NEURORADIOLOGICAL (MRI) ABNORMALITIES IN PHENYLKETONURIC SUBJECTS - CLINICAL AND BIOCHEMICAL CORRELATIONS

A clinical, biochemical and neuroradiological (MRI) study was performe d in 22 hyperphenylalaninemic patients detected by neonatal screening and early treated (Group A; 5-23 years old, 13 females and 9 males) an d in 5 late detected, symptomatic subjects (Group B; 9-23 years old, 3 females and 2 males). The screening subjects were clustered in a Grou p Al (10 on diet patients), and a Group A2 (12 after end of diet patie nts). On MRI examination (1.5-T magnet, SE T1-weighted 530/22/2, T2-we ighted 2400/15-90/1 sequences, SL 6 mm, gap 1.8) a symmetrical increas e of the T2-weighted signal in the periventricular white matter was fo und in all patients. The periatrial white matter was always involved, the occipital region was affected in 22 cases, the frontal region in 1 6. Concomitant signal decrease on the T1-weighted sequences in the sam e areas with the highest signal intensity on the T2-weighted scans was found in 7 patients (in 3 out of 12 Group A2 and in 4 out of 5 Group B patients). In 6 Group A and in 3 Group B subjects a variable degree of cortical and subcortical atrophy was detected. A significantly posi tive correlation was found between white matter involvement and the de gree of recent exposition to high PHE values. This correlation was als o confirmed when only Group A was examined. Moreover, a significant di fference in neuroradiological involvement was found between Group Al a nd Group A2 subjects, but not between Group A2 and Group B subjects. O ur data suggest that the white matter signal abnormalities, as detecte d by MRI technique, are probably the corollary of the recently sustain ed exposition to high PHE concentration. A longitudinally designed stu dy needs to clarify the prognostic value of the neuroradiological find ings and the nature of their bearing on the clinical status.