Acute disseminated encephalomyelitis (ADEM) is a rare inflammatory, demyelinating disorder of the CNS, now recognized as a distinct entity and not a multiple sclerosis variant. ADEM is typically characterized by an acute and monophasic course manifesting with encephalopathy and polyfocal neurological deficits. The disorder is mainly a condition of the pediatric age group, but on rare occasions, adults and elderly patients can also be affected.
In spite of the increased recognition of ADEM, its diagnosis remains clinical and is greatly supported by radiological techniques such as MRI of the brain and spinal cord, because of the lack of a biological marker. The diagnosis may be difficult, given that several diseases may present similar to ADEM.
This review evaluates the current knowledge in the diagnosis of ADEM and its variants (Bickerstaff encephalitis and acute hemorrhagic leukoencephalitis) and other acute parainfectious syndromes that commonly affect children, such as acute necrotizing encephalopathy of childhood (ANEC) and mild encephalopathy with a reversible splenial lesion (MERS).
This chapter includes special consideration on the value of clinical neuroradiology in the diagnoses of these entities and in the distinction between ADEM and other immune-mediated inflammatory demyelinating diseases, in particular multiple sclerosis.
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