Information processing in patients with early and continuously-treated phenylketonuria

A total of 33 patients with early and continuously-treated phenylketonuria (PKU) between 7 and 16 years of age and 33 matched controls participated in a study examining perceptual, central, and response-related mechanisms of information processing. The specific mechanisms studied were: perceptual filtering, memory search, response selection, response execution, and motor presetting. In addition, groups were compared on mean intelligence level and task oriented behaviour. The performance of the PKU patients practically matched that of the controls on all three tasks, suggesting that PKU patients who are continuously maintained on a well-controlled phenylalanine-restricted diet are not impaired in the elementary mechanisms of information processing. Furthermore, groups did not differ in mean IQ or task-oriented behaviour.

CONCLUSION

These results underline the importance of continued, well-controlled dietary treatment. Further studies are recommended to obtain a more complete evaluation of the potential of PKU patients under these stricter dietary treatment conditions.

The phenylalanine response curve in relation to growth and mental development in the first year of life

Thirty-three children with classical phenylketonuria were treated from 9 to 21 days of age onward. The standard for phenylalanine concentration was 0.2-0.5 mmol/l. During the first years of life phenylalanine concentrations were measured once every two to six weeks. For each child these values were graphically plotted in a so-called phenylalanine response curve. Growth and mental development indices were assessed at about one and two years of age. Measurements for weight, height and head circumference were normal at one month of age, showed a significant decline at the age of one year but were restored for normal values at the age of two. No associations were found with phenylalanine parameters. Mental development indices at one and two years were not different from normal. Significant negative correlations were found between mental development indices at one year and phenylalanine values above 0.5 mmol/l. Changes in mental development indices between the first and second years of life are significantly related to the phenylalanine levels during the second year of life.

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.

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

Thirty-three patients with early and continuously treated classical phenylketonuria (PKU) and 33 controls matched for age, gender, and educational level of both parents, participated in a chronometric study exploring elementary mechanisms of information processing. Subjects performed speeded performance tasks designed to systematically vary the load on perceptual, central, and output-related mechanisms of information processing. A preliminary analysis of the data indicated that the overall performance of patients with early and continuously treated PKU practically matched that of the controls on all three tasks. Although this finding must be interpreted with caution as it is based on only a preliminary analysis of the data, it suggests that PKU patients who are continuously maintained on a well-controlled phenylalanine-restricted diet are not deficient in the elementary mechanisms of processing. Given the more recent findings indicating that young children with early-treated classical PKU have specific cognitive deficits in the executive function skills, despite relatively strict dietary control, the authors suggest that future studies should focus on these higher-order cognitive processes.

Phenylketonuria and some aspects of emotional development

Early dietary treatment of phenylketonuria (PKU) prevents intellectual retardation and gross neurological impairment although not all neuropsychological problems. This study investigates to what extent the illness and its treatment imposes a burden on emotional development of early-treated PKU patients and on rearing practices of their parents. It is concluded that in early-treated PKU it is particularly difficult to find constructive ways to adapt to the situation for children as well as for parents. As coping with PKU and its treatment is so complicated, paediatric control should be combined with psychocounselling.

[Intellectual development of patients with phenylketonuria; 15-year national screening in The Netherlands]

OBJECTIVE

To evaluate the intellectual development of patients with phenylketonuria (PKU) or hyperphenylalaninaemia (HPA).

DESIGN

Longitudinal follow-up study.

SETTING

University Children's Hospitals of Amsterdam, Groningen, Nijmegen, and Rotterdam.

METHODS

In September 1974 a nationwide neonatal screening for PKU started in the Netherlands. We obtained data on the intellectual development of 116 patients (101 classical PKU, 15 HPA), all detected and treated in the first 15 years of this screening. The children were tested at 6 ages with different instruments for the assessment of intellectual functions, and the scores were compared with the test norms. Performance and verbal capacities were determined as well as possible sex-related differences.

RESULTS

Our data show that the levels of intellectual functioning of PKU and HPA patients do not differ from test norms until the age of 8 yr 6 months. In the older PKU patients there appears to be a trend towards lower IQ scores. We found no sex differences in the mental functioning of PKU patients.

CONCLUSION

Continuation of this study is necessary in order to investigate possible negative effects of PKU on cognitive functioning, especially in the older age groups.