OBJECTIVETo observe brain white matter changes in children with late-treated phenylketonuria (PKU) before and after receiving treatment.

METHODSThis study included 19 PKU patients (aged 34-410 weeks) who were administered a low-phenylalanine diet (< 15-50 mg/kg daily) for 8-16 months. The brain MR imaging with spin-echo T1-weighted and T2-weighted sequences in coronal and axial planes was taken before and after treatment. The white matter abnormalities (T2WI high signal intensity) were graded based on the Thompson grading system. Meanwhile the intelligence quotient (IQ) or developmental quotient (DQ) was tested by the Gesell's Intelligence Scale.

RESULTSAll 19 PKU patients presented with the brain white matter lesions, manifesting abnormally high T2-signal intensity in the periventricular region around anterior and posterior horns of both lateral ventricles. Different extents of mental retardation were also observed in the 19 patients. The low phenylalanine diet treatment decreased the average grade of abnormal T2-signal intensity from 2.59 to 1.76 (P < 0.05). The mean IQ or DQ improved from 44.8 to 61.6 after treatment (P < 0.05). There was some correlation between the amelioration of brain white matter lesions and IQ or DQ.

CONCLUSIONSThe patients with late-treated PKU have a higher occurrence of the brain white matter lesions and mental retardation. A low-phenylalanine diet treatment can partly improve the abnormalities. Brain white matter lesions may play a part in mental retardation.