Acute disseminated encephalomyelitis

December 31, 2014

Synonyms

Overview

Acute disseminated encephalomyelitis is a neurological condition characterized by a brief but intense attack of inflammation in the brain and spinal cord that damages myelin – the protective covering of nerve fibers. It often follows viral infection, or less often, vaccination for measles, mumps, or rubella. Treatment for ADEM is targeted at suppressing inflammation in the brain using anti-inflammatory drugs. Plasmapheresis or intravenous immunoglobulin therapy may also be used. Additional treatment is symptomatic and supportive.

Symptoms

The symptoms of acute disseminated encephalomyelitis come on quickly, beginning with encephalitis-like symptoms such as fever, fatigue, headache, nausea and vomiting, and in severe cases, seizures and coma. It may also damage white matter (brain tissue that takes its name from the white color of myelin), leading to neurological symptoms such as visual loss (due to inflammation of the optic nerve) in one or both eyes, weakness even to the point of paralysis, and difficulty coordinating voluntary muscle movements (such as those used in walking). ADEM is sometimes misdiagnosed as a severe first attack of multiple sclerosis (MS), since some of the symptoms of the two disorders, particularly those caused by white matter injury, may be similar. However, ADEM usually has symptoms of encephalitis (such as fever or coma), as well as symptoms of myelin damage (visual loss, paralysis), as opposed to MS, which doesn't have encephalitis symptoms. In addition, ADEM usually consists of a single episode or attack, while MS features many attacks over the course of time.

Causes

Acute disseminated encephalomyelitis may develop in the wake of a wide variety of infectious illnesses or immunizations. The agents most commonly identified include Epstein-Barr virus, cytomegalovirus, herpes simplex virus (HSV), and mycoplasma. ADEM is somewhat more common in the colder months of the year, during which these various viral illnesses are more prevalent. Prior to widespread immunization programs, measles was the most common associated illness. Now, most cases occur in the wake of respiratory or gastrointestinal illnesses that are presumed to be caused by viral infections; specific viral agents are seldom identified.

Clear links between the Pasteur rabies vaccine and ADEM have been established. Immunizations less frequently associated with ADEM include pertussis, measles, Japanese B virus, tetanus, and influenza.

Prognosis

Corticosteroid therapy can shorten the duration of neurological symptoms and halt further progression of the disease in the short term, but the long term prognosis for individuals with ADEM varies. For most, recovery begins within days, and half will recover completely. Others may have mild to moderate lifelong impairment. Severe cases of ADEM can be fatal. Some individuals initially diagnosed as having ADEM will later be reclassified as MS, but there is currently no method to determine whom those individuals will be.

Treatment

Treatment for acute disseminated encephalomyelitis is targeted at suppressing inflammation in the brain using anti-inflammatory drugs. Most individuals respond to intravenous corticosteroids such as methylprednisolone. When corticosteroids fail to work, plasmapheresis or intravenous immunoglobulin therapy has been shown to produce improvement. Additional treatment is symptomatic and supportive.