Clinically Isolated Syndrome (CIS)
Clinically isolated syndrome (CIS) refers to a first episode of neurologic symptoms caused by inflammation and demyelination in the central nervous system. Symptoms of CIS vary from person to person but commonly include:
- Vision problems (optic neuritis)
- Loss of sensation in the face
- Weakness in the arms and legs, with one side of the body affected more than the other
- Loss of control of bodily movements (ataxia)
- Bladder problems
To meet the definition of CIS, the episode must last at least 24 hours. Though an episode like this is typical of MS, not all people who have CIS go on to develop MS.
A person with CIS has a high likelihood of a second episode of neurologic symptoms and a diagnosis of relapsing-remitting MS
if an MRI (magnetic resonance imaging
) shows brain lesions that are similar to those seen in MS. Without those lesions, the likelihood of an MS diagnosis
is much lower.
According to the 2017 diagnostic criteria for MS
, a person with CIS may be diagnosed with MS if a brain MRI shows:
- Specific signs of an earlier episode of damage in a different location and
- Active inflammation in a region other than the one causing the current symptoms
As MRI technology improves, diagnosing MS will be quicker and easier. In the meantime, people with CIS who are considered at high risk for developing MS may be treated with a disease-modifying therapy with approval for that purpose from the U.S. Food and Drug Administration (FDA). Studies show that early treatment of CIS delays the onset of MS.