Deficits in selective and sustained attention processes in early treated children with phenylketonuria--result of impaired frontal lobe functions?

Abstract

Twenty normally intelligent children with early treated phenylketonuria (PKU) (IQ: mean = 101.4, SD = 10.0; age: mean = 10 years 11 months, SD = 1.3 years) and 20 healthy controls, matched for age, sex and IQ, were assessed for their selective (Stroop Task) and sustained attention (Test-d-2). Using positron emission tomography an activation of the frontal lobe during the Stroop task had previously been demonstrated. In addition to the Stroop Task and the Test-d-2, a short-term memory test as a "non-frontal-lobe-function-task" was administered to all subjects. Group comparisons demonstrated that PKU children had specific deficits in selective and sustained attention, which were significantly correlated with the concurrent serum phenylalanine concentration. The results give evidence that even dietary treated children with PKU were suffering from impaired attentional control mechanisms in spite of a normal IQ. The deficits might be the result of impaired frontal lobe functions.