Lateralization of Brain Networks and Clinical Severity in Toddlers with Autism Spectrum Disorder: A HARDI Diffusion MRI Study.
In toddlers with ASD, more inverted fronto-temporal brain asymmetry links to higher ADOS severity.
01Research in Context
What this study did
Conti et al. (2016) scanned 20 toddlers with ASD using HARDI diffusion MRI.
They measured how water moves along white-matter cables in left and right brain sides.
Each child also took the ADOS-G so the team could rank autism severity.
What they found
Kids with more upside-down left-right wiring in fronto-temporal tracts scored higher on the ADOS.
In plain words, stranger brain asymmetry went hand-in-hand with more obvious social-communication issues.
How this fits with other research
Eussen et al. (2016) looked at older kids and saw wide white-matter problems across both sides, not just flipped asymmetry. Together the papers show early lateral quirks may grow into broader cable damage.
Storch et al. (2012) found 90 % of routine clinical MRIs looked normal in high-functioning children. The clash is simple: research-grade diffusion sequences catch micro-differences that standard scans miss.
Bai et al. (2023) added gray-matter and functional data in the same toddler age range. Their combo of structure plus connectivity reached 86 % accuracy in separating ASD from typical kids, hinting that a full brain package—white, gray, and function—may give the clearest picture.
Why it matters
If you assess toddlers with ASD, know that flipped fronto-temporal asymmetry can signal higher support needs. Do not expect regular MRI reports to flag this; you will need research-level diffusion data. Pairing these findings with gray-motor clues from other labs can sharpen early profiles and guide intensity of early intervention.
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02At a glance
03Original abstract
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 (DI ) including mean fractional anisotropy (DFA ), number of tracts (DNUM ), and total tract length (DTTL ). 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 DFA 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 DTTL and DNUM showed significant negative correlations (P < 0.05) in six connected areas, mainly fronto-temporal. This study provides first evidence of a significant correlation between brain lateralization of diffusion indexes and clinical severity in toddlers with a first diagnosis of ASD. Significant correlations mainly involved regions within the fronto-temporal circuits, known to be crucial for sociocommunicative skills. It is of interest that all correlations but one were negative, suggesting an inversion of the typical left-right asymmetry in subjects with most severe clinical impairment.
Autism research : official journal of the International Society for Autism Research, 2016 · doi:10.1002/aur.1533