gms | German Medical Science

Olfactory training plays a significant role in the treatment of hyposmia. It is known that repeated exposure to odors modifies olfactory function. In addition, numerous studies show that the olfactory bulb (OB) volume changes under various conditions, e.g. in patients suffering from olfactory dysfunction smaller OBs were found than in healthy subjects. The aim of this study was to investigate whether the OB volume changes in relation to lateralized olfactory training.

Over a period of 4 months 97 healthy participants (34 men, 63 women) performed olfactory training. For the whole period, they were exposing the same nostril twice a day to 4 odors (lemon, rose, eucalyptus and cloves) while closing the other one. Before starting and after finishing the olfactory training, MRI scans were performed to measure the OB volume. Furthermore, participants underwent lateralized threshold and identification testing using the “Sniffin Sticks” test battery.

Although there was no significant change in olfactory function comparing results before and after training, it was found that the OB volume increased significantly by 11.3% in the trained nostril and 13.1% in the untrained nostril. No significant effect was found comparing the influence of gender, the exact duration and frequency of the training as well as the age of the subjects and the method of closing the untrained nostril.

These data indicate that olfactory training induces a top-down process which ultimately leads to a bilateral increase in OB volume.