Study: MRI sheds light on autism risk before symptoms are seen
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Abnormal development of white matter pathways in the first six months to one year of life could precede the manifestation of autistic symptoms in high-risk infants, according to research published in the June issue of the American Journal of Psychiatry.

Earlier detection of autism, which is typically diagnosed around ages 2 or 3, could lead to interventions which improve symptoms, explained authors Jason J. Wolff, PhD, of the University of North Carolina, Chapel Hill, and colleagues. “It's a promising finding. At this point, it's a preliminary albeit great first step towards thinking about developing a biomarker for risk in advance of our current ability to diagnose autism," Wolff said in a release.

Wolff and colleagues followed 92 infants from the time they were six months old to age two. All were considered at high-risk for autism because they had older siblings with the condition. Every child underwent diffusion tensor MR imaging at six months and a behavioral assessment at 24 months. The majority also had additional scans at 12 months, 24 months or both.

Thirty percent of the infants were diagnosed with autism at 24 months. White matter tract development for 12 of the 15 tracts examined differed significantly between those who developed autism and those who did not. An analysis of fractional anisotropy (FA) showed that infants who developed autism had elevated FA values early in the study which decreased over time. By 24 months, autistic infants had lower FA values than infants without autism.

The authors stressed that the wider view of longitudinal data was key to detecting the patterns in development before the onset of symptoms. “The relevance of developmental trajectories to understanding these dynamic processes is undeniable,” they wrote, adding that an even wider view—extending neuroimaging to infants younger than six months and older than two years—could help clarify the origins of diverging trajectories.

They also celebrated the possibility that autism biomarkers could be developed, and suggested that future research might advance this cause.

"For the first time, we have an encouraging finding that enables the possibility of developing autism risk biomarkers prior to the appearance of symptoms, and in advance of our current ability to diagnose autism," co-investigator Alan C. Evans, PhD, of McGill University in Montreal, said in a release.

These findings were part of the on-going Infant Brain Imaging Study (IBIS), which is funded by the National Institutes of Health (NIH).