What is Multiple Sclerosis?

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Multiple sclerosis, or MS, is a disease of the central nervous system. Your central nervous system (CNS) includes your brain and spinal cord, which contains special kinds of cells called neurons that are designed to send signals throughout your body.1 These signals pass through nerve fibres called axons, which are protected by an insulating sheath composed of myelin. These signals are responsible for many functions, including balance, physical coordination, eyesight, and memory.2

MS is sometimes called an autoimmune disease. That's because in MS, the immune system mistakes the body's own tissue as "intruders," and turns against itself.3 These attacks damage the protective myelin coating around your axons, and can create patches of scar tissue called sclerosis, or lesions. In fact, the name multiple sclerosis actually means "many scars." 2

How MS affects the CNS

Normal healthy neuron

Nerve signals quickly pass down the axon with its protective myelin coat.

Damaged neuron

Myelin damage disrupts messages travelling along nerve fibres–messages may slow down, become distorted, short circuit or not get through at all–resulting in symptoms of MS.  These symptoms can vary depending upon where the interruptions take place. Sometimes these symptoms come and go, while other times they can last longer or even be permanent.2

1. Heesen C, Shäffler N, Kasper J, Mühlhauser I, Köpke S. Suspected multiple sclerosis: What to do? Evaluation of a patient information leaflet. Mult Scler. 2009;15:1103-1112.
2. What is Multiple Sclerosis? National Multiple Sclerosis Society Web site. http://www.nationalmssociety.org/about-multiple-sclerosis/what-we-know-about-ms/what-is-ms/index.aspx. Accessed on 11 February 2011.
3. A to Z of MS Causes of Multiple Sclerosis. MS Trust Web site. http://www.mstrust.org.uk/atoz/cause.jsp. Accessed on 11 February 2011.