A DTI study on the corpus callosum of treatment-naïve boys with 'pure' Tourette syndrome

Disturbances in the corpus callosum (CC) indicating altered interhemispheric connectivity have been associated with Tourette syndrome (TS). The objective of the present study was to refine knowledge about interhemispheric connectivity in TS by analyzing four different diffusion tensor imaging (DTI) parameters in a very homogeneous group of treatment-naïve boys with pure TS in comparison to male healthy controls (HC). Fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD) and mean diffusivity (MD) of five CC-segments were assessed from DTI of 26 treatment-naïve boys with pure TS and 24 HC. We observed no group differences in both FA and RD. However, we found a significant effect for AD and a trend for MD, being both reduced in boys with TS in comparison to HC. Moreover, a negative correlation between AD and the Yale Global Tic Severity Scale total score was observed. Reduced AD of the CC in treatment-naïve boys with pure TS in comparison to HC may indicate that significant alterations in white matter microstructure of the CC contribute to tic symptomatology per se and seem not to be related to confounders such as consequences of long-term medication, tic performance or tic suppression.