The Associations Between Olfactory Bulb Morphology, Volume Change, and Olfactory Recovery
Zetian Li, Julia Gebler, Shubin Li, Kwangsu Kim, Akshita Joshi, Xinni Xu, Antje Haehner, Vittoria Avaro, Federico Calegari, Thomas HummelAbstract
Objective
To investigate whether olfactory bulb (OB) morphology is associated with olfactory recovery following olfactory training (OT) in individuals with COVID‐19‐related smell loss.
Study Design
Prospective observational study.
Setting
University hospital and research center.
Methods
Twenty women with COVID‐19‐associated olfactory dysfunction and 19 healthy controls underwent OT for 3 months. OB shape (oval vs non‐oval) was classified using high‐resolution magnetic resonance imaging (MRI), and bilateral OB volumes were manually segmented before and after OT. Olfactory performance was assessed with the Sniffin' Sticks test. Statistical analyses included independent t tests, multimodal analysis of covariance, correlation analyses, and generalized estimating equations.
Results
At baseline, OB volume correlated significantly with olfactory performance. Changes in left OB volume were positively correlated with changes in odor threshold. Following OT, patients with non‐oval OB shapes showed greater improvement in Threshold + Discrimination + Identification (TDI) scores and enlargement of left OB volume compared to those with oval‐shaped OB. However, OB morphology did not significantly change over time in both patients and controls.
Conclusion
OB shape may provide a novel perspective for predicting prognosis after OT. Further studies with larger cohorts and extended training durations are warranted to validate these preliminary observations.