What’s NMOSD? A Neurologist’s POV

Never heard of neuromyelitis optica spectrum disorder? An expert explains the nuances of diagnosing and treating this rare disease.

by Lara DeSanto Health Writer

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune disorder of the brain and spinal cord that occurs in one to 10 people per 100,000 worldwide, according to the National Organization of Rare Diseases (NORD). Even more complicated than its name is the disorder itself, which can be seriously debilitating if not diagnosed promptly and treated with the right medications.

To learn more about this rare and chronic condition, we spoke to Mary Rensel, M.D., a neurologist at Cleveland Clinic’s Mellen Center for Multiple Sclerosis Treatment and Research in Cleveland, OH, who discussed NMOSD’s often confusing symptoms, and why this disease can be so tricky to diagnose.

HealthCentral: What are the typical symptoms of NMOSD?

Dr. Rensel: The symptoms of NMOSD are very severe and noticeable. A common symptom is something called optic neuritis, which is inflammation in the big nerve in the back of the eye, which can cause painful vision loss. With relapses of this disease, there is a risk [of] neurologic symptoms leading to very severe neurologic disability. So the key to treatment of this disease is to prevent relapses. This makes early diagnosis important.

HC: Why can this condition be so difficult to diagnose?

Dr. Rensel: It’s so rare that not everyone is familiar with it. You go to a doctor, and someone has seen maybe one or two cases with similar symptoms. Additionally, a lot of NMOSD has crossover with multiple sclerosis (MS)—the symptoms can look a bit like MS, and sometimes patients are told they have MS when they really have NMOSD. They may even be put on MS medications, which can help in some cases and make things worse in others. That’s why accurate, early diagnosis is really important. The other thing about this disease is that it can happen in all ages, including kids and teens. People have to know about it because even though it’s rare, it can be very damaging if you don’t treat it correctly.

HC: What are the main ways to distinguish NMOSD from MS symptoms?

Dr. Rensel: There are three classic things: Number one is optic neuritis, which is loss of vision and pain around or behind the eyes, and it can be complete loss of vision or just dimming of the vision. The second thing is something called longitudinally extensive myelitis, which is when a very long area of the spinal cord (meaning at least three inches) is inflamed. [This is rare in MS.] I have someone I just put in the hospital the other day whose whole spinal cord was inflamed, from beginning to end.

The third thing is, when it’s very severe and very quick onset, it makes us think [it’s] NMOSD. MS tends to come on a little bit more slowly and over a few weeks or years. For example, I had a 22-year-old gentleman who all of the sudden couldn’t move his legs and had numbness up to his chest, out of nowhere. One minute he was fine, and then one minute he wasn’t. His family brought him to the emergency room, he was admitted to another hospital, and then he was put in rehab. Then they called me and said, ‘We think he has MS,’ but then we saw him and we could tell just by the severity of the symptoms and how suddenly it started that we should think about NMOSD. He did end up having NMOSD.

HC: How has the process of diagnosing NMOSD changed over time?

Dr. Rensel: In 2005, Dr. Vanda Lennon’s lab at the Mayo Clinic discovered the blood test for aquaporin-4 antibodies, which helps diagnose NMOSD. That was super-exciting because early diagnosis is so important to try to prevent relapses. Unfortunately, this is one of the diseases where I’ve had young patients who have died due to very severe relapses.

It’s actually a really exciting day for NMOSD right now for a few reasons: Number one, the diagnostic criteria was redefined in 2015 and people around the world have agreed on a certain list of diagnostic criteria so people can get diagnosed very quickly. And, there are blood tests to support the diagnosis now. [In addition], there are three U.S. Food and Drug Administration (FDA)-approved medications for NMOSD. That’s exciting because otherwise we would try to borrow medications from other diseases to try to help these folks, and before this, the best treatment wasn’t known. The first of these three treatments was just FDA-approved in 2020.

HC: What advice can you offer folks with these types of symptoms to help get an accurate and timely diagnosis?

Dr. Rensel: I would make sure to get to high-level care, the best you can in the area. These days, with virtual medicine, you can get access to different doctors. A lot of times there is a specialist you can see virtually even though it would be three to four hours by car, and they can look over your case or test results and help you determine next steps. Many medical systems are doing consultations virtually these days, so you can have more access hopefully to the specialists you might need.

I would also say that if you do have NMOSD, reach out to some of the patient support groups that exist, such as the Guthy-Jackson Charitable Foundation; also, the National MS Society provides information on NMOSD, as well as MS. The number-one priority is to make sure your diagnosis and treatment are accurate. Number two is to get some support through patient advocacy partners.

Lara DeSanto
Meet Our Writer
Lara DeSanto

Lara is a former digital editor for HealthCentral, covering Sexual Health, Digestive Health, Head and Neck Cancer, and Gynecologic Cancers. She continues to contribute to HealthCentral while she works towards her masters in marriage and family therapy and art therapy. In a past life, she worked as the patient education editor at the American College of OB-GYNs and as a news writer/editor at WTOP.com.