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Clinically Isolated Syndrome

  • Symptoms of CIS may include:
    • Bladder and/or bowel issues
    • Dizziness
    • Fatigue
    • Numbness or tingling in the face, body, arms and legs
    • Spasticity
    • Vision impairment — including optic neuritis, blurred vision, poor contrast or color vision, and pain with eye movement
    • Walking difficulties
    • Weakness
    What symptoms you have depend on where the damage to the myelin occurred in the central nervous system. The attack may affect your:
    • Spinal cord: When the immune system attack damages the spinal cord, it results in either partial or complete transverse myelitis. CIS might come on very quickly, in just a few hours, or more slowly, taking a week or two. Your symptoms depend on which area of the spinal cord is affected. You may experience muscle weakness, abnormal sensations in the arms and legs, bladder and bowel problems, or L’hermitte’s sign — an electric shock sensation when you move your neck.
    • Optic nerve: Inflammation of the optic nerve results in optic neuritis. You may develop symptoms suddenly or over a period of hours to days. Symptoms include blurred vision, vision loss (usually in only one eye), pain behind the eye, decreased color vision or blind spots.
    • Brainstem: Symptoms of brainstem damage can include nausea, vomiting, double vision, dizziness, hearing loss and unsteady walking.

  • In diagnosing CIS, it is important to rule out other potential causes as some may require immediate intervention. The process of diagnosis includes:
    • A complete medical history, including information about the specific symptoms and duration of the current episode
    • Neurological examinations
    • Magnetic resonance imaging (MRI) to look for signs of inflammation and demyelination (lesions) in the central nervous system
    • Blood tests to identify or rule out other potential causes for the symptoms
    • A lumbar puncture (spinal tap) to examine the fluid that surrounds the brain and spinal cord for oligoclonal bands(a specific group of proteins) 

  • Like MS, CIS is not directly inherited, and it is not contagious. CIS is 2 to 3 times more common in women than men. Seventy percent of people diagnosed with CIS are between the ages of 20 and 40, with the average age being 30. However, people can develop CIS at older or younger ages.

  • Based upon clinical symptoms alone, CIS and MS may appear the same. In both, damage to the myelin sheath (demyelination) interferes with the way nerve impulses travel to and from the brain, resulting in neurologic symptoms.
    • A person with CIS, by definition, is experiencing the first episode of symptoms caused by inflammation and demyelination in the central nervous system. A person with MS has experienced more than one episode.
    • With CIS, an MRI may show damage only in the area responsible for the current symptoms. With MS, there may be multiple lesions on the MRI in different areas of the brain and spinal cord.

  • If you have experienced CIS, you may or may not develop MS. Your healthcare provider will do their best to determine the likelihood of this happening. There are 3 possible outcomes:
    • High risk of developing MS: If a provider sees brain lesions similar to those in MS on Magnetic resonance imaging (MRI), you have a 60%-80% chance of a second neurologic event and diagnosis of MS within several years.
    • Low risk of developing MS: If CIS is not accompanied by MRI-detected brain lesions, you have about a 20% chance of developing MS within several years.
    • Diagnosis of MS: If CIS is accompanied by MRI findings of old lesions or scars that confirm an earlier episode of damage in a different location in the central nervous system, then an MS diagnosis is confirmed. The presence of oligoclonal bands in a person’s cerebrospinal fluid can also help make the MS diagnosis.
    As MRI technology becomes more advanced, it is likely that doctors will be able to diagnose MS more quickly and fewer people will be diagnosed with CIS. A quicker diagnosis allows people to get treatment earlier and potentially slow their disease course.Only 63% of those who experience an episode of CIS go on to receive an MS diagnosis. It is impossible to predict who will and in what period of time. Many factors contribute to this — including some that have not been identified yet.

  • Researchers have recognized multiple variables and risk factors that play a role in the potential for CIS to progress to MS. These include:
    • Younger age of disease onset
    • Assigned male at birth
    • The number of MRI lesions
    • Oligoclonal bands in cerebrospinal fluid
    This list is not exhaustive. For more details, see a 2021 study about MS biomarkers. These characteristics do not apply to every person with CIS. Finally, there are a number of risk factors associated with MS, like vitamin D deficiency and smoking, that you can control. 

  • Treatment with a disease-modifying therapy (DMT) may delay or prevent a second neurologic episode and, therefore, the onset of MS. In addition, early treatment may minimize future disability caused by more inflammation and damage to nerve cells, which can sometimes occur without any noticeable symptoms. If you have CIS, discuss starting a DMT with your healthcare provider if both of these are true:
    1. You have had one event of MS-like symptoms and
    2. You have two or more brain lesions on an MRI scan
    You and your healthcare provider can consider your specific risks and benefits and decide whether or not you should start a DMT.

Support and Resources for CIS

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The National Multiple Sclerosis Society is proud to be a source of information on multiple sclerosis related topics. Unless otherwise indicated, the information provided is based on professional advice, published experience and expert opinion. However, the information does not constitute medical or legal advice. For specific medical advice, consult a qualified physician. For specific legal advice, consult a qualified attorney.