Corpus callosum morphology from magnetic resonance images in Tourette's syndrome

We measured the midline cross-sectional area and other morphologic features of the corpus callosum (CC) from magnetic resonance (MR) images in 14 unmedicated patients with Tourette's syndrome (TS) and 14 normal control subjects matched for age, sex, handedness, and socioeconomic status. Each CC was manually circumscribed on midline images from a T₁-weighted sagittal series, and the area of the entire CC and five anatomic subdivisions were measured. CC circumference, regional width and mean callosal curvature were also measured. CC cross-sectional area correlated positively with brain size and basal ganglia volumes. The magnitude of reduction (17.7%) in total CC area in TS patients compared with control subjects was similar to the reductions seen in all CC subdivision areas. Analyses of covariance with total midsagittal cross-sectional head area as a covariate revealed the reductions to be statistically significant for the overall CC area and all subregion areas. CC width tended to be nonsignificantly thinner in all subdivisions (from 5% to 11%) and the overall length of the center line measured from rostrum to splenium was significantly reduced in the TS group (by 5.3%). Measures of mean callosal curvature suggested that CCs in TS patients are less rounded than those of normal control subjects. Worst-ever motor tic symptoms showed the strongest significant correlation with the length of the CC center line in TS patients (r = 0.88). These findings suggest that structural interhemispheric connectivity may be aberrant in the central nervous systems of TS patients and they provide indirect supportive evidence for the presence of altered cerebral lateralization in the disorder.