Neuromyelitis optica (NMO) is a central nervous system disorder that primarily affects the eye nerves (optic neuritis) and the spinal cord (myelitis). NMO is also known as neuromyelitis optica spectrum disorder or Devic's disease. It 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 of neuromyelitis optica is usually unknown, although it may sometimes appear after an infection, or it may be associated with another autoimmune condition. Neuromyelitis optica is often misdiagnosed as multiple sclerosis (MS) or perceived as a type of MS, but NMO is a distinct condition.
Neuromyelitis optica may cause blindness in one or both eyes, weakness or paralysis in the legs or arms, painful spasms, loss of sensation, uncontrollable vomiting and hiccups, and bladder or bowel dysfunction from spinal cord damage. Children may experience confusion, seizures or coma with NMO. Neuromyelitis optica flare-ups may be reversible, but can be severe enough to cause permanent visual loss and problems with walking.
Your doctor will perform a thorough evaluation to rule out other nervous system (neurological) conditions that have signs and symptoms similar to neuromyelitis optica. Distinguishing NMO from multiple sclerosis and other conditions ensures that you receive the most appropriate treatment.
To diagnose your condition, your doctor will review your medical history and symptoms and perform a physical examination. Your doctor may also perform:
- Neurological examination. A neurologist will examine your movement, muscle strength, coordination, sensation, memory and thinking (cognitive) functions, and vision and speech. An eye doctor (ophthalmologist) also may be involved in your examination.
- Magnetic resonance imaging (MRI). An MRI uses powerful magnets and radio waves to create a detailed view of your brain, optic nerves and spinal cord. Your doctor may be able to detect lesions or damaged areas in your brain, optic nerves or spinal cord.
- Blood tests. Your doctor might test your blood for the autoantibody NMO-IgG (also known as the aquaporin-4 autoantibody — AQP4), which helps doctors distinguish NMO from MS and other neurological conditions. This test helps doctors make an early diagnosis of NMO. A myelin oligodendrocyte glycoprotein (MOG-IgG) antibody test may also be requested to look for another inflammatory disorder that mimics NMO.
Lumbar puncture (spinal tap). During this test, your doctor will insert a needle into your lower back to remove a small amount of spinal fluid. Doctors test the levels of immune cells, proteins and antibodies in the fluid. This test may help your doctor differentiate NMO from MS.
In NMO, the spinal fluid may show markedly elevated white blood cells during NMO episodes, greater than normally seen in MS, although this doesn't always happen.
Stimuli response test. To learn how well your brain responds to stimuli such as sounds, sights or touch, you'll undergo a test called evoked potentials (they may also be called evoked response tests).
During these tests, doctors attach small wires (electrodes) to your scalp and, in some cases, your earlobes, neck, arm, leg and back. Equipment attached to the electrodes records your brain's responses to stimuli. These tests help your doctor to find lesions or damaged areas in the nerves, spinal cord, optic nerve, brain or brainstem.
Neuromyelitis optica can't be cured, though long-term remission may be 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, your doctor may give you a corticosteroid medication, methylprednisolone (Solu-Medrol), through a vein in your arm (intravenously). You'll be given the medication for about five days, and then the medication will be tapered off slowly over several days.
Plasma exchange is frequently recommended as the first or second treatment, usually in addition to steroid therapy. In this procedure, some blood is removed from your body, and blood cells are mechanically separated from fluid (plasma). Doctors mix your blood cells with a replacement solution and return the blood into your body.
Doctors can also help manage other symptoms you may experience, such as pain or muscle problems.
Preventing future attacks. Doctors may recommend that you take a lower dose of corticosteroids for an extensive period of time to prevent future NMO attacks and relapses.
Your doctor may also recommend taking a medication that suppresses your immune system, in addition to corticosteroids, to prevent future NMO attacks. Immunosuppressive medications that may be prescribed include azathioprine (Imuran, Azasan), mycophenolate mofetil (Cellcept) or rituximab (Rituxan).