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Complex Petroclival Meningioma: Posterior and Anterior Petrosectomies

Transcript

- [Instructor] Let's review the combined anterior and posterior petrosectomy for a complex, giant petroclival meningioma and describe all the challenges associated with performance of this procedure. This is a 30 year old female who presented with gait imbalance and third nerve palsy. As you can see, there's a large meningioma centered over the petroclival junction. There's also invasion of the tumor into IAC, significant brainstem compression is apparent, cavernous sinus is also filled with tumor, obviously this part of the tumor is in accessible and not safe to remove. Looking at T2 images, you can see a fair amount of edema within the brainstem and this is an ominous sign. This tumor is most likely invading the pia and gross total resection is not possible. We'll confirm this finding within the video as well later, as you see that we were unable to find clear planes between the tumor capsule and the brainstem, therefore from all the findings based on imaging, this tumor can only be subtotally resected. This is a coronal enhanced image, you can see again, invasion of the cranial base foramina by the tumor. There is minimal amount of calcification. The basilar artery is also encased by the tumor. Obviously, we have to pay special attention how the tumor is interacting with the perforators of the basilar artery. But based on what is seen here, most likely perforators are encased by the tumor as well. Here's an angiogram, a preoperative one, demonstrating displacement of the basilar artery and its stenosis by the tumor. You can see that posterior cerebral artery is also elevated and draped over the superior pole of the tumor and SCA is also significantly affected by the tumor as well. This patient underwent a... Supine position is evident. A lumbar drain was placed before placing the patient in the final position. The position of the pins are apparent. The incision, starting from the huda zygoma and also curving behind the ear. Facial monitoring was also used, as well as somatosensory evoke potentials and motor evoked potentials. This is the position of the patient during the second stage of the operation. You can see the position of the head is slightly different. I tend to stage these operations into two phases. During the first day, we complete the exposure and some of the early stages of dissection of the tumor, and we often stop around 5:00 p.m. and then restart the next day for final resection of the tumor. Critical part of the operation are those last hours where the tumor has to be dissected from the cranial nerves and brainstem and I would rather perform those stages early in the day, rather than being fatigued from a long day from performing the exposure and initial stages of the operation. The head is placed in a skull clamp and during the second stage, since the focus of the dissection is primarily toward the brainstem and medial structures, the head is turned slightly toward the floor and also tilted toward the floor to be able to provide an inferior to superior trajectory without significant retraction of the temporal lobe. Initial stage of the operation. While the posterior and anterior petrosectomies are completed. Scalp flap is reflected in one layer and temporalis muscle is dissected. Next to temporalis muscles is reflected inferiorally, suboccipital muscles are also mobilized using monopolar cautery and the tip of mastoid bone is found. I prefer to do the mastoidectomy first, rather than the craniotomy. This sequence of events allow me to identify the venous sinuses and critical structures before the craniotomy is completed. Here's the sigmoid sinus, transfer sinus. The dura of middle fossa. Next, a craniotomy was completed. Here you can see the bone over the presigmoid dura. In this case, the bone flap was elevated in two pieces, one for this supratentorial space and one for the infratentorial space. You can see good exposure of the sinuses and their preservation. Drainage of CSF through the lumbar drain significantly assist with decompression of the dura and making sure that the sinuses and dura are not torn during elevation of the craniotomy. Mastoidectomy. We'll go ahead and complete an anterior petrosectomy in this case. The edge of the bone over the middle fossa is drilled away. This semicircular canals are skeletonized. Here you can see the internal auditory canal. These semicircular canals. Next, the dura over the posterior fossa is incised. The incision is extended to be over this superior petrosal sinus. Here's the dural incision along the temporal lobe, parallel to the floor of the middle fossa. Obviously, vein of Labbé is protected. And the superior petrosal sinus is again, isolated. Here you can see the vein of Labbé that has to be carefully protected and released if necessary. Again, superior petrosal sinus that has to be clip ligated. Obviously, we wanna stay anterior to the insertion point of the vein of Labbé. Again, tentorium. Where clip is used to ligate the superior petrosal sinus. The tentorium is cut parallel to the posterior edge of the petrous bone. You can see the micro scissors being used. Tentorium has to be coagulated periodically, especially in the case of meningiomas. Where the tentorium is hypervascular, you can see some of the tumor already apparent. The fourth nerve is protected along the medial edge of the tentorium. You can see the tumor, tentorium, again, the tumor supratentorially. Here's the tentorium, it's completely transected and you can see the depression of the edge of the tentorium onto the tumor. Here you can see the fifth cranial nerve. Again, the tumor is medial to the fifth cranial nerve, which is expected for petroclival meningiomas that originate medial to the entrance of the trigeminal nerve. Here the tumor is debulked just above the trigeminal nerve. At this stage, I wanna feel the firmness of the tumor, it's vascularity and how suckable it is. It's relatively vascular. A primary goal at this stage should be devascularization of the tumor as much as possible from the base on the tumor and at the level of the petroclival junction. Here you can see the fifth cranial nerve entering the Meckel's cave. The tentorial cut is extended all the way onto the Meckel's cave, so the nerve is untethered and it can be manipulated without significant traction on it. So I continued to work medial to the fifth cranial nerve as that's the base of the tumor and the tumor is heavily coagulated at its base. So again, the fifth cranial nerve is identified, tentorium is open all the way into the Meckel's cave to untether the nerve and then I continued to devascularize the tumor at its base, just medial to the nerve. The tumor is very firm. Somewhat adhering to the medial aspect of the nerve, but nonetheless mobilizable. Trigeminal nerve often is more forgiving than other cranial nerves in regards to it's tolerance for manipulation. Again, the tumor anterior to the nerve is being mobilized. Creating this space is critical for the subsequent maneuvers necessary to remove this very immediately located tumor. Seven and eighth cranial nerves should be located just about here. Then I continue to mobilize the tumor, now you can see a gush of CSF, which signifies that I'm getting close to that lower pole of the tumor where the seven and eighth cranial nerve would be apparent. Again, using the ultrasonic aspirator is critical for a dramatic decompression of the tumor. Here you can see the seven and eighth cranial nerves just draped lateral and inferior to the tumor pole. The tumor is being dragged into the decompression cavity and heavily coagulated, so the capsule is firmer after its coagulation and more easily manipulated by the suction and bipolar forceps. Now, we go again, move above the trigeminal nerve and see how much we can mobilize the tumor from the cerebellum and the temporal lobe. The initial stages, at least demonstrate that the tumor is dissectable. Again, we're still in the first stage of the operation when the exposure is complete and the initial stages of dissection are being carried out. This cycle of mobilization, decompression, coagulation are continued until the tumor bulk is reduced. Unfortunately, the entire base of the tumor is not accessible for its complete devascularization and therefore bleeding during enucleation will continue for a fair amount of time during dissection and decompression of this tumor. However, this the sensory branches were carefully protected. You can see I'm sacrificing the motor branch of the trigeminal nerve, however, preserving all the sensory branches as much as possible. Again, remaining within the tumor capsule, gently, I'm also finding the tumor and removing it. Here you can see the brainstem along the lower capsule of the tumor. Tumor appears to be very adherent to the pia and it's not easily mobilizable, this was expected based on preoperative imaging studies. Here you can see the tumor very adherent to the lateral pons. Again, here is the trigeminal nerve. Coagulating the capsule and keeping it away from the brainstem. This gives me an idea of the difficulty of this procedure during the second stage of the operation. Here you can see the result at the end of the first stage. Closure was completed. Here the stage two, next day. Patient remained intubated overnight in the ICU. Here is the carotid artery, the exposure via the subtemporal approach. You can see the anterior order of the tumor. Here you can see the middle fossa dura, the anterior edge of the base of the tumor, temporal lobe, very adherent to the brain. Go ahead and devascularize the tumor. Edge of the tentorium. Again, the key part is first devascularization, then decompression and next mobilization away from the neurovascular structures via sharp dissection as much as possible. You can see the brainstem. Continuing dissection along the tentorial edge. Protecting the brainstem, the perforators. Here's the medial edge of the tentorium. I cannot appreciate the fourth cranial nerve, however, the tumor is aggressively devascularized along the tentorium as much as possible until the pia of the brainstem is identified. You can see how I'm using the bipolar forceps as scissors until carefully, the pia is encountered on the other side. Here's the third nerve actually. You can see the third nerve entering the cavernous sinus. That's why one has to always watch for nerves and arteries during the entire process of dissection, as that nerve just appeared within the tumor mass unexpectedly. We continue to decompress the tumor and again, mobilize as much of it as possible. You can see a branch of most likely posterior cerebral artery. Here you can see, again, the tumor as it's been devascularized. It's bleeding much less. You can see a perforator, it's very adherent to the superior pole the tumor. I use a round knife to be able to dissect the artery, initially it appeared that I'm successful. Most of the tumor away from the artery, however, the artery appears more and more engulfed by the tumor. Here's the third nerve, very much adherent to the tumor capsule as well. Please note the technique of the round knife for dissection of the tumor capsule away from the artery. At this stage, you'll see some bleeding from the wall of the PCA or at least one of its branches. I wanna illustrate the technique for managing the bleeding here. The artery obviously should not be coagulated to retain hemostasis, but rather, first a segment of the artery is isolated and a piece of cotton soaked in thrombin is used to cover the defect within the wall of the artery, as this defect is very small. Gentle pressure and a little bit of patience often controls the bleeding very adequately while preserving the artery. Further attempts at isolating the artery appeared unsuccessful. A piece of tumor had to be left behind over the artery. I periodically bathed the artery in a piece of gel foam soaked in papaverine to make sure that the artery does not undergo vasospasm. Here is the superior pole of the tumor, just along the midbrain. A piece of cotton was used to mobilize the midbrain away from the tumor while protecting the pia of the midbrain. To be able to mobilize the capsule away from the midbrain, the tumor was decompressed and the capsule was mobilized away from the neurovascular structures. Here you can see the technique of grabbing the arachnoid bands and then mobilizing the neurovascular structures away from the tumor capsule. Here's the third nerve, very adherent to the tumor capsule. I use high magnification and gentle dissection to see if the nerve is salvageable. I can see it's very much draped over the tumor and is very thin. You can see a piece of tumor that was preserved over the PCA to protect the vessel. Here again, grabbing the arachnoid bands of the third nerve, mobilizing the nerve and protecting the nerve as much as possible. An angled pancake dissector may also be used to gently hold the nerve away from the tumor. Number of various fine micro ball tip dissectors can be used for dissecting the arachnoid bands between the nerve and the superior capsule of the tumor. Here is the round knife, again, trying to create as close of a space to the nerve without placing the nerve at risk. Here is using the micro forceps to just handle the arachnoid bands of the nerve without manipulating the nerve itself. This is most likely the least traumatic way of handling the cranial nerves. Here you can see the nerve completely intact anatomically. The tumor capsule is being mobilized away from the third nerve and the brainstem. Now you can see, again, the brainstem. Third nerve here. We'll continue to protect the neurovascular structures. You can see the basilar artery. Unfortunately it appears very much encased by the tumor. I try to at least attempt dissection of the artery to see if it's possible to remove as much of the tumor as possible. Here is the basilar artery. Most likely this is the basilar bifurcation. The superior cerebellar artery is embedded within the tumor coming towards me and I have to be very careful to protect the vessel without transecting it during the dissection. Here you can see the PCA, the basilar bifurcation. You can see the branch of PCA very much encased into the superior pole of the tumor. I'm completely convinced that complete resection of the tumor is impossible, therefore, the tumor has to be aggressively debulked to make the tumor more amenable to proton therapy after surgery. Here is below their trigeminal nerve where I will attempt to devascularize the tumor from the dura of clivus. You can see the tumor has invaded the dura of the clivus, again, making it not resectable. I have to leave part of the tumor within the dura of the clivus. Any devascularization of the tumor will minimize its recurrence in the future. Here again is the basilar artery, the tumor is behind the basilar artery, which is very unfortunate, because that signifies that these perforators are very much engulfed by the tumor and the perforators cannot be salvaged if the tumor has to be aggressively removed. The brainstem is decompressed as much as possible. One has to be very careful and not run into the perforating vessels that are engulfed within the tumor. Again, here is the lower pons. Seventh and eighth cranial nerves are here. I'm making a final attempt to make sure if the tumor capsule can be mobilized away from the brainstem, however, the tumor is extremely adherent and again, debulking appears to be the most reasonable strategy to handle this tumor. Here is above the fifth cranial nerve along the brainstem, you can see the tumor capsule has invaded the pia and therefore, any attempt to mobilize the tumor away from the brainstem led to venous bleeding from the pial surface of the brainstem. Here again, you can see brainstem, the tumor capsule, significant adherence and invasion of the pia confirmed one more time. I'll try to deliver as much of the lateral capsule of the tumor into their resection cavity while minimizing the invasion of the pia. There's a cotton that is used to protect the pia from the suction force. Additional pieces of the tumor more laterally, are debulked. Again, the goal is maximum decompression of the brainstem, working on both sides of the trigeminal nerve. Again, you can see some bleeding from the area within the tumor. I'm not sure if it's a tiny perforator versus tumor feeding vessels. At this juncture, I feel it's proper to stop and do not remove additional tumor. Here you can see the third nerve, PCA, the brainstem, a sheet of the tumor that was left behind over the brainstem. This is the tumor affecting the cavernous sinus and the dura of the clivus, as well as anterior. And it's the most lateral aspect of the cavernous sinus. Here's the final result. You can see decompression, fifth cranial nerve. Closure was completed based on the details mentioned in the chapter of the Atlas. Post operative MRI revealed aggressive resection of the tumor within the middle fossa and anterior aspect of the brainstem, as you can see here. Here, we're able to go all the way across, find the artery. A sheet of tumor was left on the brainstem. A fair amount of tumor had to be left behind, going into the cavernous sinus along and into the dura of the clivus. Here again, you can see the tumor that corresponds to the tumor on the T2 weighted images here, and this patient subsequently underwent proton therapy. Post-operatively, patient had some worsening of her third nerve palsy, however, eventually made an excellent recovery. Thank you.

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