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Acute Disseminated Encephalomyelitis


Learning objectives

  • Learning
  • Understand
  • Integrate
  • Reflect

Many patients initially diagnosed with ADEM subsequently develop clinically definite MS upon long-term follow-up.

Introduction
  • Relevant as a stroke mimic and so should be identifiable
  • Acute disseminated encephalomyelitis mainly affects children but can affect adults
  • Inflammatory condition of brain and spinal cord that damages myelin
  • May follow a viral illness or have another precipitant
Aetiology
  • Classically acute and monophasic but not always
  • Usually affects young adults and children
  • Pathological hallmark of ADEM is perivenular inflammation with limited "sleeves of demyelination"
  • CSF elevated IFN-gamma, IL-6, and IL-8
Precipitants
  • Bacterial infections: mycoplasma, Gram negative organisms, salmonella typhi
  • Vaccination for measles, mumps, or rubella.
  • Post viral: Measles, varicella, rubella, Herpes-zoster, Infectious mononucleosis
  • Cerebral malaria
Clinical
  • Fever, meningism, seizures, coma, usually monophasic but not always
  • Weakness, hemianopia, neglect
Investigations
  • CT: may show cerebral oedema
  • MRI scan: large symmetrical lesions with basal ganglia and thalamus involved.
  • LP: raised protein and slight increase in WCC in 80%.Protein > 100mg/dl. No oligoclonal bands
  • Brain biopsy: consistent with demyelination.
Differentials
  • Multiple sclerosis
  • Susac syndrome
  • Progressive multifocal leukoencephalopathy
Management
  • Mortality is up to 30%
  • Treat with high dose IV Methylprednisolone
  • Alternatives include Plasmapheresis, IVIG and Rituximab
References and further reading