Opting for Epilepsy Surgery: How a Risk Assessment Tool Can Help Provide Expectations

Lara Jehi, MD

This is the second of a 2-part interview. Read part 1 here.

While a significantly effective treatment, making the decision to undergo epilepsy surgery is a serious and difficult decision for many patients with epilepsy and their families. For patients with refractory epilepsy, surgery may provide an opportunity to significantly reduce their seizure burden or become seizure-free; however risks of memory loss and cognitive impairment often prevent many eligible candidates from pursuing treatment.

At the 73^rd annual meeting of the American Epilepsy Society (AES), December 6-10, 2019, in Baltimore, Maryland, Lara Jehi, MD, sat down with NeurologyLive to discuss the pros and cons that patients must weigh when opting for epilepsy surgery involving the hippocampus. Jehi and colleagues have developed a personalized risk assessment tool to help better visualize the individual risk faced for each patient based on different characteristics.

Jehi, who is a professor of neurology and an epilepsy specialist at the Cleveland Clinic Lerner College of Medicine, also spoke on the risk for reoccurrence of symptoms and seizures following epilepsy surgery, and the complex factors that can influence a patient’s decision to proceed with the intervention.

NeurologyLive: Why is epilepsy surgery such a challenging decision for a patient with epilepsy?

Lara Jehi, MD: Epilepsy surgery is done when medications don't work to stop a patient’s seizures. The key to making it work is removing the spot that is triggering a patient’s seizures. That spot can be anywhere in the brain. It's a problem for the patient and for us when it happens to be in an area that is critical for a patient's function. One such area is the hippocampus. In most people, if we're talking about the hippocampus that's on the left side of their brains, then that's an engine for memory of words, numbers, things that you would use in your everyday life. If it's the right side of the hippocampus, it controls memory for visual data-- information that can be critical for some people, but not necessarily everyone, but still a highly important function. In most patients with epilepsy, the hippocampus is usually already damaged and scarred by the time they get to the point when they're considering surgery. In those patients, removing scarred abnormal tissue isn't high risk as far as losing function goes, meaning we could offer these patients a surgery to remove that scar tissue without risking, in most situations, them losing critical function. The problem that we face is in patients where we know that's the area that's triggering their seizures, yet there is no scar, it looks perfectly normal when we image it. We are faced with a dilemma where if we remove it, then the seizures are more likely to go away, but so is the memory. And if we don't remove it completely, then the patients may have some memory function that is still left, but the seizures are more likely to come back.

We had to make those decisions just based on hypothetical scenarios, without having clear guidance to tell us exactly what kind of risk we are taking when it comes to both the seizure recurrence risk and the memory loss risk with this type of surgery. We didn't know how much of it should be spared to preserve memory. Does it really make a difference if we spare it, but remove all of the brain tissue that's around it that is supposed to feed into it and help it function? It was a challenge that was coming back at us and we didn't have good enough information to help us know what to do.

This project that we did was looking at more than 150 patients in our center who had to deal with this dynamic and ended up having one surgery or the other. Either we took the hippocampus out, or we left it in. After doing a lot of testing to guide either decision and had a detailed assessment of their memory before and after they had their surgery, we then used that information to help us develop a tool to allow us to tailor decision-making to an individual patient. Depending on their imaging, what they're testing, and what their clinical situation looks like before surgery, we could tell them before they decide what to do. If we go with option A, this is your risk of your seizures coming back, but these are your chances of protecting your memory. If we go with option B, this is what you're looking at. And then as a patient, you can make an informed decision of which one you want to go with.

For patients with these types of refractory seizures, do you find that they are more willing to take that risk?

It's very individualized. I would be incorrect to say that there is a one size fits all with this. Some patients have been dealing with epilepsy for a very long time and have lost their jobs and lost their independence. They basically cannot function now anyway, regardless of what the memory function is, because of a very high seizure burden. Some would say, “I would afford to have some memory loss, but get rid of my seizures and give me back my independence.” We would then help them with developing strategies to compensate for that memory loss. It's never a memory loss where we are talking about people not knowing where they are. The memory loss we're talking about is something where, right now it takes you 5 seconds to memorize a phone number, instead it would take you 10 or 15. There are always strategies to work around it. Sometimes it can be more devastating than what I mentioned, but patients make that decision. There are other patients who just started having seizures, who have a very high-level job, where they cannot afford even that 5 to 10 second difference in how quickly they can memorize things. For them, their memory is very critical. They will to decide to go with the lower chance of success surgery, to try it out at least and see if it can help with their seizures without hurting their memory too much.

In the case that the surgery is not successful and there is seizure recurrence, what is the clinical outlook for those patients?

It is a repeatable process. If the first surgery does not work, there is always the possibility of reevaluating those patients and doing a larger resection that has a better chance of success. What we ended up finding in our study is that the smaller resections do carry a higher risk of seizures coming back, but it wasn't as much higher as we thought initially. Over time, that just evens itself out. Two years after the surgery, your outcomes would be different depending on that decision. But 5 years out, the seizure outcomes were the same.

With the memory outcomes on the other hand, there was a significant difference in people who left it versus took it out, which was the expected finding of the study. The unexpected finding, which I think is very valuable for us as we try to make these decisions, is that even when it was not removed, patients had a significant loss in their memory. That is most likely because even though we did not touch the hippocampus itself, we removed tissue that surrounds it that is critical for its function. When people make the decision of “I will take the higher risk of seizures coming back, but I am protecting my memory by sparing that hippocampus,” they may not be. Prior to this study, they may not have been fully aware of the risk to their memory by just having anything done in the vicinity.