Table 1.

Most important MRI findings in Parkinson’s Disease (PD)

Technique	MR Imaging Findings
T1-w	● The brain seed locations in both cortical and subcortical areas exhibited substantial structural pattern alterations [15]
	● Patients with sleep disorders exhibited regions of decreased GMV* and WM alterations in the cortex [16]
	● PD-RBD patients revealed more nodal property alterations within the neocortex and limbic system [17]
	● The pontomesencephalic tegmentum, medullary reticular formation, hypothalamus, putamen, and anterior cingulate cortex reduced volumes in PD patients [11]
	● High GMV was found in the cerebellar vermis, whereas low GMV was seen in the right SOG of patients with PD-RBD [18]
	● There was more GM atrophy in the PD with probable RBD group for men than for females [19]
	● In PD patients with RBD, the right putamen had a lower volume. The greater volume of the right putamen, left hippocampus, and left thalamus shows the more significant the severity of RBD symptoms [20]
	● There was a correlation between excessive daytime sleepiness and an increased OSA in individuals with PD and PSP, which indicates extensive degradation of brainstem sleep components [21]
	● That patients with troubling nocturia had reduced cortical surface on the left pre-and postcentral regions, and total WM volume decreased bilaterally as well [22]
	● PD Patients with RBD had significantly lower GM volume in the right thalamus [23]
	● The PDRBD+ group had lower GM volume in the left posterior cingulate and hippocampus compared to the PDRBD-, as well as additional lower GM volume in the left precuneus, cuneus, medial frontal gyrus, postcentral gyrus, and both inferior parietal lobules compared to the HC group [24]
	● There was substantial degeneration of GM in the frontal, temporal, and occipital regions of the brain in individuals with EDS compared to controls [25]
	● There was increased regional GM volume in both the hippocampus and the parahippocampal gyri in the PD-EDS group [26]
	● PD patients with impaired phonetic-fluency (a frontal lobe function) and those with iRBD or PDND who had lower levels of total-α-synuclein in their CSFτ were shown to have thinner frontal cortices, regardless of the presence of in their CSF [27]
Diffusion-based	● Pathways (CC, IFOF, CST, and MCP) with decreased anisotropy were found in PD patients with RBD compared to those without RBD [28]
	● The PD with sleep disruption group revealed extensive WM degeneration [29]
	● ALFF values in the main motor cortex and premotor cortex were significantly lower in individuals with RBD than in those with PD without RBD [30]
	● The right cingulum, left and right fornix, left ILF, right CST, right MCP, and genu of corpus callosum connections were considerably decreased in PD-RBD subjects with depressive symptoms [31]
	● The PD-EDS group was shown to have higher AD values in both the left anterior thalamic radiation and CST, as well as bilaterally in superior corona radiata and SLF [26]
fMRI	● PD-RBD patients revealed more nodal property alterations within the neocortex and limbic system [17]
	● The ReHo values of the ACC varied considerably across the PD groups patients [18]
	● Cortical FC in the default mode, central executive, and dorsal attention networks was less severely reduced in PD patients with sleep disturbances [29]
	● Both RBD and PD were identified by connectivity measurements of basal ganglia network dysfunction with excellent specificity (74% for RBD disorder, and 78% for PD), highlighting its potential as an early indication of basal ganglia dysfunction [32]

^*Abbreviations: GMV: Gray Matter Volume; WM: White Matter; PD: Parkinson’s Disease; RBD: Rapid Eye Movement (REM) Sleep Behavior Disorder (RBD); SOG: Superior Occipital Gyrus; OSA: Obstructive Sleep Apnea; PSP: Progressive Supranuclear Palsy; HC: Healthy Control; EDS: Excessive Daytime Sleepiness; iRBD: Idiopathic RBD; PDNP: PD Patients with No Dementia; CSF: Cerebrospinal Fluid; CC: Corpus Callosum; IFOF: Inferior fronto Occipital Fasciculi; CST: Corticospinal Tract; MCP: Middle Cerebellar Peduncle; ALFF: Amplitude of Low Frequency Fluctuation; ILF: Inferior Longitudinal Fasciculus; AD: Axial Diffusivity; SLF: Superior Longitudinal Fasciculus; ReHo: Regional Homogeneity; ACC: Anterior Cingulate Gyrus; FC: Functional Connectivity.