A demyelinating disease is any of a group of diseases that damage the myelin that surrounds neurons. As such, they usually share a common symptom of losses of sensation, ability to move, cognition and other functions affected by the relevant nerves. However, although those symptoms are more common, they can account for a very wide constellation of symptoms. They can be caused by a number of different factors including genetics, infections and autoimmune disorders. However, it appears that no matter what the underlying etiology of the disease, the immune system is at least partially to blame for the damage to the sheath as different types of antibodies are usually found at the site of the damage.
Deymyelinating diseases are usually diagnosed after a differential diagnosis rules out all other possibilities for the symptoms. They can then be confirmed by a variety of tests including MRI, evoked potential and cerebro-spinal fluid analysis, At that point, the diagnosis is narrowed to a specific condition.