Clinically Isolated Syndrome (CIS)

What it is

Clinically isolated syndrome is a first episode of neurological symptoms that lasts at least 24 hours and looks a lot like MS. It might be optic neuritis, numbness, or weakness. Some people with CIS go on to develop MS, and some do not.

Why it matters for you

If you have been told you have CIS, it means doctors are watching closely but do not yet have enough evidence to call it MS. Knowing the term helps explain how your care team is interpreting the findings.

Questions to ask your doctor

• What type of MS do I have, and how confident are you in the diagnosis?
• Would a second opinion be reasonable? Can you recommend one?
• What is my likely prognosis over the next 5 to 10 years?
• Is MS going to shorten my life?
• What is my risk of eventually needing a wheelchair or mobility aid?

Related terms

Find MS treatment centers near you

MS care is specialized — the center you choose shapes access to DMTs, infusions, and clinical trials. Pick your state to see centers in your area.