Olfactory Bulb Volume for Prognosis in Olfactory Loss

ObjectiveThe olfactory bulb (OB) is essential for olfactory perception, and its volume is correlated to the olfactory function in normal and pathologic cases. We hypothesized that olfactory bulb volume could also be used as a new predictor of olfactory recovery.MethodA cohort of 60 patients suffering from PI (n = 28) and PT olfactory loss (n = 32) was studied. Assessment of olfactory function was performed using orthonasal and retronasal tests, at the time of the diagnosis and 15 months later. All patients were examined on a 3T‐MRI. The olfactory bulb volume was calculated.ResultsRecovery rate was 25% in patients with PT olfactory loss and 35.7% in patients with PI olfactory loss. There was a correlation between both the orthonasal and the retronasal score, and between olfactory testing and the total olfactory bulb volume, both at T1 and at T2. In addition, we observed a significant correlation between changes in olfactory functions and initial measures of the total OB volume, with larger volumes relating to higher improvement on olfactory. Finally, we found that none of the patients with a total OB volume of 40 mm or less exhibited recovery of olfactory function.ConclusionOlfactory bulb volume is a predictor of olfactory recovery in patients suffering from PI and PT olfactory loss.