Clinically Isolated Syndrome: Risk and Progression

A person who has a single MS-like attack due to demyelination in the CNS is said to have clinically-isolated syndrome (CIS). To be diagnosed with definite MS, a person must have had more than one attack of MS-like symptoms lasting more than 24 hours and separated from a prior attack by at least 30 days (dissemination in time) and evidence of CNS demyelination in more than one location (dissemination in space).

The terms monofocal and multifocal are used to describe CIS that involves demyelination in one (monofocal) or more (multifocal) CNS locations. A person with multifocal CIS might experience multiple symptoms, such as weakness on one side of the body and optic neuritis, or numbness on the face and difficulty walking. These varied symptoms provide evidence of lesions or plaques in separate areas of the CNS. Multifocal CIS satisfies one of two primary diagnostic criteria for an MS diagnosis, fulfilling the dissemination in space requirement but not dissemination in time.

What is the risk that a person with CIS will develop MS?

A person with CIS may never develop MS. Or in an individual with CIS, it may take months or years for another episode to happen and a confirmed diagnosis of MS to be made. It can be challenging to determine a patient’s risk for having a second demyelinating event in the future which would satisfy the full diagnostic criteria for MS.

MRI is helpful in predicting which CIS patients are at high risk for developing MS. Studies have shown that at the time of CIS diagnosis, the presence of additional MS-like plaques or lesions, not associated with the current attack, increases the likelihood that a person with CIS may eventually develop MS.  If a person does not have MRI evidence of additional MS-like lesions, the risk for developing MS is lower. The increased risk for developing MS after a CIS attack returns to normal after about five years.

Risk of developing MS in patients with CIS depends on MRI results

MRI Shows…
Risk of second neurologic event
No evidence of MS-like brain lesions
Evidence of MS-like brain lesions

Is it possible to prevent a second exacerbation from occurring?

Studies have shown that early treatment with disease-modifying medications may decrease the risk, or delay the occurrence, of a second exacerbation. Results from these studies have led to FDA approval of several disease-modifying treatments to be used by people diagnosed with CIS.

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Written by: Jonathan Simmons | Last reviewed: May 2015.