Endoscopic Resection of Vestibular Schwannomas

Optimizing outcomes in multicompartmental brain tumor surgery: A comparative study of integrated endoscopic and microsurgical techniques versus endoscope-assisted microsurgery

BACKGROUND

Multicompartmental lesions within the central nervous system are challenging due to their complex anatomy. This study evaluates the efficacy, safety, and utility of hybrid endoscopic and microsurgery versus endoscope-assisted microsurgery(EAM) for excising these lesions.

METHODS

A retrospective comparative analysis was conducted on patients who underwent multicompartmental brain tumor surgery, utilizing either hybrid endoscopic and microsurgical techniques with the Endocameleon Hopkins telescope featuring a rotating lens system and knob (Karl Storz GmbH & Co., Tuttlingen, Germany), alternately used with a microscope (ZEISS PENTERO 800 S) (Group 1, n = 69), or endoscope-assisted microsurgery employing a fully high-definition, 45° angled endoscopic tool, QEVO®, integrated into the digital surgical microscope KINEVO 900 (Carl Zeiss Meditec, Oberkochen, Germany) as a plug-in feature (Group 2, n = 63), from July 2018 to March 2024. Data on demographics, clinical presentation, lesion characteristics, surgical details, and outcomes were meticulously collected and analyzed using rigorous statistical methods, including t-tests and chi-square tests.

RESULTS

Compared to Group 2, Group 1 had better ease of dissection and visualization of bleeders (p = 0.01) and fewer postoperative hematomas (p = 0.04). Surgical times were similar (p = 0.134). Postoperative follow-up revealed fewer recurrences in Group 1, though not statistically significant (p = 0.33). Group 1 patients reported higher cosmetic satisfaction and shorter hospital stays (p = 0.002). Logistic regression identified tumor vascularity(p = 0.001) and ease of dissection(p = 0.008) as significant factors for recurrence.

CONCLUSIONS

Hybrid endoscopic and microsurgery demonstrated superior intraoperative visualization, ease of dissection, and postoperative outcomes compared to endoscope-assisted microsurgery with the Quevo device. These findings suggest that the integrated approach may offer better outcomes for multicompartmental lesion excision regarding safety, efficacy, and patient satisfaction.

A multi-institutional machine learning algorithm for prognosticating facial nerve injury following microsurgical resection of vestibular schwannoma

Vestibular schwannomas (VS) are the most common tumor of the skull base with available treatment options that carry a risk of iatrogenic injury to the facial nerve, which can significantly impact patients' quality of life. As facial nerve outcomes remain challenging to prognosticate, we endeavored to utilize machine learning to decipher predictive factors relevant to facial nerve outcomes following microsurgical resection of VS. A database of patient-, tumor- and surgery-specific features was constructed via retrospective chart review of 242 consecutive patients who underwent microsurgical resection of VS over a 7-year study period. This database was then used to train non-linear supervised machine learning classifiers to predict facial nerve preservation, defined as House-Brackmann (HB) I vs. facial nerve injury, defined as HB II-VI, as determined at 6-month outpatient follow-up. A random forest algorithm demonstrated 90.5% accuracy, 90% sensitivity and 90% specificity in facial nerve injury prognostication. A random variable (rv) was generated by randomly sampling a Gaussian distribution and used as a benchmark to compare the predictiveness of other features. This analysis revealed age, body mass index (BMI), case length and the tumor dimension representing tumor growth towards the brainstem as prognosticators of facial nerve injury. When validated via prospective assessment of facial nerve injury risk, this model demonstrated 84% accuracy. Here, we describe the development of a machine learning algorithm to predict the likelihood of facial nerve injury following microsurgical resection of VS. In addition to serving as a clinically applicable tool, this highlights the potential of machine learning to reveal non-linear relationships between variables which may have clinical value in prognostication of outcomes for high-risk surgical procedures.

Retrosigmoid versus middle fossa approach for hearing and facial nerve preservation in vestibular schwannoma surgery: A systematic review and comparative meta-analysis

BACKGROUND

Vestibular schwannomas (VS) are benign tumors arising from vestibular nerve's Schwann cells. Surgical resection via retrosigmoid (RS) or middle fossa (MF) is standard, but the optimal approach remains debated. This meta-analysis evaluated RS and MF approaches for VS management, emphasizing hearing preservation and Cranial nerve seven (CN VII) outcomes stratified by tumor size.

METHODS

Systematic searches across PubMed, Cochrane, Web of Science, and Embase identified relevant studies. Hearing and CN VII outcomes were gauged using the American Academy of Otolaryngology-Head and Neck Surgery, Gardner Robertson, and House-Brackmann scores.

RESULTS

Among 7228 patients, 56 % underwent RS and 44 % MF. For intracanalicular tumors, MF recorded 38 % hearing loss, compared to RS's 54 %. In small tumors (<1.5 cm), MF showed 41 % hearing loss, contrasting RS's lower 15 %. Medium-sized tumors (1.5 cm-2.9 cm) revealed 68 % hearing loss in MF and 55 % in RS. Large tumors (>3cm) were only reported in RS with a hearing loss rate of 62 %.

CONCLUSION

Conclusively, while MF may be preferable for intracanalicular tumors, RS demonstrated superior hearing preservation for small to medium-sized tumors. This research underlines the significance of stratified outcomes by tumor size, guiding surgical decisions and enhancing patient outcomes.

Fully Endoscopic Retrosigmoid Approach for Cerebellopontine Angle Tumors

BACKGROUND

Fully endoscopic or endoscope-controlled approaches are essentially keyhole approaches in which rigid endoscopes are the sole visualization tools used during the whole procedure. At the early attempts of endoscope-assisted cranial surgery, it was noted that rigid endoscopes enabled overcoming the problem of suboptimal visualization when small exposures are used. The technical specifications and design of the currently available rigid endoscopes are associated with a group of unique features that define the endoscopic view and lay the basis for its superiority over the microscopic view during brain surgery. Fully endoscopic retrosigmoid approach for cerebellopontine angle tumors is a minimally invasive approach that is not routinely practiced by neurosurgeons, with few series published so far. Unfamiliarity with the technique, steep learning curve, and concerns about inadequate exposure, neurovascular injury, and decreased visibility may explain this fact. In this chapter we elaborate on the surgical technique and nuances of the fully endoscopic retrosigmoid approach and present an overview of the published series.

METHODS

From a prospective database of endoscopic procedures maintained by the senior author, clinical data, imaging studies, operative charts, and videos of cases undergoing fully endoscopic retrosigmoid approach for cerebellopontine angle tumors were retrieved and analyzed. The pertinent literature was also reviewed.

RESULTS

The surgical technique of the fully endoscopic retrosigmoid approach was formulated.

CONCLUSION

The endoscopic technique has many advantages over the conventional procedures. In our hands, the technique has proven to be feasible, efficient, and minimally invasive with excellent results.

Endoscope-assisted resection of brainstem cavernous malformations

Targeted surgical precision and minimally invasive techniques are of utmost importance for resectioning cavernous malformations involving the brainstem region. Minimisation of the surgical corridor is desirable but should not compromise the extent of resection. This study provides detailed information on the role of endoscopy in this challenging surgical task. A retrospective analysis of medical documentation, radiologic studies and detailed intraoperative video documentation was performed for all consecutive patients who underwent surgical resection of brainstem cavernous malformations between 2010 and 2020 at the authors’ institution. A case-based volumetry of the corticotomy was performed and compared to cavernoma dimensions. A total of 20 procedures have been performed in 19 patients. Neuroendoscopy was implemented in all cases. The mean size of the lesion was 5.4 (± 5) mm3. The average size of the brainstem corticotomy was 4.5 × 3.7 (± 1.0 × 1.1) mm, with a median relation to the cavernoma’s dimension of 9.99% (1.2–31.39%). Endoscopic 360° inspection of the resection cavity was feasible in all cases. There were no endoscopy-related complications. Mean follow-up was 27.8 (12–89) months. Gross-total resection was achieved in all but one case (95%). Sixteen procedures (80%) resulted in an improved or stable medical condition. Eleven patients (61.1%) showed further improvement 12 months after the initial surgery. With the experience provided, endoscopic techniques can be safely implemented in surgery for BSCM. A combination of neuroendoscopic visualisation and neuronavigation might enable a targeted size of brainstem corticotomy. Endoscopy can currently be considered a valuable additive tool to facilitate the preparation and resection of BSCM.

Endoscopic Far-Lateral Supracerebellar Infratentorial Approach for Petroclival Region Meningioma: Surgical Technique and Clinical Experience

BACKGROUND

The management of petroclival region meningioma remains the ultimate achievement in neurosurgery, because of the formidable technical challenges involved.

OBJECTIVE

To describe the technique and feasibility of the purely endoscopic far-lateral supracerebellar infratentorial approach (EF-SCITA) for the treatment of petroclival region meningiomas.

METHODS

We reviewed the clinical data of 10 consecutive cases of petroclival region meningiomas treated with the EF-SCITA from August 2018 to August 2020. The clinical outcomes were analyzed. The patient was placed in the lateral position, and then, a "C" shaped incision and craniotomy with exposed sigmoid and transverse sinuses were performed. With the endoscopic holder, endoscopic procedures were performed using standard 2-hand microsurgical techniques. Whether the tentorium or Meckel cave was handled depended on the tumor extension.

RESULTS

The mean diameter was 45 × 25 mm. Dizziness and headache were the main symptoms. All 10 patients achieved gross total or subtotal resection (Petroclival Meningioma Grade I-III) with good neurological outcomes. The EF-SCITA provides satisfactory, direct exposure to the petroclival region. Cranial nerve deficits are the main postoperative complications. Two patients had a trochlear nerve injury, 3 patients had transient facial paralysis, and 2 patients had oculomotor paralysis (1 total and 1 incomplete), but both of them recovered during the follow-up period. One patient experienced an ipsilateral superior cerebellar artery infarction, and another patient had transient hemiparesis.

CONCLUSION

The EF-SCITA is effective for most petroclival region meningiomas, except for the cavernous sinus type. This approach simplifies craniotomy procedures, omits burdensome petrosectomy, and avoids crossing posterior neurovascular structures.

Endoscope-Assisted Retrosigmoid Approach for Vestibular Schwannomas With Intracanalicular Extensions: Facial Nerve Outcomes

Objective

To explore the role of neuroendoscope assistance during surgical resection of the intracanalicular portion of vestibular schwannomas via the retrosigmoid approach and the subsequent early facial nerve outcomes.

Methods

Patients of vestibular schwannoma with intracanalicular extensions undergoing retrosigmoid dissection at a single institution were retrospectively analyzed in this study. Several surgical techniques were applied to ensure maximal and safe removal of tumors. Tumors extending less than 10 mm into the internal acoustic canal (IAC) were classified as Grade A, while those extending over 10 mm into IAC were taken as Grade B. Neuroendoscope was applied at the end of microscopic phase to search for potential remnants for Grade B tumors. Absolute tumor extension was defined and measured. House and Brackmann (HB) scale was used to evaluate immediate CN VII outcomes.

Results

Of the 61 patients, there were 38 females and 23 males. A total of 18 (29.51%) cases were Koos Grade II, 12 (19.67%) cases Koos Grade III, and 31 (50.82%) cases Koos Grade IV. There were 38 cases (62.30%) of Grade A and 23 cases (37.70%) of Grade B. Gross total resection was achieved in 60 cases (98.36%). Four cases of intracanalicular remnants were detected and completely removed under endoscopic visualizations. There was a significantly higher proportion (17%, p = 0.02) of intracanalicular remnants in Grade B than Grade A. CN VII and VIII were anatomically preserved in all cases. A total of 55 cases (90.16%) retained good (HB Grades 1 and 2) facial nerve outcomes.

Conclusions

In Grade B vestibular schwannomas, after maximal microsurgical removal, endoscopic evaluation of the intracanalicular portion revealed residual tumors in 17% of the patients. Hence endoscopic evaluation of the potential intracanalicular remnants for tumor extending over 10 mm within IAC (Grade B) is recommended.

The Role of Endoscopy in the Resection of Sporadic Vestibular Schwannomas: A Systematic Review of Surgical Outcomes

BACKGROUND

Vestibular schwannomas (VS) are benign intracranial tumors originating from the vestibular division of the eighth cranial nerve. Treatment options include microsurgery, radiotherapy, and surveillance. Endoscopy is becoming more widely used as an adjunct in skull base surgery and may influence outcomes in surgically managed VS.

METHODS

A systematic review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies involving endoscope-assisted and fully endoscopic procedures for sporadic VS resection were identified. Facial nerve function, hearing preservation, extent of resection, and complications were analyzed.

RESULTS

Thirty-one studies were included (27 endoscope-assisted, four fully endoscopic). Subgroup analyses were performed to assess outcomes according to tumor size and surgical approach. Overall, endoscopic facial nerve preservation rates were comparable to microsurgical treatment. A subgroup analysis suggested that functional facial nerve preservation rates may be higher when endoscopic assistance is used for smaller (Koos I-II) tumors using the retrosigmoid or translabyrinthine approach. The gross total resection rate for small tumors was higher in retrosigmoid ES-assisted microsurgery (96.2%) compared to rates in the literature for the standard, open retrosigmoid approach. Hearing outcomes were more variable and were under-reported.

CONCLUSIONS

Current data suggest that ES-assisted resection of sporadic VS is not inferior to microsurgical resection with respect to facial nerve outcomes and extent of resection. However, some ES series report poor hearing outcomes, which are under-reported in the literature. Further prospective studies are required to ascertain if endoscopic assistance can improve outcomes for VS resection, particularly for smaller (Koos I-II) tumors.

Clinical Studies and Pre-clinical Animal Models on Facial Nerve Preservation, Reconstruction, and Regeneration Following Cerebellopontine Angle Tumor Surgery-A Systematic Review and Future Perspectives

Background and purpose: Tumorous lesions developing in the cerebellopontine angle (CPA) get into close contact with the 1st (cisternal) and 2nd (meatal) intra-arachnoidal portion of the facial nerve (FN). When surgical damage occurs, commonly known reconstruction strategies are often associated with poor functional recovery. This article aims to provide a systematic overview for translational research by establishing the current evidence on available clinical studies and experimental models reporting on intracranial FN injury.

Methods: A systematic literature search of several databases (PubMed, EMBASE, Medline) was performed prior to July 2020. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. Included clinical studies were reviewed and categorized according to the pathology and surgical resection strategy, and experimental studies according to the animal. For anatomical study purposes, perfusion-fixed adult New Zealand white rabbits were used for radiological high-resolution imaging and anatomical dissection of the CPA and periotic skull base.

Results: One hundred forty four out of 166 included publications were clinical studies reporting on FN outcomes after CPA-tumor surgery in 19,136 patients. During CPA-tumor surgery, the specific vulnerability of the intracranial FN to stretching and compression more likely leads to neurapraxia or axonotmesis than neurotmesis. Severe FN palsy was reported in 7 to 15 % after vestibular schwannoma surgery, and 6% following the resection of CPA-meningioma. Twenty-two papers reported on experimental studies, out of which only 6 specifically used intracranial FN injury in a rodent (n = 4) or non-rodent model (n = 2). Rats and rabbits offer a feasible model for manipulation of the FN in the CPA, the latter was further confirmed in our study covering the radiological and anatomical analysis of perfusion fixed periotic bones.

Conclusion: The particular anatomical and physiological features of the intracranial FN warrant a distinguishment of experimental models for intracranial FN injuries. New Zealand White rabbits might be a very cost-effective and valuable option to test new experimental approaches for intracranial FN regeneration. Flexible and bioactive biomaterials, commonly used in skull base surgery, endowed with trophic and topographical functions, should address the specific needs of intracranial FN injuries.

Heads-up Surgery: Endoscopes and Exoscopes for Otology and Neurotology in the Era of the COVID-19 Pandemic

A new era of surgical visualization and magnification is poised to disrupt the field of otology and neurotology. The once revolutionary benefits of the binocular microscope now are shared with rigid endoscopes and exoscopes. These 2 modalities are complementary. The endoscope improves visualization of the hidden recesses through the external auditory canal or canal-up mastoidectomy. The exoscope provides an immersive visual experience and superior ergonomics compared with binocular microscopy. Endoscopes and exoscopes are poised to disrupt the standard of care for surgical visualization and magnification in otology and neurotology.

Is endoscopic inspection necessary to detect residual disease in acoustic neuroma surgery?

MAIN GOALS

To analyze how and when the endoscope is used in vestibular schwannoma surgery and identify the benefits of using endoscopy in this type of surgery.

BACKGROUND

It is currently unclear if there is any benefit from using an endoscope in vestibular schwannoma surgery so this retrospective analysis set out to study this.

METHODS

All the patients who underwent vestibular schwannoma surgery at our clinic were included for all the vestibular schwannoma approaches taken. We studied when endoscopy was used during surgery and the goal of using endoscopy. Several pre- and postoperative factors were assessed such as complications, facial function, and hearing function in the case of techniques that allow hearing preservation.

RESULTS

From January 2015 to September 2018, 280 patients underwent lateral skull base surgery. Of these, 112 were included in this study. The endoscope was used in all 112 patients, and in eight cases it was possible to identify residual disease using the endoscope to check the surgical field, and then to remove the disease under endoscopic view. Moreover, in two other cases, the endoscope was used to resolve a vasculoneural conflict between the anterior inferior cerebellar artery (AICA) loop and facial nerve in one case, and for deafferentation of the superior and inferior vestibular nerves in the second case. No major intraoperative complications occurred in our series. There was no statistically significant difference in postoperative facial nerve function between patients in whom the endoscope was used as a diagnostic tool and patients in whom it was used as an operative tool (p = 0.3152).

CONCLUSIONS

The endoscope may be useful, especially in surgical techniques where there is poor control of the internal auditory canal (IAC). An endoscopic support technique is strongly recommended to avoid residual disease, particularly in retrosigmoid and retrolabyrinthine approaches. Moreover, the recent introduction of the transcanal transpromontorial approach allows the endoscope to be used during all the procedures in patients affected by a vestibular schwannoma limited to the IAC or to support surgical procedures during an enlarged microscopic approach.

Minimally Invasive Endoscopic Retrosigmoid Approach to the Cerebellopontine Angle Using a Novel Surgical Instrument: A Cadaveric Study

OBJECTIVES

In this study, we aimed to describe how endoscopes show the neural and vascular structures at the cerebellopontine angle (CPA) through a minimal craniotomy in a well-described anatomic point in the retrosigmoid region and at the same time, evaluate the endoscopic anatomic exposure and maneuverability. We planned to use the new surgical instrument (endoscope cannula), which we designed on fresh frozen cadavers to simulate a real surgical procedure.

MATERIALS AND METHODS

The surgical procedure was planned to be performed on 20 sides of 10 fresh cadaver heads. The distance between the asterion and mastoid process was determined, and the midpoint was then marked. From this midpoint, a craniotomy 2 cm in size was posteriorly made. The endoscope cannula together with 0° or 30° endoscopes was inserted to capture the panoramic views of the neurovascular structures in CPA. Endoscopic anatomic exposure and maneuverability were evaluated using 0° and 30° endoscopes with/without the endoscope cannula.

RESULTS

The surgeon could easily use both hands during the surgical simulation, and maneuverability was seen to increase in CPA with the use of the endoscope cannula.

CONCLUSION

The surgeon can work actively with both hands when the endoscopes and the endoscope cannula are used together. We believe that owing to this, the surgeon's maneuverability would increase and a more effective minimally invasive endoscopic retrosigmoid surgery would ensue.

Retrolabyrinthine Meatotomy as Part of Retrosigmoid Approach to Expose the Whole Internal Auditory Canal: Rationale, Technique, and Outcome in Hearing Preservation Surgery for Vestibular Schwannoma

BACKGROUND

Vestibular schwannoma extending to the fundus of the internal auditory canal is currently considered an unfavorable condition for hearing preservation surgery via a retrosigmoid approach because the lateral end of the canal is hard to view directly during microsurgery.

OBJECTIVE

To present an improved retrolabyrinthine meatotomy (RLM) technique that enables the full length of the cochlear and facial nerves to be inspected up to their orifices on the fundus. Long-term results are briefly reported.

METHODS

A consecutive series of 100 cases with various degrees of fundus involvement underwent surgery via a retrosigmoid approach and RLM. The follow-up ranged from 4 to 14 yr. Outcomes on hearing and facial nerve function were recorded, and preoperative MRI findings of the tumor on the fundus were correlated with the surgical findings and the long-term radicality of the tumor resection.

RESULTS

Residual tumor on the fundus was identified in 3 cases, all belonging to the group with tumors adhering to the fundus. The functional results were in line with the best reported outcomes of this surgery.

CONCLUSION

RLM via a retrosigmoid approach seemed adequate for the purposes of hearing preservation surgery and enabled the full course of the facial and cochlear nerves through the internal auditory canal to be exposed to direct view. Tumors adhering to the vestibular quadrant of the fundus were more difficult to remove, and there were a few cases of local residual tumor.