Objective: To analyze and compare the electrophysiological signatures of ET and ET Plus

Background:

There is an on-going debate about the merits of classifying the heterogeneous group of essential tremor patients into essential tremor (ET) and essential tremor plus (ETP). It is not known whether this subclassification captures the phenotypic heterogeneity in ET or whether ETP represents a distinct etiological category from ET. We aimed to study whether tremor electrophysiological characteristics vary in patients classified clinically as ET or ETP.

Method:

Three movement disorder specialists reviewed standardized video recordings from a tremor database and classified patients into ET, ETP or dystonic tremor

(DT). Tremor severity was assessed using the Fahn-Tolosa-Marin tremor rating scale (FTM-TRS). Tremor was recorded in 8 positions using combined tri-axial accelerometry-surface Electromyography. For 4 positions i.e., Rest, Posture 1 (arms outstretched and elbows extended), Posture 2 (arms outstretched and elbows flexed with fingers pointing towards each other) and Load (500g),  power spectral density transform was performed, and following variables were derived- peak frequency (PF), total power (TP), peak power (PP), full width half maximum (FWHM), tremor stability index (TSI) and EMG-coherence between flexors and extensors. Electrophysiological characteristics were compared among ET, ETP and DT.

Results:

We screened 80 and included 72 participants in the study. Mean age (SD) was 47.7 (16.1) years, 59 (81.9%) were male and the mean disease duration was 9.5(6.7) years. Mean total FTM-TRS score was 31.1(14.1). Patients with ET were younger (p=0.014) and had less severe tremor (p=0.020) compared to the ETP and DT groups. Peak frequency was greater in ETP [7.3(0.3) Hz] compared to DT [6.1(0.4) Hz; p=0.024]. PP was greater in ETP and DT at posture 1 (ET vs ETP, p=0.009; ET vs DT, p=0.024) and posture 2 (ET vs ETP, p=0.041; ET vs DT, p=0.009). TP, FWHM, TSI, EMG coherence were similar among the groups.

Conclusion:

Electrophysiological evaluation revealed a predominant postural tremor of frequency 6-7 Hz in both ET and ETP. ETP was associated with more severe tremor and trend towards longer disease duration. Notwithstanding the presence of additional clinical features, electrophysiological characteristics were essentially similar between the groups ET and ETP.

« Back to 2023 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/essential-tremor-and-essential-tremor-plus-are-essentially-similar-on-electrophysiological-tremor-analysis-2/