Enlargement of thalamic nuclei in Tourette syndrome.

CONTEXT: The basal ganglia and thalamus together connect in parallel closed-loop circuits with the cortex. Previous imaging studies have shown modifications of the basal ganglia and cortical targets in individuals with Tourette syndrome (TS), but less is known regarding the role of the thalamus in TS pathogenesis. OBJECTIVE: To study the morphological features of the thalamus in children and adults with TS. DESIGN: A cross-sectional, case-control study using anatomical magnetic resonance imaging. SETTING: University research center. PARTICIPANTS: The 283 participants included 149 with TS and 134 normal control individuals aged 6 to 63 years. MAIN OUTCOME MEASURES: Conventional volumes and measures of surface morphology of the thalamus. RESULTS: Analyses of conventional volumes and surface morphology were consistent in demonstrating an enlargement in TS-affected thalami. Overall volumes were 5% larger in the group composed of children and adults with TS. Statistical maps of surface contour demonstrated enlargement over the lateral thalamus. Post hoc testing indicated that differences in IQ, comorbid illnesses, and medication use did not account for these findings. CONCLUSIONS: Morphological abnormalities in the thalamus, together with the disturbances reported in the sensorimotor cortex, striatum, and globus pallidus, support the hypothesis of a circuitwide disorder within motor pathways in TS. The connectivity and function of the numerous and diverse thalamic nuclei within cortical-subcortical circuits constitute an anatomical crossroad wherein enlargement of motor nuclei may represent activity-dependent hypertrophy within this component of cortical-subcortical motor circuits, or an adaptive response within a larger putative compensatory system that could thereby directly modulate activity in motor circuits to attenuate the severity of tics.

Basal ganglia surface morphology and the effects of stimulant medications in youth with attention deficit hyperactivity disorder.

OBJECTIVE: Disturbances in the basal ganglia portions of cortico-striato-thalamo-cortical circuits likely contribute to the symptoms of attention deficit hyperactivity disorder (ADHD). The authors examined the morphologic features of the basal ganglia nuclei (caudate, putamen, and globus pallidus) in children with ADHD. METHOD: A total of 104 individuals (combined-type ADHD patients: N=47; healthy comparison subjects: N=57), aged 7 to 18 years, were examined in a cross-sectional case-control study using anatomical magnetic resonance imaging. Conventional volumes and the surface morphology for the basal ganglia were measured. RESULTS: Overall volumes were significantly smaller only in the putamen. Analysis of the morphological surfaces revealed significant inward deformations in each of the three nuclei, localized primarily in portions of these nuclei that are components of limbic, associative, and sensorimotor pathways in the cortico-striato-thalamo-cortical circuits in which these nuclei reside. The more prominent these inward deformations were in the patient group, the more severe the ADHD symptoms. Surface analyses also demonstrated significant outward deformations of all basal ganglia nuclei in the ADHD children treated with stimulants compared with those ADHD youth who were untreated. These stimulant-associated enlargements were in locations similar to the reduced volumes detected in the ADHD group relative to the comparison group. The outward deformations associated with stimulant medications attenuated the statistical effects of the primary group comparisons. CONCLUSIONS: These findings potentially represent evidence of anatomical dysregulation in the circuitry of the basal ganglia in children with ADHD and suggest that stimulants may normalize morphological features of the basal ganglia in children with the disorder.