Skip to navigation MENU Navigation National Multiple Sclerosis Society Search Acute Disseminated Encephalomyelitis (ADEM) IN THIS ARTICLE Overview What causes ADEM? Who gets ADEM, and when? How is ADEM different from MS? Overview Acute Disseminated Encephalomyelitis (ADEM) is a brief but intense attack of inflammation (swelling) in the brain and spinal cord and occasionally the optic nerves that damages the brain’s myelin (the white coating of nerve fibers). Other terms used to refer to ADEM include post-infectious encephalomyelitis and immune-mediated encephalomyelitis. ADEM is sometimes difficult to distinguish from multiple sclerosis (MS) because the symptoms common to both "demyelinating" disorders include loss of vision, weakness, numbness and loss of balance. Both ADEM and MS involve immune-mediated responses to myelin in the brain and spinal cord. What causes ADEM? The cause of ADEM is not clear but in more than half of the cases, symptoms appear following a viral or bacterial infection, usually a sore throat or cough and very rarely following vaccination. ADEM is thought to be an autoimmune condition where the body’s immune system mistakenly identifies its own healthy cells and tissues as foreign and mounts an attack against them. This attack results in inflammation. Auto-antibodies directed against a component of myelin called myelin oligodendrocyte glycoprotein (MOG) are found in 36-64% of children with ADEM. Most cases of ADEM begin about 4 to 14 days after an infection. In some cases of ADEM, no preceding event is identified. Who gets ADEM, and when? Although ADEM can appear at any age, children are more likely than adults to develop it. More than 80 percent of childhood cases occur in patients younger than 10 years. Most of the remaining cases occur between the ages of 10 and 20 but ADEM is sometimes (rarely) diagnosed in adults. ADEM is thought to affect 1 in every 125,000 to 250,000 individuals in a given year. Five percent of these cases could be associated with vaccination. ADEM appears a little more frequently in boys than girls (about 60 percent of the time) with a male to female ratio of 1.3:1. ADEM appears more often in winter and spring. ADEM occurs in all parts of the world and in all ethnic groups. How is ADEM different from MS? In most but not all cases, ADEM occurs only once, while patients with MS have further, repeated attacks of inflammation in their brains and spinal cords. In most cases, ADEM patients do not develop new scars on a repeat MRI scan whereas MS patients typically experience new scars on their follow-up MRI scans. Typical symptoms of ADEM such as fever, headache and confusion, vomiting, and seizures are not usually seen in people with MS, although they can be seen in pediatric MS onset especially in patients younger than 11 years. Sometimes the pattern of MRI abnormalities helps differentiate these two disorders. Most patients with MS are treated with ongoing medication to prevent attacks. Patients with ADEM generally do not require such medication. ADEM occurs more frequently in males; MS more frequently in females. ADEM is more common in children; MS is more common in adults. Reviewed by Elias Sotirchos, MD November 2019 SHARE Share 228 Discover More Here are a few related topics that may interest you Pediatric MS LEARN MORE Transverse Myelitis LEARN MORE Neuromyelitis Optica (NMO) LEARN MORE HTLV-I Associated Myelopathy (HAM) LEARN MORE Previous Next The National MS Society is Here to Help NEED MORE INFORMATION? We Are Here Our MS Navigators help identify solutions and provide access to the resources you are looking for. Call 1-800-344-4867 or contact us online. Contact Us NEWLY DIAGNOSED If you or somone close to you has recently been diagnosed, access our MS information and resources. Start Here Colophon STAY INFORMED JOIN US What Is MS? Symptoms & Diagnosis Treating MS Resources & Support Living Well with MS Research Get Involved Program Calendar About the Society Vision Careers Leadership Cultural Values Our Story Financials News Newsroom MS Prevalence Charitable Ratings Corporate Support Helpful Links Donate Fundraising Events National MS Society Blog COVID-19 Información en Español Glossary Legal Notice/Privacy Policy Site Map Site Tour Contact Us For Professionals Researchers Physicians Nurses Rehabilitation Professionals Mental Health Professionals Health and Wellness Professionals © 2021 The National Multiple Sclerosis Society is a tax exempt 501(c)3 nonprofit organization. Its Identification Number (EIN) is 13-5661935. We use cookies to provide an enhanced experience, to keep our site safe and to deliver specific messaging. By accepting, you consent to the use of all cookies and by declining, only essential cookies will be used to make our website work. More details can be found in our Privacy Policy. Chat Chat