Neuromyelitis optica (NMO) and multiple sclerosis (MS) are distinct autoimmune disorders that affect the central nervous system. NMO predominantly targets the eyes and the spinal cord, while MS affects the entire central nervous system. Although NMO is a rare condition, it resembles MS in many ways. As a result, people with one condition are sometimes initially misdiagnosed as having the other.

“After 22 years of being told I had MS, my doctor told me I actually have NMO. I’m having a hard time wrapping my head around a new diagnosis and having to start from scratch again,” a MyMSTeam member wrote.

Currently, researchers are studying the signs and symptoms of NMO to differentiate it from other autoimmune diseases such as MS. It is important to understand these differences so that people living with NMO can receive proper treatment and care.

What Is NMO?

NMO is also known as neuromyelitis optica spectrum disorder (NMOSD) or Devic's disease. It most commonly appears during adulthood between the ages of 40 and 50. However, symptoms may occur at any age and can lead to paralysis and blindness. Similar to MS and other autoimmune diseases, NMO is more commonly found in women than men. Unlike MS, NMO “has been reported to be more prevalent in Asians and Africans,” according to the National Institutes of Health.

There are two types of NMO: relapsing and monophasic. People with the relapsing form of NMO experience periodic episodes with long recovery time in between. Those with the monophasic form of NMO experience unpredictable series of episodes that can occur for a month or longer, with recovery times ranging from several hours to days.

According to the MS Society, there are 250,000 people worldwide living with NMO and more than 4,000 people in the United States.

What Causes NMO and MS?

Although the underlying cause of NMO remains unknown, experts have found that 50 percent of people with the condition also have a family history of autoimmune disorders or have a preexisting autoimmune condition such as Sjogren’s syndrome, celiac disease, or systemic lupus erythematosus (SLE). An antibody biomarker (serum aquaporin-4 immunoglobulin G, or AQP4-IgG) is found in 80 percent to 99 percent of people living with NMO.

Both NMO and MS are caused by the immune system attacking the central nervous system. However, NMO causes damage only to the optic nerves and the spinal cord, producing swelling and inflammation within the optic and spinal tissues. Alternatively, MS affects the entire central nervous system.

Another key difference between MS and NMO is the severity and occurrence of episodes. In MS, the initial episode is typically mild and not life-threatening. In NMO, the initial episode is abrupt and causes severe symptoms with long-term effects. Also, NMO relapse periods are shorter than MS relapses.

Symptoms of NMO and MS

Vision problems are often the first noticeable symptom of NMO and MS. More than 16,700 MyMSTeam members report having vision problems as a symptom of MS. “I have lost 50 percent peripheral vision in my left eye and 25 percent in my right eye,” a MyMSTeam member wrote.

Read more details about vision problems and MS.

A person living with NMO or MS may experience the following symptoms:

• Eye pain
• Loss of color vision
• Vision loss
• Spinal cord attacks
• Weakness
• Numbness or pain
• Loss of bowel function and bladder control

Notably, inflammation in the eyes and spinal cord tend to be more severe in NMO than in MS.

The following symptoms are common in NMO but not MS:

• Vision loss that may affect both eyes at the same time
• Uncontrollable vomiting and nausea
• Recurrent hiccups that may last up to a month
• Confusion, seizures, or coma in children living with NMO

The following symptoms are common in MS but not NMO:

• Depression
• Vision loss typically affects one eye at a time
• Changes in problem-solving, reasoning, and memory

Symptoms vary from person to person, ranging from mild to severe. NMO episodes and attacks can have devastating and irreversible effects on how a person functions on a daily basis. Because NMO and MS symptoms overlap, it’s important that your doctor accurately diagnoses which condition you have as soon as possible. A misdiagnosis can lead to improper or delayed treatment, which can increase your risk of long-term disability.

Diagnosing NMO vs. MS

Both NMO and MS are diagnosed using neurological exams and MRI scans of the brain and spinal cord. However, experts have found that people with NMO usually have normal MRI brain scans early in the development of the disease. In contrast, MRI brain scans of people living with MS will display MRI abnormalities. Additionally, about 80 percent of people diagnosed with NMO have clear-cut, elongated lesions in the spinal cord that are not commonly found in people diagnosed with MS.

Your doctor may seek additional tests to distinguish NMO from MS, such as:

• Optic-nerve imaging
• Blood tests for the biomarker AQP4-IgG
• Spinal fluid samples
• Stimuli response assessment

NMO is a challenging disease, but it is helpful to have an accurate and early diagnosis to determine the best treatment options.

Treatment for NMO and MS

Although there is currently no cure for NMO, emerging medical advances are helping make the condition more manageable. There are a variety of medications approved by the U.S. Food and Drug Administration, as well as short- and long-term treatments that may help to inhibit future episodes and attacks. Treatments include:

• Steroids (or corticosteroids) — such as Solu-Medrol (methylprednisolone) — to stop the immune system's effect on nerves
• Immunosuppressant drugs such as Imuran and Azasan (azathioprine), Cellcept (mycophenolate), and Rituxan (rituximab)
• Plasma exchange to help restore vision loss or movement from recent episodes or attacks
• Other treatments to address symptoms such as weakness, numbness, pain, and loss of bowel functioning and bladder control

NMO episodes and attacks have more than a 90 percent chance of recurring. It is important for people living with NMO to have a continuous, long-term treatment plan to prevent episodes and to reduce the severity of attacks.

Treatments used for NMO are very different from treatments used to prevent MS relapses. In fact, anti-inflammatory medications used to treat MS may cause more severe attacks in people living with NMO.

Talk With Others Who Understand

MyMSTeam is the social network for people with MS and their loved ones. On MyMSTeam, more than 164,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Are you living with NMO or MS? Share your experience in the comments below, or start a conversation by posting on your Activities page.