Clinically Isolated Syndrome (CIS) - National Multiple Sclerosis Society

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Clinically Isolated Syndrome (CIS)

Learn what it means to have a CIS, how a CIS can evolve into MS, and what treatment options are available to delay an MS diagnosis.

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Clinically isolated syndrome (CIS) is one of the MS disease courses. CIS refers to a first episode of neurologic symptoms that lasts at least 24 hours and is caused by inflammation or demyelination (loss of the myelin that covers the nerve cells) in the central nervous system (CNS). 

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The Diagnostic Criteria for MS

In order to make a diagnosis of MS, the physician must:

  • Find evidence of damage in at least two separate areas of the central nervous system (CNS) AND
  • Find evidence that the damage occurred at least one month apart AND
  • Rule out all other possible diagnoses

Diagnosing MS

Diagnosing MS