Essential Tremor and Essential Tremor Plus Are Essentially Similar Electrophysiologically

Area of Science:

• Neurology
• Movement Disorders
• Electrophysiology

Background:

• The classification of essential tremors into essential tremor (ET) and essential tremor plus (ETP) remains debated.
• Understanding the distinct characteristics of these tremor types is crucial for accurate diagnosis and management.

Purpose of the Study:

• To investigate the electrophysiological and spiral characteristics of tremor in essential tremor (ET) and essential tremor plus (ETP).
• To compare these characteristics with dystonic tremor (DT) to elucidate potential overlaps or distinctions.

Main Methods:

• Standardized videos and clinical classifications from a tremor database were used to categorize patients into ET, ETP, or DT.
• Electrophysiological data (accelerometry-EMG) and hand-drawn spiral analyses were performed to derive key tremor variables.
• Variables included peak frequency, power, stability index, EMG-coherence, and spiral deviations.

Main Results:

• Patients with ET were younger and had less severe tremors compared to ETP and DT.
• ETP exhibited a higher peak frequency (7.3 Hz) than DT (6.1 Hz), with 48.6% of ETP patients showing subtle dystonia.
• Postural tremor peak power was greater in ETP and DT; rest tremor was less common in ET.

Conclusions:

• Electrophysiological findings reveal a 6-7 Hz postural tremor in ET, ETP, and DT, with ETP and DT showing more severe tremors.
• Higher tremor frequency in ETP compared to DT was noted.
• The similar tremor oscillators suggest these conditions may represent a spectrum of tremor disorders rather than distinct entities.