Neuropsychological approaches to treatment policy issues in phenylketonuria.

UNLABELLED: Neuropsychological research conducted so far on treatment factors in phenylketonuria suggests that dietary cessation at age 6 is too early. However, continuation of diet until age 10 appears to provide protection against subsequent hyperphenylalaninaemia in the domains of perception, memory and motor skill if concentrations remain at least below 1200 mumol/l thereafter. Levels in the range 360 mumol/l to 600 mumol/l appear to constitute a hazard for executive skill during the pre-school period but in the primary school years the risk diminishes. Levels above 900 mumol/l in early adolescence and adulthood may affect executive abilities adversely and the question remains whether such effects are reversible.
CONCLUSION: Though scant, neuropsychological evidence does not seriously contradict current British and German recommendations for dietary control in phenylketonuria.