Neuropsychological Deficits in Early Treated Phenylketonuric Children.

: In this preliminary study, six early treated children with phenylketonuria (PKU) were compared on the Halstead Neuropsychological Battery for Older Children with three groups of children with documented neurological disorders involving predominantly the left, the right, or bilateral dysfunction. The children with PKU had an overall level of neuropsychological impairment similar to that of the brain-damaged groups. The PKU group did not show a consistent pattern of lateralization, but there was some specificity to their deficits. The analyses showed that they were most similar to the right-hemisphere group. The children with PKU tended to show deficits consistently in two neuropsychological domains, conceptual and visuospatial skills, which would help explain their reported difficulty with mathematics. Further work is needed to test these results in a larger sample and to examine possible relationships with dietary compliance.