In order to identify early risk markers for autism spectrum disorder (ASD), investigators at University of California Davis School of Medicine and Davis Children’s Hospital conducted a longitudinal brain MRI study of infant siblings in conjunction with behavioral assessments leading to an outcome classification at 24 months or later (mean age 32.5 months). Fifty-five infants (33 ‘high-risk’ infants having an older sibling with ASD and 22 ‘low-risk’ infants having no relatives with ASD) were imaged at three time points: 6-9 months, 12-15 months, and 18-24 months of age. Compared to infants classified as developmental delay or typical development, 10 infants who developed ASD had significantly greater extra-axial fluid at 6-9 months, which remained elevated at 12-15 and 18-24 months. The amount of extra-axial fluid detected at 6 months was predictive of more severe ASD symptoms at time of outcome. Infants who developed ASD also had significantly larger total cerebral volumes at both 12-15 and 18-24 months of age. These novel findings raise the potential for use of structural MRI to aid in early detection (6-9 months of age) of children at risk for ASD. [1]

COMMENT. The clinical diagnosis of ASD is usually delayed until at least 18 months of age. This study provides a potential brain MRI biomarker for the earlier diagnosis and treatment of ASD in at risk infants.

Extra-axial fluid accumulation (communicating hydrocephalus) with rapid head growth in the first year of life typically resolves without intervention, but it may be associated with seizures and motor delays [2] and now is associated with development of ASD. Extra-axial fluid and rapid head growth in infancy is not always a benign reversible disorder.