Olfactory cortex and Olfactory bulb volume alterations in patients with post-infectious Olfactory loss

Upper respiratory tract infection (URI) is one of the most common etiology of olfactory loss. Previous studies demonstrated that both olfactory bulb (OB) volume and sulcus (OS) depth decreased in patients with post-infectious olfactory loss (PIOL) compared to normal controls. The aim of our study was to observe alterations of central olfactory pathways in patients with PIOL. T1 weighted magnetic resonance images were acquired in 19 PIOL patients and 19 age- and sex-matched control subjects on a 3 T scanner. Voxel-based morphometry (VBM) was performed using VBM8 toolbox and SPM8 in a Matlab environment. We also analyzed OB volume in coronal T2-weighted images. Whole-brain analysis revealed a significant gray matter volume loss in the right orbitofrontal cortex (OFC) in patients group. Further analysis with region of interest exhibited a significant negative correlation between gray matter volume in right OFC as well as OB volume and the duration of olfactory loss in these patients (r = -0.566 and r = -0.535 both P < 0.05, respectively). In conclusion, the morphological alterations in the right OFC and OB might contribute to the pathogenic mechanism of olfactory dysfunction after upper respiratory tract infection.