Clinically isolated syndrome (CIS)

Learn more about CIS and how it may develop into MS

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You may have heard your healthcare provider talk about clinically isolated syndrome (CIS). People who are diagnosed with CIS may or may not go on to develop MS.

What is CIS?

CIS is the first occurrence of neurologic symptoms resulting from demyelination.

What is demyelination?

A protective material surrounds the nerve fibers in the central nervous system. This is known as the myelin sheath. Damage to the myelin sheath is called demyelination. This may disrupt nerve impulses that travel between cells in the brain or from the brain to the rest of the body.

A CIS episode can involve one or more symptoms:

  • Monofocal episodes involve one symptom. For example, damage to the optic nerve behind your eye may lead to short-term vision problems. This is known as optic neuritis. In some patients, it could be permanent
  • Multifocal episodes involve more than one symptom. It may be optic neuritis (problems with vision) combined with another symptom, such as weakness on one side

Does CIS always progress to MS?

CIS is a first event that lasts for at least 24 hours. Healthcare providers use a variety of methods to find out if it’s likely someone with CIS will develop MS. This includes magnetic resonance imaging (MRI), spinal taps, and other tests.

With an MRI scan, they’re looking for brain lesions similar to those found in people with MS.

  • High-risk: If lesions are detected, there’s about a 60% to 80% chance that person will develop MS
  • Low-risk: If lesions aren’t detected, there’s about a 20% chance of developing MS

Remember, early detection and treatment of CIS and relapsing MS are important. The right treatment may allow you to slow physical disability progression, reduce relapses, or reduce brain lesions. If you have any questions about CIS, be sure to talk to your healthcare provider.

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