What is MS?

MS is short for multiple sclerosis, a disease that affects the central nervous system (CNS), which is comprised of the brain, spinal cord, and optic nerves.

Think of the CNS as the wiring in your house. In the same way that wires carry the electricity which powers the lights in your house, the CNS transmits nerve impulses or messages from the brain, throughout the body and back again. These nerve signals help us move our limbs and use our senses of sight and touch. Because MS attacks the CNS, it can greatly affect the way we interact with the world.

Is there a cure for MS?

Developing MS is not like catching a cold. MS is a lifelong, incurable disease which affects people in many different ways. MS is a serious chronic, progressive disease which can vary in intensity from mild to severely disabling. For some people, symptoms of MS pose only an inconvenience and do not get in the way of leading an active and productive life. For other people whose MS is more severe, symptoms can interfere with one’s ability to move, see, think, swallow, talk, or feel. Fortunately, there are a growing number of medical treatments and management approaches to affect the course of the disease and to lessen the impact of symptoms on activities of daily life.

Is MS an autoimmune disease?

Many experts believe that MS is an autoimmune disease. Other types of autoimmune diseases include rheumatoid arthritis, psoriasis, Crohn’s disease, Type 1 diabetes, and lupus. In each of these conditions, the body’s immune system mistakenly attacks its own tissue and organs. In fact, the word autoimmune combines the words auto, which means self, and immune to communicate the idea of the immune system attacking itself.

MS and the immune system

The purpose of our immune system is to help our bodies fight off foreign invasion of substances or organisms which pose a threat to our health. For example, our immune system helps fight off infections caused by bacteria or viruses, resulting in localized inflammation. Think of the redness and swelling you experience when you get a splinter in your finger. That’s your immune system fighting bacteria that may have entered your body with the splinter. When your immune system responds to such an invasion, it sends immune cells such as lymphocytes, plasma cells (white blood cells that produce antibodies), and macrophages to attack the intruder.

MS and the central nervous system

Normally, our immune system uses inflammation to protect itself and fight invasion by substances or organisms that are foreign to our bodies. However, in MS, inflammation produced by our immune system is directed against parts of our central nervous system (CNS)

The autoimmune response within the CNS may cause a break in the blood-brain barrier (BBB), which is the layer of cells surrounding blood vessels in the brain and spinal cord that normally keeps substances from passing from the blood stream into the CNS. Small breaks in the BBB allow inflammatory cells to enter the CNS, resulting in the inflammation that damages nerve cells in the brain or spinal cord.

In MS, inflammatory cells attack myelin which is the fatty substance that surrounds and protects nerve fibers (or neurons).  Myelin acts like a protective cover, similar to the plastic insulation that covers electrical wires. In neurons damaged by MS, parts of the myelin sheath (fatty covering) are missing.

Inflammation and demyelination

In addition to damaging myelin, inflammation caused by MS can also damage the cells that produce myelin called oligodendrocytes. The destruction of myelin and oligodendrocytes caused by MS is called demyelination, a word that means ‘loss of myelin.’ Demyelination causes plaques (also called lesions or scars) along the myelin covering. In fact, this is where the word sclerosis in multiple sclerosis comes from. It refers to the accumulation of hardened scar tissue at the site where damage to myelin has occurred. The word multiple indicates that this scar tissue occurs in many places.

Neurological impact

Many of the symptoms of MS involve neurologic function, a term that refers to the way our nerves or nervous system function. Common MS symptoms, including numbness, weakness, pain, imbalance, and vision problems, happen because the protective myelin coating which normally helps nerve impulses travel along the axon (part of the nerve) is damaged. The exposed axon is less able to transmit or conduct nerve impulses.  Exposed axons may become further damaged and cease to function at all

When nerve fibers are not able to work normally to transmit impulses through the body, it can result in a loss of neurologic function. Think again of the comparison between your CNS and the electrical wiring in your house. What would happen if the plastic covering on some of the wires in your house wore through and the wires actually broke? Your lights might not work as they should or your appliances might suddenly turn off. Something similar happens when MS interferes with the communication of nerves in your central nervous system.

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Written by: Jonathan Simmons | Last reviewed: May 2015.