Neuromyelitis optica (NMO) is a central nervous system disorder that causes inflammation in nerves of the eye and the spinal cord.
NMO is also called neuromyelitis optica spectrum disorder (NMOSD) and Devic disease. It occurs when the body's immune system reacts against its own cells. This happens mainly in the optic nerves that connect the retina of the eye with the brain and in the spinal cord. But it sometimes occurs in the brain.
The disorder may appear after an infection. Or it can be associated with another autoimmune condition. Irregular antibodies bind to proteins in the central nervous system and cause damage.
Neuromyelitis optica is often misdiagnosed as multiple sclerosis (MS) or seen as a type of MS. But NMO is a different condition.
Neuromyelitis optica can cause blindness in one or both eyes, weakness or paralysis in the legs or arms, and painful spasms. It also can cause loss of sensation, uncontrollable vomiting and hiccups, and bladder or bowel problems from spinal cord damage. Children can have confusion, seizures or comas.
Relapses are common. Preventing recurrent attacks is a key to averting disability. Neuromyelitis optica flare-ups might be reversible, but they can be severe enough to cause permanent visual loss and problems with walking.
Your health care provider performs a thorough exam to rule out other nervous system conditions that have signs and symptoms similar to neuromyelitis optica.
In 2015, the International Panel for NMO Diagnosis proposed criteria to diagnose this illness.
To detect the condition, a health care provider generally reviews the medical history and symptoms and performs a physical exam. Other tests include:
- Neurological exam. A neurologist examines the movements, muscle strength, coordination, sensation, memory, thinking, vision and speech. An eye doctor might be involved in the exam.
- MRI. This imaging test uses a magnetic field and radio waves to create a detailed view of the brain, optic nerves and spinal cord. The health care provider might be able to detect lesions or damaged areas in the brain, optic nerves or spinal cord.
Blood tests. A health care provider might test the blood for the aquaporin-4-immunoglobulin G, also called AQP4-IgG antibody. This test shows a difference between NMO and MS. This test helps in making an early diagnosis of NMO.
Other biomarkers such as serum glial fibrillary acidic protein (GFAP) and serum neurofilament light chain help detect relapses. A myelin oligodendrocyte glycoprotein immunoglobulin G (MOG-IgG) antibody test also might be used to look for another inflammatory disorder that mimics NMO.
Lumbar puncture (spinal tap). During this test, the neurologist inserts a needle into the lower back to remove a small amount of spinal fluid. This test determines the levels of immune cells, proteins and antibodies in the fluid. This test might distinguish NMO from MS.
The spinal fluid might show very high white blood cells during NMO episodes. This is greater than usually seen in MS, although this doesn't always happen.
Stimuli response test. To learn how well the brain responds to stimuli such as sounds, sights or touch, a test called evoked potentials test or evoked response test is done.
Wires called electrodes are attached to the scalp and, in some cases, the earlobes, neck, arm, leg and back. Equipment attached to the electrodes records the brain's responses to stimuli. These tests help find lesions or damaged areas in the nerves, spinal cord, optic nerve, brain or brainstem.
- Optical coherence tomography. This test evaluates the retinal nerve and its thickness. Patients with an inflamed optic nerve from NMO have more-extensive vision loss and retinal nerve thinning than people with MS.
NMO can't be cured, though long-term remission is sometimes possible with the right management. NMO treatment involves therapies to reverse recent symptoms and prevent future attacks.
Reversing recent symptoms. In the early stage of an NMO attack, a health care provider might give a corticosteroid medicine such as methylprednisolone (Solu-Medrol). It's given through a vein in the arm. The medicine is taken for about five days and then it's usually tapered off slowly over several days.
Plasma exchange is often recommended as the first or second treatment, usually in addition to steroid therapy. In this procedure, some blood is removed from the body, and blood cells are mechanically separated from fluid called plasma. The blood cells are mixed with a replacement solution and the blood is returned to the body. This process can remove harmful substances and cleanse the blood.
Health care providers also can help manage other possible symptoms, such as pain or muscle problems.
- Preventing future attacks. Your health care provider might recommend that you take a lower dose of corticosteroids over time to prevent future NMO attacks and relapses.
Reducing relapses. Monoclonal antibodies have been shown in clinical trials to be effective in reducing the risk of NMO relapses. Eculizumab (Soliris, Elizaria), satralizumab (Enspryng) and inebilizumab (Uplizna) have been approved by the U.S. Food and Drug Administration (FDA) for relapses in adults.
Rituximab (Rituxan) also has been shown in clinical trials to be effective in reducing NMO relapses. It's commonly used for NMO, although it's not currently FDA approved.
Your health care provider also might recommend taking a medicine that suppresses the immune system. They might include azathioprine (Imuran, Azasan), mycophenolate (Cellcept), methotrexate (Trexall), cyclophosphamide (Cytoxan) or tocilizumab (Actemra.)
Intravenous immunoglobulins, also known as antibodies, may decrease the relapse rate of NMO.