What to Know About Clinically Isolated Multiple Sclerosis (MS)
Medically reviewed by Nicholas R. Metrus, MD
Clinically isolated multiple sclerosis, also known as clinically isolated syndrome (CIS), is the first time you have symptoms consistent with multiple sclerosis (MS). CIS differs from MS in that it may truly be an isolated event and one that never returns. For some, however, CIS may turn out to be the first sign of MS, a lifelong condition.
CIS is one of four types of multiple sclerosis. It serves as a diagnostic "placeholder" during which time your healthcare provider will do their best to determine whether you are at high or low risk of having MS. According to the National Multiple Sclerosis Society, only 63% of those who experience CIS will go on to receive an MS diagnosis.
This article describes the symptoms of CIS and the tests that are used to establish if you are at high or low risk of MS. It will also explain how CIS is treated and why.
What Are the Symptoms of CIS?
Multiple sclerosis is a lifelong disease that causes progressive damage to the central nervous system, including the brain, spinal cord, and optic nerves.
With MS, the immune system attacks the protective coating around nerves (called myelin), causing them to fire incorrectly. The immune assault also causes the formation of scar tissues (called plaques) that further disrupt the transmission of nerve signals.
The symptoms of CIS vary based on which part (or parts) of the central nervous system is affected. Many symptoms are unilateral (affecting only one side of the body).
Symptoms of CIS may include:
Weakness of your arm and/or leg, typically unilateral
Slurred speech
Blurry vision or double vision
Decreased vision, usually in one eye
Eye pain, especially when you move it
Trouble with balance or walking
Tingling, burning, or painful sensations on the face, arm, or leg, typically unilateral
Muscle spasms in the arm or leg
Loss of bowel or bladder control
How Long Do CIS Symptoms Last?
Symptoms of CIS can develop abruptly over the course of a few hours or progressively worsen over the course of a few weeks. Events typically last for several weeks and may linger for several months in some people.
Learn More: Early, Common, and Rare MS Symptoms
Causes and Risk Factors of CIS: Who Gets It and When?
Like MS, CIS is not contagious. The exact cause of these conditions is unclear, but genetics and environment (including germs like the Epstein-Barr virus) are thought to contribute. Even so, there is no single factor linked to the onset of MS or CIS.
While any person of any age can get CIS, there are certain groups that are at higher risk. Among them:
People assigned female at birth are between two and three times more likely to get CIS the those assigned male at birth.
Around 70% of people diagnosed with CIS are between the ages of 20 and 40 years. The average age is 30.
How CIS Is Diagnosed
CIS can be difficult to diagnose. It involves an evaluation of the signs and symptoms in combination with medical imaging and lab tests. There is no single test that can diagnose CIS.
With that said, you may need to undergo numerous tests to exclude other conditions with similar signs and symptoms.
Brain Imaging
Magnetic resonance imaging (MRI) is the main imaging tool used to diagnose CIS. It uses powerful magnetic and radio waves to produce highly detailed images of the brain and spinal cord.
MRIs often involve the use of a contrast dye delivered into a vein to better highlight abnormalities in brain and spinal tissues. it can detect areas of demyelination (myelin loss) and brain plaques.
Related: MRI Results in MS and CIS
Lumbar Puncture
A lumbar puncture, also known as a spinal tap, involves the extraction of fluid (called cerebrospinal fluid) from the spinal cord using a small, thin needle.
The fluid is sent to a lab and evaluated for signs of excessive inflammation. This can be done with a technology called electrophoresis that can detect specific immune proteins (called oligoclonal bands) that are characteristically elevated in people with CIS.
Differential Diagnosis
Because there is no single test able to diagnose CIS, all other possible causes need to be excluded in order to render an accurate diagnosis. This may involve numerous tests and procedures.
Among the conditions your healthcare provider will want to exclude are:
Learn More: How Multiple Sclerosis Is Diagnosed
Will My CIS Turn Into MS?
There is a roughly 2-in-3 chance that CIS eventually be diagnosed as MS. At the same time, there is a 1-in-3 chance that CIS will be a one-off event.
While there is no way to know for sure if a person with CIS will eventually be diagnosed with MS, there are several factors that increase the risk, including:
Being male
Being a younger age
Having oligoclonal bands
Having brain lesions
Brain lesions are especially revealing. Studies suggest that having brain lesions on MRI increases the risk of an MS diagnosis within several years by 60% to 80%. Having no brain lesion is associated with a 20% risk.
When Is MS Diagnosed?
If you have been diagnosed with CIS and have a second neurological event, that would meet the diagnostic criteria for MS.
Similarly, if an MRI reveals old lesions or scars in a different location in the central nervous system, you would also be diagnosed with MS.
Do I Need Treatment for CIS?
If you have severe symptoms of CIS, your healthcare provider may prescribe intravenous steroids for several days to reduce inflammation in the central nervous system. Oral steroids, pain medications, and other treatments may also be used.
The decision to treat after CIS symptoms have resolved is made on a case-by-case basis. Although CIS may never officially "become" MS, treatment can help delay or prevent a second episode in some people.
Generally speaking, continued preventive therapy would be recommended if both of the following have occurred:
You have had one event of MS-like symptoms.
You have two or more brain lesions on an MRI.
If treatment is indicated, disease-modifying therapy (DMT) would be started using one of the following approved drugs:
Avonex (interferon beta-1a)
Betaseron (interferon beta-1b)
Extavia (interferon beta-1b)
Copaxone (glatiramer acetate)
Aubagio (teriflunomide)
Mayzent (siponimod)
All are given injections except for Aubagio and Mayzent which are taken as an oral tablet.
Whether or not treatment is prescribed, your healthcare provider will want to see you on a regular basis to assess whether there are any changes in your neurological function or any changes in your brain or spinal MRI.
Learn More: How Multiple Sclerosis Is Treated
Summary
Clinically isolated syndrome (CIS) is the first incident in which you have MS-like symptoms. While more than half of people with CIS will eventually be diagnosed with MS, there are many who will never have another episode.
CIS is diagnosed based on clinical signs and symptoms, MRI scans, lumbar puncture, and the exclusion of all other possible causes. Treatment with disease-modifying therapy (DMT) is recommended for individuals with CIS who have two or more brain lesions. Treatment may delay or altogether prevent a second event.
