Author Response: Practice Current: How do you treat neuromyelitis optica?

I thank Dr. Avasarala for responding to the Practice Current on neuromyelitis optica,¹ and for highlighting some key unresolved questions in this field.

Perhaps the use of ocrelizumab in neuromyelitis optica spectrum disorder (NMOSD) might increase following its approval in 2017 for the treatment of relapsing-remitting and primary progressive multiple sclerosis; our practice survey preceded or overlapped with this, and it would be interesting to repeat the assessment a few years down the road to see if preferences have changed in response to new evidence or trials. Concurrently, guidelines for monitoring CD19/20 cell counts in patients on B-cell-targeting therapies will likely evolve, and I was pleased to come across a recent article by Dr. Avasarala² on this topic, suggesting that CD19 cell populations may be used as a surrogate for CD20 cells on a monthly basis to guide ocrelizumab redosing parameters.

The question of double-seronegative NMOSD is one that we could discuss only briefly in the main body of the article. However, we were able to delve into this topic in some more detail with the experts we interviewed, particularly Dr. Maria Isabel Leite (Oxford), who agreed that this is a difficult diagnosis to make, and one that she basically considers a diagnosis of exclusion, ruling out other competing differential diagnoses. If a seronegative patient has a relapse, the practice favors reviewing the diagnosis, including retesting for aquaporin-4 and MOG antibodies, and if no better etiologic diagnosis is found, then chronic immunosuppressive treatments are considered. I agree that this remains a gray area meriting further systematic study.

I also agree that high-quality data collection and sharing on pregnancies in NMOSD (and disease-modifying drugs in this setting) will be helpful. Indeed, a recent international cohort study found that pregnancy after NMOSD onset is an independent risk factor for miscarriage—particularly if pregnancies were conceived at times of high disease activity—further highlighting the importance of this topic.³

• © 2018 American Academy of Neurology