Dopamine transporter density of the basal ganglia assessed with [ 123I]IPT SPECT in drug-naive children with Tourette's disorder

There is evidence that abnormalities in the dopaminergic system involving the dopamine transporter (DAT) are involved in the pathophysiology of Tourette's disorder (TD) from previous studies using [ 123I]2β-carbomethoxy-3-(4-iodophenyl)tropane ([ 123I]β-CIT) and single photon emission tomography (SPECT). However, because those studies were performed in medicated adult patients with TD, we decided to compare DAT densities in nine drug-naive children with TD and eight normal children. The children with TD did not suffer from associated psychiatric problems such as obsessive–compulsive symptoms, attention deficit hyperactivity disorder, anxiety, depression and developmental difficulties. We performed brain SPECT 2 h after the intravenous administration of I-123N-(3-iodopropen-2-yl)-2β-carbomethoxy-3beta-(4-chlorophenyl)tropane ([ 123I]IPT) and carried out both quantitative and qualitative analyses using the obtained SPECT data, which were reconstructed for the assessment of the specific/non-specific DAT binding ratio in the basal ganglia. We then investigated the correlation between the severity of tics in children with TD assessed with the Yale Global Tic Severity Scale (YGTSS) and the specific/non-specific DAT binding ratio of the basal ganglia. Drug-naive children with TD showed a significantly increased specific/non-specific DAT binding ratio in the basal ganglia compared with normal children that did not correlate significantly with the severity of tics. Our results with drug-naive children with TD between the ages of 6 and 12 may help to clarify previous findings concerning DAT binding in adult patients with TD and suggest that DAT densities may be associated directly with the pathophysiology of TD, regardless of disease progress or drug effect.