Interhemispheric functional connectivity changes in early Parkinson disease with the symptom asymmetry

Objective: To investigate changes of the interhemispheric coordination integrity in patients with hemi-parkinsonism using resting- state functional magnetic resonance imaging(rs-fMRI) homotopy technique called voxel-mirrored homotopic connectivity(VMHC). Methods: Sixteen Parkinson disease(PD) patients with right body side motor symptom onset(RPD), 15 patients with left side onset(LPD), and 19 age-, gender-, and education-matched healthy controls(HC) were included in this study. rs-fMRI scanning and pre-processed the raw data were performed. Then by using analysis of variance(ANOVA) and two sample t test, we performed VMHC analyses on rs-fMRI data of these participants(P < 0.05, corrected with AlphaSim, clusters ≥16 voxels). Exploratory linear correlations analyses were performed between the VMHC of regions showing significant group differences and the clinical features of LPD or RPD patients. Results: Compared with HCs, patients with LPD had significantly reduced VMHC in visual regions, sensorimotor regions, and the cerebellar cortex(voxels size of 17-77, t = -5.06--3.42, P < 0.05). Patients with RPD exhibited decreased VMHC in the prefrontal cortex and sensorimotor regions. Both LPD and RPD groups had increased VMHC in subcortical regions. When compared with the RPD group, the LPD group displayed decreased VMHC in the visual regions, sensorimotor regions(voxels = 16 and 18; t = -3.68 and -3.87, respectively, both P < 0.05) and increased VMHC in the supramarginal gyrus(voxels = 4, t = 4.72, P < 0.05); ROI-based correlation analyses indicated that the VMHC in the inferior occipital gyrus and the postcentral gyms was negatively correlated with the BDI-II scores in the LPD group(r = -0.58 and -0.59, respectively; both P < 0.05), and positively correlated with the MMSE scores(r = 0.56 and 0.52, respectively; both P < 0.05). In the RPD group, a positive correlation was found for the VMHC in the supramarginal gyrus and the illness duration(r = 0.56, P < 0.05) and for the VMHC in the postcentral gyrus and the(mini-mental state exam) MMSE(r = 0.53, P < 0.05). Conclusions: The differential pattern of deficits in the interhemispheric coordination integrity in hemi-parkinsonism reflected by VMHC may provide insights into the neurological pathophysiology underlying the asymmetry of symptom appearance in PD. (authors)