Acute disseminated encephalomyelitis differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:


No one test established the diagnosis of ADEM. Supporting features include an appropriate viral or vaccination history, an appropriate acute neurologic illness, and consistent features on CNS imaging.

Differential Diagnosis

  • Acute infectious encephalitis
    • Herpes simplex virus
      • Most common and treatable form of infectious encephalitis
      • Usually due to Human herpesvirus 1 (HSV-1), though HSV-2 accounts for 5%
      • One-third occur during primary infection
      • Most commonly involves the temporal and frontal lobes; speech disorders, bizarre behaviors, and gustatory and olfactory hallucinations are common
      • Fever present in 90%. Altered state of consciousness present in most.
      • Associated with scattered hemorrhages, CSF red cells
      • Treated with acyclovir 10 mg/kg IV q8h; reduces mortality and morbidity if started early enough. Untreated mortality is 70%.
    • Epstein-Barr virus
    • Lyme disease
    • Arborviruses
      • Viruses transmitted by arthropods, mosquitos and tick
      • Most common in the summer and fall (in contrast to winter and spring presentations of measles, mumps and VZV).
      • Present with:
        • Fever
        • Headache
        • Gastrointestinal symptoms
        • Neurologic disease typically presents day 2 or 3
        • CSF typically shows elevated protein, a few hundred white blood cells, normal glucose
        • No specific treatment
    • Eastern equine encephalitis
      • Presents with flu-like symptoms, fever, headache, vomiting, seizures, and progressive neurologic disease
      • Seen mostly along the east coast of the U.S.
      • Mosquito and bird vectors
      • Most common in those <15 or >55 years of age
      • Most virulent of arborviruses: 70% mortality
    • Western equine encephalitis
      • Mosquito vector
      • Young children
      • Often asymptomatic
      • Western U.S.
    • California encephalitis
      • Worldwide
      • Most common in school-age children
      • Mosquito vector
      • Gastrointestinal (GI) symptoms common
    • St. Louis encephalitis
      • Wild bird reservoir
      • Wild bird – mosquito cycle
      • Throughout U.S.
    • Japanese encephalitis
      • Flavivirus endemic in Southeast Asia from India to Japan
      • Mosquito transmission
      • Vaccine available
    • Mycoplasma infection
    • Cytomegalovirus infection
    • Ehrlichiosis
    • Measles
    • VZV/chickenpox
    • Mumps encephalitis
      • CNS features present in ~1% of cases
      • Not all patients have parotitis
      • Most common in winter and spring
      • Most patients recover completely, but some patients left with deafness, seizure, and mental retardation
      • Confirmed via culture or serology
    • Mycoplasma
    • Bacterial meningoencephalitis
    • Other infectious encephalitidies
  • Acute multiple sclerosis (MS)
    • MS may not be possible to exclude, and to some extent depends upon the natural history of the patient’s disease; MS is typically a chronic disease with a recurrent or progressive course, and ADEM is usually an acute monophasic disease. Both diseases are characterized by demyelination; it is acute in ADEM, and sustained or progressive in MS. It is sometimes best to refer to the illness as an “acute demyelinating disease”, until the disease course declares itself.
    • Simultaneous optic nerve, brain and spinal cord involvement, as well as meningismus, drowsiness, coma and seizures, are features suggestive of ADEM instead of MS.
    • Optic nerve involvement is typically bilateral in ADEM, and unilateral in MS. Transverse myelopathy is usually complete in ADEM, and partial in MS.
    • CSF protein is usually elevated in ADEM, and is often normal in MS. CSF lymphocyte counts >50, and CSF polys are also uncommon in MS.
    • In ADEM in contrast to MS, most MRI lesions enhance with gadolinium, suggestive that all lesions are active, and that the disease is therefore monophasic.
  • Hypoxic encephalopathy
  • Cerebrovascular disease
  • CNS vasculitis
  • Lupus cerebritis
  • Toxin effect
  • Acute toxic hepatoencephalopathy – Reye’s syndrome
    • Acute liver and CNS disease in children under 15 years of age, characterized by progressive liver and CNS disease, commonly in association with the use of salicylates.
    • Often follows a viral infection, especially chickenpox or influenza.
    • Patients often present with vomiting and progressive neurologic disease. Hypoglycemia is common. Jaundice is usually not a prominent feature.
    • The liver is enlarged and evidence of liver disease includes elevated transaminases, prothrombin time, and ammonia, hypoglycemia, and metabolic acidosis. Cerebral edema and brain neuronal degeneration occurs.
    • Mitochondria dysfunction occurs in the liver, brain and muscle. Liver cells show microvacuolization, as do renal tubules.
    • Mortality approaches 50%.