Brain MRI Findings in PKU Patients

Kim, Young Hee; Suh, Eun Sook; Lee, Dong Whan; Hong, Hyun Sook

Abstract

PURPOSE: Abnormalities of magnetic resonance imaging(MRI) of the brain occur in some patients with phenylketonuria(PKU). The purpose of this study was to evaluate relation between MR findings, age and serum phenylalanine level.
METHODS
We investigated sixteen patients with biochemically documented PKU who also underwent MRI. Typical classic form was in thirteen patients, atypical in other two patients and malignant hyperphenylalaninemia in the other two patients. We evaluated signal intensity, the distribution of abnormal signal intensity, and the extent of the brain atrophy in MRI, and possible clinical correlation between age and serum phenylalanine level and abnormal signal intensity.
RESULTS
MRI scans revealed areas of abnormally increased signal intensity on T2- weighted images in 10(62%) patients, preferably involving the parieto-occipital lobes. In one advanced case, the high signal intensity of both the parietal and frontal lobes was seen on T2-weighted images, and brain atrophy and gyriform enhancement on contrast enhanced T1-weighted images. In six(38%) patients, the findings were normal. No abnormalities were found in the basal ganglia, brain stem and cerebellum. Nine patients were under age of 5 years old. There were no remarkable difference in the average serum phenylalanine levels for the various groups having different degree of MRI abnormalities(normal, mild, moderate, and severe - 26,4 mg/dL, 27.6 mg/dL, 28.2 mg/dL, and 20.8 mg/dL, respectively).
CONCLUSION
Although MR findings were not specific, PKU patients showed symmetrical high signal intensity, predominantly in the peritrigonal region. In the advanced case, on T2-weighted images, high signal intensity extended to the periventricular and subcortical white matter. There was no correlation between age, serum phenylalanine level and severity of high signal intensity.