Background: The aim of this study was to assess the volume of the olfactory bulb (OB) in patients with chronic rhinosinusitis (without nasal polyposis at the endoscopic evaluation) and to evaluate the correlation between this measure and the degree of sinonasal inflammation.
Methods: Patients with sinonasal disease (SND; n = 22) were compared with healthy controls (n = 16) using orthonasal and retronasal olfactory test results and OB volumes measurement calculated by planimetric manual contouring using standardized methods. The Lund-Mackay score (originally described for CT scan) was also used to gauge sinonasal inflammation (SND score).
Results: The two groups were not significantly different in terms of age or distribution of sex. Patients had significantly higher right- and left-sided SND scores than controls. There was no significant group difference between patients and controls with regard to OB volume. However, patients with an SND score < or =12 had larger OB volumes than patients with higher SND scores (p < 0.001). Even when controlling for the subjects' age, a significant correlation was present between OB volume and SND score (r = -0.52; p = 0.001) with smaller OB volumes being associated with a higher degree of sinonasal pathology.
Conclusion: OB volume correlated with the SND score, which is an indicator of the degree of sinonasal inflammation. SND patients with a slight decrease or even normal olfactory function may already exhibit changes in their OB volume. This study also seems to emphasize the idea that OB volume changes are more sensitive to subtle changes in the olfactory system than results from psychophysical testing.