title: Corpus callosum abnormalities in Tourette syndrome: an MRI-DTI study of monozygotic twins.
abstract: BACKGROUND
  Tourette syndrome (TS) is a chronic neurodevelopmental disorder characterised by the presence of multiple motor and phonic tics. Recent brain imaging investigations with diffusion tensor imaging (DTI) techniques found reduced measures of connectivity in the corpus callosum of children with TS compared with healthy controls, thus raising the hypothesis that the reduced interhemispherical connectivity in TS reflects neural plasticity processes.
  
  
  METHODS
  We assessed corpus callosum white-matter connectivity with fractional anisotropy (FA) index from magnetic resonance-DTI in two monozygotic twins (male sex; age 20) discordant for the diagnosis of TS.
  
  
  RESULTS
  Both conventional morphological magnetic resonance images and fibre-tracking reconstruction failed to show any difference between the two twins. On the other hand, mean corpus callosum FA values were significantly lower in the affected twin than in the unaffected twin (p<0.01). The differences in FA values were highest in the posterior portions of the corpus callosum, and lowest in the central area.
  
  
  CONCLUSIONS
  Our findings of reduced interhemispherical white-matter connectivity in the affected twin support the hypothesis that plastic remodelling in the corpus callosum possibly represents an adaptation mechanism in TS.
authors.affiliation: Department of Neurology, Amedeo Avogadro University, Novara, Italy. a.cavanna@ion.ucl.ac.uk
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Cavanna
authors.forename: Alessandro
authors.initials: A
authors.lastname: Stecco
authors.forename: Hugh
authors.initials: H
authors.lastname: Rickards
authors.forename: Serena
authors.initials: S
authors.lastname: Servo
authors.forename: Emanuela
authors.initials: E
authors.lastname: Terazzi
authors.forename: Bradley
authors.initials: B
authors.lastname: Peterson
authors.forename: Mary M
authors.initials: MM
authors.lastname: Robertson
authors.forename: Alessandro
authors.initials: A
authors.lastname: Carriero
authors.forename: Francesco
authors.initials: F
authors.lastname: Monaco
mesh_terms: D016880:Anisotropy; D003337:Corpus Callosum / Q000473:pathology*; D038524:Diffusion Magnetic Resonance Imaging; D017352:Echo-Planar Imaging; D006801:Humans; D008297:Male; D009473:Neuronal Plasticity / Q000502:physiology; D005879:Tourette Syndrome / Q000473:pathology*; D014430:Twins, Monozygotic; D055815:Young Adult