Tic disorder is a neuropsychiatric disorder that begins in childhood and adolescence and has a clear genetic predisposition. It is characterized by involuntary, repetitive, rapid muscle movement twitches and vocal twitches in one or more parts of the body, and may be accompanied by inattention, hyperactivity, compulsive movements and thinking or other behavioral symptoms. The duration of tic disorders varies and can be transient or chronic, or even lifelong. Twitching usually starts with motor twitching of the eyes, face or head and progresses to the neck, shoulders, limbs or trunk, often progressing from simple to recurrent. Eye twitching is the first symptom in 38% to 59% of cases, and vocal twitching is the first symptom in 12% to 37% of cases. Various forms of twitching can be controlled by the will for a few moments, disappear during sleep, and worsen during emotional stress, excitement, or fatigue.