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A spasmodic muscular contraction, most commonly involving the face, mouth, eyes, head, neck, or shoulder muscles. The spasms may be tonic or clonic. The movement appears purposeful, is often repeated, is involuntary, and can be inhibited for a short time.
Children between the ages of 5 and 10 years are esp. likely to develop tics.
SEE: Tourette syndrome
In most cases, the cause is unknown. In some people, the tic is worsened by anxiety and nervous tension.