Neuromyelitis optica

Also called NMO, NMOSD, Devic's disease

An MS-like condition that is not MS, and the distinction is critical because some MS drugs make it dramatically worse.

What it is

An autoimmune condition attacking the optic nerves and spinal cord, causing severe attacks of visual loss and paralysis.

For decades it was thought to be a variant of multiple sclerosis. It is not, and the difference matters enormously.

**Several disease-modifying drugs used in MS, including interferon beta and natalizumab, make neuromyelitis optica substantially worse.** Misdiagnosis therefore causes direct harm, and this is one of the clearest examples in neurology of getting the label right being a safety issue.

It is identified by a blood test for aquaporin-4 antibodies, which is positive in most people. A related condition, MOG antibody disease, behaves somewhat differently and is also distinguished by a blood test.

Attacks are far more severe than typical MS relapses and cause permanent damage if not treated fast. **Optic neuritis or spinal cord symptoms in this condition are an emergency**, needing high-dose steroids and often plasma exchange within days.

Unlike MS, disability accumulates through attacks rather than through gradual progression, so preventing attacks is everything, and effective preventive treatments now exist including rituximab and newer targeted drugs.

It is more common in women, and in people of African and Asian heritage.

Signs you might notice

Optic neuritis: pain on moving the eye, then rapid loss of vision, often severe and sometimes in both eyes.

Transverse myelitis: weakness or paralysis of the legs, a band-like tightness around the trunk, numbness, and loss of bladder and bowel control, developing over hours to days.

Severe hiccups, nausea and vomiting lasting days, from a lesion in the brainstem. This is a characteristic and frequently missed presenting feature.

Painful spasms.

**Emergency: any new visual loss or any new weakness, numbness or continence change.** Attacks cause permanent damage and treatment is time-critical.

Anybody diagnosed with MS whose attacks are unusually severe, who has bilateral optic neuritis, or who has intractable hiccups and vomiting, should be tested for aquaporin-4 antibodies.

How it can affect day-to-day life

The urgency of attacks changes how people live with it. Everybody should have a written plan and a direct route into the neurology service, because a week's delay can mean permanent blindness.

Preventive treatment is lifelong and is usually immunosuppressive, so infection risk, vaccination and monitoring all become part of life.

Neuropathic pain and painful spasms are common and need specific treatment.

Bladder and bowel management often needs specialist input from the start.

Fatigue is significant, as in MS.

Because it is rare, local teams may have limited experience, and access to a specialist NMO service, of which there are designated centres in the UK, is worth pushing for; treatments are commissioned through them.

The visual loss can be severe and permanent, and practical sight-loss support is frequently not arranged. See visual impairment.

Supporting someone well

Ask for the aquaporin-4 antibody test where MS is suspected but attacks are severe, bilateral, or accompanied by intractable hiccups and vomiting.

Never accept interferon beta or natalizumab without that distinction being made.

Treat any new visual loss, weakness or continence change as an emergency; attacks need treating within days.

Have a written attack plan and a direct number for the neurology team.

Ask for referral to a designated NMO specialist service.

Take preventive treatment consistently; preventing attacks is what preserves function.

Keep vaccinations up to date, avoiding live vaccines while immunosuppressed.

Ask for pain, bladder, bowel and fatigue management in their own right.

Ask for sight-loss support and registration where vision is affected.

Where to get help

A GP practice for urgent neurology referral; a designated NMO service for treatment.

A and E or the neurology team the same day for new visual loss or weakness.

MS Society and RNIB both provide relevant support.

Brain and Spine Foundation run a helpline covering rare neurological conditions.