What is acute disseminated encephalomyelitis (ADEM)?
Acute disseminated encephalomyelitis (ADEM) is an intense attack of inflammation (swelling) in the brain and spinal cord and occasionally the optic nerves that damages the brain’s myelin (the coating of nerve fibers). Other terms used to refer to ADEM include “post-infectious encephalomyelitis” and “immune-mediated encephalomyelitis.”
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. Most often, ADEM begins about 4 to 14 days after an infection. Sometimes there is no infection before someone develops ADEM and the exact cause is unclear.
ADEM is sometimes difficult to distinguish from multiple sclerosis because the symptoms common to both demyelinating disorders can include loss of vision, weakness, numbness and loss of balance or coordination. Both ADEM and MS involve immune-mediated damage to myelin in the brain and spinal cord caused by inflammation.
In both diseases, 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 damaging inflammation. Auto-antibodies directed against a component of myelin called myelin oligodendrocyte glycoprotein (MOG) — evidence of this immune attack — are found in 36-64% of children with ADEM.
Symptoms of ADEM can come on rapidly, within a few days. The location of the inflammation (swelling) within the brain, spinal cord and optic nerves determines what symptoms may occur, including:
- Headache (can be prolonged and severe in children)
- Nausea and vomiting
- Neurological changes including
- Confusion, drowsiness or coma
- Numbness or tingling (sensory changes)
- Trouble swallowing
- Trouble with vision, often in both eyes (optic neuritis)
- Unsteady walk (ataxia)
- Weakness in the arms or legs
Tools for diagnosing ADEM
Although ADEM can appear at any age, children are more likely than adults to develop it. More than 80% of childhood cases occur in patients younger than 10 years old. Most of the remaining cases occur between the ages of 10 and 20. In rare instances, ADEM is diagnosed in adults. ADEM is thought to affect 1 in every 125,000 to 250,000 individuals each year. ADEM appears slightly more frequently in those assigned male at birth than those assigned female, 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.
Some key differences help distinguish ADEM from MS:
- In most but not all cases, ADEM occurs only once. Patients with MS have further, repeated attacks of inflammation in their brain and spinal cord.
- In most cases, ADEM patients do not develop new damage on a repeat MRI scan whereas MS patients more often experience new damage 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 old.
- The pattern of damage seen on MRI can be different for ADEM and MS.
- Most patients with MS are treated with ongoing medications to prevent attacks. Patients with ADEM generally do not need ongoing medication.
- ADEM occurs more frequently in males. MS more frequently in females.
- ADEM is more common in children. MS is more common in adults.
ADEM is a rare disease and no medications have been specifically approved by the U.S. Food and Drug Administration (FDA) to treat it. Intravenous (infusion through the vein), high-dose steroids are the standard treatment for ADEM. They are given over several days to reduce the inflammation of the brain, optic nerve and spinal cord.
If this therapy does not improve symptoms, the following therapies may be tried:
- Plasma exchange (PLEX) for severe attacks or if no improvement occurs with high-dose steroids.
- PLEX involves removing blood from the body through a needle and tubing.
- Through a series of steps, the plasma (the liquid part of the blood) is separated from blood cells and replaced with an artificial plasma substitute. The plasma substitute and blood cells are combined and returned to the body intravenously.
- The procedure lasts several hours and may be repeated multiple times over a number of days.
- Intravenous immunoglobulin (IVIG) is a treatment made from purified antibodies from healthy blood plasma donations.
- Plasma is the liquid part of the blood. The medication is given through a drip infusion through a vein in your arm and takes several hours to complete.
- IVIG has been shown to reduce the activity in certain immune diseases by decreasing inflammation.
What happens after ADEM treatment
Most children make a complete or nearly complete recovery from ADEM, including children with severe symptoms. Most begin to feel better within days though it can take up to one year for symptoms to resolve. Some patients have minor, ongoing symptoms such as blurred vision, weakness, numbness and/or incoordination.
Support for people affected by ADEM
The following organizations offer resources and information for people who live with ADEM and their families:
Reviewed by Elias Sotirchos, MD, and Shuvro Roy, MD, April 2023.