Clinically Isolated Syndrome and MS


Learn about CIS and how it’s different from multiple sclerosis

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

What is CIS?

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

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
  • 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

What’s the difference between CIS and MS?

Based on the symptoms alone, CIS and MS may appear to be the same thing. But CIS is not considered a type of MS. It’s important to know that:

  • People with CIS have had a single incident of MS-like symptoms. Their magnetic resonance imaging (MRI) scan may reveal damage only to the area involving current symptoms
  • People with MS have had more than one incident of MS-like symptoms. Their MRI may reveal multiple areas of damage

Remember, early detection and treatment of relapsing MS is important. It may allow you to slow physical disability progression, reduce relapses, or reduce brain lesions. If you have any questions about the difference between MS and CIS, be sure to talk to your doctor.