Increased ventral striatal monoaminergic innervation in Tourette syndrome

Background: Excessive striatal dopaminergic innervation is suggested to underlie Tourette syndrome (TS). Prior imaging and postmortem studies yield conflicting data. Methods: The authors used PET with the type 2 vesicular monoamine transporter ligand [C-11] dihydrotetrabenazine (DTBZ) to quantify striatal monoaminergic innervation in patients with TS (n = 19) and control subjects (n = 27). Compartmental modeling was used to determine blood to brain ligand transport (K-1) and tissue to plasma distribution volume ( a measure of ligand binding) during continuous infusion of DTBZ. TS data were compared with control data using predefined regions of interest and on a voxel by voxel basis. Results: There were no significant differences in ligand binding or ligand transport between patients with TS and control subjects in the dorsal striatum. With voxel by voxel analysis, there was increased DTBZ binding in the right ventral striatum. Conclusions: Previously reported differences between patients with TS and control subjects in dorsal striatal dopamine terminal markers may reflect medication-induced regulation of terminal marker expression or be the result of intrinsic differences in striatal dopaminergic synaptic function. Increased right ventral striatal DTBZ binding suggests that abnormal ventral striatal dopaminergic innervation may underlie tics.