Review of neuropsychological functioning in treated phenylketonuria: an information processing approach.

Phenylketonuria is no longer associated with mental retardation and other devastating neurological effects. Nonetheless, learning disabilities and IQ loss are common, even in early-treated individuals. Until recently, IQ was used as the sole measure of mental functioning in this population. As specific academic deficits were recognized and as a greater variety of tests became available, evaluation of children with phenylketonuria has included neuropsychological testing. A review of the 21 published reports highlights the areas of consensus and the need for additional well designed studies in the future. Problem solving, particularly abstract reasoning and executive functions, appears to be impaired in children with phenylketonuria. Reaction time, or speed of mental processing, appears to be the other important area affected in PKU. An information processing model is presented as a paradigm for further research and development of remedial strategies for children with phenylketonuria.