Brain magnetic resonance imaging in children with optimally controlled hyperphenylalaninaemia.

This study was undertaken to investigate whether the white-matter changes on MRI and the EEG abnormalities detectable in treated adolescents and adults with hyperphenylalaninaemia (HPA) can be detected in younger children on an optimally controlled diet. The study included 17 children, 7-12 years of age, with HPA. The MRI of five healthy children were included in the blind evaluation of the MR images. According to mutation genotype and dietary tolerance of phenylalanine, 9 patients have severe HPA and 8 have moderate HPA, all requiring dietary treatment. Mild white-matter hyperintensity was detected in 1 of the 5 healthy children and in 10 of 17 patients. EEG was abnormal in 2 patients. This group of children was compared with a previously reported group of adolescents with HPA who had been treated according to the same dietary regimen. MRI changes and EEG abnormalities were significantly less frequent in the group of children than in the group of adolescents. It is suggested that the more frequent MRI changes and EEG abnormalities seen in adolescents are related to the fact that a relaxation of the dietary treatment after the age of 8 years is often accepted.