Causes of Essential Tremor
Essential tremor is a chronic, progressive neurodegenerative disorder primarily caused by dysfunction in the cerebellum and cerebellar system, with both genetic and environmental factors contributing to its development. 1, 2
Pathophysiology and Neuroanatomical Basis
- Cerebellum and Cerebellar System: The primary site of pathology in essential tremor is the cerebellum and its connections 2
- Central Motor Network Involvement: Essential tremor involves the central motor network including:
- Cerebellum
- Thalamus (particularly the ventral intermediate nucleus)
- Cortical networks 3
- Neurodegenerative Changes: Research has identified neurodegenerative changes within the cerebellum, supporting the classification of essential tremor as a degenerative disorder 2
Etiological Factors
Genetic Factors
- Family History: Essential tremor often has a familial pattern, suggesting strong genetic components 1
- Heterogeneity: There is growing evidence that essential tremor may represent a family of diseases rather than a single entity, sometimes referred to as "the essential tremors" 2
Environmental Factors
- Toxic Exposures: Environmental toxins have been explored as potential contributors to essential tremor development 2
Clinical Characteristics
- Prevalence: Essential tremor is the most common movement disorder after restless leg syndrome, with prevalence in the United States estimated between 0.3% and 5.55% 4
- Progression: Essential tremor is typically progressive, with symptoms worsening over time 4, 2
- Impact: While essential tremor does not shorten life expectancy, it can significantly interfere with quality of life, functional activities, mood, and socialization 4
- Disease Associations: Essential tremor appears to be a risk factor for other neurodegenerative conditions including:
- Alzheimer's disease
- Parkinson's disease 2
Diagnostic Classification
- Activation Conditions: Essential tremor can be classified by activation condition 1:
- Postural tremors (4-8 Hz): Occur when maintaining position against gravity
- Kinetic tremors: Occur during voluntary movement
- Rest tremors (4-6 Hz): Occur when body part is relaxed and supported
Differential Diagnosis Considerations
When evaluating tremor, it's important to rule out other causes:
- Parkinsonian syndromes: Including Parkinson's disease, progressive supranuclear palsy, multiple system atrophy, and corticobasal degeneration 4
- Drug-induced tremor: Medications can cause or exacerbate tremor 5
- Metabolic disturbances: Various metabolic abnormalities can present with tremor 5
- Dystonic tremor: Can sometimes be confused with essential tremor 6
Evaluation for Secondary Causes
Laboratory testing to rule out secondary causes should include:
- Thyroid function tests
- Liver function tests
- Basic metabolic panel
- HbA1c
- Consider copper studies if Wilson's disease is suspected 1
Essential tremor represents a complex neurological condition with multiple contributing factors rather than a single cause. The growing understanding of its pathophysiology has led to recognition that it may represent a family of related disorders with similar clinical presentations but potentially different underlying mechanisms.