Current research indicates that neuromyelitis optica (NMO) patients have a 91% to 98% five-year survival rate. Life expectancy has improved from the earlier 68% to 75% five-year survival rate, after the discovery of antibodies known as anti-aquaporin-4 (AQP-4) immunoglobulin G (IgG) present in 70% of NMO patients, and the development of treatments targeting these antibodies.
- Life expectancy with NMO also depends on various factors such as the patient’s age, type of NMO, and severity and frequency of relapses.
- Up to 30% of patients, however, have residual visual and neuromuscular disabilities after the initial attack, which can worsen with relapses.
- Monophasic NMO, a type of NMO that doesn’t relapse has a better prognosis.
What is NMO?
Neuromyelitis optica is a rare inflammatory autoimmune disorder that primarily affects the optic nerve and the spinal cord, and sometimes the brain. NMO is also known as Devic’s disease or neuromyelitis optica spectrum disorder (NMOSD).
NMO is a condition in which the immune system specifically attacks myelin, a fatty sheath that insulates nerve fibers (axons) and enables efficient transmission of nerve signals. The autoimmune attack results in inflammation and damage to the nerve fibers, disrupting nerve cell communication.
NMO can occur at any age from infancy to old age and is far more common in women than men. NMO also appears to be more prevalent in people of Asian and African origin than in Caucasians.
NMO may be of two types:
- Monophasic: Monophasic form is a single attack of NMO lasting for a period of a few days or weeks which does not recur. This form is uncommon and affects both sexes equally.
- Relapsing: The relapsing form of NMO is characterized by periodic flare-ups with intervals of remission which can last anything from weeks to even decades. This form is more common than the monophasic form and is up to 7 times more prevalent in women than in men.
What are the symptoms of NMO?
- Optic neuritis: Optic neuritis is the inflammation of the optic nerve, which can affect one or both eyes. Symptoms include:
- Transverse myelitis: Transverse myelitis is the inflammation of the spinal cord. Symptoms may include any of the following:
What causes NMO?
NMO is the result of an abnormal attack on healthy nerve cells by the immune system. Antibodies (IgG) in the immune system, for unknown reasons, consider certain proteins in the central nervous system a threat and attack them. NMO is caused by two types of antibodies that attack different proteins in the optic nerve and spinal cord:
- Anti-AQP4: In the relapsing type of NMO, anti-AQP4 antibodies (NMO-IgG) form and attack aquaporin-4 protein, damaging the myelin and nerve fibers. Aquaporin is a protein in the cell membrane, which regulates the flow of water molecules in and out of cells. Aquaporin-4 is the most common aquaporin in the optic nerve, spinal cord, and brain.
- Anti-MOG: Anti-myelin oligodendrocyte glycoprotein (MOG) antibodies attack MOG, a component of myelin. Antibodies to MOG are found in monophasic NMO, a less common type of NMO.
It is not clear what exactly triggers the autoimmune attack in NMO and it doesn’t appear to be an inherited condition. Only about 3% of NMO patients report having a relative with the condition, but approximately 50% of patients have a personal or family history of other autoimmune disorders.
What is the best treatment for NMO?
Treatment for NMO is based on several tests that the patient undergoes, which include:
- Physical examination
- Blood tests to detect the presence of NMO antibodies
- Spinal taps to test the cerebrospinal fluid
- Imaging tests such optical coherence tomography (OCT) scans to look for damage in the optic nerve, and CT and MRI scans of the spine
- Tests to rule out closely related autoimmune disorders such as MS
The standard treatment for NMO is threefold:
Management of an acute attack
Acute attacks of NMO are typically treated with the following:
- Intravenous corticosteroids such as methylprednisolone reduce inflammation.
- Plasma exchange (plasmapheresis), a procedure to lower the NMO-IgG in the blood. The patient is connected through an intravenous line to a device that separates the plasma from the blood and replaces it with substitute plasma, which is then reinfused along with the other blood components.
Prevention of future attacks
More than 90% of NMO patients have recurring attacks which are generally severe, so prevention of relapse is an integral part of NMO treatment. Preventive medications are primarily immunosuppressants that lower immune activity in NMO patients.
In 2019 and 2020, the FDA approved three medications to treat anti-APQ4 positive NMO. These medications are lab-engineered human antibodies that specifically target the anti-APQ4 antibodies in NMO, which include:
Immunosuppressants used off-label to treat NMO include:
Management of symptoms
Is NMO curable?
Currently, there is no cure for NMO, but treatments can reduce the frequency and severity of attacks and alleviate symptoms. The discovery of anti-APQ4 and anti-MOG bodies have improved the prospects for early diagnosis and effective management of the disease.
Is NMO worse than MS?
- Symptoms after an NMO attack are generally more severe than those after multiple sclerosis (MS) attack, though, unlike MS, NMO rarely has a progressive stage between episodes.
- MS episodes are usually mild and patients may or may not accumulate disabilities, but NMO episodes can have debilitating and irreversible effects, and can also lower life expectancy.
- NMO was previously thought to be a variant of MS because many symptoms are common between the two diseases.
- The discovery of anti-AQP4 and anti-MOG antibodies led to the distinction between the two diseases. The two diseases have some distinct features that can be detected with tests.
- Both NMO and MS are autoimmune conditions, but NMO primarily affects the optic nerve and spinal cord while MS can affect any white matter in the central nervous system.
- Anti-AQP4 antibodies are present in 70% of NMO patients, while these antibodies are absent in MS.
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