Are You a Candidate for Epilepsy Surgery?
The May 2024 episode of Epilepsy Explained focuses on epilepsy surgery. In part 1 of a two-part episode, Dr. Scott Perry, Head of Neurosciences at the Jane & John Justin Institute for Mind Health at Cook Children’s Medical Center, answers questions about brain surgery for epilepsy including when to consider surgery, how to determine if you might be a candidate, and what tests you may have to undergo in preparation for surgery.
Video Transcript
Can surgery cure epilepsy?
Dr. Scott Perry: It can. It’s always something we want to happen in epilepsy surgery. You have to understand that it takes very specific populations that have a high likelihood of that happening. For instance, people who have a very focal lesion, well identified on MRI, that can be completely removed, would have a high A lot of the times our goals with epilepsy surgery are to reduce the seizures as much as possible, and hopefully more than could be reduced with other types of therapies. The definition of “cure of epilepsy” is to be seizure free for over 10 years, with five of those years off medications completely. So, it’s not an easy thing to obtain, but it’s something that can occur.
When should I consider surgery?
Dr. Scott Perry: We typically think about offering epilepsy surgery when a person has a diagnosis of drug resistant epilepsy. And what that means is that they have tried and failed to appropriately chosen and dosed treatments for epilepsy. The reason for that is because after you failed two medicines used at high doses, the likelihood the third, fourth, or fifth medicine is going to make you seizure-free becomes actually quite small. So we want to look at what other options that we have.
There are some instances, for example, people who have cortical dysplasia, as a focal cortical dysplasia, which is a malformation of the brain. We know those dysplasias are highly associated with drug-resistant epilepsy. So in some cases, we may even do surgery on those patients before they fail two medicines. That way they don’t have to experience seizures that won’t respond to therapy, and we can stop them hopefully sooner.
How do I know if I’m a candidate for surgery?
Dr. Scott Perry: So, I usually tell people that almost everyone’s a candidate for epilepsy surgery, but some people have characteristics that make them better candidates than others. There are certain conditions that we know, like for instance, in childhood, that only occur during a certain period of their life. For instance, childhood absence epilepsy or Rolandic epilepsy, those are epilepsies that will go away with age, and so we wouldn’t really consider them for epilepsy surgery, but almost everyone else could be a candidate for epilepsy surgery if they’re not controlled with medications.
Typically, we always thought about people with focal epilepsy or seizures coming from one area of the brain, but people who have generalized seizures and people who have seizures for multiple areas of the brain can all be candidates for epilepsy surgery. So really to find out if you’re a candidate, the first thing to do is bring it up. If you have not obtained seizure freedom after the first two drugs, you should definitely talk to your doctor about it and ask, would I be a candidate for a surgical procedure that might be helpful.
What tests will I need to undergo before planning for surgery?
Dr. Scott Perry: So, the tests you’re going to get will differ. It’ll differ depending on your seizure epilepsy situation, maybe how frequently your seizures are, what type you have, and also where you get evaluated, Most people will have undergone a video EEG where we want to capture multiple seizures, make sure they look the same, understand where they come from, things like that. A good high resolution MRI, so that we really understand the structure of the brain. And then we may do other tests. For instance, a spec scan, which is a type of study where we actually inject a isotope during a seizure. That isotope measures blood flow, basically. And so areas of the brain where seizures come from use more blood than other areas. And so, you’ll see that kind of light up in that study.
A PET scan is a scan we do where we give you glucose or sugar and watch how the brain uses that sugar to make energy. Areas where seizures come from often do not metabolize or make energy normally, so they look different on that type of scan. We might do something called a MEG scan or a magnetoencephalogram. It’s kind of like doing EEG, but instead of looking at electrical fields, it looks at magnetic fields. And the reason that’s important is because magnetic fields don’t look any different outside of the skull as they do in the brain, whereas electrical fields actually disperse as they leave the brain, and so may not be picked up on EEG as clearly.
We may do a functional MRI to look at where things like speech and motor and sensation and vision are in the brain. And then depending on that evaluation, some people will need an invasive evaluation or what we call invasive EEG. So stereo EEG or grids or strips. That’s actually a surgery, where we put electrodes directly on the brain areas that we think seizures are coming from to kind of help us narrow down even further, because we always want to find the smallest, most accurate area that the seizures are coming from.
All of this workup can take weeks, can take months. In some cases it can take years depending on what is necessary to get all the information to make a final surgical decision.
What is the success rate for epilepsy surgery?
Dr. Scott Perry: The success rate depends on, it depends on the patient and it depends on their etiology. There are some broad categories. So for instance, in temporal lobe epilepsy, people who have maybe mesial temporal sclerosis, they have high rates of seizure freedom after surgery. 80, 85% can be seizure free.
We know people who are non-lesional or where their MRI doesn’t show any abnormality, but we can localize where the seizures are coming from, they can be seizure-free too, but it may be a lesser number, maybe 60% or so. We know that people who have temporal lobe procedures tend to do better than people who have procedures done outside of the temporal lobe.
We know certain characteristics, like people who have, well-defined lesions, where we know that entire lesion can be removed, have a very high likelihood of seizure freedom. Children, for example, who have these hemispheric conditions where the entire hemisphere might be malformed. If we can remove that hemisphere, they can do very, very well and be seizure-free.
So it really depends on the whole situation. And that’s an important conversation to have with your epilepsy surgery team to understand based on those characteristics, what they think your chances are for either seizure freedom or seizure reduction after the procedure that they’re proposing.
