Neuromyelitis optica (NMO)

Overview

Also known as Devic’s disease, neuromyelitis optica (NMO) is an uncommon disease syndrome of the central nervous system (CNS) that affects the optic nerves and spinal cord. Individuals with NMO develop optic neuritis, which causes pain in the eye and vision loss, and transverse myelitis, which causes weakness, numbness, and sometimes paralysis of the arms and legs, along with sensory disturbances and loss of bladder and bowel control. NMO leads to loss of myelin, which is a fatty substance that surrounds nerve fibers and helps nerve signals move from cell to cell. Put briefly NMO is a central nervous system disorder, which results in primarily swelling and inflammation of the eye nerves (optic neuritis) and the spinal cord (myelitis).

The condition occurs when your body’s immune system reacts against its own cells in the central nervous system, mainly in the optic nerves and spinal cord, but sometimes in the brain. The cause often is unknown, although it may sometimes appear after an infection, or it may be associated with another autoimmune condition.Historically, NMO was diagnosed in patients who experienced a rapid onset of blindness in one or both eyes, followed within days or weeks by varying degrees of paralysis in the arms and legs. In most cases, however, the interval between optic neuritis and transverse myelitis is significantly longer, sometimes as long as several years.

After the initial attack, NMO follows an unpredictable course. Most individuals with the syndrome experience clusters of attacks months or years apart, followed by partial recovery during periods of remission. This relapsing form of NMO primarily affects women. The female to male ratio is greater than 4:1. Another form of NMO, in which an individual only has a single, severe attack extending over a month or two, is most likely a distinct disease that affects men and women with equal frequency. The onset of NMO varies from childhood to adulthood, with two peaks, one in childhood and the other in adults in their 40s.

The recent discovery of an antibody in the blood of individuals with NMO gives doctors a reliable biomarker to distinguish NMO from multiple sclerosis. The antibody, known as NMO-IgG, seems to be present in about 70 percent of those with NMO and is not found in people with MS or other similar conditions.

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