R. A. Weeks

PET studies of the presynaptic and postsynaptic dopaminergic system in Tourette's syndrome.

Dysfunction of the dopaminergic pathway has been postulated to underlie the symptomatology of Tourettes syndrome. Presynaptic functional integrity of dopaminergic terminals was assessed with 18F-dopa PET in 10 patients with Tourettes syndrome, three of whom were drug free and seven of whom were on neuroleptic treatment. Dopamine D2 receptor site density was measured with 11C-raclopride PET in a further group of five drug free patients with Tourettes syndrome. Mean caudate and putamen 18F-dopa influx constants were similar in patients with Tourettes syndrome and controls, and there was no difference in striatal 18F-dopa uptake between the treated and untreated Tourettes syndrome groups. Mean caudate and putamen 11C-raclopride binding potentials in patients with Tourettes syndrome were also similar to control values. The findings suggest that striatal metabolism of exogenous levodopa and the density of striatal D2 receptors are both normal in patients with Tourettes syndrome and that Tourettes syndrome does not arise from a primary dysfunction of dopaminergic terminals.