Increased putamen and callosal motor subregion in treatment-naïve boys with Tourette syndrome indicates changes in the bihemispheric motor network.

BACKGROUND: Despite an increasing number of studies, findings of structural brain alterations in patients with Tourette syndrome are still inconsistent. Several confounders (comorbid conditions, medication, gender, age, IQ) might explain these discrepancies. In the present study, these confounders were excluded to identify differences in basal ganglia and corpus callosum size that can be ascribed more probably to Tourette syndrome per se. METHODS: High-resolution T1-weighted structural magnetic resonance images of 49 boys with Tourette syndrome were compared with those of 42 healthy boys. The groups were matched for IQ and age (9 to 15 years). Boys with comorbid conditions and previous treatment were excluded. Volumes of gray and white matter, cerebrospinal fluid as well as the size of the basal ganglia, the thalamus, the corpus callosum and its subregions were estimated. RESULTS: The left and right putamen and subregion 3 of the corpus callosum were larger in boys with Tourette syndrome than in healthy controls. No differences were found in volumes of caudate nucleus, globus pallidus or thalamus of each hemisphere or in total callosal size and its other subregions. CONCLUSIONS: Bilateral enlargement of the putamen may reflect dopaminergic dysfunction or neuroimmunologic alterations (PANDAS) underlying Tourette syndrome. The larger callosal motor subregion 3 might be a consequence of daily tic activity. Previous divergent volumetric findings might be ascribed to confounding variables like comorbid conditions or medication, or to different imaging methods.

No brain structure abnormalities in boys with Tourette's syndrome: a voxel-based morphometry study.

Morphometric findings in Tourette's syndrome (TS) are still inconsistent probably due to differences in analysis approaches as well as several confounders (coexisting psychiatric conditions, medication status, etc.). Our aim was to identify possible morphometric changes in a well-defined sample of drug-naïve boys with "pure" TS. High-resolution structural magnetic resonance images of 38 boys with TS were compared with those of 38 healthy boys matched for age and IQ using voxel-based morphometry (VBM). Coexisting psychiatric conditions and previous medication were excluded. The inclusion of 10- to 15-year-old boys minimized the well known compensatory changes due to tic suppression over many years. VBM analyses revealed no differences between the treatment naïve boys with "pure" TS and healthy controls. Brain morphology is not altered in boys with "pure" TS. Further studies should reveal whether previous findings might be ascribed to confounding factors like coexisting psychiatric conditions or long-term compensatory mechanisms due to voluntary tic suppression.