Bob Underwood, MD (Host): Magnetoencephalography, or MEG, is advanced neuroimaging that maps brain activity for targeted epilepsy care. Children's Health Comprehensive Epilepsy Center uses MEG to greatly enhance epilepsy care in the pediatric patient population.

This is Pediatric Insights Advances and Innovations with Children's Health, where we explore the latest in pediatric care and research.

I'm your host, Dr. Bob Underwood, and today we'll discuss how MEG is being used at Children's Health to inform care for pediatric epilepsy. With us today is Dr. Afsaneh Talai, Pediatric Neurologist and Epileptologist at Children's Health and Assistant Professor at UT Southwestern. Dr. Talai, thank you for joining us today. This is going to be so interesting.

Afsaneh Talai, MD: Thank you for having me. I'm excited to be here. 

Host: So let's start with the basics. What is magnetoencephalography, or MEG, and how is it different from other tests for epilepsy? I mean, we're all familiar with EEGs, right?

Afsaneh Talai, MD: Definitely. Yeah, so MEG is a non-invasive neurophysiology study, similar to EEG, but a little bit different. We use it in the workup of drug resistant epilepsy. So, simply put, the MEG measures the magnetic field produced by the electrical activity of the brain. The best way to think of this is if you recall back to your physics class when we learned about the right hand rule, where your thumb moves in the direction of the current or the electrical activity of the brain in this situation. And the rest of your fingers curl around, producing the magnetic field.

That's what the MEG is measuring. And so, this differs from EEG, which measures the electrical activity itself that's produced by the brain. Both are essential, but both have limitations and advantages. One of the most important differences we think about is that electrical activity is affected by the permeability of the tissue, whereas the magnetic field is not. 

Meaning all the material between the brain that's producing this abnormal brain activity, so the brain tissue, the skull, and the scalp, affects electrical activity, but not the magnetic activity. So for this reason, the MEG can measure the activity unobscured, letting us look at that activity very accurately. What's even cooler is, the MEG uses magnetic source imaging to create a functional map of this abnormal brain activity. So the final output, or the MEG results that we produce is an MRI with little dots on it, that we call dipoles.

And these dipoles form a cluster, and that's what we're looking for. And this cluster is mapped onto a brain MRI, and then the epileptologist can use this information to pinpoint where we think the seizure activity is coming from, and then plan their next surgical steps for that patient.

Host: It is absolutely fascinating that we can get that detailed through this methodology. So how is it currently being used in terms of clinical care for pediatric patients with epilepsy?

Afsaneh Talai, MD: We're currently using the MEG to help us localize where we think the seizures are coming from. So this information is essential for helping us guide invasive EEG monitoring, what we call SEEG. It complements the other tests we perform for this process, but when children are undergoing the workup for possible epilepsy surgery, the MEG now helps us identify an area that we think the seizures are coming from, so then we can target our invasive EEG or our resection as best as possible. Again, what's unique is that the MEG is measuring something that no other test can measure and that's that magnetic field that the electrical activity is producing.

Host: So in addition to identifying the foci of the seizure, then it's also used for functional brain mapping, right?

Afsaneh Talai, MD: That's right. So it's really awesome that we can use the MEG not only for identifying where the seizures are coming from, but to help us localize what we call eloquent cortex. Or the parts of the brain that control important functions for our day to day life, such as movement, speech, and vision, to name a few.

So, when we're planning epilepsy surgery, we're wanting to identify not only where the seizures are coming from, but where are the essential parts of our brain that we can't absolutely lose. And we correlate these two areas to ensure that when we're giving a recommendation for a surgical intervention, our neurosurgeon doesn't go near the eloquent cortex, ideally, to avoid any deficits after the surgery.

So the MEG is helping us identify those essential areas, as well as identifying the essential areas where the seizures are coming from and making sure that we know where those places are and avoiding targeting the eloquent cortex.

Host: So based on the mapping you're able to do with MEG, you're able to preserve the critical functions like speech, motor control, things like that during a neurosurgical procedure.

Afsaneh Talai, MD: Exactly.

Host: That's just fascinating that we can do these things now, it really is. And so pediatric patients, they present unique challenges in epilepsy management. So what makes MEG particularly useful in this particular population and, how does it compare to other diagnostic tools in terms of comfort, safety, things like that with pediatric kids?

Afsaneh Talai, MD: Definitely the MEG is a very useful tool in our pediatric patient population. For instance, sometimes the MRI may be limited as pediatric brains haven't completely finished myelinating or developing. And so the MRIs might miss, you know, these subtle abnormalities. Well, the MEG is not really affected by that.

And so often we might use a technology like the MEG to help us identify an abnormality that the MRI may miss. Additionally, with the MRI, it's, it's a long procedure that requires a patient to not move at all. So sedation is often required for our younger patients.

In the MEG, there is some flexibility with that. And so we actually don't sedate our patients. So the risk of undergoing a MEG is a lot less. And, it imposes no risks to our patients, meaning there's no radiation, they don't need an IV, there's no other side effect that comes with the procedure. So, I think it's very palatable to families when you put it that way.

Now, it does require involvement and participation from the patient. So, our MEG team, specifically our technicians, are so great at working with the families and the physician ordering the tests to create a plan to help the child successfully complete this procedure. And we've been very successful. Most of our patients tolerate it very well and are able to get really good results from it.

Host: That is awesome in terms of being able to meet the patient where their capability is and their cooperation and, not be so intimidating, you know, taking care of kids is scary for the patient sometimes and to be able to do something like this where it's not as traumatic for them, I think is phenomenal.

Afsaneh Talai, MD: Definitely in our pediatric epilepsy population, they have a lot of developmental differences. And so being able to work with them and their families is important for us to be able to successfully complete our procedures such as the MEG.

Host: Yeah, that's awesome. So do you have any specific cases where MEG played a key role in diagnosing, treating a complex case? What were the outcomes?

Afsaneh Talai, MD: Oh, there's so many to choose from, but I'd have to say we have several patients who fit in a category that are very difficult to treat. So they have drug resistant focal epilepsy, but their MRIs are normal, meaning there's nothing on the MRI to tell us why they're having seizures. And this poses a challenge because when you want to do epilepsy surgery, you want to be able to tell your neurosurgeon and point maybe to the MRI and say, Hey, take this piece of the brain out or target the invasive EEG, the SEEG right there so that we can collect the information we need.

Well, when their MRIs are normal. That's difficult. And we have a lot of extra tests that help us and the seizure simulogy and the history the families provide are very helpful. But at the end of the day, you want something to point to and say, this is where I think the abnormality is.

And that's where the MEG comes in. So, in these few patients, who underwent a MEG, we identified a cluster, you know, those dots or dipoles that we have on the MRI. The cluster was identified on these patients, and then during our multidisciplinary epilepsy surgery conference, our neuroradiologist went back and looked at the MRI in that region of the cluster.

And sure enough, they identified a subtle abnormality, possibly what we call a dysplasia. And so then we were able to take it to the neurosurgeon and say, Hey, there's something subtle here. Can we target our SEEG electrodes right around this lesion and see if we have seizures coming from here? And sure enough, in these few patients, we captured seizures from here.

Then took them to surgery to remove that lesion, and now a few of them have had such great outcomes. And so, I tell these stories because the MEG was just so vital to their workup and so vital for their success. At the end of the day, the MEG is just one other test we do of many, but sometimes it can play a very pivotal role in some of these patient cases. 

Host: That's huge to be identify the location so precisely. That's an amazing story. So what advice would you give a pediatric neurologist or epileptologist who might be considering integrating MEG into their practice? Are there specific factors that they need to consider deciding whether or not MEG is the right tool for the patient?

Afsaneh Talai, MD: Definitely, what I will say is there are not enough MEG machines in the country, and it's very expensive to get a program going. So, ideally, what a pediatric neurologist or epileptologist should do next is to identify a MEG program near them that can work with them to easily and quickly get their patients in for this study.

There's maybe about 50 in the whole country and not every state has one. There's a whole process to get insurance approval that requires a lot of manpower and dedication. Thankfully, our MEG team here at Children's and UT Southwestern has been doing an awesome job at this. And as a result, we've actually been getting a lot of MEG requests from out of state, you know as far as even California.

Host: That just speaks volumes to our program and how we're able to help our families get them in and help other providers. But yeah, most importantly is to find a MEG program that'll work with you to get your patient the tests they need.

So, as we close, anything else you'd like to add?

Afsaneh Talai, MD: I have to say that the MEG program requires a whole team of extremely talented individuals to successfully implement. As I mentioned, our MEG technicians are so awesome with getting our children who are very young or who have developmental differences to cooperate with the study.

They work so closely with the families to ensure a successful procedure. We also have MEG scientists who are PhD trained scientists who work with the data we produce. And the radiologist who then interprets the location of the findings. And I guess there's me. I read the actual squiggles that the MEG produces. But at the end of the day, it's a team approach and we have really one ultimate goal and that's to make the lives of children with epilepsy better.

Host: That's phenomenal. Thank you so much for being with us today. I have learned so much.

Afsaneh Talai, MD: Thank you for having me.

Host: And to our audience, thank you for listening to Pediatric Insights Advances in Innovations with Children's Health, where we explore the latest in pediatric care and research.

You can find more information at Childrens.com, and if you found this podcast helpful, please rate and review or share the episode, and please follow Children's Health on your social channels.