An Overview of Clinically Isolated Multiple Sclerosis (MS)

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Clinically isolated multiple sclerosis is a neurological episode that produces the same symptoms and diagnostic test results as multiple sclerosis (MS). Clinically isolated MS is typically called clinically isolated syndrome (CIS). The main difference between CIS and MS is that CIS is diagnosed after you have only one event, while MS is a progressively worsening or recurring condition. CIS can be the first sign of MS, or it can be the first and last time you ever experience this type of episode

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The symptoms of CIS can occur abruptly over a few hours, or they may worsen over the course of a few weeks. They can occur at any age but tend to be more common during the ages between 20 and 40. They are similar to the symptoms MS, and you may experience just one symptom or several at a time. 

Symptoms of CIS can include:

  • Weakness of your arm and/or leg, usually on one side of the body 
  • Slurred speech
  • Blurry vision or double vision 
  • Optic neuritis—decreased vision, usually in one eye 
  • Pain of your eye, especially when you move it
  • Trouble with balance and/or walking 
  • Tingling, unusual sensations and/or pain of the face, arm, and/or leg, usually in only one side of the body
  • Brief muscle spasms of the arm or leg 
  • Decreased control of bowel or bladder 

With CIS, these symptoms can all begin at once or may start within a few days of each other. Generally, if you begin to experience one symptom before the others, your first symptom is likely to remain when the others appear.

It is not easy to predict when CIS will resolve, but it typically lasts for several weeks and may linger for a few months.


CIS is caused by decreased function of nerves in the brain, spine, and/or eyes (the optic nerves). The decreased nerve function is the result of a process called demyelination.


Demyelination is the loss of myelin around nerves. Myelin is a type of fat that coats and protects nerves, helping them function efficiently. When myelin is diminished, nerves can slow down to the point of dysfunction—which manifests with weakness, visual and sensory changes.

Autoimmune Inflammation 

Generally, it is believed that inflammation, which is a flood of the body’s immune cells, attacks the body’s own myelin, causing the demyelination of CIS. When the body attacks itself, this is described as an autoimmune process

CIS and MS are often described as inflammatory demyelination or autoimmune demyelination.

CIS and MS Causes 

CIS can be the first episode of MS, but it can occur even among people who will never get MS. There is some evidence that these conditions can potentially be triggered by an infection or by stress. However, there is not usually an obvious cause of MS or CIS. In fact, these conditions are largely believed to be idiopathic, which means that their cause is unknown.


If you experience the symptoms of CIS, you should definitely call your healthcare provider right away. You will need to be examined, and you may need some diagnostic tests, as well as medical treatment. Your medical team may also consider ruling out other conditions that can mimic CIS.

Your healthcare provider will likely talk to you in detail and ask you questions about your symptoms, their severity, and duration. You will need a physical examination, which can include a measure of your body temperature, an evaluation of your eyes and vision, muscle strength, sensation, reflexes, and your ability to communicate and walk. Based on the results of your history and physical examination, your healthcare provider may decide that you need additional testing. 

Diagnostic Tests

Several medical tests are often needed in the diagnostic evaluation of CIS. Your healthcare providers will often know whether your symptoms and signs correspond to a problem in your brain, spine, or optic nerve, but will need to verify whether demyelination is the cause. 

Brain imaging: brain or spine magnetic resonance imaging (MRI) is helpful in evaluating CIS. This test can often differentiate between a stroke, an infection, demyelination, inflammation, or a tumor—illnesses that all can produce similar signs and symptoms.

A demyelinating lesion may be described as a plaque or as an active inflammatory lesion when it is visualized on an imaging test. Your imaging tests may show that you have had demyelinating lesions in the past, even if you never had symptoms before.

The next step in your diagnosis and treatment often depends on what is seen in your brain or spine imaging. Another thing that your healthcare providers look for is whether the location of any demyelination matches up with your symptoms— which strongly suggests that the imaging findings correspond with your condition.

Sometimes, older demyelinating lesions can be seen on imaging tests, which would suggest that you have MS and not CIS.

Lumbar puncture (spinal tap): This is an interventional test that involves the removal of spinal fluid using a small, thin needle. After your skin is sterilized, the needle is placed in your lower back.

Either your healthcare provider or a radiologist will perform the procedure. It is not painful or dangerous, although it can be slightly uncomfortable. The procedure takes about 10 to 20 minutes, and your healthcare provider will want you to lie down and rest for at least an hour after the procedure is completed.

The spinal fluid is sent to a laboratory, and it can be examined for inflammatory cells, evidence of an infection, blood, cancer cells, and proteins. The results will give your medical team an idea about the cause of your signs and symptoms, and, along with your brain or spine imaging, can help with your diagnosis. 

Neurocognitive testing: While CIS is quite noticeable, some people who have MS or other neurological diseases can have mild or subtle symptoms for years.

If you or a close family member has noticed that you have memory, concentration, or mood problems, then you might need to have neurocognitive testing. These tests evaluate your thinking and problem-solving skills and can help identify whether your complaints correspond to the lesions seen on your brain imaging studies. 

Visual evoked potentials (VEPs): This is a non-invasive electrical study that measures vision. VEPs can help in the diagnosis of optic neuritis, which is inflammation or demyelination of the optic nerve that can occur with CIS or MS.

A VEP is a painless test involving superficial placement of electrodes on your scalp and measurements of the electrical activity that occurs when you look at visual stimuli.

Sometimes, optic neuritis is not identified on brain imaging tests, so VEPs can be helpful in identifying the cause of your vision loss. VEPs can show signs of optic neuritis even if you have not experienced eye pain or a substantial deficit in your vision.

Likelihood of CIS

The diagnosis of CIS is made if your medical team is convinced that your symptoms are caused by demyelination. Other conditions that can mimic CIS include an infection, an autoimmune disease (like lupus), a stroke, cancer, or a reaction to a medication.

If you are diagnosed with CIS, there is a chance that you could develop MS. This chance is higher if you have more than one lesion, if you have evidence of previous lesions, if you have had other symptoms of MS in the past (even if you didn’t seek medical attention for them), or if you have family members with MS.


Demyelinating disease is treated in two ways. Acute episodes are treated with intravenous (IV) steroids. During an acute attack, you might need other temporary symptomatic treatments. Your healthcare provider may also talk with you about long term management with disease modifying therapy (DMT) after your symptoms resolve.

You will likely have close follow up of your neurological abilities (such as walking, speaking, and vision) for several years after you recover from an episode of CIS. 

Acute Treatment

IV steroid treatment is often used for several consecutive days, and improvement may begin during treatment. But generally, symptoms do not resolve until several weeks after treatment is complete. If you have a course of high dose IV steroids, your healthcare provider may also prescribe a tapering dose of oral steroids afterward.

Severe episodes may be treated with plasmapheresis, a type of plasma exchange. This procedure filters your blood to decrease the autoimmune activity.

Plasma exchange is a slow and steady process that filtrates your blood through a machine and immediately returns the blood to your body through a blood vessel. The procedure can take several hours and you would need to remain attached to the machine with a small tube throughout the procedure.

Symptomatic treatments during an episode of CIS can include pain medication if you are experiencing discomfort of your arms, legs, or eye. Sometimes a splint can help in support if you have muscle weakness. An eye patch can relieve symptoms of double vision.

Disease Modifying Therapy

MS, which is a chronic disease, is also managed with DMT, which are medications used to prevent disease progression and relapses. There are over a dozen different DMTs approved for management of MS, and several are approved for CIS as well. Most neurologists tend to recommend treatment with a DMT for CIS patients considered to be at higher risk of developing MS.

The American Academy of Neurology (AAN) has created practice guidelines regarding treatment of CIS. You and your healthcare provider can use the guidelines to help you make a decision about treatment, but the bottom line is that some people opt for MS disease modifying therapy, while others do not. 

According to the AAN guidelines, you and your healthcare provider should discuss the benefits and risks of DMTs if you are diagnosed with CIS. Your healthcare provider can prescribe a DMT for you if you decide that you want therapy and are committed to taking it.

Some DMTs require giving yourself an injection, and all DMTs can have some side effects. 

DMTs approved for CIS include:

  • Avonex (interferon beta-1a)
  • Betaseron and Extavia (both interferon beta-1b)
  • Copaxone (glatiramer acetate)
  • Aubagio (teriflunomide)
  • Mayzent (siponimod)

These medications are all used as injections except for Aubagio and Mayzent, which are taken as an oral tablet.

Keep in mind that your healthcare provider may consider prescribing an "off label" DMT that is approved for MS, but isn’t necessarily FDA-approved for CIS if it seems like it would be a better fit for you.

If you don’t take a DMT, your healthcare provider may recommend repeated brain or spine imaging tests at least once a year for the first five years after your diagnosis. 

A Word From Verywell

CIS and MS are both caused by inflammatory demyelination. In general, your body renews myelin on a regular basis so you may regain some or all of your abilities as you recover from the episode.

If you have had CIS, no one can predict with certainty if you will eventually be diagnosed with MS. However, if you have had subtle symptoms for a few years or if you have one or more family members with MS, this makes it more likely that you will eventually be diagnosed with this chronic condition. However, you might never have another episode or additional symptoms even if you have these risk factors. 

The best thing to do if you have had CIS is to maintain a positive attitude and to learn about the symptoms of MS so that you can recognize them and get prompt treatment if you need to. Living a healthy lifestyle has not been proven to prevent or cure MS, but lifestyle habits—like managing stress and mood, staying physically fit and active, eating healthy—can lessen the impact of the disease if you are eventually diagnosed with it.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  • Cohen M, Brochet B, Clavelou P, et. al. Qualicis Study Group. Cognition and quality of life in clinically isolated syndrome patients starting a disease modifying therapy in the QUALICIS study may not predict treatment response at one year. J Neurol Sci. 2017 Nov 15;382:73-78. DOI: 10.1016/j.jns.2017.09.030.

  • Ehler J, Koball S, Sauer M, et al. Therapeutic plasma exchange in glucocorticosteroid-unresponsive patients with Clinically Isolated Syndrome. Ther Apher Dial. 2014 Oct;18(5):489-96. DOI: 10.1111/1744-9987.12176.

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.