Background Post-COVID-19 olfactory dysfunction (PCOD) is a common sequela of SARS-CoV-2 infection, with some cases persisting beyond the acute phase. While prolonged PCOD has been considered primarily sensorineural, recent studies suggest that olfactory cleft (OC) obstruction may contribute to olfactory dysfunction (OD). This study aimed to investigate OC obstruction in prolonged PCOD compared to post-infectious olfactory dysfunction (PIOD) and assess its impact on olfactory function.

Methodology/Principal We retrospectively analysed sinus computed tomography scans of patients with prolonged PCOD and PIOD. OC obstruction was classified into absent (0%), mild (1–90%), and severe (>90%) types. The severity of OC obstruction was compared between PCOD and PIOD cases, and olfactory test results were analysed according to OC obstruction severity.

Results A total of 87 PCOD patients and 67 PIOD patients were included. Mild and severe OC obstruction was more prevalent and severe in prolonged PCOD (mild: 35.6%, severe: 18.4%) than PIOD (mild: 13.4%, severe: 3%). Moreover, worsened olfactory function was found in PCOD patients with severe OC obstruction. In contrast, OC obstruction showed little association with olfactory function in PIOD patients.

Conclusions Mild and Severe OC obstruction appear to be more common in prolonged PCOD. Moreover, severe OC obstruction may further impair olfactory function in PCOD patients. Conversely, severe OD in PIOD patients occurred independently of OC obstruction.

The authors have declared no competing interest.

This study did not receive any funding

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

This study was approved by the ethics committee of Jikei University School of Medicine (Approval No. 33-159[10774]).

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All data produced in the present study are available upon reasonable request to the authors