Neuromyelitis optica

Neuromyelitis optica, also known as NMO, is a central nervous system disorder that causes inflammation in nerves of the eye and the spinal cord.

NMO also is called neuromyelitis optica spectrum disorder (NMOSD) and Devic disease. It occurs when the immune system reacts against the body's own cells. This happens mainly in the spinal cord and in the optic nerves that connect the retina of the eye with the brain. But it sometimes happens in the brain.

The condition may appear after an infection, or it can be linked with another autoimmune condition. Altered antibodies bind to proteins in the central nervous system and cause damage.

Neuromyelitis optica is often misdiagnosed as multiple sclerosis, also known as MS, or is seen as a type of MS. But NMO is a different condition.

Neuromyelitis optica can cause blindness, weakness in the legs or arms, and painful spasms. It also can cause loss of sensation, vomiting and hiccups, and bladder or bowel symptoms.

Symptoms can get better and then worse again, known as a relapse. Treatment to prevent relapses is important to help prevent disability. NMO can cause permanent vision loss and trouble walking.

Symptoms of neuromyelitis optica are related to the inflammation that occurs in the nerves of the eye and spinal cord.

Vision changes caused by NMO are called optic neuritis. These may include:

• Blurred vision or loss of vision in one or both eyes.
• Not being able to see color.
• Eye pain.

Symptoms related to the spinal cord are called transverse myelitis. These may include:

• Stiffness, weakness or numbness in the legs and sometimes in the arms.
• Loss of feeling in the arms or legs.
• Not being able to empty the bladder or trouble managing bowel or bladder function.
• A tingling feeling or shooting pain in the neck, back or stomach.

Other symptoms of NMO may include:

• Hiccups.
• Nausea and vomiting.

Children can have confusion, seizures or coma. However, these symptoms in children are more common in a related condition known as myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).

Symptoms may get better and then worse again. When they get worse, it's known as a relapse. Relapses can happen after weeks, months or years. Over time, relapses can lead to total blindness or loss of feeling, known as paralysis.

Experts don't know exactly what causes neuromyelitis optica. In people who have the disease, the immune system attacks healthy tissues in the central nervous system. The central nervous system includes the spinal cord, brain and optic nerves that connect the retina of the eye with the brain. The attack occurs because altered antibodies bind to proteins in the central nervous system and cause damage.

This immune system reaction causes swelling, known as inflammation, and leads to the damage of nerve cells.

Neuromyelitis optica is rare. Some factors that may raise the risk of getting NMO include:

• Sex assigned at birth. Women have NMO more often than do men.
• Age. Most often, NMO affects adults. The average age of diagnosis is 40. However, children and older adults also can have neuromyelitis optica.
• Race or ethnicity. People of Hispanic, Asian, or African or Afro-Caribbean descent have NMO at higher rates than do people who are white.

Some research suggests that not having enough vitamin D in the body, smoking and having few infections early in life also may raise the risk of neuromyelitis optica.

Diagnosing neuromyelitis optica involves a physical exam and tests. Part of the diagnosis process is to rule out other nervous system conditions that have similar symptoms. Healthcare professionals also look for symptoms and test results linked to NMO. Criteria to diagnose neuromyelitis optica spectrum disorder (NMOSD) were proposed in 2015 by the International Panel for NMO Diagnosis.

A healthcare professional reviews your medical history and symptoms and does a physical exam. Other tests include:

• Neurological exam. A neurologist examines movement, muscle strength, coordination, sensation, memory, thinking, vision and speech. An eye doctor also 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 results may show lesions or damaged areas in the brain, optic nerves or spinal cord.

• Blood tests. A healthcare professional might test the blood for the autoantibody that binds to proteins and causes NMO. The autoantibody is called aquaporin-4-immunoglobulin G, also known as AQP4-IgG. Testing for this autoantibody can help healthcare professionals distinguish between NMO and MS and make an early diagnosis of NMO.

  Other biomarkers such as serum glial fibrillary acidic protein, also called GFAP, and serum neurofilament light chain help detect relapses. A myelin oligodendrocyte glycoprotein immunoglobulin G antibody test, also called an MOG-IgG antibody test, also might be used to look for another inflammatory disorder that mimics NMO.

• Lumbar puncture, also known as a spinal tap. During this test, a healthcare professional 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 a very high level of white blood cells during NMO episodes. This is greater than the level usually seen in MS, although this symptom doesn't always happen.

• Stimuli response test. To learn how well the brain responds to stimuli such as sounds, sights or touch, you may have a test called an evoked potentials test or evoked response test.

  Wires called electrodes are attached to the scalp and, sometimes, the earlobes, neck, arms, legs 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 looks at the retinal nerve fiber layer and its thickness. Patients with inflamed optic nerves from NMO have more-extensive vision loss and retinal nerve thinning than do people with MS.

Neuromyelitis optica can't be cured. But treatment can sometimes lead to a long-term period with no symptoms, known as remission. NMO treatment involves therapies to reverse recent symptoms and prevent future attacks.

• Reversing recent symptoms. In the early stage of an NMO attack, a healthcare professional 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.

  Healthcare professionals also can help manage other possible symptoms, such as pain or muscle problems.

• Preventing future attacks. Your healthcare professional 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. These medicines include eculizumab (Soliris), satralizumab (Enspryng), inebilizumab (Uplizna), ravulizumab (Ultomiris) and rituximab (Rituxan). Many of these have been approved by the U.S. Food and Drug Administration (FDA) for prevention of relapses in adults.

  Your healthcare professional also might recommend taking a medicine that suppresses the immune system. This might include azathioprine (Imuran, Azasan), mycophenolate (Cellcept, Myhibbin), methotrexate (Trexall, Xatmep, others), cyclophosphamide or tocilizumab (Actemra).

  Intravenous immunoglobulins, also known as antibodies, may decrease the relapse rate of NMO.