Acute Disseminated Encephalomyelitis is a monophasic CNS inflammatory disease that mainly occurs in children and adults younger than 40 years. The disorder can be triggered by an acute systemic infection or vaccination. Symptoms include cranial nerve palsies, ataxia, hemiparesis, myelopathy, or optic neuritis. Myelin oligodendrocyte glycoprotein (MOG) antibodies can transiently occur in almost 50% of children with acute disseminated encephalomyelitis.

Diagnosis can be made when all 5 of the following criteria have been met (Graus et al. 2016 A Clinical Approach to the diagnosis of autoimmune encephalitis)

1. A first multifocal, clinical CNS event of presumed inflammatory demyelinating cause
2. Encephalopathy that cannot be explained by fever
3. Abnormal brain MRI:
   • Diffuse, poorly demarcated, large (>1–2 cm) lesions predominantly involving the cerebral white matter on T2-weighted FLAIR imaging that can be present in the supratentorial white matter, basal ganglia, brainstem, cerebellum, and spinal cord, with or without contrast enhancement
   • T1-hypointense lesions in the white matter in rare cases
   • Deep grey matter abnormalities (e.g. – thalamus or basal ganglia) can be present
4. No new clinical or MRI findings after 3 months of symptom onset

Reasonable exclusion of alternative causes

See ADEM Fact Sheet for more information