Essential Tremor

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management

Definition

Essential tremor (ET) is a common movement disorder characterised by an involuntary, rhythmic tremor that typically affects the hands, head, or voice, and worsens with voluntary movement.

Aetiology

The exact cause of essential tremor is unknown, but it is believed to involve abnormal function in the cerebellum and related pathways.

1. Genetic Factors:

  • Strong familial predisposition (autosomal dominant inheritance in many cases).
  • Commonly referred to as "familial tremor" when inherited.

2. Neurophysiological Abnormalities:

  • Possible dysfunction in the cerebellum and thalamus.
  • Altered GABAergic neurotransmission may contribute to tremor generation.

Pathophysiology

  • Increased oscillatory activity in the thalamocortical circuit.
  • Abnormal cerebellar output affecting motor control.
  • GABAergic dysfunction contributing to lack of inhibitory control over movement.

Risk factors

  • Family history of essential tremor.
  • Advancing age (more common after 40 years).
  • Exposure to neurotoxins (e.g., lead, pesticides – possible but unproven).

Signs and symptoms

Core Features:

  • Action tremor: occurs during voluntary movement (e.g., holding a cup, writing).
  • Postural tremor: present when maintaining a position against gravity.
  • Symmetrical onset: usually affects both hands equally.
  • Head tremor: "Yes-yes" or "no-no" head movements.
  • Voice tremor: tremulous speech in some cases.

Distinguishing Features from Parkinson’s Disease:

  • Essential tremor is absent at rest but worsens with movement.
  • No bradykinesia, rigidity, or postural instability.
  • Tremor improves with alcohol in some cases.

Investigations

  • Clinical diagnosis: based on characteristic tremor features.
  • Neurological examination: excludes other movement disorders.
  • DaTSCAN (dopamine transporter scan): helps differentiate ET from Parkinson’s disease if uncertainty exists.
  • Thyroid function tests: rules out hyperthyroidism as a cause of tremor.
  • Serum copper and caeruloplasmin: to exclude Wilson’s disease in young patients.

Management

1. Lifestyle and Supportive Measures:

  • Avoidance of triggers such as caffeine and stress.
  • Alcohol may transiently reduce tremor but is not a treatment.
  • Adaptive devices (e.g., weighted utensils) for fine motor tasks.

2. Pharmacological Treatment:

First-Line Treatment:
  • Propranolol (beta-blocker): reduces tremor amplitude.
  • Primidone (anticonvulsant): effective in reducing tremor severity.
Alternative Treatments:
  • Topiramate: used in patients intolerant to propranolol or primidone.
  • Gabapentin: occasionally used for refractory cases.
  • Clonazepam: may be used in patients with significant anxiety-related tremor.

3. Advanced Treatment Options:

  • Deep brain stimulation (DBS): effective for severe, medication resistant tremor.
  • Focused ultrasound thalamotomy: a newer, non invasive procedure for disabling tremor.

4. Physiotherapy and Occupational Therapy:

  • Exercises to improve coordination and reduce functional disability.
  • Speech therapy if voice tremor affects communication.
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