Tremors
Tremor is the uncontrollable shaking of a body part. Nearly everyone experiences tremor at some point, most often as a result of fear or excitement. However, persistent uncontrollable shaking is a common symptom of neurological disorders that destroy nerve tissue, such as Parkinson's disease or multiple sclerosis. Tremor may also occur after stroke or head injury. Other tremors appear without any underlying illness. For example, essential tremor (ET) is caused by abnormalities in areas of the brain that control movement. ET alone affects approximately 5 million people in the United States.

Tremor is the most common of all involuntary movements. Although tremor can affect various body parts including the hands, head, facial structures, vocal cords, trunk, and legs, it most frequently occurs in the hands.