Clinical Diagnosis: Essential Tremor (ET)

What the Video Shows

1. Prominent rhythmic head tremor ("titubation") - present at rest while sitting
2. Bilateral postural/action tremor of the upper limbs - visible when arms are outstretched with fingers spread, affecting both hands symmetrically

Why Essential Tremor is the Leading Diagnosis

"Head tremor (titubation) suggests a diagnosis other than PD, such as essential tremor, dystonic neck tremor, or a cerebellar tremor..."

"The presence of head tremor should raise the possibility of essential tremor or of dystonic tremor associated with cervical dystonia..."

• Frequency of 4-8 Hz (lower end of range)
• Appears or is enhanced with postural maintenance or movement (action/postural tremor)
• Not associated with other neurologic changes ("essential")
• Commonly involves hands, and head tremor is well-recognized - observed as isolated head tremor or in combination with limb tremor
• Worsened by emotion, exercise, and fatigue
• Often familial (autosomal dominant with high penetrance)

Differential Diagnosis

Key Clinical Pearls

• In PD, head tremor is rare; its presence essentially argues against a pure Parkinson's diagnosis
• About 20-30% of ET patients can have a rest component, which can cause confusion with PD - especially in long-standing disease
• ET patients have a 4-5x increased risk of later developing PD (PMC3475963)
• A striking response to small amounts of alcohol is particularly characteristic of ET and can help distinguish it clinically

Recommended Workup

1. Neurological exam - assess for bradykinesia, rigidity, gait, postural reflexes
2. Thyroid function tests (TFTs) - hyperthyroidism is a common reversible cause of enhanced physiologic tremor
3. DaTscan (dopamine transporter scan) - if PD cannot be excluded clinically; normal in ET, reduced in PD
4. Cervical MRI - if dystonic features are present (abnormal head posture, torticollis)
5. Family history - ET is autosomal dominant; a positive family history strongly supports the diagnosis

Management of ET

• First-line: Propranolol (non-selective beta-blocker) or Primidone
• Second-line: Topiramate, gabapentin, clonazepam
• For refractory cases: Deep Brain Stimulation (DBS) of the ventral intermediate thalamus (VIM nucleus)

Differential Diagnosis: Tremor + Fever

Organized by Priority

🔴 EMERGENCIES - Rule Out First

1. Serotonin Syndrome

• Cause: Serotonergic drugs (SSRIs, SNRIs, MAOIs, tramadol, lithium, dextromethorphan, linezolid, "ecstasy")
• Key features: Tremor, clonus (especially ankles), hyperreflexia, agitation, diaphoresis, tachycardia, hyperthermia
• Onset: Rapid (within hours of drug initiation or dose increase)
• Hunter Criteria for diagnosis (from Rosen's Emergency Medicine):
  • Spontaneous clonus
  • Inducible clonus + agitation or diaphoresis
  • Tremor + hyperreflexia
  • Hypertonic + temperature >38°C + ocular clonus

2. Neuroleptic Malignant Syndrome (NMS)

• Cause: Dopamine antagonists (antipsychotics, metoclopramide, haloperidol)
• Key features: Fever >38°C, lead-pipe muscle rigidity, altered mental status, autonomic instability, elevated CK
• Tremor type: Coarse, can resemble parkinsonism
• Onset: Slower than serotonin syndrome (days to weeks after drug exposure)

3. Viral Encephalitis

"Encephalitis is characterized by altered mental status, ataxia, tremor, myoclonus, parkinsonism, and/or varying degrees of flaccid paralysis."

• West Nile Virus: Fever + tremor + parkinsonism + flaccid paralysis; MRI shows T2 hyperintensity in thalamus and basal ganglia
• Herpes Simplex Encephalitis (HSE): Fever + altered consciousness + focal signs + seizures; temporal lobe involvement
• Japanese Encephalitis / Arboviral: Fever + movement disorder + altered sensorium
• COVID-19 encephalitis / post-infectious: Emerging cause of tremor with systemic fever

4. Bacterial Meningitis / Meningoencephalitis

• Fever + headache + neck stiffness + photophobia
• Tremor may occur as part of cortical irritation or toxic-metabolic dysfunction
• Can progress to septic encephalopathy with multifocal tremors

🟠 URGENT - Toxic-Metabolic

5. Thyroid Storm

• Cause: Severe hyperthyroidism precipitated by stress, infection, surgery, or iodine load
• Key features: Fever >38.5°C, fine tremor, tachyarrhythmia, agitation, diaphoresis, goiter
• This patient's postural tremor + fever could represent thyroid storm
• Scott-Brown's Otorhinolaryngology notes fever + tremor + tachycardia as classic thyrotoxicosis features

6. Alcohol Withdrawal / Delirium Tremens

"Tremor, irritability, nausea, tachycardia, hypertension, sweating, perceptual distortion, seizures (6-48h after last drink)..."

• Fever occurs as part of the hyperadrenergic state + potential aspiration/infection
• Tremor is coarse postural/action tremor
• History of alcohol use is key

7. Septic Encephalopathy

• Any severe systemic infection (pneumonia, UTI, bacteremia) can cause toxic encephalopathy
• Tremor, asterixis, myoclonus, confusion in the context of systemic sepsis
• Common in elderly patients

🟡 IMPORTANT - Infectious + Systemic

8. Cerebral Malaria

• In endemic regions: fever + tremor + altered sensorium + seizures
• Plasmodium falciparum; thick and thin blood smears essential

9. Typhoid Fever (Enteric Fever)

• Rose spots, relative bradycardia, stepladder fever
• Neuropsychiatric typhoid: tremor, delirium, meningismus

10. Rickettsial Infections / Viral Hemorrhagic Fevers

• Argentine hemorrhagic fever (arenavirus): fever + cerebellar/tremor syndrome (Bradley & Daroff's Neurology)
• Rocky Mountain Spotted Fever: fever + neurological signs

11. Subacute Bacterial Endocarditis (SBE)

• Persistent fever + embolic phenomena to brain
• Tremor from septic emboli causing cerebral microabscesses or toxic encephalopathy

🟢 CHRONIC CONDITIONS EXACERBATED BY FEVER

12. Exacerbation of Pre-existing Essential Tremor

"A variety of everyday circumstances - stress, anxiety, hunger, fatigue, fever, too much caffeine - can enhance the tremor."

• The most clinically straightforward explanation: this patient's ET is worsened by a concurrent febrile illness (any cause - pneumonia, UTI, viral infection)
• No primary neurological emergency; treat the underlying infection

13. Enhanced Physiologic Tremor from Fever/Catecholamines

• Fever itself raises catecholamine levels, stimulating muscular beta-adrenergic receptors
• Any systemic febrile illness can produce or worsen postural/action tremor

Diagnostic Approach Summary

Tremor + Fever
     |
     ├── Drug history? → Serotonin syndrome / NMS
     ├── Neck stiffness, photophobia? → Meningitis/Encephalitis → LP + MRI
     ├── Alcohol history, last drink? → Alcohol withdrawal
     ├── Thyroid symptoms, tachycardia, goiter? → Thyroid storm → TFTs
     ├── Travel history? → Malaria / Arboviral → Blood smear, serology
     ├── Fever + sepsis signs? → Septic encephalopathy
     └── No alarm features + known ET? → Fever exacerbating ET