Neuromyelitis Optica (NMO)
Neuromyelitis optica is a demyelinating disorder that affects only the eyes and spinal cord.
(See also Overview of Demyelinating Disorders.)
Neuromyelitis optica causes acute optic neuritis, sometimes bilateral, plus demyelination of the cervical or thoracic spinal cord. It was previously considered to be a variant of multiple sclerosis (MS) but is now recognized as a different disorder.
Symptoms include visual loss, muscle spasms, paraparesis or quadriparesis, and incontinence.
Diagnosis of neuromyelitis optica usually includes brain and spinal cord MRI and visual evoked potentials.
Neuromyelitis optica is distinguished from MS because it affects several contiguous spinal segments of the spinal cord, whereas MS typically affects a single segment. Also unlike in MS, cerebral white matter lesions are uncommon in neuromyelitis optica.
Blood tests to measure an IgG antibody specific for neuromyelitis optica (aquaporin-4 antibody [also known as NMO-IgG]) may be done to differentiate it from MS.
There is no cure. However, treatment can prevent, slow, or decrease the severity of exacerbations.
Methylprednisolone and azathioprine are often used together. Plasma exchange may help people who do not respond to corticosteroids.
Rituximab, an anti–B-cell antibody, reduces IgG production and appears to stabilize the disease.
Treatment of symptoms is similar to that for MS. Baclofen or tizanidine may relieve muscle spasms.