Neuromyelitis optica (NMO): symptoms, causes and treatment

Neuromyelitis optica is an autoimmune condition, which means the immune system attacks part of the body it should protect. In NMO, the NHS says it attacks nerves in the eyes or the spinal cord. The condition is rare, and it is also known by the names NMO spectrum disorder (NMOSD) and Devic's disease.

Because NMO affects the eyes and spinal cord, two terms come up often. Optic neuritis is inflammation of the optic nerve that causes eye pain and vision problems. Transverse myelitis is inflammation of the spinal cord that can cause weakness, numbness and bladder or bowel problems. The NHS says some people have symptoms affecting only the eyes (optic neuritis), or only the spinal cord (transverse myelitis).

The NHS says symptoms vary between people and can be mild or severe. They can include:

• Eye pain and problems with eyesight or colour vision, in one or both eyes.

• Sharp, burning or shooting nerve pain in the back, neck, arms or legs.

• Weakness, numbness or paralysis in the arms or legs.

• Muscle spasms, where the muscles suddenly tighten.

• Bladder and bowel problems, such as incontinence, constipation or not being able to pee.

• Sexual problems, such as not being able to get an erection or reach orgasm.

• Vomiting and hiccups.

According to the NHS, symptoms start over a few hours or days and usually last a few days or weeks before gradually improving. Some people recover well with treatment, while others have longer-lasting problems.

It is common for symptoms to return. These relapses can happen after a few weeks, months or years. The NHS says that in some people relapses lead to permanent problems such as sight loss or mobility problems, which is why treatment aims to reduce the risk of relapse as well as treat each attack.

The NHS says anyone diagnosed with NMO needs treatment to stop the inflammation in their nerves and reduce the risk of relapses. Treatment has three parts.

• Initial treatment and treatment of relapses: high-dose steroid injections, plasma exchange (some of your blood is removed, treated and returned to your body) and immunoglobulins (antibodies from the blood) given through a drip into a vein.

• Preventing relapses: medicines taken long term that reduce the activity of the immune system, which may include immunosuppressants such as azathioprine, steroid tablets such as prednisolone, and biological medicines such as rituximab.

• Treating symptoms: painkillers, medicines for nerve pain such as amitriptyline or gabapentin, muscle relaxants or anticonvulsants for spasms such as baclofen or carbamazepine, medicines for bladder problems such as oxybutynin, and laxatives for bowel problems.

• Rehabilitation: physiotherapy, including advice on exercises and stretching, and occupational therapy to help with daily activities when there is muscle weakness or mobility problems.

If a GP thinks you could have NMO, the NHS says they will refer you to a neurologist (a specialist in nerve conditions) for tests and treatment. It can be hard to diagnose because symptoms vary and are similar to other conditions, such as multiple sclerosis (MS).

Tests the NHS lists are blood tests, an MRI scan of the brain and spinal cord, a lumbar puncture (a sample of fluid from around the spinal cord) and tests to check your eyes and vision. Your neurologist decides which are needed.

The NHS says it is not known what causes NMO. Sometimes it happens after a virus such as flu. It is not an inherited condition, but it is more common in people with other autoimmune conditions and in those with close relatives who have autoimmune conditions. It is more common in women and in people of Asian or Black African origin.

The NHS notes that NMO symptoms are similar to other conditions such as MS, which is one reason diagnosis can be hard. The NHS descriptions of the two conditions show some overlap and some differences. This table sets out only what those NHS pages say.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you think you could have NMO. Prompt assessment matters because the NHS says relapses can lead to permanent problems such as sight loss or mobility problems.

The NHS also says to call 999 or go to A&E if you have sudden weakness or numbness in one arm, loss or blurring of vision, or problems with balance and co-ordination, because these could be signs of a stroke. Do not drive yourself to A&E.

The NHS names the Brain Charity, the Brain & Spine Foundation and the Transverse Myelitis Society as charities that can support people with NMO and their families. It also says your care team will pass information about you and your condition to the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS), which helps scientists look for better ways to prevent and treat the condition. You can opt out of the register at any time.

On the NHS, care starts with an urgent GP or NHS 111 contact and referral to a neurologist. Because NMO is rare and needs specialist immune treatment, ongoing care is normally led by neurology. Some people see a neurologist privately for an earlier opinion or tests. Either way, results and treatment plans should be shared with your GP and NHS neurology team so that relapse treatment and long-term medicines are coordinated.