(See also Overview of Movement and Cerebellar Disorders Overview of Movement and Cerebellar Disorders Voluntary movement requires complex interaction of the corticospinal (pyramidal) tracts, basal ganglia, and cerebellum (the center for motor coordination) to ensure smooth, purposeful movement... read more .)
Tremor may be
Normal (physiologic)
Pathologic
Physiologic tremor, usually barely perceptible, becomes noticeable in many people during physical or mental stress.
Tremors vary in
Pattern of occurrence (eg, intermittent, constant)
Severity
Acuity (eg, gradual, abrupt)
The severity of tremor may not be related to the seriousness of the underlying disorder. For example, essential tremor is generally thought of as benign and should not shorten life, but symptoms can be disabling, and cerebellar degeneration has been detected in some neuropathologic studies.
Pathophysiology of Tremor
Various lesions in the brain stem, extrapyramidal system, or cerebellum can cause tremors. Neural dysfunction or lesions that cause tremor may result from injury, ischemia, metabolic abnormalities, or a neurodegenerative disorder. Sometimes tremor is a familial condition (eg, essential tremor).
Classification
Tremor is classified primarily based on when it occurs:
Resting tremors are visible at rest and occur when a body part is completely supported against gravity. Resting tremors are minimal or absent during activity. They occur at a frequency of 3 to 6 cycles/seconds (hertz [Hz]).
Action tremors are maximal when a body part is moved voluntarily. Action tremors may or may not change in severity as a target is reached; they can occur at very different frequencies, but the frequency is always < 13 Hz.
Action tremors include kinetic, intention, and postural tremors.
Kinetic tremors appear in the last part of a movement toward a target; amplitude is low.
Intention tremors occur during voluntary movement toward a target, but amplitude is high and frequency is low during the complete movement, while the tremor worsens as the target is reached (as seen in finger-to-nose testing); they occur at a frequency of 3 to 10 Hz.
Postural tremors are maximal when a limb is maintained in a fixed position against gravity (eg, holding the arms stretched out); they occur at a frequency of 5 to 8 Hz. Sometimes they are modified by specific positions or tasks, which may indicate their origin; for example, dystonia Dystonias Dystonias are sustained involuntary muscle contractions of antagonistic muscle groups in the same body part, leading to sustained abnormal posturing or jerky, twisting, intermittent spasms that... read more may trigger a tremor (dystonic tremor).
Complex tremors can have components of more than one type of tremor.
Tremor can also be classified based on whether it is
Physiologic (within the range of normal)
A primary disorder (essential tremor, Parkinson disease)
Secondary to a disorder (eg, stroke)
Tremor is usually described based on frequency of oscillations (rapid or slow) and amplitude of movement (fine [low amplitude] or coarse [high amplitude]).
Etiology of Tremor
Physiologic tremor
Physiologic tremor occurs in otherwise healthy people. It is an action or postural tremor that tends to affect both hands about equally; amplitude is usually fine. It is often noticeable only when certain stressors are present. These stressors include
Anxiety
Fatigue
Exercise
Sleep deprivation
Withdrawal of alcohol or certain other central nervous system (CNS) depressant drugs (eg, benzodiazepines, opioids)
Certain disorders (eg, hyperthyroidism), when symptomatic
Consumption of caffeine or recreational drugs such as cocaine, amphetamines, or phencyclidine
Use of certain therapeutic drugs, such as theophylline, beta-adrenergic agonists, corticosteroids, and valproate
Pathologic (nonphysiologic) tremor
There are many causes (see table Some Causes of Tremor Some Causes of Tremor Tremors are involuntary, rhythmic, oscillatory movements of reciprocal, antagonistic muscle groups, typically involving the hands, head, face, vocal cords, trunk, or legs. Diagnosis is clinical... read more ), but the most common are
For action (including postural) tremors: Essential tremor
For intention tremors: Cerebellar dysfunction Cerebellar Disorders Cerebellar disorders have numerous causes, including congenital malformations, hereditary ataxias, and acquired conditions. Symptoms vary with the cause but typically include ataxia (impaired... read more (eg, due to a stroke Overview of Stroke Strokes are a heterogeneous group of disorders involving sudden, focal interruption of cerebral blood flow that causes neurologic deficit. Strokes can be Ischemic (80%), typically resulting... read more
, trauma Traumatic Brain Injury (TBI) Traumatic brain injury (TBI) is physical injury to brain tissue that temporarily or permanently impairs brain function. Diagnosis is suspected clinically and confirmed by imaging (primarily... read more 
, or multiple sclerosis Multiple Sclerosis (MS) Multiple sclerosis (MS) is characterized by disseminated patches of demyelination in the brain and spinal cord. Common symptoms include visual and oculomotor abnormalities, paresthesias, weakness... read more 
)
Drugs (see table Some Causes of Tremor by Type Some Drug Causes of Tremor by Type Tremors are involuntary, rhythmic, oscillatory movements of reciprocal, antagonistic muscle groups, typically involving the hands, head, face, vocal cords, trunk, or legs. Diagnosis is clinical... read more ) can cause or aggravate different types of tremor. Low doses of some sedatives (eg, alcohol) may relieve some tremors (eg, essential and physiologic tremor); higher doses may cause or exacerbate tremor.
Evaluation of Tremor
Because the diagnosis of tremor is largely clinical, a meticulous history and physical examination are essential.
History
History of present illness should cover
Acuity of onset (eg, gradual, abrupt)
Age at onset
Body parts affected
Provoking factors (eg, movement, rest, standing)
Alleviating or exacerbating factors (eg, alcohol, caffeine, stress, anxiety)
If onset is abrupt, patients should be asked about potential triggering events (eg, recent trauma or illness, use of a new drug).
Review of systems should seek symptoms of causative disorders, including
Recent sudden onset of motor weakness, language difficulties, or dysarthria: Stroke Overview of Stroke Strokes are a heterogeneous group of disorders involving sudden, focal interruption of cerebral blood flow that causes neurologic deficit. Strokes can be Ischemic (80%), typically resulting... read more
Confusion and fever: Meningitis Overview of Meningitis Meningitis is inflammation of the meninges and subarachnoid space. It may result from infections, other disorders, or reactions to drugs. Severity and acuity vary. Findings typically include... read more , encephalitis Encephalitis Encephalitis is inflammation of the parenchyma of the brain, resulting from direct viral invasion. Acute disseminated encephalomyelitis is brain and spinal cord inflammation caused by a hypersensitivity... read more , brain abscess Brain Abscess A brain abscess is an intracerebral collection of pus. Symptoms may include headache, lethargy, fever, and focal neurologic deficits. Diagnosis is by contrast-enhanced MRI or CT. Treatment is... read more
, or brain tumor Overview of Intracranial Tumors Intracranial tumors may involve the brain or other structures (eg, cranial nerves, meninges). The tumors usually develop during early or middle adulthood but may develop at any age; they are... read more 
Muscle rigidity, gait and postural problems, and slowness of movement: Parkinson disease Parkinson Disease Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more or other forms of parkinsonism Secondary and Atypical Parkinsonism Secondary parkinsonism refers to a group of disorders that have features similar to those of Parkinson disease but have a different etiology. Atypical parkinsonism refers to a group of neurodegenerative... read more
Weight loss, increased appetite, palpitations, diarrhea, and heat intolerance: Hyperthyroidism Hyperthyroidism Hyperthyroidism is characterized by hypermetabolism and elevated serum levels of free thyroid hormones. Symptoms are many and include tachycardia, fatigue, weight loss, nervousness, and tremor... read more
Agitation and hallucinations: Alcohol withdrawal Alcohol Toxicity and Withdrawal Alcohol (ethanol) is a central nervous system depressant. Large amounts consumed rapidly can cause respiratory depression, coma, and death. Large amounts chronically consumed damage the liver... read more or drug toxicity
Past medical history should cover conditions associated with tremor (see table Some Causes of Tremor Some Causes of Tremor Tremors are involuntary, rhythmic, oscillatory movements of reciprocal, antagonistic muscle groups, typically involving the hands, head, face, vocal cords, trunk, or legs. Diagnosis is clinical... read more ). Family history should include questions about tremor in 1st-degree relatives. The drug profile should be reviewed for causative drugs (see table Some Drug Causes of Tremor Some Drug Causes of Tremor by Type Tremors are involuntary, rhythmic, oscillatory movements of reciprocal, antagonistic muscle groups, typically involving the hands, head, face, vocal cords, trunk, or legs. Diagnosis is clinical... read more ), and patients should be asked specifically about caffeine intake and alcohol and recreational drug use (particularly recent discontinuation).
Physical examination
A complete and extensive neurologic examination Introduction to the Neurologic Examination The neurologic examination begins with careful observation of the patient entering the examination area and continues during history taking. The patient should be assisted as little as possible... read more is mandatory and should include evaluation of mental status, cranial nerves, motor and sensory function, gait, muscle stretch reflexes, and cerebellar function (with observation of finger-to-nose, shin-to-heel, and rapid alternating hand movements). The examiner should test muscles for rigidity by moving the limbs through their range of motion.
Vital signs should be reviewed for tachycardia, hypertension, or fever. General examination should note any cachexia, psychomotor agitation, and absence of facial expressions (which may indicate bradykinesia). The thyroid should be palpated for nodules and enlargement, and any signs of exophthalmus or eyelid lag should be noted.
Focused examination should note distribution and frequency of the tremor while
The affected body parts are at rest and fully supported (eg, in the patient’s lap).
The patient assumes certain postures (eg, holding the arms outstretched).
The patient is walking or doing tasks with the affected body part.
The examiner should note whether the tremor changes during mental distraction tasks (eg, serial subtraction of 7 from 100). The quality of the voice should be observed while the patient sustains a long note.
Red flags
The following findings are of particular concern:
Abrupt onset
Onset in people < 50 and with no family history of benign tremor
Other neurologic deficits (eg, change in mental status, motor weakness, cranial nerve palsy, ataxic gait, dysarthria)
Tachycardia and agitation
Interpretation of findings
Clinical findings help suggest a cause (see table Some Causes of Tremor Some Causes of Tremor Tremors are involuntary, rhythmic, oscillatory movements of reciprocal, antagonistic muscle groups, typically involving the hands, head, face, vocal cords, trunk, or legs. Diagnosis is clinical... read more ).
Tremor type and onset are useful clues:
Resting tremors usually indicate Parkinson disease, particularly when they are unilateral or when tremor is isolated to the chin, voice, or leg.
Intention tremors suggest a cerebellar disorder but may result from multiple sclerosis or Wilson disease.
Postural tremors suggest physiologic or essential tremor if onset is gradual; it suggests a toxic or metabolic disorder if onset is sudden.
Severe essential tremor is often confused with Parkinson disease but can usually be distinguished by specific characteristics (see table Some Characteristics Differentiating Parkinson Disease From Essential Tremor Some Characteristics Differentiating Parkinson Disease From Essential Tremor Tremors are involuntary, rhythmic, oscillatory movements of reciprocal, antagonistic muscle groups, typically involving the hands, head, face, vocal cords, trunk, or legs. Diagnosis is clinical... read more ). Occasionally, the two syndromes overlap (mixed essential tremor–Parkinson disease).
The following findings may help suggest causes of tremor:
Sudden onset is most typical of psychogenic tremor after physical pathologic processes have been ruled out.
Stepwise progression suggests an ischemic vascular disorder or multiple sclerosis
Development of tremor after use of a new drug suggests that the drug is the cause.
Onset of tremor with agitation, tachycardia, and hypertension within 24 to 72 hours of hospitalization may suggest withdrawal from alcohol, a sedative, or an illicit substance.
Gait is observed. Gait abnormalities may suggest multiple sclerosis, stroke, Parkinson disease, or a cerebellar disorder. Gait is characteristically narrow-based and shuffling in Parkinson disease and wide-based and ataxic in cerebellar disorders. The gait may have histrionic or inconsistent qualities in patients with psychogenic tremor. In patients with essential tremor, gait is often normal, but tandem gait (placing heel to toe) may be abnormal.
Psychogenic tremor can be identified because psychogenic tremors decrease or disappear when the patient is mentally distracted and when tremor frequency synchronizes (entrains) to a volitional tapping rhythm by an unaffected body part. Maintaining different volitional movement frequencies simultaneously in two different body parts is difficult.
Testing
In most patients, history and physical examination are sufficient to identify the likely etiology of tremor. However, MRI or CT of the brain should be done if
Tremor onset is acute.
Progression is rapid.
Focal neurologic signs suggest a structural lesion (eg, stroke, brain tumor, a demyelinating disorder).
When the cause of tremor is unclear (based on history and physical examination findings), the following are done:
Thyroid-stimulating hormone (TSH) and thyroxine (T4) are measured to check for hyperthyroidism.
Calcium and parathyroid hormone are measured to check for hyperparathyroidism or hypoparathyroidism.
Glucose testing is done to rule out hypoglycemia.
In patients with toxic encephalopathy, the underlying condition is usually readily apparent, but measurement of BUN and ammonia levels can help confirm the etiology. Measurement of free metanephrines in plasma is indicated in patients with unexplained refractory hypertension. Serum ceruloplasmin and urinary copper levels should be measured to check for Wilson disease if patients are < 40 and have tremor with an unclear cause (with or without parkinsonism) and no family history of benign tremor.
Although electromyography (EMG) can differentiate true tremor from other movement disorders (eg, myoclonus, clonus, epilepsia partialis continua), it is rarely required. However, EMG may help establish peripheral neuropathy as a potential cause of tremor if a neuropathy is clinically suspected.
Treatment of Tremor
Physiologic tremors
No treatment is necessary unless symptoms are bothersome. Avoiding triggers (such as caffeine, fatigue, sleep deprivation, drugs, and, when possible, stress and anxiety) can help prevent or reduce symptoms.
Physiologic tremor is enhanced by alcohol withdrawal, by hyperthyroidism, and by use of drugs and by conditions that can cause tremor. The tremor responds to treatment of the underlying condition.
Oral benzodiazepines (eg, diazepam 2 to 10 mg, lorazepam 1 to 2 mg, oxazepam 10 to 30 mg) given 3 or 4 times a day may be useful for people with tremor and chronic anxiety, but continuous use should be avoided. Propranolol (20 to 80 mg orally 4 times a day) and other beta-blockers are often effective for tremor enhanced by drugs or acute anxiety (eg, stage fright).
Essential tremors
Propranolol 20 to 80 mg orally 4 times a day (or other beta-blockers) is often effective, as is primidone 50 to 250 mg orally 3 times a day. For some patients, a small amount of alcohol is effective; however, alcohol is not routinely recommended for treatment because abuse is a risk.
Second-line drugs are topiramate 25 to 100 mg orally 2 times a day and gabapentin 300 mg orally 2 or 3 times a day. Benzodiazepines may be added if other drugs do not control the tremor.
Cerebellar tremors
No effective drug is available; physical therapy (eg, weighting the affected limbs, teaching patients to brace the proximal limb during activity) sometimes helps.
Parkinsonian tremors
Parkinson disease Treatment Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more is treated.
Levodopa Levodopa Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more is usually the treatment of choice for most parkinsonian tremors.
Anticholinergic drugs Parkinson Disease Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more may be considered in certain cases, but their adverse effects (decreased mental concentration, dry mouth, dry eyes, urinary retention and the possibility that they enhance tau pathology) may outweigh their benefits, particularly in older patients.
Other drugs include dopamine agonists Dopamine agonists Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more (eg, pramipexole, ropinirole), MAO type B inhibitors Selective MAO-B inhibitors Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more (selegiline, rasagiline), catechol O-methyltransferase (COMT) inhibitors Catechol O-methyltransferase (COMT) inhibitors Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more (entacapone, tolcapone—used only in combination with levodopa), and amantadine Amantadine Parkinson disease is a slowly progressive, degenerative disorder characterized by resting tremor, stiffness (rigidity), slow and decreased movement (bradykinesia), and eventually gait and/or... read more .
Disabling tremor
For severe, disabling, drug-refractory essential tremor, surgical management with unilateral stereotactic thalamotomy or chronic unilateral or bilateral thalamic deep brain stimulation may be considered.
Dystonic tremor may respond better to functional neurosurgery targeting the internal portion of the globus pallidus.
In Parkinson disease, tremor substantially lessens after thalamic, internal globus pallidus, or subthalamic nucleus deep brain stimulation.
Although these techniques are widely available, they should be used only after reasonable drug therapy has failed and only in patients who do not have substantial cognitive or psychiatric impairment.
Geriatrics Essentials: Tremor
Many older patients attribute development of tremor to normal aging and may not seek medical attention. Although essential tremor is more prevalent among the older people, a thorough history and physical examination are required to rule out other causes and to determine whether the symptoms are severe enough to justify drug or surgical treatment.
Comparatively low doses of drugs may exacerbate tremor in older patients, and adjusting doses of chronically used drugs (eg, amiodarone, metoclopramide, selective serotonin reuptake inhibitors, thyroxine) to the lowest effective dose should be considered. Similarly, older patients are more vulnerable to adverse effects of drugs used to treat tremor; thus, these drugs should be used cautiously in older patients, usually at lower dosages than are otherwise considered optimal. If possible, anticholinergic drugs should not be used in older patients.
Tremor can significantly affect functional ability in older patients, particularly if they have other physical or cognitive impairments. Physical and occupational therapy can provide simple coping strategies, and assistive devices may help maintain quality of life.
Key Points
Tremor can be classified as resting or action (which includes intention, kinetic, and postural tremors).
The most common causes of tremor include physiologic tremor, essential tremor, and Parkinson disease.
History and physical examination can typically identify the etiology of tremor.
Consider Parkinson disease if patients have a resting tremor, consider essential or physiologic tremor if they have a postural or an action tremor, and consider cerebellar tremor if they have an intention tremor.
If tremor begins abruptly or occurs in patients who are < 50 and do not have a family history of benign tremor, evaluate them promptly and thoroughly with brain imaging and laboratory tests based on clinical presentation.
Treat according to the cause and type of tremor: avoidance of triggers (physiologic), propranolol or primidone (essential), physical therapy (cerebellar), usually levodopa (parkinsonian), and possibly deep brain stimulation (disabling and drug-refractory).
