Neuromyelitis

Neuromyelitis, commonly referred to as neuromyelitis optica or neuromyelitis optica spectrum disorder (NMOSD), is an autoimmune inflammatory demyelinating disease of the central nervous system. It is characterized by episodes of optic neuritis and transverse myelitis and is distinguished from multiple sclerosis by its clinical features, antibody associations, and treatment responses. The discovery of aquaporin-4–specific antibodies (AQP4-IgG) has refined diagnosis and classification, though a subset of patients has MOG-IgG–associated disease rather than AQP4-IgG–positive NMOSD.

Clinical features typically include acute or subacute optic neuritis with vision loss, eye pain, and impaired color vision, and episodes of transverse myelitis with bilateral or segmental weakness, sensory disturbance, and bladder or bowel dysfunction. A hallmark at times is longitudinally extensive spinal cord involvement, spanning three or more vertebral segments. Some patients experience area postrema syndrome (intractable hiccups, nausea, vomiting), highlighting the disease’s potential to affect brainstem regions.

Pathophysiology is autoimmune, with antibodies targeting aquaporin-4 water channels on astrocytes, leading to secondary demyelination. NMOSD can be relapsing or monophasic; relapses drive accumulated disability. MOG-IgG–associated disorders are considered a related but distinct group.

Diagnosis relies on clinical presentation, MRI findings of optic nerves and spinal cord, and serology. AQP4-IgG positivity supports NMOSD; MOG-IgG testing helps distinguish MOG-associated disease. CSF often shows inflammatory features but oligoclonal bands are less common than in multiple sclerosis.

Treatment emphasizes rapid management of attacks (high-dose IV methylprednisolone, plasmapheresis if needed) and long-term immunotherapy to reduce relapses (rituximab, azathioprine, mycophenolate, or newer agents such as eculizumab, inebilizumab, and satralizumab). Prognosis improves with early, targeted therapy, but disability may accrue with relapses.