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Multicenter Study
. 2022 Jun;49(4):329-332.
doi: 10.1016/j.neurad.2022.03.003. Epub 2022 Mar 17.

Transient modifications of the olfactory bulb on MR follow-up of COVID-19 patients with related olfactory dysfunction

Amine Ammar  1 , Lea Distinguin  2 , Anaelle Chetrit  3 , Dominique Safa  3 , Stephane Hans  2 , Robert Carlier  3 , Jerome R Lechien  4 , Myriam Edjlali  5
Affiliations
Multicenter Study

Transient modifications of the olfactory bulb on MR follow-up of COVID-19 patients with related olfactory dysfunction

Amine Ammar et al. J Neuroradiol. 2022 Jun.

Abstract

Background: Olfactory dysfunction (OD) has been reported with a high prevalence on mild to moderate COVID-19 patients. Previous reports suggest that volume and signal intensity of olfactory bulbs (OB) have been reported as abnormal on acute phase of COVID-19 anosmia, but a prospective MRI and clinical follow-up study of COVID-19 patients presenting with OD was missing, aiming at understanding the modification of OB during patients'follow-up.

Methods: A prospective multicenter study was conducted including 11 COVID-19 patients with OD. Patients underwent MRI and psychophysical olfactory assessments at baseline and 6-month post-COVID-19. T2 FLAIR-Signal intensity ratio (SIR) was measured between the average signal of the OB and the average signal of white matter. OB volumes and obstruction of olfactory clefts (OC) were evaluated at both evaluation times.

Results: The psychophysical evaluations demonstrated a 6-month recovery in 10/11 patients (90.9%). The mean values of OB-SIR significantly decreased from baseline (1.66±0.24) to 6-month follow-up (1.35±0.27), reporting a mean variation of -17.82±15.20 % (p<0.001). The mean values of OB volumes significantly decreased from baseline (49.22±10.46 mm3) to 6-month follow-up (43.70±9.88 mm3), (p=0.006).

Conclusion: Patients with demonstrated anosmia reported abnormalities in OB imaging that may be objectively evaluated with the measurement of SIR and OB volumes. SIR and OB volumes significantly normalized when patient recovered smell. This supports the underlying mechanism of a transient inflammation of the OB as a cause of Olfactory Dysfunction in COVID-19 patients.

Keywords: Anosmia; COVID-19; Magnetic resonance imaging; Olfaction disorders; SARS-CoV-2.

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Conflict of interest statement

Declarations of Competing Interest None.

Figures

Image, graphical abstract
Graphical abstract
Fig 1:
Fig. 1
Signal intensity ratio (SIR) measurement Coronal Flair-weighted at the same level slices through the olfactory bulbs (OB) in a 32-year-old anosmic female at the initial exam (A) and at the follow-up exam (B), performed respectively at day 4 and 147 from onset of anosmia. The SIR between the average signal of the OB (manual ROI) and the average signal of a ROI placed in the frontal same level white-matter (circle) went from 1.63 to 1.05 on the right and from 1.68 to 0.96 on the left (fall of 35.26% and 42.45% respectively). There was a partial obstruction of right olfactory cleft (dotted arrow) which regressed on control. Note the isointense signal OB (arrows) compared to normal brain cortex (head of arrows).
Fig 2:
Fig. 2
Measurement of the olfactory bulbs (OB) volumes Same level reformatted axial, frontal and sagittal 3D-T2-wheighted slices through the olfactory bulbs (OB) in a 26-year-old anosmic female at the initial exam (A, B, C) and at the follow-up exam (D, E, F), performed respectively at 7 and 147 days from onset of anosmia. OB volumes varied from 54.91 to 41.80 mm3 on the right and from 57.73 to 42.7 mm3 on the left (decrease of 41.0% and 37.85% respectively).
See this image and copyright information in PMC

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