Name:
Hearing preservation middle fossa approach for intracanalicular vestibular schwannoma in a NF2 patient
Description:
Hearing preservation middle fossa approach for intracanalicular vestibular schwannoma in a NF2 patient
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Duration:
T00H10M24S
Embed URL:
https://stream.cadmore.media/player/51778b18-a32a-4ec1-af01-44f3736a346b
Content URL:
https://cadmoreoriginalmedia.blob.core.windows.net/51778b18-a32a-4ec1-af01-44f3736a346b/21-121.mp4?sv=2019-02-02&sr=c&sig=R5RVQWgAtu91kqIVJ2INGPxqxcHkK9I%2FM2grjE3hiqE%3D&st=2024-04-28T15%3A19%3A30Z&se=2024-04-28T17%3A24%3A30Z&sp=r
Upload Date:
2021-10-27T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[MUSIC PLAYING]
SPEAKER: We present a surgical video case of hearing preservation, middle fossa approach for intracanalicular vestibular schwannoma in an NF2 patient. This is a 53-year-old female patient with a history of familial neurofibromatosis type 2. The patient presented to us 5 years ago with bilateral intracanalicular vestibular schwannomas and normal hearing without tinnitus or vertigo.
SPEAKER: The patient elected to proceed with conservative treatment with surveillance MRIs and audiograms. At the preoperative consult, the audiogram was unchanged with a 15-dB pure tone average and a 100% speech discrimination bilaterally. There was, however, worsening of the auditory evoked potential with prolonged wave V latency in the left ear. MRI demonstrated bilateral enhancing tumors extending to the fundus of the internal auditory canal.
SPEAKER: The left-sided tumor measured 1 by 0.6 cm, as compared to previous imaging of 0.8 by 0.4 cm, and the right-sided tumor measured 1.2 by 0.5 cm, as compared to 0.8 by 0.5 cm on MRI 5 years prior. FIESTA MRI sequence clearly showed the cranial nerve VII and VIII in the cerebellopontine angle. Surgical intervention was recommended based on the progression of the tumor size and worsening of the auditory evoked potentials.
SPEAKER: The side of the surgery was chosen based on the changes of the auditory evoked potentials on the left. The middle fossa hearing preservation approach was recommended based on the size of the tumor, hearing status, intracanalicular location of the tumor with extension to the fundus of the IAC, and the senior author's published experience. Radiosurgery is an option in intracanalicular schwannomas to control tumor growth, but functional hearing is preserved in only 44% to 63% of cases.
SPEAKER: These hearing preservation percentages are lower than the results of the senior author for this type of tumor, with a 73% hearing preservation rate. The position of the head is important. We recommend 30 degrees head elevation for brain relaxation. Rotation of the head should not be more than 30 degrees to the opposite side, to allow a favorable vantage point in line with the long axis of the IAC and the obliquely oriented superior semicircular canal.
SPEAKER: A temporal craniotomy is created, measuring about 5 by 6 cm. We center the craniotomy 2/3 anterior to the external ear canal and 1/3 posterior to it. The craniotomy is flattened with a middle fossa skull base. We think that the anterior and lower location of the craniotomy is important to allow access to the V3 branch of the trigeminal nerve and to allow anterior to posterior unobstructed access and visualization of the internal auditory canal.
SPEAKER: Elevation of the temporal lobe dura away from the middle fossa skull base starts with coagulation and section of the middle meningeal artery. Next, the dura is elevated from the V3 branch of the trigeminal nerve. The dissection progresses posteriorly, with peeling of the dura away from the gasserian ganglion. The greater superficial petrosal nerve and the arcuate eminence are identified.
SPEAKER: We believe that this wide dural elevation is necessary to allow ample exposure of the superior surface of the petrous bone without undue focal retraction of the temporal lobe brain parenchyma. The arcuate eminence has clearly identified. The superior semicircular canal is blue-lined. The posterior extension of the dural exposure is maximized. The posterior limit of the IAC is identified.
SPEAKER: Drilling starts at the petrous apex. We think that this is a safe spot to start the bone removal. The geniculate ganglion is exposed and identified with the nerve integrity monitor probe. The course of the facial nerve and the facial nerve canal and the location of the cochlea are projected and conceptualized. This allows safer further drilling of the petrous apex, which then progress posteriorly to find the anterior limits of the internal auditory canal.
SPEAKER: Removal of bone over the IAC allows progressive definition of the borders of the IAC. Bone is then removed from the petrous ridge over the porus acousticus, with visualization of the dura of the posterior fossa. The bone removal progresses towards the fundus of the IAC and the facial nerve canal. The nerve integrity probe is used for identification of the facial nerve and the facial canal.
SPEAKER: Prior to further drilling at the dangerous area of the fundus, the important anatomical structures should be clearly identified. This includes the arcuate eminence, the facial nerve canal, the geniculate ganglion, and the cochlea. The bone removal then continues at the fundus. Exposure of the dura all the way to the end of the IAC is essential for accessing the lateral limit of the tumor, permitting safe resection.
SPEAKER: Thorough exposure of this area, however, comes close to the cochlea, facial nerve canal, and the ampulla of the superior semicircular canal. Careful attention is necessary to avoid injury to these structures. Dura is widely open, starting posteriorly to avoid the facial nerve anterior trajectory in the IAC. The dural opening continues to include all the dura of the IAC porus, petrous ridge, and petrous apex.
SPEAKER: This wide dural opening allows visualization of the entirety of the tumor. Debulking of the tumor starts posteriorly to avoid facial nerve injury, and continues at the more superficial part of the tumor. Proximal vestibulocochlear nerve is identified posterior and under the tumor at the cerebellopontine angle. Tumor debulking continues and clear identification of the vestibulocochlear nerve is obtained.
SPEAKER: Facial nerve is encountered in the IAC anterior and under the tumor, as opposed to the more common superficial location of the nerve. The tumor is peeled away from the facial nerve. The origin of the tumor is clearly seen at the superior vestibular nerve. Tumor dissection away from the more proximal aspect of the facial nerve continues, until the nerve is completely separated from the capsule of the tumor.
SPEAKER: Note the good plane of dissection between the nerve and the tumor. The origin of the tumor at the superior vestibular nerve is cut and the cochlear nerve is identified posterior to the facial nerve and under the tumor. Notice the cochlear nerve more posterior in the depth of the exposure and the origin of the tumor in the superior vestibular nerve in a more superficial location.
SPEAKER: The tumor is removed and passed off the field. After resection of the tumor, the cochlear nerve and the facial nerve can be seen in the tumor bed cavity. Proximal facial nerve is stimulated with the facial nerve integrity probe at 0.02 mA.
SPEAKER: At 18 months follow- up, the patient has preserved hearing, no tinnitus, no vertigo or balance difficulties. Audiogram at 11 months postoperative is unchanged from the preoperative audiogram, with a 15-dB pure tone average and a 100% speech discrimination. Postoperative CT shows extensive resection of the petrous bone around the IAC and petrous apex.
SPEAKER: Postoperative postcontrast MRI at 12 months shows no evidence of residual or recurrent tumor. Postoperative FIESTA sequence MRI at 12 months shows intact facial nerve and cochlear nerve from CPA to the cochlea. We present the case in a video of middle fossa hearing preservation approach as a viable option for treatment of intracanalicular vestibular schwannoma in neurofibromatosis 2 patients.
SPEAKER: The approach, however, is technically demanding, and an expertise with a surgical technique is required to achieve successful outcomes. We share technical pearls learned over 20 years experience with middle fossa approach to vestibular schwannoma.