Synopsis
Distinguish the usually monophasic encephalopathic demyelinating illness ADEM from infection, MS, MOG-associated disease and structural mimics, then deliver safe acute and recovery care.
- ADEM is an acute inflammatory demyelinating disorder that is commonest in children and often follows an infection; it is much less commonly the first diagnosis in an adult.
- Encephalopathy is a defining clinical feature: altered behaviour, irritability, drowsiness or reduced consciousness accompanies polyfocal neurological deficits.
- MRI usually shows large, bilateral, poorly demarcated T2 or FLAIR lesions in subcortical and central white matter, deep grey nuclei, brainstem, cerebellum or spinal cord.
Key red flags
Days to weeks after a febrile illness, a child becomes unusually irritable, confused or sleepy and develops multifocal weakness, ataxia, cranial-nerve findings or seizures.
Investigation priorities
Demonstrate the distribution and age of demyelinating lesions while excluding tumour, abscess, stroke, PRES and other structural encephalopathies.
Management branches
A child or adult has altered consciousness or behaviour with multifocal neurological signs.
- Stabilise airway, breathing and circulation, check glucose and electrolytes, treat seizures promptly and escalate signs of cerebral oedema or respiratory weakness to paediatric or adult critical care.
- Obtain urgent MRI and, when safe, CSF for microbiology and inflammation; give empiric aciclovir and antibacterial cover according to the encephalitis or meningitis pathway while infection remains credible.
Key medicines
Intravenous methylprednisoloneAdults commonly receive 1 g daily for three to five days; paediatric dosing is weight-based and specialist-led.
Intravenous immunoglobulinA specialist course commonly totals 2 g/kg divided over two to five days.