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10 Dysfunction of dopamine neurotransmission is strongly implicated in this process, with current evidence pointing to low tonic synaptic dopamine levels and excessive phasic release of dopamine in the basal ganglia. TS is thought to result from a developmental failure of inhibitory function within the frontal-subcortical circuits governing voluntary movements, 9 possibly leading to impaired surround-off inhibition (the ability to suppress unwanted movements). With very high comorbidity rates of both attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD), TS may represent a multifaceted developmental neuropsychiatric brain disorder. Tics lasting less than 1 year are termed transient tic disorder. 6, 7 When chronic tics of both types cannot be identified, the terms chronic motor tic disorder and chronic vocal tic disorder are used. Diagnostic criteria include presence of both motor and vocal tics, onset in childhood, fluctuations in tic types and severity, and duration of at least one year. 3 – 5Ĭhronic tics are the characteristic feature of Tourette’s syndrome (TS). Compulsions frequently occur in association with tics, can sometimes be difficult to distinguish from complex motor tics, but typically differ by being done in response to an obsession, being performed to ward off future problems, or being done according to certain rules (ritualistic). Some tics are slow or twisting in character resembling dystonia and are termed “dystonic tics.” Contrary to dystonic tics, dystonia per se tends to be slower and leads to more sustained disturbances in posture of a limb, the neck, or trunk. Stereotypies are typically seen in patients with autism, mental retardation, Rett syndrome, psychosis, or congenital blindness and deafness. Complex motor tics need to be distinguished from stereotypies that are longer lasting, more stereotyped movements (eg, body rocking, head nodding, and hand/wrist flapping) or sounds (eg, moaning, yelling) that occur over and over again in a more continuous, less paroxysmal fashion. Simple tics are commonly accompanied by complex tics and associated with premonitory sensations or suppressibility. Simple motor tics may need to be differentiated from myoclonic jerks, which are not typically repetitive in the same body part like tics.