Essential tremor (ET)

Essential tremor (ET) is a very common but complex neurologic movement disorder. It is called "essential" because in the past, it had no known cause. Essential tremor does not develop from another neurological condition or as a side effect of medication. As many as 1 in 20 people older than age 40 and 1 in 5 people over 65 may have Essential tremor. There may be as many as 10 million people with Essential tremor in the United States, and many more worldwide.

Essential tremor usually affects the hands, but it may also affect the head and neck (causing shaking), face, jaw, tongue, voice (causing a shaking or quivering sound), the trunk and, rarely, the legs and feet. The tremor may be a rhythmic "back-and-forth" or "to-and-fro" movement produced by involuntary (unintentional) contractions of the muscle. Severity of the tremors can vary greatly from hour to hour and day to day. Some people experience tremor only in certain positions – this is called postural tremor. Tremor that worsens while writing or eating is called kinetic or action-specific tremor. Most people with Essential tremor have both postural and kinetic tremor.

Essential tremor cannot be prevented and it is is rarely debilitating. Severe cases can usually be treated with medication or with surgery.

Surgery
Surgery may be recommended when essential tremor is so severe that it causes disability. Thalamotomy is destruction of a portion of the area deep within the brain that receives sensory messages (thalamus). This procedure relieves essential tremor on one side of the body in approximately 75% of cases. Surgery on both sides of the thalamus rarely is performed because of the high risk for speech loss.

Deep brain stimulation (DBS) is another surgical option when severe essential tremor does not respond to medication. In this procedure, a small wire is implanted in the thalamus and connected to a device (called a neurostimulator) that is implanted under the collarbone. The neurostimulator sends electrical impulses along the wire to the thalamus to interrupt signals that cause tremor.

Patients can turn DBS on when needed and turn it off when tremors are infrequent (e.g., during sleep). About 85-90 percent of patients with essential termor undergoing treatment with deep brain stimulation obtain good or excellent relief of tremor.