Magnetic resonance imaging in phenylketonuria: reversal of cerebral white matter change

J Pediatr. 1995 Aug;127(2):251-5. doi: 10.1016/s0022-3476(95)70303-9.


Objectives: To investigate the extent to which the abnormalities in cerebral white matter in adolescents and adults with phenylketonuria (PKU) are reversible.

Method: Magnetic resonance imaging (MRI) of the brain was repeated in 41 patients with PKU (age range, 14 to 49 years) after an interval (median, 9 months; range, 3 to 12 months) of dietary intervention. Scans were scored according to the extent of the white matter involvement. After an initial MRI, five patients returned to a strict low-phenylalanine diet with amino acid supplement; 21 patients started a low-protein diet (1 gm/kg) with amino acids supplement; and 15 patients made no dietary alteration.

Results: Scans improved in all five patients who returned to a strict low-phenylalanine diet, in 5 of the 21 patients on the low-protein diet plus amino acid supplement, and in 4 of the 15 patients who made no dietary change. There was a significant association between change in the MRI findings and in the blood phenylalanine concentration (Pearson correlation: r = 0.55; p < 0.0002) and between change in the MRI and in the phenylalanine level at the time of the second scan (r = 0.58; p < 0.0001). Improvement was seen primarily in those in whom phenylalanine levels were reduced to less than 900 mumol/L. There was no obvious change in MRI score after 3 weeks of strict phenylalanine restriction for the two adults who underwent serial scanning.

Conclusion: The MRI changes in PKU are at least partially reversible by lowering the blood phenylalanine concentration.

MeSH terms

  • Adolescent
  • Adult
  • Amino Acids / administration & dosage
  • Brain / pathology*
  • Diet, Protein-Restricted
  • Female
  • Follow-Up Studies
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Middle Aged
  • Phenylalanine / administration & dosage
  • Phenylalanine / blood
  • Phenylketonurias / diet therapy*
  • Phenylketonurias / pathology*
  • Time Factors


  • Amino Acids
  • Phenylalanine