What is the difference in diagnosis and management of essential tremor vs intention tremor in an older adult patient?

Essential Tremor vs Intention Tremor: Diagnosis and Management

Key Clinical Distinction

Essential tremor is a bilateral action tremor (4-8 Hz) that occurs during voluntary movements like writing or drinking, while intention tremor is a coarse, irregular cerebellar tremor that progressively worsens as the limb approaches a target and is accompanied by dysarthria and ataxic gait. 1, 2

Diagnostic Features

Essential Tremor Characteristics

• Bilateral action tremor of arms and hands that occurs during voluntary movements 1, 3
• Frequency of 4-8 Hz with consciousness intact during episodes 2
• Worsens with emotional stress, caffeine consumption, and physical exertion 2
• Autosomal dominant inheritance in 50% of cases 2
• May have postural tremor component, and 25% develop moderate-to-severe intention tremor as disease progresses 4
• Can involve head and voice, though isolated head/voice tremor argues against the diagnosis 5

Intention Tremor Characteristics

• Coarse, irregular tremor that becomes progressively worse as the limb approaches a target during goal-directed movements 1, 2
• Often has a "wing-beating" appearance 1
• Accompanied by cerebellar signs: dysarthria, ataxic gait, and other signs of cerebellar dysfunction 1, 2
• May be unilateral or bilateral depending on lesion location 2
• Associated with cerebellar pathology or its connections 1

Critical Diagnostic Pitfall

Some ET patients (25%) develop intention tremor as the disease progresses, representing more advanced cerebellar dysfunction rather than a separate diagnosis. 4 These patients are older, have longer disease duration, and show more head/trunk involvement. 4

Diagnostic Workup

• Clinical examination focusing on tremor activation conditions (rest vs. postural vs. kinetic vs. intention), frequency, and distribution 6
• Assess for cerebellar signs: ataxia, dysarthria, dysmetria, and gait abnormalities 2
• DaTscan (ioflupane SPECT/CT) essentially excludes Parkinson's disease in diagnostically uncertain cases 2
• MRI to identify cerebellar lesions or structural abnormalities if intention tremor is present 2

Management Approach

Essential Tremor Treatment Algorithm

First-line pharmacological treatment (initiate only when tremor interferes with function or quality of life): 1, 7

1. Propranolol 80-240 mg/day - most established medication with 40+ years of efficacy data, effective in up to 70% of patients 7

   • Contraindications: COPD, asthma, bradycardia, congestive heart failure 1, 7
   • Dual benefit for patients with hypertension 1, 7
   • Side effects: lethargy, depression, dizziness, hypotension, exercise intolerance 7

2. Primidone - alternative first-line option, effective in up to 70% of patients 7

   • Clinical benefits may take 2-3 months to appear 7
   • Side effects: behavioral disturbances, irritability, sleep disturbances 7
   • Teratogenic risk (neural tube defects) - counsel women of childbearing age 7

Second-line options if first-line agents fail: 7

• Gabapentin (limited evidence for moderate efficacy) 7
• Carbamazepine (generally less effective than first-line therapies) 7

Surgical interventions for medication-refractory cases causing significant disability: 1, 7

1. MRgFUS thalamotomy - preferred option for unilateral tremor 1, 7

   • 56% sustained tremor improvement at 2-4 years 1, 7
   • Lowest complication rate (4.4%) vs. radiofrequency thalamotomy (11.8%) and DBS (21.1%) 1, 7
   • Contraindications: inability to undergo MRI, skull density ratio <0.40, bilateral treatment needed, previous contralateral thalamotomy 1, 7

2. Deep brain stimulation (DBS) - preferred for bilateral tremor or younger patients 7

   • Adjustable and reversible treatment option 7
   • Higher complication rate (21.1%) but suitable for bilateral cases 7

Intention Tremor Treatment

Intention tremor is more challenging to treat pharmacologically than essential tremor. 1 Management focuses on:

• Physical and occupational therapy with adaptive devices to improve function 1
• Rhythm modification techniques: superimposing alternative rhythms on tremor and gradually slowing movement to rest 7
• Using gross rather than fine movements for activities like handwriting 7
• Avoiding cocontraction or muscle tensing as long-term strategy 7
• Avoid prescribing aids in acute phase as they may interrupt normal automatic movement patterns 7

Surgical options (MRgFUS, DBS, radiofrequency thalamotomy) may be considered for refractory cases, though evidence is more limited than for essential tremor. 1, 7

Special Considerations in Older Adults

• Beta-blockers: Exercise caution with excessive heart rate reduction in elderly patients, which may lead to serious adverse events 7
• Assess for comorbidities that contraindicate beta-blockers (COPD, heart failure, bradycardia) 1, 7
• Screen for dementia and severe depression before considering surgical interventions 7
• Evaluate functional impact on activities of daily living to guide treatment intensity 1, 5