Acute disseminated encephalomyelitis in an adult patient. Magnetic resonance and diffusion-weighted imaging findings.

Acute disseminated encephalomyelitis ADEM is an uncommon inflammatory disease of the central nervous system and can be defined strictly as scattered focal or multifocal disseminated inflammation of brain or spinal cord, or both. An ADEM usually reveals patchy demyelinated lesions with a high signal on T2-weighted sequences. Here, we report a case of a 39-year-old man with ADEM. Echo-planar trace diffusion magnetic resonance imaging revealed high signal intensity changes at the lesion sites on b=1000 s/mm2 images, initially suggesting restricted diffusion. On corresponding apparent diffusion coefficient ADC maps, however, the lesions have a high signal intensity and high ADC values, compared with the normal white matter. This was consistent with the presence of elevated diffusion, and hence, vasogenic edema.