**2.4 Acute disseminated encephalomyelitis**

ADEM is an acute immune-mediated demyelinating encephalopathy with or without myelitis that is usually preceded by a viral infection. ADEM may present with prodromal signs such as fever, vomiting, or headache. Ataxia is a common feature (42%). Other neurological manifestations include long pathway signs (71%), acute hemiparesis (64%), consciousness impairment (58%), cranial nerve palsies (37%), meningeal reaction (36%), seizures (29%), visual loss due to optic neuritis (19%) and spinal cord involvement (20%) [16]. Diagnosis requires the demonstration of characteristic multifocal demyelinating lesions on MRI (**Figure 1**). The approximate incidence of ADEM is 0.2–0.4 per 100,000 children annually [16, 17]. The most common age of presentation is 3 to 7 years [18].

Current first-line therapy is methylprednisolone at 20–30 mg/kg IV once a day for 3–5 days, followed by a corticosteroid taper over 4–6 weeks [19]. ADEM typically has a monophasic evolution with a favourable prognosis with complete recovery in almost all the patients usually over 4–6 weeks [20]. There is evidence that a minority of children may have persistent and long-term effects, such as physical or cognitive deficits, including attention difficulties and poor executive functioning [21, 22].
