Devic’s disease, now more commonly called neuromyelitis optica (NMO) or neuromyelitis optica spectrum disorder (NMOSD), is an autoimmune inflammatory disorder of the central nervous system that primarily attacks the optic nerves and spinal cord. It causes episodes of vision loss, limb weakness or paralysis, and pain that can be severe and disabling. Once considered a variant of multiple sclerosis, it is now recognized as a distinct condition with its own biological mechanism, diagnostic test, and targeted treatments.
How Devic’s Disease Attacks the Nervous System
In most people with Devic’s disease, the immune system produces antibodies that target a protein called aquaporin-4, a water channel found on the surface of astrocytes, the support cells of the brain and spinal cord. These antibodies bind to the outside of astrocytes and trigger a destructive chain reaction. The body’s complement system, a branch of immune defense normally aimed at invaders, activates against the body’s own cells. Immune cells including natural killer cells and white blood cells pile on, destroying the astrocytes.
Once astrocytes are damaged, the surrounding nerve insulation (myelin) breaks down, and the nerve fibers themselves can be injured. This is why attacks tend to cause more severe, lasting damage than what’s seen in multiple sclerosis. The destruction concentrates wherever aquaporin-4 is densely packed, which explains why the optic nerves, spinal cord, and a specific area of the brainstem called the area postrema are the most common targets.
Symptoms of an Attack
Devic’s disease typically strikes in distinct episodes, or relapses, rather than as a slow, steady progression. The two hallmark attacks are optic neuritis and transverse myelitis.
Optic neuritis causes pain with eye movement and decreased vision in the affected eye. Vision loss can be severe, and blindness is not uncommon. In the classic presentation, rapid-onset blindness in one or both eyes is followed within days or weeks by spinal cord symptoms. Compared to optic neuritis in MS, attacks in Devic’s disease tend to cause more severe damage to the retinal nerve fibers and poorer recovery of visual sharpness and contrast sensitivity.
Transverse myelitis, the spinal cord component, causes limb weakness, numbness, or partial paralysis. It can also produce shooting pain or tingling in the neck, back, or abdomen, along with loss of bowel and bladder control. On MRI, the spinal cord inflammation typically stretches across three or more vertebral segments, a pattern called a longitudinally extensive lesion. This is one of the key features that distinguishes it from MS, where spinal lesions tend to be shorter.
Some people also experience episodes of uncontrollable vomiting and hiccups, which result from inflammation in the brainstem. These symptoms, once dismissed as unrelated, are now recognized as a characteristic feature of the disease.
Diagnosis and Blood Testing
The discovery of the aquaporin-4 antibody transformed how Devic’s disease is diagnosed. A blood test can detect these antibodies, present in up to 80% of people with the condition. The best current testing methods, cell-based assays, detect the antibody in roughly 92 to 94% of confirmed cases with near-perfect specificity, meaning false positives are extremely rare. Older testing methods like standard ELISA are less sensitive, catching only about 60% of cases, so the type of assay matters.
Beyond the blood test, diagnosis requires at least one core clinical event: optic neuritis, transverse myelitis with a long spinal lesion on MRI, or an area postrema syndrome (the vomiting and hiccup episodes) with a corresponding brainstem lesion. Brain MRI scans in Devic’s disease are often normal, which is another contrast with MS, where scattered brain lesions are typical.
How It Differs From Multiple Sclerosis
For years, Devic’s disease was misdiagnosed as MS, and the distinction matters because some MS medications can actually worsen NMO. Several key differences set them apart:
- Antibody marker: The aquaporin-4 antibody is specific to Devic’s disease and is not found in MS.
- Vision damage: Visual impairment after optic neuritis is typically severe in Devic’s disease but moderate in MS. Permanent optic nerve atrophy develops in over 70% of NMO patients with optic neuritis, while MS patients tend to recover more visual function.
- Spinal cord lesions: NMO produces long spinal lesions spanning three or more segments. MS spinal lesions are usually shorter.
- Brain involvement: Early brain MRI is often normal in NMO but shows scattered lesions in MS.
- Disease course: NMO attacks tend to cause more severe damage with less recovery between episodes, leading to stepwise accumulation of disability.
The Role of MOG Antibodies
A subset of people with NMO-like symptoms test negative for the aquaporin-4 antibody but positive for a different antibody targeting myelin oligodendrocyte glycoprotein (MOG). This is now considered a separate condition called MOG antibody disease, or MOGAD. It more commonly affects younger males and tends to have a better long-term outlook. Spinal cord and brain lesions in MOGAD resolve more frequently on follow-up MRI. In one study, six out of seven MOGAD patients showed complete resolution of their spinal lesions within a few months, compared to only a fraction of aquaporin-4-positive patients. Bilateral optic neuritis (both eyes at once) is more common in MOGAD, while lasting optic nerve atrophy points more toward aquaporin-4-positive disease.
Disease Course and Prognosis
Devic’s disease typically follows a relapsing course. Relapses are often associated with incomplete recovery, meaning each attack can leave behind a new layer of permanent neurological damage. In a large European study of 433 patients with aquaporin-4-positive NMOSD, about 30% experienced at least one relapse after their initial attack, with roughly 17% of those having three or more relapses. The cumulative effect of these attacks is the primary driver of long-term disability, making prevention of relapses the central goal of treatment.
Treatment During an Attack
When a relapse occurs, the first-line treatment is a course of high-dose intravenous steroids, typically given daily for three to seven consecutive days, followed by a gradual taper over about two weeks. If steroids don’t produce adequate improvement, plasma exchange is used as a rescue therapy. This procedure filters the harmful antibodies out of the blood and is particularly logical for a disease driven by a strong antibody response.
Long-Term Prevention of Relapses
Because each relapse can cause irreversible damage, long-term preventive therapy is critical. Four targeted biologic medications are now approved specifically for aquaporin-4-positive NMOSD, each working through a different mechanism:
- Complement blockers (eculizumab, approved 2019; ravulizumab, approved 2022): These block a key complement protein to prevent the immune system from forming the destructive complex that kills astrocytes. Eculizumab requires infusions every two weeks, while ravulizumab, a longer-acting version, is given every eight weeks. Both carry a risk of serious meningococcal infection, so vaccination is required before starting treatment.
- B cell depletion (inebilizumab, approved 2020): This targets immune cells that produce the harmful antibodies, depleting them from the body. It’s given by infusion every six months after initial loading doses.
- Inflammation signaling blocker (satralizumab, approved 2020): This blocks a signaling molecule that drives the inflammatory cascade. It’s the only option given as a self-administered injection under the skin, dosed every four weeks after an initial loading period.
These targeted therapies represent a major shift from the older approach of using broad immunosuppressants. They were specifically designed around the biology of Devic’s disease, and their approval has given patients more effective options for staying relapse-free.