Functional imaging of dopaminergic neurotransmission in Tourette syndrome.

Tourette syndrome (TS) is a heritable neuropsychiatric disorder that presents in childhood with a constellation of motor and nonmotor symptoms. Many of the earliest efforts to elucidate the anatomic substrate of TS focused on the contribution of the basal ganglia to the disorder. Simultaneously, however, a substantial body of evidence has accrued to implicate dysfunction of regions outside the basal ganglia in the generation of tics. In particular, while activation studies have shown evidence for cortico-striato-thalamo-cortical circuit abnormalities in TS, several other functional imaging reports have suggested that a dysregulation of striatal dopamine both at the presynaptic and postsynaptic level may play a primary role in TS. In addition, new radiotracers allowing for the investigation of extrastriatal dopamine seem to support the involvement of cortical structures as well.