MAGNETIC-RESONANCE-IMAGING IN PHENYLKETONURIA - REVERSAL OF CEREBRAL WHITE-MATTER CHANGE

Objectives: To investigate the extent to which the abnormalities in ce rebral white matter in adolescents and adults with phenylketonuria (PK U) are reversible. Method: Magnetic resonance imaging (MRI), of the br ain was repeated in 41 patients with PKU (age range, 14 to 49 years) a fter an interval (median, 9 months; range, 3 to 12 months) of dietary intervention, Scans were scored according to the extent of the white m atter involvement, After an initial MRI, five patients returned to a s trict low-phenylalanine diet with amino acid supplement; 21 patients s tarted a low-protein diet (1 gm/kg) with amino acid supplement; and 15 patients made no dietary alteration. Results: Scans improved in all f ive patients who returned to a strict low-phenylalanine diet, in 5 of the 21 patients on the low-protein diet plus amino acid supplement, an d in 4 of the 15 patients who made no dietary change, There was a sign ificant association between change in the MRI findings and in the bloo d phenylalanine concentration (Pearson correlation: r = 0.55; p <0.000 2) 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 p rimarily in those in whom phenylalanine levels were reduced to less th an 900 mu mol/L. There was no obvious change in MRI score after 3 week s of strict phenylalanine restriction for the two adults who underwent serial scanning. Conclusion: The MRI changes in PKU are at least part ially reversible by lowering the blood phenylalanine concentration.