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What is Clinically Isolated Syndrome?

Have you ever heard the term “Benign MS”? It is a term referring to what appears to be a single Multiple Sclerosis attack followed by a complete absence of what is considered a chronic disease. Sounds pretty nice when compared to the MS that most of us have grown to know, doesn’t it? Just one exacerbation (occurrence of new neurological symptoms) and that’s it; no lingering symptoms, no repeat attacks (flare ups), and no need for treatment. Of course, everyone has a slightly different definition of what “Benign MS” actually is. Some may say that individuals with Benign MS actually do have a few mild symptoms that stick around and that after a long period of time, (meaning about a decade according to some) these individuals may develop a more progressive form of the disease. Some may say Benign MS can result in more than one attack with symptoms that either completely resolve or only partially so. Long-term disability? Some say yes and some say no.

Benign MS

So why is there no concrete answer as to what Benign Multiple Sclerosis really is? Well, I have attended several speeches by my previous neurologist who addressed this very question. He always found it amusing when people talked about “Benign MS” because as he said, “There is no such thing as Benign MS”. But if you look at these patients something is definitely going on; they are not crazy! So what is it? He would go on to explain that the proper term for this “phenomena” is called Clinically Isolated Syndrome (CIS).

A single flare up

OK, so then what is CIS? Clinically Isolated Syndrome basically refers to a single (what people in the MS community would call) “flare up”. A patient with CIS experiences a single neurological episode of demyelination/inflammation in the Central Nervous System (CNS) that results in neurological symptoms (such as weakness or optic neuritis) that last at least 24 hours. This episode does not appear to be caused by infection and therefore is considered to be an autoimmune attack (where the body’s immune system attacks it’s own body; specifically the CNS) which is exactly what Multiple Sclerosis is; an autoimmune disease. So CIS pretty much means, something is definitely going on and it might be MS but we can’t be certain yet.

Criteria for MS diagnosis

The reason they can’t be certain is that a patient with CIS does not satisfy the criteria for an MS diagnosis; most commonly the CIS patient has one or even no visible lesions. The “McDonald Criteria” for diagnosing MS (which was updated in 2010) requires a patient to have lesions in at least 2 or more areas of the CNS, the patient must have experienced at least 2 attacks separated by 30 days, and that other possible diagnoses have been ruled out (since many diseases such as Lyme disease closely mimic MS). Of course in some cases MS can be diagnosed before fulfilling this criteria based on certain clinical presentations or test results; one example could be the presence of a high number of Oligoclonal Bands in the Cerebral Spinal fluid (CSF) which is extracted by performing a spinal tap/lumbar puncture. An early diagnosis is usually (or should be I should say) done at a knowledgeable neurologists’ discretion.

So with that said, the symptoms that appear in this single attack may or may not appear as lesions on the brain (seen as white spots on the brain with an MRI) but alone are not enough to fulfill the MS diagnosis criteria. The symptoms of this single attack usually completely (or at least partially) resolve themselves which is where the term “benign MS” was apparently coined.

Clinically Definite MS

But when I first started talking about Benign MS at the beginning of this article I noted that some people would say it could in fact result in more than one attack. If someone who has been diagnosed with Clinically Isolated Syndrome goes on to experience a second attack their diagnosis gets “upgraded” to Clinically Definite Multiple Sclerosis (CDMS) which pretty much means, “you definitely have MS”. According to the National MS Society, patients with CIS who do present with brain lesions consistent with those of MS have a 60-80% chance of developing CDMS and CIS patients without these lesions have about a 20% chance of developing CDMS.

Obviously, if your risk is higher for developing MS, you should start an MS treatment as soon as you can. This can delay the conversion of CIS to CDMS but more importantly it will reduce your long term disability if it turns out you actually do have Multiple Sclerosis. So really, the term “Benign MS” is just an improper reference to Clinically Isolated Syndrome. CIS has a much more definite definition and is a medically accepted term that can actually be linked to research. So if you or someone you know has gone on to think (or currently is thinking) that you have (or may have) “Benign MS”, it’s actually called “Clinically Isolated Syndrome”. You can think of CIS as the “politically correct” name for Benign MS.1,2

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. Rae-Grant, Alexander D., Robert J. Fox, and Francois Bethoux. Multiple Sclerosis and Related Disorders. Demos Medical, 2013. 50-56. Print.
  2. "Clinically Isolated Syndrome (CIS)." National Multiple Sclerosis Society. Web. 15 Aug. 2014. .


  • itasara
    5 years ago

    Although I have a dx of RRMS, I have had one big symptom of transverse myelitis which led to my diagnosis. The reason I had a brainscan after the spinal scan was because I have a daughter with MS and she had TM 3 years before (only she was 20 and I was 57.) Otherwise the brain scan may not have been recommended, although I had two spinal lesions which is more suspect than those who might have one. Until that point I can’t say I had any symptoms that would have had me go to a doctor. But looking back at my life now, I had little things happen a maybe with in a year before like the infrequent “ms hug” which I and my internest thought was muscular cramps. So my brain scan had typical ms lesions, and I went on medication. Since my diagnosis 9 year ago, I can’t say I have had any particular “for sure” symptoms. Little things bother me which are probably related, but then these things happen with other non MS patients as “senior” citizens. So do I feel disabled or have symptoms that other MS patients describe? Not really. Is my MS “benign?” Probably not. I probaby had MS a lot longer than I ever thought so maybe it was benign for a long time. I thought I was leading a pretty “normal” life until my diagnosis and had not had a reason to see a doctor.

  • Matt Allen G author
    5 years ago

    Well, the thing is, you may feel like your experiancing no symptoms at all which is good but that doesnt mean you have no lesion activity in the brain. Plus if your on medication the GOAL is no symptoms. People who claim to have “”benighn”” ms are usually not on medication, at which point, the correct term for what they have is CIS.

  • David
    5 years ago

    No lingering effects my foot! I had one attack in 1998 and I still live with significant right-side deficits. Foot drop, weak right leg, tight right arm and inability to touch type with right hand. I may have had no known relapses, but one attack was enough.

  • Matt Allen G author
    5 years ago

    That is all it takes, ONE, just one… Not everything heals unfortunately…

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