Abnormal, involuntary, discrete, repetitive movements or sounds that change over time, tics are classified as motor or phonic and further subclassified as simple or complex. Motor tics may be brief jerks, more sustained twisting movements, or long-sustained muscle contractions; phonic tics produce a sound from the mouth or nose. Common motor tics include eye blinking and shoulder shrugging; common phonic tics include sniffing and throat clearing. Tics tend to occur in the setting of normal activity or speech but outside of normal context or at inappropriate times. Common in childhood, up to 25% of children have tics at some point during development, and they are more common among children needing special education. Persistent (chronic) tic disorders, characterized by the presence of tics for at least 1 year, affect approximately 1% of youth. Tourette syndrome (TS), the most common form of persistent tic disorder, is characterized by the presence of multiple...
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