Association Between Limited Airflow in Olfactory Cleft and Impaired Olfactory Function: A Systematic Review

Objective: This systematic review aims to evaluate and summarize the available literature on the relationship between olfactory cleft (OC) airflow and olfactory function in both healthy individuals and those with olfactory dysfunction. Methods: A systematic search was conducted in PubMed, Google Scholar, OVID, and Cochrane databases to identify studies on OC airflow and olfactory function. Studies were selected based on predefined inclusion criteria. Results: 12 studies were included. The average OC airflow rate and velocity of healthy people were strongly correlated with olfactory threshold (OT) and olfactory discrimination (OD), but weakly with olfactory identification (OI). The anatomical localization of nasal polyps (NP) significantly influenced nasal airflow patterns, with lesions situated in the pre-olfactory region or occupying the entire OC demonstrating complete obstruction of OC airflow and consequent impairment of olfactory recognition thresholds. In contrast, NP localized to the superior or middle meatus exerted minimal clinical impact on airflow parameters. Quantitative analysis revealed an inverse correlation between polyp volume and both OI scores and peak nasal inspiratory flow measurements. In patients with nasal septum deviation, the OT and OI scores were significantly lower on the affected side, though these parameters demonstrated improvement following septoplasty. Combined septoplasty with partial inferior turbinectomy improved the nasal airflow and olfaction, particularly the OD and OI scores. Patients with hypertrophic inferior turbinate due to chronic rhinitis had higher nasal resistance and lower OT, OD, and OI scores compared to healthy controls. There was a significant recovery in resistance, OT, OD, and OI scores postoperatively. Middle turbinate resection demonstrated efficacy in augmenting the olfactory flux and nasal airflow. Notably, superior turbinate lateralization in chronic rhinosinusitis with NP increased the cross-sectional area of OC and improved odor identification function. Conclusion: Impaired OC airflow was highly associated with olfactory dysfunction. Precise mapping through computational fluid dynamics of the airflow-olfaction axis not only enhances diagnostic accuracy but also informs targeted surgical interventions.