Information processing deficits in children with early and continuously treated phenylketonuria?

Executive function in treated phenylketonuria as measured by the one-back and two-back versions of the continuous performance test

The executive dysfunction hypothesis in treated phenylketonuria was investigated by means of the one-back and two-back versions of the continuous performance test. Eleven non-retarded, primary school-age children with classical phenylketonuria who had been treated early and continuously were indistinguishable from healthy, matched controls on the measures and test performance was not predicted by historical or concurrent plasma phenylalanine concentrations. Mean lifetime phenylalanine concentrations for the phenylketonuric subjects were within ranges currently recommended as dietary optima in the United Kingdom. The negative neuropsychological test findings add weight to the rationale for this policy.

Executive function and psychosocial adjustment in children with early treated phenylketonuria: correlation with historical and concurrent phenylalanine levels

The issue of what level of phenylalanine (phe) constitutes a safe upper limit for the therapeutic range in dietary treatment of phenylketonuria (PKU) remains unsettled. It has been proposed that the previous guideline figure of 600 mumol l-1 may result in specific impairment of executive functions such as attention, planning and set maintenance. The executive dysfunction theory was investigated by correlation historical and concurrent phe with executive, non-executive and personality tests in a group of early and continuously treated children, aged 10-13 years, with classical PKU, whose average phe levels of 355 mumol l-1 (SD = +/-144) for the pre-school period and 480 mumol l-1 (SD +/-193) for the primary school period corresponded to the upper limits presently recommended in the UK of 360 and 480 mumol l-1 for these age ranges. No clear associations were found between historical or concurrent phe levels and any of the neuropsychological or personality measures, thereby weakening the case for the emergence of executive deficits, at least when average phe levels remain close to the upper limits now considered safe. Furthermore no significant differences were found on psychological variables where comparison with population norms was possible.

Social behaviour and task orientation in early-treated PKU

In the context of the Dutch Collaborative Study on the Psychological Development of Children, early treated for Phenylketonuria (PKU), data were obtained on children's behaviour as perceived by parents (n = 53) and teachers (n = 57), using standardized behavioural questionnaires. Results are compared with a group representative of Dutch school-aged children (n = 1381) with a matched control group (n = 38), and with a group, to be considered as "Attention Deficit Hyperactivity Disorder" (ADHD, n = 38). Especially the clusters "negative task orientation" and "extraversion" distinguish between PKU children and controls. In parents' descriptions as well as in teachers' descriptions PKU children score higher in both clusters. Intriguing differences are found between PKU and ADHD. In parents' but not in teachers' descriptions PKU children show signs of negative task orientation almost to a similar degree as children with ADHD, but not of the signs of "negative social behaviour", characteristic for ADHD children. Data are discussed in terms of the effectiveness of early treatment and guidance.