We applied diffusion-tensor MRI (DT-MRI) to investigate directly the water diffusivity within subcortical gray matter structures comprising the fronto-striato-thalamic (FST) circuit, which is implicated in the pathophysiology of Tourette syndrome (TS). We investigated the structural integrity of basal ganglia and thalamus in 23 children with TS and 35 age-matched healthy controls (NC), and examined the association of DT-MRI measures to tic severity and comorbid symptoms. We measured parallel (lambda(1)) and perpendicular (lambda(23)) diffusivity, mean diffusivity (MD), and fractional anisotropy (FA) in both hemispheres. Compared with NC, the TS group showed a significant increase in lambda(1) (P = 0.003) and MD (P = 0.027) in the bilateral putamen, an increase in lambda(23) in right thalamus (P = 0.008), and a reversed asymmetry of FA (P = 0.03) in the thalamus. There was a significant positive correlation between lambda(23) in right thalamus and tic severity. TS patients showed significantly lower left caudate volume (P = 0.011) and bilateral thalamic volumes (left, P = 0.035, right P = 0.006) compared with NC. These findings support the notion that microstructural dysfunction measured by DT-MRI in component regions of the FST circuit contribute to the pathophysiology in TS.
(c) 2008 Movement Disorder Society.