Regional homogeneity analysis of major Parkinson's disease subtypes based on functional magnetic resonance imaging

Regional homogeneity (ReHo) differences in encephalic regions of Parkinson's disease (PD) patients of different subtypes were investigated to analyze its clinical significance during disease occurrence.

39 PD patients were evaluated in this study, which included 14 cases with the tremor dominant (TD) PD subtype and 23 cases with the postural instability and gait difficulty (PIGD) PD subtype, along with 28 healthy individuals, who were included as the control group. Magnetic resonance imaging (MRI) was performed for all the cases to obtain the rest-state functional magnetic resonance imaging (R-fMRI) data along with structural data. The ReHo values of the three groups were calculated and disparities in brain structures among the three groups were processed by analysis of variance. In addition, t-test analysis was used to evaluate the differences between the groups. In the end, a correlation analysis between the brain areas evaluated for ReHo differences and the clinical symptoms presented by the patients was carried out.

Compared to the control group, brain areas with increased ReHo values in the TD PD subtype group, included the right putamen, right para-hippocampal gyrus, right inferior temporal gyrus, and right orbital superior frontal gyrus, while areas with decreased ReHo values, included the bilateral superior occipital gyrus and bilateral middle occipital gyrus. In contrast with the control group, areas like the right putamen, right superior temporal gyrus, left thalamus, and right superior parietal gyrus in the PIGD PD subtype group presented an increased in ReHo values, while a decreased in ReHo values was found in the right para-hippocampal gyrus, bilateral superior occipital gyrus, and middle occipital gyrus. Compared to the PIGD group, the TD group showed an increase in ReHo values in the right para-hippocampal gyrus.

In the present study, ReHo values increased in the TD PD subtype group of patients, indicating a compensatory performance of slow progressive cognitive decline when compared to the PIGD PD subtype group. Two subtypes of PD manifest ReHo changes in the basal ganglia, thalamus, and in several areas of the cerebral cortex, areas that are likely to correlate with non-motor symptoms, such as cognition and emotions.