Introduction

The olfactory bulb is responsible for processing information about odors detected by cells in the nasal cavity. It differentiates during adulthood and its growth is dependent on stimulation or sensory input. Lack of stimulation causes cell death and a decrease in its size and volume.

Rhinosinusitis is the most frequent cause of anosmia. It causes inflammation of the nasal sinuses which allows access of odors to the olfactory cleft and, disturbs the function of the olfactory epithelium which house cells in the nasal cavity that detect smell. This consequently leads to a decrease in the size of the olfactory bulb due to lack of stimulation (no sense of smell). Rhinosinusitis is treated using glucocorticoids and in case of presence of nasal polyps surgery is also indicated.

The aim of this study was to assess whether olfactory bulb volume increases after short term treatment in patients with a diagnosis of rhinosinisitis with polyps. A previous study done on rodents revealed it takes approximately 40 days for the olfactory bulb to regain its size after normalization of olfactory stimulation. The study participants were grouped into two; patients and healthy controls. Healthy controls were aged between 20 to 54 years while patients were aged between 36 to 73 years.  Olfactory function tests were done on both nostrils in both groups at the beginning of the study and 3 months later on follow up. Sniffin sticks tests was used to determine threshold odor (T), odor discrimination (D) and identification (I). Olfactory bulb volume was also measured using MRI scanners.

Results

There was a significant increase in patient TDI scores from 20 to 27 on the left nostril and 18.6 to 27 on the right nostril. There was also a significant increase in olfactory bulb volume among the patients. There was however no significant increase in neither TDI scores nor olfactory bulb volume among the controls. There was also no significant correlation between age, gender, odor identification and discrimination with changes in olfactory bulb volume.

Conclusion

Treatment of chronic rhinosinitis leads to olfactory stimulation. This consequently lead to an increase in volume on the left and right olfactory bulb by 9.4% and 18.4% respectively within 3 months from onset of therapy. Increase in stimulation causes an increase in progenitor cells (cells that differentiate into a specific type of cell) in the olfactory bulb as well as a decrease in cell mortality.