Diffusion MRI findings in neonatal brain abscess.

In neonates and infants, bacterial brain abscess is rare, and the diffusion weighted MR imaging appearance of such abscesses has not been reported. We report the diffusion weighted MR findings of a brain abscess in a 25-day-old boy. The lesion initially had a large cystic component with some high-signal pyogenic material inside on diffusion-weighted (b=1000 sec/mm(2))images. The ADC value of this material was low (0.59 x 10(-3) mm(2)/sec), compared to the value from normal cerebellar parenchyma (0.78 x 10(-3) mm(2)/sec). The unusual initial appearance mimicked a cystic tumor. The lesion markedly decreased in size over 20 days after antibiotic therapy with persistent high-signal pyogenic material. In addition, at the initial presentation b=1000 sec/mm(2) images revealed high-signal changes in the brain parenchyma compressed by markedly dilated ventricles, consistent with ischemia. Also, ADC values of perilesional vasogenic edema (1.74 x 10(-3) mm(2)/sec), and that of transependymal resorption of CSF (1.56 x 10(-3) mm(2)/sec) were noted at the initial stage.