July 01, 2015
This is another surgical video describing technical analysis for a section of a CP angle or a petrotentorial meningioma. Interestingly, this small tumor caused trigeminal neuralgia in this young patient, the tumor is located around the area of the Meckel's cave, most likely invading part of the Meckel's cave, pressing against the trigeminal nerve, leading to trigeminal neuralgia. Obviously part of the tentorium is also affected by this tumor. This patient underwent a right sided retromastoid craniotomy using the standard curvilinear incision. You can see the landmark for the mastoid groove in the transfer sinus Brainstem auditory evoked responses were monitored in this case. Here is the transfer sigmoid sinus and their junction. The dural is incised peril the dural venous sinuses. The edges of the dural all tacked up, piece of rubber dam is used under the cottonoid to slide the cottonoid around the cerebellum effortlessly Here is the tentorium. Tentorium petrous junction, where the tumor is located. The arachnoid bands are generously dissected. Here is the seven and eight cranial nerve complex. The arachnoid bands over these nerves are also released to avoid any traction on the sensitive nerves. Let's go ahead and carefully expose the tumor. Since the tumors is relatively small, I like to identify the vital neurovascular structures early on and keep them out of harm's way, during the later steps of the operation. This superior petrosal vein is also coagulated and sacrificed. The arachnoid bands over the lower cranial nerves were also partially dissected So any traction on the cranial nerves, during cerebellar hemisphere manipulation and mobilization is avoided. Here's the fourth cranial nerve at the edge of the tentorium Here is the superior cerebellar artery branches. I'll go ahead and find the trigeminal nerve and the brain stem. One more time, emphasizing the principle of early neurovascular identification for their protection. Here's the tumor against the trigeminal nerve. Some of the motor roots of the nerve are very much adhering to the tumor capsule in this area. Surface of the brain stem I can dissect the tumor relatively easy, further preparing the surface of the tumor for its coagulation and devascularization. However, the first step for devascularization would involve disconnection of the tumor from its base at the level of the petrous bone and the tentorium. Here is now the tumor very well isolated. I have a good control over the vital neurovascular structures early on. Now the tumor is generously devascularized at its base over the dural of the petrous bone and tentorium Here is disconnection of the base of the tumor from the tentorium that is infiltrated by the mass. Early devascularization minimizes the spot loss and also keeps the operative field clean during the later stages of microsurgery. The fourth cranial nerve, I'm going to leave part of the tentorium that is affected by the tumor, behind for the next step of the operation. Here, you can see the fourth nerve is being carefully followed along its length. The larger portion of the tumor is being removed piecemeal, The fifth cranial nerve, now the tumor here is more aggressively mobilized away from the fifth cranial nerve. Part of the tumor that could be infiltrating the Meckel's cave, is also being dislodged The route of the compressed trigeminal nerve, is now more apparent. There is large piece of tumor that was removed. Here's part of the tentorium that is affected by the tumor. I'll go ahead and remove a window of the tentorium infiltrated by the tumor in this case. An initial incision was created along the more posterior aspect of the tentorium. This incision is advanced anteriorly while carefully watching for the fourth cranial nerve. Here is the last cut. Here is the the more lateral part of the tentorium towards the petrous ridge. Again, we're cutting a window of the tentorium toward the petrous ridge, a part of their tentorium that is infiltrated by the tumor. Here's the basal surface of the occipital lobe. Here's the petrous ridge, I continued to follow the petrous ridge One has to be specially careful about trochlear nerve Here as you can see as it enters the tentorium So it's not transected Small portion of the tumor may have to be left behind to protect the trochlear nerve. As you can see here is the final result of the resection cavity with part of the tentorium, that was affected by the tumor removed and part of the tumor that was affecting the Meckel's cave was also resected. Small portion of the dural of the petrous bone that could have been affected by the tumor was heavily coagulated to minimize the risk of future tumor recurrence, The magnified view of the operative space closure waxing of the air cells, a watertight dural closure. I use a piece of gel foam sheet to cover the epidural space. Fibracol may be used in select cases. Cranioplasty was performed in this case since then initial craniectomy was completed for exposure and post operative MRI in this patient demonstrates complete removal of the mass and the patients trigeminal neuralgia resolved after surgery. Thank you.
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