Olfactory Cleft Length: A Possible Risk Factor for Persistent Post-COVID-19 Olfactory Dysfunction

Abstract

Introduction: To date, little is known about predisposing factors for persistent COVID-19-induced olfactory dysfunction (pCIOD). The objective was to determine whether olfactory cleft (OC) measurements associate with pCIOD risk.

Material and methods: Three subgroups were recruited: group A included patients with pCIOD, group B included patients without olfactory dysfunction following SARS-CoV-2 infection (ntCIOD), and group C consisted in controls without past history of SARS-CoV-2 infection (noCOVID-19). Olfactory perception threshold (OPT) and visual analog scale for olfactory impairment (VAS-olf) were obtained. OC measurements were obtained through computed tomography scans. Results were subsequently compared.

Results: A total of 55 patients with a mean age of 39 ± 10 years were included. OPT was significantly lower in pCIOD patients (group A: 4.2 ± 2.1 vs. group B: 12.3 ± 1.8 and group C: 12.2 ± 1.5, p < 0.001). VAS-olf was significantly higher in pCIOD (group A: 6 ± 2.6 vs. group B: 1.7 ± 1.6 and group C: 1.6 ± 1.5, p < 0.001). OC length was significantly higher in group A (42.8 ± 4.6) compared to group B (39.7 ± 3.4, p = 0.047) and C (39.8 ± 4, p = 0.037). The odd of pCIOD occurring after COVID-19 infection increased by 21% (95% CI [0.981, 1.495]) for a one unit (mm) increase in OC length. The odd of pCIOD occurring was 6.9 times higher when OC length >40 mm.

Conclusion: Longer OC may be a predisposing factor for pCIOD. This study is expected to encourage further research on OC morphology and its impact on olfactory disorders.

Keywords: COVID-19; Hyposmia; Length; Olfactory cleft; Olfactory dysfunction.

Conflict of interest statement

The authors have no conflicts of interest to declare.

© 2022 S. Karger AG, Basel.

Figures

Fig. 1

CT evaluation of the olfactory cleft: initial orientation of the axial slices parallel to the cribriform plate in the sagittal plane.

Fig. 2

Measurement of the anteroposterior length of the olfactory cleft in the axial plane parallel oriented to the cribriform plate, between the anterior insertion of the middle turbinate and the anterior wall of the sphenoid sinus.

Fig. 3

Measurement of the olfactory cleft width bilaterally, in the coronal plane, at the intersection between the anterior and posterior two-thirds of the olfactory cleft, 5 mm inferior to the cribriform plate.

Fig. 4

Mean olfactory cleft (OC) length across subgroups. Note: Results from ANOVA model.

Fig. 5

Mean olfactory cleft (OC) area across subgroups. Note: Results from ANOVA model.

Fig. 6

Flowchart of the main findings.