MICROSTRUCTURE-SENSITIVE T1W/T2W GRADIENTS REVEAL ALTERED STRIATAL PROFILES ASSOCIATED WITH RESTING TREMOR IN PARKINSON’S DISEASE

The link between PD resting tremor (RT) and dopaminergic dysfunction is unclear, and RT may represent a partially distinct clinical entity. We found that higher caudate, but not putaminal, dopamine terminal integrity relates to RT, yet limited DaT spatial resolution constrains striatal characterization. We tested whether T1w/T2w microstructure-sensitive imaging would reveal different microstructural gradients between PD patients with RT (PD-RT) and without RT (PD-NRT).
The Parkinson’s Progression Markers Initiative was searched for baseline and 2-year 3T Siemens Trio T1w and T2w MRI scans from PD patients and matched controls, which were co-registered and normalized to MNI space. A T1w/T2w ratio map was computed, and 3D caudate and putamen volumes segmented; voxel-wise T1w/T2w values were then compared between PD-RT and PD-NRT. Images from 157 PD patients (102RT, 55NRT) and 67 controls were selected. PD-RT and PD-NRT groups did not differ in age, disease duration, or UPDRS without RT. Compared to PD-RT, PD-NRT patients showed increased caudate T1w/T2w ratios (F(1,1085)=7.94,p=0.005), but no putamen effect (F(1,1085)=1.68,p=0.19); this pattern persisted after matching for institution, sex, and age. PD-RT patients displayed T1w/T2w values closer to controls (caudate: F(1,169)=0.97,p=0.324; putamen: F(1,1169)=0.51,p=0.476). Longitudinally, PD-NRT patients retained higher T1w/T2w ratios than PD-RT patients (caudate: F(1,840)=11.17,p<0.001; putamen: F(1,840)=17.38,p<0.001). Striatal T1w/T2w microstructural gradients reveal consistent differences between PD patients with and without RT, with prominent caudate effects. These differences were reproducible at follow-up and extended to the putamen, indicating a pattern of striatal microstructural variation in relation to RT, without additional granularity despite the higher spatial resolution of MRI.