Acute disseminated encephalomyelitis (ADEM) is a neurological disorder characterized by brief but widespread attacks of inflammation (swelling) in the brain and spinal cord that damages myelin. Myelin is the whitish protective coating over nerves that helps with electrical nerve signaling. ADEM often appears following a viral or bacterial infection and sometimes (rarely) following a vaccination. It is sometimes misdiagnosed as the first severe attack of multiple sclerosis, since the symptoms and appearance of damage to the white matter may be similar. ADEM may be an autoimmune condition, in which the body’s immune system mistakenly identifies and attacks healthy cells and tissue.

ADEM can occur in people of any age, but it most often occurs in young children.

Causes: 
ADEM is caused by inflammation in the brain and/or spinal cord. Inflammation is the body’s normal immune response to infections and injuries. 

The inflammation of ADEM does not fight an infection or repair an injury—instead, it actually attacks the body’s nervous system. This type of attack against one’s own body is described as an autoimmune reaction.

The inflammatory process in ADEM attacks myelin in the brain and spinal cord. Myelin is a type of fat that insulates nerves to help them function efficiently. The inflammatory process of ADEM affects the white matter of the brain and spinal cord. White matter is the more heavily myelinated sections, and it is located deep in the central regions of the brain and toward the outer sections of the spinal cord.

Symptoms: 

• Loss of vision in one or both eyes due to inflammation of the optic nerve 
• Weakness that may be severe 
• Difficulty coordinating intended (voluntary) movement such as walking 
• Rapid onset of fever 
• Some degree of impairment of consciousness, perhaps as severe as coma 

Treatment: 
Treatment is targeted at suppressing the immune system and inflammation in the brain using anti-inflammatory drugs such as corticosteroids. Some individuals may need plasma exchange (plasmapheresis) or immunoglobulin therapy. Most people with ADEM being to recover within days after treatment, and many will recover completely within six months. In rare instances, ADEM can be fatal.