Glossary of Terms

Autoimmune disease: Occurs when the immune system cannot tell the difference between healthy cells and invaders like viruses, fungi, or bacteria. Because it cannot tell the difference, the body begins to attack and damage healthy cells.1

Antibody: Chemicals the immune system makes to kill germs.2

AQP4: This stands for aquaporin-4, a protein found on brain cells called astrocytes. The AQP4 protein helps control water balance in the brain.3

Aquaporin-4 antibodies: These antibodies, also called anti-AQP4, AQP4-IgG, and NMO-IgG, target and bind to AQP4. This leads to inflammation and symptoms of NMO.3,4

Area postrema syndrome (APS): The area postrema is located in the brainstem. Damage or inflammation to this area leads to episodic or constant nausea, vomiting, and/or hiccups. APS may occur with NMO.4,5

Astrocyte: A type of brain and spinal cord cell that does not conduct electrical impulses.6

Biologics: Biologics are drugs made from living cells. These cells can come from parts of the blood, proteins, viruses, or tissue. This process turns the cells into drugs that can treat diseases like NMO.7

Blood-brain barrier: The blood-brain barrier is the layer that divides the blood and brain. This layer has several jobs. It protects the brain from substances in the blood that could injure it (“foreign” substances). It also allows some healthy substances to reach the brain and maintains a constant environment for the brain.8

Bulbar palsy: A condition affecting specific nerves in the brain that leads to problems chewing or swallowing, decreased gag reflex, slurred speech, and/or weak jaw or facial muscles. Bulbar palsy may occur in NMO.9,10

Central nervous system (CNS): Consists of the brain and spinal cord and controls most functions of the mind and body.11

Comorbidity: Used to describe a condition that occurs at the same time as another condition. Comorbid illnesses can interact in ways that make both worse. Morbidity should not be confused with mortality. Morbidity means disease or illness. Mortality means death.12

Demyelination: Nerve fibers in your brain, spinal cord, and eye have a protective coating called myelin. Damage to this layer is called demyelination. When this layer is damaged, nerve signals can slow or stop. This leads to brain and nerve problems. NMO is a demyelinating disease.4,13

Devic disease: Former name for NMO. Some may still refer to NMO with this name.14

Myelin oligodendrocyte glycoprotein (MOG): Protein on the outermost layer (myelin) of the nerves found in the brain, spinal cord, and eyes (optic nerves). Also called MOG-IgG.15

MOG antibody NMO (MOG-IgG NMO): A subtype of NMO, this autoimmune disease affects the CNS. MOG antibody (MOG-IgG) NMO has similar symptoms to those of AQP4 (AQP4-IgG) antibody NMO. However, symptoms develop differently and need to be treated differently from those of AQP4 (AQP4-IgG) antibody NMO. It is possible that MOG antibody (MOG-IgG) NMO and AQP4 antibody (AQP4-IgG) NMO will eventually be considered separate diseases, though this is debated.15-17

Monophasic: A single attack. This pattern of NMO occurs in only 5 to 10 percent of cases and is more common in children. Men and women are equally likely to get this pattern of disease.18,19

Neuroimmunologist: A doctor who specializes in immune disorders of the nervous system.20

Neurologist: A doctor with special training in diagnosing, treating, and managing brain and nervous system disorders.21

NMO: Neuromyelitis optica spectrum disorder (NMO) is a rare inflammatory disease of the central nervous system (eye nerves, spinal cord, and brain). NMO may also be called neuromyelitis optica or NMO.4,22

Off-label: Use of a drug approved by the U.S. Food and Drug Administration (FDA) in an unapproved way or dose. Off-label uses may be common in rare diseases like NMO, for which few drugs are approved and few studies have been performed.23

Optic neuritis: Inflammation of the bundle of nerve fibers in the eye. This condition is a symptom of NMO.24

Ophthalmologist: Eye doctors with advanced training in medicine and surgery. Some ophthalmologists specialize in a specific area of eye care.25

Recurrent or Relapsing: Refers to periodic NMO attacks with some time in between. This pattern of NMO occurs 90 to 95 percent of the time and is much more common in women than in men.18

Plasma exchange: Also called plasmapheresis, therapeutic plasma exchange (TPE), or PLEX. In NMO, plasma exchange removes harmful antibodies from the blood and replaces them with healthy plasma.26,27

Spasticity: Condition of stiff muscles that remain contracted and difficult to stretch. This affects movement, speech, and walking patterns. It is caused by damage to the area of the brain and spinal cord that is responsible for muscle movement.28

Spinal tap: Also known as a lumbar puncture (LP). During an LP, a needle is inserted between 2 bones in the lower back to remove a sample of fluid from around your spine (cerebrospinal fluid, or CSF).29

Transverse myelitis: Inflammation of a section of the spinal cord. This condition damages the protective coating over the nerve fibers of the spine (myelin). Symptoms vary but may include pain, abnormal sensation, and weakness. This condition is a symptom of NMO.30

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Written by: Katie Murphy │Last reviewed: September 2021