What is Tremor?

Tremor is an involuntary, rhythmic muscle contraction leading to shaking movements in one or more parts of the body. It is a common movement disorder that most often affects the hands but can also occur in the arms, head, vocal cords, torso, and legs. Tremor may be intermittent (occurring at separate times, with breaks) or constant. It can occur sporadically (on its own) or happen as a result of another disorder.

Tremor is most common among middle-aged and older adults, although it can occur at any age. The disorder generally affects men and women equally.

Tremor is not life threatening. However, it can be embarrassing and even disabling, making it difficult or even impossible to perform work and daily life tasks.

WHAT CAUSES TREMOR?

Generally, tremor is caused by a problem in the deep parts of the brain that control movements. Most types of tremor have no known cause, although there are some forms that appear to be inherited and run in families.

Tremor can occur on its own or be a symptom associated with a number of neurological disorders, including:

• multiple sclerosis
• stroke
• traumatic brain injury
• neurodegenerative diseases that affect parts of the brain (e.g., Parkinson’s disease).

Some other known causes can include:

• the use of certain medicines (particular asthma medication, amphetamines, caffeine, corticosteroids, and drugs used for certain psychiatric and neurological disorders)
• alcohol abuse or withdrawal
• mercury poisoning
• overactive thyroid
• liver or kidney failure
• anxiety or panic

HOW IS TREMOR DIAGNOSED

Tremor is diagnosed based on a physical and neurological examination and an individual’s medical history. During the physical evaluation, a doctor will assess the tremor based on:

• whether the tremor occurs when the muscles are at rest or in action
• the location of the tremor on the body (and if it occurs on one or both sides of the body)
• the appearance of the tremor (tremor frequency and amplitude).
• Medications and other treatment methods
• While drugs can be effective for some people, approximately 50 percent of individuals do not respond to medication. In order to develop assistive and rehabilitative tremor-suppressing devices for people with essential tremor, researchers are exploring where and how to minimize or suppress tremor while still allowing for voluntary movements.
• Many people with essential tremor respond to ethanol (alcohol); however, it is not clear why or how. NINDS researchers are studying the impact of ethanol on tremor to determine the correct dosage amount and its physiological impact on the brain and whether other medications without the side effects of ethanol can be effective.
• Other NIH researchers hope to identify the source of essential tremor, study the effects of currently available tremor-suppressant drugs on the brain, and develop more targeted and effective therapies.