DESCRIPTION OF OPERATION: After informed consent was obtained, the patient was taken to the operating room and general anesthesia was administered. Attempts were made at placement of a lumbar drain, which were unsuccessful. The patient was placed in a supine position with the head turned to the right side to expose the left side of the head. The head was then placed in a Mayfield pin-head holder. EMG monitoring of the cranial nerves was performed throughout the case. The suboccipital area was then prepped and draped sterilely. A linear incision measuring approximately 10 cm was made in the retromastoid area. Using monopolar cautery, the suboccipital area was exposed as well as the mastoid process. Bur holes were placed and a craniotomy was completed using a craniotome. Additional craniectomy was performed to expose the transverse and sigmoid sinuses. Excellent hemostasis was achieved with Gelfoam and bone wax. The mastoid air cells were entered and extensively waxed. At this point, the dura was opened in a curvilinear fashion based laterally. Mannitol was given as well as Decadron. The operative microscope was brought into use and the remainder of the procedure was performed using careful microdissection techniques, including the use of microbipolar cautery, microscissors and microdissectors. This was done to prevent injury to the delicate neural and vascular structures. With careful retraction, the cerebellum was able to be retracted medially along the cerebellopontine angle. Using microdissection technique, a mass was encountered. A sample was sent for frozen section pathology, which was consistent with schwannoma. With careful microdissection techniques, the inferior and superior portions of the tumor were exposed. Draining veins into the petrosal vein were carefully coagulated and divided on the superior portion of the tumor to facilitate retraction of the cerebellar hemisphere. On the inferior pole, the lower cranial nerves were identified. The posterior wall of the tumor was stimulated and there was no facial nerve response. The posterior portion of the tumor was then coagulated and the tumor was internally debulked using a Cavitron ultrasonic aspirator. By internally debulking, additional tumor was able to be resected circumferentially, and using this type of meticulous dissection, the upper and lower poles of the mass as well as the medial portion of the tumor were able to be rolled centrally. Excellent extra-arachnoidal dissection plane was established. Small feeding vessels were carefully coagulated and divided, and additional internal debulking was performed. The facial nerve was then identified coursing from the brainstem. This was stimulated with good facial response. There was also a second branch, which extended in the superior portion of the tumor, which also was able to be stimulated with facial nerve function. Additional resection was performed taking great care to preserve the cranial nerves. It was felt that an excellent decompression was performed. The brainstem was well protected. The facial nerve was able to be followed from the brainstem to the porus acusticus. It was felt that the small residual could be treated with radial surgery. The area was irrigated with excellent hemostasis and again a very small residual was noted extending into the internal auditory canal. The IAC was not drilled. The dura was then closed with 4-0 silk suture. Gelfoam was placed over this defect. The craniotomy bone flap was replaced and secured using titanium plates and screws of the Leibinger Stryker system. Again, excellent hemostasis was achieved. The musculature was approximated with a Vicryl suture. Subcuticular Vicryl sutures were placed and the skin was closed with catgut running suture.
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