Table 5.

Criteria for diagnosis of acute disseminated encephalomyelitis (ADEM)

Subacute encephalopathy (altered level of consciousness, behavior, or cognitive function)

Evolution over 1 week to 3 months; new symptoms, including focal/multifocal demyelinating syndromes, such as optic neuritis or myelitis within the first 3 months from onset are allowed, as long as they are not separated by a period of complete remission from the initial symptoms (in which case the diagnosis is MS)

Accompanied by improvement or recovery although residual neurological deficits may be present

MRI shows predominantly symptomatic white matter lesions that

Are acute (remote lesions accompanied by encephalomalacia cast doubt on the diagnosis if there is no previous explanation for them other than remote demyelinating disease)

Are multiple but rarely a single large lesion

Are supra- or infra-tentorial or both

Generally include at least one large (1–2 cm diameter) lesion

Variably enhance with gadolinium (gadolinium enhancement is not required)a

May be accompanied by basal ganglia lesions, but their presence is not required

^aSimultaneous enhancing lesions may occur but are not required; when present, this MRI finding may increase suspicion of ADEM, but should also lead to suspicion of other causes (e.g., vasculitis or lymphoma).