Multiple Sclerosis: Understanding MS

What is Multiple Sclerosis?

Multiple Sclerosis (MS) is a condition that affects the brain and spinal cord. The body’s immune system attacks the protective covering of nerve fibers, which then affects the way the electrical messages flow within the brain, and from the brain to the rest of your body. It causes damage to the nerves, which causes scarring. In fact, ‘Sclerosis’ is a Greek word, referring to the scarring of the nerves. ‘Multiple’ refers to the many parts of the brain and spinal cord that can be affected.

The symptoms of MS vary depending on the degree of nerve damage and which nerves are affected. Some people may only have mild symptoms that come and go over time, while others may gradually notice problems with walking.

MS as disease has been known for centuries and for most of that time there were no effective treatments. However, in the last 20 years, very effective drugs that can change the course of the disease, known as disease modifying therapy (DMT), have become available. There is still no ‘cure’ for MS, and its cause is only partly understood.

Understanding Multiple Sclerosis

It is impossible to understand MS without first understanding a little about how the human nervous system and immune system normally work.

How does the nervous system work?

The nervous system has a central part and a peripheral part. The central part consists of the brain, spinal cord, and optic nerves. The peripheral part lies outside of this and includes the nerves that lead from the spinal cord into the muscles, and the nerves that bring back sensation from the skin into the spinal cord.

The main cells in the nervous system are called neurons. The body of the neurons lie in the brain and send a long nerve fiber stretching all the way into the spinal cord. This is called an axon. The axon is covered by a fatty, insulating substance called myelin.

Most parts of the brain have their own unique function. For example, when you want to move your right foot, the body of neurons in the motor cortex of the left side of the brain are stimulated. An electrical signal spreads down the axon, all the way down to the spinal cord. The signal is relayed to another neuron whose axon exits the spinal cord. These axons combine to make a nerve, which signals the muscle and makes it move.

Similarly, when you step on something sharp, nerve endings from the skin of your foot send electrical signals through the nerves to the spinal cord, and to the sensory area of the brain.

Nerves conduct electricity and all electrical systems require insulation to avoid short circuiting and for effective transmission of a current. Myelin is the insulation around the nerves that does this job.

Immune System

The immune system is the defense system of the body. It is meant to protect us from things like infection and cancer. The main ‘soldiers’ of the immune system are the white blood cells. Of the many kinds of white blood cells, the two primarily involved in causing autoimmune diseases are the T and B cells. These are the cells that release many different substances that cause inflammation.

Inflammation is the word used to describe the process and damage that the immune system causes in areas that it considers ‘foreign’. In an inflamed area, white blood cells accumulate and release substances that cause damage.

Autoimmune Disease

In an autoimmune disease, the body’s defense system mistakes the components of our own organs as foreign, causing inflammation. Virtually any organ in the body can be affected by an autoimmune disease. Examples include joints (rheumatoid arthritis), thyroid-hypothyroidism, ulcerative colitis and Crohn’s disease, skin-vitiligo, and psoriasis. The mechanisms of inflammation are surprisingly similar in many autoimmune diseases and therefore the medicines used to treat them are often similar. Only the substance that triggers the immune system varies. The tendency for autoimmunity can lead to more than one autoimmune disease being present in the same person. Because there are genetic factors involved in autoimmune diseases, they can occur in more than one person in the same family.

MS is the most common autoimmune disease that affects the central nervous system, affecting the brain, optic nerves, and spinal cord. We are not sure which substances in the central nervous system trigger the immune response, but myelin, the protein covering the nerves, is definitely one.

Learn more about the symptoms, causes and risk factors for multiple sclerosis