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Acute Disseminated Encephalomyelitis (ADEM)

Last Updated: October 1, 2018

Open Table of Contents: Acute Disseminated Encephalomyelitis (ADEM)

Figure 1: In this patient, with a recent history of upper respiratory tract infection, there is clear asymmetric subcortical FLAIR hyperintense signal (top row left) within the bilateral temporal and parietal lobes with subtle corresponding hypointense signal on T1 (top row right). The postcontrast image (bottom row) demonstrates faint peripheral enhancement.

Figure 2: Axial T2-FS (left) and sagittal T1 post-contrast (right) images of the head demonstrate expansile FLAIR hyperintensity in the bilateral cerebellar hemispheres. There is a flocculent appearance of the signal abnormality with heterogeneous internal contrast enhancement. The patient presented with history of viral illness, nausea, vomiting, and multiple neurologic deficits on exam. The lesions subsequently resolved following treatment with IVIG and steroids.

Description

  • Auto-immune mediated demyelination typically occurring shortly after immunization or upper respiratory viral infection

Pathology

  • Inflammation surrounding vessels, edema and perivenous demyelination

Clinical Features

  • Symptoms
    • Fever, malaise, myalgia, lethargy and potentially coma
    • Nonspecific neurologic findings related to location of demyelination
  • Age

    • Most commonly in children
  • Gender

    • M > F
  • Prognosis

    • 10-30% mortality

Imaging

  • General
    • Multifocal areas of white matter demyelination typically within a few weeks of immunization or viral infection
    • Cerebral, cerebellar and spinal cord lesions
    • Very little mass effect
  • Modality specific

    • CT
      • Often normal at presentation but may have multiple ill-defined regions of hypoattenuation
      • Variable enhancement
    • MR

      • T1WI
        • Ill-defined regions of hypointensity
      • T2WI/FLAIR

        • Multifocal asymmetric white matter hyperintensities with surrounding edema
        • Typically, symmetric signal abnormality within the basal ganglia and thalami
      • DWI

        • Diffusion restriction is uncommon and portends a poor prognosis
      • Contrast

        • Incomplete rim of enhancement
        • Cranial nerve enhancement is common
  • Imaging Recommendations

    • MR with contrast of the brain and spinal cord
  • Mimic

    • While multiple sclerosis, vasculitis and PRES are common mimics. ADEM may also mimic infiltrative glioma or CNS lymphoma in an immunocompromised patient, particularly when involving the corpus callosum. The incomplete rim of enhancement and clinical history of recent immunization or upper respiratory tract infection can help clinch the diagnosis.

For more information, please see the corresponding chapter in Radiopaedia, and the Acute Disseminated Encephalomyelitis chapter in the Spinal Cord Disorders sub-volume of the Neurosurgical Atlas.

Contributor: Sean Dodson, MD; Jacob A. Eitel, MD

DOI: https://doi.org/10.18791/nsatlas.v1.03.02.02

References

Honkaniemi J, et al. Delayed MR Imaging Changes in Acute Disseminated Encephalomyelitis. AJNR. 2001; 22:1117-24.

Kanekar S, et al. A Pattern Approach to Focal White Matter Hyperintensities on Magnetic Resonance Imaging. Radiol Clin North Am. 2014; 52(2):241-61.

Mader I, et al. Acute Disseminated Encephalomyelitis: MR and CT Features. AJNR. 1996; 17:104-09.

Noorbakhsh F, et al. Acute Disseminated Encephalomyelitis: Clinical and Pathogenesis Features. 2008; 26(3):759-80.

Rossi A. Imaging of Acute Disseminated Encephalomyelitis. Neuroimaging Clin N Am. 2008; 18(1):149-61.

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