Thinning of sensorimotor cortices in children with Tourette syndrome

Abstract

The basal ganglia portions of cortico-striato-thalamo-cortical (CSTC) circuits have consistently been implicated in the pathogenesis of Tourette syndrome, whereas motor and sensorimotor cortices in these circuits have been relatively overlooked. Using magnetic resonance imaging, we detected cortical thinning in frontal and parietal lobes in groups of Tourette syndrome children relative to controls. This thinning was most prominent in ventral portions of the sensory and motor homunculi that control the facial, orolingual and laryngeal musculature that is commonly involved in tic symptoms. Correlations of cortical thickness in sensorimotor regions with tic symptoms suggest that these brain regions are important in the pathogenesis of Tourette syndrome.

Figure 1

Cortical thickness group differences. (a) Statistical P maps of the effect of diagnosis on cortical thickness with intelligence quotient statistically controlled. P maps are color-coded as indicated (also applies to Fig. 2a,b). Regions in red are statistically significant (uncorrected, P < 0.05). Regions in purple or pink do not approach significance (P approaching 1.0). Central, precentral and postcentral sulci, which bound the precentral and postcentral gyri, and the inferior frontal sulcus and Sylvian fissure are superimposed in black. Broca’s area, BA; occipital cortex, Occ; parietal cortex, P; postcentral gyrus, PostCG; precentral gyrus,PreCG; subgenual, SG; temporal cortex, T. (b) Cortical thickness differences in millimeters. Maps of differences between the entire group of Tourette syndrome and control subjects in thickness of gray matter (Tourette syndrome coded 1, controls coded 0 for all maps shown) showing differences in gray matter (in millimeters) between the Tourette syndrome and control subjects, as indicated by the color bar. Warmer colors (<0 on the color bar) indicate regions where the gray matter thickness is less in the Tourette syndrome subjects than in the control subjects, and cooler colors (>0) indicate regions where individuals with Tourette syndrome have greater gray matter thickness than the control subjects. Note that cortical thickness in Tourette syndrome subjects is reduced bilaterally in ventral frontal and parieto-occipital regions by approximately 0.45 mm. These maps are constructed without any brain scaling and represent decreases in absolute thickness of the cortex in the Tourette syndrome group.

Figure 2

Symptom severity and cortical thickness. (a) Statistical P maps of the correlation between the worst-ever severity of tic symptoms and cortical thickness in a subsample of 24 individuals in the Tourette syndrome group for whom YGTSS data were available. The graph illustrates the negative correlation between symptom severity and cortical thickness (thinner cortex associated with higher severity scores) at one brain surface point in the superior portion of the sensory strip, indicated by the asterisk on the brain map. dorsal frontal, DF; dorsal medial frontal, DMF. (b) Simple facial tics and cortical thickness. Statistical P maps of the correlation between the number of different types of facial tic symptoms and cortical thickness in a sub-sample of 21 individuals in the Tourette syndrome group for whom detailed YGTSS data were available. The graph illustrates the negative correlation between facial tics and cortical thickness (thinner cortex associated with more types of facial tics) at one brain surface point in the inferior portion of the sensory strip, indicated by the asterisk on the brain map.