What is Essential Tremor?
Essential tremor is a progressive neurological syndrome characterized primarily by bilateral action tremor of the arms and hands, with a prevalence in the US between 0.3% and 5.55%, making it the most common movement disorder in adults. 1, 2
Core Clinical Features
Essential tremor presents with specific defining characteristics that distinguish it from other tremor disorders:
- Bilateral action tremor involving the hands and forearms that is visible and persistent, occurring with both postural (holding a position) and kinetic (during movement) activities 1, 2
- Tremor frequency typically ranges between 4-8 Hz 3
- Duration requirement of at least 3 years of bilateral action tremor for definitive diagnosis 1, 4
- Consciousness remains completely intact during tremor episodes, distinguishing it from other neurological conditions 3
Beyond the Hands: Extended Manifestations
While classically considered a hand tremor disorder, essential tremor can affect multiple body regions:
- Head tremor (neck) may occur, though isolated head tremor without hand involvement argues against the diagnosis 1, 5
- Voice tremor affecting the vocal cords is common 4, 5
- Leg, feet, trunk, jaw, chin, and tongue tremor may develop 5
- Task- and position-dependent tremor should be absent for classical essential tremor diagnosis 3
Non-Motor Features: A Multisystem Disorder
Essential tremor extends beyond pure motor symptoms to affect multiple domains of function:
- Cognitive impairments including memory problems, executive dysfunction, and in some cases dementia 1, 5
- Psychiatric disturbances such as anxiety, depression, and social phobia 5
- Gait disturbances and ataxia may develop as the condition progresses 5
- Sensory abnormalities including olfactory deficits and hearing loss 1, 5
Functional Impact and Quality of Life
Essential tremor significantly interferes with quality of life, functional activities, mood, and socialization, and can cause greater impairment than Parkinson's disease in activities like writing, eating, drinking, and reading. 1
Exacerbating Factors
Tremor severity worsens predictably with specific triggers:
- Emotional stress intensifies tremor amplitude 3
- Caffeine consumption exacerbates symptoms 3
- Physical exertion increases tremor severity 3
Essential Tremor vs. Essential Tremor Plus
The updated 2018 consensus statement created a distinction:
- Classical essential tremor: Isolated bilateral action tremor with no other neurological signs explaining the tremor 6, 4
- Essential tremor plus: Patients with additional neurological signs of unknown origin beyond the tremor itself 6, 4
This classification provides better subtyping for research and clinical management, though some experts have critiqued this terminology 2.
Pathophysiology
The immediate cause involves:
- A preformed oscillating network within the central nervous system that enters a tremor mode, revealed through electrophysiological studies 6
- Adaptive changes in the brain, particularly in the cerebellum, though definitive neurodegeneration has not been convincingly proven 6
- Various underlying etiologies likely contribute to what appears clinically as a relatively uniform condition 6
Diagnostic Exclusions
The following conditions must be ruled out before diagnosing essential tremor:
- Cerebrovascular disease, demyelinating disease, metabolic disorders, brain trauma, and psychological disorders 3
- Red flags include tremor duration less than 1 minute per episode, age of onset over 20 years, and abnormalities on brain CT/MRI 3
Progressive Nature
Essential tremor is a chronic, progressive syndrome that typically worsens over time, though the rate of progression varies among individuals 2, 6.