Acute disseminated encephalomyelitis or multiple sclerosis: can the initial presentation help in establishing a correct diagnosis?

Abstract

The differential diagnosis of CNS white matter disease is broad, and can be divided into vascular, metabolic, infective, or inflammatory aetiologies. Isolated inflammatory disorders of the CNS are often associated with demyelination, and the two terms (inflammatory and demyelinating) are often used in conjunction. When the disease is monophasic, the term acute disseminated encephalomyelitis (ADEM) is used. ADEM typically occurs as a post-infectious phenomenon, and by definition, must be an isolated (monophasic) episode. If a relapse occurs shortly after the ADEM presentation in association with a further infection or steroid withdrawal, the term MDEM (multiphasic disseminated encephalomyelitis) is used. When there are relapses or progressive disease, the term multiple sclerosis (MS) is used (for full recommended diagnostic criteria for multiple sclerosis refer to McDonald and colleagues).

Figure 1

Diagnostic dilemma: are ADEM and MS separate clinical entities or part of the same demyelinating spectrum?

Figure 2

(A) MRI brain (T2 weighted) in MS showing well demarcated lesions in the region of the periventricular white matter. (B) MRI brain (T2 weighted) in ADEM showing a large mass-like lesion in the white matter. (C) MRI brain in ADEM showing multiple large lesions with poorly defined margins and relative periventricular sparing.

Figure 3

Clinical and investigation differences between ADEM and MS (trends only). *MR lesions other than white matter.