Giant Acoustic Neuroma
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Resection of giant acoustic neuromas can be quite challenging. The retromastoid approach is the ideal approach for such giant tumors. This is a 22 year old pregnant woman, 26 weeks pregnant with gait instability, and significant facial weakness. MRI evaluation revealed a five centimeter acoustic neuroma with significant evidence of brainstem compression and hydrocephalus. Since she was pregnant, she first underwent placement of a ventriculoperitoneal shunt to relieve her hydrocephalus and allow a smooth delivery. Two weeks after her delivery of a healthy baby she underwent a retromastoid craniotomy for resection of her tumor. You can see the horseshoe incision at the location of the mastoid groove and the approximate location of the transverse sinus. Here's the sigmoid sinus that was unroofed. Obviously, the cerebellum is quite tense despite the presence of the shunt. Cisterna magna was opened for further CSF drainage. And the tumor was aggressively debulked after the lateral edge of the cerebellum was resected. I resect a very small part of the lateral cerebellum in giant tumors to facilitate resection of the mass and minimize significant retraction of the cerebellum. Here's the trigeminal nerve along the superior pole of tumor just underneath the tentorium. Mapping was used during the entire resection process. However, since significant facial weakness was present preoperatively, I suspected that I will not be able to map the facial nerve. The nerve will be extremely attenuated and may not be salvageable in such size tumors with significant preoperative facial weakness. Here are the lower cranial nerves mobilized away from the inferior pole of the tumor. After mapping the circumference of the tumor, the capsule was carefully mobilized from the brainstem. All the PL membranes were protected over the brainstem as much as possible. Further debulking continues and the tumor that is essentially located facing the brainstem is mobilized laterally. I continue to map the superior pole of the tumor. The trigeminal nerve is mobilized away. Here's the fourth cranial nerve at the level of the incisura. Tumor capsule is coagulated before it's removed piecemeal. Here's the root entry zone of the trigeminal nerve near the brainstem. Now that most of the tumor located in the cisterna is debulked. We divert attention to the intracanalicular portion of the tumor. This part of the tumor was also removed. Here's the facial nerve localized within the canal. However, this nerve was not discernible at the level of the porous. Tumor debulking and mobilization continues for the portion of the tumor located within the CP angle. Because of the giant size of the tumor, it's not unusual for pial membranes to be violated. However, every attempt should be made to minimize any parenchymal injury. You can see most of the pial surfaces are intact. More debulking allows aggressive mobilization of the tumor capsule away from the brainstem. Here's the sixth cranial nerve adhering to the capsule of the tumor. This nerve was ultimately dissected from the capsule. Gross-total removal of the mass was possible. Facial nerve was not salvageable. Here's the trigeminal nerve joining the brainstem. Hemostasis was secured. Postoperative MRI revealed gross-total removal of the mass without any evidence of ischemia. This patient made an excellent recovery without any lower cranial nerve dysfunction. However, required further reanimation procedures for her facial weakness. Thank you.
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