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Saturday, August 23, 2025

Essential tremor


Introduction

Essential tremor (ET) is a chronic neurological disorder characterized by involuntary, rhythmic shaking, most commonly affecting the hands and forearms, but sometimes the head, voice, legs, or trunk. It is typically action tremor (occurs during voluntary movement such as writing or holding a cup), unlike the resting tremor of Parkinson’s disease.

It affects 0.5–5% of the population, with prevalence increasing with age. Although often considered benign, it can be functionally disabling, affecting daily activities, social interaction, and quality of life.

Pathophysiology

  • The exact mechanism remains unclear.

  • Likely due to abnormal oscillatory activity within the cerebello-thalamo-cortical pathway.

  • Neuroimaging and genetic studies support dysfunction in the cerebellum.

  • Genetic predisposition: ET often runs in families; inheritance is usually autosomal dominant.

Risk Factors

  • Age: More common after age 40, but can appear earlier.

  • Family history: First-degree relatives often affected.

  • Environmental triggers: Caffeine, stress, fatigue, and certain medications may exacerbate tremor.

Clinical Features

  • Tremor type: Bilateral, symmetrical, action/postural tremor.

  • Common sites:

    • Hands and arms (95%)

    • Head (“yes-yes” or “no-no” shaking)

    • Voice (quivering speech)

    • Legs and trunk (less common)

  • Improves with alcohol intake (reported by many patients).

  • Worsens with stress, anxiety, fatigue, caffeine.

  • No other neurological deficits (unlike Parkinson’s disease which includes rigidity, bradykinesia).

Differential Diagnosis

  • Parkinson’s disease: Rest tremor, bradykinesia, rigidity, asymmetry.

  • Enhanced physiological tremor: Stress, caffeine, drugs.

  • Hyperthyroidism: Fine tremor, weight loss, tachycardia.

  • Medication-induced tremor: Lithium, valproate, bronchodilators.

  • Dystonic tremor: Associated with abnormal postures.

  • Cerebellar tremor: Intention tremor with ataxia.

Diagnostic Approach

1. Clinical Diagnosis (Key)

  • Bilateral action tremor of hands/forearms for >3 years.

  • Absence of other neurological signs.

  • Family history supports diagnosis.

2. Laboratory Tests

  • Thyroid function tests (rule out hyperthyroidism).

  • Drug history (exclude medication-induced tremor).

3. Imaging

  • Usually not required, but MRI/CT if atypical features or rapid progression.

Management

Treatment is indicated when tremor interferes with daily activities, work, or social life. Many patients with mild tremor may not require medication.

A. Lifestyle and Non-Pharmacological Measures

  • Avoid caffeine, stimulants, nicotine.

  • Reduce stress, practice relaxation techniques.

  • Limit medications that worsen tremor (e.g., bronchodilators, SSRIs, lithium).

  • Small amounts of alcohol may temporarily reduce tremor, but not recommended as therapy.

  • Occupational therapy: weighted utensils, special pens, wrist weights.

B. Pharmacological Therapy

1. First-Line Agents

  • Propranolol (non-selective beta-blocker):

    • Starting dose: 40 mg orally twice daily.

    • Usual effective dose: 120–320 mg/day in divided doses.

    • Contraindications: asthma, COPD, heart block, severe bradycardia.

  • Primidone (barbiturate anticonvulsant):

    • Start: 12.5–25 mg orally at bedtime.

    • Gradually increase to 250 mg twice daily (max 750 mg/day).

    • Side effects: sedation, nausea, dizziness, ataxia.

2. Alternatives / Adjuncts

  • Topiramate: 25–50 mg orally once daily, titrated up to 100–400 mg/day.

  • Gabapentin: 300 mg orally three times daily, up to 1200–1800 mg/day.

  • Alprazolam (benzodiazepine): 0.25–0.5 mg orally up to 3 times daily (for anxiety-related exacerbation, short-term use).

  • Clonazepam: 0.5–1 mg orally two to three times daily.

3. Botulinum Toxin Injections

  • Useful for head tremor and voice tremor.

  • OnabotulinumtoxinA: 25–75 units injected into affected muscles.

  • Risk: muscle weakness, dysphagia (if injected near throat).

C. Surgical and Device-Based Therapy

Reserved for severe, drug-resistant tremor.

  1. Deep Brain Stimulation (DBS):

    • Electrode implantation in ventral intermediate (VIM) nucleus of thalamus.

    • Highly effective, reversible, adjustable.

  2. Thalamotomy (radiofrequency or MR-guided focused ultrasound):

    • Lesion in VIM nucleus reduces tremor.

    • Effective but irreversible, potential side effects (weakness, speech disturbance).

Complications

  • Disability in eating, writing, dressing.

  • Psychological distress, social anxiety, depression.

  • Risk of injury due to impaired motor control.

  • Adverse effects of long-term medications (sedation, cognitive impairment, bradycardia).

Prognosis

  • Slowly progressive but not life-threatening.

  • Tremor amplitude may increase with age, but many patients remain functional with treatment.

  • Quality of life significantly improves with pharmacological or surgical therapy.

Patient Education

  • Essential tremor is not Parkinson’s disease.

  • Avoid triggers: caffeine, stress, fatigue.

  • Medications provide partial relief, not cure.

  • Lifestyle modifications and adaptive devices are valuable.

  • Consider early specialist referral for severe or disabling tremor.




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