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.

Normal 'heart' in Parkinson's disease: is this a distinct clinical phenotype?

BACKGROUND AND PURPOSE: Reduction of metaiodobenzylguanidine (MIBG) uptake has been observed in almost all patients with Parkinson's disease (PD), associated with hyposmia, orthostatic hypotension and rapid eye movement sleep behavioral disorder (RBD). In contrast, a subgroup of patients with PD with normal MIBG uptake have been reported to have milder disease and preserved cognition compared with those with lower MIBG. The aim of this study was to investigate whether non-motor manifestations of PD differ between patients with normal and abnormal myocardial MIBG uptake. METHODS: Among 160 de-novo cases of PD, 44 had normal MIBG uptake. Twelve candidate non-motor features were evaluated using questionnaires and laboratory tests. RESULTS: Patients with decreased MIBG uptake had more constipation, RBD, cognitive impairment, hyposmia and orthostatic hypotension than did those with normal MIBG uptake. On linear regression analysis, orthostatic hypotension, olfactory function and probable RBD were significantly associated with MIBG uptake in PD. The principal component analysis showed that the group with normal MIBG was not associated with non-motor impairments. CONCLUSIONS: These results suggest that patients with PD with normal MIBG scans have a relatively low disease burden compared with those with abnormal MIBG. Fewer synuclein pathologies in the myocardia and sympathetic ganglia in PD with preserved MIBG uptake might be associated with lower threshold patterns of Braak synuclein pathology for non-motor manifestations compared with PD with decreased MIBG.