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Neuromyelitis optica spectrum disorder (NMOSD) is a chronic immune mediated condition, in which the body’s immune system mistakenly attacks the central nervous system. People with NMOSD often develop inflammation of the nerves of the eyes or optic nerves (optic neuritis), of the spinal cord (transverse myelitis), or sometimes of the brain.
Possible symptoms of NMOSD include:
NMOSD has an unpredictable course and many people with NMOSD develop attacks (relapses) which may occur months or years apart. Disability can be cumulative with repeated attacks, leading to worsening disability over time e.g. difficulty with walking and long-lasting visual loss.Previously, NMOSD was thought to be a subtype of multiple sclerosis (MS) as both the conditions have similar symptoms. We now know that NMOSD is a separate condition. Attacks in NMOSD are often more severe and the effects might be permanent after each attack.
In most patients, this autoimmune condition is caused by an autoantibody called aquaporin-4-immunoglobulin G (AQP4-IgG antibody). NMOSD may develop in association with other autoimmune disorders. NMOSD usually develop in adulthood, between the ages of 30 and 65. It can also rarely affect children and the elderly. Women are more commonly affected than men.While NMOSD can affect people of all races and ethnic backgrounds, those of African and Asian descents may develop the disorder at a higher rate.
NMOSD can be diagnosed by a combination of detailed medical history, clinical examination and tests. Some of these tests include:
- Detecting AQP4-IgG antibody in the blood helps to differentiate between NMOSD and MS as well as other similar immune-mediated neurological conditions
- Imaging of the brain, optic nerves and spinal cord to detect areas of inflammation or damage
There is currently no cure for NMOSD but there are treatment options for acute attacks, relapse prevention, and symptom relief.
Early treatment after an attack is essential to minimize the risk of permanent damage. The most common drugs are corticosteroids. High dose intravenous (IV; given through the vein) methylprednisolone is usually given over 3 to 5 days, followed by a slow tapering course of oral prednisolone.Plasma exchange (plasmapheresis) may be recommended as first or second treatment, especially for patients who did not respond substantially to corticosteroids. Plasma exchange involves removal of harmful antibodies and other immune factors in the blood stream by mechanically separating the blood cells from the fluid (plasma) via a specialized machine.
There are drugs available for the prevention of relapses. Your neurologist may recommend azathioprine, mycophenolate mofetil, rituximab, or tocilizumab. While these drugs have been demonstrated in small clinical trials, observation studies, and clinical practice to be effective in preventing NMOSD relapses and are commonly used, they are currently not approved by the U.S. Food and Drug Administration (FDA).Drugs which have been shown to be effective in reducing relapses in adults with NMOSD who have AQP4-IgG antibodies and are approved by the U.S. FDA include eculizumab, inebilizumab, and satralizumab. However, these monoclonal antibodies may not be readily available in every country.
After a relapse, people with NMOSD may continue to have symptoms such as weakness, walking difficulty, visual impairment, bowel and bladder issues, and pain. Medications can be prescribed to address these symptoms.Additionally, physiotherapy and occupational therapies are often required to optimize functional status e.g. to improve mobility.