Improvements in upper extremity function in children with unilateral spastic cerebral palsy after intensive training correlates with interhemispheric connectivity

AIMS The corpus callosum (CC) regulates signalling between the two hemispheres and plays an important role in upper limb functions. There is limited evidence on the relationships between the integrity of the CC and upper limb functions in children with USCP. Furthermore, the extent of how much the CC can be used as a biomarker to predict hand functions following intensive interventions remains unknown. We examined 1) the relationship between hand function and tractography of the CC, and 2) the associations between the integrity of the CC and changes in hand function following intensive intervention. METHODS Forty-four participants received 90 hours of intensive therapy and were randomly allocated in one of two training groups: Hand-arm Bimanual Intensive Therapy (HABIT) or Constraint-Induced Movement Therapy (CIMT). Hand functions were assessed pre-and post-intervention by a blinded clinician using the Jebsen-Taylor of Hand Function (JTTHF), Assisting Hand Assessment (AHA), and Box and Blocks test (BBT). Functional goals and daily functioning were measured using the Canadian Occupational Performance Measure and the Abilhand-Kids. CC tractography was reconstructed using diffusion tensor imaging (DTI). Corpus callosum was segmented into three regions of interest (genu, midbody and splenium). Linear regression and pearson correlations were used to assess the relationships between bimanual outcomes and DTI parameters. RESULTS Both groups demonstrated improvement of hand function (p<0.05). JTTHF, AHA and BBT significant correlated with DTI variables for all ROIs (p<0.05). Bimanual and perceived manual ability of children changes following CIMT were negatively correlated with number of streamlines and number of voxel for the whole CC (r=-.442, p=0.05), midbody (r=-.458, p=0.042) and spelnium (r=-.512, p=0.021). No significant correlation was observed for the HABIT group. INTERPRETATION Tractography of the CC was found to be associated with unimanual and bimanual functions at baseline. Children with reduced integrity of the CC and with greater bimanual impairments improve more from CIMT. On the contrary, all children in the HABIT group had similar improvements independent of the CC integrity.