Terpene-Centered Olfactory Training in Postinfectious Olfactory Dysfunction: A Dual-Route Approach

Abstract

ABSTRACT Objective: To compare the efficacy of classical olfactory training (COT) protocols with a novel dual-route method targeting both orthonasal and retronasal pathways in the management of postinfectious olfactory dysfunction (PIOD), and to explore the neurotherapeutic potential of terpene-based odorants. Methods: One hundred and seventeen patients diagnosed with PIOD received either conventional olfactory training or a modi- fied protocol that integrates retronasal stimulation. The terpene profile of administered odorants was evaluated for its contribu- tion to olfactory and cognitive outcomes. Results: This study had five major findings: (1) The Terpene-Centered Orthonasal and Retronasal Olfactory Training (TCOT) group showed significantly greater improvements in Sniffin' Sticks TDI and odor identification scores at the 9th and 12th months compared to the COT and Modified Olfactory Training (MOT) groups (p<0.001); (2) Retronasal olfactory scores improved sig- nificantly more in the TCOT group at the 9th and 12th months (p<0.001); (3) Clinically meaningful improvement (≥6-point TDI gain) was most frequent in TCOT participants at all time points beyond 6months; (4) TCOT participants exhibited the greatest re- ductions in parosmia severity at 6, 9, and 12months (p<0.05); (5) Cognitive complaints, as measured by CFQ-5 scores, improved most markedly in the TCOT group, with significant differences at the 6th (p<0.001) and 12th (p=0.02) months. Conclusion: Incorporating retronasal training and terpene-rich odorants in olfactory rehabilitation may improve outcomes in PIOD. These findings support the integration of terpene-centered, multimodal olfactory training into clinical rehabilitation strategies for PIOD. Level of Evidence: Level 2