Abnormal Gray Matter Volume and Functional Connectivity in Parkinson’s Disease with Rapid Eye Movement Sleep Behavior Disorder

Abstract

Objective. Rapid eye movement (REM) sleep behavior disorder (RBD) is a common symptom in Parkinson’s disease (PD), and patients with PD-RBD tend to have an increased risk of cognitive decline and have the tendency to be akinetic/rigidity predominant. At the same time, the mechanisms of RBD in patients with PD remain unclear. Therefore, this study aimed to detect the structural and functional differences in patients with PD-RBD and PD without RBD (PD-nRBD). Methods. Twenty-four polysomnography-confirmed patients with PD-RBD, 26 patients with PD-nRBD, and 26 healthy controls were enrolled. Structural and functional patterns were analyzed based on voxel-based morphometry and seed-based functional connectivity (FC). Correlations between altered gray matter volume (GMV)/FC values and cognitive scores and motor impairment scores in PD subgroups were assessed. Results. Compared with patients with PD-nRBD, patients with PD-RBD showed relatively high GMV in the cerebellar vermis IV/V and low GMV in the right superior occipital gyrus (SOG). For the FC, patients with PD-RBD displayed lower FC between the right SOG and the posterior regions (left fusiform gyrus, left calcarine sulcus, and left superior parietal gyrus) compared with the patients with PD-nRBD. The GMV values in the right SOG were negatively correlated with the Unified PD Rating Scale-III scores in patients with PD-RBD but positively correlated with delayed memory scores. The GMV values in the cerebellar vermis IV/V were positively correlated with the tonic chin EMG density scores. There were positive correlations between the FC values in the right SOG-left superior parietal gyrus and MoCA and visuospatial skills/executive function scores and in the right SOG-left calcarine sulcus and delayed memory scores. Conclusion. Higher GMV in the cerebellum may be linked with the abnormal motor behaviors during REM sleep in patients with PD-RBD, and lower GMV and FC in the posterior regions may indicate that PD-RBD correspond to more serious neurodegeneration, especially the visuospatial–executive function impairment and delayed memory impairment. These findings provided new insights to learn more about the complicated characteristics in patients with PD-RBD.

Neuroimaging of rapid eye movement sleep behavior disorder and its relation to Parkinson's disease

“…When using a seed‐based approach of a priori regions of interest based on gray matter loss in PD patients with RBD, functional connectivity was lower between the right superior occipital gyrus and posterior regions including the left fusiform gyrus, left calcarine sulcus, and left superior parietal gyrus compared to PD patients without RBD. The reduced connectivity between the superior occipital gyrus and the superior parietal gyrus positively correlated with cognition (Jiang et al, 2021).…”

“…The authors relate such gray matter loss to cholinergic, GABAergic, and glutamatergic neuron depletion in the promotion of REM sleep and muscle atonia (Boucetta et al, 2016). A recent study on PD patients undergoing polysomnography confirmed RBD had higher cerebellar volume compared to PD patients unaffected by RBD in the vermis IV/V, and this was found to be associated with abnormal motor behavior during REM sleep (Jiang et al, 2021). In addition, reduced gray matter volume in the right superior occipital gyrus of PD patients with RBD was negatively associated with motor severity and positively associated with memory function (Jiang et al, 2021).…”

Neurochemical Features of Rem Sleep Behaviour Disorder

“…The results of studies assessing structural and functional MRI (fMRI) studies are summarized, in chronological order, in Table 4 [ 163 , 164 , 165 , 166 , 167 , 168 , 169 , 170 , 171 , 172 , 173 , 174 , 175 , 176 , 177 , 178 , 179 , 180 , 181 , 182 , 183 , 184 , 185 , 186 , 187 , 188 , 189 , 190 , 191 , 192 , 193 , 194 ]. These include sudies of gray matter volume (GMV), cortical thickness, diffusion tensor imaging, dorsal nigral hyperintensity (DNH), neuromelanin-sensitive structural and diffusion MRI, and functional MRI.…”

“…Compared with PD patients without RBD and controls, patients with concomitant PD and RBD or probable RBD have shown decreased volumes in the pontomesencephalic tegmentum (location of cholinergic, GABAergic, and glutamatergic neurons), medullary reticular formation, hypothalamus, thalamus, putamen, amygdala, and anterior cingulate cortex [ 171 ], volume decrease over time in the left caudate nucleus, pallidum and amygdale [ 187 ], and a relatively high GMV in the cerebellar vermis IV/V and low GMV in the right superior occipital gyrus [ 188 ].…”

“…Finally, two studies addressed the possible differences in functional connectivity (one of them in dynamic functional connectivity) between PD patients with and without concomitant RBD. One of them showed decreased functional connectivity between the right superior occipital gyrus and the posterior regions (left fusiform gyrus, left calcarine sulcus, and left superior parietal gyrus [ 188 ], and the other a brain pattern mainly marked by weaker positive couplings between visual network and default mode network, default mode network and basal ganglia network, and within default mode network [ 192 ], in PD patients with RBD compared with those without RBD.…”