Correlation of olfactory function with changes in the volume of the human olfactory bulb.

OBJECTIVE To investigate changes of olfactory bulb (OB) volume over time in relation to olfactory function. DESIGN Prospective, before-after trial. SETTING Outpatient clinic of a university clinic for otorhinolaryngology. PATIENTS A total of 20 patients with olfactory loss participated in the study. The duration of olfactory deficits ranged from 3 months to 6 years. MAIN OUTCOME MEASURES Olfactory function was assessed for phenyl ethyl alcohol odor threshold, odor discrimination, and odor identification. Olfactory bulb volume was determined using magnetic resonance imaging. RESULTS In initially hyposmic patients (n = 13), changes in OB volume were found to correlate with odor threshold changes (r = 0.82; P = .001); no such correlation was found for odor discrimination or odor identification. CONCLUSION As demonstrated in a longitudinal study for the first time to our knowledge, the human OB is a highly plastic structure that responds to individual changes in olfactory status.