Neuromyelitis optica, also known as neuromyelitis optica spectrum disorder, is a rare chronic inflammation of the central nervous system mediated by autoantibodies. Previously considered a variant of multiple sclerosis, it is now a distinct disease. In most of the patients, antibodies are produced against astrocyte aquaporin 4 (AQP4) water channel that leads to recurrent exacerbations of optic neuritis and myelitis. Some patients may have involvement of the brainstem and brain causing postrema syndrome or diencephalic syndrome leading to hiccups, nausea, vomiting, narcolepsy, muscle affection. Patients also suffer from symptoms of fatigue, pain, headache, sleep disorders, and depression.(1)
The mean age of disease onset is around 39 years and women are more frequently affected by neuromyelitis optica, especially in cases of AQP4 seropositivity, in which the female to male ratio can be 10:1. Even after treatment, there is incomplete recovery from relapses and remission from the disease is rare. Relapsing neuromyelitis optica accounts for about 80-85% of all cases and each relapse leads to increasing neurologic disability. The prognosis is poorer with increased mortality rates in patients with long term immunosuppressive therapy.(1)
What Is The Best Treatment For Neuromyelitis Optica?
The treatment of neuromyelitis optica depends on whether the treatment is for acute attacks or for long term therapy of the patient. Acute attacks of neuromyelitis optica are managed with systemic corticosteroids or therapeutic plasma exchange. High dose IV methylprednisolone (3-5 days) is the first line of treatment when the diagnosis of neuromyelitis optica is confirmed or suspected. Early pulse therapy is crucial for minimizing the loss of axons during the attack. If no improvement or worsening symptoms are seen with corticosteroid therapy, then therapeutic plasma exchange (5-7 cycles) is the treatment of choice. Studies have shown superior results with add on therapeutic neuromyelitis optica to glucocorticoids than with glucocorticoids alone.(2)
Since the course of neuromyelitis optica is relapsing in nature, long term immunosuppressive therapy is important for disease management and better prognosis. The long term therapy for nearly 5 years has been suggested for the prevention of disease. However, the duration of treatment in each patient should be individualized depending on the treatment efficacy, the clinical course of the disease and associated complications. Low dose prednisolone monotherapy was found effective in reducing relapses of the disease; however, it is used as a combination therapy with azathioprine or cyclosporine.(2)
Azathioprine, a purine analog, has an antiproliferative and immunosuppressive effect. It takes 3-6 months to be fully effective, so initially, oral prednisone has to be given and can be tapered off when azathioprine is fully effective. Bone marrow depression and pancytopenias is a common side effect of the drug. Rituximab causes a reduction in antibody production and is directly against CD20 and B lymphocytes. The side effects include pruritus, rash, headache, or fever-related to IV infusion. Azathioprine and rituximab are the two most commonly used drugs for immunosuppressive therapy in neuromyelitis optica. Some comparative studies have shown rituximab to be more superior to azathioprine; therefore, rituximab is currently the most effective treatment for neuromyelitis optica.(1)
Mycophenolate mofetil is another immunosuppressant that is used in the treatment of neuromyelitis optica. Mycophenolate mofetil has fewer side effects than azathioprine with similar efficacy. Intravenous immunoglobulin has also been found effective in the treatment of neuromyelitis optica; however, there are very few studies on the efficacy of the drug. Methotrexate has also been used as a treatment option in patients who do not respond to first-line treatment and have greater side effects with other therapies. Multiple sclerosis medications such as interferon beta, fingolimod, alemtuzumab, natalizumab, glatiramer acetate, dimethyl fumarate are found ineffective in the management of neuromyelitis optica and have been known to worsen the disease; therefore, these are contraindicated in the treatment of neuromyelitis optica.(1)
There are emerging therapies that are currently undergoing clinical trials, such as eculizumab, tocilizumab, and C1-esterase inhibitor. These drugs have shown promising results in clinical trials and hopefully, they will be available as newer drugs for the treatment of neuromyelitis optica in future.(2)