Tremor is an unintentional and uncontrolled rhythmic muscle movement of one or more parts of the body. It most often affects the hands, but can also affect the arms, head, face, voice, trunk and legs. In some people tremor is due to a neurological disorder; it may also be due to a side effect of certain drugs. Tremor is not the same as muscle spasms or twitches.
Tremor is typically caused by problems in the part of the brain that control muscles throughout the body or the part of the brain that controls muscles in particular areas such as the hands. Some neurological disorders can produce tremor, such as: multiple sclerosis, stroke, traumatic brain injury and neurodegenerative diseases that damage or destroy parts of the brainstem or the cerebellum. Other causes of tremor include the use of certain drugs, alcohol abuse or withdrawal, overactive thyroid or liver failure. Some forms of tremor are genetic, while others have no known cause.