Regression of neuropsychological deficits in early-treated phenylketonurics during adolescence

Even early-treated phenylketonuric patients suffer from phenylalanine-assoc iated (mild) neuropsychological impairment. To date it is still unclear whe ther patients' deficits show a progression on ageing. This unsolved questio n seems to be an important aspect in the still ongoing debate about how lon g and how strictly the patients should be maintained on diet. Twenty early- treated (20 +/- 10, 9-30 days) adolescent phenylketonurics (10 boys, 10 gir ls) and 20 healthy controls, matched for age, sex and IQ, were investigated twice at a mean ages of 11 and 14 years for their IQ (Culture Fair Intelli gence Test-Scale 2; CFT-20), fine motor abilities (Motor PerformanceTask), sustained (Test d(2)) and selective attention (Stroop-Task). At the first t est, examinations revealed significant blood phenylalanine-correlated neuro psychological deficits in PKU patients. In spite of raised blood phenylalan ine concentrations during the following 3 years and significantly elevated concurrent blood phenylalanine concentrations, the repeated measurements re vealed a significant decrease of patients' deficits compared to controls. C linical-neurological status of patients and controls was normal at both tes t times. The results indicate a decreased vulnerability of PKU-patients wit h respect to their neuropsychological functioning against elevated blood ph enylalanine levels on ageing.