Tremor

An involuntary, rhythmic, oscillating movement in the muscles of part of the body, most commonly those of the hands, feet, jaw, tongue, or head. Tremor is the result of rapidly alternating muscle contraction and relaxation. Occasional tremors are experienced by most people and are due to increased production of the hormone adrenaline (epinephrine). A slight, persistent tremor is common in elderly people. Essential tremor, which runs in families, is a slight-to-moderate tremor that may be temporarily relieved by consuming a small amount of alcohol or by taking beta-blocker drugs. Coarse tremor (4–5 muscle movements per second), which is present at rest but reduced during movement, is often a sign of Parkinson’s disease. An intention tremor (tremor that is worse on movement of the affected part) may be a sign of cerebellar ataxia. Tremor may also be caused by multiple sclerosis, Wilson’s disease, mercury poisoning, thyrotoxicosis, or hepatic encephalopathy; drugs, such as amfetamines and caffeine; and withdrawal from drugs, including alcohol.