Name:
Resection of a meningioma, vestibular schwannoma, and placement of auditory brainstem implant using translabyrinthine approach
Description:
Resection of a meningioma, vestibular schwannoma, and placement of auditory brainstem implant using translabyrinthine approach
Thumbnail URL:
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Duration:
T00H09M59S
Embed URL:
https://stream.cadmore.media/player/4304e10e-daf3-4c94-9821-c18055c10649
Content URL:
https://asa1cadmoremedia.blob.core.windows.net/asset-ed644406-387c-4a40-88cf-4793910cebcb/21-63.mp4
Upload Date:
2021-08-30T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[MUSIC PLAYING]
SPEAKER1: We are presenting the case of a resection of a meningioma and vestibular schwannoma in NF-2 and the placement of an ABI through a translabyrinthine approach in a 34-year-old female with NF-2 and multiple tumors, losing hearing on the left side that has failed Avastin as well as twice Gamma Knife to the left tumor. Here is the audiogram showing anacusis on the left side.
SPEAKER1: One can appreciate on the MRI the multiple meningiomas and the bilateral acoustic neuromas. The region of interest is on the left side. The rationale for doing the procedure is a complete loss of hearing on the left side, tumor growth, failure of previous radiosurgery twice, and her young age with an opportunity to train her on the ABI before she loses hearing on the right ear.
SPEAKER1: Risks of the procedure include infection, hematoma, facial nerve weakness, incorrect placement of the ABI, occasionally death. The benefits are of course tumor control and possibly hearing restoration to the left ear. The alternatives do not include radiosurgery anymore because she has had already twice the procedure done. We could certainly consider observation.
SPEAKER1: The setup includes supine position with a shoulder bump for a translabyrinthine approach with the head turned 45 degrees. The necessary equipment includes the usual neuro-otologic and neurosurgical equipment, as well as intraoperative monitoring. The translabyrinthine approach is shown here, having been well underway on the left side. The neuro-otologist performs this part of the procedure.
SPEAKER1: Here the incus is removed to allow much better access to the Eustachian tube in order to pack it with Surgicel and fat to prevent CSF leak. The sigmoid sinus can be decompressed further both presigmoid and retrosigmoid. The sinodural angle is being exposed here at the junction between the middle and the posterior fossa.
SPEAKER1: Diamond drilling is being used close to the dura after having used the cutting drill earlier in the drilling. The retrosigmoid decompression is important, particularly when there are large tumors. The labyrinthectomy now is underway, particularly with a superior semicircular canal here being delineated in a circular fashion.
SPEAKER1: The fallopian canal is delineated. The lateral semicircular canal, the lumen of which is well seen. The sigmoid sinus is mobilized posteriorly. And here is the presigmoid dura with the endolymphatic duct and endolymphatic sac. One can appreciate the direction of Donaldson line.
SPEAKER1: Now as we are approaching the internal auditory canal, the inferior trough is being delineated and drilled. The jugular bulb is noted and is not particularly high in this case. The outline of the canals are drawn here-- lower torque and much finer drill that we like to use in the deep skull base surgery.
SPEAKER1: It is covered all the way to the drill bit and therefore much safer. This is the superior trough of the internal auditory canal being delineated with the diamond drill bit. After drilling, the schematic demonstrates the location of the nerves. Now it is time to open the dura. The first cut is usually parallel and interior to the sigmoid.
SPEAKER1: And normally for an acoustic neuroma one would see cerebellum at this point. But here we encountered the expected presigmoid meningioma that is piecing the schwannoma interior to it. We resect the meningioma of the cerebellar surface along with the dura. After resecting the meningioma, one can appreciate the vestibular schwannoma immediately interior to it.
SPEAKER1: And now it is important to delineate where the facial nerve is. Here we are colder to the tumor. And we are using nerve hook. And here we are using the NIM stimulator to define the facial nerve, which is well seen. It is displaced enteral superiorly. As expected, the tumor having been irradiated twice with Gamma Knife, is quite fibrous and not particularly suckable.
SPEAKER1: The plane with the brainstem is seen and meticulously defined. The facial nerve is splayed on the tumor, and therefore it is essential to use sharp dissection with piecemeal removal to avoid avulsing the nerve or causing a vascular injury in it. At this point in the dissection, we used a disposable, very sharp round knife to get closer to the nerve, but it was not possible to be in the extra capsular plane of the tumor.
SPEAKER1: Therefore a small nest of tumor is left attached on the nerve. Here is a dissection and a schematic from Rhoton to remind us where choroid plexus, flocculus, and lateral recess of the fourth ventricle are. Here, we are defining the choroid plexus of the lateral recess in order to enter the fourth ventricle. Here is an excellent view inside the fourth ventricle through the lateral recess where the electrode will be placed.
SPEAKER1: We are here placing the ABI receiver in a subcutaneous pocket. Here is the electrode end of the ABI. Again, the goal is to enter the lateral recess of the fourth ventricle, to place it on top of the cochlear nuclei area through the foramen of Luschka.
SPEAKER1: Naturally the correct surface of the electrode has to be placed down on the brainstem floor. We like to use that plastic around the excrescence on the electrode to push the paddle in. Here is a schematic of where the various nuclei are in the floor of the fourth ventricle overlaid on a Rhoton dissection.
SPEAKER1: The goal is of course not to push the electrode paddle too deep. Otherwise we would reach the vagal and hypoglossal trigone or the medial longitudinal fasciculus and the other long tract of the floor of the fourth ventricle. The audiology team will then confirm correct placement by interrogating a pair of electrodes and to make sure we are on top of the cochlear area.
SPEAKER1: ABI Is the most common placed stimulator in the CNS. It was first developed in the 1970s at the House Ear Institute. The patient remained neurologically intact. She currently has 15 out of the 21 electrodes active. Two of the electrodes are turned off because of a sensation in her throat. And four of them are turned off because they are stimulating probably the medial longitudinal fasciculus.
SPEAKER1: She has improved significantly in her lip-reading ability when the implant is turned on. A postoperative MRI showed essentially gross-total resection of the acoustic neuroma. And here are some relevant references. Thank you.
