Olfactory brain gray matter volume reduction in patients with chronic rhinosinusitis

Background: Chronic rhinosinusitis (CRS) is a common inflammatory condition and a major cause of olfactory loss. Olfactory dysfunction has been associated with reduced olfactory bulb (OB) volume and gray matter (GM) density in the olfactory-related brain areas. The aim of this study was to investigate brain GM structural and OB volume alterations in patients with CRS. Methods: Structural brain images were collected from 21 CRS patients and 31 healthy controls on a 3-T scanner. Voxel-based morphometry (VBM) was performed to investigate GM. Olfactory bulb volumes were measured using AMIRA software. Psychophysical olfactory testing for odor threshold (T) and identification (I) was performed using the Sniffin' Sticks battery. Results: CRS patients had significantly lower scores for Sniffin' Sticks olfactory tests than controls (p < 0.001 for T, I, and combined T and I [TI] scores). Region-of-interest analyses revealed no difference in GM volume between CRS patients and healthy controls; however, in CRS patients with severe olfactory dysfunction, GM reduction was observed in the gyrus rectus, orbitofrontal cortex, thalamus, and the insula. In addition, no difference was observed for OB volume in CRS patients compared with healthy controls. Conclusion: In this study we identified a reduction in gray matter in olfactory brain regions in CRS patients with severe olfactory dysfunction.