Thalamic AVMs and the “Commando Operation”
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This video describes techniques for resection of thalamic arteriovenous malformations along the left medial wall of the third ventricle. It also details the technique for Interhemispheric Craniotomy and demonstrates the so-called commando operation for premature intraoperative rupture of this AVM. This is a young patient with history of intraventicular hemorrhage related to this left thalamic arteriovenous malformation. The CT angiogram demonstrates a relatively small arteriovenous malformation along the medial wall of the third ventricle on the left side. The majority of feeders are originating from the P one branch, and are the thalamogeniculate perforators. These three or four dominant feeding vessels, feed the AVM that drains through a large internal super vein, joining the vein of Galen. And angiogram demonstrates the angioarchitecture of this malformation on the AP vertebral injuction. You can see the malformation and its draining vein pointing medially and then posteriorly as expected. And the lateral over to point injection demonstrates the three large dominant thalamogeniculate perforating vessels originating the P one, feeding the malformation. Let's review some of the details for operative planning. This is the angiogram. When the patient initially presented with an intraventicular hemorrhage and underwent external ventricular drain placement. You can see there are two large draining veins just along the posterior aspect of the frontal lobe that have to be carefully protected during placement of the craniotomy. This malformation is relatively posterial along the wall of the third ventricle, and therefore the craniotomy should be placed as posteriorly as possible while preserving these large draining veins. Therefore, the operation was conducted using intraoperative image guidance, using a CT angiogram for guiding the route of surgery. The patient was placed in a lateral position, a supine position is as good. However, the head should be placed parallel to the floor of the floor with the sagittal suture being parallel to the floor. The head of the patient is turned 45 degrees away from the floor. Neuronavigation is used to localize the large draining veins. The sagittal suture is marked, since this lesion is relatively deep and is close to the midline. And ipsilateral left hemispheric approach was chosen and relatively small incision is adequate to reach this very deep lesion. A lot more drain was used to decompress the hemisphere early during surgery and allow a smooth dissection or within the interhemispheric space. This video goes through essentially every detail of the operation. The initial burr holes are placed over the superior sagittal sinus to allow the exposure of the sinus and its mobilization during the interhemispheric dissection for a completion of the burr hole. Carousel jura is used to expand the burr hole further and safely, unroof the super sagittal sinus. Second burr hole is placed using similar techniques. The cancellous bone is removed and the inner table is exposed and removed in layers using carousel jura And alternative option is placement of two burr holes on each side of the superior sagittal sinus Here's the second burr hole placed more posteriorly and the bone is removed using carousel jura Two bony cuts are necessary to complete the craniotomy before then. A number three Penfield dissector is used to mobilize the dura and the roof of the sinus away from the bone. I drain about 30 to 40cc of CSF gradually during the process to decompress the dura away from the inner table of the bone. Thalamus gel foam is used to control epidural venous bleeding. The initial bonny cut is conducted over the left posterior frontal lobe dura. The drill cutting blade is maintained perpendicular to the surface of the bone. The second bony cut is just over the super sagittal sinus and through the contralateral side. The bone flap is elevated. Bleeding from the venous lacunaes are carefully protected using Gelfoam soaked in thrombin. We may also be used Now that the epidural venous bleeding is under relatively good control, The dura is open in a curvilinear fashion based over the superior sagittal sinus. The incision of the dura extended as close to the lateral wall of the sinus as possible. All the bridging veins are carefully protected. One or two small bridging veins may have to be sacrificed. However, the larger one, as you can see is mobilized and untethered and retracted with a dura by it. It's paced and see is preserved. Here the incision of the dura is conducted more parallel to the superior sagittal sinus to avoid significant tension on this important large parasagittal vein along the posterior aspect of the craniotomy. The arachnoid membranes just over the falx are dissect the way to allow the hemisphere to fall away under a gravity retraction. I placed two retraction sutures into the superior aspect of the falx and use these retention sutures to mobilize the sinus out of my interhemispheric working zone. This is the first suture. You can see the effect of the suture as the tension is placed over it, and how the sinuses gently mobilized away from the interhemispheric space. The second suture carries the same function. Here is the interhemispheric corridor without any retraction. This patient suffer from a previous history of subarachnoid and intraventricular hemorrhage and the interhemispheric dissection and the inter cingulate intra pial dissection was quite laborious due to significant adherence to pial surfaces at this location. Patience and high magnification, sharp dissection are both beneficial maneuvers to protect the pial membranes and avoid bleeding. The arteries within the interhemispheric space and cingulate can be used as roadmaps to maintain the interhemispheric and inter cingulate space. Small amount of venous bleeding is left alone. For the patient's coagulation cascade to control aggressive bipolar coagulation of these small venous bleeding points can lead to further cortical injury and additional bleeding. Here, you can see the artery that is being used as a roadmap to maintain the inter cingulate space. And make sure that I'm not dissecting subpial. You can see that placing the patient's head in this position allows gravity to clear the field. And also allows efficient disection along the horizontal planes. Here is, an inter cingulate branch of the pericallosal artery. We have not yet reached the corpus callosum, whose surface is quite yellow and glistening as you can see here. The difference between the cortex and the corpus callosum is quite evident. Now the pericallosal arteries are used as a roadmap to extend the interhemispheric dissection. Here is both of the pericallosal arteries that are evident. The inside to outside technique is used just like the Sylvian fissure to open up the interhemispheric corridor to reach the corpus callosum. Here, you can see the image of the neuronavigation guiding my working angles to reach the malformation. Since I plan to reach the left ventricle, both pericallosal arteries were mobilized laterally toward the right side, along with their perforating branches. Dynamic retraction is used. Two cotton balls of moderate size are placed one in front and one posteriorly to keep the inter cingulate space open and obviate the need for use of fixed retractors. Small callosotomy is performed over the center of the malformation based on our navigation data and this callosotomy extended further, according to the intraventricular findings and the location of the mass. Any epidermal veins are immediately coagulated to prevent intraventricular bleeding from epidermal veins they may not be readily controllable through a minimal callosotomy. Now the callosotomy is extended more posteriorly due to the caudal location of the malformation. Now you can see the gliotic surface and hemosiderin-laden surface of the ventricle, due to previous history of intraventricular hemorrhage. Here's an epidermal vein that has been coagulated and cut early. Here's a septal vein, the foramen of monro, the choroid plexus. These anatomical relationships confirm my entry into the left ventricle, which is the correct ventricle to approach this lesion. Here's the choroid plexus area. Transchoroidal approached is used to reach the third ventricle and this malformation, the choroid plexus is mobilized medially. The choroidal fissure is identified, and the dissection is performed in this plane to reach the third ventricle. You can see the gliotic surface. Here is the transchoroidal approach into the posterior aspect of the third ventricle, with again heavily hemosiderin-laden surfaces confirming the most likely location of the malformation. Here is the vein on the lateral wall of the ventricle that will be protected. However, as dissection continues and further anterior exposure toward the pole of the tumor is necessary. One of these veins had to be sacrificed. Here's the superior pole of the tumor and some of the feeders within the malformation that is quite evident. I'll go ahead and start my dissection along the pre-AVM gliotic region. And I try to stay as close as possible to the nidus of the malformation due to the location of this mass within very vital territory. One of the first errors during this procedure was my overzealous and enthusiastic attempts to closely hog the borders of the malformation. Retrospectively. I should have entered the third ventricle along the medial wall of the right lateral ventricle and obtain proximal control over the thalamogeniculate perforators to protect the walls of the ventricle, however, I stayed just over the lateral aspects as was the medial walls of the malformation to preserve as much neural function as possible. Here's some of the feeders along the interpol of the malformation. One of the ventricular veins is being sacrificed to allow more generous exposure to the pre-AVM gliotic region. Here's some of their feeders to the interpol of the malformation. Neuronavigation confirms my location within the entire aspect of the AVM. Here, you can see the more of a normal area along the entire aspect of the AVM. The white matter feeders can be quite daunting in this location. There are quite active because their large feeding vessels are not managed yet. The location of the avian places, the surgeon away from the perforating vessels early on during the operation here, you can appreciate the location of my surgical maneuvers through image guidance. You can see these feeding vessels and white matter feeders continue to be quite annoying. The posture of surgeon and his arms or her arms too, work is quite taxing due to the position of the head of the patient and therefore arm rests are necessary to maintain steady hands to conduct microsurgery. Reasonable control was achieved, and I continue to stay slightly away from the medial wall of the malformation. So I can avoid the pathologic walls of these white matter feeders that somewhat improve upon moving slightly away from the nidus. So this looks like relatively normal white matter. However, there is a robust white matter feeder, right at the tip of the suction. I continue to isolate this white matter feeder to hopefully gain some control over it. Here, you can see relatively normal brain. Therefore I don't find myself right into the nidus and I'm hoping this maneuver would protect me from further torrential bleeding that is difficult to control. Here's a more demagnified view. is the foramen of monro I'm trying to see if I can reach the deep feeders through the foramen. However, this was deemed not possible. Is working through the frame and entering the third ventricle. However, I don't see any obvious, deep white matter of feeders that are accessible. I like to stay around the white matter of the AVM and continue to isolate it without any control over the large feeding vessels. Retrospectively I should have persisted into the third ventricle by opening the choroidal fissure more aggressively and finding the feeding vessels earlier. Dissection along their pre-AVM gliotic surfaces continues, quite laborious. Often complicated with the white matter feeders robustly fed and supplied by the deep thalamogeniculate perforating vessels. The bleeding is becoming more and more robust and the brain looks a little bit more tense. Here's the magnified view of my working space. I try to use some gentle tampan to control some of the white matter feeder bleeding without aggressively coagulating here is entering there foramen monro, trying to achieve some sort of proximal control, however, I was again not successful. I continue stay around the malformation and to hope that by going around the malformation, I'll reach the deep white matter feeders through the P one and PCA control. The bleeding is becoming more and more problematic to control. The brain is becoming more tense. You can see my operative corridor is becoming more restricted and narrow because of brain swelling. I have to keep the working space open using the forceps. However, this proofs to become even more problematic. And I am left with extremely narrow working space due to acute cerebral swelling and tension. Leading me believe that the AVM is hemorrhaging from a location that is not visible through my operative field. Most likely through the third ventricle and into the contralateral lateral ventricle. At this juncture, I had to use a fixed retractor blade to be able to keep the operative corridor open And continue decisive maneuvers, to save the life of the patient under such extremely difficult situation. You can see the significant cerebral tension, the use of the fixed retractor blade. Now I try to reach the septum pellucidum, open the septum pellucidum to be able to remove the clot from the contralateral lateral ventricle. This proved to be more difficult than I thought. Unfortunately, there's no obvious bleeding within my operative field to control. Here, you can see additional retraction allows me to reach the septum pellucidum, with opening it, I'll be able to evacuate a large blood clot and achieve some cerebral decompression. Here's again, my suction within the third ventricle, but there is no obvious source of bleeding. Here is some herniation of the clot through the septum pellucidum that I'll evacuate momentarily. Here's the clot right about there, that is being evacuated. The contralateral lateral ventricle is entered. The bleeding is controlled. You can see the choroid plexus within this region. The walls of the ventricle relatively healthy. Now, that some decompression is attained. I have to enter the third ventricle immediately. Decisively control the feeders to the malformation Here is my deliberate maneuvers to go around the malformation, continue dissection in the face of significant bleeding until I can reach those deep white matter feeders through the floor of the third ventricle. Here, you can see the location and the depth of my reach within the third ventricle. You see the medial wall, the third ventricle on the right side, as well as on the left side, the malformation is here. Here is one of the feeding vessels to the malformation along the floor of the third ventricle that is being exposed. I continue my dissection until I'm able to reach the floor of the third ventricle and isolate the feeding vessel that is bleeding actively. I'm essentially following the flow of blood. Here, you can see a large feeder that is actively bleeding, right at the tip of the suction. These feeding lesion is more evident. Now that I can see the floor of the third ventricle. This part of the video is edited minimally for you to appreciate the steps involved with control of such life-threatening situations during the surgery, I continue to remain patient. Aggressive indiscriminate, coagulation is prohibited. The blood clot is removed. Here is that feeding vessel that was loose. That was coagulated going to the malformation here. Here's the medial wall of the third ventricle on the left side is coagulated to devascularize the malformation. This is the floor of the third ventricle. This is another feeding vessel that was evident on the preoperative angiogram. Again, the right wall of the third ventricle looks very healthy. Again, this is another feeding vessel to the malformation along the depth of the third ventricle that is being controlled. Patience, persistence is absolutely mandatory to get these feeding vessels under control. I'm more encouraged now, that the malformation is under more control. The feeding vessels are relatively manageable. Now it's time to continue to dissect the malformation and to be able to remove it. Here's the inferior aspect of the malformation that is being disconnected. Here's another feeding vessel that popped upon coagulation. However, it's not relatively under control. It's been transected and part of the malformation close to the floor of the ventricle is being mobilized away. So here's the malformation where I'm rolling it more anteriorly to disconnect it from its draining vein that you can see here. The draining vein is relatively collapsed and now can be coagulated and cut. And then this malformation can be delivered. The nidus is removed. The resection cavity is further inspected. You can see the walls of the third ventricle and the aqueduct more posteriorly. The ventricular drain is placed within the resection cavity. This is a copy of the preoperative CT angiogram. Retrospectively, when I review this case to avoid torrential bleeding and the need for a Commando operation, I should have persisted through the transchoroidal corridor and entered their third ventricular space and control the deep feeders early, rather than continuing to stay on the lateral side of the malformation and struggling with a deep white matter feeders very close to the nidus of the malformation. However, one has to keep in mind that even in the desperate moments, the surgeon has to remain composed, deliberate and persistent to save the life of the patient under such difficult situations. Postoperative angiogram demonstrated complete exclusion of the malformation without any AV shunting this patient. I will confirm the anesthesia with some optimization, but continue to improve neurologically. And at six months, evaluation has returned to his preoperative status. Thank you for your attention.
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