How do you differentiate and treat intention tremor vs resting tremor in a patient presenting with tremor?

Differentiating and Treating Intention vs. Resting Tremor

The key to differentiating intention tremor from resting tremor is observing when the tremor occurs during examination and identifying associated neurological signs, which will guide appropriate treatment strategies targeting the underlying cause.

Tremor Classification and Differentiation

Resting Tremor

• Occurs when the affected body part is completely relaxed and supported against gravity 1
• Typically disappears or diminishes with voluntary movement 2
• Characteristics:
  • Frequency: 3-6 Hz
  • Often unilateral at onset
  • "Pill-rolling" quality (thumb against fingers)
  • Associated with Parkinson's disease and parkinsonism syndromes
  • Often accompanied by bradykinesia and rigidity 3

Intention/Action Tremor

• Occurs during voluntary movement 1
• Can be further subdivided into:
  • Postural tremor: Present when maintaining a position against gravity
  • Kinetic tremor: Present during voluntary movement
  • Intention tremor: Worsens as approaching a target (terminal tremor) 4
• Characteristics:
  • Often bilateral
  • Typically higher frequency than resting tremor
  • Associated with cerebellar pathology, essential tremor, or physiologic tremor

Diagnostic Approach

1. Observe tremor activation conditions:

   • Is the tremor present at rest? (Parkinson's disease)
   • Is it present with sustained posture? (Essential tremor, physiologic tremor)
   • Does it worsen with goal-directed movement? (Cerebellar/intention tremor) 5

2. Look for associated neurological signs:

   • Bradykinesia, rigidity, postural instability (Parkinson's disease) 2
   • Ataxia, dysmetria, nystagmus (Cerebellar pathology)
   • Dystonic posturing (Dystonic tremor)
   • Flapping tremor of hands (Hepatic encephalopathy) 2

3. Consider tremor characteristics:

   • Frequency (high vs. low)
   • Amplitude
   • Symmetry (unilateral vs. bilateral)
   • Distribution (hands, head, voice, etc.)

Treatment Strategies

For Resting Tremor (Parkinsonian)

• First-line: Dopaminergic medications
  • Levodopa/carbidopa
  • Dopamine agonists (pramipexole, ropinirole)
• Second-line options:
  • Anticholinergics (trihexyphenidyl)
  • Amantadine
• Advanced options for medication-refractory cases:
  • Deep brain stimulation of subthalamic nucleus or globus pallidus
  • Focused ultrasound thalamotomy 4

For Intention/Action Tremor

• Essential tremor:

  • First-line: Propranolol (beta-blocker) or primidone
  • Second-line: Topiramate, gabapentin, or benzodiazepines
  • Refractory cases: Botulinum toxin injections or surgical interventions

• Cerebellar tremor:

  • Often difficult to treat
  • Trial of isoniazid, clonazepam, or propranolol
  • Treat underlying cause if identifiable

• Functional tremor:

  • Superimpose alternative voluntary rhythms
  • Entrainment techniques
  • Relaxation of affected muscles
  • Cognitive behavioral therapy 2

Special Considerations

Wilson's Disease

• Consider in young patients with tremor
• Look for Kayser-Fleischer rings
• Check ceruloplasmin levels and 24-hour urinary copper
• Treatment with chelating agents is essential 2, 6

Drug-Induced Tremor

• Review medication list for potential tremor-inducing drugs:
  • Antipsychotics
  • SSRIs
  • Stimulants
  • Valproate
  • Lithium
  • Beta-agonists 1

Hepatic Encephalopathy

• May present with flapping tremor (asterixis)
• Look for other signs of liver disease and encephalopathy
• Treat underlying liver condition and reduce ammonia levels 2

Common Pitfalls to Avoid

1. Misdiagnosing essential tremor as Parkinson's disease

   • Essential tremor is primarily postural/action, bilateral, and lacks other parkinsonian features

2. Missing Wilson's disease

   • Always consider in young patients with tremor, especially with psychiatric symptoms or liver abnormalities

3. Overlooking drug-induced tremors

   • Perform thorough medication review, including over-the-counter drugs

4. Confusing dystonic tremor with essential tremor

   • Look for abnormal posturing or positioning of affected body parts

5. Failing to recognize psychogenic tremor

   • Features include abrupt onset, spontaneous remission, changing characteristics, and extinction with distraction 1

By systematically evaluating the tremor's characteristics and associated neurological signs, clinicians can accurately differentiate between tremor types and implement appropriate treatment strategies to improve patient outcomes.