Neuromyelitis Optica

Neuromyelitis optica (NMO) is a rare chronic condition that affects your eyesight and your ability to move. It’s an autoimmune disorder, meaning it happens because your immune system mistakenly attacks parts of your central nervous system.

This condition has undergone name changes over the years. The condition’s original name, Devic’s disease, comes from Eugène Devic, the French neurologist who first described it. However, an international group of experts gave the condition its current name in 2015. This condition’s full, formal name is neuromyelitis optica spectrum disorder (NMOSD). But it’s still common for healthcare providers and other experts to simply call it neuromyelitis optica.

Experts previously thought that NMO was a rare type of multiple sclerosis (MS). However, they know now that it’s a separate condition.

Who does neuromyelitis optica affect?

NMO is much more likely to affect women and people assigned female at birth, who make up about 80% to 90% of cases. It usually affects people between the ages of 30 and 40. NMO in children is very uncommon, making up only 5% or so of cases.

People of all races and ethnic backgrounds can develop NMO, but it doesn’t affect people of all backgrounds at the same rates. NMO affects people of African descent, especially African Caribbean descent, at higher rates. The Caribbean island of Martinique, a French territory, has the highest number of cases for the size of its population, about 10 per 1000,000 people. It can also disproportionately affect people of Asian descent.

How common is neuromyelitis optica?

NMO overall is rare. The average number of people with NMO per 100,000 is between 0.3 and 4.4. That means there are between 1,000 and 14,600 cases in the United States and between 24,000 and 350,600 cases worldwide.

How does neuromyelitis optica affect my body?

To understand how NMO affects you, it helps to know a little about the makeup of your nervous system. Your nervous system consists of your brain and spinal cord (the optic nerves, which are the cranial nerves that allow you to see, are technically part of your brain also).

Together, your brain and spinal cord are known as the central nervous system. The network of nerves that branch outward throughout your entire body makes up your peripheral nervous system.

Your nervous system transmits information to and from your brain using chemical and electrical signals. Those signals travel through specialized cells known as neurons, which form incredibly complex connections to other neurons around them.

A key part of every neuron is an arm-like extension called the axon, which carries electrical signals to the synapses (pronounced sin-apps-is) at the end of the axon. These finger-like extensions are where the electrical signals in the neuron become chemical signals. The synapses connect and communicate with other nearby neurons.

Around the axon, there’s a thin, protective coating called myelin, which is made up of fatty chemical compounds. Myelin helps with conduction of electrical signals along the axon and protects it from damage. NMO is a demyelinating disease, meaning it involves the myelin coating of the axon. Without the protective myelin coating, the axon is vulnerable to damage and deterioration.

Damage from NMO tends to involve neurons in two specific areas: The optic nerve that connects your eyes to your brain, and your spinal cord, which is the central connection point for nerve signals to reach before heading to your brain. NMO can affect your spinal cord at different levels, and every nerve that connects to your spinal cord below the affected area of your spinal cord can show the effects.