essential tremor

Essential tremor (ET), also called benign tremor, familial tremor, and idiopathic tremor, is a medical condition characterized by involuntary rhythmic contractions and relaxations (oscillations or twitching movements) of certain muscle groups in one or more body parts of unknown cause. It typically is symmetrical, and affects the arms, hands, or fingers; but sometimes involves the head, vocal cords, or other body parts. Essential tremor is either an action (intention) tremor—it intensifies when ...