Key Facts

Essential tremor (ET) is the most common movement disorder, often underdiagnosed and undertreated. It is a clinical diagnosis requiring exclusion of other causes of tremor. Despite its name, ET can cause significant functional impairment and social embarrassment.

Epidemiology

Prevalence ~1% overall; ~5% in over-60s. Bimodal age of onset (peak in 2nd-3rd decade and 6th-7th decade). Positive family history in ~50% (autosomal dominant with variable penetrance). Equal sex distribution.

Aetiology

• Genetic: autosomal dominant with variable penetrance; multiple loci identified (ETM1, ETM2, LINGO1 gene polymorphism)
• Sporadic: cases without family history — possibly polygenic or de novo
• Exact genetic basis remains incompletely understood

Pathophysiology

The pathophysiology is not fully understood. Involves oscillatory activity within the cerebello-thalamo-cortical network. Inferior olive → cerebellum → VIM thalamus → motor cortex circuit generates rhythmic tremor. Post-mortem studies show Purkinje cell loss and cerebellar degeneration in some ET patients, suggesting ET may be a neurodegenerative condition. GABA receptor dysfunction in the cerebellum may contribute (basis for alcohol and primidone response).

Tremor Characteristics

• Action tremor: present during voluntary movement (e.g., writing, drinking, eating)
• Postural tremor: present when maintaining posture against gravity (e.g., arms outstretched)
• Frequency: 4-12 Hz (typically 6-8 Hz)
• Bilateral (may be asymmetric but almost always bilateral)
• Progressive: slowly worsens over years/decades

Distribution

• Hands/arms: most common (95%); interferes with writing (large, irregular — vs micrographia in PD), drinking, eating
• Head: titubation (yes-yes or no-no nodding) — ~30%
• Voice: tremulous speech — ~20%
• Legs: uncommon

Associated Features

• Improves with alcohol (ethanol)
• Worsens with anxiety, caffeine, fatigue, cold
• No bradykinesia, no rigidity, no postural instability
• Gait usually normal (mild tandem gait difficulty in some)

Red Flags (Suggest Alternative Diagnosis)

• Rest tremor (PD)
• Bradykinesia or rigidity (PD)
• Unilateral tremor that remains unilateral (PD)
• Acute onset (drug/toxin, psychogenic)
• Associated neurological signs (cerebellar signs, dystonia, neuropathy)

Clinical Diagnosis

• Diagnosis is clinical: bilateral action/postural tremor ± head/voice tremor; no bradykinesia/rigidity; family history supports
• No specific blood test or imaging required for typical presentation

Investigations (if Diagnostic Uncertainty)

• DaTSCAN: NORMAL in ET (abnormal in PD) — key differentiating investigation
• TFTs: exclude hyperthyroidism (enhanced physiological tremor)
• U&Es, LFTs: metabolic causes
• Drug review: valproate, lithium, amiodarone, salbutamol, SSRIs
• MRI brain: if cerebellar signs or atypical features
• EMG/accelerometry: research/specialist use — characterise tremor frequency and pattern

Non-pharmacological

• Reassurance: ET is not PD; ET is benign in terms of life expectancy
• Lifestyle: reduce caffeine, manage stress/anxiety, adequate sleep
• Weighted utensils/adaptive devices: practical aids for eating/drinking
• Occupational therapy: functional strategies

Pharmacological

• First-line: propranolol 40-320 mg/day (long-acting SR formulation preferred — 80-160 mg OD; tremor reduction 50-70%; contraindicated in asthma, heart block, severe bradycardia)
• Alternative first-line: primidone 25-750 mg/day (start very low — 12.5-25 mg ON; titrate slowly; metabolised to phenobarbitone; sedation and dizziness common initially)
• Second-line: topiramate 25-400 mg/day (weight loss, cognitive side effects), gabapentin 300-2400 mg/day
• Others: alprazolam (short-term), botulinum toxin (head/voice tremor)

Surgical (Refractory)

• Deep brain stimulation (DBS): VIM (ventral intermediate nucleus) thalamic DBS; for severe, medication-refractory ET causing significant disability; NICE IPG — 60-80% tremor reduction
• MRI-guided focused ultrasound (FUS) thalamotomy: non-invasive alternative to DBS; unilateral only; NICE IPG

Referral Criteria

• Neurology: diagnostic uncertainty, poor treatment response, consideration of DBS
• Functional impact: occupational therapy assessment

ET is a slowly progressive condition. Tremor amplitude typically increases over decades. Frequency may decrease with age. ET does NOT reduce life expectancy. Functional impairment is common — many patients have difficulty with writing, eating, drinking, and fine motor tasks. Social embarrassment is significant. ~50% of patients require treatment. Propranolol and primidone provide good symptomatic relief in most. DBS is highly effective for refractory cases. Some epidemiological studies suggest a modestly increased risk of dementia and PD in ET patients, but this remains debated.

Essential Tremor vs Parkinson Disease Tremor