December 11, 2015
This is an unedited surgical video of microvascular decompression surgery for right-sided V1 pain. This patient underwent a right-sided retromastoid craniotomy as you can see here in the lateral position. I'm going to review the basic landmarks for the incision and the craniotomy. I identified the inion and the root of the zygoma and a connecting line defines the approximate route of the transfer sinus. In addition, the tip of the mastoid and the mastoid groove is identified, a vertical line parallel to the mastoid groove and through the groove is also marked. A cross between these two lines approximates the location of transfer sigmoid junction. The summit of the incision should be going through at the location where these two lines cross. The base of the incision is relatively wide. And this curvilinear incision essentially reflects the myocutaneous flap in one layer inferiorly and mobilizes the myocutaneous flap out of the working zone of the surgeon. The head is turned slightly toward the floor. You can see the location of the pins and the angle between the shoulder and the neck is expanded to improve the working zone around the suboccipital area. Here's the mmyocutaneous flap that is reflected inferiorly using fish hooks. This is the transferase's location for the emissary vein. This is the mastoid groove. We'll go ahead and place our first hole somewhere here, just above the mastoid groove and just slightly above the emissary vein. A generous burr hole is placed, a small craniectomy is quite adequate, almost less than two centimeters. Here you can see the junction of the transferase and sigmoid sinuses. The burr hole started on the dura and the craniectomy moved toward the sinus. A small piece of bone was left over the sinus to protect any significant injury to this sigmoid sinus. You can see the size of the craniectomy that is relatively small and essentially keyhole. The dura is open along the transverse-sigmoid junction while leaving a piece or a sleeve of dura attached to the sinuses. So, watertight closure can be attempted at the end of the procedure. This cranial opening leaves most of the dura over the cerebellum and protects the dura from desiccation and heat injury from the intense light of the microscope. You can see further opening placement of three stitches on the sigmoid junction and transverse sinus dural sleeves. I use a piece of rubber dam, a piece of blue glove underneath the very thin carotenoids. This rubber dam allows smooth entry into the posterior fossa and goes around the cerebellum without necessarily causing injury to the cerebellar cortex due to the rough surface of the carotenoid. A lumbar puncture was performed just before the incision was made. Therefore cerebellum is very slack. And this allows a very smooth entry into the posterior fossa and reaching the cerebellopontine angle cisterns. My first goal is to find the petrous tentorial junction. Often there is some maneuvering of the microscope to be done in order just to get the working angle right to the petrous bone right below the level of the petrous tentorial junction. You can see how the carotenoid is gonna be smoothly sliding over the cerebellum underneath my bipolar forceps. We'll go ahead and increase our magnification and get the lighting just right. So the microscope is projecting its light at the correct angle. So enough light reaches the small operative corridor in the CP angle. Here you can see a glimpse of the petrous bone. Again, the carotenoids gently advanced all the way through, but patiently. Here's the petrous bone. Here's the tentorium. And I'll go ahead and palpate the hard petrous bone and the soft tentorium and their junction. Here you can see this is soft tentorium, the hard petrous bone and their junction. And then I stay on the petrous side. It is important not to stay on the tentorial side in order to avoid any injury to the bridging veins that could cause bleeding within the posterior fossa. The superficial arachnoid memories over the seventh and eighth cranial nerves are generously opened. I used a curved micro scissor under direct vision to cut these membranes. The seventh and eighth cranial nerves are superficial and just inferior to the fifth cranial nerve. You can see the seventh and eighth cranial nerve right here. It's important to be very careful doing exchange of instruments within the operating field not to injure nerve. I just open enough arachnoid to release the traction on the nerve. However, most often the immediate arachnoid over there can be left intact to protect the nerve. I used the tip of the microscissors as a dissector to open the arachnoid membranes and then identify the absence of any entangling, small perforating arteries, and then continue to just cut the arachnoid and open the membranes. You can see the fifth cranial nerve there. The relationship of seventh and the eighth and the fifth cranial nerve are more evident now. You can see seventh and eight there. And this unedited video illustrates some of the challenges of just getting the lighting right in order to be able to see through the posterior fossa. At this time I'm just adjusting the distance of the operative lens or the microscope's lens to the operative field so the instruments can be exchanged without necessarily hitting the lens of the microscope. Having the appropriate distance is quite necessary for getting enough light into this small craniectomy site. Now that we seem to have reasonably good distance from the operative field, we'll go ahead and adjust the magnification. Here you can see Dandy's vein or the superior petrosal vein. I'll go ahead and open the arachnoid membranes, just parallel to the lateral margin of the vein, in order to expose the trigeminal nerve. I frequently do not sacrifice the superior petrosal vein as it is unnecessary to do so. The vein is owning relatively a redundant path and can be mobilized with dissection of the arachnoid membranes. Here you can see the trigeminal nerve. The arachnoid membrane over the shoulder of the nerve is being dissected. One has to remember that the V2 offending vessel is, often it is at the shoulder right here where the vein is at this time. However, for the V1 pain, most often the vascular loop is located at the axilla of the nerve superiorly. And this is what I'm expecting at this time, to find a vascular loop at the axilla of the nerve. The loop is most likely at the root entry zone so I'll go ahead and continue mobilize the vein to be able to identify the root entry zone close to the brain stem. However, the entire cisternal segment has to also be decompressed. I'll go ahead and mobilize the vein. You can see a curved dissector which is quite helpful. The curvature of the tip is more than the usual one used for a super tentorial surgery. This additional curve allows me to see around the tip of the dissector in the small working space of the posterior fossa. Here's the dissector mobilizing the vein away from the shoulder of the nerve and the initial offending vessel is apparent. Although a vessel has been found, I continue to further inspect the area for any other potential offending vessels that could be missed just because the first one has been the center of attention. Pulmonary irrigation is used, clear the field. The motor root of the trigeminal nerve is carefully protected. Additional space along the medial aspect of the vascular loop is necessary to ensure that no other loop is apparent or necessarily this is not part of another loop. And you can see it is. There is one limb of the loop and the other one more posteriorly. This signifies the fact that the loop is most likely just at the axilla and anterior to the nerve. And now we have to continue to dissect the loop along the interior aspect of the nerve to be able to completely mobilize the loop away from the shoulder of the nerve. Any small bleeding from the vessels can be easily controlled with irrigation. Aggressive coagulation should be avoided. So now we take on the challenge of mobilizing this loop. It can be quite challenging because this loop extends all the way to the inferior edge of the nerve which is located here. So I'll go ahead and work more superiorly and patiently dissect the arachnoid bands as much as possible. And then divert my attention a little bit to the inferior aspect of the nerve, where the value of the loop will be further dissected so the entire loop can be mobilized out of the shoulder or axilla of the nerve. Additional space is necessary. I'll go ahead and use the microscissors to open arachnoid membranes along the distal cisternal segment of the nerve. By manual dissection and use of the handheld suction device as a dynamic retractor is quite effective to avoid fixed retraction and fixed retractor blades that can be even compromising the operative field. Here is the more proximal segment of that loop, the superior cerebellar artery and its branches. Now that we have the anatomy more thoroughly laid out, we'll go ahead and continue mobilizing the loop. Here's the vascular loop at the axilla. There is a small vein that most likely can be sacrificed safely in order to untether the trigeminal nerve from the overlying structures. This untethering would allow me to move the nerve slightly more inferiorally and therefore be able to move the artery of the axilla. It seems like this is the best I can do right now unless either the small vein is sacrificed or if I move more inferiorly along the edges of the nerve to mobilize the value of the vascular loop. The interlateral aspect of the pons is apparent. No other offending vessel is evident. You can see this seventh and eighth complex that is carefully protected during the inspection of the lower portion of the nerve. You can see the vascular loop reaches all the way in the axilla of the nerve and more anteriorly. I'll go ahead and try to mobilize the loop as much as possible. The nerve is somewhat deformed posteriorly, and it's not in its physiological position. Some manipulation of the nerve is necessary to get this loop just released enough so it can be mobilized along the superior edge of the nerve. Gentle manipulation however prevents any trigeminal neuropathy and post-operative numbness. Here is the loop relatively free inferiorly. Now we go ahead and redivert our attention more superiorly where we can find the vascular loop and mobilize the entire complex from the interior aspect of the nerve. That small vein is still apparent and probably tethering the nerve at this time. We'll go ahead and coagulate and cut that small nerve momentarily to be able to, again, untether the nerve completely and be able to manipulate the vascular loop more aggressively. Bipolar forceps with fine tines are especially useful to be able to see around the forceps. And therefore I will go ahead and exchange my forceps for a finer set off tips to be able to adequately see the tips while I'm coagulating the vein without placing the vascular loop at risk. Any epidural bleeding is usually cleaned out periodically to keep the intradural space pristine. Here's the vein that's being coagulated and subsequently transected. The Dandy's vein remains intact. It's quite resilient as long as it's manipulated carefully and not placed under significant traction to a avulse it's entry into the tentorium or junction area. Now that all the structures and the arachnoid bands are dissected and the vascular loop is mostly untethered, we'll go ahead and see if I can move the vascular loop out of the axilla of the nerve. You can see that fair amount of manipulation is necessary. The loop is almost out of the axilla. However, continuous gentle teasing of the bands around the vascular loop to mobilize the artery is necessary. You can see that tiny bands that are still apparent on the anterior aspect of the nerve. The nerve is in a more physiological position at this stage. High magnification is used. Here's the loop almost released completely from the axilla of the nerve. Here is the final piece. You can see it's quite tortuous. Although there are still some fine bands that are effecting the two branches of the superior cerebellar artery. The main branch is evident there and the two branches are the offending vessels. So the anatomy is now completely exposed. I'll go ahead and move the loop. And this is the last section of the loop that should be being mobilized. It's important to know that in this situation, because of the very redundant pathway of the vascular loop, its mobilization often leads to its kinking. Other contingency plans are necessary to ensure that the lumen of the vessel is intact at the end of the procedure where the implant or the Teflon prostheses is placed. So for now, let's go ahead and move the vascular loop out of the axilla of the nerve. Ensure that the nerve is assuming a more physiologic posture, which it seems it is, and now we'll have to reposition the vascular loop so it is not so kinked. If there's evidence of spasm in the vessel due to manipulations noted, a piece of papaverine-soaked Gelfoam is used to bathe the artery and relieve the spasm. This maneuver is quite effective. You can see some discoloration along the root entry zone of the nerve. This finding assures me that the compressive vessel has been found and adequately addressed. Now that we feel that the offending vessel has been moved, I'll inspect other areas, especially more superiorly and superficially to ensure that no other offending vessel is overlooked. Now the vascular loop is being untangled so that kinking in its lumen is relieved. And therefore, instead of allowing it to go back to its original position, I'm gonna move the loop anteriorly more parallel to the nerve and let the vascular loop lay on the prosthetic that will be implanted momentarily. Further inspection inferiorly, again, does not reveal any other evidence of compression. I'm very satisfied. The nerve looks relatively healthy. They're really safe. And we should be just about ready to proceed with placement of the Teflon. However, I'm inspecting again around the vein and underneath it to make sure that another more superficial loop is not overlooked. The entire cisternal segment of the nerve is decompressed. You can see all the way across the pons to the clivus. It's quite evident that no other vessel could be placing the nerve in danger. Here is that extra inspection more medially and superficially to ensure that no other compressive vessel is apparent. That's the area of discoloration again. That extra curvature of the dissector is quite helpful and beneficial to see around the edges. Now we're just about ready to proceed and place the Teflon implants. I'm going to shred the pieces of Teflon to be able to achieve a good modeling and place the Teflon implant. Here you can see that a very small piece is implanted first between the nerve and the artery, and then rolled distally along the route of the nerve to be able to decompress the nerve. Now that the first piece has been implanted, we'll go ahead and bring a larger piece of shredded Teflon. This larger piece will be able to mobilize a good portion of the loop. Excessively large pieces should be avoided as they will prevent adequate visualization around that implant to ensure the vascular loop is completely mobilized away from the nerve. In addition, larger pieces of Teflon can cause compression of the nerve by themselves and lead to trigeminal neuropathy or potentially recurrence trigeminal neuralgia from the phenomenon of Teflon granuloma. Here, I am able to look around the Teflon. I first placed the shredded Teflon and then used the dissector to mold the implant to the area that I would like it to be situated in. Since the former construct is essentially complete, I will go ahead and use a micro Doppler ultrasound device to ensure that the flow within the vessel is uninterrupted. I detect good Doppler pulse, and I'm happy that the vessel is not necessarily compromised. Our final step would be placement of the small piece of implant to decompress the very distal cisternal segment of the nerve. As we discussed, the entire nerve including its root entry zone, proximal cisternal segment and the distal cisternal segment, should be thoroughly decompressed to ensure prevention of any recurrence of trigeminal neuralgia or delayed displacement of the implant. I'm satisfied. We'll go ahead and demagnify our operative field, irrigate thoroughly to make sure the implant is not gonna move out of its place. The anatomy is apparent. You can see the seventh and eighth cranial nerves, you can see the tentorium. This opening is more than enough to complete a thorough decompression for the trigeminal nerve. A little bit of epidural bleeding can be evacuated. The cotton will be removed along with a rubber dam underneath it. Bone wax was initially used on the way in when the dura was opened and additional bone max will be used on the way out when the dura is closed. You can see the cerebellar hemisphere and its cortex is very healthy. I'm going to remove the retention sutures on the dura and start dural closure. However, further irrigation will be done before the final suture is laid down as it is imperative for all the air to be forced out from intradural space and immaculate the hemostasis. Confirmed. Pristine nature of intradural procedure decreases the risk of postoperative aseptic meningitis and can also decrease postoperative headaches and nausea and discomfort. Techniques of dural closure are relatively straightforward. If the procedure is pristine as expected, I do not persist upon watertight dural closure for microvascular decompression procedures. However, the mastoid aerosols have to be thoroughly filled with bone wax to prevent or minimize any risk of postoperative CSF fistula development. I'm going to reflect the edge of the dura so I can approximate the edges as effectively as possible. This edge is relatively inverted so I'm going to use the tip of the needle in order to invert the edge and start my dural closure, which will be performed essentially in the middle of the dural opening first and then extended to both sides. The last stitch will be placed, but not knotted yet until, again, the intradural space is thoroughly irrigated and immaculate hemostasis confirmed. Any bleeding from the sinus should be controlled with covering the roof of the sinus with a thrombin-soaked Gelfoam. Aggressive impaction of the lumen of the sinus with Gelfoam should be avoided as this can lead to thrombosis of the sinus. The Dura is relatively slack. Again, as long as the procedure is performed efficiently, most of the dura are protected from the intense light in the microscope. The dural closure should be relatively straightforward and seamless. Here's the additional sutures that are approximating the dura. Watertight closure should be relatively easy in this case. I'm going to also perform a methyl methacrylate cranioplasty at the end of the dural closure. Pulmonary irrigation is used. You can see the last one or two stitches are left loose while the intradural space is being thoroughly irrigated until clear fluid is returning. The last stitch is now isolated and the last knot is laid down to complete our dural closure. Again, a methyl methacrylate cranioplasty is completed and the rest of the muscle and scalp layers are closed in the anatomical layers. Thank you.
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