CORPUS-CALLOSUM MORPHOLOGY FROM MAGNETIC-RESONANCE IMAGES IN TOURETTES-SYNDROME

We measured the midline cross-sectional area and other morphologic fea tures 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 T- 1-weighted sagittal series, and the area of the entire CC and five ana tomic subdivisions were measured. CC circumference, regional width, an d mean callosal curvature were also measured. CC cross-sectional area correlated positively with brain size and basal ganglia volumes. The m agnitude of reduction (17.7%) in total CC area in TS patients compared with control subjects was similar to the reductions seen in all CC su bdivision areas. Analyses of covariance with total midsagittal cross-s ectional head area as a covariate revealed the reductions to be statis tically significant for the overall CC area and all subregion areas. C C width tended to be nonsignificantly thinner in all subdivisions (fro m 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 patien ts are less rounded than those of normal control subjects. Worst-ever motor tic symptoms showed the strongest significant correlation with t he length of the CC center line in TS patients (r = 0.88). These findi ngs suggest that structural interhemispheric connectivity may be aberr ant in the central nervous systems of TS patients, and they provide in direct supportive evidence for the presence of altered cerebral latera lization in the disorder.