Acute disseminating encephalomyelitis (ADEM) in children

  • Follows an infection (viral) or vaccination
  • Post infectious inflammatory immune-mediated process
  • Focal neurologic deficits, headache, fever, altered consciousness
  • Monophasic usually
  • Can involve multiple sites in brain and spinal cord
  • Full recovery in children apart from 10-30% which have residual deficit
  • If episodes relapse in time or in place, consider multiple sclerosis as differential
  • ADEM patients have no residual lesions on follow up, while MS patients show new lesions 
  • Asymmetric areas of demyelination
  • High signal in T2w images with swelling 
  • Subcortical white matter of both hemispheres
  • Can sometimes involve cerebellum and spinal cord
  • Cortex and deep grey matter can be involved but is less
  • Free diffusion in all lesions
  • Sometimes a more fulminant form can show hemorrhagic lesions 
  • Periventricular and callosal lesions favor MS
  • Deep grey matter involvement favors ADEM more than MS
  • Viral encephalitis tends to be cortical based and also shows diffusion restriction due to vasculitis 
  • Apart from MS, consider autoantibody associated inflammatory demyelination like aquaporin-4 associated neuromyelitis optics spectrum disorders (NMSODs) and encephalomyelitis associated with myelin oligodendrocyte glycoprotein (MOG) autoantibody