The optic neuritis of NMO causes pain in the eye and vision loss. Transverse myelitis causes weakness, numbness, and sometimes paralysis of the arms and legs, along with problems with sensation and loss of bladder and bowel control.

Patients may undergo magnetic resonance imaging (MRI) as part of the evaluation process. In patients with NMO, lesions in the spinal cord tend to appear longer than those seen in patients with multiple sclerosis (MS), often longer than three or more vertebral bodies of the spine.

The discovery of an antibody in the blood of individuals with NMO has provided doctors with a reliable biomarker to distinguish NMO from MS. The antibody, called NMO-IgG, is present in about 70 percent of patients with NMO and is not found in people with MS or other similar conditions.