Neuropsychological approaches to treatment policy issues in phenylketonuria

Neuropsychological research conducted so far on treatment factors in phenyl ketonuria suggests that dietary cessation at age 6 is too early. However, c ontinuation of diet until age 10 appears to provide protection against subs equent hyperphenylalaninaemia in the domains of perception. memory and moto r skill if concentrations remain at least below 1200 mu mol/l thereafter. L evels in the range 360 mu mol/l to 600 mu mol/l appear to constitute a haza rd for executive skill during the pre-school period but in the primary scho ol years the risk diminishes. Levels above 900 mu mol/l in early adolescenc e and adulthood may affect executive abilities adversely and the question r emains whether such effects are reversible. Conclusion Though scant, neuropsychological evidence does not seriously con tradict current British and German recommendations for dietary control in p henylketonuria.