Longitudinal Trajectories in Essential Tremor: Evidence From A Seven-Year Follow-Up of Motor and Non-Motor Symptoms

Essential tremor (ET) is a common movement disorder characterized by heterogeneous features, though the rate and pattern of worsening are variable. Longitudinal data combining clinical and objective motor measures remain limited, resulting in uncertainty regarding trajectories and predictors of progression in ET.

Twenty-two patients from a previously established ET/ET-plus cohort underwent a third clinical and kinematic evaluation almost seven years after baseline. Kinematic analysis assessed postural, kinetic, rest tremor, and finger-tapping performance. Longitudinal changes were evaluated using non-parametric statistics and linear mixed-effects models adjusting for clinical covariates.

Over time, tremor worsened overall. Kinematic measures indicated a selective increase in kinetic tremor severity, while rest and postural tremor amplitude remained stable. Clinically, tremor spread to a greater number of body regions. Soft neurological signs increased over time and were associated with greater tremor spread. Cognitive performance showed only a mild decline, partly related to age and affective symptoms. Higher baseline tremor severity was associated with greater worsening of kinetic tremor, and lower baseline cognitive scores with changes in postural tremor.

ET progression is heterogeneous and often non-linear. Kinematic measures were particularly sensitive in capturing worsening of kinetic tremor, the most disabling clinical feature. The accumulation of soft neurological signs and their association with tremor spread support the notion of ET-plus as a more advanced disease stage with broader cerebral involvement. Independent of disease progression, there were strong aging-related effects. Future multimodal longitudinal studies may clarify how aging interacts with disease trajectories in essential tremor.