Acute Disseminated Encephalomyelitis (ADEM)
Last Updated: October 1, 2018
- Auto-immune mediated demyelination typically occurring shortly after immunization or upper respiratory viral infection
- Inflammation surrounding vessels, edema and perivenous demyelination
- Fever, malaise, myalgia, lethargy and potentially coma
- Nonspecific neurologic findings related to location of demyelination
- Most commonly in children
- M > F
- 10-30% mortality
- 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
- Often normal at presentation but may have multiple ill-defined regions of hypoattenuation
- Variable enhancement
- Ill-defined regions of hypointensity
- Multifocal asymmetric white matter hyperintensities with surrounding edema
- Typically, symmetric signal abnormality within the basal ganglia and thalami
- Diffusion restriction is uncommon and portends a poor prognosis
- Incomplete rim of enhancement
- Cranial nerve enhancement is common
- MR with contrast of the brain and spinal cord
- 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.
Contributor: Sean Dodson, MD; Jacob A. Eitel, MD
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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