Subcortical volumes in girls with Tourette syndrome - Support for a gender effect

Objective: To test whether girls with Tourette syndrome (TS) show subcortical morphology that differentiates them from control subjects. Methods: MRI-based subcortical assessment was completed on 19 girls with TS age 7 to 15 years, 11 with TS only, and 8 with TS plus attention deficit hyperactivity disorder (TS + ADHD), and on 21 age- and sex-matched controls. The structures measured were the caudate, putamen, globus pallidus, and lateral ventricle volumes. Whole-brain-corrected volumes and asymmetry indices were compared using two- and three-group designs (i.e., TS versus control; TS-only versus TS + ADHD versus control). Results: Two-group comparisons demonstrated no robust significant differences between girls with TS and gender-matched controls. Three-group comparisons demonstrated that TS-only subjects had significantly small lateral ventricles compared with TS + ADHD and control subjects. Because the two-group comparisons of the current study differed from previous reports of putamen asymmetry index as a marker for TS, retrospective comparisons with data from boys were performed. These additional comparisons showed that girls with TS had putamen asymmetry indices similar to those of boys with TS; however, control girls also showed those same patterns. Conclusions: Basal ganglia volume and asymmetry differences do not distinguish the girls with TS from matched controls. Gender differences confound the association between putamen asymmetry and TS. Although the numbers are small and the clinical significance is unclear, this study further indicates that girls with TS-only have smaller lateral ventricular volumes than control subjects and those with TS + ADHD.