UNCOVERING FUNCTIONAL IMAGING CORRELATES OF REST TREMOR IN PARKINSON’S DISEASE

Rest tremor (RT) hubs in Parkinson’s disease are yet to be settled and resting-state fMRI may help identify and clarify how activity in specific regions relates to tremor pathophysiology. However, most previous studies classified patients using ratios of symptom severity rather than the presence or absence of RT, introducing heterogeneities in the results. Thus, we aim to identify functional features associated with RT using measures of local spontaneous activity and synchrony.
We included participants from the Parkinson’s Progression Markers Initiative with confirmed PD and available baseline UPDRS, resting-state fMRI and structural MRI. Patients were divided into RT and no-RT groups and analyses were restricted to a single-scanner cohort (RT=62;no-RT=25), to limit scanner-related variability. Local resting-state activity was quantified using Regional Homogeneity (ReHo) and fractional Amplitude of Low Frequency Fluctuations (fALFF).
Whole-brain analyses were conducted to screen for RT-related differences, controlling for relevant variables, namely age, sex, disease duration and UPDRS without RT. No whole-brain differences survived family-wise error correction. In exploratory maps, increases in ReHo and fALFF in the RT group converged on three regions: primary motor cortex, supplementary motor area and precuneus.
These findings suggest that RT is associated with abnormal spontaneous activity and synchrony in key hubs, even at rest. Classifying patients according to the presence or absence of RT allows isolation of RT-specific functional features. Although effects did not survive whole-brain correction, convergence across metrics supports biological relevance. Future research should incorporate network-level and lateralized analyses to better capture underlying RT circuitry.