MR imaging of anisotropically restricted diffusion in the brain of neonates and infants.

Brain MR examinations were performed on one normal and 30 abnormal neonates and infants with a variety of clinical problems using pulsed gradient spin echo (PGSE) sequences sensitized in different directions to detect changes due to anisotropically restricted diffusion of water within the brain. Anisotropically restricted diffusion was demonstrated within white matter, which appeared to be myelinated with T1-weighted inversion recovery or spin echo sequences and within white matter where the presence of myelin was not demonstrated with these sequences. Cysts and fluid collections were recognised by their low signal intensity using PGSE sequences in the subcortical regions, lentiform nuclei, and periventricular regions. An intracerebral hematoma and a subdural hematoma showed a high signal intensity with PGSE sequences consistent with isotropically restricted diffusion. Chronic infarction displayed a low signal intensity consistent with relatively free isotropic diffusion. Patients with leukodystrophy associated with congenital muscular dystrophy showed an anisotropic pattern with different components of the abnormality present on images with sensitization in different directions. The corticospinal tracts failed to show highlighting in three cases where conventional imaging was normal. In several patients with a history of birth asphyxia, asymmetry and a relative reduction in signal intensity were seen in the corticospinal tracts.