Brain structure in pediatric Tourette syndrome

Abstract

Previous studies of brain structure in Tourette syndrome (TS) have produced mixed results, and most had modest sample sizes. In the present multicenter study, we used structural magnetic resonance imaging (MRI) to compare 103 children and adolescents with TS to a well-matched group of 103 children without tics. We applied voxel-based morphometry methods to test gray matter (GM) and white matter (WM) volume differences between diagnostic groups, accounting for MRI scanner and sequence, age, sex and total GM+WM volume. The TS group demonstrated lower WM volume bilaterally in orbital and medial prefrontal cortex, and greater GM volume in posterior thalamus, hypothalamus and midbrain. These results demonstrate evidence for abnormal brain structure in children and youth with TS, consistent with and extending previous findings, and they point to new target regions and avenues of study in TS. For example, as orbital cortex is reciprocally connected with hypothalamus, structural abnormalities in these regions may relate to abnormal decision making, reinforcement learning or somatic processing in TS.

Figure 1

Subject flow diagram. MRI, magnetic resonance imaging; TS, Tourette syndrome. PowerPoint slide

Figure 2

The largest cluster from the contrast showing where WM volume is lower in TS than in the control group (5.2 ml, p_FDR =0.001; see Table 2). The t statistic is shown in color (thresholded at t⩾3.0), laid over the average MP-RAGE image from the entire sample (in grayscale). The crosshairs show (−12, 49.5, −16.5)_MNI, left medial orbital gyrus, BA11. The peak t-value from this contrast, t₁₉₃=5.95, is at (−13.5, 31.5, −22.5)_MNI in left medial orbital gyrus, BA13, near the red ‘X’ in the sagittal image. Supplementary Figure 2 shows the other significant cluster from this contrast, the homologous area on the right side of the brain. FDR, false discovery rate; MNI, Montreal Neurological Institute template brain coordinates; TS, Tourette syndrome; WM, white matter. PowerPoint slide

Figure 3

Largest clusters showing greater GM volume in TS compared with controls. (a) Largest cluster from GM>control contrast, in left pulvinar nucleus of thalamus (see Table 2 and legend to Figure 2). (b) The second largest cluster from the GM>control contrast, with the crosshairs at (4, 6, −6)_MNI in hypothalamus. In this figure, all voxels with t⩾3.0 are highlighted in color to better visualize the underlying anatomy. GM, gray matter; MNI, Montreal Neurological Institute template brain coordinates; TS, Tourette syndrome. PowerPoint slide