The development of auditory and visual evoked potentials in early treated phenylketonuric children.

Brain-stem auditory evoked potentials (BAEPs) and flash visual evoked potentials (F-VEPs) were gathered from 8 early treated phenylketonuric (PKU) children in a prospective longitudinal investigation during the 1st to the 12th months after birth. No consistent differences were found in the wave morphology of evoked potentials in PKU children from that of age-matched controls. Studying the latency of some components showed that in BAEPs, wave I latency was similar to control values for the whole year, but that the I-V interpeak mean latency (I-V IPL) was always significantly longer than in controls. In F-VEPs wave N1 latency was significantly longer than in controls only at 1-2 months of age, but returned to control values at 3-4 months (when all children were on dietary therapy) and remained in this range up to the 12th month. The mean latency of the P2 wave of flash VEPs was always significantly longer in PKU children than in controls. These results show that relevant alterations in evoked potentials may be found in PKU children several months after starting dietary therapy. This suggests that information processing in the brain may be impaired for a long time, due to abnormal metabolic conditions between birth and the onset of dietary therapy.