What Triggers NMO?

Neuromyelitis optica (NMO) or Devic’s disease is a rare, autoimmune disease of the central nervous system (CNS). It primarily affects the myelin sheath that insulates the CNS. It targets the spinal cord, optic nerves, and brainstem. Damage to the optic nerves produces swelling and inflammation that cause pain and vision damage. Damage to the spinal cord causes weakness or paralysis in the legs or arms, loss of sensation, and problems with the bladder and bowel function. Moreover, damage to the brainstem can lead to prolonged hiccoughs, nausea, vomiting, vertigo, or respiratory failure.

NMO is a relapsing-remitting disease, and during a relapse, new damage to the optic nerves and/or spinal cord can cause additional disability.

Unlike multiple sclerosis (MS), NMO isn’t a progressive disease. Hence, preventing relapse is crucial to prevent further disabilities.

There are two types of NMO:

1. Relapsing form: It is the most common type of NMO and mainly affects women. It has periodic flare-ups with some respite in between.
2. Monophasic form: It involves a single attack that lasts for 1-2 months. Both men and women are equally affected by this form.

In most cases, neuromyelitis optica (NMO) is caused by the abnormal antibodies (proteins) binding to the protein gates called aquaporin-4 (AQP4) in the optic nerves and spinal cord. Aquaporins are proteins that transport water across the cell membranes. The binding of the aquaporin-4 antibody triggers other constituents of the immune system, causing inflammation and damage to these cells. Further, the brain and spinal cord lose the myelin sheath that insulates the central nervous system (CNS).

The symptoms of neuromyelitis optica (NMO) are mainly because of inflammation of the optic nerves (optic neuritis) and spinal cord (transverse myelitis). The most common symptoms include:

• Loss or blurring of vision in one or both the eyes
• Loss of color vision
• Eye pain
• Weakness
• Numbness (no sensation)
• Paralysis (loss of function)
• Loss of bowel or bladder control
• Retention of urine or difficulty emptying the bladder
• Spasticity (increased tone or stiffness in the extremities)
• Shooting pain or tingling in the neck, back, or abdomen
• Uncontrollable nausea and vomiting
• Uncontrollable hiccoughs
• Fatigue
• Confusion, seizures, or coma can occur in children

In the early course of the disease, the symptoms of NMO are challenging to differentiate from those of multiple sclerosis (MS) because both may cause optic neuritis and transverse myelitis. However, optic neuritis and myelitis are severe in NMO compared with those in MS.

Physicians may use the following tests to diagnose neuromyelitis optica (NMO):

• Neurological examination to examine movement, muscle strength, coordination, sensation, memory, and thinking functions
• Magnetic resonance imaging of the brain and spinal cord
• Blood test or lumbar puncture to screen for antibodies

Neuromyelitis optica (NMO) is incurable; however, physicians may prescribe medications to avoid relapse and relieve symptoms. The standard care for an initial attack includes:

• Intravenous high-dose methylprednisolone
• Plasma exchange: In this procedure, the physician removes the blood from the body through a needle and tubing; they separate the plasma from the blood cells and replace it with an artificial plasma substitute.

Medications used to treat NMO include:

• Eculizumab
• Inebilizumab
• Satralizumab