Neuromyelitis optica is a condition that involves loss of the myelin sheath (demyelination) that surrounds the optic nerve and spinal cord. The condition is also referred to as Devic's disease / syndrome. This is a rare disorder that resembles multiple sclerosis. Some also consider it to be a variant of acute disseminated encephalomyelitis.
Neuromyelitis optica is an autoimmune disease. Studies have shown that a large proportion (70%) of people who suffer from the condition have aquaporin 4 (AQP4) antibodies in their blood. These antibodies target transmembrane protein channels that are responsible for transporting water into the brain cells. In cases where individuals do not have the AQP4 antibodies, the cause of neuromyelitis optica is unclear.
The simultaneous inflammation and demyelination of the spinal cord and optic nerve in this condition may give rise to the following symptoms:
- Decreased or blurred vision
- Loss of visual acuity
- Reduced color vision
- Loss of color vision
- Limb weakness
- Muscle contractions
- Reduced bladder and bowel control
- Increased sensitivity to touch and temperature
- Burning or numbing sensation below affected area of spine
- Difficulty swallowing
- Speech difficulties
According to the Mayo clinic, a diagnosis of neuromyelitis optica requires that a patient meets at least two absolute criteria in addition to two of three other criteria.
The absolute criteria include:
- The presence of optic neuritis
- The presence of acute myelitis.
Supportive criteria include:
- Brain MRI rules out multiple sclerosis
- Spinal cord MRI with contiguous T2-weighted signal abnormality across at least three vertebral segments
- The presence of antibodies to aquaporin 4
There are currently no cures for neuromyelitis optica and treatment is aimed at managing symptoms and attacks, as well as preventing relapses. Attacks of the condition are treated with corticosteroids to suppress the immune system. Patients who are non-responsive to this therapy are treated using plasmapheresis.