Electroencephalographic findings in children with phenylketonuria.

The electroencephalographic findings of 90 patients with phenylketonuria (PKU) who were observed in one clinic were critically reviewed. Seventy-three percent of patients with classical PKU that was diagnosed and treated early (group 1) were found to have normal EEGs, 23% had mild background abnormalities, and 4% had paroxysmal discharges. Only 31% of the patients in whom PKU was diagnosed after 6 months of age (group 2) had normal EEGs, while 24% had background abnormalities and 45% had paroxysmal discharges. Of the patients with atypical PKU (group 3), 62% had normal EEGs and 38% showed background abnormalities. No major changes in EEG patterns were noted with initiation or termination of the low phenylalanine diet. There was no correlation between the degree of dietary control, EEG findings, and intellectual performance in group 1.