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What causes symptoms of multiple sclerosis (MS)?

Multiple sclerosis (MS) symptoms are caused by loss of myelin, axons and nerve cells.

The brain in multiple sclerosis:
  • The immune system attacks the myelin covering the axons of nerve cells.
  • It destroys patches or sections of myelin, leaving behind bare axons.
Nerve signals fail to reach the intended target:
  • A nerve signal begins at the cell body of the nerve cell.
  • It moves down the axon but can't jump an area of myelin damage.
  • Unable to jump across the section of bare axon, the signal is blocked.
  • The signal fails to reach its intended target, resulting in symptoms.
MS symptoms depend on the affected nerve pathway:
  • For the nerve-sending signals from the eye to the brain, vision may be affected.
  • A nerve sending signals for motor function may result in weakness.
Myelin, axons and nerve cells are damaged in MS:
  • Damage is done directly to the axons by the immune attack on the myelin.
  • The axon may be unable to survive if enough myelin is lost.
  • Loss of axons leaves fewer of them to carry the signal to the intended targets.
  • It is unknown whether immune attacks with myelin damage are the only cause of loss of the nerve cell body.
  • Nerve cells are eventually lost in MS.
  • Symptoms reflect damage/loss of the nerve pathway (vision, motor, etc.).
Lost cells in a nerve pathway cause MS symptoms:
  • An affected nerve pathway serves a specific function (vision, motor, etc.).
  • Lost nerve cells decrease the number of nerve cells available to carry a signal.
  • There is a reduced likelihood that signals in an injured nerve pathway will get through.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.