Radiologically Isolated Syndrome and MS
Everyone who has been diagnosed with MS has had an MRI before, and in all likelihood you have had way more than one! They help clinicians diagnose and treat each person on a case-by-case basis. For most of us, we had our first MRI because we were having strange symptoms, which is how we learned that we had MS lesions.
Detecting MS lesions before a person has MS symptoms
However, there are cases where we see lesions on an MRI before a person has any MS symptoms. This is called “radiologically isolated syndrome” or RIS. Most often we incidentally find RIS on MRIs that have been done because a person has a recurring problem such as headaches or dizziness. A study recently published in the International Journal of MS Care followed people with RIS and looked at their risk for developing multiple sclerosis.
Radiologically isolated syndrome vs. clinically isolated syndrome
RIS means that there are MRI changes, but no physical signs or symptoms of MS. This is slightly different then clinically isolated syndrome (CIS). CIS is an episode of neurological symptoms that lasts longer than 24 hours and is associated with inflammation and demyelination. There may or may not be MRI changes with CIS, but someone with MRI changes is at a higher risk for developing MS. In order to be diagnosed with MS, the current McDonald criteria state that the person must have two attacks (dissemination in time), and two or more lesions (dissemination in space). Both RIS and CIS can be precursors of multiple sclerosis.
Studying the relationship between RIS and MS
In the study, Longitudinal Follow-up of a Cohort of Patients with Incidental Abnormal Magnetic Resonance Imaging Findings at Presentation and Their Risk of Developing Multiple Sclerosis, researchers followed 30 people who presented to an MS clinic for evaluation following an abnormal brain MRI.1 Most of the participants had an MRI because they were experiencing headaches, and the results incidentally suggested that they might have MS. None of the participants had any physical symptoms at their initial visit, so researchers were able to follow them and study the relationship between RIS and the development of MS.
You may already be asking yourself, "Why we would care at all about this?" and the truth is, it could potentially impact the way we treat and diagnose MS. Misdiagnosis of MS is common, although we have made great strides! We know that outcomes are better if we intervene early, and identifying high-risk individuals could make a big impact. RIS is not officially MS, but if we know an individual has RIS, then we can carefully monitor them and intervene quickly if MS develops.
How many people with RIS developed MS?
The study included 30 participants, 15 of which had MRIs that met the Barkhof MRI imaging criteria, meaning that the results were suggestive of MS. Out of those 15 people, 7 (47%) went on to eventually meet the McDonald criteria and were officially diagnosed with MS within four years.2 None of the people that had MRIs without any signs of MS developed the disease during the study. In summary, researchers found that if a person without symptoms (i.e. asymptomatic) presented to the clinic with a positive MRI, they had a 47% chance of developing MS. But, none of the people who were asymptomatic with negative MRI results went on to develop MS during their study. This could mean that RIS is an asymptomatic period that occurs before the development of CIS or MS. It would be even more interesting to figure out why the other 53% never went on to develop MS within the 5.5 years that the study was occurring. Other studies have suggested that doing a lumbar puncture in people with RIS can help further identify whether there is a high risk of developing MS.
There have been a few studies on RIS, but most of them have been small so we still don’t have enough data to set official practice guidelines. According to the studies, 15-50% of people with RIS will develop MS within 5 years, and 66% will show radiologic progression. Additionally, 33% will develop physical symptoms, such as cognitive dysfunction, following the detection of RIS.
How many people with CIS develop MS?
Similarly, people diagnosed with CIS have a 31-45% chance of developing MS in the future. Given that a person presenting with RIS or CIS may or may not develop MS, it can be tough to decide the best course of action. Having more data that identifies who is at the highest risk could be a great asset to clinicians. It could help us decide whether to watch and see, or if starting medications could help prevent damage and improve long-term outcomes. Studies with a larger group of participants would be helpful in finding more answers.
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