Longitudinal Progression of Essential Tremor: Do Tremor Severity Scores Increase at a Uniform Rate?

Abstract

BackgroundFew longitudinal studies assess the progression of essential tremor (ET). One unexplored issue is whether tremor severity increases across time at a uniform rate. That is, does the observed rate of change in tremor severity within a particular patient remain constant or vary across time? This question of intra-individual differences is particularly important since it reflects a primary patient concern–will the nature of change I have seen to date be what I can expect in the future?MethodsET cases were enrolled in a prospective, longitudinal study. We selected 35 cases and assessed tremor severity via Bain and Findley ratings of Archimedes spirals assigned by a senior movement disorders neurologist. After reviewing both the change in spiral scores and the rate of change in scores, we identified five mutually exclusive patterns of severity change. We calculated the prevalence of each category using two complementary sets of classification criteria.ResultsLength of follow-up was 4.5 to 16.0 years, mean=10.2 years. Mean baseline tremor severity score was 4.6, SD=1.6. Depending upon the classification criteria used, the tremor scores of one-third to one-half of cases did not increase in a uniform fashion but were better described as demonstrating jumps and/or reversals in scores across time.ConclusionsWe document the nature of changes in ET tremor severity scores across a ten-year period via expert ratings of Archimedes spiral drawings. Such natural history data are valuable to patients and clinicians who hope to better understand and predict the likely course of ET symptoms.

Elevated serum neurofilament light chain protein in patients with essential tremor

“…Although generally regarded as progressive in nature, the course of this disease is not well understood as few longitudinal clinical studies of patients with ET are available [31]. A recent study highlighted the unpredictability of disease progression over time for many individuals with ET and the need for markers to predict the likely course of ET motor and nonmotor symptoms [32]. sNfL or probably the change of sNfL in the first years after symptom onset may be useful in subclassifying patients with ET, which is mandatory in order to uncover the so far unknown various aetiologies of this common tremor syndrome.…”