Neuromyelitis Optica Spectrum Disorder (NMOSD) and MOG-Associated Disease are a group of severe autoimmune diseases in which the immune system attacks the optic nerve and spinal cord. They cause sudden loss of vision, often in both eyes, and without timely treatment can lead to permanent blindness. Seeking medical care early is critical.
What are NMOSD and MOG-associated disease
These are autoimmune demyelinating diseases of the central nervous system. “Demyelinating” means the immune system destroys myelin — the protective coating of the nerve fibres that carry signals from the eye to the brain. In neuromyelitis optica (NMOSD, Neuromyelitis Optica Spectrum Disorder), the body produces antibodies against a protein called aquaporin-4 (AQP4). In MOG-associated disease, the antibodies target a different protein — myelin oligodendrocyte glycoprotein (MOG). Both conditions mainly affect the optic nerve and spinal cord. It is very important to distinguish them from multiple sclerosis, because the treatment is completely different, and some multiple-sclerosis medications can actually worsen these diseases.
Causes
- A malfunction of the immune system, which begins to attack the body’s own nerve tissue.
- Production of antibodies against aquaporin-4 (AQP4) — typical of NMOSD.
- Production of antibodies against the MOG protein — typical of MOG-associated disease.
- The exact trigger of this process is unknown; sometimes a preceding infection acts as a trigger.
- The disease is not passed from person to person and is not contagious.
Symptoms
- Sudden loss of visual acuity in one or both eyes, sometimes one after the other.
- Pain in or around the eye that worsens with eye movement.
- Disturbed colour perception — colours appear pale or washed out.
- A dark spot or “curtain” appearing in front of the eye.
- Weakness or numbness in the arms and legs, difficulty walking (when the spinal cord is affected).
- Sometimes persistent hiccups, nausea or vomiting that will not stop (a sign of brainstem involvement).
Why this is a neuro-ophthalmic condition
These diseases sit at the border between neurology and ophthalmology, which is why they are assessed by a neuro-ophthalmologist. The problem does not begin in the eye itself but in the optic nerve and the nervous system. A routine eye examination may look almost normal, while vision is sharply reduced. Only a consultation with a neuro-ophthalmologist can properly assess the condition of the optic nerve, order the necessary tests, and refer you for treatment in time to preserve your sight.
Diagnosis
- Blood test for antibodies against aquaporin-4 (AQP4) and MOG — the key investigation for making the diagnosis.
- Magnetic resonance imaging (MRI) of the brain, optic nerves and spinal cord.
- Optical coherence tomography (OCT) — measures the thickness of the retinal nerve fibres and assesses damage.
- Visual evoked potentials — check the speed at which the signal travels from the eye to the brain.
- Testing of visual acuity, visual fields and colour perception.
- If needed, examination of the cerebrospinal fluid.
Treatment
Treatment has two goals: to stop the acute flare-up and to prevent new attacks. During a flare-up, high doses of corticosteroids are used, and in severe cases a blood-cleansing procedure (plasma exchange). To prevent future attacks, medications that suppress the immune system are prescribed. The most important thing is to start treatment as early as possible: every day of delay reduces the chance of recovering vision. That is why, at the first signs of sudden visual loss, you should not wait — see a doctor immediately. Treatment started in time can preserve sight and prevent disability.
When to seek urgent help
Seek medical help immediately if you experience a sudden loss of vision in one or both eyes, pain in the eye during movement, loss of colour, or a dark spot in front of the eye. Weakness in the limbs, numbness, or persistent hiccups and vomiting are also warning signs. In these diseases time is decisive — the earlier treatment begins, the greater the chance of preserving your sight.
German Eye Clinic, phone 0 800 507 670, the “Neuro-ophthalmologist Consultation” service page.
