Acute disseminated encephalomyelitis: current controversies in diagnosis and outcome

Acute disseminated encephalomyelitis (ADEM) is a rare inflammatory, demyelinating disorder of the CNS. Only in the past 15 years have larger groups of patients from several geographical areas been reported for comparisons across studies. In spite of the increased recognition of ADEM, the diagnosis of ADEM remains clinical, aided by neuroimaging confirmation, because of the lack of a biological marker. The diagnosis may be difficult, given that several diseases may present similar to ADEM. The controversial existence of multiphasic forms necessitates a continuous evaluation of the diagnosis by tracking subsequent events. Despite proposed consensus criteria, the diagnostic criteria employed to characterize ADEM range widely among the largest reported cohorts to date. This review comprehensively evaluates the current knowledge and controversies that surround ADEM, with special consideration of the distinction between ADEM and other demyelinating diseases such as multiple sclerosis. In addition, we present implications of the current knowledge of ADEM for both research and clinical practice.