Name:
Right medium-sized vestibular schwannoma with trigeminal neuralgia post-fractionated radiotherapy
Description:
Right medium-sized vestibular schwannoma with trigeminal neuralgia post-fractionated radiotherapy
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Duration:
T00H10M16S
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https://cadmoreoriginalmedia.blob.core.windows.net/e5384bac-62be-4300-966a-d607e8db3e31/21-112.mp4?sv=2019-02-02&sr=c&sig=B0UJNScOH3L3NoDtT5f9PcaeRWQxxWF1fTqwo3gIiCI%3D&st=2024-05-05T05%3A25%3A15Z&se=2024-05-05T07%3A30%3A15Z&sp=r
Upload Date:
2021-10-27T00:00:00.0000000
Transcript:
Language: EN.
Segment:0 .
[MUSIC PLAYING]
SPEAKER: Here we describe a recessionary right medium-sized vestibular schwannoma with trigeminal neuralgia postfractionated radiotherapy. Patient is a 51-year-old female with right-sided V2 trigeminal pain who was found to have a vestibular schwannoma that underwent fractionated radiotherapy with 48.6 Gy, 27 fractions over a 2-month period at an outside institution. She had sharp, persistent, lightning-type pain 6 months after radiotherapy.
SPEAKER: By exam, there was reduced pinprick sensation of V1 and V2, down to the angle of the jaw on the right side. Her facial nerve was intact with no overt signs of vestibulopathy. Preoperative audiogram demonstrated moderate hearing loss in the right ear with greater than 25 dB of hearing loss in that ear. Axial T1 contrast-enhanced MRI is demonstrates an inhomogeneously enhancing tumor that extends all the way to the fundus.
SPEAKER: Axial FIESTA imaging demonstrates that the tumor is compressing the trigeminal nerve root entry zone, as well as distorting the pons. Although the patient had recently been treated with a fractionated radiotherapy, her trigeminal pain had persisted and worsened over several months, and thus my rationale was to intervene at this point to give her the best chance of pain relief, especially because she had failed medical management.
SPEAKER: The patient is positioned in the lateral decubitus position with the head positioned in a Mayfield head holder. An operative microscope is used, and neuromonitoring was used for cranial nerves 5, 7, 8, and 11, although a good brainstem auditory evoked response was not obtained in the right ear. Key surgical steps include making sure that the anteroinferior edge of the craniotomy is extended all the way down to the end of the sigmoid sinus to allow access to the lower cranial nerves.
SPEAKER: In addition, lower cranial nerve should be identified early on during the cisternal dissection, and an intrafloccular approach could be used to identify the facial nerve. Decompression of the trigeminal nerve root entry zone is a key to treating this patient's trigeminal neuralgia. After the durotomy is performed, the cerebrospinal fluid drainage from the cisterns is allowed to relax and remain at the cerebellum. And then, the remainder of the durotomy is opened.
SPEAKER: Surgicel is used to line the cerebellum prior to operation. Arachnoid dissection around the lower cranial nerves as done, and the accessory, or 11th, cranial nerve is identified early on. Arachnoid dissection is then carried around pica. And the lower cranial nerves, including 9, 10, and 11 are identified. When the petrosal vein is superficial and seems to be tethering the cerebellum, we do not hesitate to take it, as is routinely done from microvascular decompression.
SPEAKER: And peritumoral arachnoid dissection is then performed along the posterior aspect of the tumor to allow for points to be identified, along with the cerebellum. After the tumor capsule is stimulated and no facial nerve is identified, the tumor capsule is coagulated, and a window is cut into the tumor all the way to the porus acusticus to allow for early internal debulking and maneuverability around the edges of the tumor.
SPEAKER: An ultrasonic aspirator is used to debulk the inside of the tumor to allow for more efficient manipulation of the tumor superior. Dissection is carried around the tumor capsule after the seventh nerve is stimulated and the course of the seventh nerve is identified. Here, you can see that we're dissecting tumor off of the cerebellar surface. And this is significantly harder secondary to the fact that the patient had prior radiotherapy.
SPEAKER: We then carry on the dissection along the posterior edge of the capsule from the proximal vestibular cochlear nerve and identify where the nerves plays out. It became apparent that we were not going to be able to achieve the goals of the operation and save the eighth nerve, largely because of the tumor size prior to radiation and the adherence of the tumor to the nerve.
SPEAKER: While we could identify it, the fact that it was running along the dorsal aspect of the tumor meant that we probably would likely have to sacrifice it to safely and efficiently dissect the tumor away from the facial nerve. Here, we continued to dissect the tumor along the nerve. And at this point, we work to identify where the facial nerve is, as well.
SPEAKER: Neurostimulation helps at this point, as well. We then stimulate along the eighth nerve to confirm its location and confirm the location of the seventh nerve, as well. And we debulk the tumor to allow for safer and easier manipulation without manipulation of the facial nerve and traction on the facial nerve. We then carry the dissection to the superior edge of the tumor after having identified the course of the facial nerve.
SPEAKER: And we dissect between the trigeminal nerve and the tumor capsule. We untether the superior cerebellar artery from the trigeminal nerve. And here, we can see a view of the fourth cranial nerve, the superior cerebellar artery, and the trigeminal nerve. On the back end of the tumor, we identify where the cochlear nerve is, as well as in the cistern.
SPEAKER: Deep, we can see cranial nerve 6. We identify the split nerves of cranial nerve 7 and stimulate it to verify. Sharp dissection with microdissectors, including a Rhoton 11, is used along the back edge of the tumor capsule. And after stimulation along the back edge of the tumor capsule to identify the exact fibers of the seventh nerve, this area is sharply incised and dissected off of the back of the tumor capsule.
SPEAKER: Here, you can see a combination of microinstruments used to develop this plane between the tumor and the seventh nerve. We debulk the tumor to limit manipulation of the seventh nerve, particularly around the porus acusticus, given that it's tethered to the bony region. After this is done, Gelfoam is placed along cranial nerve 6 and the cisterns.
SPEAKER: Dura is coagulated along the petrous bone, and an ultrasonic aspirator with a bone-cutting bit is used to drill the porus acusticus. During this process, the superior trough is created. The bone is then taken off of the entire porus acusticus, and the dura is coagulated and then sharply incised and opened.
SPEAKER: At this point, the tumor is incised distally. And then, micro dissectors are used in a combination along the facial nerve from both proximal and distal to dissect the tumor off of the facial nerve. Here, we can see that the tumor is in the internal auditory canal and excised until normal neural structures are identified, including the cochlear nerve and facial nerve.
SPEAKER: Microdissectors, including the Koavar, are used to pull the tumor from the distal internal auditory canal after the correct point is identified. Here, we can see the beginning of the facial nerve that was initially stimulated and identified. Tumor is dissected from distal to proximal. And here, you can see cranial nerve 7 and 8 identified in the distal porus acusticus.
SPEAKER: Microdissectors and round dissectors are used to sharply dissect the tumor and tumor capsule off the nerve again, being a slightly more challenging dissection secondary to prior radiotherapy. The facial nerve is identified, and tumor is debulked off the nerve at the entry to the porus acusticus. Here, you can see, after stimulation, we sharply incise that boundary and an Apfelbaum mirror is used to inspect the distal internal auditory canal.
SPEAKER: The motor branch of the trigeminal nerve is stimulated and identified and Teflon pledgets are used in typical fashion for microvascular decompression to protect the trigeminal nerve root entry zone. Making sure we have adequate decompression at the entry zone is important. And here, we see anatomy of the superior cerebellar artery all the way down to cranial nerve 6.
SPEAKER: Dural sealant is applied after the drilled surface is bone waxed. Postoperative axial T1 contrast-enhanced MRIs demonstrate that there's a gross total resection. The patient had a resolution of her trigeminal pain and was weaned off all medication. Her facial nerve was intact, but hearing was not preserved. Again, we see the postoperative FIESTA imaging, demonstrating cranial nerve 5 and cranial nerve 7 after the decompression of the trigeminal nerve root entry zone.
SPEAKER: There are several learning points from this case. First is the early identification of the lower cranial nerves and the origin of the facial and vestibulocochlear nerve are key to determining the operative corridors for resection of vestibular schwannomas. Next is identifying the trigeminal nerve root entry zone and motor branch are key to dissecting out the trigeminal nerve and treating this patient's trigeminal neuralgia.
SPEAKER: Finally, fractionated radiotherapy does not sufficiently and effectively treat trigeminal neuralgia/neuropathy secondary to compression of the nerve root by vestibular schwannoma.