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Suprameatal Endoscopic Approach: Trigeminal Schwannoma

November 30, 2020


The suprameatal approach, is an excellent approach to extend the reach of the retromastoid route, toward the Meckel's cave and maximize resection of the tumors, that extend from the CP angle, into the Meckel's cave. We're going to review the technical nuances, and some of the anatomical details, in this video. This is a 45 year-old male, who presented with right-sided trigeminal neuralgia. MRI evaluation revealed a mass in the area of the CP angle. As you can see at the tip of the arrow, extending into the Meckel's cave. You can see that on the coronal image as well, extending into the posterior aspect of the Meckel's cave. And there is a relatively small component of this tumor, also present within the CP angle. Removal of the tumor, all the way through the Meckel's cave, can be challenging, and require radical skull base approaches. However, I'm going to review some of the modifications of the CP angle, and osteotomy around the suprameatal tubercle, with the use of the endoscope, to be able to maximize resection of the tumor, through a relatively minimally invasive route. Here is a right-sided retromastoid craniotomy. Here's the sigmoid sinus, or it's edge. Here's the transverse sinus. Here's the transverse sigmoid sinus junction, right at this region. The dura has been opened, along the dural venous sinuses. Again, we're on the right side. You can see the fifth nerve, that's being gently mobilized, and here's the tumor, very intimately involved, with one of the superior branches, of the, fifth nerve. As you can see here, the capsule of the tumor is being dissected, from the brain stem. This tumor, ultimately, was found to be a trigeminal schwannoma. Here's the tumor being debulked. Again, you can see. One of the, tiny branches of the nerve, is very intimately associated with this tumor. Going to gently mobilize the nerve away, and remove as much of it, as possible, while preserving, as many of the fascicles of the nerve possible. Here is a portion of the tumor within the CP angle being removed. Now it's going to be, the time for removal of the tumor that is extending, into the Meckel's cave. Here, additional tumor removal towards the Meckel's cave. As we get closer to the Meckel's cave, the tumor becomes less visible, and we're going to have to remove some of the bone, in the area of the suprameatal tubercle, to be able to achieve further visualization. Here is the, bone ultrasonic aspirator, that we're going to use to drill the bone. This device avoids slippage, of a regular drill, and we used a curette, as well, to peer out some of the tumor, and the bone. Here is further bony removal. A CT angiogram stealth may be used, to protect the carotid artery, or other structures, within the petrous apex. Some bleeding may be encountered. Venous bleeding that can be easily controlled. We continue bony removal, toward the carotid artery. As you can see, here is an extra length of the trigeminal nerve, that's being exposed, and we're removing more tumor, within the Meckel's cave, using the curette. Here is, again, additional tumor removal, within the posterior aspect of the Meckel's cave, The capsule of the tumor and a small fascicle, that was very much involved with a tumor, is being used, as a method to deliver, the residual tumor into the resection cavity. Here, you can see additional tumor removal through the Meckel's cave. Again, you can see that fascicle of the nerve, that was intimately associated, with the tumor. I'm using this as a handle, to deliver the tumor into the resection cavity, and evacuate it, using the suction device, if possible. Now, it's about all we can do, without the use of a 45-degree visualization device, in order to remove the tumor. I'm going to bring in the keyhole device, to be able to further extend the visualization. More, anteriorly. Here are the last pieces of the tumor. Through this window, here, using the 45-degree endoscope, you can see small amount of residual tumor, that has to be evacuated, in this area. Again the nerve, the tumor. We'll go ahead and, uh, use the curette device to remove additional tumor. First, we're going to remove additional pieces of bone, to extend our reach. You can see, at least half a centimeter of additional length, of the trigeminal nerve has been exposed. I'm going to use the curette device, to remove additional pieces of tumor, all the way through the Meckel's cave. And here is the final view, showing, almost radical, gross total resection of the tumor with very, real little, around, of the affected fascicle of the trigeminal nerve. Here is the final result. And a post-operative MRI, demonstrated gross total resection of the tumor. You can see that the tumor, all the way through the Meckel's cave, at the tip of the arrow, was removed. And this patient had some post-operative numbness, in the trigeminal nerve, that significantly improved, at the six weeks follow-up. So, again, this is a nice, minimally invasive extension of the retromastoid craniotomy, into the Meckel's cave, in order to maximize resection of the tumors, that extend from the CP angle, into the area of the Meckel's cave, and posterior cavernous sinus. Thank you.

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