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Trigeminal Schwannoma: Root Type

January 13, 2016

Transcript

This video reviews resection of a root type Trigeminal Schwannoma within the cerebellar pontine angle. This is a 47 year-old male who presented with right-sided progressive V1 numbness and on MRI evaluation was noted to have an enlarging relatively homogeneously enhancing tumor, partially extending into the Meckel's cave. These findings are consistent with presence of a Trigeminal Schwannoma. Due to the progressive enlargement of the tumor, he underwent a right-sided retromastoid craniotomy for resection of his tumor. A lumbar puncture was performed at the beginning of the procedure to achieve early brain decompression. You can see the curve on the incision. That was fashioned around the dural venous sinuses to expose the CP angle. Brainstem auditory evoked responses were monitored. The dura was opened along the dural venous sinuses. I use a piece of rubber dam or cloth to slide around the cerebellum and expose the petrous tentorial junction. Here's the tumor affecting some of the fascicles of the trigeminal nerve. The superior petrosal sinus was sacrificed early to allow working space. The arachnoid bands were generously exposed so that the tumor can be debulked, and the fourth cranial nerve identified early. Here's the seventh and eighth cranial nerve, which are untethered. You can see the fascicle of the fifth cranial nerve affected by the tumor. Most of the nerve is unaffected and draped around the inferior pole of the tumor. The affected fascicle is transected. The tumor is slightly mobilized away from the trigeminal nerve as much as possible. You can see there is significant amount of attachment there. Superiorly, you can see the brainstem. Early identification of important neurovascular structures keeps them out of harms way. Let's go ahead and debulk the tumor using pituitary rongeurs. Tumor's relatively soft but not suckable. Portion of it is. Here you can see the anterolateral aspect of the brainstem. Two suctions is used as much as possible to remove the tumor atraumatically. You can see the fourth cranial nerve at each of the tentorium draped over the superior pole of the tumor. A branch of the superior petrosal sinus was preserved. Now that the tumor is debulked anteriorly, let's go ahead and develop the plan between the tumor capsule posteriorly and the brainstem. The fourth cranial nerve was released from the superior pole of the tumor. And as you can see, the tumor is being gently pulled out of the cerebellopontine fissure. I continue to mobilize the tumor anteriorly away from the brainstem, remembering that the root entry zone of the fifth cranial nerve is substantially affected. Again, piecemeal removal of the tumor continues. Here, additional piece of the tumor are extracted. Dynamic retraction is quite effective. The suction device provides countertraction on the cerebellum and the brainstem. Here's that part of the tumor that is affecting the root entry zone of the nerve and intimately associated with some of the fascicles of the fifth cranial nerve. Piecemeal debulking continues. Here, you can see the nerve very adherent to the inferior pole of the tumor. Patience is a virtue, especially at this junction of the tumor removal to avoid any avulsion injury to some of the intact fascicles of the trigeminal nerve. Ultrasonic aspirator is also effective for evacuation of the fibrous portion of the tumor. Now you can see the nerve. And part of the tumor that is embedded within the root entry zone and the fascicles entering the tumor capsule. The tumor is being shaved off, further debulked. Here's the copping phenomenon where the tumor really embeds itself within the proximal portion of the nerve. One has to continue dissection while protect the nerve as much as possible to achieve a gross total removal of the mass. You can see the nerve is quite attenuated and thinned out. Here is, again, dissection of the tumor from the proximal portion of the nerve. Using countertraction on the nerve to mobilize the nerve away from the tumor capsule. Ambidextrous dissection is necessary. The nerve continues to be intact. Here's a more distal part of the nerve that is being released away from the tumor. Angle instruments are especially useful to mobilize the tumor away from the nerve. Obviously, the trigeminal nerve is quite forgiving as long as most of the intact fascicles are preserved. Short dissection is not necessary to remove the last attachment. You can see the major of the nerve is intact. You can see the portion of the tumor invading the Meckel's cave was also pulled out of the cave. Gross total tumor resection was achieved. Post-operative MRI demonstrates gross total removal of the tumor. The portion of the tumor, again, protruding into the Meckel's cave was removed. This patient suffered from some worsening of his trigeminal numbness. After surgery, however, this numbness has subsided and he continues to perform well. Thank you.

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