Differences in water diffusion and lactate production in two different types of postinfectious encephalopathy.

We compared two different types of postinfectious encephalopathy using magnetic resonance imaging (MRI), including diffusion-weighted images and MR spectroscopy. Acute disseminated encephalomyelitis (ADEM) and acute necrotizing encephalopathy (ANE) showed different distribution of abnormal intensity areas and different diffusion of water measured by diffusion-weighted imaging (DWI). Proton MR spectroscopy (MRS) showed lactate production in both cases, which returned to a normal range; the rate of increased lactate production was much lower in the ANE case. Water diffusion showed a difference in pathophysiological background between the two encephalopathies, but the lactate elevation observed by proton MRS did not correlate with clinical severity.