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Table of Contents    
OPERATIVE NUANCES: STEP BY STEP (VIDEO SECTION)
Year : 2022  |  Volume : 70  |  Issue : 4  |  Page : 1366-1369

Cystic Vestibular Schwannoma Resection Through Suboccipital Retrosigmoid Approach


Neurosurgical Department of Changzheng Hospital, Neurosurgical Institute of Shanghai, Naval Medical University, China

Date of Submission10-Jun-2022
Date of Decision04-Aug-2022
Date of Acceptance05-Aug-2022
Date of Web Publication30-Aug-2022

Correspondence Address:
Lijun Hou
Neurosurgical Department of Changzheng Hospital, 415# Fengyang Road, Huangpu District, Shanghai
China
Yong Yan
Neurosurgical Department of Changzheng Hospital, 415# Fengyang Road, Huangpu District, Shanghai
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.355144

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  Abstract 




How to cite this article:
Yan Y, Jiang L, Bai R, Mei Q, Dai W, Hou L. Cystic Vestibular Schwannoma Resection Through Suboccipital Retrosigmoid Approach. Neurol India 2022;70:1366-9

How to cite this URL:
Yan Y, Jiang L, Bai R, Mei Q, Dai W, Hou L. Cystic Vestibular Schwannoma Resection Through Suboccipital Retrosigmoid Approach. Neurol India [serial online] 2022 [cited 2022 Oct 2];70:1366-9. Available from: https://www.neurologyindia.com/text.asp?2022/70/4/1366/355144

Yong Yan and Lei Jiang has contributed equally to the manuscript.
Key Message: Through careful patient selection, intraoperative nerve monitoring, and prudent surgical procedures, it was possible to achieve GTR of the cystic vestibular schwannoma and preserve facial nerve function.




Cystic vestibular schwannoma accounts for about 10% of all vestibular schwannomas.[1] It has a rapid growth rate, an increased propensity to infiltrate the facial nerve and has an unpredictable biological process. Surgical resection is the treatment of choice for long-term tumor control. The purpose of the procedure is to completely resect the tumor under a microscope while preserving neurological function.

Objective: In this video, we present a case of vestibular schwannoma totally resected with the facial nerve function fully preserved postoperatively.

Procedure: Using a retrosigmoid approach in a lateral position, the tumor was excised. A range of 5 mm × 6 mm was drilled into the posterior wall of the inner acoustic canal (IAC) to incise the IAC-infiltrating tumor. The anterior inferior cerebellar artery (AICA) was discovered to be completely encased by the tumor, and it was dissected and protected with care during surgery. The facial nerve was well preserved in the inferior and anterior regions of the tumor.

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Video timeline with audio transcript

00:00–00:08

We presented a case of vestibular schwannoma totally resected by retrosigmoid approach in lateral position with the facial nerve function fully preserved postop.

00:12–00:52

The patient is a woman who is 69 years old. She had a two-year history of right-sided hearing impairment. On admission, a loss of hearing in her right ear was discovered, but no other neurological symptoms. On the MR images, a 3.5 × 3 × 3 cm capsular tumor was visible in the right cerebellopontine (CP) angle. The inner acoustic meatus was found to be slightly enlarged by the tumor, and it was evident that the tumor had invaded it. On the CT images, there were also some high signals in the tumor capsules, indicating that the tumor was bleeding prior to surgery.

00:53–01:12

The patient was placed in a lateral position with a slightly elevated upper body. The patient's head was slightly bent forward, parallel to the floor, and fixed in a neutral position using head pins. During surgery, the orbicularis oculi and orbicularis oris were probed to monitor facial nerve function.

01:13–01:34

Cisternal cerebrospinal fluid (CSF) release, adequate drilling of the posterior wall of the inner acoustic canal, resection of the intra-meatus portion of the tumor, intracapsular tumor debulking, vessels and cranial nerve protection, and cautious hemostasis and closure are essential surgical steps.

01:35–01:55

Post-auricular S-shaped incision and standard suboccipital retrosigmoid approach were adopted [Figure 1]. A bur hole was made at the corner where the transverse sinus transitioned into the sigmoid sinus. Then a bone flap with a size about 4 × 4 cm was made.
Figure 1: The position and incision of the patient

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01:56–09:16

Under a microscope, CSF was released by opening the cerebellomedullary cistern and the cisterna magna. The tumor was then visible in the surgical field. After the probe determined that there was no facial nerve in the tumor's posterior wall, the tumor's capsule was punctured with needles and liquid was aspirated to reduce its size. The tumor's borders were then identified by tearing open the arachnoid membranes on its surface. To expose the posterior wall of the inner acoustic meatus, the adhesion of the tumor to the dura was dislodged in superior, inferior, and posterior directions. Sharp scalpels were used to make a C-shaped incision in the dura surrounding the posterior wall of the meatus. The dura was then detached from the bone to create a flap and turned inward to position the meatus' orifice. The posterior wall of the meatus was deboned using high-velocity drills with a coarse diamond bur. The meatus was opened within a 6 × 5 mm range. Using bipolar, the bleeding of the dura was carefully coagulated. The dura was then incised with microscissors parallel to the direction of the meatus, revealing the tumor's inner meatus portion. The probe was utilized once more to detect the facial nerve and as a microdissector. The interfaces between the tumor and the nerves were identified, and the tumor was separated from the nerves by peeling it from the outside in [Figure 2]. After the intra-meatus portion of the tumor was resected and the blood supply from the meatus dura was severed, the portion of the tumor beneath the cerebellum was addressed. Attempts were made to locate the interfaces between the tumor and cerebellum, and adhesions to the dura were excised using microscissors. After separating the tumor from the cerebellum, the tumor's capsule was cut open and the tumor's contents were extracted. It could be seen that the tumor's contents were soft and comprised of blood clots. All of these were extracted using forceps. After removing a portion of the capsule's contents, the tumor shrank further, and the assistant surgeon gently pulled the tumor to expose its deeper boundary. The arachnoid membrane on the surface of the tumor was separated from the capsule using sharp forceps and the tumor's small supplying arteries were coagulated and severed. The AICA was discovered in the upper portion of the tumor, running inferiorly at the interface of the tumor and brainstem, adhering to these structures. Microscissors were used to remove the adhesions and arachnoid binds from the AICA, and great care was taken to protect the vessel and its branches. The vessel and its branches were separated from the surrounding structures, including the tumor capsule, arachnid bind, and brain tissue, using a combination of sharp and blunt dissection. Although great care was taken to avoid damaging the vessel's branches, a small branch encased by the arachnoid sheath was severed during surgery. The branch's bleeding point was coagulated with bipolar at low power, and the arterial branch was successfully reserved to stop the bleeding. The course of the vessel dissection is also the course of separating the tumor capsule from the brainstem. After crossing the vessel's line, the brain stem could be seen in the field as a white color. This area was possibly the facial nerve's exit zone, so the probe was used once more to determine if there was a signal indicating the seventh cranial nerve. For the absence of a signal, the left capsule was continued to be dissected and removed. The capsule was dissected piece by piece with extreme caution to avoid damaging the seventh nerve. The trigeminal nerve was subsequently observed at the capsule's base [Figure 3]. The safe portion of the tumor was then removed. The last portion of the capsule to be dissected was the most in-depth portion of the tumor. Because it was extremely adherent to the surrounding structures, sharp dissection was again employed. Small arteries that supplied the tumor capsule were meticulously coagulated and severed, whereas large vessels that passed by were preserved. In the inferior portion of the tumor capsule, the seventh nerve was located [Figure 4]. The monitor displayed a strong facial nerve signal. In this instance, the seventh nerve was located below and in front of the tumor. The tumor likely originated from the superior vestibular nerve and compressed the seventh nerve and inferior vestibular nerve. The remainder of the tumor was removed from the inferior vestibular nerve. The small bleeding point on the nerves, brainstem, and cerebellum were meticulously coagulated. Lower cranial nerves were well preserved. The surfaces of these structures were covered with fragments of fibrillar surgicel. The wound was flushed with saline water to ensure there was no oozing blood. The dura, the skull, and the wound were routinely closed.
Figure 2: Drilling of the IAC and resection of the intracanalicular part of the tumor

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Figure 3: After tumor debulking, the trigeminal nerve and brainstem were shown under the bottom of the tumor

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Figure 4: After most of the tumor was resected, the facial nerve and inferior vestibular nerve were shown

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09:17–09:54

The postoperative recovery process was unremarkable. According to the House–Brackmann scale, the facial nerve function was graded as I. The tumor had been completely removed. On T2-weighted postoperative MRI, facial and inferior vestibular nerve fibers were visible. Pathological analysis suggested schwannoma, confirming the diagnosis before surgery. After eight days, the patient was discharged from the hospital.

Thanks for your attention!

Outcome: The tumor was completely excised, and the facial nerve function was grade I on the House–Brackmann scale after surgery. The patient recovered without incident and was discharged. After 1.5 years of follow-up, there are no indications of a recurrence of the tumor.


  Pearls and Pitfalls Top


Pearls

  1. By releasing the cyst fluid, the volume of the tumor can be decreased in order to delineate its border. However, tumor capsules typically contain septum, necessitating the continuous opening of smaller sacs during resection to adequately reduce tumor volume.
  2. The arachnoid interface is a surgeon's ally and must be safeguarded during tumor dissection. It could be torn from the tumor and left on the exteriors of the neurological structures. In cystic vestibular schwannoma, however, the arachnoid interface is frequently incomplete, especially at the tumor's deep surface. In these regions, sharp dissection is incredibly useful for isolating individuals.
  3. A combination of sharp and blunt dissection is required when the blood vessels are surrounded by the tumor wall. Sharp separation is used to loosen the band between the tumor and blood vessels, while blunt separation is used to locate and enlarge the tumor-vessel interface. Tracking along the long axis of the vessel is beneficial for clarifying the vessel's course and preventing injury. Low-power local coagulation and pressure are very useful for hemostasis in small arterial injuries.
  4. Intraoperative electrophysiological monitoring is essential for facial nerve function preservation. During tumor resection, especially at the tumor's deep borders, a monitoring probe must be used frequently to detect any structure that resembles the facial nerve or is in its path.
  5. Drilling the inner acoustic meatus has at least three benefits: resecting the intracanalicular portion of the tumor, controlling the blood supply from the IAC, and locating the facial nerve in the meatus canal. In acoustic neuroma surgery, a mastery of the drilling technique is essential.


Pitfall

The auditory brainstem responses were not monitored in the operation nor was the aspect of hearing preservation involved.


  Discussion Top


Cystic vestibular schwannoma has a rapid growth rate, an unpredictable biological process, and a propensity to invade the facial nerve. The treatments of cystic vestibular schwannoma include observation, surgical resection, and radiosurgery.[1] Some cystic vestibular schwannoma would rapidly expand after radiosurgery, and surgical resection is still the first choice of long-time control of the tumor.[2],[3]

The cystic vestibular schwannoma usually encases the vessels and is adhesive to the facial nerve, making it difficult to resect with fully preservation of neurological functions.[4] Tumors with central and thick walls can be removed in most cases. However, when peripheral thin-walled, adherent, cystic tumors are confronted and the cysts are medially or anteriorly located, it is difficult to excise them completely, and it is recommended to leave portions of cyst adherent to neurovascular structures for better preservation of facial nerve function.[5] The facial nerve function and the degree of excision depend on the type and location of the cyst, and their adherence to neurovascular structures in such cases.

Careful patient selection, intraoperative neurological monitoring, and prudent manipulations to protect vessels and nerves are critical to minimize surgical risks.[6–8] When the tumor cannot be separated from the important structures surrounding it (especially the brainstem), it is necessary to retain a portion of the cyst wall and not resect it.[5],[9],[10] Maximum benefit of the patient through surgery instead of gross total resection (GTR), should be the pursuit of the surgeon.


  Conclusions Top


By careful patient selection, intraoperative nerve functional monitoring, and prudent surgical procedures, GTR of cystic vestibular schwannoma could be achieved with well preservation of the facial nerve function through suboccipital retrosigmoid approach.

Patient's consent

A full and detailed consent from the patient's guardian has been taken. The patient's identity has been adequately anonymized. If anything related to the patient's identity is shown, adequate consent has been taken from the patient's guardian. The journal will not be responsible for any medico-legal issues arising out of issues related to patient's identity or any other issues arising from the public display of the video.

Financial support and sponsorship

Sponsored by Program of Shanghai Academic Research Leader (15XD1504700); Shanghai Medical Innovation research-key project of Shanghai Science and Technology Commission (21Y21900400); Major project of Logistic Support Department of PLA (AWS17J003).

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Metwali H, Samii M, Samii A, Gerganov V. The peculiar cystic vestibular schwannoma: a single-center experience. World Neurosurg 2014;82:1271-5.  Back to cited text no. 1
    
2.
Pollock BE, Driscoll CL, Foote RL, Link MJ, Gorman DA, Bauch CD, et al. Patient outcomes after vestibular schwannoma management: A prospective comparison of microsurgical resection and stereotactic radiosurgery. Neurosurgery 2006;59:77-85; discussion 77-85.  Back to cited text no. 2
    
3.
Stangerup SE, Caye-Thomasen P, Tos M, Thomsen J. The natural history of vestibular schwannoma. Otol Neurotol 2006;27:547-52.  Back to cited text no. 3
    
4.
Samii M, Matthies C. Management of 1000 vestibular schwannomas (acoustic neuromas): the facial nerve--preservation and restitution of function. Neurosurgery 1997;40:684-94; discussion 694-5.  Back to cited text no. 4
    
5.
Piccirillo E, Wiet MR, Flanagan S, Dispenza F, Giannuzzi A, Mancini F, et al. Cystic vestibular schwannoma: Classification, management, and facial nerve outcomes. Otol Neurotol 2009;30:826-34.  Back to cited text no. 5
    
6.
Gardner G, Robertson JH. Hearing preservation in unilateral acoustic neuroma surgery. Ann Otol Rhinol Laryngol 1988;97:55-66.  Back to cited text no. 6
    
7.
Samii M, Gerganov V, Samii A. Improved preservation of hearing and facial nerve function in vestibular schwannoma surgery via the retrosigmoid approach in a series of 200 patients. J Neurosurg 2006;105:527-35.  Back to cited text no. 7
    
8.
Samii M, Matthies C. Management of 1000 vestibular schwannomas (acoustic neuromas): Surgical management and results with an emphasis on complications and how to avoid them. Neurosurgery 1997;40:11-21; discussion 21-3.  Back to cited text no. 8
    
9.
Gormley WB, Sekhar LN, Wright DC, Kamerer D, Schessel D. Acoustic neuromas: Results of current surgical management. Neurosurgery 1997;41:50-8; discussion 58-60.  Back to cited text no. 9
    
10.
Samii M, Gerganov VM, Samii A. Functional outcome after complete surgical removal of giant vestibular schwannomas. J Neurosurg 2010;112:860-7.  Back to cited text no. 10
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]



 

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