Tremor is an unintentional, rhythmic, muscle movement involving to-and-fro movements of one or more parts of the body. Most tremors occur in the hands, although they can also affect the arms, head, face, voice, torso, and legs. Tremor may occur at separate times or be constant.
There are two main categories of tremor:
- Resting tremor occurs when the muscle is relaxed, such as when the hands are resting on the lap
- Action tremor occurs with the intended movement of a muscle
Ther are more than 20 types of tremor. Some of the most common are:
- Essential tremeor usually appears on both sites of the body and is often noticed more in the dominant hand
- Dystonic tremor can affect any muscle in the body and usually is associated with abnormal body postures due to forceful muscle spasms or cramps
- Parkinsonian tremor, with shaking of one or both hands at rest and may also affect the lips, face, and legs
Generally, tremor is caused by a problem in the deep parts of the brain that control movements. Some forms of tremor are inherited and run in families, while others have no known cause. Sometimes tremor is a symptom of another neurological disorder or a side effect of certain drugs, but the most common form occurs in otherwise healthy people. Other causes of tremor can include the use of certain medicines, alcohol use disorder or withdrawal, and an overactive thyroid. Tremor may occur at any age but is most common in middle-aged and older adults.
There is no cure for most forms of tremors. In some individuals, the symptoms may be mild enough to not require treatment. The appropriate treatment depends on accurate diagnosis of the cause. Drug treatment may include beta-blocking drugs, anti-seizure medications, tranquilizers, botulinum toxin injections, and drugs such as levodopa or carbidopa to treat tremor associated with Parkinson's disease. Deep brain stimulation is the most common form of surgical treatment for parkinsonian tremor, essential tremor, and dystonia. Eliminating tremor "triggers" such as caffeine and other stimulants from the diet is often recommended. Physical therapy may help to reduce tremor and improve coordination and muscle control for some individuals.
Although tremor is not life-threatening, it can be embarrassing to some people and make it harder to perform daily tasks such as working, bathing, eating, and getting dressed. The symptoms of essential tremor usually worsen with age.
Researchers at the National Institute of Neurological Disorders and Stroke (NINDS, a unit of the National Institutes of Health) are working to better understand the underlying brain functions that casue tremor, indentify the genetic factors that make individuals more susceptible to tremor, and develop new and better treatment options. Researchers are working to identify structural and functional changes in the brain using non-invasive neuroimating techniques. Other researchers hope to identify the genetic abnormalities in the development of essential tremor. Additional NINDS research is investigating the impact of ethanol to determing the correct dosage amount for essential tremor and whether other medications without the side effects of ethanol can be effective. Information from the National Library of Medicine’s MedlinePlus Tremor