Page created on June 3, 2021. Last updated on April 2, 2022 at 15:02
Definition and epidemiology
Neuromyelitis optica (NMO), more properly called neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory demyelinating disease of the central nervous system characterised mainly by optic neuritis and acute longitudinally extensive (> 3 vertebral segments) transverse myelitis. It’s associated with anti-aquaporin 4 antibodies (anti-AQP4 antibodies).
It mostly occurs in 40 – 60 year olds, and mostly in women. The clinical features may be similar to MS so it’s important to distinguish them. However, the prognosis of NMO is much worse, as the mortality rate is high and many become severely disabled.
The patient has recurring attacks of severe symptoms which become progressively worse and worse. The attacks remit over weeks/months, but usually with significant sequalae.
The symptoms of optic neuritis may be unilateral or bilateral and can be impaired vision with or without retrobulbar pain. The symptoms of transverse myelitis are bilateral and may be symmetric paraplaegia, sensory loss, and bladder dysfunction.
The patient may also have area postrema syndrome, where they experience severe nausea and vomiting.
Diagnosis and evaluation
80% of patients have anti-AQP4 antibodies in the serum. Some who are AQP4 negative have anti-MOG antibodies instead. MRI shows transverse inflammation and demyelination of the spinal cord which spans 3 or more segments. CSF should also be performed to rule out MS. The CSF in NMO is unremarkable. Unlike in MS, the MRI shows no lesions in the brain itself.
Like for MS, there are three sides to treatment, acute treatment, disease-modifying treatment, and symptomatic treatment.
Acute treatment is usually glucocorticoids ± plasma exchange. Disease-modifying treatment is usually rituximab or other antibodies, as well as immunosuppressants like azathioprine are used.