title: Altered interhemispheric connectivity in individuals with Tourette's disorder.
abstract: OBJECTIVE
  The corpus callosum is the major commissure connecting the cerebral hemispheres. Prior evidence suggests involvement of the corpus callosum in the pathophysiology of Tourette's disorder. The authors assessed corpus callosum size and anatomical connectivity across the cerebral hemispheres in persons with Tourette's disorder.
  
  
  METHODS
  The size of the corpus callosum was determined on the true midsagittal slices of reformatted, high-resolution magnetic resonance imaging scans and compared across groups in a cross-sectional case-control study of 158 subjects with Tourette's disorder and 121 healthy comparison subjects, ages 5-65 years.
  
  
  RESULTS
  In the context of increasing midsagittal corpus callosum area from childhood to age 30 years, children with Tourette's disorder had smaller overall corpus callosum size, whereas adults with Tourette's disorder on average had larger corpus callosum size, yielding a prominent interaction of diagnosis with age. Corpus callosum size correlated positively with tic severity. Corpus callosum size also correlated inversely with dorsolateral prefrontal and orbitofrontal cortical volumes in both the subjects with Tourette's disorder and the comparison subjects, but the magnitudes of the correlations were significantly greater in the group with Tourette's disorder. The effects of medication and comorbid illnesses had no appreciable influence on the findings.
  
  
  CONCLUSIONS
  Given prior evidence for the role of prefrontal hypertrophy in the regulation of tic symptoms, the current findings suggest that neural plasticity may contribute to smaller corpus callosum size in persons with Tourette's disorder, which thereby limits neuronal trafficking across the cerebral hemispheres and reduces input to cortical inhibitory interneurons within the prefrontal cortices. Reduced inhibitory input may in turn enhance prefrontal excitation, thus helping to control tics and possibly contributing to the cortical hyperexcitatibility reported previously in patients with Tourette's disorder.
authors.affiliation: New York State Psychiatric Institute, 1051 Riverside Dr., Unit 74, New York, NY 10032, USA.
authors.forename: Kerstin J
authors.initials: KJ
authors.lastname: Plessen
authors.forename: Tore
authors.initials: T
authors.lastname: Wentzel-Larsen
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hugdahl
authors.forename: Patricia
authors.initials: P
authors.lastname: Feineigle
authors.forename: Joel
authors.initials: J
authors.lastname: Klein
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Staib
authors.forename: James F
authors.initials: JF
authors.lastname: Leckman
authors.forename: Ravi
authors.initials: R
authors.lastname: Bansal
authors.forename: Bradley S
authors.initials: BS
authors.lastname: Peterson
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000033:anatomy & histology; D015897:Comorbidity; D003337:Corpus Callosum / Q000033:anatomy & histology* / Q000503:physiopathology; D003430:Cross-Sectional Studies; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D009771:Obsessive-Compulsive Disorder / Q000453:epidemiology; D017397:Prefrontal Cortex / Q000503:physiopathology; D012720:Severity of Illness Index; D005879:Tourette Syndrome / Q000175:diagnosis* / Q000453:epidemiology / Q000503:physiopathology