- Etiology & Triggers:
- Exaggerated baseline physiologic tremor driven by ↑ sympathetic activity, toxicities, or metabolic states.
- Substances/Meds: Caffeine, nicotine, β-agonists (e.g., albuterol), SSRIs/SNRIs, lithium, valproate, tacrolimus, systemic steroids.
- Metabolic/Endocrine: Hyperthyroidism, hypoglycemia, pheochromocytoma.
- Systemic/Situational: Stress/anxiety, fatigue, acute illness/fever, EtOH/sedative withdrawal.
- Clinical Presentation:
- High-frequency (8–12 Hz), low-amplitude.
- Postural and kinetic: Elicited by holding arms outstretched against gravity or during movement; absent at rest.
- Bilateral and symmetric; isolated to fingers/hands (spares head, voice, and legs).
- Exam shows no rigidity, bradykinesia, ataxia, or focal neurologic deficits.
- Diagnosis & Workup:
- Primarily a clinical diagnosis.
- Initial labs: TSH & Free T4 (rule out thyrotoxicosis), BMP (glucose/electrolytes), and drug/tox levels if indicated.
- High-Yield Differentials:
- Essential Tremor: Slower (4–8 Hz), action/postural, improves with EtOH, (+) family hx, involves head/voice.
- Parkinson Disease: Slower (4–6 Hz), resting tremor (“pill-rolling”), asymmetric, improves with action, (+) rigidity/bradykinesia.
- Cerebellar Tremor: Slow (<5 Hz) intention tremor, worsens near visual target, (+) ataxia/dysmetria.
- Functional / Psychogenic Tremor: Abrupt onset, distractible (amplitude/frequency diminishes when performing contralateral cognitive/motor tasks), entrainment (tremor shifts frequency to match voluntary rhythmic movement of another limb).
- Management:
- First-line: Remove offending agent (e.g., stop caffeine, taper offending meds) or treat underlying condition (e.g., antithyroid drugs).
- Symptomatic pharmacotherapy: Propranolol (non-selective β-blocker) PRN or daily if the underlying trigger cannot be modified.