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Acute Disseminated Encephalomyelitis

Also known as:

Background

Acute disseminated encephalomyelitis (ADEM) is an inflammatory disorder affecting the brain (enceph-) and/or spinal cord (myelitis). It is a monophasic condition meaning it tends to only occur once. It usually occurs after an infection, even a minor one, and occasionally after immunisation. In the case of ADEM, unlike in viral encephalitis, no organisms or viral particles are found in the brain or spinal fluid.

Credits

Medical text written by October 2010 by Leena D Mewasingh. Last updated May 2016 by Leena D Mewasingh, Consultant Paediatric Neurologist and Honorary Senior Clinical Lecturer, St Mary's Hospital, Imperial College Healthcare NHS Trust, London, UK.

Although great care has been taken in the compilation and preparation of all entries to ensure accuracy, we cannot accept responsibility for any errors or omissions. Any medical information is provided is for education/information purposes and is not designed to replace medical advice by a qualified medical professional.

What are the symptoms?

There is often an infection that occurs before the diagnosis of ADEM, or even an immunisation, the interval varying between several days up to one month, the average being one to two weeks. In a minority of cases there is no clear preceding illness. At the beginning, symptoms are often non-specific, such as fever, headache, stiff neck, a loss of appetite and vomiting. This is followed by a decreased conscious level (eg the child may seem confused, lethargic or drowsy and not respond in their normal way). For a diagnosis of ADEM to be made, a child's level of consciousness must be affected and this is referred to as 'acute encephalopathy'. At times the child can even slip into coma.

Other symptoms include:

  • hemiparesis (weakness down one side of the body)
  • ataxia (unsteadiness)
  • cranial nerve palsies (paralysis of the nerves that emerge directly from the brain)
  • visual impairment or visual loss due to inflammation of the optic nerve (eg optic neuritis) often involving both eyes
  • seizures (these are more common in the younger child - five years old or younger).

What are the causes?

Why ADEM occurs remains poorly understood. As it is generally preceded by an infection or rarely, an immunisation, this suggests an immune/inflammatory process is important. Whilst many different bacteria, viruses and other infections have been related to ADEM, this condition does not appear to be caused by any one specific infectious agent.

How is it diagnosed?

The diagnosis is made based upon clinical history, with magnetic resonance imaging (MRI) scans that often show changes as described by the IPMSSG criteria. Other tests include a lumbar puncture, where a small amount of fluid called cerebrospinal fluid (CSF) is removed from the spine with a needle. This fluid is analysed and in ADEM it is often abnormal with an increase in white cells and protein. An electroencephalogram (EEG), which records the surface brain activity, is abnormal in most ADEM cases.

A special committee, the International Pediatric Multiple Sclerosis Study Group (IPMSSG) was brought together to define ADEM, given variations in its definition until then, and also because there are no diagnostic tests for this condition. The group established criteria for the definition of ADEM in 2007, which were recently reviewed and amended in 2013 and are now largely accepted as a definition to aid a working diagnosis of ADEM.

How is it treated?

High-dose steroid treatment given early during the illness is the main form of treatment used and it is given intravenously (through a vein) for a few days. The high-dose steroids are then changed to oral steroids which are gradually reduced over several weeks. This process of adjusting the body's immune response is called immunomodulation. There is often a dramatic improvement after this type of treatment. Most children recover significantly, if not completely, and overall the prognosis is very good. Other treatments used are: intravenous immunoglobulin (IVIG) and throughout the illness the child has to be monitored closely and at times this can mean intensive care management with the child on a ventilator.

Some research studies of children that had ADEM have reported a small group of patients who then went on to develop multiple sclerosis. There is a lot of research that is ongoing in this area.

Another study that is currently ongoing in UK is looking at the role of IVIG in children with encephalitis known as the IgNITE study.

Inheritance patterns and prenatal diagnosis

Is there support?

Information and support in the UK for acute disseminated encephalomyelitis is provided by the Encephalitis Society (see entry Encephalitis).

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