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Multiple sclerosis (MS) is a chronic, disabling disease of the central nervous system. The disease causes inflammation, destruction, and scarring of the nerve sheath (called myelin) that covers nerve fibers in the brain and spinal cord. There can also be damage to the underlying nerve itself (called the axon). As a result, electrical signals are slowed or blocked.

Nerve cells (neurons) showing normal and damaged myelin sheaths

nucleus image
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There are several types of MS:

  • Relapsing-remitting MS—Symptoms suddenly reappear every few months or years, last for a few weeks or months, and then go back into remission. Symptoms sometimes worsen with each occurrence.
  • Primary progressive MS—Symptoms gradually worsen after they first appear. Relapses and remissions usually do not occur.
  • Secondary progressive MS—After years of relapses and remissions, symptoms suddenly begin to progressively worsen.
  • Progressive relapsing MS—Symptoms gradually worsen after they first appear. One or more relapses may also occur.

Multiple Sclerosis

Copyright © Nucleus Medical Media, Inc.

A malfunction of the body's immune system seems to be the cause of MS, but exactly why that occurs is not known. Researchers are still working to understand autoimmune diseases, in which the immune system, which normally protects the body from infection and other disease, starts attacking the body. The following conditions may contribute to MS:

  • Viral or other infection
  • Genetic factors (heredity)
  • Environmental factors

According to the National Multiple Sclerosis Society, about 400,000 people in the US have multiple sclerosis.

References:

FAQs about MS. National Multiple Sclerosis Society website. Available at: http://nationalmssociety.org/. Accessed August 2, 2010.

Multiple sclerosis. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php. Updated July 13, 2011. Accessed August 8, 2011.

National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/.

Last reviewed September 2013 by Rimas Lukas, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.