MRI - Leukodystrophy: A 22-month-old boy was noted by his pediatrician to be developmentally delayed with an enlarged head circumference of 55 cm. (normal adult = 55 cm.). This MRI scan (T2-weighted axial image) reveals a diffuse increase in white matter signal intensity, especially in the frontal regions. Note the preservation of gray matter structures, including the basal ganglia and cortical ribbon. The specific etiology of leukodystrophy is occasionally determined by means of blood or urine studies, but often brain biopsy is required.