Tremors are the most common movement disorder and are defined as rhythmic, involuntary movements of one or more parts of the body. Tremors are classified as resting or action tremor (i.e., postural and intention tremors). Resting tremors typically occur in patients with Parkinson disease and usually present as asymmetrical tremors that occur during rest. Postural tremors are usually essential or physiologic. Essential tremors are the most common type of tremor and usually involve the hands and head. They characteristically improve with alcohol consumption. Physiologic tremors occur when holding a position against gravity and are enhanced by increased sympathetic stimulation (e.g., caffeine, anxiety). Intention tremors suggest cerebellar lesions, which typically occur with strokes, trauma, or tumors. Patients present with a coarse hand tremor that is aggravated by goal-directed movements. A combination of tremor types is also possible. The diagnosis of tremors is typically clinical. Further laboratory tests and imaging may be required to determine the underlying condition. Treatment depends on the type of tremor.
|Common types of tremors |
|Resting tremor||Action tremor|
|Postural tremor||Intention tremor|
|Description|| || || |
|Etiology|| || |
|Onset|| || || |
|Associated features|| || |
|Improved by|| || || || |
- Age of onset: ∼ 60 years
- Pathophysiology: caused by a dysfunction of the basal ganglia, especially substantia nigra
- Typically, asymmetric resting tremor of the extremities (especially apparent in the hands); at a low frequency (4–6 Hz, rarely up to 9 Hz)
- “Pill-rolling” of hands that subsides with voluntary movements
- Reduced with target-directed movement
- In early Parkinson disease, unilateral tremors are common.
- Worsens with emotional stress
- Often associated with rigidity, bradykinesia, and postural instability (also see “ ”)
- Typically a clinical diagnosis
- MRI for atypical presentations
- Treatment: dopaminergic agents (see “ ”)
“Rest in the park”: One of the main causes of resting tremor is Parkinson disease.
- Most common form of tremor
- Bimodal distribution: teens and 6th decade of life (common in elderly patients)
- Etiology: positive family history (50–70%; autosomal dominant inheritance) or sporadic; benign form
- Localization: hands (∼ 90%); , head (∼ 30%; "yes-yes” or "no-no” motion), voice (∼ 15%)
- Mostly bilateral postural tremor with a frequency of 5–10 Hz
- The essential tremor may be accompanied by an intention tremor and/or a resting tremor .
- Diagnostics: usually a clinical diagnosis of exclusion
- Drugs of choice: propranolol or primidone
- Alternatives (if propranolol and primidone are unresponsive or contraindicated)
- In drug-resistant cases
Physiologic tremor 
- Epidemiology: may occur at any age
- A physiologic tremor does not suggest a disorder , while an enhanced physiologic tremor (higher-frequency oscillations, more visible) may be more significant and debilitating.
- The tremors are increased by sympathetic stimulation:
- Stress, exercise, or fatigue
- Intoxication: mercury poisoning, caffeine, alcohol
- Drug-induced: valproate, lithium, SSRIs, tricyclic antidepressants, beta-2 agonists, levothyroxine, immunosuppressants (e.g., daclizumab, basiliximab)
- Withdrawal: alcohol, benzodiazepines, barbiturates, marijuana
- Medical conditions: hyperthyroidism or pheochromocytoma, Lewy body dementia
- Other: magnesium deficiency, hypoglycemia , Wilson disease
- Usually a fine bilateral postural tremor in the hands and fingers (∼ 10 Hz)
- Occurs while holding a position against gravity (e.g., extending arms in front of the body)
- Diagnostics: depends on the suspected underlying cause (thyroid function tests, blood glucose level, review of medications, history of substance use)
- Usually reversible once the underlying cause is treated
- Propranolol may be considered under certain conditions .
Orthostatic tremor 
- Etiology: unknown
Clinical features: associated with long periods of standing
- Trembling feeling in the legs
- Subjective feeling of unstable balance, and falling over
- Clinical diagnosis: Synchronized shaking of the legs may be seen or felt by the examiner.
- Electromyography of the legs while the patient is standing; detection of 13–18 Hz tremor
- Clinical features
- Physical therapy
Additional types of tremors
Flapping tremor (asterixis) 
- Clinical features
- Treatment: See “Treatment” in “” and “ ” articles.
Functional tremor 
- Etiology: : a potential feature of conversion disorder; may also occur in other psychiatric disorders (e.g., anxiety disorder, factitious disorder, depression)
- Complex resting, postural, and/or action tremor (can occur simultaneously)
- Sudden onset
- Worsens under direct observation and diminishes with distraction
- Quick progression to severe symptoms and disability
- Inconsistency over time with variable amplitude, frequency, or distribution of the movement
- Movement disorder does not seem related to an organic disease
- Voluntary coactivation of agonist and antagonist muscles with overlying tremor
- Associated with sensations of pain, weakness, and sensory loss without an organic cause
- Inquire about somatization in past history.
- Inquire about patterns of precipitating events
- Diagnosis of exclusion
- Used to diagnose functional tremor
- The patient is asked to perform a voluntary movement (e.g., tapping) with an unaffected limb in a set rhythm that is different from the frequency of the tremor.
- Positive test: the tremor of the affected limb will align with the frequency of the voluntary movement.