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Vestibular schwannoma manifesting with hemifacial spasm in a young woman: clinical considerations and tumor removal with hearing preservation. Two-dimensional operative video
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Vestibular schwannoma manifesting with hemifacial spasm in a young woman: clinical considerations and tumor removal with hearing preservation. Two-dimensional operative video
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T00H10M35S
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Upload Date:
2021-10-27T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[MUSIC PLAYING]
CARLOS CANDANEDO: This is Dr. Carlos Candanedo from the Hadassah-Hebrew University Medical Center in Jerusalem. This video depicts imaging findings and the dissection of a vestibular schwannoma manifesting with hemifacial spasm in a young woman, with discussion of clinical considerations and tumor removal with hearing preservation. A 27-year-old woman, otherwise healthy, presented with a 2-month history of left-side hemifacial spasm.
CARLOS CANDANEDO: On physical examination, besides the intermittent sustained contractions of the perioral facial muscles, there was no other cranial nerve or focal motor deficit. Preoperative pure tone audiometry showed normal hearing bilaterally with a speech reception threshold of 10-15 dB. Preoperative ABR show a delay in wave III on the left side, compared to the right side, indicating a fraction of the cochlear nerve by the tumor.
CARLOS CANDANEDO: But hearing was still intact. Brain MRI revealed a left vestibular schwannoma with an extrameatal tumor diameter of 18 mm compressing the brainstem. Bone window head CT revealed pneumatization of the posterolateral wall of the internal auditory canal, predicting high risk of postop CSF leak. We decided that the most appropriate treatment would be surgical removal, because of the hemifacial spasm.
CARLOS CANDANEDO: But, given that the patient's hearing was normal, it was also important to evaluate the chances of hearing preservation. Important prognostic signs in this case are the intracanalicular tumor that did not reach the end of the IAC, as clearly seen on FIESTA images. The anatomical position of the labyrynth was convenient, providing the possibility of sufficient IAC drilling to expose the entire tumor, without violating the posterior semicircular canal or vestibule.
CARLOS CANDANEDO: Which is also possible to see on MRI FIESTA and CT bone window images. The surgery was performed with the patient in a right three-quarters prone position, using auditory brainstem response and four-channel facial nerve nerve physiology monitoring. We preferred this three-quarters prone position instead of the park- bench position. This head is kept parallel to the floor, while the upper shoulder falls forward with the gravity, and facilitates unlimited room for the surgeon's hand.
CARLOS CANDANEDO: We also looked for the lateral spread responses, but we found no evidence of this response in our patient. The left hip was also prepped for fat graft harvesting, since we were aware of the possibility of postop paradoxical CSF leak. We made a retroauricular curvilinear skin incision and performed a retrosigmoid craniectomy, with exposure of the transverse sigmoid junction. Adequate sealing of the open mastoid air cells was done with a mixture of bone wax and bone dust.
CARLOS CANDANEDO: Now, this would prefer to build the mold of polymethyl methacrylate bone flap for cranioplasty in situ before opening the dura, to avoid the overheating of the cerebellum, by flushing off the mold. By doing this, would prevent the toxic monomer that is liberated from being submerged into these intradural spaces, since it is potentially neurotoxic to the cerebellum.
CARLOS CANDANEDO: Since the posterior fossa dura and cerebellum are tense in this position, we made a small triangular dural incision in the inferior part of the craniectomy, and inverted dural flap basally. The otherwise intact dura keeps the cerebellum in place and prevents it from prolapsing. Through this tiny opening we carefully insert a narrow retractor beneath the cerebellum, elevating it 2 to 5 mm, enough to open the arachnoid at the edge of the cisterna magna, achieving CSF outflow with cerebellar relaxation.
CARLOS CANDANEDO: Then, we open the dura, and you can see the cerebellum is relaxed. To prevent severe trauma, it should not be retracted, but elevated. We start from the lower point of the canal opening, where we have opened the cistern and released CSF. Small rigid veins are identified, coagulated and truncated. We identified the spinal accessory nerve and continue arachnoid dissection around it, and then, laterally, in the direction of the vagus and glossopharyngeal nerve.
CARLOS CANDANEDO: Finally, a tumor with a typical appearance of vestibular schwannoma comes into view. Using the Prass probe facial monitor, we check the posterior surface of the tumor to be sure there is no posterior facial nerve location. The dura above the IAC is coagulated and excised. We prefer to open the IAC in the early steps of surgery for the following reasons: we obtain more room for surgical manipulation, it improves our anatomical understanding, and drilling before arachnoid dissection around the tumor prevents bone dust for being dispersed around the CPA and parabrainstem cisterns, since this dust may be a reason for persistent postoperative headache.
CARLOS CANDANEDO: The depth of drilling is measured on the preoperative head CT. We used coarse and regular diamond drills, with copious irrigation to prevent thermal damage to the nerves. Mastoid air cells were opened while drilling and obliterated with pieces of bone wax. The dural sleeve inside the IAC is opened, and the thin bony shells in the sides of the IAC may be removed with ultrasonic aspiration.
CARLOS CANDANEDO: Now we debulk, the intracranial and intracanalicular part of the tumor with a 1.14-mm precision tip ultrasonic aspiration. After significant tumor debulking, we may proceed to identify the cranial nerve and to dissect the tumor, which we flip away from the brainstem and start to see the preserved layer of the nerve.
CARLOS CANDANEDO: Know that the cochlear nerve, vestibular nerve, and the facial nerve are lying in the same bundle and the same direction. [BEEPING SOUND] The tumor did not split the nerve apart. This is a very important condition for the hearing preservation. From this point, we performed by manual peeling. Not suction in forceps, but with two micro forceps, one in each hand of the surgeon.
CARLOS CANDANEDO: This provide tumor retraction with one hand, and delicate peeling of the arachnoid or nervous layer with the other hand. Of course, this demands high magnification. Only now we start to see the AICA loop, which cause compression of the facial nerve, which was found in its most typical anatomical location, in the inferoventral corner between the tumor and the brain stem.
CARLOS CANDANEDO: We separate the AICA loop from the facial nerve. There was obvious compression, which is playing the hemifacial spasm, patient's main complain. The tumor had compressed the facial nerve against the AICA. The entire nervous layer containing facial and cochlear nerve was very well preserved and covered with microcottonoid. We proceed with the removal of tumor remaining in the IAC. It is important to mention that dissection should be done in the peripheral direction, from the brainstem to the ending of the IAC, and not the opposite, since traction away from the fundus may cause trauma and rupture of the fine nervous fibers, where they penetrate into the cochlea and cause a hearing loss.
CARLOS CANDANEDO: The ABR followed by the neurophysiologist showed in the upper arrow a deterioration of the ABR wave V and then, a partial recovery marked with the lower arrow. Wide IAC opening enabled by manual dissection even inside the canal will remove the last visible tumor piece with an angle curette and insert a QEVO endoscopic microinspection tool of a 45-degree angle. This revealed obvious residual tumor in the fundus of the IAC.
CARLOS CANDANEDO: We drill additional 3 mm of the lateral IAC and remove this tumor remnant. Repeat examination through QEVO now confirmed complete tumor removal. The facial and cochlear nerve are well preserved. The facial nerve respond to stimulation with 0.02 mA [BEEPING SOUND] from the exit area.
CARLOS CANDANEDO: Since the patient had hemifacial spasm, and there was an obvious compression by the AICA, we placed a tiny Teflon polymer pledget between the artery and the nerve. A piece of fat harvested from the patient's hip was inserted to pack the drill area of the IAC without compressing the nerves. And a mixture of cryoprecipitate and thrombin was added to help seal in the opened air cells.
CARLOS CANDANEDO: Watertight dural closure was completed with Lyoplant, which is a dural matter substitution from lyophilized bovine collagen and Prolene 5-0. This is a fusion image of the preop MRI and postop CT. Showed in red, the drill area next to the IAC. In yellow, the part of the tumor removed microscopically. And light blue, the part removed with the endoscope. The pathology report was consistent with schwannoma, as suspected.
CARLOS CANDANEDO: Following surgery, the patient's hemifacial spasm resolved, and she had no evidence of facial palsy or subjective hearing loss. Postoperative pure tone audiometry revealed a new onset unilateral high tone perceptive hearing loss at 6-8 kH of 100-105 dB on the left side. But speech perception thresholds were unaffected. Postoperative brain MRI showed the fat in the surgical area sealing the opened mastoid air cells around the IAC, and complete removal of the tumor, Including the intracanalicular segment.
CARLOS CANDANEDO:
