When People Tremble

At some time, everyone unintentionally shakes or trembles (has a tremor). Such tremors are normal (physiologic). In most people, they are too slight to be noticed. But some things cause normal tremors to become noticeable---for example, holding the arms out from the side, consuming foods or beverages with caffeine, or feeling stressed, anxious, or tired. When people who are used to consuming caffeine or alcohol suddenly stop, a normal tremor may become more noticeable. An overactive thyroid gland (hyperthyroidism) may also make a normal tremor more noticeable.

Most tremors are not serious, although they may be troublesome. Some tremors are symptoms of disorders. For example, they may indicate brain damage, as occurs in Parkinson's disease, or a problem with the nerves that supply certain muscles.

Tremors that are caused by disorders or drugs are classified by when they occur: when resting, when moving, when performing a precise and purposeful action, or when holding a position for a long time. These tremors may be fast or slow (frequency). Their range of movement may be narrow (fine) or wide (coarse). Tremors may be constant or occur once in a while.

Resting tremor is a slow, coarse tremor that occurs when the muscles are at rest. An arm or a leg shakes even when the person is completely relaxed. Resting tremor may be caused by Parkinson's disease or certain drugs, such as lithium (used to treat mood disorders) or antipsychotic drugs (used to treat loss of contact with reality). Resting tremor, although sometimes embarrassing, usually interferes slightly if at all with movements, such as drinking a glass of water or eating soup.

Action tremor occurs during movement, such as writing or using utensils. It usually stops when the movement is stopped. Action tremor may be caused by using certain drugs, such as prednisone and some drugs used to treat asthma (beta-adrenergic agonists), or by disorders, such as essential tremor.

Intention tremor is a relatively slow, broad tremor that occurs at the end of a precise, purposeful movement, such as trying to press a button or put a key in a lock. Intention tremor may result from malfunction of or damage to areas of the brain that coordinate movements (the cerebellum or clusters of nerve cells connected with the cerebellum). Excessive use of alcohol can cause intention tremor.

Postural tremor occurs when part of the body is held in one position, for example, when an arm is held out from the side. The tremor usually stops when the body is relaxed. It may be caused by using certain drugs (such as lithium or thyroid hormones).

Any tremor that is easily noticed should be evaluated by doctors. Doctors can usually identify the type of tremor by its characteristics, including when it occurs. Tests done to identify the cause depend on the type of tremor, and treatment depends on the cause.