In the autoimmune disorder neuromyelitis optica (NMO), the immune system attacks the optic nerves and spinal cord. This can cause symptoms such as loss of vision and changes in sensation. Early and ongoing treatment helps reduce the chances of an attack that may cause more severe symptoms.
In NMO, a rare autoimmune disorder, a person’s immune system attacks the optic nerves, the spinal cord, and sometimes the brain. This condition is also known as Devic’s disease or neuromyelitis optica spectrum disorder (NMOSD).
Depending on where the damage occurs, it can cause a variety of symptoms ranging from pain in the eyes and weakness in the arms and legs to paralysis.
Prompt and ongoing treatment can greatly reduce the likelihood of experiencing future attacks and more severe NMO symptoms.
This article discusses the symptoms of NMO, the causes, and more.
In NMO, the body’s immune system attacks the optic nerves and the spinal cord. In some cases, the immune system may also attack the brain. This causes swelling, inflammation, and damage in the optic nerves and spinal cord.
People with this rare autoimmune disorder usually experience periods where symptoms get worse, known as relapses or attacks. During attacks, the person’s immune system may cause new damage to the optic nerves and spinal cord.
Attacks may occur weeks or even years apart. New damage can occur each time a person experiences an NMO relapse, which can lead to more symptoms and disabilities over time.
Women account for more than 80% of NMO cases, according to the National MS Society.
The condition can appear at any age, but it most commonly develops between ages 40 and 50. While NMO occurs in people of all races all over the world, it tends to be more common in people of African, Asian, or Native American descent, per the National MS Society.
Symptoms of NMO vary based on where in a person’s body the damage occurs.
NMO can cause optic neuritis and myelitis. Optic neuritis refers to swelling of the optic nerve and myelitis refers to inflammation of the spinal cord.
Optic neuritis may happen in one or both eyes and cause the following symptoms:
- pain at the back of the eye socket and when the eye moves
- blurry vision
- colors looking faded or dull
- dim vision, as if someone has turned the lights down
These symptoms can get worse when a person feels hot or tired. Exercise may aggravate symptoms. The symptoms may worsen without treatment.
Myelitis most commonly causes changes in or loss of sensation. A person may also experience:
- muscle weakness
- numbness and tingling
- shooting pain or tingling in the neck or back
- increased tone or stiffness in the extremities (spasticity)
- difficulty controlling the bowels or bladder
- trouble completely emptying the bladder
- stiffness in the arms and legs
- uncontrollable nausea, vomiting, or hiccups
- confusion, seizures, or coma (usually in children)
NMO usually appears as a relapse-remitting disease. This means that people experience periods of worsening symptoms.
People generally experience severe episodes. Without diagnosis and treatment, these can cause accumulating damage, disability, and potentially death due to complications.
For the best outcomes, a person must get an early NMO diagnosis. It will help them get proper treatment and lessen the damage caused by NMO relapses.
A healthcare professional will generally start by reviewing a person’s medical history and doing a physical exam. They may refer the person to a neurologist for a neurological exam.
During the neurological exam, a doctor will check the person’s:
- muscle strength
Depending on the outcomes of the neurological exam, a doctor may order several tests including:
- MRI scan to see the brain, optic nerves, and spinal cord
- spinal tap to examine the fluid around the spine
- eye exams
- blood tests for NMO-IgG and MOG-IgG
Doctors will first rule out other possible conditions, then make a diagnosis based on whether a person tests AQP4-positive.
If a person has AQP4 antibodies, they must meet at least one additional diagnostic criteria for an NMO diagnosis.
If a person does not have AQP4 antibodies, they must meet at least two additional diagnostic criteria to get an NMO diagnosis, including at least one of the first three criteria listed below. Diagnosis includes several other requirements, such as an MRI that shows specific types of brain lesions.
Diagnostic criteria for NMSOD include:
- optic neuritis
- acute myelitis
- unexplained hiccups or nausea and vomiting (area postrea syndrome)
- symptomatic narcolepsy with NMOSD-typical lesions on the brain
- acute brainstem syndrome
- symptoms of acute cerebral syndrome along with NMOSD-typical lesions on the brain
Researchers do not know the exact cause of NMO. While more than 95% of people with NMO have no family history of the disease, 50% have a personal or family history of other autoimmune disorders, according to the National Organization for Rare Disorders.
In NMO, the immune system attacks proteins on the surface of supportive cells in the brain, spine, and optic nerves. This damages the cells and leads to the loss of protective fatty tissues (called myelin) that surround the nerves, in a process called demyelination.
For an estimated 80% of people with NMO, the body develops AQP4 antibodies (NMO-IgG or anti-AQP4 antibody) that attack the AQP4 water channel. This channel allows water to pass through cell membranes.
Up to 1 in 3 people who do not test positive for AQP4 antibodies have another antibody that attacks myelin, called myelin oligodendrocyte glycoprotein (MOG).
If demyelination occurs around the optic nerve, it can lead to eye pain and a loss of vision. When it occurs around the spinal cord, it can lead to the changes in sensation and perception associated with myelitis.
Early and ongoing treatment for NMO can help manage the condition. It also greatly reduces the likelihood of a relapse. This, in turn, reduces the chances of experiencing more severe symptoms and disability.
- Corticosteroids: These help manage an ongoing attack.
- Plasma exchange: Healthcare professionals typically recommend this therapy during an acute attack and usually only if corticosteroids do not get symptoms under control.
- Immunotherapy: The Food and Drug Administration (FDA) has approved three drugs as an ongoing treatment for NMO in AQP4 antibody-positive people:
- eculizumab (Soliris)
- inebilizumab (Uplizna)
- satralizumab-mwge (Enspryng)
Healthcare professionals may also use other immunotherapies, including mycophenolate mofetil (CellCept) and rituximab (Ruxience, among others), off-label to help prevent future NMO attacks.
The autoimmune disorder NMO causes a person’s immune system to attack the optic nerves and spinal cord. Periods of relapse can cause additional damage and worsening disability if the condition goes untreated.
Symptoms can include:
- loss of vision
- eye pain
- changes in perception and sensation
- loss of control of the bladder and bowels
Diagnosis includes ruling out other conditions, determining whether a person has AQP4 antibodies, and checking whether they meet other criteria.
Prompt diagnosis and treatment can help prevent worsening symptoms and disability from relapses.