1. Ilana Kahn, MD* 1. *Children’s National Health System, George Washington University Medical School, Washington, DC * Abbreviations: ADEM: : acute disseminated encephalomyelitis ADS: : acquired demyelinating syndrome AQP4: : aquaporin-4 ATM: : acute transverse myelitis CNS: : central nervous system CSF: : cerebrospinal fluid IgG: : immunoglobulin G IVIg: : intravenous immunoglobulin MOG: : myelin oligodendrocyte glycoprotein MRI: : magnetic resonance imaging MS: : multiple sclerosis NMO: : neuromyelitis optica NMOSD: : neuromyelitis optica spectrum disorder OCB: : oligoclonal band Most pediatricians report lack of knowledge related to the understanding of the diagnosis and treatment of both acute disseminating encephalomyelitis and acute transvers myelitis. Pediatric providers should understand presenting symptoms, initial diagnostic testing, and acute treatment. Clinicians should know when to refer to a neurologist for evaluation of long-term treatment. After completing this article, readers should be able to: 1. Define and characterize acquired demyelinating syndromes. 2. Identify the prevalence, etiology, and clinical presentations of acute disseminating encephalomyelitis (ADEM) and acute transverse myelitis (ATM). 3. Initiate a diagnostic evaluation, including an evaluation for medical emergencies. 4. Make treatment decisions for acute management. 5. Counsel patients on long-term outcomes after ADEM and ATM. 6. Counsel patients on recurrence risks for multiphasic or chronic demyelinating diseases. Acquired demyelinating syndromes (ADSs) encompass a group of immune-mediated disorders in which there is breakdown of the myelin sheath, the lipid-rich covering around the axon that increases conduction speed and metabolic efficiency of the neuron. ADSs are characterized by a sudden onset of new neurologic symptoms in concurrence with neuroimaging evidence of demyelination. Outcomes vary from full neurologic recovery to long-term severe disability. ADSs are characterized based on location and frequency of the demyelinating events. Location is either focal, limited to 1 specific location, or polyfocal, involving several areas of the central nervous system (CNS). Frequency is classified as monophasic or multiphasic, meaning either a single 1-time event or a recurrent, potentially chronic, disease. It is important to keep at the forefront of your mind, however, that over time what seems to be a monophasic event may, in fact, turn out to be the initial or first attack of a multiphasic disorder. (1) …