|
Tourette syndrome (TS) is characterized by motor and vocal tics associated with varying degrees of psychiatric comorbidity. Prevalence of the syndrome is estimated to be 0.4-1/100 in the general population. The disease involves several motor tics and at least one vocal tic present for at least one year and appearing before 18 years of age, in the absence of an identifiable cause. Patients also have variable psychiatric comorbidity, including obsessive-compulsive disorder (OCD), attention deficit-hyperactivity disorder (ADHD), panic and rage attacks, self-mutilation and anxiety disorders. Onset is during childhood and the course is characterized by successive periods of relative worsening and improvement in tics. Improvement is observed at the end of the 2nd decade of life in most patients but symptoms may persist in adulthood in about one third of patients. The cause of Tourette syndrome is unknown but genetic susceptibility and certain environmental factors appear to play a role. Pathophysiologically, dysfunction of the dopaminergic system, and of the neuronal networks in the associative and limbic areas of the basal ganglia and the prefrontal cortex, has been suggested. These dysfunctions are thought to be involved in abnormal migration of GABAergic and cholinergic interneurons. Diagnosis is clinical and based on the symptoms defined in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR). Differential diagnoses include myoclonia, dystonia, chorea, paroxysmal dyskinesia, hemiballism, hemifacial spasm, stereotypy, mannerisms, compulsions, akathisia, restless legs syndrome and epilepsy. Treatment of Tourette syndrome and of severe tics is often difficult and requires and multidisciplinary approach (neurologist, psychiatrist, psychologist and social workers). In mild cases, patient information and psychological management are usually recommended. Medicinal treatments, including neuroleptics, are essential in patients with moderate and severe forms of the disease. Recently, cognitive-behavioral therapy (CBT) has been found to be useful in the treatment of tics. For certain isolated tics, injection of botulinum toxin may prove beneficial. Psychiatric comorbidity, when present, often warrants specific treatment. In very severe forms of Tourette syndrome, treatment by deep brain stimulation (DBS) of the associative and limbic territories of the thalamus or pallidum is currently under evaluation in a multi-center protocol. Preliminary results are encouraging. About two thirds of patients recover once they reach adulthood, while the remaining third continue to suffer from tics with varying degrees of social and functional impairment. |