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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.

The aim of the study was to determine whether abnormal connectivity of the fronto-striato-thalamic circuit underlies the morphological changes in subcortical structures of patients with Tourette syndrome and to correlate these changes with neurobehavioral measures. A total of 18 children with Tourette syndrome and 12 age-matched healthy controls underwent diffusion tensor magnetic resonance imaging. Tractography of the fronto-striato-thalamic circuit was achieved using probability distribution function of individual voxels. The Tourette syndrome group had significantly lower probability of connection between caudate nucleus and anterior-dorsolateral-frontal cortex on the left (P = .038). Obsessive-compulsive behavior was negatively associated with connectivity score of the left caudate and anterior dorsolateral frontal cortex (P = .01) and was positively associated with connectivity score for the subcallosal gyrus (P = .009) and for the lentiform nucleus (P = .008). The abnormal connectivity among components of the fronto-striato-thalamic circuit bilaterally (ie, seeds on the caudate and thalamus) in patients with Tourette syndrome provides direct evidence for the involvement of these circuits in the pathophysiology.

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