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).