A study of hereditary essential tremor

Area of Science:

• Neurogenetics
• Movement Disorders
• Clinical Neurology

Background:

• Essential tremor (ET) is a common movement disorder, but its hereditary forms require precise phenotyping.
• Understanding the genetic and clinical spectrum of hereditary essential tremor (HET) is crucial for diagnosis and management.

Purpose of the Study:

• To define the phenotype of hereditary essential tremor (HET) in index patients and their relatives.
• To investigate inheritance patterns, age of onset, and associated clinical features of HET.

Main Methods:

• Studied 20 index patients with HET and 93 first-degree/38 distant relatives.
• Clinical examinations, segregation analysis for inheritance patterns, and assessment of tremor characteristics and disability.
• Investigated alcohol responsiveness, co-occurrence of other neurological conditions (e.g., dystonia, Parkinson's disease, migraine), and disability progression.

Main Results:

• Identified 53 definite and 18 possible secondary HET cases, with onset bimodally distributed around age 15.
• Autosomal dominant inheritance with near-complete penetrance by age 65; no skipping of generations observed.
• Typical phenotype: mild symmetrical postural tremor of upper limbs; alcohol responsiveness in ~50%, with family-specific heterogeneity in 20%; migraine co-segregated in ~26%.

Conclusions:

• Hereditary essential tremor presents as a distinct autosomal dominant condition with early onset and progressive disability.
• Phenotypic features, including tremor type and alcohol responsiveness, are generally consistent within families, though heterogeneity exists.
• Exclusion of dystonia and Parkinson's disease suggests HET is a distinct entity, with migraine as a potential co-occurring condition.