Asking a Canadian Neurologist Whether Preventative Whole Body MRIs are Worth It
All about whole body preventative MRIs from a Canadian Toronto based Neurologist. July 29, 2024.
Prefix Health: Dr, if one of your patients said that they heard about preventative whole body MRI, what would be the first thing that goes through your mind as to whether or not they should do it?
Dr: From a safety standpoint, it’s very safe, assuming there are no contra-indications such as having certain metal lodged in your body.
From a affordability standpoint, that’s usually the first question. Is something that you can afford? If you can afford it, then I don’t see a downside to it. There is a lot of information from the report that’s going to be good information, such as to know what a baseline looks like, even if you expect nothing to be wrong.
It’s not bad to have a baseline of something, which because imaging is usually only ordered reactively. So, when imaging is exclusively ordered reactively, then baseline imaging exists only because people had symptoms for which the imaging ended. Your preventative MRI might end up being negative, but that becomes the baseline.
My next question would be, what’s the purpose of why you want to get this? A lot of people think they’re going to see something that they can’t predict yet but we aren’t at that stage yet for predicting. A lot of them are hoping to catch the needle in the haystack. But for those who say, “I just want information about my body” then if affordability is there and safety is there, it’s okay to obtain the baseline.
I deal mostly with the brain and the nervous system, where it’s always helpful to have a baseline on file.
Prefix Health:
What would be your immediate concerns? What would you be cynical about if you hear a preventative whole body MRI being done in one hour?
Doctor:
There’s two major concerns. One: does the imaging quality for each body region give you subsets like sufficient information to actually exclude or diagnose things? Correctly? There are many things for which we, in the brain at least, order additional sequences. and we hone in on certain areas, add certain sequences as its dynamic, or as a sequence.
There’s different ways of acquiring images. You have the T1, and the T2, and there’s variations of them with gadolinium; we have GRE, which is a way to pick up iron ore susceptibility weighted imaging which is for ferromagnetic molecules like iron – it will pick up old blood and things like that. So we can add those sequences. We can do diffusion weighted imaging, which is geared towards things like stroke. So there’s ways to tailor the imaging. Field of view can be changed to hone in for example, when you want to look at the pituitary, we need a dedicated image. There’s lots of ways you can look at the orbits around the eyes. There’s a lot of things for which thinner slices are required, especially the brainstem or areas with high density real estate so to speak.
What will you not be able to see on an MRI?
Doctor:
ALS – People need to keep in mind that there’s many things that aren’t diagnosed by an MRI – for example, if you have ALS, nothing will be seen on MRI.
Headache – Many headache disorders don’t produce an MRI change. You can have very subtle things for which a specific type of MRI needs to be done for which a routine MRI might not pick it up. For example, let’s say that you had a small in the orbit of meningioma. A routine MRI might miss that.
Tiny brain tumours – Tiny brain tumors could be missed in certain areas. Just because like the field of view and the way it is, could be missed if it’s not, or you might get an inconclusive finding or something you need to bring the person back.
False positives?
Doctor: Then there’s the false positive; almost invariably, there will be some findings that are in the normal range as we age for which the description sounds very ominous to a person who’s not trained in MRI. And so the most common would be what we call white matter lesions.
As we age, we can accumulate very tiny white matter lesions, some of them are pathologic if there’s a certain amount or size of them. For example, if you have white matter lesions by definition, wow, okay. But as we age also, people who did things like smoking or high blood pressure, might have a couple of tiny ones, and they’re often reported by radiologists. People often panic when they see them on the report because they Google it and they’re gonna get a large differential – most of which the ‘bad news’ is highlighted.
Prefix Health: Okay – so false positives might happen with whole body MRI, not great. Field of vision is not the same as scanning a dedicated body part. There are some diseases that don’t show up on MRIs like ALS, headache or tiny brain tumours. What about MS?
Doctor:
Yes, if you had MS, you’d most likely pick it up on the preventative MRI.
It’s multiple lesions in multiple areas.
What about Dementia or Alzheimer’s?
Doctor: No, you won’t see anything for the most part. Most of these diseases, the most common being Alzheimer’s, you can get atrophy in some areas of the brain. Atrophy meaning shrinkage of one part of the brain relative to another.
A lot of atrophy is called qualitatively by radiologists, meaning that they’re not actually sitting there with an atlas of normal controls and being like, “I measured the thickness of this region of the cortex and it was, you know, three millimeters instead of, you know, 3.7 millimeters.” They’re not doing that. They’re they’re eyeballing it globally and looking at certain areas and saying, this is probably too small or too big. By let’s say, looking at a muscle on somebody and saying, a person is muscular versus thinner or larger in an area compared to the average person. They’re able to do that too for the brain tissue. There’s a little bit of what they call global so the whole brain has a bit of global atrophy. People panic when they see that. Sometimes it has no clear significance.
The hope is that these MRIs not only catch a needle in the haystack, but also relieve the public system to some extent. But they also have the potential for overloading the public system if, if what I would call extraneous findings or spurious findings are seen they will lead to referrals and that happens often.
So you think if everyone did a preventative whole body MRI, it would clog up the system?
Doctor: I wonder, if we actually got people booked back to back, if it would actually harm the public system. Inevitably, statistically, you’re going to find stuff that people will look into. Some of the stuff will come back as nothing.
We have to remember that MRIs and images are just tools. Some people see that MRIs are the be-all and end-all, but it’s not a litmus test for everything under the sun. It’s a tool to be added to being followed consistently by one physician.
The most important thing with any tool is that it’s taken in the context of all the other information you have, and we call clinical correlation should be correlated with the there. There are some obvious exceptions: if you have no symptoms from a small brain tumor, and you catch one, yes, you’ve caught a brain tumor that’s, you know, de facto information that’s not debatable. And you may have the potential to live longer because you’re heading it off, but that’s a very rare thing to catch. Compared to, you will definitely catch more false positives, Yes, it’s a fact.
The analogy would be like casting a net as a fisherman. If every time you throw your net out you harpoon a whale and you have 100% success rate, in the doctor world, that tells us you didn’t cast your net wide enough…meaning that your positive rates so high that you’re likely missing stuff because you only send the harpoon out or the net out to catch what you think is a real fish right in front of you in the water. You should be sending the net out. There should be some findings that turn out to be non-issues.
And so, if by definition, if you’re ordering, let’s say 1000 MRIs, the definition would be even if they’re preventative, that the vast majority of those are going to catch false positives.
What about false negatives? Where you think there’s nothing wrong with the patient based on the MRI but it turns out there is?
Doctor: False negatives are rare for MRIs, if MRIs are the tool used to actually detect the issue. Remember that headache is not detectable on MRI.
It’s a test that we considered highly sensitive, meaning that its picked up rate is very high because it’s something if it’s structural, that means it shouldn’t be seen. It should be visible to the eye.
With the exception being something that’s slowly degradative structural like, like gradual loss of brain tissue or something dementia, where you’re losing brain cells over a span of many, many years. The initial scan might be normal or show something nonspecific that doesn’t aid in the diagnosis. That’s the issue.
The imaging correlate of Alzheimer’s would be like early medial temporal lobe atrophy. What’s in the medial temporal lobe is the hippocampus, the memory center, if there’s selective medial temporal atrophy that’s a finding that you can see with early Alzheimer’s and in particular, the temporal parietal, selective temporal parietal atrophy over let’s say, global attribute or frontal lobe atrophy or occipital atrophy. You’re gonna say, okay, that’s an early imaging correlate and it’s in the diagnostic criteria of Alzheimer’s you can make what they say a likely diagnosis or probable, probable Alzheimer’s based on an MRI it’s possible with with the with the right clinical correlation. Okay, it’s possible, so interesting, but the flip side that you can rule it out with a normal MRI is not correct. It’s interesting.
What are the other most common issues that you deal with day to day? We talked about ALS, MS, Dementia, chronic headache. Anything else as it pertains to MRI?
Doctor: Headaches as the primary diagnosis, are not seen on MRI. However, headaches that are a symptom of a bigger issue, such as a brain tumour, would be associated with using the image.
What about epilepsy?
Doctor: MRIs are often normal in epilepsy. Many people don’t have a clear cause – it’s genetic or something interesting.
Stroke?
Doctor: Yes, you would see a stroke on MRI. as well as anything else whereby the definition of the disease would be defined by th MRI change to a large extent or by precise brain tissue damage.
How many patients do you see a year?
Doctor: If it’s new consults 10 a day. A busier day would be 20 a day. So as we make it an average of 15 times, let’s say five days, you’re seeing 70 plus 80 patients a week. Let’s say we see 4,000 patients a year in Neurology. I estimate that I order MRIs for 20% of patients because we deal with the spine in addition to the brain.
So, that means that a single Neurologist in Toronto is requesting 800 MRIs a year of just the brain and spine.
Doctor: Yeah. And so don’t forget some people get more than one MRI. That’s possible so may need an MRI of the brain and spine many follow up patients given MRIs, so 20% of my patient population would be a conservative estimate.
So if a patient came to you and said, and but they also said, Hey, I have this baseline MRI from like three years ago. Would that mean anything or would it be irrelevant?
Doctor: Always helpful. Always helpful. If it’s actually available for review? Yes. I’ll give you an example. You might see a slightly enlarged pituitary gland, but it’s not a tumor of the pituitary. And if we had a baseline it was the same five years ago, we know that’s not a cause for concern, because most tumors will grow year to year. The passage of time is always reassuring in Neurology. Most things are progressive if untreated.
Is there anybody who absolutely should not ever book a preventative whole body MRI at all?
Doctor: If you have metal in your body, such as a metal fragment, shrapnel, etc, you most likely cannot. If you have other types of metal in the body, depending on what it is, it might be compatible with MRI. You need to talk to your doctor about what you have, such as a hip replacement, pacemaker, inner ear implant, etc.
But other than that, I wouldn’t say there’s anybody that shouldn’t get an MRI on a preventative basis.
So other than having metal stuck in your body, if you’re debating whether to buy a new purse, go on an international vacation, or get a preventative whole body MRI…?
Doctor: There’s huge peace of mind when it comes to knowing a baseline of your body. The main thing it probably boils down to for most people is cancer. Cancer is a top killer.
If you can catch an early tumor somewhere, you’re going to do yourself a great service.
So I’m biased, but if it’s between a purse and this, the MRI is the better bet because you’re spending on your health and you’re getting huge peace of mind.
But please remember that MRI is not perfect, and it’s not for everyone. MRIs are far from perfect. Even for many early findings, they can be missed on MRI. The other thing with MRI is everything is subject to human error, because it’s read by a person. The person reading the image is excellent, especially if they’re trained in Canada…they’re exceptional, but it’s still possible to miss something small. That could be the earliest stages of something which is what you’re trying to catch. Between the earliest earliest stage of something and the point that it declares itself, let’s say pancreatic cancer or colon cancer, there’s there’s a no man’s land where something could be, it’s larger, but it could could have been on your MRI could have been missed, but it was just too vague to be detected.
Don’t rest on your laurels. If you get a preventative MRI that’s normal but you smoke and have a family history of cancer, that doesn’t mean “you’re good” – you still need to have a regular doctor who follows you and you must use all the tools available to you: healthy diet, exercise, reducing stress, and so on.
How often should someone get a preventative whole body MRI? Every other year? Annually?
Doctor: It’s amazing how things can change in as little as three months. We’ve seen people who had an MRI, let’s say for a headache a year prior and then in the next year had new symptoms: a seizure, or something…might have had a brain tumor that wasn’t on the prior MRI. And they developed that in that time. It definitely happened in that time. If you have a new symptom, don’t ignore it. Go seek help.
