WHITE-MATTER ABNORMALITIES IN PHENYLKETONURIA - RESULTS OF MAGNETIC-RESONANCE MEASUREMENTS

In adolescents and adults with PKU, blood phenylalanine levels above 1 0 mg/dl are generally associated with white matter changes in MRI. The grade of these changes is correlated to most recent blood phenylalani ne levels. Based on studies using T-2 relaxometry the MRI changes seem to be the consequence of a reversible dysmyelination. The clinical re levance of these white matter changes remains unclear as the extent of MRI alterations did not correlate with IQ, neurological and electroph ysiological deficits of the patients. The intracerebral phenylalanine concentration as measured by protonspectroscopy amounts to about 50% o f blood phenylalanine concentrations. Preliminary data indicate that b rain phenylalanine levels remain constant if blood concentrations exce ed 20 mg/dl. This might be of clinical relevance for the treatment of adolescent and adult PKU patients.