This young woman presented with progressive left hemiparesis after having had a viral infection a week earlier. This MRI demonstrates bilateral asymmetric lesions with open ring enhancement characteristic of demyelination. Note that restricted diffusion is not seen centrally (usually seen in cerebral abscesses) but at the advancing rim of demyelination. She was treated with steroids, and rapidly improved.
Acute disseminated encephalomyelitis is, as the name would suggest, acute inflammation and demyelination of white matter typically following a recent (1 – 2 weeks prior) viral infection or vaccination. Grey matter, especially that of the basal ganglia, is also often involved, but to a lesser extent, as is the spinal cord. It is usually a monophasic illness (c.f multiple sclerosis), although within the episode individual lesions may be of varying stages of evolution.
Typically ADEM presents in children, however cases in all ages have been reported.
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