients (30.4%) underwent NSF reconstruction. NSF was associated with a greater number of patients who experienced postoperative olfactory decline compared to no-NSF (RR 1.77; 95% CI 1.20-2.62; p = 0.004). At 3 months, NSF patients had worse olfactory scores (SMD - 0.32; 95% CI - 0.60 to - 0.05; p = 0.02). However, no significant difference in olfactory scores was observed at ≥ 6 months (SMD - 0.43; 95% CI - 1.63 to 0.77; p = 0.33). NSF reconstruction is associated with worse short-term olfactory test scores and a higher proportion of patients with olfactory decline at ≥ 6 months. However, the severity of dysfunction at longer-term follow-up is comparable between groups, suggesting delayed but eventual olfactory recovery.