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MS 101: The Who, What, When, and Why of MRIs

If you have MS then I’m sure that you are intimately familiar with MRI machines! MRIs are the single best way for your health care providers to track disease progression, and to evaluate if your medications are working well. In the past, if an MRI showed new lesions but there were not any new symptoms, we would take a “wait and see” approach. However, new evidence is telling us that we should treat the MS, even if no new symptoms are present.

Preventing damage from occurring

Dr. Vollmer of the Rocky Mountain MS Center says that allowing new lesions to accumulate and basing treatment only based on symptoms is like closing the barn door after the horse has bolted. Once enough damage occurs, the person will inevitably have a relapse, and once that happens there is nothing we can do to reverse that damage. Therefore, it makes sense that we would want to prevent damage from occurring in order to prevent a major event down the line.

Switching medications

Last year, I switched my medications because my spinal cord showed new lesions and atrophy. I didn’t have any new symptoms, but both my doctor and I felt that I was accumulating too much new damage. We decided to take a proactive approach and switched my medications so that I had the best chance at continuing to feel fine in the future. It can be a bit tricky to decide what to do when there is a discrepancy between symptoms and the results of an MRI but it is important to have MRIs done, even if we feel good.

Why do we get MRIs?

All of us know that we get MRIs periodically, but not many of us know how they work or what exactly they show. That got me thinking, this could make an excellent educational blog post! You are a brilliant group of people, and you know how much I love expanding your MS knowledge. I truly believe that knowledge is power, so today I want to take some time to explain how MRIs work, why they make such a ruckus, and what they tell us about MS.

How do MRIs work?

The human body is mainly made of water and fat (I know, how flattering). As most of you probably learned in grade school, water is made up of hydrogen and oxygen (H2O). An MRI scan focuses on all of the hydrogen atoms within the body. Normally they are spinning around in random directions like a spinning top, but when you put a big powerful magnet next to them, they snap to attention and align with the magnetic field. Next, pulses of radiofrequency are applied which knock the hydrogen out of alignment with the magnetic field. The radiofrequency is then shut off, and the hydrogen atoms snap back to attention once again. The pulsing of the radio frequency is what makes the loud noises, and the periods of silence occur when the pulse is shut off and the hydrogen atoms are realigning with the magnetic field. The movement of the hydrogen is sensed and recorded by the MRI machine, which allows the computer to assess how the liquid within our tissues behaves.

Stephanie mri

What does MS look like on an MRI?

The picture above is an MRI image of the brain. Air and bone appear dark because they have a low water content (but there are certain types of MRI scans where they appear bright), while things with a high water and/or fat content such as spinal fluid, blood, and brain tissue are brighter. Although bone is dark on MRI scans, the fatty bone marrow also appears white which is why you can see the outline of the skull. Demyelination increases the water content of the surrounding tissue, which is why lesions show up as bright white spots. Additionally, contrast dye lets us know if demyelination is new or old.

What are their limitations?

Images are captured in slices and a scan is made up of several slices put together, much like a loaf of bread. This lets health care providers look at a very detailed picture of all the structures as if they were picking up slices of a loaf of rye bread and inspecting its marbling. However, in the process of cutting slices, the MRI may miss some tissues because of gaps between the slices.

There are different resolutions, or strengths, of MRIs. We like the highest resolution possible because they have very minimal gaps between slices. It is important to consistently get MRIs on a high-resolution machine, otherwise, we may not know whether lesions are new or if they were just missed because a lower resolution MRI machine was used.

Comparing past and present MRIs

Being able to compare images from previous years is essential to making decisions about medications, so it can be very frustrating when previous MRIs are not high quality. During the ECTRIMS/ACTRIMS conference in Boston, leading experts were discussing the importance of using the standardized MRI protocol, so that all MS patients have the same type of images no matter where they are being treated. The Consortium of MS Centers has a standardized guideline available on their website.1-3

So, that’s probably more than you ever wanted to know about MRIs, but it’s sort of interesting I think! Any questions?

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. Wilner AN, Naismith, RT. Treating the MRI in Multiple Sclerosis Medscape Neurology. July 15, 2014. Available at:
  2. Wilner AN, Pelletier D. Standardizing MRI in Monitoring MS. Medscape Neurology; An Expert Interview With Daniel Pelletier, MD. September 24, 2014. Available at:
  3. MRI (magnetic resonance imaging) and MR angiography. Mayfield Clinic for Brain & Spine. Available at:


  • tluvrock
    5 years ago

    Could you please discuss the varying strengths of MRI machines? If I ask the provider what strength their machine is, will I get an answer that I can understand or use to compare against others?

  • Stephanie Buxhoeveden, RN, MSCN author
    5 years ago

    Absolutely! Tesla (abbreviated as ‘T’) is the unit of measurement for the strength of a magnetic field. The standard of care for brain imaging in MS patients is to use a 1.5T or 3T MRI machine. In studies the 3T machine has been shown to be faster, more sensitive, and better at seeing MS lesions because it has better image clarity then a 1.5T machine. However, high quality images can still be obtained with a 1.5T MRI if a 3T scanner is not available in your area.

  • MSwife
    5 years ago

    Ugh, so confused. We just had another MRI after a medication switch. As you stated, i always understood new lesions on the brain to be white on the MRI. Old, healed lesions were dark, hence the name ‘black holes’.

    While reviewing our images, the doc repeatedly pointed out 3 bright white lesions, stating those were his oldest and largest. He advised us ‘no change’, repeatedly. He did have images done both with and without contrast, if that matters.

    This should be good news, but my husband feels there are changes,both cognitively and physically…we were told, that’s just MS. What’s up with the bright white spots? Our Doc has given us false info before, the nurse catches his error.

  • itasara
    5 years ago

    I am rather conservative and I think my neuro is also. In 9 years since my dx, he has not felt it necessary to order an MRI. He said this year that probably in the future he’d recommend another MRI. There is research I read about technology that will be able to see what it in the grey matter, not sure that is ready for prime time yet. Since my MS it fairly benign and so far remains so that could be why I don’t have regular MRI’s and also as Sephanie indicated, there is no particular correlation between symptoms and lesions on MRI’s. Some people on one of my ms boards indicate they get an MRI every year. I’m not so sure I understand the reason for that except for monetary purposes that for some cost the patient and become income for the doctor and insurance company. I don’t of course know all the details, but I remember my daughter telling me her neuro in california tells her she needs a new MRI and I asky why? Nothing changed far as she indicates to me and she is not switiching medications.

  • Stephanie Buxhoeveden, RN, MSCN author
    5 years ago

    I understand how frustrating it is when you are experiencing symptoms that are getting worse, but your MRI is “unchanged”!

    It is common for there to be a paradox between what the MRI shows and what symptoms a person with MS has. MRI’s are not perfect, for instance they don’t show us the grey matter of the brain. More and more research is showing that MS affects the grey matter, and contributes to disease progression. It’s very important to use a combination of physical exam and MRI imaging when determining the best way to treat multiple sclerosis. Has your husband been offered a cognitive evaluation or physical therapy? There are a lot of great therapies to help with cognitive and physical symptoms.

    This is a great (albeit very technical) article about grey matter involvement in MS:

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