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Surgical Resection of Thalamopeduncular Tumors

Rick Boop

August 19, 2020


- Colleagues and friends, thank you for joining us this morning, evening, anywhere you are around the globe for another session of the virtual operating room coming to you from the Neurosurgical Atlas. Our guest this evening is, Dr. Rick Boop, from University of Tennessee, Semmes Murphy Neurosurgery group. Rick, is truly a dear friend, but besides that, Rick, is one of the most gifted pediatric neurosurgeons of our time. Beside being so incredibly respected, he's also an amazing leader who has had multiple, very high positions in AANS in pediatric society and around the globe. He's truly been one of the greatest champions of global neurosurgery. It's truly an honor for me to have him with us this evening talking about extremely challenging tumors, and those are the thalamic and thalamopeduncular tumors with, obviously, an emphasis in pediatric population. Rick, thank you again.

- Pleasure's mine, Aaron, thanks for having me. And I hope that introduction, she'd be proud.

- Oh, you're amazing. I truly meant it. Before we start, Rick, you have been, obviously, tackling some of the most challenging tumors in pediatric population with amazing results. Can you tell us what makes a great pediatric neurosurgeon in your mind?

- Well, apparently, when I was a resident, I was fortunate enough to be able to go to see kids on a pediatric neurosurgery elective. And I came under the influence of the three H's. Hoffman, Humphreys, and Hendricks, and they had such inquisitive minds and they would sit down and puzzle over clinical questions, treatment questions, and when they could, they would design the studies to answer those questions. So they approached clinical neurosurgery from a very, very research-oriented

- Perspective.

- and I was very impressed by them. I was very taken by them. They wrote a lot of papers. They traveled the world and made friends wherever they went, but they also learned lessons wherever they went and brought those lessons back home. And to me, that was so inspiring. I wanted to be just like them. I think it takes a special personality to be a pediatric neurosurgeon. It takes someone who loves children of all ages, regardless of whether they are normal children or abnormal children. But it also takes someone who can work with their parents at a time of life crisis and help those parents through the crisis. And, you know, most parents are used to being in control of their family, when they're thrown into a situation like our patients have, then all of a sudden they've lost control and they typically react to that. So we have to recognize that and help them through a time of crisis. But 30 years into my practice, the patients and the families that I've been to hell and back with, are the ones that I'm closest to still.

- Yeah. And you have, definitely, been a great, huge, you have created a huge legacy that I'm sure we all are proud of along with you. So with that in mind, let's go ahead and jump into your talk. Luke, please bring us to the PowerPoint. And we're looking forward to the presentation.

- Well, thank you. And I appreciate the opportunity. I was very fortunate when I was in practice in Little Rock when Sam Ameri took over the chair and brought Yashir to Little Rock. He was very interested in teaching, particularly, teaching junior faculty. And I was one of those. So we spent a lot of time together. He taught me the transsylvian approach for amygdalohippocampectomy. He taught me that he doesn't like to use fixed retractors even though he invented the most popular fixed retractor, et cetera. And so a lot of my microsurgical technique came directly from his influence. So when it came to thalamic tumors, we all learned the anatomy of the thalamus in medical school, the complexities of the specific and non-specific relay nuclei and so forth. And he dumbed it down to me and it's helped me quite a bit. He said, "Rick, there's two kinds of tumors in the thalamus. There are those that arise from the posterior thalamus, which are usually pulled in. It's a visual pathway. They don't present with motor deficits and you can be very aggressive there. And there are the anterior thalamic tumors, and they, typically, will present with motor deficits. And you have to be very careful in that region because you can worse than the deficit, or you can leave them with movement disorders, tremors, and things like that. So that helps simplify things for me. So when we talk in general about thalamic tumors, at least in children, they make up about 5% of the tumors we see. And, of course, it's a very challenging anatomy because it's in the center of the brain and it's surrounded by complex anatomy. So if you look at the approaches that are described in the neurosurgical literature, depending on the direction that the tumor grows and the course that it takes, people have tried all sorts of approaches. And as you can see here, even a transtentorial approach to these tumors. So I think it's important not to say this is the approach that I use, but to tailor your approach to the patient and to the specific circumstance. If you look at these drawings in this slide of the anatomy, you can see the thalamus and the ventricle medial to them is the choroid plexus and just above it are the fornices. And if you have a tumor that grows into the third ventricle, remember from Aaron's paper that you can take the septal vein here just as it starts to join with the thalamus right vein. And when you do that, that unlocks the door to the third ventricle, because once you've done that, you can open up the choroid fissure here and have free access to the entire third one.

- I agree with you, Rick. That's just, you know, your group actually were the ones describing this technique, which is so extremely useful. And so under-recognized, unfortunately, is that you can, in fact, cut the septal vein here as it joins the thalamostriate vein, and that would unleash or untether, the thalamostriate vein, which runs under the choroid plexus here. And in that case, you can dissect a little bit until choroid fissure leave the choroid plexus, medial or laterally as it's most easy to dissect along. And then the thalamostriate vein stays laterally, the foramen becomes significantly enlarged and with an enlarge framing, and you can do anything through the third ventricle. You can see all the way through the aqueduct. This approach is so much safer. In fact, then the transcranial approach described where you have to really manipulate not only the thalamostriate vein and a foreigner sees, and you really have to fight for every millimeter of your exposure in what we call a Transcallosal Transforaminal Transvenous means cutting the septal vein. You can really expand the foramen and already half of your exposure to the third ventricle is done. You only need to do a few millimeters of the intracranial dissection. So I just wanna make sure all of viewers know that this technique is actually from Dr. Boop's group. It's from Semmes Murphy and it's really a revolutionary way to approach the third ventricle but it's very much under-recognized. I, routinely, use it for the adults population and, you know, Dr. Boop, and his group have the largest series of this approach with significant amount of safety, minimal complications related to transection of the septal vein. So thank you, Rick.

- Yeah, thank you. And I find myself using it more and more people ask, "Well, do you have any venous infarctions from taking the septal vein?" In all the years we've been using it, I've not seen that. So here's some examples. This is a child who was referred to us at age 12, with a cystic and solid posterior thalamic tumor. Neurologically normal, local neurosurgeons had placed a stereotactic Ommaya reservoir into the tumor as you can see here. And, of course, that doesn't have much durability because when you do that, the proteinaceous fluid within the cyst will soon stop up the catheter. So it's not a durable solution. But you can see here enhancing nodules, suggesting this as a pilocytic tumor. And we know that pilocytic tumors displace normal, functional anatomy. They don't infiltrate. And when we see an enhancing wall, we know that that's a neoplastic carpet that has to be resected. But in a case like this, we don't see enhancing wall. So it's mainly just this nodule that needs to be removed. And you can see, we chose an approach through the posterior body trying to leave this plenty of intact. And that gave us a very nice approach to the tumor. And you can see the postoperative scan here and the patient with no deficit. There she is in follow up. In this case, however, that you can see the tumor starts in the posterior thalamus and grows, laterally, into the atrium of the ventricle. And for me, this is a very nice case to use a transcortical approach. Nowadays, we would use tractography to map out genicular calcar tract and make sure we stay above visual fibers and don't give a visual deficit. But you can see this was a very complex tumor. But, again, typical enhancement that you would expect of a pilocytic astrocytoma. And here's the poster section scan again with no discernible deficit in the patient who's cured. The lateral transcortical approach may be from a pridal transcortical approach. This is a child who came with a short history suggesting that this is most likely a malignancy. And, unfortunately, her father was a Gliadel sales rep, so you know this is gonna be a malignant glioma. But you can see our approach here from high parietal and debulking, what turned out to be a glioblastoma. And she went on to chemotherapy and radiation. So this is a paper that, Jeff Wisof, published with Alex Stanford. Tumors collected in children and followed for over 10 years. And these are all low grades of different types. And what you can see here is that the midline gliomas, foramic gliomas, and the hypothalamic gliomas don't do nearly as well as those on the surface. And then there are these unusual bi-thalamic tumors that are, diffusely, infiltrative. These patients will present with hydrocephalus and a fairly short history. And these tumors are obviously not resectable, but they're not treatable. And these patients follow a fairly typical course, similar to that seen in the children with the diffuse intrinsic pontine gliomas. Most of them live about a year to 15 months, despite all efforts. So remembering that 2/3 are low grade, that makes what we do as surgeons, critically important. 1/3 are high grade and for the high grade gliomas, the prognosis remains dismal. Nowadays, we have recognized the H3K27M mutation, which can be detected through immunohistochemistry and through paraffin embedded tissues. Typical of the diffused midline gliomas the DIPG, as well as the midbrain and thalamic malignant tumors. We now have good animal models working on histone deacetylase analogs, HDAC, targeted therapies for these children. At the moment we've not shown any improvement in the outcomes, but I think in the next decade or two, we should see good improvement in their survival. This is a paper from '98, and I don't think things have changed for these high-grade malignancies since that article. Typically, they present with a short history, they present with hydrocephalus, tremors, visual changes, seizures. That prompted this study that we did in, Memphis, about 2004, where we looked at 22 children who had malignant thalamic gliomas, five had been treated with craniotomy and resection, and 17 were treated with biopsy and shunting. And we were interested in trying to tell whether one conferred an advantage over the other in these children. And what we decided to do is look at their Karnofsky performance status, documented in the clinic notes from month to month and develop Kaplan-Meier curves with their Karnofsky performance. Remember the Karnofsky score 100 is a symptomatic and normal. 50 is requires considerable assistance. 30 is ready for the hospital unable to be cared for at home. And you can see for the group as a whole, that over a period of the first year, their Karnofsky dropped steadily and rapidly to the point where they were not functional children. When we compared those who had biopsy and shunt to those who had open resection, the two curves overlap. So we could not demonstrate a survival advantage nor a functional advantage to the children that had a gross total resection versus those who had just a biopsy alone for the thalamic tumors. What we did find was that we had significant hemorrhagic complications in the foramic glioblastomas in the children who had biopsies and even those that had shunts. And we had two peri-operative mortalities from hemorrhage into the tumor following either shunting or biopsy alone. You can see an example here of hemorrhagic conversion of the tumor following shunting. We took it out and controlled the bleeding and the patient recovered about the time they continued in their downhill slope. Here's another unfortunate case that came in with spontaneous hemorrhage within the tumor. And when we placed the shunt catheter, the tumor just blew up. The child was decerebrate by the time she got to the recovery room and never did wake up. So we are very hesitant to do stereotactic biopsies for thalamic GBMs. If we do, we put them in the ICU and we scan them frequently. And we tell the parents beforehand that it may not be uncommon to have to take this tumor out if it bleeds. So you can see how this, progressively, turned more hemorrhagic from one day to the next until it required a resection. So overall survival for the malignant gliomas remains poor median survival is about 13 months. The H3K27M mutations offer us a new target to study, to see if we can improve survival on these unfortunate patients. And the take-home message is that these tumors tend to bleed with shunting or with biopsy. And sometimes those bleeds can be catastrophic. Regarding the thalamo-pedunclar tumors, I'm gonna tell you the story of how we got into these. And this is from a 3D anatomy textbook, just showing the hippocampus, showing the corpus callosum, showing the fornix. And we think that these tumors arise from the junction of the peduncle and the thalamus underneath a normal thalamus. My first exposure to this was a six year old, who came in 2000 with this tumor that you see. Four-month history of progressive hemiparesis they almost always present with progressive spastic hemiparesis. And that's generally what leads to as CT or MRI scan, and the diagnosis before most of them have a chance to develop hydrocephalus. So in this case, we looked at the child and recognized that the tumor was underneath the thalamus. In the old literature, these tumors they were categorized with a thalamic tumors. And as such many people recommended a transcallosal approach to these tumors. But recognize that if you do that, you're destroying a normal thalamus to get to these tumors, not a good option. So what we observed, is that the tumor grows out of the peduncle across the cistern, into the temporal horn, as you see here. They, typically, will have a dilated temporal horn. And so I thought, why not approach it, open up the Sylvian fissure, like, Yashir, taught us and approach this from a transsylvian approach, get into the tumor in the temporal horn, and just stay in tumor. Which is what we did. You can see here where we opened up the Sylvian fissure and remove the tumor completely. And the child woke up hemiplegic. And I did not expect that outcome. And this was before we had DTI or tractography. But I'll make the point that these tumors are almost always seen within the first two decades of life. They may be solid. They may be cystic. They may enhance. They may not enhance. We've had many children treated with chemotherapy and radiation based on imaging, thinking that these were glioblastomas and when they didn't die, then it was discovered that they were pilocytic astrocytomas. So in the early years, we had a small group of patients. We're now up to close to 20 patients with this tumor. They, typically, will present as I said, with this progressive spastic hemiparesis some have had partial third nerve palsy, one had a homonymous hemianopsia from tract effect. And in these older articles, the first one I saw was this article by Ted Tomita. Seven patients approached from a subtemporal approach. And if you see, he was only able to get a gross total resection in three of the patients. They were all pilocytic. This a paper from the Paris group from, Stephanie Puget, is actually where the term thalamopeduncular was coined. And she gets credit for that. But if you look at these patients, five out of six, presented with hydrocephalus, which was unusual. And they, again, used a subtemporal approach. They were able to do a biopsy in two partial resection, two subtotal resection in two, and then three out of six went on to radiation therapy. So gross total resection was not a part of this series and yet pilocytic histology. So that's a surgeon's friend, if we can figure out how to do it. So this was our early series. You can see the ages of the children. They all presented in the first two decades of life. They too present with hydrocephalus, the rest presented with hemiparesis. Many had had prior biopsy, prior chemotherapy. And as tractography came into use, we found that ATL as anterior lateral displacement of the cortical spinal tracks, which happened in 80% of the children, which explained to me why the child that I did in 2000, woke up hemiplegic. We went right through his cortical spinal tract by going transsylvian to this tumor. So here's a case, and you can see again, how they grow out of the peduncle, underneath the normal thalamus, push the normal thalamus up. As you can see here. And grow across the cistern into the temporal lobe. So we postulated. We could look at tractography. And in this case, and this is the only one in our series where we've seen this, the cortical spinal tracks were completely pushed medial to the tumor. And that made it very easy for us to approach this tumor from a middle temporal gyrus approach, where we could wander up and down and get to the extent of the tumor. And, whereas, you can see, there's no way to get to the apex of this tumor from a subtemporal approach. It's just not a way to deal with these. So this was the first one that we used a middle temporal gyrus approach on, and we were able to get a gross total resection, as you see here. Here's our track to the tumor. We do this using forehand technique, which is two opposing oculars, two opposing surgeons working with four hands, assisting one another as we go. And what we found is that, because the tumor stretches the normal thalamus up, if we get into the lower portion of the tumor, It will deliver itself to us. Here's another patient that a similar presentation. And again, you can see here how the tumor has grown out of the brainstem across the cistern. They will often stretch the choroid fissure until it tears, and then they grow into the temporal horn. And when they do, they may obstruct and cause it to dilate. So in this child, here you can see the anterior lateral displacement of her cortical spinal tract. And so we thought we could use frameless stereotactic to come in, middle temporal gyrus behind the tract, get into the tumor here and debulk. And what we also learned, is that you have to look for the optic tract because it's always stretched, laterally, around the tumor and if you don't recognize it, you can get into it and they wake up with an amount of hemianopsia. The other structure at risk is if the tumors grow down below the tentorium. The third nerve may be stuck in the tumor capsule. And sometimes it's so thin out that it's hard to identify. So if we could play this video, we've used frameless stereotaxy to guide a ventricular catheter into the temporal horn. And then you see the two opposing surgeons. We've made a colyconomy along the middle temporal gyrus. You can see the choroid plexus in the view there, working over the alveus of the hippocampus and trying to keep it protected with catenoids as we work so that we don't damage it. But the choroidal fissure comes into view. And as we open up the choroidal fissure here, you can see the fimbriae will just tear. And the tumor capsule comes into view. When we first started this approach, I was concerned that the patients may develop temporal lobe epilepsy. And we've actually not seen this at all to date. We've not had any of the kids seize from this approach. But if you look as we focus down, this is the optic tract here, and this is the basal vein of Rosenthal here. There's a vein optic tract. We wanna be careful about retracting on the object tract. We also wanna keep our catenoids over the alveus. But here we're opening up the tumor capsule and you see the typical gray fleshy appearance of a pilocytic astrocytoma inside the capsule. And these are confluent tumors, very easy to debulk them with the ultrasonic aspirator, so that we minimize the motion on the brainstem. So you can see here using the ultrasonic aspirator to debulk the tumor. We've obviously taken pieces for pathology. But you'll see at the end of this slide, the glistening white of the white matter tracks in the brainstem, as opposed to the gray fleshy appearance of the pilocytic astrocytoma itself. And so we have both textural and visual cues of the tumor when we're here. And when we get to the end of the tumor, you can see the white matter come into view there. So you know, when to stop. So here's her post-operative scan. You can see are tracked through the middle temporal gyrus to tumor here. The enhancement is choroid plexitis. And next slide, please, Luke.

- May I ask a question, Rick? How do you position yourself and your assistant? It seems like you really can do a really nice work with two surgeons on their microscope? That's very difficult to do, usually. Can you tell us a little bit your positioning and how the assistant is sitting?

- We have the patient in pens with the head nail and eminence towards the ceiling and make a linear incision using frameless stereotaxy. And so one of us is standing on each side of the head, and it's a very comfortable position. You can sit or stand, but you're 180 degrees apart from one another. And in doing so, we learn to help each other. It's a very nice technique when you're training fellows in residents because they can be an equal part of the operation as you move through it.

- And the other issue is that I know vein of Rosenthal is always, you know, one of the critical diastolic veins, it has to be preserved. It may cause, you know, diastolic infarction, if it's taken. However, based on what I saw in the video, and what I have seen him in my videos, it ends up right the center almost of your dissection. And you may have to take it at times. I have taken it a couple of times and I have never had a complication. I'm not recommending we should take it. I'm just saying those two times that I had to, patients did not have any on tour defects. Did you ever take it? And did you have any complications?

- Right. It's a good question. Like all deep veins, we should preserve them whenever we can. In the case, I just showed you, initially, it was quite congested. And as we debulk the tumor, the vein became slack and we did take it. We transected it and the patient tolerated it just fine. And I've done that two or three times and not had a complication, but I've had a partner take it in a medial temporal lobe tumor and have the patient wake up with a venous infarct of the mesial temporal structures. So I think if you have to, take it. Most of the time you'll get away with it, but when you don't get away with it, it's a disaster.

- No, I agree. Very well said. Any other pitfalls in this approach that you wanna tell our colleagues who wanna try it? Obviously, it's technically very challenging. It's a very long reach. You really have to be very ambidextrous and, technically, very agile. What else, technically, could be a pitfall?

- You'll notice we didn't use any fixed retraction. We use dynamic retraction. And I think that's very important. Fixed retraction's metal damages brain and fixed retraction damages frame. So we don't use fixed retraction anymore. It takes some skill for the surgeons to use the forehand technique, but it's not that complicated. So the optic tract should be identified early. Most of the time if you don't see it, when you open the choroid fissure, it's going to be just above where you're looking and you can usually find it with your frameless stereotactic equipment, if you can. The other is, if you're working along the edge of the tentorium, look for the third nerve and be careful of it.

- I agree. May I ask, do you use neuromonitoring, intraoperatively?

- I have not with these. I don't know what I would monitor. Maybe yeah, I have not.

- Moderate evokes or you have a monitor and motor evokes or somatosensory evoked potential.

- We use a lot of monitoring, Aaron, and I just haven't seen much utility of it here. The tumors have been so obvious and when you get to the end of the tumors, you'll see in some of these videos, it's pretty obvious.

- I completely agree with you that it's not necessary, but I think that's a question we often are asked. And how much do you push the limits to the white matter? Do you go just until you see a little bit of a white hue, or do you really clean out the carpet of the tumor over the white matter, Rick?

- I try to clean the carpet of tumor down to good white matter, yeah.

- Okay.

- Obviously, if you see any perforating vessels, try to preserve those when you can.

- Okay, thank you. Let's go to video of this little girl, please.

- That was a cell phone video father sent me three months after her surgery. It's a case just presented. And what you'll see is, her face and her arms have made a complete recovery but when she walks, she still has a bit of a spastic gait in that low one foot and is typical in these cases unless they present with normal neurologic function, they'll always remain with some impairments. Sometimes the arms and the legs, sometimes

- [Father] Say, "Hey, Dr. Boop."

- Hey, Dr. Boop.

- [Father] Hi.

- Hi.

- She's just saying, hi. Next slide, please.

- You know, Rick, that's an excellent result. That's truly an amazing result operating in this area. Amazing results.

- Well, thank you. This next case is a three-year-old who came to us from California. Local neurosurgeon had done a stereotactic biopsy. And as you can see here, as his biopsy tract was through the frontal lobe, and notice that the tumor does not enhance it all, but this lack of enhancement, it looks pilocytic, and her presentation was progressive spastic hemiparesis just like the other. So when we look at this patient's tractography, in her case, and she's the only one in our series that has this, her cortical spinal tract were, completely, stretched draped over the outside of the tumor, so that a transtemporal approach was not a feasible approach in her case. So in her case, we made the decision to follow the biopsy track down through the middle frontal gyrus into the tumor, oh, that doesn't show well, and we were able to get a gross total resection, as you can see there, without much difficulty. And she's done very well with it. This is a picture her family sent about six months post-op. And again, in this case, you'll see that her leg has made a complete recovery, but she still has a spastic arm. Face is completely recovered. I think we can go on, Luke. I think that demonstrated the point. Now, this is a child who presented with hydrocephalus. He came to us from Alabama, and you can see the ventricles getting large here. And then this tumor by the CT scan that we were told was opposed to your faucet tumor. Obviously, it's more than just that. You can see the MRI. The typical cystic and solid areas within the tumor. Again, we thought that this looked pilocytic. What's interesting about this case is, number one, he had no hemiparesis. He just had hydrocephalus. And number two, this tumor extends very low down in the posterior fossa. Well below the tentorium. And I didn't think I could get to the bottom of this tumor without either damaging the third or the fourth nerve. So in this case, we used a combined approach in a single setting, where we went through the medial temporal lobe. First, up here, took out the superior half of the tumor, then used a retrosigmoid approach to get to the lower portion of the tumor that you can see here, as well, underneath the tentorium. So here's this tractography. And you can see his cortical spinal tract for pushed anterolateral as well. So we had a corridor here through the middle temporal gyrus that took us into the upper segment of that tumor quite nicely. And this is a picture with our intraoperative MRI when we were halfway through showing a complete resection of the upper portion before we went to the retrosigmoid craniotomy and took out the lower portion. So, Luke, if you could play the video. We use frameless stereotaxy to pass a catheter into the temporal horn through the middle temporal gyrus. And you can tell you're in the temporal horn because you've got good CSF pulsation out of the catheter, then enlarging the colyconomy to the size of a half by three catenoid, following the catheter down till we get into the temporal horn. And then when we removed the catheter, put in our catenoids, and we see tumor immediately upon entering the temporal horn. And so typical appearance of a gelatinous pilocytic tumor. You can see choroid plexus above here, and using catenoids to retract. Getting the pathologist is due, which is extremely important, particularly, nowadays, when we're looking at molecular targets for treating these tumors. Then using the ultrasonic aspirator to debulk. And again, you can see the typical fleshy appearance of the gray pilocytic astrocytoma, which is distinctly different than the sub Jason white matter. Once we've got the top part cleaned out, we left gel foam there, and then here's our retrosigmoid approach without having to reposition the patient or anything. It's not difficult to do these. And I've got another case where I'll show it at a taking and then you can see just under the arachnoid, the tumor capsule in the posterior fossa. And we open, you can see us dissecting the cranial nerves off of the tumor capsule here. And you'll see the fourth nerve come into view here and then opening the arachnoid, opening the tumor capsule, and getting into the tumor. And once we're in the tumor, staying in the tumor until we see the normal brain around it. Typical glial cyst fluid coming out of the cyst as we open it. You can see the gel foam from above that we left there with our temporal resection. And then this is the inferior portion of the tumor here. And debulking that. All of these children we've extubated at the end of the surgery, we've not had to keep any of them intubated. They've not had swallowing difficulties. They've almost all had worsening of their hemiparesis immediately after surgery, and then that recovers fairly quickly over the next few weeks.

- It's really a nice approach. Gives you a panoramic view of the whole tumor.

- Yeah, it's a very comfortable approach. And as I said in the next video, you'll see that you don't really have to reposition the patient. Now, Keki Turel, has had some cases. I've seen him approach these tumor from a super cerebellar inference and toil approach. And if they present more posteriorly, then I think that is a very nice approach as well. He does those in a sitting position, which for me is not as comfortable as this position. You can see they appear the brainstem here and then the tumor capsule here. And just standard microsurgical tumor removal with debulking and then the section of the catheter of the capsule until we get

- Yeah, the tumor is very discolored and it's a nice feature. So you can differentiate what's normal, what's abnormal. And, obviously, the texture is also very different, Rick. And that provides a significant guidance in terms of removing the tumor, so.

- This is a video of the child on post-op, day four. All right, what's your name?

- Christopher.

- Can you show me your teeth, Christopher? There you go. Can I see you walk? Walk down the hallway for me. You'll see he's still ataxic. But this is four days post-op. Can you come back for me? Very good.

- [Woman] Good job.

- Can you hold it right there for me? Luke, you can go to the next slide. Can you raise your arm up? Good job. That's right. And this is three months post-op. Luke.

- [Woman] One more time, one more time.

- So this child doesn't have any obvious neurological Next slide. This is a more complicated case and, Luke, you can play it. I'll talk as we advance. And thanks to my fellow, Chandra, and, Zang, for editing this video. This child came to us from Seattle, five-year-old boy. Initially, had a hemiparesis and then developed bilateral trigeminal neuralgia and had a catheter placed into the cyst, hooked to an Ommaya which didn't help. But you can see how extensive this tumor is. And here are two incisions for the transtempolar approach and followed by the retrosigmoid approach, all in one setting. So familiar scene here, two opposing surgeons using an incision of a catenoid pattern following the catheter down to the tumor in the temporal horn. Here's the obvious of the hippocampus. Choroid plexus above here. And then there's tumor capsule just underneath the choroid fissure as you can see here. And, again, trying to protect the obvious of the hippocampus with catenoid after we've opened the fissure. Dissecting out as much of the capsule as we can, before we get into the tumor, and sizing the capsule with an 11 blade. And you can see the gelatinous, grayish appearance. In this case, the tumor was quite gelatinous and suckable. And I'll make the point, that, the tumor is obvious when it's gray. But if you bipolar these tumors, they turn white. And what you bipolar looks very much like white matters. So you need to limit your cautery to just what needs to be cauterized and not try to do widespread cautery. Typically, these tumors are not particularly vascular. As you can see here, blood loss is not a major concern. And so we'll debulk, then we'll mobilize until we find white matter at the periphery and try to work along that plane as we go. When you get to the white matter, you can see how glistening white it is. Completely different texture and color compared to the normal brain. So here we finished the temporal component, close this, and then open up our retrosigmoid approach. He had actually had a previous biopsy through that. So this is a redo retrosigmoid that we're opening here. But no need to reposition the patient. Making the approach to the tumor. The transversing and more junction. And again, once we get to the posterior component of the tumor, we get into it where it comes to the surface. And again, you see that gray fleshy component, typical, of the pilocytic tumor and, distinctly, different than the normal brainstem next to it. We, eventually, come to the Ommaya reservoir that was left there, and you can see the tip of the catheter. We took that out at the same setting. And you'll see us come to the end of the tumor here. The tissue becomes firmer and it becomes more glistening white. So, Luke, I think you can move to the last few seconds of the video here. The rest is just fairly standard. You can see here, the blending of the tumor with the brainstem. Here's his intraoperative MRI confirming a gross total resection. Here's his incisions post-op. This is one month after surgery. Next slide, please. And this is a video his parents sent me last week. He's now two years out from surgery. Still has a weak right arm. Those legs have made a great recovery.

- [Group] Four, five, six, seven, eight, nine, ten eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, twenty. Next slide, please. Next slide. And you can see he still has to where a band on his wrist here for a spastic arm, but very functional child. Back going to school, and two years with no evidence of any recurrence. In our series, we've had four patients develop a homonymous hemianopsia. One of those was a redo operation. We've had 2/3 nerve palsy. We've had two who had a worsened hemiparesis, postoperatively, that did not completely recover. All of the patients that I know of are ambulatory. We have one obese child that may not be ambulatory, but, generally, they can get back to where they can walk. This case is an interesting case and that he presented with a typical pilocytic thalamopedencular tumor. We tried to debulk it, but as you can see here, his tumor was multi-focal. And in follow up, he recurred with all these little multi-focal areas. So he went on to low-grade chemotherapy and then radiation. And his parents sent me a video a couple of years ago of him in college. Still alive over a decade later with this multi-focal residual. So his did not act like the other tumors. So we published a paper a couple of years ago, looking at the BRAF mutational status in our series. We had 12 patients that we had tissue for testing, and 10 out of 12 are positive for the KIAA 1549-BRAF mutation. And I'm not gonna pretend to be a molecular geneticist, but we had two that were positive for BRAF, different BRAF fusion, basically. But we had two patients that did not have the typical BRAF fusion. One of those recurred within six months. So it was not a typical, most of these children have been cured by surgical resection. The other was the child that you saw with the multi-focal tumor. His was an FGFR1-TACC1 fusion, which we've not seen in any of the other patients. So whether that explains the difference in the biology of his tumor compared to the rest of these, is speculative. But the vast majority of these tumors will have a BRAF V600E point mutation. That gives us a targetable treatment strategy. So in closing, these tumors, typically, will present in the first two decades of life. The youngest we've had was two years old, the oldest we've had was 16. Most are amenable to resection for cure with acceptable morbidity. They have not responded well to chemotherapy, and at least low-grade chemotherapy. DTI/tractography has been very helpful. And the adjunct of the intra-operative MRI has as well. The structures' greatest risk are the optic tract and the third cranial nerve. And I'll make the point that if you get both of these in the same patient, they can't open the ipsilateral eye and they have a hemifield in the opposite eyes. They only have one useful nasal field of vision if they have both of these in the same patient. We've had that happen one time. And that's not a very good outcome. I'll pause there, Aaron, and we can go on to questions.

- Very nice lecture. Very difficult series of cases. Very impressive, Rick. As we all know, couple of very good questions. Number one is, I assume through the transtemporal approach, is it a quite hemanopsia or what is the expected visual field deficit in these patients?

- We've not seen a temporal lobe visual pie in the sky autonomous deficit in any of these patients. I think we're coming in low enough and anterior enough that the genicular calcram tract is above us. And it, typically, comes in further back. We're coming in at the level of the optic tract as it comes from around the brainstem.

- Okay. And the other good question is that, have you tried the approach through the posterior fossa, where you remove the posterior fossa component through the retrosigmoid super cerebral approach, you cut the tent, and then you go through the medial temporal lobe and clean out the rest?

- I've not tried that, but I think it could be done. As you saw in that last video, the fourth nerve is there. And I don't know that you could get to the superior aspect of the foramic portion without injuring that nerve.

- I agree. I have tried that frequently and I have really liked it. In children, it can be more challenging because the space is so small but in adult, there's more space to work with. So I think that's very different. And somebody asked is, "What is the single most important nuance for tackling thalamic tumors?" If you can say what's the absolute most important factor, what would you say, Rick?

- Well, I think the greatest advance for us has been advances in neuroimaging and frameless stereotactic guidance because we know where functional pathways are. We know where the tumor presents to the safest point for the surgeon. And with the frame of the stereotaxy, we know where we are when we get there and can't, and the anatomy is distorted.

- Right. And the optic tract really is not thinned out, necessarily, over these tumors the way you approach them trance temporarily. I think you're much more anterior, am I correct, Rick?

- That's correct.

- Okay. That's one of the questions that came in. You know, Rick, I wanna thank you again. Obviously, there's another very important fact about your families, that there's three generations of neurosurgeons in your family. Your dad, yourself, and your son, who is now a resident in the University of Washington. It's truly not only your legacy on neurosurgery, your legacy of great neurosurgery, is also multi-generational legacy of neurosurgeons in the Boop family. Can you tell me, what's the trick there? How is it that your dad was a neurosurgeon, you're a neuro neurosurgeon, your son is a neurosurgeon, is there anything that you wanna share with us that has made all of you guys so interested in this profession?

- Well, I know for me, it was reverse psychology. My dad said, "Whatever you do, don't go into neurosurgery." So, of course, I did. I tried to remain neutral of my son and he chose it by choice.

- You must have been a been a great role model. It couldn't be done any other way.

- Very proud of him.

- I would be too, absolutely. Actually, met him in one of our AANS meetings a few years ago, a really a solid man. So with that in mind, I wanna again, Rick, thank you for discussing some of the most challenging tumors, intrapregmo tumors that we tackle, especially in children. Those can be very daunting. Really a great corridor through the transtemporal approach, combined approaches that you described, and really giving these kids a chance. And I can see from your videos, how much you care about the outcome of these patients. And, truly, the greatest satisfaction I think in neurosurgery, comes from treating children. Because not only their tumors, some of the times turn out to be benign, but they're so resilient. And the outcomes are so satisfying. So with that, I wanna appreciate you for being with us this evening, and look forward to having you again with us in the near future.

- Well, thank you. Thanks for those who logged on from around the world.

- Thank you.

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