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Objectives: To identify characteristics differentiating children with Down syndrome with and without autism.
Methods: Children with trisomy 21 (n = 20) and autism were compared to children with trisomy 21 without autism matched on chronologic age, race and gender. Communication, cognitive and adaptive behavior skills were assessed with standardized instruments. Medical history was reviewed and medical records were examined for head growth in the first 3 yrs of life. Paired t-tests were conducted to evaluate case-control differences on all standardized test scores. Proportions in each group having specific medical conditions were compared with a chi square statistic. Differences in head circumference growth velocity were evaluated with a repeated measures model using generalized estimating equations.
Results: Cases ranged in age from 4.3yr to 16.8yr (median = 9.1yr). Controls matched within 12 mo. Mean case-control difference in age equivalent scores for receptive language was -26.7mo (SEM = 15.6; p<0.0001); for expressive language it was -25.4mo (SEM = 16.8; p < 0.0001). Mean difference in full scale change sensitive score from the SB5 was -40 (SEM = 6.1; p<0.0001). Mean difference for the Adaptive Behavior Composite was -21.4 (SEM = 2.3; p<0.0001). Seven cases had a history of seizures compared to 1 control (p=0.04). All participants had decreased head size consistent with Down syndrome, with no case-control differences.
Conclusions: Children with Down syndrome and autism have more severe, widespread deficits than children with Down syndrome alone. Their presentation does not include increased head size but does include an increased risk for seizures that may indicate a more widespread loss of functional connectivity in the brain.