Magnetic resonance imaging assessment of the substrate for hyposmia in patients with Parkinson's disease

AIM To assess whether multimodal magnetic resonance imaging (MRI) could detect neuroanatomical substrates that are distinctive to hyposmic Parkinson's disease (PD). MATERIALS AND METHODS Among 102 PD patients, 62 were hyposmic and 40 were normosmic. For each patient, a sagittal structural three-dimensional (3D) T1-weighted image was obtained with the magnetisation-prepared rapid acquisition of the gradient-echo sequence to generate subcortical grey matter masking templates and to perform a voxel-based morphometry analysis of the subcortical grey matter volumes. A 3D multi-echo gradient sequence was run to obtain axial magnitude and phase images to produce a quantitative susceptibility map (QSM), and a diffusion-weighted image was acquired to generate an apparent diffusion coefficient (ADC) map. The volumes and average QSM and ADC values of the 15 subcortical grey matter structures were calculated, and the group differences were evaluated using a one-way analysis of covariance with age and gender as covariates. RESULTS The QSM of the left thalamus significantly increased, while that of the right thalamus significantly decreased in hyposmia. No effects on the cortical volume changes were found other than aging. CONCLUSION The present results suggest that accumulation of disease-related substances in the left and right thalamus and the increasing asymmetry between the two sides are associated with hyposmia in PD.