LOCALIZED BRAIN PROTON NMR-SPECTROSCOPY IN YOUNG-ADULT PHENYLKETONURIA PATIENTS

Localized proton magnetic resonance spectroscopy with short echo time (TE= 20 ms) was used to investigate biochemical changes in the cerebra l white matter of 20 young adult patients (median 19 years) with pheny lketonuria (PKU). Results were compared with those of a group of 12 ag e-matched healthy volunteers (median 25 years). Concentrations of N-ac etyl-aspartate (NAA) and choline (Cho) relative to creatine (Cr) were unchanged. However, concentrations of inositol (Ins) relative to creat ine were found to be significantly lower (P < 0.001) in the PKU patien ts (0.30 +/- 0.09 versus 0.57 +/- 0.17). Individual inositol concentra tions did not correlate with age, diet, serum phenylalanine (Phe) leve ls or extent of pathological regions in the T-2-weighted images. The l ack of correlation with individual data suggests that the decreased in ositol concentration could be related to a metabolic deficiency during fetal development. No signal from the phenyl ring protons of phenylal anine was detected in the PKU patients (phenylalanine serum concentrat ion less than or equal to 1.27 mM), which suggests that concentration of phenylalanine may be lower in brain than in serum.