Acute disseminated encephalomyelitis and demyelinating disease — branching viva

Opening branch — the encephalopathic six-year-old

A previously well six-year-old presents four days after a viral illness with fever, drowsiness, irritability, a right hemiparesis, and slurred speech, and the brain MRI shows diffuse, bilateral, poorly demarcated white-matter lesions with thalamic involvement. The candidate must first recognise this as a first central nervous system demyelinating event and apply the International Pediatric Multiple Sclerosis Study Group definition: the polysymomatic deficit plus encephalopathy - an altered conscious level not explained by fever alone - establishes the acute disseminated encephalomyelitis phenotype, distinguished from a non-encephalopathic clinically isolated syndrome by that one feature. The teaching point is that encephalopathy is the mandatory discriminator and that the post-infectious timing and the diffuse bilateral white and deep grey matter lesion pattern are supportive but not the defining feature. ^[1]

The examiner probes the acute treatment. The candidate states that the first-line therapy for every demyelinating event is high-dose intravenous methylprednisolone at 20 to 30 mg/kg per day to a maximum of 1 g per day for three to five days, begun as soon as infection is reasonably excluded, with the workup in parallel. The escalation rule is stated precisely: if the deficit has not improved after forty-eight to seventy-two hours, the event is steroid-refractory and the response is intravenous immunoglobulin (2 g/kg total) or plasma exchange, not a repeat steroid course. The antibody triad - serum MOG-IgG and AQP4-IgG by cell-based assay, and cerebrospinal-fluid oligoclonal bands - resolves the diagnosis and governs the long-term treatment. ^{[1] [4]}