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.
Types of Tremors
Tremors are usually classified based on when they occur:
Tremors can also be classified by what causes them (see see Causes). Examples include the following:
Other important characteristics of tremors are
This 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. Such disturbances usually result from Parkinson disease. However, they can result from use of drugs that can affect this part of the brain, such as antipsychotic drugs and some drugs 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.
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 coarse.
Intention tremors may result from damage to the cerebellum, the part of the brain responsible for balance and coordination. Thus, cerebellar tremor and intention tremor may be used as synonyms.
Certain hereditary disorders that affect the cerebellum (called spinocerebellar ataxias) are a common cause of intention tremors, as is multiple sclerosis. Stroke, a tumor, alcoholism, and overuse of sedatives or anticonvulsants can also cause the cerebellum to malfunction, resulting in an intention tremor.
This type of tremor is 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 and physiologic (normal) tremor.
Complex tremor is a tremor that has features of more than one type of tremor. Common causes of complex tremors are psychologic factors and widespread nerve damage such as that caused by diabetes or Guillain-Barré syndrome.
Tremors can be normal (physiologic) or abnormal. Many disorders can cause tremor (see see Table 1: Some Causes and Features of Tremor).
Most commonly, tremors are
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
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.
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
The following symptoms are cause for concern:
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, but a delay of a week or two (or slightly longer if the tremor has developed over months or years) is usually not harmful.
If people are under 50 years old and do not have a family history of tremor, being evaluated by a doctor is important to make sure that the cause is not another disorder or a drug.
What the 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 below).
Doctors ask whether the tremor began gradually or suddenly, which body parts are affected, what triggers it (such as movement, rest, or standing), and what relieves or worsens it (such as alcohol, caffeine, stress, or anxiety). 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 (see see Table 1: Some Causes and Features of Tremor). They ask about tremors in close relatives. They review the drugs taken and ask about use of caffeine, alcohol, and recreational drugs (particularly whether the person recently stopped using such drugs).
Doctors do a physical examination, paying particular attention to the neurologic examination (including the way the person walks—see Physical Examination). Doctors note which body parts are affected by the tremor. They observe how fast the shaking movements are in various situations:
The quality of the person's voice may be observed when holding a long note.
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Doctors can usually identify the type of tremor based on its characteristics and results of the medical history and physical examination. For example, if the tremor develops gradually, it is usually physiologic or essential tremor. If a postural tremor starts more suddenly, the cause may be 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.
Brain imaging with magnetic resonance imaging (MRI) or computed tomography (CT) is done if
For people with postural tremors, testing may also include blood tests to check for possible causes. Tests may include measurement of blood sugar and tests to evaluate how well the thyroid and parathyroid glands, liver, and kidneys are functioning.
Any specific cause 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 levodopa and other drugs.
For mild tremor, no treatment is needed. If tremors become bothersome, some simple measures can help:
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.
For physiologic or essential tremor, eliminating or minimizing the trigger may lessen the tremor. For example, avoiding caffeine, getting enough sleep, and minimizing stress may help. 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. 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, drug therapy may help. It may include a beta-blocker (such as propranolol), the anticonvulsant primidone, or both. For physiologic tremor, occasionally taking a low dose of a benzodiazepine (a sedative), such as lorazepam, may help lessen the tremor.
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:
Tiny electrodes are placed in the area of the brain involved in tremors. The electrodes deliver a painless shock to block the impulses causing tremors. Deep brain stimulation is sometimes done when drugs cannot control a severe, disabling tremor. Sometimes essential tremors or tremors due to Parkinson disease or another disorder require such treatment. Such treatments are available only at special centers.
Essentials for Older People
Many older people think that developing a tremor is a part of normal aging and may not seek medical attention. Nonetheless, older people 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 drugs to lessen the tremor.
Also, older people are more likely to be taking drugs that cause tremor and are more vulnerable to side effects of these drugs. Thus, when prescribing such drugs to older people, doctors try to prescribe the lowest effective dose. Such a dose may be lower than the doses used to treat younger adults.
Tremor can significantly affect quality of life in older people, 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 people maintain quality of life.
Last full review/revision August 2007 by Hector A. Gonzalez-Usigli; Alberto Espay