Essential tremor is a neurological disorder characterized by shaking of hands (and sometimes other parts of the body including the head), evoked by intentional movements. The exact incidence is unknown, but it is presumed to be the most common type of tremor and also the most commonly observed movement disorder.
Half of the cases are due to gene mutation and transmitted dominantly. The rest are idiopathic. No identifiable and consistent structural abnormality has yet been demonstrated to exist in the nervous system of every person with ET.
Essential tremor (ET) generally presents as a rhythmic tremor (4-12 Hz) that is present only when the affected muscle is exerting effort (i.e., it is not present at rest). Any sort of physical or mental stress will tend to make the tremor worse. It is typical for the tremor to worsen in "performance" situations, such as attempting to drink out of a cup, or concentrating on some mental task. ET-related tremors do not occur during sleep. In severe cases, ET can interfere with a person's ability to perform tasks of daily living, including feeding, dressing, and activities of personal hygiene. ET is progressive in most cases (sometimes rapidly, sometimes very slowly) but significant disability is rare.
Usually the diagnosis is established on clinical grounds. Tremors can start at any age, from birth through advanced ages. Any voluntary muscle in the body may be affected, though it's most commonly seen in the hands and arms and slightly less commonly in the neck (causing the patient's head to shake), eyelids, larynx, tongue, trunk, and legs. ET does sometimes occur in combination with other neurological disorders such as dystonia. However, there is no clear evidence that having ET predisposes a person to one of these disorders.
The two medications that are prescribed most commonly for control of ET symptoms are the anticonvulsant Primidone (Mysoline) and the beta-blocker propranolol (Inderal). People with ET often improve with the ingestion of alcohol.
Surgical treatments (which are generally reserved for the most severe cases) include botulism toxin injections into the affected muscles, thalamotomy and deep brain stimulation – the insertion of a brain pacemaker.