What is the appropriate diagnostic and treatment approach for a patient presenting with new onset tremor?

Neurological Examination for New-Onset Tremor

The neurological examination for new-onset tremor must systematically categorize the tremor by its activation condition (rest vs. action), topographic distribution, frequency, and amplitude to differentiate between the most common etiologies: enhanced physiologic tremor, essential tremor, and parkinsonian tremor. 1

Classification by Activation Condition

Rest Tremor Assessment

• Observe the patient with limbs completely relaxed and fully supported against gravity (e.g., hands resting in lap while seated) to identify rest tremor 1
• Parkinsonian rest tremor is typically unilateral, 4-6 Hz frequency, "pill-rolling" quality, and becomes less prominent with voluntary movement 1, 2
• Rest tremor that persists during action suggests Parkinson's disease rather than essential tremor 2

Action Tremor Assessment

• Postural tremor: Have patient extend arms horizontally in front of body with fingers spread 1, 3
• Kinetic tremor: Observe during finger-to-nose testing and other goal-directed movements 1, 3
• Isometric tremor: Have patient push against resistance (e.g., pressing palms together) 1
• Essential tremor manifests as bilateral postural and kinetic tremor, typically 4-12 Hz, affecting hands most commonly 1, 4

Critical Distinguishing Features

Signs Indicating Parkinson's Disease

A diagnosis of Parkinson's disease is likely if the patient has two of three major clinical features: resting tremor, bradykinesia, and rigidity 2

• Bradykinesia: Test with rapid alternating movements (finger tapping, hand opening/closing, foot tapping) - look for progressive slowing and decrement in amplitude 2
• Rigidity: Assess tone in all limbs with passive movement, checking for cogwheel rigidity 2
• Minor signs: Masked facies, reduced blink rate, hypophonic speech, micrographia, shuffling gait, reduced arm swing, postural instability 2

Signs Indicating Essential Tremor

• Bilateral, symmetric postural and kinetic tremor (though may start unilaterally) 1, 4
• Improves with alcohol consumption in 50-70% of cases (ask specifically about this in history) 4
• Family history positive in 50% of cases (autosomal dominant inheritance) 1
• Absence of other neurological signs - no bradykinesia, rigidity, or gait abnormality 1, 4

Topographic Distribution Assessment

• Head tremor: Isolated head tremor (without hand tremor) is more likely dystonic rather than essential tremor 3
• Voice tremor: Can be part of essential tremor spectrum 3
• Unilateral tremor: Suggests Parkinson's disease over essential tremor 1, 2

Red Flags for Secondary Causes

Enhanced Physiologic Tremor Features

• High-frequency (8-12 Hz), low-amplitude tremor 1
• Bilateral postural tremor without rest component 1
• History of anxiety, caffeine intake, fatigue, or medications (beta-agonists, valproate, lithium, SSRIs, steroids) 1

Psychogenic Tremor Features

• Abrupt onset with spontaneous remissions 1
• Changing tremor characteristics (frequency, amplitude, distribution) 1
• Extinction with distraction - give patient a cognitive task and observe if tremor disappears 1
• Entrainment test: Have patient tap with unaffected hand at specific frequency; psychogenic tremor may entrain to this frequency or stop 3

Cerebellar Tremor Features

• Intention tremor - worsens as target is approached during finger-to-nose testing 1
• Associated cerebellar signs: Dysmetria, dysdiadochokinesia, ataxic gait, nystagmus 1

Frequency and Amplitude Documentation

• Low frequency (3-5 Hz): Suggests parkinsonian or cerebellar tremor 1, 3
• Medium frequency (4-8 Hz): Typical of essential tremor 1, 3
• High frequency (>8 Hz): Suggests enhanced physiologic tremor 1, 3
• Document amplitude as mild, moderate, or severe based on functional impact 3

Common Pitfalls to Avoid

• Do not diagnose essential tremor if rest tremor is present - this suggests Parkinson's disease 1, 2
• Do not assume bilateral tremor excludes Parkinson's disease - while typically starting unilaterally, it can become bilateral over time 2
• Do not overlook medication-induced tremor - carefully review all medications including over-the-counter drugs 1
• Do not diagnose psychogenic tremor as exclusion - positive clinical signs must be demonstrated 3

When Advanced Testing Is Needed

• If diagnostic uncertainty between Parkinson's disease and essential tremor persists after clinical examination, consider DaTscan (single-photon emission computed tomography) to visualize dopaminergic pathway integrity 1
• Transcranial ultrasonography may be useful to diagnose Parkinson's disease 1
• Electrophysiological measurements can objectively assess tremor frequency and amplitude when clinical assessment is insufficient 3