Summary

Essential Tremor (ET) is the most common movement disorder worldwide, affecting approximately 5% of the population over 65 years. Unlike the resting tremor of Parkinson's Disease, ET is an Action Tremor (Kinetic and Postural) that manifests during voluntary movement. It typically affects the hands (90%), head (30%), and voice (20%), often causing significant functional disability (eating, writing, drinking). The "Benign" Misnomer: Historically called "Benign Essential Tremor", this term is outdated. The condition causes profound psychosocial embarrassment, functional impairment, and anxiety. Alcohol Responsiveness: A hallmark feature is the dramatic reduction of tremor with alcohol ingestion, a key diagnostic clue but also a risk factor for secondary alcoholism.

Key Facts

Clinical Pearls

"The Family Shake": ALWAYS ask about family history. "Does your dad have shaky hands?" is often more revealing than "Is there a family history of neurological disease?".

"The Sherry Sign": If a patient says "I have a glass of sherry before I sign a cheque", it is almost certainly Essential Tremor. Parkinson's tremor does not respond nearly as well to alcohol.

"No Legs Allowed": ET rarely affects the legs. Leg tremor is Parkinson's until proven otherwise.

"The Voice": A wavering voice (Tremulous speech) is common in ET. In Parkinson's, the voice is quiet (Hypophonia) and monotone.

The Cerebello-Thalamo-Cortical Loop

Unlike Parkinson's (which is a dopamine deficiency in the Basal Ganglia), Essential Tremor is a disorder of the Cerebellum and its connections.

Mechanism:

1. The Pacemaker: Abnormal oscillating neurons in the Inferior Olive (Brainstem).
2. The Amplifier: These oscillations travel to the Cerebellum (Purkinje Cells).
3. The Relay: The signal is projected to the Thalamus (VIM Nucleus).
4. The Output: The Thalamus excites the Motor Cortex, sending rhythmic tremors to the muscles.

Neurodegeneration?

• Historically considered "functional".
• Post-mortem studies show:
  • Loss of Purkinje Cells in the cerebellum.
  • Torpedo Bodies (Swellings on Purkinje cell axons).
  • This suggests ET is actually a neurodegenerative disease of the cerebellum.

GABA Dysfunction

• The system lacks inhibition.
• Propranolol and Primidone likely work by dampening this overactive loop.
• Alcohol acts as a GABA agonist, restoring inhibition (hence the dramatic response).

1. The Tremor Characteristics

• Action Tremor: Absent at rest. Appears with posture (arms out) or kinetic movement (drinking).
• Frequency: 4–12 Hz. (Slightly faster than Parkinson's).
• Symmetry: Bilateral and Symmetrical (Start).
• Progression: Insidious. Starts in one hand but rapidly becomes bilateral. Worsens slowly over decades.

2. Anatomical Distribution

3. Aggravating & Relieving Factors

1. Parkinson's Disease (The Big One)

This is the main diagnostic challenge.

2. Dystonic Tremor

• Clue: Irregular, jerky.
• Null Point: There is a position where the tremor stops.
• Sensory Trick: Touching the chin/head stops the tremor ("Geste antagoniste").

3. Enhanced Physiological Tremor

• Clue: High frequency, low amplitude.
• Cause: Thyrotoxicosis, Anxiety, Hypoglycaemia, Salbutamol, Lithium, Caffeine.
• Test: Put a piece of paper on the hands (amplifies the shake).

4. Functional (Psychogenic) Tremor

• Clue: Variable frequency. Distractible (tremor changes if you ask them to tap the other hand). Abrupt onset.

1. Basic Screen (Rule Out Reversible Causes)

• TFTs: Exclude Hyperthyroidism.
• U&Es / LFTs: Exclude metabolic encephalopathy.
• Copper/Ceruloplasmin: Mandatory in anyone <40 years (Wilson's Disease).

2. DaT Scan (Dopamine Transporter SPECT)

• Indication: If clinical differentiation between ET and PD is difficult.
• Mechanism: Shows dopamine neurons in the Basal Ganglia.
• Result:
  • Essential Tremor: NORMAL ("Comma shape" preserved).
  • Parkinson's: ABNORMAL ("Full stop shape" - loss of putamen tail).

3. Structural Imaging (MRI Brain)

• Usually NOT needed unless: Unilateral, Rapid onset, or other cerebellar signs (Ataxia).

Only treat if the tremor is functionally disabling (spilling drinks, unable to write).

┌─────────────────────────────────────────────────────────────────────────────┐
│                    ESSENTIAL TREMOR MANAGEMENT                              │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│   IS IT DISABLING?                                                          │
│   • NO: Education, reassurance. Avoid caffeine.                             │
│   • YES: Pharmacotherapy.                                                   │
│   └─────────────────────────────────────────────────────────────────────┘   │
│                          ↓                                                  │
│   ┌─────────────────────────────────────────────────────────────────────┐   │
│   │                 1. FIRST LINE THERAPY                               │   │
│   │  **A. Propranolol (Beta-Blocker)**                                  │   │
│   │  • Mechanism: Peripheral beta-adrenergic blockade.                  │   │
│   │  • Effectiveness: Reduces amplitude by 50%.                         │   │
│   │  • C/I: Asthma.                                                     │   │
│   │                                                                     │   │
│   │  **B. Primidone (Barbiturate)**                                     │   │
│   │  • Mechanism: Unknown. Metabolised to Phenobarbitone.               │   │
│   │  • Effectiveness: Equal to Propranolol.                             │   │
│   │  • S/E: Sedation (start low/slow).                                  │   │
│   └─────────────────────────────────────────────────────────────────────┘   │
│                          ↓                                                  │
│   ┌─────────────────────────────────────────────────────────────────────┐   │
│   │                 2. SECOND LINE                                      │   │
│   │  • Gabapentin / Topiramate (Anti-epileptics).                       │   │
│   │  • Benzodiazepines (Clonazepam) - caution habituation.              │   │
│   └─────────────────────────────────────────────────────────────────────┘   │
│                          ↓                                                  │
│   ┌─────────────────────────────────────────────────────────────────────┐   │
│   │                 3. SURGICAL (Refractory/Severe)                     │   │
│   │  **A. Deep Brain Stimulation (DBS)**                                │   │
│   │  • Target: Vim Nucleus of Thalamus.                                 │   │
│   │  • Highly effective (>80% reduction).                               │   │
│   │                                                                     │   │
│   │  **B. Focused Ultrasound (Thalamotomy)**                            │   │
│   │  • Non-invasive MRI-guided thermal ablation of thalamus.            │   │
│   │  • Option for patients unfit for DBS.                               │   │
│   └─────────────────────────────────────────────────────────────────────┘   │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

Principles of Treatment

1. Treat Disability, Not the Tremor: If the patient is not bothered, No Treatment is the best option.
2. Start Low, Go Slow: Especially in the elderly (risk of bradycardia/falls).
3. Realistic Expectations: Drugs reduce tremor amplitude by ~50%. They do not cure it.

Management Algorithm Image

First Line: The "Big Two"

Propranolol and Primidone are equally effective. Choice depends on comorbidities.

1. Propranolol (Beta-Blocker)

• Mechanism: Blocks peripheral Beta-2 receptors on muscle spindles (reduces tremor amplification).
• Efficacy: 50-70% reduction in amplitude.
• Protocol:
  • Start: 10mg BD or 40mg OD (Long Acting).
  • Titrate: Increase every 3-7 days.
  • Target: 80-160mg daily (Slow Release preferred for compliance).
• Contraindications:
  • Asthma / COPD.
  • Bradycardia / Heart Block.
  • Diabetes (masks hypoglycaemia).
• Side Effects: Fatigue, Cold extremities, Erectile dysfunction, Nightmares.

2. Primidone (Barbiturate)

• Mechanism: Unknown. Metabolised to Phenobarbitone.
• Protocol (The "Quarter" Rule):
  • Day 1: 25mg (1/4 tablet) at night. Warn about acute sedation.
  • Week 2: 50mg.
  • Target: 250mg daily.
• Side Effects: Significant sedation (improves with time), Ataxia, Nausea.
• Use Case: Asthma patients where Propranolol is contraindicated.

Second Line Therapy

If monotherapy fails, Switch or Combine (Propranolol + Primidone).

3. Topiramate

• Type: Anti-epileptic.
• Dose: 25-400mg.
• Side Effects: Cognitive slowing ("Dopamax"), Weight loss, Paraesthesia, Kidney stones.

4. Gabapentin

• Dose: 1200-2400mg daily.
• Side Effects: Sedation, Weight gain.

Indicated for severe, disabling tremor failing adequate trials of medications.

1. Deep Brain Stimulation (DBS)

• Target: Ventral Intermediate Nucleus (VIM) of the Thalamus.
• Mechanism: High-frequency stimulation inhibits the abnormal thalamic oscillations.
• Efficacy: >80% reduction in limb tremor. The "Gold Standard" for severe ET.
• Pros: Adjustable, Reversible, Bilateral treatment possible.
• Cons: Infection, Leads breaking, Intracerebral haemorrhage (1%), Hardware maintenance.
• Image:

2. MR-Guided Focused Ultrasound (MRgFUS)

• Mechanism: Uses 1000s of ultrasound beams to thermally ablate (burn) a tiny lesion in the VIM Thalamus. No incision.
• Pros: Incisionless. Immediate result on the table.
• Cons: Permanent lesion (Not reversible). Usually Unilateral only (Bilateral ablation causes severe speech/balance issues).
• Indication: Older patients unfit for DBS surgery.

Exam-Focused Points

1. Alcohol Response: The classic exam clue. "He has a drink to steady his nerves".
2. Symmetry: ET is bilateral. PD is unilateral (initially).
3. Head Tremor: Common in ET ("Titubation"). Very rare in PD (PD affects chin/jaw, not whole head).
4. Propranolol: Check for asthma first.
5. Examination: Test with Arms Out (Postural) and Finger-Nose Test (Kinetic - tremor worsens as finger approaches nose).

Common Exam Scenarios

• Young man (25) with hand tremor. Dad has it too. Worse with coffee. (Familial Essential Tremor).
• Patient on Propranolol for tremor develops wheeze. (Stop beta blocker - induced asthma).
• Difference between PD and ET spiral? (Spiky vs Small).

Is it Parkinson's?

"No. This is a different condition called Essential Tremor. Parkinson's causes stiffness and slowness, whereas your condition is purely a shaking of the hands when you try to use them. It is often inherited."

Can it be cured?

"We cannot cure it, but we can dampen it down. Beta-blockers (the adrenaline blocking drugs) are very effective at reducing the shake to a manageable level."

Key Guidelines

Evidence-Based Recommendations

1. The Archimedes Spiral Test

• The Test: Ask the patient to draw a spiral on a piece of paper, starting from the centre, without resting their hand on the table.
• Interpretation:
  • Essential Tremor: The spiral is reasonably large (normal size) but the lines are Jagged/Tremulous. The axis of the tremor is often 11 o'clock to 5 o'clock.
  • Parkinson's Disease: The spiral is smooth but Tiny (Micrographia).
• Image:

2. Physical Exam Steps

1. Inspection: Look for head tremor (Titubation).
2. Arms Out (Postural): Ask patient to hold arms outstretched. Place a piece of paper on hands to amplify tremor.
3. Finger-Nose Test (Kinetic): Tremor worsens as the finger approaches the target ("Intention" component).
4. Tone: Evaluate for "Cogwheeling" (Parkinson's) vs Normal (ET).

3. Classic Viva Questions

• Q: How does Alcohol affect the tremor?
  • A: It significantly improves it in 50-70% of cases (GABA agonist).
• Q: What is the inheritance pattern?
  • A: Autosomal Dominant (>50% familial).
• Q: Name 3 reversible causes of enhanced physiological tremor.
  • A: Thyrotoxicosis, Anxiety, Hypoglycaemia, Caffeine, Salbutamol.

"Is it Parkinson's?"

"No. This is a condition called Essential Tremor. It is 10 times more common than Parkinson's. The key difference is that Parkinson's causes slowness and stiffness, whereas Essential Tremor is purely a shaking of the hands when you try to use them. It does not shorten your life expectancy."

"Will it get worse?"

"It typically gets worse very slowly over decades. It usually starts in one hand and spreads to the other. It may eventually affect your head or voice."

"Can we cure it?"

"We cannot cure it, but we can dampen it down. We use Beta-Blockers (drugs used for anxiety or heart issues) which can reduce the shake by about 50%."

Key Guidelines

Landmark Trials

• Gorman et al (1986): Demonstrated efficacy of Propranolol vs Placebo.
• Deuschl et al (2011): Large review comparing DBS vs Thalamotomy. DBS favored for bilateral safety.
• Elias et al (2016): NEJM trial establishing MR-guided Focused Ultrasound as effective (but unilateral).

12. Clinical Case Studies

Case 1: The "Nervous" Student

Presentation: A 22-year-old medical student presents with shaky hands. He is worried about his upcoming OSCEs. He notices it most when holding a coffee cup or typing. It improves after a few beers on Friday night. His father has "bad nerves". Examination:

• Rest: No tremor.
• Posture (Arms out): Fine, high-frequency tremor of both hands.
• Spiral Drawing: Jagged, normal size. Diagnosis: Familial Essential Tremor. Management: Reassurance. Trial of Propranolol 10mg PRN for anxiety-provoking situations (OSCEs).

Case 2: The "Spilling" Grandmother

Presentation: A 74-year-old lady is brought by her daughter. She has stopped eating out because she spills soup and tea. She has lost weight because "it's too hard to cook". She has a "nodding" head tremor. Examination:

• Significant bilateral kinetic tremor.
• Titubation (Head nod).
• No rigidity/bradykinesia. Management:
• Started on Primidone (as she has asthma).
• Titrated to 250mg OD.
• Occupational Health referral for weighted cutlery and non-spill cups.
• Result: Able to feed herself again.