Essential tremor
Essential tremor (ET), also called benign tremor, familial tremor, and idiopathic tremor, is a disorder of the nervous system that causes the patient to experience involuntary movements, producing involuntary and rhythmic jerks. It often affects the hands, although it can sometimes affect the voice or the head. Although it is the most common type of tremor, its causes have not yet been identified. It is not usually a dangerous condition, but essential tremor can progress over time, worsening the patient's condition.