Multiple Sclerosis Development: What is Clinically Isolated Syndrome (CIS)?
1. What is Clinically Isolated Syndrome?
Clinically isolated syndrome (CIS) may or may not be a sign of multiple sclerosis. The term refers to the first episode of neurologic symptoms experienced by a patient. It usually lasts at least 24 hours and it is related to an inflammation or loss of the myelin lining of the nerve cells (called demyelination) in the central nervous system. A monofocal episode of clinically isolated syndrome occurs when the patient experiences only one sign or symptom, which is caused by a single lesion.
In comparison, a multifocal episode of clinically isolated syndrome refers to when a patient experiences more than one sign or symptom due to lesions in more than one location. These symptoms may include an attack of optic neuritis accompanied by numbness or tingling in the legs. The National Multiple Sclerosis Society also explains that these episodes are usually not related to fever or infection, and patients often experience a full or partial recovery after it.