(See also Overview of Movement Disorders Overview of Movement Disorders Every body movement, from raising a hand to smiling, involves a complex interaction between the central nervous system (brain and spinal cord), nerves, and muscles. Damage to or malfunction... read more .)
Types of Tremors
Tremors can be
Normal (physiologic)
Abnormal (pathologic), caused by a disorder or drug
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
Intention tremor: Triggered by movement toward a target (for example, reaching for a glass)
Kinetic tremor: Appearing at the end of a movement toward a target or during any voluntary movement, such as moving the wrists up and down or closing and opening the eyes
Postural tremor: Triggered by holding a limb outstretched in one position
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 or drug)
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
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
Consume caffeine
Take certain drugs, including theophylline and albuterol (which are used to treat asthma Drugs for Preventing and Treating Asthma Drugs allow most people with asthma to lead relatively normal lives. Most of the drugs used to treat an asthma attack can be used (often in lower doses) to prevent attacks. (See also Asthma... read more
and chronic obstructive pulmonary disease Treatment Chronic obstructive pulmonary disease is persistent narrowing (blocking, or obstruction) of the airways occurring with emphysema, chronic obstructive bronchitis, or both disorders. Cigarette... read more 
, or COPD), corticosteroids, or recreational drugs (such as cocaine Cocaine Cocaine is an addictive stimulant drug made from leaves of the coca plant. Cocaine is a strong stimulant that increases alertness, causes euphoria, and makes people feel powerful. High doses... read more or amphetamines Amphetamines Amphetamines are stimulant drugs that are used to treat certain medical conditions but are also subject to abuse. Amphetamines increase alertness, enhance physical performance, and produce euphoria... read more ) Have certain disorders, such as an overactive thyroid gland (hyperthyroidism Hyperthyroidism Hyperthyroidism is overactivity of the thyroid gland that leads to high levels of thyroid hormones and speeding up of vital body functions. Graves disease is the most common cause of hyperthyroidism... read more
) 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 Introduction to Symptoms of Brain, Spinal Cord, and Nerve Disorders ). 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 Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more , 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 Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more or disorders that cause the same symptoms as Parkinson disease (parkinsonism Parkinsonism Parkinsonism refers to symptoms of Parkinson disease (such as slow movements and tremors) that are caused by another condition. Parkinsonism is caused by brain disorders, brain injuries, or... read more )
However, resting tremors can also 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.
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 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.
Common causes of intention tremor include
Certain hereditary disorders that affect the cerebellum (called spinocerebellar ataxias Spinocerebellar ataxias Coordination disorders often result from malfunction of the cerebellum, the part of the brain that coordinates voluntary movements and controls balance. The cerebellum malfunctions, causing... read more )
Other disorders and drugs can also cause the cerebellum to malfunction, resulting in an intention tremor. They include
Overuse of sedatives or antiseizure drugs
Postural 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
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 Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Symptoms of diabetes may... read more or Guillain-Barré syndrome Guillain-Barré Syndrome (GBS) Guillain-Barré syndrome is a form of polyneuropathy causing muscle weakness, which usually worsens over a few days to weeks, then slowly improves or returns to normal on its own. With treatment... read more
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 Friedreich ataxia Coordination disorders often result from malfunction of the cerebellum, the part of the brain that coordinates voluntary movements and controls balance. The cerebellum malfunctions, causing... read more and spinocerebellar ataxias Spinocerebellar ataxias Coordination disorders often result from malfunction of the cerebellum, the part of the brain that coordinates voluntary movements and controls balance. The cerebellum malfunctions, causing... read more
Due to use of certain drugs or exposure to certain toxic substances
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 or a drug.
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 Some Causes and Features of Tremor 
).
Doctors ask about the tremor:
Whether the tremor began gradually or suddenly
Which body parts are affected
What triggers it (such as movement, rest, or standing)
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 Types of Tremors 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... read more . 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 Neurologic Examination When a neurologic disorder is suspected, doctors usually evaluate all of the body systems during the physical examination, but they focus on the different parts of the nervous system. Examination... read more (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 postural 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
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 Electromyography and Nerve Conduction Studies Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more 
(stimulating muscles and recording their electrical activity) is rarely done. But if the cause is thought to be nerve damage, it may be done.
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 levodopa and other drugs Treatment Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more .
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
Avoiding other circumstances that trigger the tremor (such as consumption of caffeine, lack of sleep, or fatigue)
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 drugs (see table Some Causes and Features of Tremor 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
Eliminating or minimizing the trigger may lessen physiologic tremor. For example, avoiding caffeine, getting enough sleep, and minimizing stress may help.
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.
People with a physiologic tremor and anxiety may benefit from taking a low dose of a benzodiazepine (a sedative), such as lorazepam. However, these drugs should be taken only occasionally.
If a physiologic tremor is worsened by taking prescribed drugs that are necessary or by feeling very anxious, propranolol (a beta-blocker Adrenergic blockers High blood pressure is very common. It often does not cause symptoms; however, high blood pressure can increase the risk of stroke, heart attack, and heart failure. Therefore, it is important... read more ) 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.
Antiseizure drugs (primidone, topiramate, or gabapentin) or propranolol may also be used if needed to control the tremor.
Benzodiazepines may be used to treat essential tremor if other drugs are ineffective.
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 this procedure, 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). 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 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 used only when drug therapy has been tried and has been not been effective. These treatments are available only at special centers.
Essentials for Older People: Tremor
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. Doctors, if possible, avoid using anticholinergic Anticholinergic: What Does It Mean? drugs in older people.
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 Treatment , and assistive devices may help older people 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 drugs can help control the tremors.
