Transcript

- Colleagues and friends, thank you for joining us for another session of this short OR. Our guest today is Dr. Robert Spetzler from Barrow Neurological Institute. He doesn't require any introduction, truly a role model for me and all of us. He's gonna talk to us about the third ventricular tumors or lesions in the area, a place many of us refer to as the seat of the soul, if such a thing exists as the seat of the soul per se. And really one of the most difficult places to reach. And they're more approaches described to the third ventricle than any other place in the brain. And that's an indication for really the difficulty of this location. So, Dr. Spetzler, thank you again for being such an immense contributor to this series and please go ahead.

- Thank you, Aaron. It's a pleasure to be talking about a kind of lesion that really requires everything that we have learned about the anatomy. And that really requires everything that we know how to get to the deep portions of the brain. In order to really do microsurgery as is required for this particularly difficult area, the surgeon needs to be comfortable. There are many different ways to be in the comfort zone, for me to be sitting, having arm rests and wrist support, and then utilizing your foot pedals, like playing an organ, to move the microscope if necessary, always using a mouthpiece so that your hands are constantly available. And the mouthpiece also always gives you the very best trajectory for your vision and for your light. And with a foot pedal, you can obviously use the mouthpiece in an arc motion rather than just the X, Y axis. And this is basically the way we sit at the operating room table. One of the things that's really important is to recognize is that our visual axis and our light axis come in at different angles. And that can vary between three to six degrees, depending on how long your focal length is, which means that if you wanna have the best vision, which is straight down the visual axis, your light may be totally inadequate because it'll bounce off the side and this is particularly so as we work with very increasingly smaller corridors. So in order to obviate that we have designed some instruments that really bring light down to us, as you can see right here, by either utilizing a lighted suction or a lighted bipolar. Anatomy, anatomy, anatomy, especially when were talking about the third ventricle, this is a view from above where we can see the two internal cerebral veins. We can see the foramen on each side, we see the choroid plexus and I want you to notice the choroid plexus as it sits on the thalamus, because our approach is gonna be a little different than it's usually described from the textbooks. Here the internal cerebral veins have been separated and you're looking right down into the third ventricle. When we look inside the third ventricle, what we really wanna concentrate on is the fornix. So we see that column of the fornix and we see the body of the fornix. So if you look at the relationship of the fornix and the thalamus and the choroid plexus, the reason I like to go lateral to the choroid plexus rather than medial, which is the way it's described in most textbooks is because it gives you one extra cushion to protect this all important fornix. And then if we go through the septum pellucidum up front here, this absolutely incredible beautiful anatomy. There are many, many approaches down into this region, and we're gonna go through them step by step. The transsphenoidal is naturally a classic approach, and I don't do the transsphenoidal because I have one colleague, one partner that does this all the time. And so we're gonna come from here through the transsphenoidal approach. And what I've done is I've borrowed a little video from my partner, Dr. Andrew Little, and this is after he's removed the tumor, and you can see the end of the third ventricle in the anatomy beautifully as can be seen from this elegant approach. So we're gonna take this case, and this is a patient that has declined and acute loss of consciousness, and you can see a large lesion that's occupying a good portion of the third ventricle. And obviously you've got some obstructive hydrocephalus. So we're gonna do a sub-frontal approach. And obviously you have a number of routes and we'll use them all. So here's one sub-frontal, in this case we're going over the optic nerve underneath the anterior choroidal arteries, right in the midline and as we open the cyst, this is obviously a craniopharyngioma and the importance in this here is to not hurt the hypothalamus. And so I like using this sweeping motion with the sucker that has a teardrop on it. So when your fingers off the sucker, there's absolutely no suction going through it. So you can just use it as a blunt, gentle disector. And then as you progressively obstruct the teardrop, you get increasing suction, which is a nice way to really manipulate this section, which is so critical. And here you see the actual tumor with the classic appearance of the calcifications. We're still on top of the chiasm, again, just separating the tumor and small steps and utilizing that pulling slight tension and then sweeping motion with the sucker and don't wanna lose any portion of the cystic wall, because if we leave anything behind, a recurrence is inevitable. And again and we just keep going until we really get it all out. Now we're looking into the third ventricle. And if you look at the pre-op and the post-op, you can obviously see the lesion gone completely. And this patient did well, except for the temporary problem with thirst that is inevitable. This is a bigger tumor where the patient really had lost vision with bitemporal hemianopsia and in the nasal field on the left hand, he only had hand-waving appreciation of vision, and we can see how large it is, how it's extending up into the third ventricle. So in this case, we're going to go through an approach between the internal carotid artery, underneath the optic nerve and a little lower. And each one of these approaches is for a specific purpose. So now we're looking at the optic nerve carotid artery soft to the side, we're looking right at the wall of the tumor. This is obviously another craniopharyngioma. We're emptying out the contents that are soft and suckable to give us adequate room to move everything inside. Now, as we look at it, what we're really concentrating on now is the infundibulum. You can identify the hypothalamic stock with how the blood vessels are oriented. And I'll show you that in a second. And here we're just moving the wall, just keep moving a toward the inside and then keep cutting the wall. And as we're localizing it, here's the stock. That's the stock, see how those blood vessels are going in a parallel with the lesion itself, with the stock itself. And there's obviously quite a bit of controversy, whether you should go ahead and cut the stock when it's that high or not. I make every effort to maintain the integrity of the stock. And so here's still a little bit of attachment. And again, we're right, that's this stock coming right on the back. And so we just keep separating it, that stock that's distal, this is proximal. So I'm cutting it off, I'm sacrificing a few fibers of the stock in order to get complete tumor excision, but there's the stock in continuity and intact and you're just removing the last bit of the tumor. Piecemeal, so that we could see better. And again, we see the integrity of the stock and then finally the last piece of the tumor wall. And when we see the post-op, we can see that the lesion is a beautifully gone and the third ventricle is open again. And you can see how the lateral ventricles have collapsed. This is a gentleman that was operated elsewhere with the appearance of this lesion and the progression of lesion and postoperatively after they operated on him, he had a left side of hemiparesis, right cranial 3 palsy and hypernatremia. And their impression from the surgery that they did was that the diagnosis was a glioma. As we look at their post-op scan, six months later, when they referred them to the BNI, this is what it looked like. So here we are through a OC approach going down, right down you'll see the superior cerebellar artery, posterior cerebral artery, basilar artery. Remember you had a third nerve palsy, we're mobilizing everything away from the blood vessels, utilizing image guidance to get our trajectory, to know how far we have to go to the other side, SVM did it out, it looks like a very much of a vascular lesion. And very quickly it becomes obvious that this is actually a cavernous malformation. And so here are the golden changes. We go around the edges until we get it mobilized and can remove it completely. And here we are, we're now past and we see the speckle typical pattern that surrounds a cavernous malformation. Actually, I wanted to show this, this is obviously the post-op and you could see the space where the lesion was beforehand. This is a three-year-old with intractable gelastic seizures, precocious puberty, non-verbal on Tegretol and Keppra and the seizures are not controlled. And here I'm really operating with my pediatric colleague. And you can see this a classic hematoma sitting inside and below and to the side of the third ventricle. And what we're going to is we're gonna go anterior and we're going to go between the leaves of the fornix, so an interforniceal approach. This is an approach that really has largely been discontinued since we have newer ways of taking these out. And it is an approach that should definitely never be used in adults as the risk is quite high, but the young children really accommodate to it very well. The head is horizontal with the elevated. Every one of these hemispheric approaches, we have the head horizontal, your eyes are horizontal, your hands are horizontal. So that makes it the easiest to work. But you can see the space really goes right down between the fornixes and that's where the risk comes in the adult population. So here we are, the head is horizontal, we're using gravity, no retractors are required. We go anteriorly, we're using some small sponges for retraction and now we're between the leaves of the fornix. And as we go down into the third ventricle, we identify the classic appearance, this hematoma. And it's really quite distinct and relatively easy to separate from normal structures. And here you can see as we're getting lower we will see the base and the arachnoid that covers the basilar artery. I like to keep this arachnoid intact for protection, but now we're looking straight down to that region. And when we look post-op, this is what it looked like pre-op and here the lesion is completely gone, it's all folded together. And this young three year old did very well. Progressive weakness, here we have a lesion that impinges on the third ventricle. For these I really liked to go contralateral, right by the choroid plexus to get to the lesion. And that's the approach we use. And here we're opening the corpus callosum and going right across. We're gonna open here the septum pellucidum 'cause it's bulging up and you can see as we open it, it's settles down, so we're not going to the other side. We can see already the hemosiderin on the thalamus. This is a very robust entry point with very little risk. And then as with most cavernous malformation, we create a space within the lesion and bring the edges into that space and remove it in a piecemeal fashion. You can see the is really just about as big as the sucker. So getting those two instruments in just automatically enlarges that opening just enough so that we can work in that tiny little space. Bringing everything toward that space, you could see the little pituitary like instruments, and then using the sucker as counter traction and just keep pulling, loosening up, utilizing these two instruments. If we get any significant bleeding, it is always venous. So a little Tampa knob and a little bit of patience is always adequate to control this. But you could see how it becomes looser and looser as we go around wherever it's attached, we'll do some work until we can finally bring the lesion out. Critically it's naturally to keep going until you really see normal wall all the way around. And the endoscope here is very helpful. And that's what we're doing right there with utilizing an angled endoscope. And when we look at the post-op, you see the MP cavity. So we came contralateral and took it right up. This is significantly more difficult. And the problem here is that this is really too low to come this way. It has the aqueductal plate, if we wanted to come this way. And he presents with the most difficult problem, which is this disabling right arm tremor. And this lesion has been known for five years, has slowly increased in size and the tremor has gotten worse. So when we look at it on different planes, we see it here. You can see that this is really very difficult to get to. It is very difficult to go from this side and very difficult when we come in this way to get up to here all the way up here. And the aqueduct really from behind, that's a very, very difficult entry point. So what we ended up doing is going through the space where the middle cerebral artery rests. So here you can see the angle, this is our trajectory. We're coming right by the very distal portion of the middle cerebral artery to get to this lesion. So here we are, we have opened the sylvian fissure all the way, we are now at the distal end of the middle cerebral artery. That's the disc lament, the bifurcation is right here. We separate the small vessels, we check our trajectory and then we make a small opening right in line with our image guidance. We enlarge it, be able to get our instruments in there. And now we're at the cavernous malformation, very, very small opening. This one is a very bloody cavernous malformation. And again, the same technique that we've utilized before to get it out, that sweeping motion, only a very small opening through the space that we've created and we just keep loosening it up. There was little down biding instruments that we've developed. I'm really very, very fond of those tumor sectors, they're sharp and here sweeping off the vessels overlying it to bring the rest of it up. Unfortunately, I left some blood behind but it shows nicely the cavity. So his hemiparesis right afterwards was worse, but his pre-op tremor, which was really his most disabling symptom was completely gone. And I think we may take credit because we took this out, but I suspect this little infarct that we caused is probably why the tremor is gone. And fortunately his weakness recovered completely by six months and his tremor remained cured. He was a very, very happy camper. This is the kind of tumor that you love to have when you're going in from the top. You can see it fills the entire third ventricle, and it's obviously an epidermoid, it has split. The fornixes are ready, all the work is done. So we're gonna go anterior transcallosal. And here's a few really from the basilar artery. And here's the epidermoid, we just keep removing and removing. So we're looking from the top down and we're gonna be seeing the basilar artery all the way down to the vertebral artery, moving the tumor toward the middle. We're gonna see ICA off to the side. Now we're looking at basilar artery there. ICA will see six nerve, all the branches and we just keep removing the epidermoid piecemeal to the best of our abilities. And so we see basilar down below, we see the junction, we see the vertebral artery, and you can see how we got all the way down to the very bottom of this cavity. This here is the classic appearance of obviously a head a colloid cyst, and you could see that started developing increased size of the ventricles and elected open surgery, which is what I prefer for these. And obviously this is through the foramen of Monroe. Again, the head is in the horizontal position. I like taking the dura over the sinus so that when you are retracting the dura, you were actually pulling up a little bit on the sagittal sinus to give you one more millimeter. So here we're going through the corpus callosum. This is the cyst already, this is the foramen of Monroe. We know that up here as where the fornix lies, thalamus down below and so we just mobilize this lesion. We have to remember where its blood supplies and where it's attached, which is really the roof of the third ventricle. So we wanna mobilize it from all its attachments laterally and on both sides immediately until we can sort of roll it out and get to its final attachment so that we get a cure. And so with sharp dissection, it'll be attached right underneath there. Little bit of tension to see where it's still attached until we can really reach its blood supply and it's last adhesion. Here see the choroid plexus of the roof of the third ventricle. And we just pull some of it forward, where we're going to cut it and get full control of the lesion. You can just see sort of that pulling and they're just separating it. And then finally getting the last little blood vessels. So that we don't have any bleeding afterwards. And with this here we can really be entirely confident that this colloid cyst will not come back. And we can see the post-op lesion is gone. This one is a little more difficult. This is somebody that had a previous surgery elsewhere and had incomplete resection of the colloid cyst. So he was 42 years old at that time. And the symptomatic recurrence didn't occur until seven years later. And that's why so many of these stereotactic procedures, et cetera, partial resection look good for quite a few years but really unfortunately predict recurrence uniformly. And so here we see this larger one, it's on both sides. So what we're gonna do is reopen, again, head is horizontal and you can see all the atrophy from the earlier surgery. We're going right down into the lateral ventricle. We see the lesion, we go through the septum pellucidum. So then we can operate on both sides. Because here now we have to worry about the adhesions that have occurred after the first surgery. So here we are just separating the wall, emptying out the cyst and with it being empty, we then have plenty of room to mobilize the wall of the cyst and bring it to the inside. And then it's sort of nice because with all that atrophy from the first surgery, you really have much more room than you usually have. And in this particular case, because of the previous surgery and adhesions, that room is a very welcome. So here we just removing the wall until it's completely out, and we have completely eliminated the cyst. And this time there will be no recurrence. And you can see the pre-op and the post-op and the cyst completely gone. This is a patient that has this cavernous malformation located here. Enlarging third ventricle. So what we're going to do here is unexpectedly, all we really need to do is enlarge the foramen of Monroe. Again, you see the bone is off across, you can see the sinus being pulled over to give us that extra room. Now we're gonna go through the corpus callosum and we're gonna go to the foramen of Monroe right here. We see the choroid plexus and that shoots a pathway to take us right where we wanna to go. And now we're looking through the foramen of Monroe and we're looking right at the lesion, it just couldn't be nicer, fortuitous. I wasn't sure that I would get by with just being able to operate through the foramen of Monroe, but in this case that was possible. So that's all we needed to do. We enlarged the foramen by just going along the choroid plexus, right by the veins. There are some that say you can take thalamostriate vein, I have not done so as I've had bad experience with taking veins in other locations. But certainly when you're forced to, that may be an option. But here again, you can see we're just holding over the vein and we're just taking out the cavernous malformation in a piecemeal fashion. Until it's gone, again horizontal, not a very big, no retractors required. And you could see the post-op, the lesions nicely gone, still some of the hemosiderin in the bed of the lesion. And here you can see a classic incision for the anterior approach for a incredibly difficult cavernous malformation occupying the entire third ventricle. But as you can see it extending up and severely disabled. So this is where we wanna go, that's the incision. And here's the opening. Here we're using a retractor to hold over the corpus callosum. I am not against retractors. I just don't think we ought to be using a retractor as the first step without first determining whether we really need it. So here the corpus callosum has been opened. Retractors used to pull up the corpus callosum some, and you immediately see the cavernous malformation sticking out really through the foramen of Monroe and enlarging of the foramen, so we can just go right to it, shrink it and keep removing it. And utilizing whatever is required to get it out in a piecemeal fashion. And this one is obviously so attached to everything that we have to take our time in order not to hurt the hypothalamus or the chiasm and infundibulum, et cetera. But I think you can see the piecemeal removal of this lesion and then we just roll the cavernous malformation from side to side, separating it, utilizing these non-stick bipolars. And then just really rolling it up. Now, we're looking at the bottom of the third ventricle, love these nonstick bipolars, and you can see how the tumor is being removed, piecemeal fashion. And the classic appearance of a cavernous malformation, going on the other side, just for more room, being able to see until we really remove it all. Luke, we can go onto the next slide. And here you could see the lesion removed, very difficult case, and you could see continued with a short-term memory. And obviously we hope that that returns. And as I recall, the last follow-up a year later he was really much, much better. This is an interesting case because we now have a thalamic lesion that's impinging on the third ventricle, and this doesn't enhance. And the patient is really intact neurologically, but the lesion has enlarged. So between the neuro-oncologist and the patient and ourselves, we offered him surgery and here we're coming down to the lesion, that's really our goal. And that's how we get to the thalamus, we open right where the lesion is. And again, you have this classic appearance of the low grade tumor that has relatively sharp margin as opposed to the more malignant gliomas. So these low grade gliomas really have a very sharp edge and we can dissect around it, very much similar to the hematoma. You can see the gelatinous appearance of the tumor itself, a very tough tumor, very gelatinous, but very firm. And so again, utilizing our various instruments until we got it all out. And here, you could see where it was. And it really came out very, very nicely and no change in the neurological exam. This is an interesting patient that sent us a colloid cyst. But as soon as you look at the imaging, you can see that it's not a colloid cyst. And with this darkness and suggestion of hemosiderin, this was obviously a colloid cyst. Now more difficult is, it sitting on the roof of the third ventricle. So this is not one you can take out through the foramen. So again, we're gonna go through the corpus callosum and then go transchoroidal. Patient is horizontal, bone is taken across the midline. Gravity is used to allow the ipsilateral hemisphere to fall away, going down to the corpus callosum, opening into the third ventricle foramen of Monroe. And now we're cutting along the lateral margin of the choroid plexus. And the whole point of that is to protect the fornix. We're keeping that as a buffer to help protect the fornix. Now we're looking inside the third ventricle, the roof, and now we're cutting, utilizing the little CO2 laser holding up the venous structures while separating the cavernous malformation from the roof of the third ventricle and keeping the normal anatomy intact. And here the lesion is out. And if we look at the post-op, it's beautifully gone. More difficult is this young man who's a lesion is really at the backend of the third ventricle extending into the aqueduct. You could see third ventricle and lesion here. So when we look at it, you see it here. And so we're gonna open just like we did for the previous one, go through the corpus callosum and now down under the third ventricle and in the third ventricle, we slide down until we see the cavernous malformation. Just separating the walls of the third ventricle to get more room, utilizing the suction on the sucker and there we're getting to the aqueduct and there's the cavernous malformation sitting right at the entrance of the aqueduct in the posterior third ventricle. And then very carefully, we remove the lesion in piecemeal fashion, obviously way down deep. And again, the same technique. We can go onto the next slide, please. And when you look at the post-op, this is pre-op, that's post-op gone, pre-op, post-op. This is a gentleman who was in surgery with one of my colleagues when they encountered significant bleeding and asked for some help. And I came in, we controlled the bleeding and as we're looking at the lesion, again, horizontal off, this time we're coming in posterior interhemispheric. You can see where we're coming in from this angle. That's how we'd approached it. And as we look at this lesion, we recognize really that it turns into a cavernous malformation and we mobilize it and it's attached to the deep venous drainage system which you'll see. And here by using ICG, we can recognize some of the deep veins that we obviously have to preserve. So we keep going around the lesion. We now have it under a good control, bipolar, all the feeding vessels and then just remove it in a piecemeal fashion until we've only left behind the small attachment to the deep veins. Because the last thing you want to do is compromise the deep venous system. And we can take that out again in piecemeal fashion, we can go onto the next slide. And here's the pre-op and here's the deep venous system and the attachment to the deep venous system and the remnant of the cavernous malformation we left attached. This is a 18 year old college student who had progressive memory loss. And you can see this cavernous malformation occupying the entire third ventricle and what our plan is, is really to go posterior interhemispheric, the rationale for that is because the fornixes have split apart, so we don't really have to worry about them. And we go, and in between here, you see the faux, we use tool retractors to get us down between, in order to enter the third ventricle posteriorly through the splenium of the corpus callosum, tela choroidea and right underneath, we will see the cavernous malformation. And there it is, very bloody cavernous malformation. So we have to be particularly careful. But remember, as I said, the bleeding from a cavernous malformation is always venous. So Tampa nodding judiciously really controls the bleeding at all times. And piecemeal just keep going. The whole goal here is to find an edge of normal anatomy, which we then will utilize to bring the rest of the cavernous malformation into the cavity we've created, the space we've created. But you can see how this is much more bloody. We're sucking the blood and now we can see anteriorly, we just saw the third ventricle, and this gives us a very nice anatomical landmark to allow us to remove the rest of the lesion. And here are the lesion is gone and he did very well. And then finally the supracerebellar approaches. Here we have a lesion that is pretty straight forward, obviously a teratoma, probably a mixed teratoma, progressive symptoms. And here we're going through a midline, supracerebellar infratentorial approach. And these tumors have so many different components. Some of them are soft, some of them are like a dense rubber and have to be cut. And here we're using scissors to take out a component of the tumor and we just keep taking out one piece after the other. Top of the head is here, feet are up here. My attempt to draw a foot up there and head up here, and again, we just take one step at a time, keep removing, keep removing, it's the normal anatomy that counts that tells us where we are. And here we are rolling the rest of the tumor, looking into the third ventricle, always counter traction, sharp dissection. And you can see the size of this tumor, but it really comes out very readily until it's all gone. This is third ventricle upfront, and here the lesion is completely gone. This is a gentleman that had previously been operated through an anterior temporal approach with this cavernous malformation. If you look here, you could see that one approach might be to come through a lateral supracerebellar infratentorial approach and that's what we did. You could see it's off the midline as opposed to the last case. Don't need a very big incision. You just come in underneath the tentorium. And so here, we're using a small patty. We see the tentorium, we have to cut the tentorium because we need to go up, our angle has to be up because this lesion goes up so far by the third ventricle. Remember that the fourth nerve is under the arachnoid, so as long as you're staying X to arachnoid, you can safely cut the tentorium. So shrinking it back a little bit with bipolar coagulation, looking into the ambient cistern, and then with image guidance, we make an opening in the medial meniscus and we go through and there's the cavernous malformation. So a very small opening gets you right to the lesion and we can really remove it very readily. We can go to the next one. Same technique for taking it out. And here he is post-op, the lesion is completely gone. So he had another scan four and a half, oh, here it is four and a half months later. And his referring neurosurgeon says he's now able to ambulate independently with much better balance. So a very nice result for a very difficult cavernous malformation. And then this is a little baby that was referred to Lunsford to Doug for a radiation. And he referred her to me. She'd had a shunt placed and then had another bleed. And here we are top of the head, feet are up there, cerebellum right there. So here we're opening again, the tentorium. This one here really, that lesion is very high up on the edge of the third ventricle. And so our angle is going to be very steep to get to where we need to go, right up by the quadrant germinal plate, right up by the confluence of the veins, the arachnoid is always thicker there but once we're there using image guidance become right down to where we wanna go, right down to the lesion itself from the lateral supracerebellar approach. We get into the cavernous malformation and that allows us really to remove it piecemeal. And you can see the size of the lesion and you can go ahead to the next one. And you can see post-op, the lesion is completely gone. We got a beautiful look into the third ventricle. The shunt was removed and the patient made a complete uneventful recovery. Last case I wanna show you here is really a very, very difficult one. You could see it all here, third ventricle. You can see occupying the entire third ventricle all the way up to the foramen of Monroe. A young lady from Europe and you can see the angle, extreme lateral supracerebellar approach, supracerebellar infratentorial approach. We're right along the lateral sinus. I'm getting down to the tentorium. We'd cut the tentorium because we have to have go all the up toward the end of the foramen of Monroe. We decide our entry point based on imaging, going right to the center of the lesion as you could see here. And once we're there, we then take it out in a piecemeal fashion one step at a time. Same technique as I've shown you before. Next, took a long time to get this out. Obviously it was so large. But here we are all the way up with image guidance, all the way up to the foramen of Monroe and that's the post-op, lesion is completely gone. And a week later she returned home. These were with their permission. We wrote an article that really outlined the various approaches to these regions of the thalamus. It's in the Journal of Neurosurgery but you can see just like a showed you even all these lesions are very, very close together. They all require a different approach for safe removal. So in conclusion, third ventricle lesions are accessible. You have to really be aware of all the multiple routes that are available to you. Anatomy, anatomy, anatomy, and with that, you can really get a good result, thank you.

- Very illuminating, Dr. Spetzler as expected. Truly a masterpiece as always. Two things I wanted to ask you. One of the variations that has really worked with me and is very flexible, is I enlarged the foramen of Monroe by coagulating and cutting the central vein. Never had an issue, have done it more than probably 50 times. It really mobilizes the thalamostriate vein, you can do barely or a little bit of a intercloidal dissection and you can almost get all the way to the posterior aspect of the third ventricle. Do you have any feelings about that approach?

- Yeah, I worry, no, that's perfectly reasonable and I know that's been done and I've certainly taken the septal vein, but you still have to worry about the fornix.

- Absolutely.

- And if it's hanging in the breeze there and I have incredible respect for the fornix and that's why I like to stay away from it.

- No, I do exactly how you do it based on what to learn from you. I leave everything on the fornix. I've seen terrible complications and as much you can stuff leave on the fornix, it's critical, the respect for the fornix can not be underestimated. Number two question I have for you is that the cavernoma you showed into the aqueduct. What I have done in one instance is that I have gone in the raphe between the tectum. I know the tectum is normal, I have gone between the raphe, made a small opening, lateral supracerebellar. I never do midline supracerebellar anymore. And through the lateral supracerebellar approach, I've been able to do that. The patients have some obviously extraocular movement abnormality for six weeks but they go away. Have you ever tried between their raphe when it's normally 100%?

- Yeah, I have not, I have not gone through the raphe. I've considered it certainly like for that case, I just wasn't sure enough whether we would have temporary visual problems, but if you say you can get away with that, then that's really a little more straightforward approach and I'm not at all upholstered.

- Yeah, I have gone to the way you showed it multiple times, it's just that patients wake up and the recovery is protracted. Obviously it's very long approach, it's very far posterior third ventricle into the aqueduct, a lot of transcortidial dissection, there's no way around it. And in those cases I have forced the issue to go posteriorly. But again, nobody can know because we don't have enough patients to compare. So I can reliably tell you that's a better approach.

- I'm a firm believer that there are many roads to Rome. You have to travel the one that you think is safest and most efficacious.

- I cannot thank you enough for being such an incredible mentor for so many of us. Thank you, thank you, thank you again for making the time.

- Thanks.

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