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. The syndrome can also damage nerve fibers and leave areas of broken-down tissue. In the disease process of NMO, for reasons that aren't yet clear, immune system cells and antibodies attack and destroy myelin cells in the optic nerves and the spinal cord.

There is no cure for NMO, but there are therapies to treat an attack while it is happening, to reduce symptoms, and to prevent relapses. Doctors usually treat an initial attack of NMO with a combination of a corticosteroid drug (methylprednisolone) to stop the attack, and an immunosuppressive drug (azathioprine) for prevention of subsequent attacks. If frequent relapses occur, some individuals may need to continue a low dose of steroids for longer periods. Plasma exchange (plasmapheresis) is a technique that separates antibodies out of the blood stream and is used with people who are unresponsive to corticosteroid therapy. Pain, stiffness, muscle spasms, and bladder and bowel control problems can be managed with the appropriate medications and therapies. Individuals with major disability will require the combined efforts of occupational therapists, physiotherapists, and social services professionals to address their complex rehabilitation needs.

Most individuals with NMO have an unpredictable, relapsing course of disease with attacks occurring months or years apart. Disability is cumulative, the result of each attack damaging new areas of myelin. Some individuals are severely affected by NMO and can lose vision in both eyes and the use of their arms and legs. Most individuals experience a moderate degree of permanent limb weakness from myelitis. Muscle weakness can cause breathing difficulties and may require the use of artificial ventilation. The death of an individual with NMO is most often caused by respiratory complications from myelitis attacks.

Prepared by the National Institutes of Health