A tic is a sudden, repetitive, stereotyped, involuntary motor (e.g., blinking, grimacing) or vocal (e.g., throat clearing, grunting, barking) movement. Tics can also be classified into simple (e.g., nose twitching, grunting) or complex (e.g., head shaking, trunk flexion, echolalia, neologism). Tics are stereotypical (repeat same way each time) and also variable, as new tics surface. Often preceded by a premonitory sensation. Patients may be able to suppress tics (partial voluntary control).

• Tourette syndrome (TS): Motor and vocal tics intermittent over ≥1 year
• Chronic multiple motor or vocal tic disorder: Motor or vocal tics, but not both, ≥1 year
• Transient tic disorder: Motor and/or vocal tics that have been present ≥2 weeks, ≤1 year
• Tic disorder not otherwise specified (NOS): Motor and/or vocal tics that do not fit a specific tic disorder
• Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus (PANDAS): Debatable entity described in 1998. In theory, group A β hemolytic Streptococcal (GABHS) infection evokes antibodies that cross-react with the basal ganglia causing tics in some individuals.