Tourette's syndrome: from behaviour to biology.

Tourette's syndrome (TS) is a chronic neuropsychiatric disorder characterised by motor and vocal tics. Diagnosis is based solely on clinical criteria. The prevalence of this syndrome is estimated to be between one and ten per 1000 children and adolescents and the outcome is generally favourable; most patients improve by their late teens or early adulthood. Affected individuals are at increased risk of various comorbid neurobehavioural problems, the negative effects of which commonly exceed those of tics. Despite evidence that TS is an inherited disorder, the exact genetic abnormality is unknown. Environmental factors might have an important role in the expression of tics, and a poststreptococcal autoimmune cause has been proposed but is unproven. Brain imaging, neurophysiological, and post-mortem studies support involvement of cortical-striatal-thalamocortical pathways, but the definitive pathophysiological mechanism or neurotransmitter abnormality is unknown. Recent evidence, however, suggests a prefrontal dopaminergic abnormality. Traditional neuroleptics are the standard treatment for TS, but there is increasing interest in non-neuroleptic drugs, behavioural therapies, and surgical approaches.