Comparison of Olfactory Cleft Width and Volumes in Patients with COVID-19 Anosmia and COVID-19 Cases Without Anosmia

Abstract

Introduction: The aim of this study was to assess the relationship between olfactory cleft width/volume and COVID-19-related anosmia.

Methods: This study consisted of PCR-proven COVID-19 patients. Cases with COVID-19-related anosmia constituted Group 1 and cases without any olfactory dysfunction (OD) throughout COVID-19 infection or after recovery constituted Group 2. A total of 50 patients were included in the study, comprising 24 cases in Group 1 and 26 cases in Group 2. Group 1 patients underwent a 4-item-odor identification test during active symptoms and a Sniffin' Sticks test after reconversion of PCR results to negative. All patients in Group 2 also underwent the Sniffin' Stick test to document normosmia. All cases had paranasal sinus CT performed. Olfactory cleft widths and olfactory volumes were measured. The differences in width and volume between groups and the correlation with odor test scores (threshold-discrimination-identification [TDI]) were calculated. In addition, regression analyzes analysis was performed for cleft widths, volumes, and TDI scores according to age.

Results: Olfactory cleft widths and olfactory volumes were significantly higher in Group 1 than those in Group 2 (p = 0.001; p < 0.01). There was a significant negative correlation between total TDI scores and olfactory cleft widths and total olfactory volumes (r = -0.665; r = -0.731, respectively). Patients younger than 40 years of age had significantly higher right olfactory cleft width, left olfactory cleft width, and olfactory cleft volume than those in patients older than 40 years of age (p = 0.004, p = 0.005, p = 0.003; p < 0,01, respectively). However, patients younger than 40 years of age had a significantly lower total TDI score and in all other values individually (t-d-i) than those in patients older than 40 years of age (p = 0.004; p < 0.01).

Conclusion: Patients with COVID-19-related OD had larger olfactory cleft width and volumes than those without OD in this study. Total TDI score was found to be inversely correlated with cleft width and volume.

Keywords: Age; Anosmia; COVID-19; Olfactory cleft; Olfactory cleft volume; Olfactory cleft width; Paranasal computed tomography; Threshold-discrimination-identification.

Conflict of interest statement

The authors declare that there is no conflict of interest.

© 2021 S. Karger AG, Basel.

Figures

Fig. 1

Cleft measurements were calculated at the junction of anterior 1/3 and posterior 2/3 because of more stable anatomy with preserved aeration and symmetric bilateral clefts at this point. More anterior or posterior slices had alterations in the anatomy and asymmetry (partial cleft opacification, medialization/lateralization of laminae). This may not have importance in daily clinical practice; however, measurement of a small region like the olfactory cleft required a standard methodology. a In order to measure the olfactory cleft width, a line (line A) parallel to the cribriform plate is defined along the olfactory cleft borders on paranasal sinus CT images in sagittal reconstruction. The intersection of anterior 1/3 and posterior 2/3 of this line is marked (point A). b Coronal oblique reformats are created perpendicular to line A, and olfactory cleft widths are measured at the intersection of anterior 1/3 and posterior 2/3 of this line (point A) and 10 mm inferior to the cribriform plate. During olfactory cleft width measurement, air and mucosa are included, whereas bone and cartilaginous structures are excluded. c In the coronal plan image (same as b) created in the soft tissue window, a sample of olfactory cleft volume measurement (marked as blue highlighted region) is shown by drawing the contours of the osseous cortex (including the cleft mucosa) taking into account a 1 cm depth of the cribriform plate. Bone (thick arrow) and cartilaginous structures (arrow at nasal septum) are not included in the total volume.

Fig. 2

a Measurement of right and left olfactory cleft volumes on coronal plane. During segmentation, structures with air and soft tissue density are included. b Measurement of right and left olfactory cleft volumes on axial plane, depicting the anterior and posterior margins of olfactory cleft. c 3D volumetric images illustrate right and left olfactory cleft volume measurements and mean density of volume of interest.

Fig. 3

The relation between right/left olfactory cleft widths and TDI. TDI, threshold-discrimination-identification.

Fig. 4

There is a significant negative relation between olfactory cleft volume and TDI in the whole study group. TDI, threshold-discrimination-identification.

Fig. 5

Flowchart summarizing odor tests and radiological findings of patients.