A tremor is an involuntary, rhythmic, shaking movement of part of the body, such as the hands, head, vocal cords, trunk, or legs. Tremors occur when muscles repeatedly contract and relax.
(See also Overview of Movement Disorders.)
Types of Tremors
There are several ways to classify tremors.
Tremors can be
Normal (physiologic)
Abnormal (pathologic), caused by a disorder or medication or other substance
Tremors are usually classified based on when they occur:
Resting tremor: Occurring mainly at rest
Action tremor: Occurring when a body part is moved voluntarily
Action tremors include
Resting tremors can be seen during rest and occur when a body part is completely supported. Resting tremors are slight or absent during activity.
Action tremors are most noticeable when a body part is moved intentionally (voluntarily). Action tremors may or may not change in severity as a target is reached. Action tremor can be subdivided into postural and kinetic tremors.
Postural tremors occur when a limb is maintained in one position that is not supported (as when holding the arms outstretched). Postural tremor may vary depending on the position.
Kinetic tremors occur during voluntary movement. They can be subdivided into simple kinetic tremor and intention tremor. Simple kinetic tremors do not change during a movement. Intention tremors worsen as the body part moves toward its target (as when reaching for a glass).
Tremors can also be classified by what causes them, as follows:
Physiologic (the normal tremors that everyone has to some degree)
Essential (a common hereditary disorder that rarely causes any other symptoms)
Cerebellar (caused by damage to part of the brain called the cerebellum)
Secondary (caused by a disorder, medication, or other substance)
Psychogenic (caused by psychologic factors)
Other important characteristics of tremors are
How fast the shaking is (frequency): Slow to fast
How wide the movement is (amplitude): Fine to coarse
How often the tremor occurs: Intermittent to constant
How severe it is
How rapidly it appears: Sudden to gradual
Doctors commonly use the following categories.
Physiologic tremor
Physiologic tremor is the normal tremor that everyone has to some degree. For example, most people's hands, when held outstretched, usually tremble slightly. Such slight, rapid tremor reflects the precise moment-by-moment control of muscles by nerves. In most people, the tremor is barely noticeable. However, a normal tremor may become more noticeable under certain conditions and may worry people. For example, the tremor may be more noticeable when people
Feel stressed or anxious
Are deprived of sleep
Stop drinking alcohol or taking a sedative (such as a benzodiazepine) or an opioid
asthma and chronic obstructive pulmonary disease [COPD]), corticosteroids, or illicit drugs (such as or amphetamines)
Have certain disorders, such as an overactive thyroid gland (hyperthyroidism) that is causing other symptoms
Essential tremor
Essential tremor results from a problem in the nervous system, but people with this tremor rarely have any other symptoms of nervous system dysfunction (neurologic symptoms). The cause is unclear, but the tremor often runs in families.
Essential tremor usually begins during early adulthood but can begin at any age. The tremor slowly becomes more noticeable as people age. Thus, it is sometimes incorrectly called senile tremor. The tremor usually involves the arms and hands and sometimes affects the head. When it affects the head, people may look as if they are nodding yes or shaking their head no. These tremors are usually worsened by holding a limb outstretched (against gravity) or by moving a limb.
Usually, essential tremor remains mild. However, it can be troublesome and embarrassing. It can affect handwriting and make using utensils difficult. In some people, the tremor gradually worsens over time, eventually resulting in disability. Symptoms may resemble those of Parkinson disease, and sometimes essential tremor is misdiagnosed as Parkinson disease. Rarely, people have Parkinson disease and essential tremor.
Resting tremor
Resting tremor occurs when muscles are at rest. An arm or a leg shakes even when a person is completely relaxed. The tremor becomes less noticeable or disappears when the person moves the affected muscles. Resting tremors are often slow and coarse.
These tremors develop when nerve cells in the part of the brain called the basal ganglia are disturbed. The basal ganglia help initiate and smooth out intended (voluntary) muscle movements. Such disturbances usually result from
Parkinson disease or disorders that cause the same symptoms as Parkinson disease (parkinsonism)
However, resting tremors can also result from use of medications or other substances that can affect basal ganglia, such as antipsychotic medications and some medications used to relieve nausea.
Resting tremors may be socially embarrassing, but because they go away when people try to do something (such as drinking a glass of water), they typically do not interfere with daily activities.
Intention tremor
This tremor occurs during a purposeful movement, as when reaching for an object with the hand. People may miss the object because of the tremor. Intention tremors worsen as people get closer to the targeted object. These tremors are relatively slow and wide (coarse).
Intention tremors may result from damage to the cerebellum, the part of the brain responsible for balance and coordination.
Common causes of intention tremor include
Certain hereditary disorders that affect the cerebellum (called spinocerebellar ataxias)
Other disorders and drugs can also cause the cerebellum to malfunction, resulting in an intention tremor. They include
A tumor
Overuse of sedatives or antiseizure medications
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Postural tremor
Postural tremors are most obvious when a limb is held in a position that requires resisting the pull of gravity, as when people hold their arms outstretched.
The most common postural tremors are
Essential tremor
Physiologic (normal) tremor
Complex tremor
Complex tremor is a tremor that has features of more than one type of tremor.
Common causes of complex tremors are
Psychologic factors
Widespread nerve damage such as that caused by diabetes or Guillain-Barré syndrome
Causes of Tremor
Many disorders can cause tremor. Most commonly, tremors are
Physiologic tremor (most common overall)
Essential tremor
Due to Parkinson disease
Due to a stroke or multiple sclerosis affecting parts of the brain that control movement
Due to severe liver disease
Due to alcohol withdrawal
Due to an overactive thyroid gland (hyperthyroidism)
Due to hereditary disorders involving the cerebellum, such as Friedreich ataxia and spinocerebellar ataxias
Due to use of certain drugs or exposure to certain toxic substances
Functional (psychogenic) tremor (due to psychologic factors)
Sometimes there is more than one cause of the tremors. For example, a person may have essential tremor and Parkinson disease.
Evaluation of Tremor
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
Warning signs
The following symptoms are cause for concern:
Tremors that start abruptly
Tremors in people who are under 50 years old and have no relatives who have had essential tremors
Other neurologic symptoms, such as a change in mental status, muscle weakness, changes in the way a person walks, and difficulty speaking
A rapid heart rate and agitation
When to see a doctor
People with warning signs should see a doctor immediately.
People without warning signs should see a doctor as soon as possible.
If people are under 50 years old and do not have a family history of essential tremors, they should see a doctor soon. Being evaluated by a doctor is important to make sure that the cause is not another disorder, a drug, or another substance.
What a doctor does
Doctors first ask questions about the person's symptoms and medical history and then do a physical examination. What doctors find during the history and physical examination often suggests a cause and the tests that may need to be done (see table Some Causes and Features of Tremor).
Doctors ask about the tremor:
When the tremor started
Whether the tremor began gradually or suddenly
Which body parts are affected
What triggers it (such as movement, rest, or standing)
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If the tremor began suddenly, doctors ask about events that may have triggered it (such as a recent injury or use of a new drug).
Doctors review the person's past medical history, looking for conditions associated with tremor
Doctors do a physical examination, paying particular attention to the neurologic examination (including the way the person walks). Doctors note which body parts are affected by the tremor. They observe how fast the shaking movements are in various situations:
When the affected body parts are at rest and when they are fully supported (for example, hands in the person's lap)
While the person maintains certain positions (such as holding the arms outstretched)
While the person is walking or doing tasks with the affected body part
The quality of the person's voice may be observed when holding a long note.
Doctors can usually identify the type of tremor based on its characteristics and results of the medical history and physical examination—for example,
Tremors that develop gradually: Usually physiologic or essential tremor
A tremor that starts suddenly: Possibly psychologic factors, a poison, a disorder (such as hyperthyroidism), stopping use of alcohol or another drug (such as a sedative), or use of a drug known to cause tremor
Some Causes and Features of Tremor
Cause | Features* | Diagnostic Approach† |
|---|---|---|
Postural tremors (tremor when a limb is held outstretched) | ||
Alcohol or another sedating substance (such as a benzodiazepine) when use is stopped | Agitation and a fine tremor starting 24–72 hours after the last use of alcohol or a another substance Sometimes high blood pressure, a rapid heart rate, or fever, especially in people who are hospitalized | A doctor's examination |
Medication or other substances, such as
| History of medication or substance use | Stopping the medication or substance to see whether the tremor goes away |
Hormonal, metabolic, and toxic abnormalities that affect the brain:
| A tremor plus one or more of the following:
For hyperthyroidism: Difficulty tolerating heat, excessive sweating, an increased appetite, weight loss, bulging eyes, and frequent bowel movements | Tests to help identify the cause, such as blood tests
|
Essential tremor | A persistent tremor that
No other symptoms of nervous system malfunction | A doctor's examination |
Physiologic tremor | A fine, rapid tremor that
| A doctor's examination |
Resting tremor | ||
Parkinsonism triggered by a drug, such as certain antipsychotic medications and medications used to relieve nausea | A history of medication or substance use | Stopping the medication or substance to see whether the tremor goes away |
A slow alternating tremor that
Often no family history of tremor and no lessening of tremor after drinking alcohol | A doctor's examination | |
A sometimes coarse or jerky tremor that is often inconspicuous In older adults who have difficulty looking down and eventually looking up, muscle stiffness, difficulty moving, early falls, and dementia | A doctor's examination | |
Intention tremor | ||
A slow tremor that
In some people, a family history of the disorder (as for Friedreich ataxia or spinocerebellar ataxias) | MRI of the brain | |
Medications or other substances, such as
| A history of use of a medication or other substance | Stopping the medication or substance to see whether the tremor goes away |
Complex tremors | ||
Disorders that affect many of the nerves outside the brain and spinal cord (polyneuropathies): | A tremor that
| Electromyography (stimulating muscles and recording their electrical activity) Other tests to identify the cause |
Functional (psychogenic) tremor (due to psychologic factors) | A tremor that
| A doctor's examination |
* Features include symptoms and results of the doctor's examination. Features mentioned are typical but not always present. | ||
† Although a doctor's examination is always done, it is mentioned in this column only if the diagnosis can sometimes be made by the doctor's examination alone, without any testing | ||
MRI = magnetic resonance imaging; SSRIs = selective serotonin reuptake inhibitors (a type of antidepressant). | ||
Testing
Brain imaging with magnetic resonance imaging (MRI) or computed tomography (CT) is done if
The person has other neurologic symptoms that suggest a brain disorder, such as a stroke, a tumor, or multiple sclerosis.
The tremor started suddenly or progresses rapidly.
Blood tests may be done to check for possible causes when the cause is unclear. Tests may include
Measurement of blood sugar
Tests to evaluate how well the thyroid and parathyroid glands, liver, and kidneys are functioning
Electromyography (stimulating muscles and recording their electrical activity) is rarely done. But if the cause is thought to be nerve damage, it may be done. This test can help distinguish tremor from other disorders, such as disorders of the peripheral nerves.
Treatment of Tremor
Any specific cause of the tremor is treated when possible—for example, by stopping a drug that is causing the tremor or by treating hyperthyroidism. Parkinson disease can be treated with . There is no effective treatment for tremors caused by a coordination (cerebellar) disorder, but physical therapy sometimes helps.
For mild tremor, no treatment is needed. If tremors become bothersome, some simple measures can help:
Grasping objects firmly and holding them close to the body to avoid dropping them
Avoiding uncomfortable positions
Using assistive devices, as instructed by an occupational therapist
Assistive devices may include rocker knives, utensils with large handles, and, particularly if the tremor is severe, button hooks, Velcro fasteners (instead of buttons or shoe laces), zipper pulls, straws, and shoe horns.
Certain medications (see table Some Causes and Features of Tremor) can cause or aggravate different types of tremor. Alcohol and other sedatives, sometimes only when given in low doses, may suppress essential and physiologic tremor.
Physiologic tremor
If many daily activities (such as using utensils and drinking from a glass at mealtime) become difficult or if the person's work requires steady hands, medications may help.
beta-blocker) may help.
Essential tremor
For some people, drinking alcohol in moderation may lessen the tremor, but doctors do not recommend this tactic as a treatment. Heavy drinking followed by suddenly stopping makes the tremor worse.
Benzodiazepines may be used to treat essential tremor if other medications are ineffective. However, they should be taken for only a short time if at all.
Intention tremors
Intention tremors are difficult to treat, but if the condition causing it can be corrected, the tremor may resolve.
If the condition cannot be corrected, a therapist may put wrist and ankle weights on the affected limb to reduce the tremor. Or people may be taught to brace the limb during activity. These measures sometimes help.
Deep brain stimulation
For deep brain stimulation , tiny electrodes are placed in the area of the brain involved in tremors—the basal ganglia (collections of nerve cells that help smooth out muscle movements—see figure Locating the Basal Ganglia). The electrodes send small amounts of electricity to the specific area of the basal ganglia responsible for the tremors and thus help relieve symptoms.
Deep brain stimulation is sometimes done when medications cannot control a severe, disabling tremor. Sometimes essential tremors or tremors due to Parkinson disease or another disorder require such treatment. Such treatments are used only when medications have been tried and have been not been effective. These treatments are available only at special centers.
Essentials for Older Adults: Tremor
Many older adults think that developing a tremor is a part of normal aging and may not seek medical attention. Nonetheless, older adults should talk to their doctor, who can ask them questions and do a physical examination to check for possible causes of tremor. Doctors may then recommend strategies or possibly medications to lessen the tremor.
Also, older adults are more likely to be taking medications that cause tremor and are more vulnerable to side effects of these medications. Thus, when prescribing such medications to older adults, doctors try to prescribe the lowest effective dose. Such a dose may be lower than the doses used to treat younger adults. Doctors, if possible, avoid using anticholinergic medications in older adults.
Tremor can significantly affect quality of life in older adults, interfering with their ability to function, especially if they have other physical or mental impairments. Physical and occupational therapists can provide simple coping strategies, and assistive devices may help older adults maintain quality of life.
Key Points
Tremors can be classified based on when they occur—whether at rest (resting tremor) or when moving (action tremor)—and action tremors can be classified as those occurring at the end of a movement toward a target or during any voluntary movement (kinetic tremor), when moving toward a target (intention tremor), or when holding a limb outstretched (postural tremor).
Most tremors are physiologic (normal) tremors, and some are essential tremor or are caused by other disorders.
Tremors that occur during rest are often caused by Parkinson disease.
Doctors can usually identify the cause based on the history and physical examination.
If a tremor begins suddenly or is accompanied by other neurologic symptoms, people should see a doctor right away.
If people are under 50, have a tremor, but do not have a family history of essential tremors, they should see a doctor soon.
The cause of the tremor is treated if possible, but otherwise, some simple strategies (such as avoiding circumstances that trigger tremors) and sometimes medications can help control the tremors.
