Chengyuan Wu, MD at Jefferson University Neurological Surgery talks about using laser ablation to treat epileptic seizures.
You were talking about how a lot of the prep work is initially done so by the time the actual procedure takes place, it’s fairly quick. Can you explain that for us?
WU: Unlike other surgeries, where we may discover some things at the time of surgery, all of our procedures are planned beforehand so the surgery becomes very standardized. In fact, every week we plan all our stereotactic, or precision, procedures for the following week. What that means is that we’re looking through the MRI scan slice by slice, millimeter by millimeter, and figuring out exactly where we need to put either a stimulator, or in this case, a laser probe to get the best result. That’s what a lot of this work and research we’ve done is about because we focus so much on precision. How can we know that that precision is appropriate if we don’t know what the outcomes associated with that precision are? We must know what to target before we know if we’re doing a good job targeting it. That was the impetus behind this whole research. All of our planning is done beforehand and takes a number of hours. It usually involves a team including myself, a resident or fellow, and my partner as another set of eyes. We all work together to verify that that’s the best trajectory, not only from a delivery of therapy standpoint, but also a minimization of complications standpoint.
One of the things that stood out with your patient is the idea that when he would suffer his next seizure, it would be so unexpected that he literally could not live his life. How does something like this rescue that patient?
WU: In general, when we do surgery for epilepsy, we have the potential to offer a cure to patients. We have a high rate of success of seizure freedom. The degree of uncertainty patients have to deal with is what makes living with epilepsy so hard. That is why we always strive for seizure freedom whenever we talk about a patient in surgical epilepsy conferences. Even if you had two seizures a year, there’s still that uncertainty of saying, when is that other seizure going to be? Or when’s that one seizure? Or can I go out because I’m worried about a seizure. If you’re seizure free, all that goes away. Whenever we think about the most appropriate therapy for patients, we always strive for that high goal of seizure freedom because that’s really a life-changing event.
Does that happen in every procedure you do?
WU: No. In the study we did with 234 patients, we saw the seizure freedom rates across 11 centers at about 58 percent. That’s at one and two year follow up. And, that’s durable seizure freedom. The question is always… could we do better? When you look at open temporal lobectomy, which is what this is being benchmarked against, seizure freedom rates have been published upwards of 70 to 80 percent. So, as invasive as it seems, we continue to do it because we’ve done a lot of them and they’re exceedingly effective. Part of what makes this technology and laser difficult is that it’s against such a high benchmark. So even if we’re talking 60 percent seizure freedom, you’ll have people saying that’s still not 80 percent. We’ve been doing temporal lobectomies for decades and we’ve been doing laser for epilepsy since 2012. So, we’re talking about coming into seven years now. Still relatively new, but we must think about what the factors are that make a patient do really well versus not really well? Is it a patient selection aspect? Or is it something that we can control from a surgical standpoint? Without looking at that critically, we would never know. We have done quite a few laser ablations in the realm of about 40 to 50, but any one given center will only do 40 to 50 or so over the years. We had to work together to get numbers upwards of 200 plus with one to two year follow up. That was the only way this was going to work.
How much less invasive is it?
WU: Far less invasive. For a temporal lobectomy, the patient comes in and gets general anesthesia. We then shave a little bit of hair and make an incision on the head. We take out a piece of bone and then a piece of brain that’s approximately the size of a plum. That whole process takes about three to four hours. Then, we put the bone back together, sew everything up, make sure everything’s clean and the patient goes to the intensive care unit for a night. Their stay in the hospital can be on average two to four or five days. Recovery in terms of when patients feel back to normal can be anywhere from one to three or four months. Even though from the outside they look like they’ve healed after two weeks, people still feel the effects for several weeks to months later. Compare that to laser ablation, where the actual ablation is only about three or four minutes total. We’re usually done around noon with all that setup. Then they go to a recovery area before going to their room. We’ve had patients ask if they can go home that day and we are not so cavalier to let them yet. They stay on a short course of steroids just to help minimize some of the swelling. But people feel pretty much back to normal after a week or so. We’ve had patients that go back to work after three or four days. So, it’s very, very different.
When you’re operating on a patient, are you thinking how much of this is going to work? Do you know beforehand that the patient is going to hit that 60 percent or are you hoping they do?
WU: No, I outright tell a patient they have about a 60 percent chance of seizure freedom. During the procedure itself, all I really focus on is executing that plan as best as I can in order to maximize that chance as much as possible. That’s where all this targeting comes into play… putting in the probe and getting the MRI and making sure that probe is in the right spot. That’s also the hard thing about epilepsy, we never know until it comes months later. Once you are five months out and seizure free, we know that you’ve got a pretty good chance of being seizure free one year, two years and further out.
So, what you’re saying is that it’s sort of the chicken or the egg as to why the scar tissue associated with seizures exists?
WU: Absolutely. In the early experience with this, we would only choose patients with that scar tissue. That “mesial temporal sclerosis” is a hallmark of saying that’s where this is coming from. What’s interesting in this study and some of the other studies is we found that the presence of that scar tissue does not predict seizure outcome. If we’re confident that the seizures are coming from that area, whether you have scar tissue or not, does not necessarily mean that you will have a better outcome. The things that are really more important is making sure the seizures are coming from that location and in hitting that location.
How close to the patient are you during this actual procedure?
WU: I would break the procedure up into two parts. There’s the delivery of the probe that’s done in the operating room. I’m right there drilling and putting the anchor bolt in. That’s direct contact just like any other surgery. Once everything’s in place, we move to the MRI scanner. That’s phase two. Once we’re in the MRI scanner, that’s when we verify that the probe is in the right spot. Once we verify that, the OR portion is effectively over. We’ve done everything we’ve needed to deliver the probe to the right spot. Then it’s just activating the probe to create the ablation. That’s done in the control room of the MRI scanner. There are not only the computers that control the MRI, there’s a computer that controls the laser. That’s where we can monitor that ablation in real time, using MRI thermometry, looking at the heat happening in the brain, knowing exactly where we are ablating, how much we’re ablating, and then we will usually do three maybe even four ablations. When we do an ablation, we go back into the MRI scanner and pull back the probe about a centimeter, do another ablation and then repeat that three times to get a long ellipsoid ablation cavity.
In Scott’s case, how successful were you in treating this?
WU: Very happy with the radiographic outcome. Uniformly with these procedures, if I’m not happy with the end result, I’m going to do something until I am. Fortunately, that typically requires just one laser probe, and very rarely do we have to go back and reposition because we spent so much time planning and preparing that. As long as we stay methodical and meticulous about the execution, we’re quite successful with that.
Can you talk about the results of the study and what you were able to find out?
WU: The most notable finding was that location matters. That’s a really big thing because when you look at surgical studies a lot of times, you say, did surgery X work for disease Y? But you don’t really qualify it or quantify the appropriateness of the surgery. The analogy is that doing a surgery study without actually looking at what has been targeted or what has been ablated or what has been taken out is like doing a drug study without looking at drug levels. If you give a drug and it’s non-therapeutic, how do you know the drug didn’t work or you just weren’t applying it the right way? Same thing here. If our ablation is unsuccessful, how do we know it’s the therapy and not necessarily the way in which it was applied. What we really want to look at was how did the outcomes relate to where the ablations were? We found a strong relationship between where the probe was and the ablation that happened and then outcomes.
END OF INTERVIEW
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
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Chengyuan Wu, MD
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