Essential Tremor

1. Clinical Overview

Summary

Essential tremor (ET) is the most common movement disorder worldwide, with prevalence estimates ranging from 0.9% in the general population to 4.6-6.3% in individuals over 65 years of age. [1] Historically termed "benign essential tremor," this nomenclature has been abandoned as the condition causes significant functional disability, psychosocial impairment, and reduced quality of life. [2]

ET is characterized by an action tremor — specifically a kinetic and postural tremor that manifests during voluntary movement and sustained posture, contrasting sharply with the rest tremor of Parkinson's disease. The tremor predominantly affects the upper limbs (90-95% of cases), with variable involvement of the head (30-50%), voice (20-30%), and less commonly the legs (less than 5%) or trunk. [3]

The pathophysiology centres on dysfunction within the cerebello-thalamo-cortical circuit, with mounting evidence from post-mortem studies suggesting ET may be a neurodegenerative cerebellar disorder characterized by Purkinje cell loss and torpedo body formation. [4] This represents a paradigm shift from historical conceptualization of ET as a purely functional disorder.

Genetics play a substantial role, with greater than 50% of cases demonstrating familial aggregation consistent with autosomal dominant inheritance with variable penetrance. First-degree relatives have a 5-10 fold increased risk of developing ET. [5]

A pathognomonic clinical feature is the dramatic response to alcohol ingestion, with 50-75% of patients reporting marked tremor reduction following small amounts of ethanol — a response not seen in Parkinson's disease. [6] While clinically useful as a diagnostic clue, this response carries significant risk of developing alcohol dependence.

Treatment follows a stepwise approach: first-line therapy with propranolol or primidone achieves approximately 50% tremor amplitude reduction. Second-line agents include topiramate and gabapentin. For medically refractory, disabling tremor, surgical interventions including deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of the thalamus or MR-guided focused ultrasound (MRgFUS) thalamotomy offer highly effective options with tremor reduction exceeding 80%. [7,8]

Key Facts

Clinical Pearls

"The Family Shake": ALWAYS ask about family history using lay terminology — "Does your father or mother have shaky hands?" or "Does anyone in your family have a tremor?" This simple question is often more revealing than formal medical history and is positive in > 50% of cases.

"The Sherry Sign": If a patient reports taking a small alcoholic drink (sherry, whisky, beer) before social events to "steady the nerves" or before signing important documents, this strongly suggests essential tremor. Parkinson's tremor does NOT respond to alcohol. [6]

"No Legs Rule": Essential tremor rarely affects the legs. Leg tremor at rest is Parkinson's disease until proven otherwise. The anatomical distribution (arms > head > voice >> legs) is diagnostically useful.

"The Voice Difference": In essential tremor, voice involvement produces a tremulous, quivering quality from laryngeal muscle tremor. In Parkinson's disease, the voice is hypophonic (quiet) and monotonous. Listen carefully — the character is distinctly different.

"The Spiral Test": Ask the patient to draw an Archimedes spiral starting from the centre. In ET, the spiral is normal in size but with tremulous, jagged lines. In Parkinson's, the spiral is smooth but progressively smaller (micrographia). This simple bedside test is highly discriminating.

Why This Matters Clinically

Essential tremor is frequently misdiagnosed as Parkinson's disease or dismissed as "nerves," leading to delayed or inappropriate treatment. The key clinical decisions are:

1. Distinguishing ET from Parkinson's disease: This differentiation has profound prognostic and therapeutic implications. ET is a tremor-dominant disorder without the motor and non-motor progression of PD.

2. Identifying treatable causes: Before diagnosing ET, exclude enhanced physiological tremor from thyrotoxicosis, hypoglycaemia, or medications (salbutamol, lithium, valproate, caffeine).

3. Assessing disability: Treatment is indicated only when tremor causes functional disability. Many patients with mild ET require only reassurance.

4. Avoiding alcohol dependence: While alcohol responsiveness is diagnostically useful, patients must be counselled about the serious risk of alcohol dependence, which is increased 4-fold in ET. [6]

---

2. Epidemiology

Incidence and Prevalence

Essential tremor demonstrates strongly age-dependent prevalence, with marked increase in older populations.

Global Burden: ET is approximately 10 times more common than Parkinson's disease, making it the most prevalent movement disorder worldwide. [1]

Bimodal Age of Onset:

• Early-onset peak (15-25 years): Strong familial component, autosomal dominant pattern, often positive family history spanning multiple generations
• Late-onset peak (55-70 years): More often sporadic, sometimes termed "senile tremor," may represent distinct phenotype

Risk Factors

Genetic Epidemiology

ET demonstrates clear familial aggregation with evidence supporting autosomal dominant inheritance with variable penetrance:

• Family history positive: 50-70% of ET cases report affected first-degree relatives [5]
• Concordance in monozygotic twins: 60-90%
• Concordance in dizygotic twins: 27-40%
• Segregation analysis: Consistent with autosomal dominant inheritance

Identified genetic loci (ETM1, ETM2, ETM3) and candidate genes (LINGO1, SLC1A2) have been reported but explain only a small proportion of cases, suggesting genetic heterogeneity. [14]

---

3. Pathophysiology

The Oscillating Cerebello-Thalamo-Cortical Loop

Unlike Parkinson's disease (which results from dopaminergic neurodegeneration in the substantia nigra affecting basal ganglia circuits), essential tremor is fundamentally a cerebellar circuit disorder. [4]

Central Oscillator Model:

┌─────────────────────────────────────────────────────────────────────────┐
│             PATHOPHYSIOLOGICAL CIRCUIT OF ESSENTIAL TREMOR              │
├─────────────────────────────────────────────────────────────────────────┤
│                                                                         │
│  1. THE PACEMAKER: INFERIOR OLIVE (Brainstem)                          │
│     • Abnormal oscillating neurons (4-12 Hz)                           │
│     • Generates rhythmic signals that propagate through circuit        │
│     • Climbing fibers project to cerebellum                            │
│                           ↓                                            │
│  2. THE AMPLIFIER: CEREBELLUM (Purkinje Cells)                        │
│     • Receives oscillatory input via climbing fibers                   │
│     • Purkinje cell loss and torpedo bodies in post-mortem studies    │
│     • Reduced GABAergic inhibition amplifies oscillations              │
│                           ↓                                            │
│  3. THE RELAY: THALAMUS (VIM Nucleus)                                 │
│     • Deep cerebellar nuclei project to VIM (ventral intermediate)    │
│     • VIM acts as "gatekeeper" to motor cortex                        │
│     • Target for DBS and focused ultrasound ablation                  │
│                           ↓                                            │
│  4. THE OUTPUT: MOTOR CORTEX                                          │
│     • Receives oscillatory thalamic input                              │
│     • Generates rhythmic motor commands                                │
│     • Manifests as 4-12 Hz tremor during movement/posture             │
│                                                                         │
└─────────────────────────────────────────────────────────────────────────┘

Neurodegenerative Hypothesis

Post-mortem neuropathological studies have challenged the traditional view of ET as a purely functional disorder, revealing structural abnormalities in the cerebellum: [4]

These findings suggest ET may represent a neurodegenerative cerebellar disorder, though the relationship between pathology and clinical phenotype requires further investigation.

GABAergic Dysfunction

The GABAergic hypothesis provides a unifying framework explaining both pathophysiology and therapeutic responses: [15]

• Cerebellar GABA reduction: Post-mortem and neuroimaging studies demonstrate reduced cerebellar GABA levels
• Alcohol response: Ethanol is a positive allosteric modulator of GABA-A receptors, explaining dramatic tremor improvement
• Primidone mechanism: Metabolized to phenobarbital, a GABA-A receptor enhancer
• Benzodiazepine efficacy: GABA-A positive allosteric modulators (clonazepam) provide tremor relief

Why DBS Works

Deep brain stimulation of the VIM nucleus interrupts the oscillatory thalamo-cortical signal transmission:

• High-frequency stimulation (130-185 Hz) "jams" the pathological 4-12 Hz tremor rhythm
• Does not destroy tissue — effects are reversible and adjustable
• VIM is the "bottleneck" where cerebellar output converges before reaching motor cortex

---

4. Clinical Presentation

Core Tremor Characteristics

The hallmark of essential tremor is an action tremor with the following defining features:

Anatomical Distribution

Modifying Factors

Functional Impact Assessment

Essential tremor causes significant functional disability that correlates poorly with tremor amplitude. Assess specific activities:

Activities of Daily Living Affected:

• Handwriting (illegible, embarrassing)
• Drinking from cups (spilling, uses covered containers)
• Eating soup (spilling, avoids in public)
• Buttoning clothes
• Applying makeup/shaving
• Using keys and touchscreens
• Typing and computer use

Social and Occupational Impact:

• Public embarrassment leading to social withdrawal
• Difficulty with precision occupations (surgery, dentistry, watchmaking)
• Avoidance of restaurants and public eating
• Depression and anxiety (20-40% prevalence)
• Alcohol misuse for self-medication (4-fold increased risk) [6]

Associated Non-Motor Features

Emerging evidence suggests ET may be associated with non-motor features: [16]

These features suggest ET may represent a more widespread neurological disorder than previously recognised, though this remains controversial.

---

5. Differential Diagnosis

Essential Tremor vs Parkinson's Disease — The Critical Distinction

This is the most important differential diagnosis in clinical practice. Misdiagnosis leads to inappropriate treatment and unnecessary prognostic anxiety.

Other Differential Diagnoses

1. Enhanced Physiological Tremor

• High frequency (8-12 Hz), low amplitude, fine tremor
• Causes: thyrotoxicosis, anxiety, hypoglycaemia, pheochromocytoma, caffeine, salbutamol, lithium, valproate, SSRIs, cocaine
• Diagnosis: Identify and treat underlying cause; thyroid function tests essential
• Paper test: Place paper on outstretched hands — amplifies visible tremor

2. Dystonic Tremor

• Irregular, jerky tremor with variable amplitude and frequency
• "Null point": Position where tremor diminishes or disappears
• "Geste antagoniste": Sensory trick (touching chin, head) reduces tremor
• Often associated with subtle dystonic posturing
• May be indistinguishable from ET in early stages

3. Drug-Induced Tremor

• Common culprits: valproate, lithium, amiodarone, tacrolimus, beta-agonists, SSRIs
• Temporal relationship to medication initiation
• Improves with dose reduction or discontinuation

4. Orthostatic Tremor

• High-frequency (13-18 Hz) tremor of legs on standing
• Patients report unsteadiness rather than visible tremor
• Relieved by walking or sitting; surface EMG diagnostic

5. Wilson's Disease

• MUST exclude in any patient less than 40 years with tremor
• Associated features: hepatic dysfunction, Kayser-Fleischer rings, psychiatric symptoms
• Screen: serum ceruloplasmin (low), 24-hour urinary copper (elevated), slit-lamp examination

6. Functional (Psychogenic) Tremor

• Variable frequency and amplitude
• Distractibility: Tremor frequency entrains or is suppressed by contralateral rhythmic movement
• Abrupt onset and remission
• Inconsistent features over time
• Positive signs (entrainment, co-activation sign) more reliable than negative signs

---

6. Investigations Strategy

Approach to Investigation

Essential tremor is primarily a clinical diagnosis. Investigations serve to:

1. Exclude treatable causes of enhanced physiological tremor
2. Distinguish ET from Parkinson's disease when clinical uncertainty exists
3. Screen for Wilson's disease in appropriate patients

Tier 1: Basic Screening (All Patients)

Tier 2: Additional Investigations (Selected Patients)

Tier 3: Specialised Investigations (Diagnostic Uncertainty)

DaTscan (Dopamine Transporter SPECT Imaging) [17]

• Indication: Clinical distinction between ET and Parkinson's disease is difficult
• Mechanism: Radiolabelled ligand (Ioflupane I-123) binds presynaptic dopamine transporters in striatum
• Interpretation:
  • "Essential Tremor: NORMAL — comma-shaped striatal uptake preserved"
  • Parkinson's Disease: ABNORMAL — reduced putaminal uptake ("full-stop" appearance)
• Sensitivity/Specificity: 78-98% sensitivity and 80-100% specificity for distinguishing degenerative parkinsonism from non-degenerative tremor
• Limitations: Cannot distinguish between different parkinsonian syndromes (PD vs MSA vs PSP)
• Cost-effectiveness: Reserve for cases with genuine diagnostic uncertainty

Electromyography (EMG) with Accelerometry

• Quantifies tremor frequency and pattern
• Differentiates ET (6-12 Hz) from orthostatic tremor (13-18 Hz)
• Research tool; rarely needed clinically

Investigation Algorithm

┌─────────────────────────────────────────────────────────────────────────┐
│                  INVESTIGATION PATHWAY FOR TREMOR                       │
├─────────────────────────────────────────────────────────────────────────┤
│                                                                         │
│  ALL PATIENTS WITH TREMOR                                              │
│  ├── Clinical history and examination                                  │
│  ├── TFTs (exclude hyperthyroidism)                                    │
│  ├── Glucose (exclude hypoglycaemia)                                   │
│  └── Medication review (exclude drug-induced)                          │
│                           │                                            │
│                           ▼                                            │
│  AGE less than 40 YEARS OR ATYPICAL FEATURES?                                  │
│  ├── YES → Ceruloplasmin, 24h urinary copper, slit-lamp exam         │
│  │         (Wilson's disease screen)                                   │
│  └── NO → Proceed to clinical diagnosis                               │
│                           │                                            │
│                           ▼                                            │
│  CLINICAL UNCERTAINTY: ET vs PARKINSON'S?                             │
│  ├── YES → DaTscan (dopamine transporter SPECT)                       │
│  │         Normal = ET; Abnormal = Parkinsonism                       │
│  └── NO → Clinical diagnosis of ET                                    │
│                           │                                            │
│                           ▼                                            │
│  ATYPICAL PROGRESSION OR FOCAL SIGNS?                                 │
│  ├── YES → MRI brain (exclude structural lesion)                      │
│  └── NO → Initiate treatment if disabling                             │
│                                                                         │
└─────────────────────────────────────────────────────────────────────────┘

---

7. Management Strategy

Treatment Principles

1. Treat disability, not the tremor: If the patient is not functionally impaired, treatment is NOT indicated
2. Set realistic expectations: Pharmacotherapy reduces tremor amplitude by approximately 50% — it does NOT cure the tremor
3. Start low, go slow: Especially in elderly patients at risk of bradycardia and falls
4. Avoid alcohol dependence: Counsel all patients about the 4-fold increased risk
5. Consider occupational therapy: Adaptive devices can be transformative
6. Reserve surgery for refractory cases: DBS and FUS are highly effective but invasive

Management Algorithm

┌─────────────────────────────────────────────────────────────────────────┐
│                    ESSENTIAL TREMOR MANAGEMENT                          │
├─────────────────────────────────────────────────────────────────────────┤
│                                                                         │
│  STEP 1: ASSESS DISABILITY                                             │
│  ├── Mild/Not disabling → Education, reassurance, avoid caffeine      │
│  │                        Occupational therapy, adaptive devices       │
│  └── Moderate-Severe/Disabling → Proceed to pharmacotherapy           │
│                           │                                            │
│                           ▼                                            │
│  STEP 2: FIRST-LINE PHARMACOTHERAPY                                   │
│  ┌─────────────────────────────────────────────────────────────────┐  │
│  │  Option A: PROPRANOLOL (if no asthma/bradycardia)               │  │
│  │  • Start 40mg BD or 60mg LA OD                                  │  │
│  │  • Titrate to 120-240mg/day (max 320mg)                        │  │
│  │  • 50-70% tremor reduction in responders [10]                  │  │
│  │                                                                 │  │
│  │  Option B: PRIMIDONE (if beta-blocker contraindicated)         │  │
│  │  • Start 12.5-25mg nocte (quarter tablet)                      │  │
│  │  • Titrate slowly over weeks to 250-750mg/day                  │  │
│  │  • WARN about first-dose sedation/nausea [10]                  │  │
│  │                                                                 │  │
│  │  Option C: COMBINATION (Propranolol + Primidone)               │  │
│  │  • If monotherapy inadequate, combine both                      │  │
│  └─────────────────────────────────────────────────────────────────┘  │
│                           │                                            │
│                           ▼                                            │
│  STEP 3: SECOND-LINE PHARMACOTHERAPY (if first-line inadequate)      │
│  ├── Topiramate 25-400mg/day (cognitive effects, weight loss)        │
│  ├── Gabapentin 1200-3600mg/day (sedation)                           │
│  ├── Alprazolam 0.25-3mg/day (short-term; dependence risk)           │
│  └── Clonazepam 0.5-4mg/day (sedation; dependence risk)              │
│                           │                                            │
│                           ▼                                            │
│  STEP 4: SURGICAL INTERVENTION (Refractory, disabling tremor)        │
│  ├── Deep Brain Stimulation (VIM nucleus) — GOLD STANDARD            │
│  │   • Reversible, adjustable, bilateral treatment possible          │
│  │   • > 80% tremor reduction [7]                                     │
│  │                                                                    │
│  └── MR-guided Focused Ultrasound Thalamotomy                        │
│      • Incisionless; immediate effect on table                       │
│      • Unilateral only (bilateral → speech/balance issues) [8]       │
│      • Suitable for DBS-ineligible patients                          │
│                                                                         │
└─────────────────────────────────────────────────────────────────────────┘

---

8. Pharmacotherapy Protocols

First-Line Agents — The "Big Two"

1. Propranolol (Non-selective Beta-Blocker)

Mechanism: Blocks peripheral β2-adrenergic receptors on muscle spindles, reducing tremor amplification. Some central effect may also contribute. [10]

Evidence: Level A recommendation (AAN 2011/2022) — established efficacy from multiple Class I studies

Protocol:

Contraindications:

• Asthma or COPD (bronchospasm risk)
• Bradycardia (less than 50 bpm) or heart block (2nd/3rd degree)
• Decompensated heart failure
• Severe peripheral vascular disease
• Phaeochromocytoma (without alpha-blockade)

Cautions: Diabetes (masks hypoglycaemia symptoms), depression, Raynaud's phenomenon

Side Effects:

• Fatigue and lethargy
• Cold extremities
• Bradycardia and hypotension
• Erectile dysfunction
• Vivid dreams/nightmares
• Sleep disturbance
• Bronchospasm (even in "mild" respiratory disease)

2. Primidone (Barbiturate Pro-Drug)

Mechanism: Metabolized to phenobarbitone; mechanism in ET unclear but likely GABA-A enhancement

Evidence: Level A recommendation (AAN 2011/2022) — equally effective as propranolol

Protocol — "The Quarter Rule":

First-Dose Phenomenon: Up to 25% of patients experience severe nausea, sedation, and ataxia with the first dose ("primidone sensitivity"). This is idiosyncratic, unpredictable, and NOT dose-related. Advise:

• Take first dose at bedtime
• Have someone available next morning
• Start with lowest possible dose (quarter tablet)
• If tolerated, subsequent doses much better tolerated

Contraindications: Porphyria, severe respiratory disease, hepatic impairment

Side Effects:

• Sedation (usually improves with time)
• Cognitive slowing
• Ataxia
• Nausea
• Depression
• Rash

Use Case: Preferred when propranolol contraindicated (asthma, bradycardia)

Combination Therapy

If monotherapy with propranolol OR primidone provides partial but inadequate response:

• Combine propranolol + primidone — additive effect in many patients
• Dose each at lower end of range when combining
• Monitor for cumulative side effects

Second-Line Agents

Topiramate [18]

Gabapentin [18]

Benzodiazepines (Clonazepam, Alprazolam)

• Reserve for short-term use or when other agents fail
• Dependence and tolerance are significant concerns
• May be useful for performance anxiety exacerbating tremor
• Clonazepam 0.5-4mg/day; Alprazolam 0.25-3mg/day

Botulinum Toxin

Indication: Refractory head or voice tremor; focal limb tremor

---

9. Surgical Interventions

For patients with medically refractory, severely disabling tremor despite adequate trials of pharmacotherapy, surgical intervention offers highly effective options. [7,8]

1. Deep Brain Stimulation (DBS) — The Gold Standard

Target: Ventral Intermediate Nucleus (VIM) of the thalamus

Mechanism: High-frequency electrical stimulation (130-185 Hz) disrupts pathological oscillatory activity in the thalamus, "jamming" the 4-12 Hz tremor signal before it reaches motor cortex

Efficacy:

• > 80% tremor reduction in controlled studies [7]
• Benefits sustained at 5-10 year follow-up
• Improvement in quality of life and functional disability

Advantages:

• Adjustable and reversible
• Bilateral treatment possible (lower risk than bilateral ablation)
• Long-term efficacy proven
• Does not preclude future treatments

Risks:

Patient Selection:

• Medically refractory disabling tremor
• Adequate trial of first-line agents (propranolol AND primidone)
• Cognitively intact (able to participate in programming)
• Life expectancy > 5 years
• Medically fit for surgery
• Realistic expectations

2. MR-Guided Focused Ultrasound (MRgFUS) Thalamotomy

Mechanism: Uses > 1000 converging ultrasound beams to create a precise thermal ablation lesion in the VIM thalamus. No incision required. [8]

Procedure:

• Patient awake in MRI scanner wearing stereotactic frame
• Real-time MRI thermometry monitors ablation
• Progressive lesioning with immediate tremor assessment
• Typically 2-3 hour procedure

Efficacy: Comparable to DBS — approximately 60-80% tremor reduction at 1 year [8]

Advantages:

• No surgical incision or anaesthesia
• No implanted hardware
• No infection or hardware failure risk
• Immediate effect

Disadvantages:

• Unilateral only (bilateral → 25-30% risk severe dysarthria/dysphagia)
• Permanent and irreversible
• Not adjustable
• Requires skull density ratio compatible with ultrasound transmission
• Limited long-term follow-up data
• Less experience than DBS

Complications:

Ideal Candidate for MRgFUS:

• Unilateral dominant hand tremor
• Contraindication to surgery/anaesthesia
• Patient preference for non-invasive approach
• Not candidate for DBS (anticoagulation, pacemaker, infection risk)
• Older patient with limited life expectancy

Surgical Decision Algorithm

┌─────────────────────────────────────────────────────────────────────────┐
│               SURGICAL INTERVENTION DECISION PATHWAY                    │
├─────────────────────────────────────────────────────────────────────────┤
│                                                                         │
│  PREREQUISITES MET?                                                     │
│  ├── Failed propranolol AND primidone at adequate doses                │
│  ├── Severely disabling tremor affecting quality of life               │
│  ├── No untreated psychiatric disease                                  │
│  └── Cognitively intact with realistic expectations                    │
│                           │                                            │
│                           ▼                                            │
│  BILATERAL TREATMENT NEEDED?                                           │
│  ├── YES → Deep Brain Stimulation (DBS) preferred                     │
│  │         • Bilateral VIM DBS possible (staged)                       │
│  │         • Adjustable and reversible                                 │
│  │                                                                     │
│  └── NO (Unilateral dominant hand tremor)                             │
│      │                                                                 │
│      ▼                                                                 │
│      SURGICAL CANDIDATE?                                               │
│      ├── YES → DBS (gold standard) OR MRgFUS (if preferred)          │
│      │                                                                 │
│      └── NO (anticoagulation, high surgical risk)                     │
│          → MRgFUS thalamotomy (incisionless option)                   │
│                                                                         │
└─────────────────────────────────────────────────────────────────────────┘

---

10. Examination Technique

Systematic Approach to Tremor Examination

1. Observation at Rest

• Ask patient to sit with hands relaxed in lap
• Observe for tremor at rest (suggests PD, not ET)
• Note any facial masking, reduced blink rate (PD features)

2. Postural Tremor Assessment

• Ask patient to hold arms outstretched in front with palms down
• Hold for 20-30 seconds
• Place paper on dorsum of hands to amplify visible tremor
• Note frequency, amplitude, symmetry

3. Kinetic Tremor Assessment — Finger-Nose Test

• Standard finger-nose-finger test
• Observe tremor during movement
• Note if tremor worsens approaching target (intention component)
• Compare right and left sides

4. Spiral Drawing Test (Archimedes Spiral)

This is the single most discriminating bedside test:

Technique:

• Give patient unlined paper and pen
• Ask to draw a spiral starting from centre, spiralling outward
• Hand must NOT rest on table (arm unsupported)
• Draw slowly and carefully

Interpretation:

5. Head Tremor Assessment

• Observe head position and any titubation
• "Yes-yes" (vertical) vs "no-no" (horizontal) head tremor
• Test for dystonic features: Ask patient to rotate head — does tremor change?

6. Voice Assessment

• Ask patient to sustain "aaah" for 10 seconds
• Listen for tremulous, wavering quality (ET)
• Compare to hypophonic, monotonous voice (PD)

7. Tone Assessment

• Assess tone at wrist and elbow
• Normal tone in ET
• Rigidity (lead-pipe or cogwheel) suggests PD

8. Bradykinesia Assessment

• Finger tapping: Ask patient to tap thumb and index finger rapidly
• Hand opening/closing
• Foot tapping
• Look for progressive reduction in amplitude and speed (decrement) — hallmark of PD

9. Gait Assessment

• Observe patient walking
• Normal in ET
• Reduced arm swing, shuffling, festination, turning en bloc suggest PD

Documentation Example

"Examination reveals a bilateral, symmetric, action tremor of the upper limbs, most prominent with arms outstretched (postural component) and during finger-nose testing (kinetic component). Tremor frequency approximately 6 Hz with moderate amplitude. No tremor at complete rest. Spiral drawing shows tremulous lines with preserved size. Mild head titubation present with 'no-no' quality. Tone is normal bilaterally without cogwheeling. No bradykinesia on repeated finger tapping. Gait normal with preserved arm swing. No Parkinsonian features identified. Findings consistent with essential tremor."

---

11. Examination Focus (OSCEs & Vivas)

Classic OSCE Scenarios

Scenario 1: "The Medical Student with Shaky Hands"

• 24-year-old medical student worried about tremor during clinical skills
• Tremor worse with stress, coffee, and during examinations
• Father has "shaky hands"
• Key findings: Bilateral postural/kinetic tremor, tremulous spiral, normal tone
• Diagnosis: Essential tremor (familial, early-onset)
• Management: Reassurance +/- propranolol PRN for high-stress situations

Scenario 2: "The Spilling Grandmother"

• 72-year-old woman has stopped eating in public — "too embarrassing"
• Progressive tremor over 20 years
• Dramatic improvement with small glass of sherry
• Associated head tremor
• Key findings: Marked kinetic tremor, head titubation, normal tone/gait
• Diagnosis: Essential tremor
• Management: Primidone (asthma history precludes propranolol), OT referral for weighted cutlery

Scenario 3: "ET or PD?"

• 68-year-old man with right hand tremor
• Examiner asks you to differentiate
• Key discriminators: Rest vs action tremor, micrographia vs tremography, rigidity, bradykinesia, gait
• Investigation: DaTscan if uncertain

Viva Questions with Model Answers

Q1: How do you differentiate Essential Tremor from Parkinson's Disease clinically?

"The key differentiating features are: First, tremor type — ET is an action tremor appearing with posture and kinetic movement, while PD is a rest tremor that diminishes with action. Second, symmetry — ET typically affects both hands relatively symmetrically, while PD classically starts unilaterally. Third, associated features — ET has no rigidity or bradykinesia, whereas PD demonstrates cogwheel rigidity and progressive slowing on repeated movements. Fourth, anatomical distribution — head tremor and leg sparing favour ET; leg involvement and chin tremor suggest PD. Fifth, handwriting — ET produces large tremulous writing; PD causes progressively smaller micrographia. Finally, alcohol response — ET characteristically improves with alcohol; PD does not."

Q2: What is the inheritance pattern of Essential Tremor?

"Essential tremor demonstrates autosomal dominant inheritance with variable penetrance in approximately 50-70% of cases. First-degree relatives of affected individuals have a 5-10 fold increased risk of developing ET. Several genetic loci (ETM1, ETM2, ETM3) and candidate genes including LINGO1 have been identified, but these explain only a small proportion of familial cases, suggesting significant genetic heterogeneity."

Q3: A 32-year-old presents with action tremor. What must you exclude?

"In any patient under 40 years presenting with tremor, I must exclude Wilson's disease — this is a treatable condition that is fatal if missed. I would check serum ceruloplasmin, 24-hour urinary copper, and arrange slit-lamp examination for Kayser-Fleischer rings. Additionally, I would screen for hyperthyroidism with thyroid function tests and take a thorough drug history to exclude drug-induced tremor."

Q4: What are the first-line treatments for Essential Tremor?

"First-line treatments are propranolol and primidone, both with Level A evidence from the AAN guidelines. Propranolol is started at 40mg twice daily and titrated to 120-240mg daily. It is contraindicated in asthma and bradycardia. Primidone is started at a very low dose — 12.5-25mg at night — due to the first-dose phenomenon causing severe sedation and nausea. It is titrated slowly to 250-750mg daily. Both achieve approximately 50% tremor amplitude reduction. If monotherapy fails, the two can be combined with additive effect."

Q5: When would you consider Deep Brain Stimulation?

"I would consider DBS for patients with severely disabling tremor that significantly impairs quality of life, who have failed adequate trials of both propranolol and primidone at therapeutic doses. Prerequisites include intact cognition, realistic expectations, medical fitness for surgery, and the absence of untreated psychiatric disease. DBS of the VIM nucleus achieves greater than 80% tremor reduction in appropriately selected patients, is adjustable and reversible, and allows bilateral treatment. The main alternative is MR-guided focused ultrasound, which is incisionless but permanent, irreversible, and limited to unilateral treatment."

---

12. Prognosis and Long-Term Outcomes

Natural History

Quality of Life Impact

ET significantly impairs quality of life, comparable to other chronic neurological conditions:

• Physical function: Difficulty with writing, eating, drinking, dressing
• Employment: May preclude precision occupations
• Social function: Embarrassment, social withdrawal, avoidance of public eating
• Psychological: Depression (20-30%), anxiety (25-40%)
• Alcohol dependence: 4-fold increased risk due to self-medication [6]

Predictors of Disability

---

13. Patient Education

Common Patient Questions

"Is this Parkinson's disease?"

"No, this is essential tremor — a different condition entirely. While both cause tremor, essential tremor affects your hands when you use them (during movement), whereas Parkinson's causes shaking when your hands are resting. Parkinson's also causes stiffness and slowness that essential tremor does not. Importantly, essential tremor does NOT turn into Parkinson's disease, and unlike Parkinson's, it does not affect your life expectancy."

"Will it get worse?"

"Essential tremor typically progresses slowly over many years or decades. The shaking may gradually increase in amplitude and may spread to involve your head or voice in some cases. However, the rate of progression is very variable — some people notice little change over many years, while others experience more noticeable worsening. The good news is that effective treatments are available at every stage."

"Can it be cured?"

"Currently we cannot cure essential tremor, but we can effectively control it. Medications such as propranolol or primidone typically reduce tremor by about half in people who respond. For those with severe tremor not responding to medications, surgical treatments including deep brain stimulation can reduce tremor by 80% or more. Research into new treatments continues."

"Why does alcohol help?"

"Alcohol works on a brain chemical called GABA, which has a calming effect on the brain circuits involved in tremor. This is why a small drink can dramatically reduce your tremor. However, it's very important not to rely on alcohol for tremor control — people with essential tremor have a four times higher risk of developing alcohol dependence. We have medications that work in similar ways without the addiction risk."

"Is it hereditary?"

"Essential tremor runs in families in about half of cases. If you have essential tremor, there is approximately a 50% chance that each of your children could develop it at some point in their lives — though this varies considerably. Having the genetic tendency doesn't mean someone will definitely develop tremor, and even if they do, it may remain mild."

Practical Advice for Patients

Lifestyle Modifications:

• Minimise caffeine intake (worsens tremor)
• Ensure adequate sleep (fatigue exacerbates tremor)
• Avoid alcohol as a tremor remedy (dependence risk)
• Plan challenging tasks for times when tremor is least severe
• Use stress-reduction techniques (anxiety worsens tremor)

Adaptive Strategies and Devices:

• Weighted pens and utensils (dampen tremor)
• Two-handled cups and non-spill mugs
• Electric razors instead of manual
• Voice-to-text software for writing
• Button hooks and Velcro clothing modifications
• Wrist weights (some patients find helpful)

Occupational Therapy Referral: OT assessment can be transformative, providing:

• Functional assessment of activities of daily living
• Appropriate adaptive equipment prescription
• Task modification strategies
• Workstation and home modifications
• Liaison with employers for workplace adjustments

---

14. Clinical Case Studies

Case 1: Classic Familial Essential Tremor

Presentation: A 28-year-old software engineer presents with bilateral hand tremor first noticed 5 years ago. The tremor is embarrassing during presentations and when drinking coffee with colleagues. His father and paternal grandmother have "shaky hands."

History:

• Tremor absent at rest, appears when typing or holding objects
• Notably improved after a glass of wine at social events
• No other neurological symptoms
• Tremor worsened by caffeine and stress

Examination:

• Bilateral symmetric 6 Hz postural and kinetic tremor
• Spiral drawing: Normal size with tremulous lines
• Finger-nose: Tremor throughout, worse approaching target
• No head or voice tremor
• Tone: Normal
• Gait: Normal

Investigations:

• TFTs: Normal
• Clinical diagnosis; no DaTscan needed

Management:

1. Reassurance — not Parkinson's, normal life expectancy
2. Reduce caffeine intake
3. Trial propranolol 40mg BD → titrated to 80mg LA OD
4. PRN propranolol 10-20mg before presentations
5. Result: 50% tremor reduction; significant functional improvement

Follow-up: Well-controlled on propranolol 120mg LA. Continues working successfully as engineer.

Case 2: Elderly Patient with Disabling Tremor

Presentation: A 76-year-old retired teacher has stopped eating in restaurants due to embarrassment from spilling food. Her daughter is concerned about weight loss. Tremor progressive over 30 years.

History:

• Severe bilateral hand tremor with head involvement
• "Has a sherry before dinner to steady hands"
• Mother had similar tremor
• Also has well-controlled asthma

Examination:

• Coarse bilateral kinetic tremor (4-5 Hz)
• Marked head tremor ("no-no" pattern)
• Tremulous voice
• Spiral: Tremulous, preserved size
• Normal tone and gait

Management:

1. Cannot use propranolol (asthma)
2. Started primidone 12.5mg nocte with clear warning about first-dose effect
3. Tolerated well; titrated to 250mg OD over 6 weeks
4. Occupational therapy: Weighted utensils, non-spill cup
5. Nutritional support

Outcome: 40% tremor reduction; now eating at daughter's home; improved nutrition.

Case 3: Diagnostic Uncertainty — ET vs PD

Presentation: A 64-year-old accountant with 2-year history of right hand tremor. Referred by GP who is "not sure if this is ET or Parkinson's."

Key Discriminating Features:

Investigation: DaTscan ordered due to diagnostic uncertainty

Result: Abnormal — reduced left putaminal uptake consistent with right-sided parkinsonism

Diagnosis: Early Parkinson's disease (NOT essential tremor)

Learning Point: The combination of asymmetric rest tremor, micrographia, subtle rigidity, and bradykinesia points toward PD. DaTscan confirmed the clinical suspicion and altered prognosis and treatment planning.

---

15. Evidence and Guidelines

Major Guidelines

Landmark Studies

Evidence Levels for Treatments

---

16. References

1. Louis ED, Ferreira JJ. How common is the most common adult movement disorder? Update on the worldwide prevalence of essential tremor. Mov Disord. 2010;25(5):534-541. doi:10.1002/mds.22838

2. Lorenz D, Deuschl G. Update on pathogenesis and treatment of essential tremor. Curr Opin Neurol. 2007;20(4):447-452. doi:10.1097/WCO.0b013e3281e66942

3. Elble RJ. Essential tremor frequency decreases with time. Neurology. 2000;55(10):1547-1551. doi:10.1212/WNL.55.10.1547

4. Louis ED, Faust PL, Vonsattel JP, et al. Neuropathological changes in essential tremor: 33 cases compared with 21 controls. Brain. 2007;130(Pt 12):3297-3307. doi:10.1093/brain/awm266

5. Bain PG, Findley LJ, Thompson PD, et al. A study of hereditary essential tremor. Brain. 1994;117(Pt 4):805-824. doi:10.1093/brain/117.4.805

6. Hopfner F, Deuschl G. Is essential tremor a single entity? Eur J Neurol. 2018;25(1):71-82. doi:10.1111/ene.13454

7. Schuurman PR, Bosch DA, Bossuyt PM, et al. A comparison of continuous thalamic stimulation and thalamotomy for suppression of severe tremor. N Engl J Med. 2000;342(7):461-468. doi:10.1056/NEJM200002173420703

8. Elias WJ, Lipsman N, Ondo WG, et al. A randomized trial of focused ultrasound thalamotomy for essential tremor. N Engl J Med. 2016;375(8):730-739. doi:10.1056/NEJMoa1600159

9. Deuschl G, Petersen I, Lorenz D, Christensen K. Tremor in the elderly: Essential and aging-related tremor. Mov Disord. 2015;30(10):1327-1334. doi:10.1002/mds.26265

10. Zesiewicz TA, Elble RJ, Louis ED, et al. Evidence-based guideline update: Treatment of essential tremor: Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2011;77(19):1752-1755. doi:10.1212/WNL.0b013e318236f0fd

11. Louis ED, Thawani SP, Andrews HF. Prevalence of essential tremor in a multiethnic, community-based study in northern Manhattan, New York, N.Y. Neuroepidemiology. 2009;32(3):208-214. doi:10.1159/000195691

12. Louis ED, Ford B, Frucht S, Barnes LF, X-Tang M, Ottman R. Risk of tremor and impairment from tremor in relatives of patients with essential tremor: A community-based family study. Ann Neurol. 2001;49(6):761-769. doi:10.1002/ana.1022

13. Louis ED, Zheng W, Applegate L, Shi L, Factor-Litvak P. Blood harmane concentrations and dietary protein consumption in essential tremor. Neurology. 2005;65(3):391-396. doi:10.1212/01.wnl.0000172352.88359.2d

14. Clark LN, Louis ED. Essential tremor. Handb Clin Neurol. 2018;147:229-239. doi:10.1016/B978-0-444-63233-3.00015-4

15. Paris-Robidas S, Bherer L, Bherer L, et al. GABAergic dysfunction in essential tremor: A review of the evidence. Tremor Other Hyperkinet Mov (N Y). 2020;10:30. doi:10.7916/tohm.v0.753

16. Jhunjhunwala K, Pal PK. The non-motor features of essential tremor: A primary disease feature or just a secondary phenomenon? Tremor Other Hyperkinet Mov (N Y). 2014;4:255. doi:10.7916/D8RF5S4J

17. Benamer TS, Patterson J, Grosset DG, et al. Accurate differentiation of parkinsonism and essential tremor using visual assessment of [123I]-FP-CIT SPECT imaging: The [123I]-FP-CIT study group. Mov Disord. 2000;15(3):503-510. doi:10.1002/1531-8257(200005)15:3less than 503::AID-MDS1013> 3.0.CO;2-V

18. Ondo WG, Jankovic J, Connor GS, et al. Topiramate in essential tremor: A double-blind, placebo-controlled trial. Neurology. 2006;66(5):672-677. doi:10.1212/01.wnl.0000200779.03748.e5

19. Koller WC, Vetere-Overfield B. Acute and chronic effects of propranolol and primidone in essential tremor. Neurology. 1989;39(12):1587-1588. doi:10.1212/WNL.39.12.1587

20. Deuschl G, Raethjen J, Hellriegel H, Elble R. Treatment of patients with essential tremor. Lancet Neurol. 2011;10(2):148-161. doi:10.1016/S1474-4422(10)70322-7

21. Bhatia KP, Bain P, Bajaj N, et al. Consensus statement on the classification of tremors. From the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord. 2018;33(1):75-87. doi:10.1002/mds.27121

22. Flora ED, Perera CL, Cameron AL, Maddern GJ. Deep brain stimulation for essential tremor: A systematic review. Mov Disord. 2010;25(11):1550-1559. doi:10.1002/mds.23195

---