Name:
Middle cranial fossa approach for acoustic neuroma
Description:
Middle cranial fossa approach for acoustic neuroma
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Duration:
T00H08M30S
Embed URL:
https://stream.cadmore.media/player/a3a8b95a-a605-491f-9e02-a1d578b3544c
Content URL:
https://cadmoreoriginalmedia.blob.core.windows.net/a3a8b95a-a605-491f-9e02-a1d578b3544c/21-124.mp4?sv=2019-02-02&sr=c&sig=nVqjbYm%2BzT9awgSC0sopRU36aL69CQ2qP%2BGZjiAABsc%3D&st=2024-04-28T15%3A19%3A07Z&se=2024-04-28T17%3A24%3A07Z&sp=r
Upload Date:
2021-10-27T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[MUSIC PLAYING]
PAUL GIDLEY: This is Dr. Paul Gidley, and this is our middle cranial fossa approach for excision of acoustic neuroma. The middle fossa has a very complex anatomy, which is briefly reviewed here. Internal auditory canal lies at the same level as the external auditory canal. The key landmarks for the middle fossa are labeled here. An imaginary line drawn from the GSPN joins an imaginary line drawn from the arcuate eminence to form an angle that is roughly 90 to 120 degrees.
PAUL GIDLEY: The internal auditory canal is found by bisecting this angle. The patient presented is a 38-year-old man with an incidental acoustic neuroma, first identified in 2012. It was observed to grow. This is his initial MRI showing a small intracranial ocular tumor.
PAUL GIDLEY: Repeat imaging shows interval growth of the tumor. The audiogram shows good hearing in the right ear with a word understanding of 96%. ABR shows absent wave 3 and wave 5 on the right side. The options for management were explained to the patient. And these include observation with serial imaging, microsurgical resection, and stereotactic radiosurgery.
PAUL GIDLEY: The risk and benefits of each one of these approaches was outlined, and he opted for surgical excision. Hearing preservation is offered to patients under the age of 65 with small tumors and good hearing. ABR waveforms should be intact to allow intraoperative monitoring. The patient is positioned supine with the head in a Mayfield head holder.
PAUL GIDLEY: Electrodes for facial nerve monitoring are placed. ABR is performed intraoperatively. In this patient, the intraoperative waves 1, 3, and 5 were present. The skin is marked to outline a posteriorly based skin flap that follows the hairline. Temporalis fascia is harvested and set aside. An interior temporalis muscle flap is elevated. Craniotomy is planned to be centered at the external auditory canal measuring 4 cm high and 4 cm wide.
PAUL GIDLEY: It is important that the sides of the craniotomy are parallel. The patient is then given mannitol and is hyperventilated to allow dura elevation. Dura elevation is performed from a posture to anterior direction. Dura is elevated until the posterior fossa, arcuate eminence, and middle meningeal arteries are identified. A house urban retractor is in place at the petrous apex.
PAUL GIDLEY: The middle fossa anatomy can then be examined. The arcuate eminence and the GSPN are marked here. Imaginary lines outlining these two structures are marked here with bisection here, which should overlay the IAC. Drilling starts over the arcuate eminence in order to blue line the superior semicircular canal.
PAUL GIDLEY: The superior semicirclar canal is always perpendicular to the posterior petrous ridge. Any air cells that are open during this dissection are sealed off with bone wax. The blue line of the canal is seen here. Drilling then continues interior and medial to the superior semicircular canal to open up the air cells of the petrous apex.
PAUL GIDLEY: This drilling continues until the dura of the posterior fossa is encountered. The bone around the porous is completely removed exposing the dura. Drilling is then continued laterally along the internal auditory canal. Drilling continues until Bill's bar is reached.
PAUL GIDLEY: The remaining thin shell of bone over the internal auditory canal is removed with fish instruments. The dura of the internal auditory canal is then opened with a 5910 Beaver blade. The dura is reflected to show the facial nerve anteriorly and superior vestibular nerve posteriorly. A press probe is used to identify the facial nerve and to separate it from the superior vestibular nerve.
PAUL GIDLEY: The superior vestibular nerve is reflected posteriorly. And the tumor can be seen between it and the facial nerve. The superior vestibular nerve has then cut with microscissors to allow better visualization of the tumor from the inferior vestibular nerve. The tumor can then be elevated out of the internal auditory canal by severing its lateral attachment to the inferior vestibular nerve.
PAUL GIDLEY: The tumor is then carefully and bluntly separated from the facial nerve and the cochlear nerve, which is seen here as a bright white densely myelinated nerve.
PAUL GIDLEY: The facial nerve is then stimulated by the press probe to ensure its integrity. A portion of temporalis muscle is then harvested. This muscle is used to plug the defect in the internal auditory canal. Temporalis fascia is laid over the muscle plug to reconstruct the middle fossa.
PAUL GIDLEY: A bone chip is then placed over the defect in the petrous apex, and the middle fossa retractor is then removed. The craniotomy flap is placed back into its anatomic location, rigidly fixated with plates. The temporalis muscle and skin flaps are then closed in a watertight fashion. Patients are observed overnight in the ICU.
PAUL GIDLEY: An MRI is obtained the following day. And the patient is observed another 3 or 4 days until they meet discharge criteria. MRI 3 years later shows no evidence of disease. Postoperative audiogram shows class B hearing with an SRT of 35 and a discrim score of 88%.
SPEAKER: In our practice, we have found that patients with class A or B hearing preoperatively are able to maintain class A or B hearing and 62% of cases after undergoing middle cranial fossa of a section of acoustic neuroma.