What Are MEG Brain Scans? - Stefan Rampp, University of Erlangen-Nürnberg, Germany
Magnetoencephalographies - or MEGs - are brain scans with a very high sensitivity and are a distinct complement to EEG and MRI scans in preparation for epilepsy surgery. Hear all about them now from the expert in biosignal analysis: Stefan Rampp.
Reported by Torie Robinson | Edited and produced by Pete Allen
Podcast:
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Torie
Thank you for joining us today, Stefan. It's brilliant to have you here after seeing you at the most wonderful conference earlier this year. Could you tell everyone about yourself, please, what you do?Stefan
Sure. So, first of all, thank you very much for the invitation. So, my name is Stefan Rampp. I work at the University Hospital in Erlangen, which is in the south-eastern part of Germany, so roughly about one and a half hours north of Munich, and I work at the Department of Neurosurgery and Department of Neuroradiology in Erlangen. And I specifically specialise in MEG, that is magnetoencephalography, which we use a lot for research, but specifically also clinically for pre-surgical evaluation for epilepsy surgery.Torie
Very exciting stuff. And what led you to work specifically in this field?Stefan
So that, I mean, that has quite a bit of a story! So, I started working with MEG quite a number of years ago because I encountered it during going to medical school to studying medicine and working on my thesis and this is when I got into contact with the former head of the Epilepsy Centre, Hermann Stefan, and he also introduced me to the technique; to magnetoencephalography. And so, for quite some time I was able to work at the epilepsy centre 50% and 50% for magneto, on MEG, on magnetoencephalography. But over the years that kind of shifted a little bit. So, I'm more involved now with MEG and imaging than when I started out. So that has been quite some time now.Torie
And how do, can you tell us how MEGs differ from other more well-known types of brain scans such as EEGs, MRIs, etc?Stefan
Right. So, MEG is basically something like the younger sister of EEG, you could think of it. So, what it does is it records, it registers the tiny magnetic fields that are generated by brain activity. So, in that regard, it's a bit comparable to EEG; they actually have the same temporal time resolution: so within milliseconds. And usually, we also record like EEG and MEG at the same time. So, this gives you an idea how comparable they are. And the advantages of MEG is that we have a very high sensitivity, especially in the neocortex (so in the superficial areas of the brain), which means that in quite a number of cases, we see activity that EEG does not see; because while the activity is also in the EEG somewhere, it's just that the amplitude is so tiny that it just is buried in all of this background activity and all of this “noise”. And we use this to record epileptic activity, for example, in patients with epilepsy. And we're then able to calculate where this activity comes from. So, we end up with images that have these markings on there that tell you where the activity is coming from. So that could be seizures, for example (if you are lucky enough to record a seizure during those usually quite short recordings of like, roughly about an hour). Or, we can also look at so-called interictal activity (that is activity that appears between seizures); so just these tiny blips that are in there. And we can also then localise that and give the neurosurgeon, for example, an idea where the activity is really coming from/where the epileptic focus is. So, in that sense, it's way on the functional side and not really comparable to MRI, which is on the structural side, right? So, you see lesions on there [on the MRI], changes of the anatomy. That would be like the other end of that diagnostic spectrum.Torie
So, would you say then, having an MEG scan, would be significantly complimentary to both having EEG and MRI? It's kind of like a good threesome, if you like?Stefan
Well, of course, it's my job to say that!Torie
Are you on commission?!Stefan
Yes! But, in addition to that, so, the patients that we evaluate are usually patients with focal epilepsy, where epilepsy surgery is one of the options. So, where it's at least evaluated whether that is an option. So, what we usually do there is of course we do an MRI because if we know there is a lesion that also causes the seizures then it's much, much easier to decide on, like, the surgical strategy, right? Then, of course, EEG is also done, but what MEG adds is another, is an additional perspective, basically, especially for like a certain group of patients. So, if there are, like, large lesions, the issue is that sometimes you have this large lesion, but you don't necessarily know from which part the epilepsy actually comes from, and there might not be the option to resect all of it. Then MEG can help with that. Another group of patients that usually benefit from this type of investigations are patients that don't have a lesion on the MRI, right? So, when you don't really know where to operate or where to put invasive electrodes for further evaluation. And then also patients that had previous surgery – because, previous surgery changes the anatomy, obviously, right; there are, like, skull defects, for example. Obviously, there’s also, like, a bit of brain missing, and all of this influences, for example, the EEG, but not really so much the MEG. So, the MEG is basically able to look beyond that. And also in these patients, when you then do another MRI, you will, of course, see the previous surgery. You will see the resection volume. You might also see some scarification. But where in all of that is the remaining epileptic tissue, right? So, the MRI is not really able to tell you that. And for these patients, MEG is a very good additional investigation. Right, so obviously we don't do MEG in just every patient. We select the ones that we think would actually benefit most from that.Torie
And are they, so is it largely the people that you put forward for MEG, they're likely to have refractory epilepsy, so perhaps try two anti-seizure medications; those don't work or don't work sufficiently, you have then the EEG, MRI, and then if you don't, if that doesn't provide enough information to give you good insight to what the challenges might be, then they might have an MEG. Is that about right?Stefan
That's pretty much how it works in practice. And we also already have quite a good idea which patients would benefit most. So sometimes, we also, when patients come to our epilepsy centre and are being evaluated with video EEG monitoring, so to evaluate their seizures: record the seizures on video but also record simultaneous EEG this is usually already the time point when we recognise whether or not that patient would benefit from that. So, it's not something that we do late in many patients, but we already do it when we start thinking about epilepsy surgery.Torie
That's really exciting; to be able to see the brain from so many dimensions and then being able to make more educated decisions on what the next step might be. And I think we were talking about before we started recording how just by finding this information out, it doesn't mean you definitely have to have a surgery, for instance. It's just putting that information on a plate and saying this is what we have, and these are our potential options. Right?Stefan
Right. It’s just finding out what the options are, right. And then it's a discussion, of course, specifically with the patient: what option would be optimal, right? And also, I mean, sometimes you don't have, like, like the best options, right? Sometimes you only have suboptimal options. So, for example, when you have [an] epileptic focus that's near essential functional cortex. So, let's say visual areas, or areas that process language, then the issue is that the epilepsy or the lesion causing the epilepsy might have led to, like, reorganisation; so, the functional area’s moved a little bit, and you don't necessarily know whether you can actually do a resection in this area and whether or not that is related to a high risk of functional deficit. So, you might not be able to, like, talk anymore. You might not be able to see everything around you, because if you damage these areas, then there will be a deficit. And in these cases, what we can also do with the MEG is that we don't only look at epileptic activity, but we can also look at this “normal” function. So, look at like normal - what we call it “physiological activity”, and then also localise that, right. So, during the recordings, we might then just like show you these chess-like/chessboard-like figures, or we might let you speak a few words or just think about a few words or read a text, and then we can see what the brain does during that time and where it does that. And then we can basically show the neurosurgeons, well, “this point here: this is where the epilepsy is from, and this point here: this is the visual cortex. So cut this but leave that intact”. Right. And we can do that, like, before going to the OR and then having an educated discussion with the patient what the chances are to be seizure free after surgery versus having a functional deficit due to the specific location.Torie
And then you can, I guess, look into the, or put it on a plate, say to the person, okay, this was what the likelihood/potentially would be if we didn't go forward with surgery, like we're talking about drugs in the future, the impact on cognition, quality of life, but then equally look at the side, potential side effects, if they go forward for the surgery, how might that affect their quality of life and their cognitive function? And it's about weighing those things up.Stefan
Yeah, exactly. Although, I mean, these discussions are always a bit difficult. Because we're talking about like percentages and percentages are - I mean we discussed this also before starting the recording - percentages are just so hard to grasp! And if I tell you, well, “if we do this, there is, like, if we do the surgery, there is, like, a 15% risk of having a functional deficit. And there's, like, a 45% chance of becoming seizure free”; what are you going to do, right. So, it's, it's difficult. It's always going to be an individual decision. But then on the other hand, usually the chances to, to get an improvement are actually really, really good. And at that point where we already know that this type of epilepsy cannot be really treated effectively with anti-seizure medication, then we know that the chances for improvement are so much better than with medication. So, there are statistics that clearly show that if you tried these two or three anti-seizure medication substances and they don't work - because, I don't know, they don't work just because they have like side-effects, but they don't work because they are not able to control the seizures, then your chances to become seizure-free with an additional anti-seizure drug is like around 5% or something like that. Whereas with epilepsy surgery (if you're a candidate for that): your chances to become seizure-free are roughly like between 60, 70, 80% (depends a little bit on what the cause of epilepsy is). So that is, I mean, this is so much better, right? So, this is why you should have this discussion! If anti-seizure medication doesn't work anymore, then have this evaluation, right? And then decide!Torie
Exactly. And one, I think one can always rest assured that if the option of surgery is put forward to them, it's not going to be done so unless the potential benefits outweigh the potential risks, right? So, it's not like, oh, we're just going to plonk you in the theatre, go on and have a bit of your brain sliced out. It's not as simple as that. Hence the workup.Stefan
No, no, we don't do that! No. Yeah, absolutely! And I mean, that the workup to get to this point is quite extensive, because it's also so individual, right, because, I mean there are types of epilepsy but even in focal epilepsy, so candidates where you can actually achieve something during epilepsy surgery. So, each patient situation is so different, that you have to undergo this extensive diagnostic workup: you do MRI, you do video EEG recording for, like, quite a number of days. And, and that sometimes really, I clearly understand that feels like a chore, right? So, it's, it's probably not fun to do this (!) but I think it's really well worth it because your chances (if you're a candidate) are so much better than with anti-seizure medications at this point.Torie
I completely agree. This has been a wonderful conversation. Thank you so much. Something that is close to my heart as well and I think more people need to be aware of the potentials of surgery. Going forward or putting yourself forward for having all these tests doesn't mean you have to have a surgery. And also, you explained to us the value of a MEG machine because not all areas of a country or countries indeed actually have one. And yeah, it sounds a lot like they can really improve an understanding of an individual's quality. What would I call it? Take this bit out, Pete. Understanding of a person's, well, just brain activity as a whole, really, and what might be best for them.Stefan
Exactly.Torie
Thank you so much, Stefan. It’s been brilliant to have you.Stefan
Thank you for having me. -
Stefan Rampp studied medicine at the University Erlangen-Nürnberg, Germany, where he graduated in 2004. He completed his doctoral thesis in 2006. From 2004 to 2014, he worked at the Epilepsy Center, Department of Neurology, and at the Department of Neurosurgery, University Hospital Erlangen, Germany since 2015.
In 2006, he also joined the Department of Neurosurgery, University Hospital Halle (Saale), Germany. In May 2016, he completed his habilitation thesis in experimental neurosurgery. He is currently the chair of the MEG lab of the University Hospital Erlangen, Germany.
His research includes diverse topics, such as MEG, surface and invasive EEG, as well as MRI analysis and postprocessing for epileptic focus localization, functional mapping, and neurocognitive research. Further areas of interest are intraoperative monitoring, biosignal analysis, and software development.
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Twitter/X: stefan_doe
LinkedIn: stefan-rampp
ResearchGate: Stefan-Rampp
ILAE: stefan-rampp
Universitätsklinikum Erlangen: stefan-rampp
University of Erlangen-Nuremberg: epilepsieoperationen-erfolgreicher
Martin Luther University Halle-Wittenberg: uni-halle.de
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