FACTORS AFFECTING COGNITIVE, MOTOR, BEHAVIORAL AND EXECUTIVE FUNCTIONING IN CHILDREN WITH PHENYLKETONURIA

We administered measures of cognitive, frontal lobe (executive), behav ioral and motor functioning to 18 children with classical phenylketonu ria, aged 12-101 months, in order to determine the relationship of age , current and lifetime average phenylalanine levels, and individual va riation (standard deviation of lifetime average levels) to these funct ions. On measures of cognitive function, in children greater than or e qual to 3 y of age lower current phenylalanine levels were associated with higher cognitive functioning. On a behavioral temperament scale d esigned for normal children, we found that higher current and average phenylalanine levels correlated with more difficult temperament. Motor function was also poorer in children with phenylketonuria, and was mo st impaired in children with current phenylalanine levels >360 mu mol/ l. We also identified a previously unreported correlation between incr eased individual variation and poorer executive function performance, a finding that may raise new management concerns about level fluctuati ons. Maintenance of phenylalanine levels < 360 mu ml/l may be necessar y for optimal performance in children with phenylketonuria.