Acute disseminated encephalomyelitis (ADEM) is a rare autoimmune disease, which causes inflammation (swelling) and damage to the protective covering of the fibers in the central nervous system.
What is Acute Disseminated Encephalomyelitis (ADEM)?
The central nervous system – the brain, optic nerves and spinal cord – is made of nerves (fibers) that control bodily movement. When a child experiences ADEM, the body’s immune system mistakenly attacks the nerves, causing swelling and serious damage to the myelin around the nerves (demyelination). Myelin acts as insulation (like a plastic covering on electrical wires), allowing the body’s electrical impulses that control normal functions to activate. When the myelin is damaged, it can slow down the body’s internal communication that manages movements and reactions.
ADEM is a brain disease that is more common in children and adolescents than adults. A recent study shows that it is especially rare, with only approximately three to six cases per year in the U.S., U.K. and Australia combined.
What are the signs and symptoms of Acute Disseminated Encephalomyelitis (ADEM)?
Symptoms of ADEM can range, depending on the cause, and may impact multiple areas of the body and functions. The damage can also lead to other diseases that may present as symptoms.
There can be some confusing overlap between multiple sclerosis (MS) and ADEM symptoms. Both are demyelinating disorders caused by autoimmune attacks. But unlike ADEM, MS attacks can happen multiple times, repeatedly damaging the nervous system. MS can occur in children but presents more frequently in adults. ADEM can also rarely lead to MS.
Post-infectious ADEM symptoms typically begin within a couple of weeks after a viral or bacterial illness. Post-immunization ADEM neurologic symptoms often appear 4 to 13 days after a vaccination. Symptoms can include the following:
Initial symptoms (not typically seen in MS)
These include damage to the brain and occur quickly.
- Behavioral changes
- Change in consciousness (range from lack of energy to coma)
- Inattentive (can’t focus on simple tasks, shift focus or maintain attention for long periods of time like reading a book)
Other neurological symptoms
- Acute hemiparesis (muscle weakness on one side only)
- Cerebellar ataxia (decreased muscle coordination)
- Cranial neuropathies (damage of cranial nerves)
- Decreased voluntary movements (like walking)
- Optic neuritis (ON) (decreased vision and eye pain)
- Transverse myelitis (TM) (including impaired breathing, bowel/bladder problems and muscle weakness)
What are the causes of Acute Disseminated Encephalomyelitis (ADEM)?
Like many other autoimmune diseases in children, the exact cause of ADEM is still being investigated. However, there are some common risk factors.
- Post-infectious ADEM – The autoimmune attack that causes ADEM may be triggered by a viral or bacterial infection, which occurs in approximately 50-75% of the cases. This can include measles, mumps,Epstein-Barr (mono), rubella (German measles), influenza and enterovirus infections (including hand-foot-and-mouth). Studies have shown that most post-infectious ADEM cases occur seasonally in the winter and spring.
- Post-immunization ADEM – Although there is a relationship between immunizations and immune attacks, a direct connection to ADEM hasn’t been established and occurs in less than 5% of cases. Some immunizations that have been associated with this condition are rabies, hepatitis B, influenza, DPT (diphtheria/pertussis/tetanus), MMR (measles/mumps/rubella), pneumococcus (pneumonia), meningitis, polio, smallpox and varicella (chicken pox).