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Large Third Ventricular Tumors without Suprasellar Extension

December 11, 2015

Transcript

This video demonstrates the far reach or maximal reach of the endoscopic transnasal Transsphenoidal approach for resection of large and predominantly third ventricular tumors without any significant suprasellar extension. This is a patient who presented with bilateral visual dysfunction, and on MRI was noted to have a large, predominantly third ventricular, heterogeneously enhancing lesion with minimal extension into this suprasellar space. The location of the chiasm is apparent at the tip of my arrow. Therefore the operative space to reach this tumor is through the retrochiasmatic space. The tumor extends all the way to the foramen of Monro. The transnasal trajectory offers an excellent opportunity to remove this mass along its long axis. However, the space to work through is extremely small. Importantly, the stock is intimately associated with the capsule of this tumor, and no matter what route is used. In other words, the trans is sub-frontal or the transnasal approach, the risk to the pituitary stock is significant and its sacrifice is highly likely. I decided on a transnasal approach. I do want to emphasize that if the tumor is highly fibrous, its removal through such a small operative corridor can be quite challenging, and if not, impossible. Here's the optical carotid cistern. This is the protuberance of the carotid artery, the bone over the optic nerve. Similarly, on the right side, this is the optic nerve and the optical carotid recess with the carotid protuberance being present over here. Here is the sellar. For resection of tumors through the expanded transnasal approach or tumors within the parasellar area, I often remove only the bone along the anterior aspect of the sellar and preserve the bone over the posterior aspect of the sellar. As further removal posteriorly is unlikely to help with the working angles. So I will go ahead and remove the bone over the interface of the sellar, the tuberculum and part of the planum to provide additional and maximal space to handle this tumor. bony removal will be extended all the way to the optic foramen bilaterally, and to the lateral edge of the carotid arteries. An osteotome, a small one, is used to remove bone first, and then create a window where drawers can remove additional bone. Here's the anterior intracavernous sinus. bony removal continues on the left side all the way to the level of the optic foramen, but the foramen is not opened. Here's the bone all the way to that right side of the carotid artery to the left side of the right carotid artery. Maximizing bone removal is critical for removal of such a large lesion through a small intradural trajectory. Bleeding from the cavernous sinus is controlled via flow seal and gentle tamponade through the use of a small car catenoid to seal the area, the hemorrhage from the cavernous sinus. Here's the bony removal over the plenum and to tuberculum sella. Here is bony removal just along the anterior half of the sellar. Dural opening is conducted in a sharp fashion and a cushioned fashion. Posteriorly, the dural is open all the way to the level of the pituitary gland. The arachnoid membranes are generously opened. Here, you can see the chiasm and the pole of the tumor within the retrochiasmatic space. All the arachnoid membranes and bands are dissected so the normal anatomy can be thoroughly appreciated. Here are the A2 branches and the Acom. Here's the pole of the tumor. As expected based on preoperative imaging, the stock is quite adherent and involved with the inferior pole of the tumor. I initially attempted to preserve this stock via its dissection, but as you can see in this image, the stock is quite adherent and the tumor has infiltrated its superior sections. I continue to attempt to mobilize the stock toward the left side. In addition, I try to only partially transect the stock with a hope of preserving the neuroendocrine axis as much as possible. I go ahead and open the capsule. Here's the partial transection of the stock, with the hope of mobilizing this stock more toward the left side. The inspection of this stock at this level demonstrates that the stock is again intimately involved with the inferior pole and its preservation is impossible. Sharp dissection is used to open the inferior pole of the tumor. Here's the stock is essentially moved to the left, but most likely is not functional. Here's the capsule in the tumor, mobilized into the resection cavity. I decided to go ahead and transect the stock as its preservation would be impossible based on the anatomy we just discussed. Next step involves aggressive de-bulking of the tumor using reincarnates of various sizes. This is a key step to allow the superior pole of the tumor to descend into the resection cavity. I continue to deliver tumor piecemeal. Now the tumor demonstrates its vascularity. Aggressive coagulation is avoided. As much of the tumor as possible is de-bulked to facilitate capsular dissection during the next step of the operation. Now, the angled endoscope is used so that I can more aggressively dissect the tumor close to the periphery of the capsule within the tumor. This direct visualization using angled endoscopes minimizes the risk of violating the tumor capsule and placing the walls of the third ventricle at risk. Now that the tumor has been highly decompressed, I dissected tumor from the posterior aspect of the chiasm and floor of the third ventricle, including hypothalamus. This vessel later proved to be a tumor-fitting artery or arterial, and was sacrificed. Here is a more angled endoscope allowing visualization underneath the chiasm and dissection of the posterior aspect of the chiasm from the tumor capsule. The tumor is highly adherent, as you can appreciate, especially at one point at the tip of the arrow to the floor of the hypothalamus and the posterior aspect of the chiasm. This adhesion was transected, as you can see here, releasing part of the capsule and allowing its mobilization inferiorly. The goal is here to remove the anterior capsule piecemeal to facilitate the descent of the superior pole of the tumor, close to the foramen of Monro. You can see the tumor-feeding vessel that is being coagulated and sharply cut, so the wall of a capsule can be mobilized more efficiently. Gentle elevation of the chiasm is well tolerated in my experience. Two-handed dissection allows dissection of the capsule away from the hypothalamus. The transnasal route does allow the use of techniques used via the transcranial routes for dissecting the tumor capsule. Here's the tumor hypothalamic interface that is being dissected through the bimanual technique. A 30 degree endoscope is ideal during performance of such maneuvers. Now I'm exploring the suprachiasmatic space for another operative trajectory to manipulate the superior pole of the tumor. As you can see, the A2 branches are not providing any additional space to work through. And just to the left side of these vascular structures, there is normal frontal lobe. I therefore concluded that my sole operative trajectory would remain within the retrochiasmatic space. Here's the use of the angled ring curettes to mobilize the capsule into the resection cavity to allow its piecemeal removal. I gently pull on the tumor capsule, identify the surrounding neural walls, facilitating piecemeal removal of the tumor. Again, the oozing within the operative field is handled via frequent irrigation rather than aggressive coagulation. Here's the right side of the tumor, which is more mobilizable. There are a number of veins on the tumor capsule that lead to bleeding. Here's the key step to move the tumor into the resection cavity and go over the pole of the tumor to reach its superior pole. I'm hoping that I have reached adequate tumor de-bulking to reach the tumor capsule superiorly. There's still some tumor remaining. I'll continue to mobilize the tumor along its lateral aspect. This is quite labor-intensive. The angling instruments are quite effective. By the inferior aspect of the tumor has to be aggressively de-bulked for one to be able to reach the superior pole. The lateral tumor capsule is being mobilized and dissected into the resection cavity. Under direct vision, the capsule is being transected. At this region, continue the persistent dissection maneuvers to dissect the capsule laterally so the superior pole of the capsule can be reached. Some of the venous bleeding is tolerated. Here's another significant piece from the lateral side that is being delivered. Here is my initial attempt to go over the superior pole of the tumor. There is evidence of CSF egress, which is quite encouraging that the superior pole of the tumor is nearby. Here's the superior pole that is evident. Additional piece of the tumor is being extracted. Next, I'll go ahead and look over the superior pole of the tumor to stablish the dissection plans from the posterior aspect of the tumor capsule. This part of the tumor was relatively suckable. Small attachment from the wall of the third ventricle is being peeled off using bimanual dissection. Here's the superior pole of the tumor. Let's go ahead and look inside. Here are the bilateral foramina of Monro choroid plexus into the lateral ventricle. A 45 degree angle endoscope is used to mobilize the tumor carefully from the lateral walls of the third ventricle. This maneuver is highly technically challenging, requires significant coordination of bimanual dissection, but it is possible. Here is additional removal of the tumor piecemeal. The capsule is being gently pulled into the resection cavity. Here is a band between the third ventricle wall and the tumor capsule that will be released momentarily. Here's that band there, after which I should be able to get a good portion of the tumor mobilized into the resection cavity along the posterior capsule. Using the angled dissector, the posterior pole is mobilized away from the aqueduct. Some of the bleeding is tolerated. Now that the dissection is more complete, larger pieces of the tumor can be delivered. Here's the portion of the tumor, more inferiorly there being extracted. This part is not really suckable. Here's a larger piece that was not possible to remove through the one nostril without adequate visualizations through the nostril. Therefore, the endoscope is being placed into the ipsilateral nostril, so the tumor can be maneuvered through the nasal cavity and carefully removed without residual tumor within the nostril. Here's looking back into our resection cavity and the third ventricle. There is large blood clot that has to be removed. Again, during the entire procedure, the blood pulled posteriorly. Here is this very large clot that is being delivered. It is very important to investigate the cavity and to clear these clots. Here is the resection cavity within the ventricle. You can appreciate the aqueduct. The walls of the third ventricle are relatively intact. There is no residual tumor in this area. Next, I'm going to investigate the more inferior posterior aspect of the cavity. You can see some residual tumor. Angled ring curettes are quite effective again for removal of the tumor in this area. The tumor is pursued until the membrane of Liliequist over the posterior circulation is evident. A larger angled ring curette is necessary to completely remove the tumor. Here's that larger ring curette that is being carefully maneuvered during the resection without injury to the surrounding cerebrovascular structures. Here's one of the last pieces of the tumor that's delivered. Ample amount of irrigation is used to irrigate the resection cavity to achieve hemostasis and clear any debris. The closure is standard. A piece of allograft dura is used to obliterate the subdural space. The age of the allograft are inserted within the subdural space. This layer of closure, by itself, can be quite effective as long as its well placed. The optic nerves have to be carefully protected. So they're not significantly compressed. Doing reconstruction of the skull base. Frequently, the highest risk of hemorrhages along the anterior aspect of the reconstruction. The resection cavity was further inspected to assure no evidence of a clot before further closure is completed. Here you can see valsalva maneuvers demonstrate a reasonable initial inlay closure. Next, another piece of allograft dura is laid over the bone. A piece of prosthesis is used to complete the gasket seal closure. This prosthesis is counter-sunk along the edges of the bone while staying away from the optic foramina to avoid any compression injury to the nerves. The prosthesis is rotated to assure a good seal along the inferior aspect of the closure Here's their countersinking maneuver. Further inspection reveals no evidence of significant defect in our reconstruction. I'm quite satisfied with this closure. The nasal septal flap is also rotated. This flap was obviously harvested at the beginning of the procedure. All the edges are carefully placed to be in direct contact with the surrounding mucosa and the bone. This is a postoperative MRI immediately after surgery, which demonstrates gross total resection of the mass without any complicating features. This patient had some mild memory difficulty after surgery, which cleared at six months follow up. Again, the final pathology was consistent with spindle cell oncocytoma. Thank you.

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