Lateralization of brain networks and clinical severity in toddlers with autism spectrum disorder: A HARDI diffusion MRI study

Recent diffusion tensor imaging studies in adolescents and children with Autism Spectrum Disorder (ASD) have reported a loss or an inversion of the typical left-right lateralization in fronto-temporal regions crucial for sociocommunicative skills. No studies explored atypical lateralization in toddlers and its correlation with clinical severity of ASD. We recruited a cohort of 20 subjects aged 36 months or younger receiving a first clinical diagnosis of ASD (15 males; age range 20-36 months). Patients underwent diffusion MRI (High-Angular-Resolution Diffusion Imaging protocol). Data from cortical parcellation were combined with tractography to obtain a connection matrix and diffusion indexes (D-I) including mean fractional anisotropy (D-FA), number of tracts (D-NUM), and total tract length (D-TTL). A laterality index was generated for each measure, and then correlated with the Autism Diagnostic Observation Schedule-Generic (ADOS-G) total score. Laterality indexes of D-FA were significantly correlated with ADOS-G total scores only in two intrafrontal connected areas (correlation was positive in one case and negative in the other). Laterality indexes of D-TTL and D-NUM showed significant negative correlations (