Temporal Dynamics of Parkinson's Disease Tremor: Clinical and Neuroimaging Insights.

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder clinically defined by three cardinal motor symptoms: bradykinesia, rigidity, and tremor. Although the natural history of bradykinesia and rigidity is well described, the evolution of tremor as the disease progresses remains controversial.

OBJECTIVES

The goal was to clinically characterize long-term trajectories of rest, postural, and action tremor in PD and examine their neural network correlates using longitudinal resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

In this retrospective longitudinal cohort study, we analyzed 93 tremor-positive PD patients (mean disease duration: 3.6 years), each with up to six clinical assessments over 4.2 years. Linear mixed-effects models assessed temporal change in Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) and Fahn-Tolosa-Marín Tremor Rating Scale (FTM-TRS) scores. Rs-fMRI data from 30 tremor-affected patients (mean interval, 3.35 years) were analyzed for seed-to-whole-brain connectivity and connectivity between predefined brain regions.

RESULTS

Bradykinesia (β = +0.09, P < 0.001) and rigidity (β = +0.06, P < 0.001) worsened, whereas total FTM-TRS scores declined by 0.49 points/year (P = 0.037), driven by reductions in postural (P < 0.001) and action tremor (P = 0.033); resting tremor remained stable. Rs-fMRI revealed longitudinal changes in cerebellar- and thalamic-seed-to-whole-brain connectivity.

CONCLUSIONS

Tremor in PD evolves along distinct clinical courses, often stabilizing or improving as other motor features worsen. These findings are consistent with partially adaptive reorganization within tremor-related networks and underscore the importance of identifying patient subtypes with divergent trajectories to inform prognosis and optimize therapy. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.