Do facial nerve displacement pattern and tumor adhesion influence the facial nerve outcome in vestibular schwannoma surgery?

Predictive value of Blink reflex and facial corticobulbar motor evoked potential in cerebellopontine angle tumor surgery

OBJECTIVE

The current study examined the efficacy of the facial corticobulbar motor evoked potentials (FCoMEPs) and blink reflex (BR) on predicting postoperative facial nerve function during cerebellopontine angle (CPA) tumor surgery.

METHODS

Data from 110 patients who underwent CPA tumor resection with intraoperative FCoMEPs and BR monitoring were retrospectively reviewed. The association between the amplitude reduction ratios of FCoMEPs and BR at the end of surgery and postoperative facial nerve function was determined. Subsequently, the optimal threshold of FCoMEPs and BR for predicting postoperative facial nerve dysfunction were determined by receiver operating characteristic curve analysis.

RESULTS

Valid BR was record in 103 of 110 patients, whereas only 43 patients successfully recorded FCoMEP in orbicularis oculi muscle. A reduction over 50.3% in FCoMEP (O. oris) amplitude was identified as a predictor of postoperative facial nerve dysfunction (sensitivity, 77.1%; specificity, 83.6%). BR was another independent predictor of postoperative facial nerve deficit with excellent predictive performance, especially eyelid closure function. Its optimal cut-off value for predicting long-term postoperative eyelid closure dysfunction was was 51.0% (sensitivity, 94.4%; specificity, 94.4%).

CONCLUSIONS

BR can compensate for the deficiencies of the FCoMEPs. The combination of BR and FCoMEPs can be used in CPA tumor surgery.

SIGNIFICANCE

The study first proposed an optimal cut-off value of BR amplitude deterioration (50.0%) for predicting postoperative eyelid closure deficits in patients undergoing CPA tumor surgery.

Refining the predictive value of preoperative apparent diffusion coefficient (ADC) by whole-tumor analysis for facial nerve outcomes in vestibular schwannomas

BACKGROUND

Apparent diffusion coefficient (ADC) in MRI has been shown to correlate with postoperative House-Brackmann (HB) scores in patients with vestibular schwannoma despite limited methodology. To rectify limitations of single region of interest (ROI) sampling, we hypothesize that whole-tumor ADC histogram analysis will refine the predictive value of this preoperative biomarker related to postoperative facial nerve function.

METHODS

Of 155 patients who underwent resection of vestibular schwannoma (2014-2020), 125 patients were included with requisite clinical and radiographic data. After volumetric analysis and whole-tumor ADC histogram, regression tree analysis identified ADC cutoff for significant differences in HB grade. Outcomes were extent of resection, facial nerve function, hospital length of stay (LOS), and complications.

RESULTS

Regression tree analysis defined three quantitative ADC groups (× 10-6 mm2/s) as high (> 2248.77; HB 1.7), mid (1468.44-2248.77; HB 3.1), and low (< 1468.44; HB 2.3) range (p 0.04). The mid-range ADC group had significantly worse postoperative HB scores and longer hospital LOS. Large tumor volume was independently predictive of lower rates of gross total resection (p <0.0001), higher postoperative HB score (p 0.002), higher rate of complications (p 0.04), and longer LOS (p 0.003).

CONCLUSIONS

Whole-tumor histogram yielded a robust regression tree analysis that defined three ADC groups with significantly different facial nerve outcomes. This likely reflects tumor heterogeneity better than solid-tumor ROI sampling. Whole-tumor ADC warrants further study as a useful radiographic biomarker in patients with vestibular schwannoma who are considering surgical resection.

An Artificial Neural Network Model for Predicting Postoperative Facial Nerve Outcomes After Vestibular Schwannoma Surgery

BACKGROUND AND OBJECTIVES

The emergence of machine learning models has significantly improved the accuracy of surgical outcome predictions. This study aims to develop and validate an artificial neural network (ANN) model for predicting facial nerve (FN) outcomes after vestibular schwannoma (VS) surgery using the proximal-to-distal amplitude ratio (P/D) along with clinical variables.

METHODS

This retrospective study included 71 patients who underwent VS resection between 2018 and 2022. At the end of surgery, the FN was stimulated at the brainstem (proximal) and internal acoustic meatus (distal) and the P/D was calculated. Postoperative FN function was assessed using the House-Brackmann grading system at discharge (short-term) and after 9-12 months (long-term). House-Brackmann grades I-II were considered good outcome, whereas grades III-VI were considered fair/poor. An ANN model was constructed, and the performance of the model was evaluated using the area under the ROC curve for internal validation and accuracy, sensitivity, specificity, and positive and negative predictive values for external validation.

RESULTS

The short-term FN outcome was grades I-II in 57.7% and grades III-VI in 42.3% of patients. Initially, a model using P/D had an area under the curve of 0.906 (internal validation) and an accuracy of 89.1% (95% CI: 68.3%-98.8%) (external validation) for predicting good vs fair/poor short-term FN outcomes. The model was then refined to include only muscles with a P/D with a proximal latency between 6 and 8 ms. This improved the accuracy to 100% (95% CI: 79%-100%). Integrating clinical variables (patient's age, tumor size, and preoperative HB grade) in addition to P/D into the model did not significantly improve the predative value. A model was then created to predict the long-term FN outcome using P/D with latencies between 6 and 8 ms and had an accuracy of 90.9% (95% CI: 58.7%-99.8%).

CONCLUSION

ANN models incorporating P/D can be a valuable tool for predicting FN outcomes after VS surgery. Refining the model to include P/D with latencies between 6 and 8 ms further improves the model's prediction. A user-friendly interface is provided to facilitate the implementation of this model.

Analysis of Related Factors Affecting Facial Nerve Function after Acoustic Neuroma Surgery

Objective

To investigate the factors affecting facial nerve function after acoustic neuroma surgery and to provide theoretical reference for clinicians to preserve facial nerve function better after surgery.

Methods

A retrospective cohort study was conducted to analyze the correlation between postoperative facial nerve function and surgical approach, age, sex, tumor size and adhesion degree of facial nerve in 152 patients with acoustic neuroma.

Results

In the choice of surgical approach, there was no significant difference in the anatomy of the complete facial nerve in labyrinth path, retrosigmoid sinus path, and middle cranial fossa path. There was no statistically significant difference between the middle cranial fossa path and the retrosigmoid sinus path in facial nerve function preservation 7 days after surgery. The difference between middle cranial fossa path and labyrinthine path was statistically significant (P < 0.01). There were statistically significant differences between labyrinth path and retrosigmoid sinus path (P < 0.05). Logistic multivariate regression analysis showed that the operative approach and the degree of adhesion between tumor and facial nerve were the risk factors affecting functional preservation of facial nerve 7 days after surgery. Age and the degree of adhesion between tumor and facial nerve were the risk factors for functional preservation of facial nerve 1 year after operation.

Conclusion

The facial nerve function injury in patients with acoustic neuroma may be related to the choice of surgical approach, the adhesion degree of tumor and facial nerve, and their age. Clinicians need to comprehensively evaluate the risk factors before surgery, so as to achieve individualized treatment to protect the integrity of postoperative facial nerve function of patients.

Application of Subperineural Resection Technique in Vestibular Schwannomas: Surgical Efficacy and Outcomes in 124 patients

Objective

We aimed to explore the application and prospects of the subperineural resection technique for tumor separation and removal under the perineurium during surgery for vestibular schwannomas (VSs).

Methods

This study retrospectively analyzed 124 patients with VSs who underwent surgery via a retrosigmoid approach from July 2015 to October 2020 in the Department of Neurosurgery, Tangdu Hospital, Air Force Military Medical University. The data will be discussed with regard to the following aspects: clinical features, surgical strategies, tumor resection extent, facial–acoustic function preservation, and postoperative complications.

Results

Gross total resection (GTR) of the tumor was achieved in 104 patients, with a GTR rate of 83.9%, and subtotal resection (STR) of the tumor was achieved in 20 patients. There was no significant difference in facial and acoustic nerve functional preservation between GTR and STR, as well as in tumor resection between solid and cystic tumors. The retention rate reached 97.6% in terms of complete anatomical facial nerve preservation. Facial nerve function was assessed using the House–Brackmann (HB) grading score. Consequently, HB grades of I–II, III–IV, and V–VI were determined for 96 (77.4%), 25 (20.2%), and 3 (2.4%) cases, respectively, 1 week postoperatively and accounted for 110 cases (88.7%), 13 cases (10.5%), and 1 case (0.8%), respectively, at 6 months. Fifteen of 35 (42.9%) patients with serviceable hearing before the operation still had serviceable hearing at 6 months postoperatively. There were 5 cases of cerebellar or brainstem bleeding after the operation, and one patient died. Multivariate logistic regression analysis showed that older age (≥60 years, p = 0.011), large tumor (>3 cm, p = 0.004), and cystic tumor (p = 0.046) were independent risk factors associated with the extent of adhesion between the tumor and the brainstem and facial–acoustic nerve.

Conclusion

We successfully applied the subperineural resection technique to a large series of patients with VSs and achieved satisfactory results. Accurate identification of the perineurium and subperineural resection of the tumor can effectively reduce the disturbance of the facial–acoustic nerve during the operation and provide an intuitive basis for judging the tumor boundary. The subperineural resection technique may be conducive to improving the rate of total tumor resection and facial–acoustic nerve functional preservation in the surgical treatment of VSs.

Nomogram for Predicting Facial Nerve Outcomes After Surgical Resection of Vestibular Schwannoma

Objective

The facial nerve (FN) outcomes after vestibular schwannoma surgery seriously affect the social psychology and quality of life of patients. More and more attention has been paid to the protection of FN function. This study aimed to identify significant prognostic factors for FN outcomes after vestibular schwannoma surgery and create a new nomogram for predicting the rates of poor FN outcomes.

Methods

Data from patients who had undergone operations for vestibular schwannoma between 2015 and 2020 were retrieved retrospectively and patients were divided into good and poor FN outcomes groups according to postoperative nerve function. The nomogram for predicting the risk of poor FN outcomes was constructed from the results of the univariate logistic regression analysis and the multivariate logistic regression analysis of the influencing factors for FN outcomes after surgical resection of vestibular schwannoma.

Results

A total of 392 participants were enrolled. The univariate logistic regression analysis revealed that age, tumor size, cystic features of tumors, cerebrospinal fluid (CSF) cleft sign, tumor adhesion to the nerve, learning curve, and FN position were statistically significant. The multivariate logistic regression analysis showed that age, tumor size, cystic features of tumors, CSF cleft sign, tumor adhesion to the nerve, learning curve, and FN position were independent factors. The nomogram model was constructed according to these indicators. At the last follow-up examination, a good FN outcome was observed in 342 patients (87.2%) and only 50 patients (12.8%) was presented with poor FN function. Application of the nomogram in the validation cohort still gave good discrimination [area under the curve (AUC), 0.806 (95% CI, 0.752–0.861)] and good calibration.

Conclusion

This study has presented a reliable and valuable nomogram that can accurately predict the occurrence of poor FN outcomes after surgery in patients. This tool is easy to use and could assist doctors in establishing clinical decision-making for individual patients.

Vestibular Schwannomas in Young Patients: A 12-Year Experience in a Single Center

OBJECTIVE

This study evaluated the characteristics of vestibular schwannomas (VS) in young patients, including clinical features, treatment, prognosis, and histopathologic characteristics.

METHODS

We retrospectively reviewed medical records and follow-up data for 36 pediatric patients <21 years of age who were surgically treated for VS in the Chinese PLA General Hospital between 2008 and 2019.

RESULTS

Mean patient age was 17.4 years. Mean tumor size was 2.8 cm. Hearing loss (n = 32, 88.9%) and tinnitus (n = 20, 55.6%) were the most common symptoms. Ten patients (27.8%) had impaired facial nerve function after surgery. Gross total resection (GTR) was achieved in 26 cases (72.2%). The median tumor Ki-67 level was 5%. Tumor size was related to incomplete tumor resection (odds ratio, 0.2; 95% confidence interval, 0.1-0.9) and postoperative facial nerve dysfunction (odds ratio, 24.9; 95% confidence interval, 1.2-539.1). Tumor size was nonlinearly associated with prognosis and 2.2 cm corresponded to the inflection point at which the probability of tumor remnant and postoperative facial nerve dysfunction significantly increased. The GTR and low Ki-67 groups achieved better 3-year tumor control rate. Histopathologic findings confirmed the presence of cellular schwannoma subtype in young patients.

CONCLUSIONS

Tumor size is an important factor affecting the prognosis of VS in young patients. For large VS, surgical treatment should be the first choice, rather than wait-and-scan. VS in young patients shows high tumor proliferation and a tendency to relapse. The cellular schwannoma subtype requires special attention; an accurate histopathologic diagnosis is necessary for young patients with VS, and a closer follow-up strategy should be adopted for cellular VS.

Value of intraoperative monitoring of the trigeminal nerve in detection of a superiorly displaced facial nerve during surgery for large vestibular schwannomas

The aim of this study was to investigate the role of trigeminal and facial nerve monitoring in the early identification of a superiorly (anterior and superior (AS)) displaced facial nerve. This prospective study included 24 patients operated for removal of large vestibular schwannomas (VS). The latencies of the electromyographic (EMG) events recorded from the trigeminal and facial nerve innervated muscles after mapping the superior surface of the tumor were analyzed. The mean latency of the recorded compound muscle action potential (CMAP) from the masseter muscle was 3.6 ± 0.5 ms and of the peripherally transmitted responses by volume conduction from the frontalis, o. oculi, nasalis, o. oris, and mentalis muscles was 4.6 ± 0.9, 4.1 ± 0.7, 3.9 ± 0.4, 4.3 ± 0.8, and 4.5 ± 0.6 ms, respectively, after trigeminal nerve stimulation in 24 (100%) patients (pattern I response). In 6 (25%) patients, the mean latency of CMAP on the masseter was 3.3 ± 0.3 ms, and the latencies of the CMAP from the frontalis, o. oculi, nasalis, o. oris, and mentalis muscles were 6.5 ± 1.3, 5.0 ± 1.5, 7.5 ± 1.3, 7.4 ± 0.6, and 7.0 ± 1.5 ms, respectively, longer than those of the peripherally transmitted responses (p = 0.002, p = 0.001, p < 0.001, and p = 0.015, respectively) indicating simultaneous stimulation of both nerves (pattern II response). All patients with this response were later confirmed to have an AS-displaced facial nerve. Recognizing the response resulting from simultaneous stimulation of both the facial and trigeminal nerves is important to help early identification of an AS-displaced facial nerve before it is visible in the surgical field and to avoid misleading information by confusing this pattern for a pure trigeminal nerve response.

Intraoperative facial nerve electromyography parameters to optimize postoperative facial nerve outcome in patients with large unilateral vestibular schwannoma

BACKGROUND

Decision-making for large sporadic vestibular schwannomas (VS) resection guided by the intraoperative change in supramaximal facial nerve (FN) amplitude and latency response to optimize post-operative FN outcome.

METHODS

Prospectively study of 43 patients, from January to December 2018, of large sporadic VS with preoperative normal FN function at our center. Tumors were removed through retrosigmoid (81%) or translabyrinthine (19%) approaches with FN monitoring. Intraoperative pre- and post-VS resection supramaximal (2 mA) amplitude and latency responses at the proximal FN root were recorded.

RESULTS

Total, near-/subtotal VS resections (TR, NTR, STR) were achieved in 51%, 38%, and 11% of tumors, respectively, guided by no more than 40% decrease in supramaximal amplitude. Pre- and post-resection supramaximal amplitude and latency responses were lower and longer, respectively, in NTR+STR than in TR. At day 8, FN function was grade I-II in 77% of patients and grade III-V in 23%, and after 6 months, it was in grade I-II in 95% and grade III in 5%, and there was no significant difference between TR and NTR+STR. Facial palsy occurred in older patients and in the case of severe FN adhesion. At day 8, pre- and post-resection supramaximal amplitude but not latency responses were different between FN grade III-V and grade I-II. Serviceable hearing was preserved in 28% of large VS.

CONCLUSIONS

Intraoperative FN monitoring guided VS resection in large VS so that 49% retained some residual tumor. Accordingly, 95% good postoperative FN function and significant hearing preservation were achieved after 6 months.

Hearing recovery after surgical resection of non-vestibular schwannoma cerebellopontine angle tumors

PURPOSE

Post-operative outcomes for hearing after resection surgery to remove cerebellopontine angle (CPA) tumors other than vestibular schwannomas (VS) are not well understood. This study presents a series of patients with significant post-operative hearing recovery, trying to define the incidence among all patients operated on for removal of non-VS CPA tumors.

METHODS

This is a retrospective observational case series of 8 patients among 69 operated on for removal of non-VS CPA tumors between 2012 and 2020. All patients had pre- and post-operative hearing measurement with pure-tone average (PTA) and speech discrimination score (SDS), according to the American Academy of Otolaryngology-Head and Neck Surgery recommendations, auditory brainstem response (ABR) measurements and imaging.

RESULTS

Six meningiomas and two lower cranial nerve schwannomas operated on with a retrosigmoid approach were included for analysis. The mean pre-operative PTA and SDS were 58 ± 20.7 dB and 13 ± 17.5%, respectively. All patients had pre-operative class D hearing and asynchronous ABRs. They all showed significant hearing recovery, with an improvement of 36 ± 22.2 dB (p = 0.0025) and 85 ± 16.9% (p = 0.0001) in PTA and SDS, respectively, with mean follow-up of 21 ± 23.5 months. Seven patients recovered to a class A hearing level and one patient to class B. The ABRs became synchronous for three patients. The incidence of auditory recovery was 13% for patients operated on with a conservative approach (n = 60).

CONCLUSION

A significant post-operative improvement in hearing could be a reasonable expectation in non-VS tumors extending into the CPA and a retrosigmoid approach should always be considered regardless of pre-operative hearing status.

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.

Facial Nerve Length Influence on Vestibular Schwannoma Microsurgery Outcomes

OBJECTIVE

Facial nerve (FN) function preservation is the primary goal during vestibular schwannoma (VS) resection. Many factors are linked to postoperative FN outcomes. In the present study, we evaluated the association between FN length and VS surgical outcomes.

METHODS

We included 70 consecutive patients who had undergone VS microsurgery between October 2019 and November 2020. The clinical data were prospectively obtained from the patients. The relative FN (rFN) length was obtained by subtracting the contralateral FN length from the ipsilateral FN length as measured using DSI Studio software (available at: http://dsi-studio.labsolver.org/).

RESULTS

The postoperative FN function was House-Brackmann grade I in 47 of the 70 patients (67.1%), grade II in 10 (14.3%), and grade III in 13 (18.6%). Gross total resection (GTR) was performed in 61 patients (87.1%). A residual tumor was retained to preserve FN function in 9 of the 70 patients (12.9%), and rFN length was measured (mean diameter, 20.8 mm; range, 2.5-51.5]). On multivariate analysis, the rFN length was significantly associated with the extent of tumor resection. The receiver operating characteristic curve indicated that the cutoff value for rFN length to predict for intraoperative near total resection versus GTR was 36.6 mm, with a specificity and sensitivity of 93.4% and 88.9%, respectively.

CONCLUSIONS

The rFN length is important for predicting surgical outcomes. An rFN length >36.6 mm might indicate difficulty in achieving GTR with preservation of FN function. Therefore, the rFN length could become an objective indicator for neurosurgeons to predict the difficulty of GTR to preserve FN function.

Prognostic Factors for the Outcome of Translabyrinthine Surgery for Vestibular Schwannomas

OBJECTIVE

To identify predictors of tumor recurrence and postoperative facial nerve function after translabyrinthine surgery for unilateral vestibular schwannomas.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

Between 1996 and 2017 a total of 596 patients with unilateral vestibular schwannoma underwent translabyrinthine surgery. Pre- and postoperative clinical status, radiological, and surgical findings were evaluated.

INTERVENTIONS

Translabyrinthine surgery.

MAIN OUTCOME MEASURES

Potential predictors for tumor recurrence and facial nerve outcome were analyzed using Cox regression and ordinal logistic regression, respectively.

RESULTS

The extent of tumor removal was total in 32%, near-total in 58%, and subtotal in 10%. In 5.5% (33/596) of patients the tumor recurred. Subtotal tumor resection (p = 0.004, hazard ratios [HR] = 10.66), a young age (p = 0.008, HR = 0.96), and tumor progression preoperatively (p = 0.042, HR = 2.32) significantly increased the risk of recurrence, whereas tumor size or histologic composition did not. A good postoperative facial nerve function (House-Brackmann grade 1-2) was achieved in 85%. The risk of postoperative facial nerve paresis or paralysis increased with tumor size (p < 0.001, OR = 1.52), but was not associated with the extent of tumor removal, histologic composition, or patient demographics.

CONCLUSIONS

Translabyrinthine surgery is an effective treatment for vestibular schwannoma, with a good local control rate and facial nerve outcome. The extent of tumor removal is a clinically relevant predictor for tumor recurrence, as are young patient age and preoperative tumor progression. A large preoperative tumor size is associated with a higher risk of postoperative facial nerve paresis or paralysis.

Clinical Predictors of Facial Nerve Outcomes After Surgical Resection of Vestibular Schwannoma

OBJECTIVE

To identify clinical predictors of facial nerve (FN) outcomes after microsurgical resection of vestibular schwannoma (VS).

STUDY DESIGN

Prospective cohort study.

SETTING

Academic medical center.

METHODS

Consecutive patients undergoing VS resection from November 2017 to October 2019 were included. FN function was evaluated with the House-Brackmann (HB) scale and stratified into good (HB I-II) and poor (HB III-VI) function. Analyses included descriptive statistics, correlation, and logistic regression.

RESULTS

Of 256 patients who met criteria (mean age, 47.7 years; 62.5% female), 227 (88.7%) achieved good FN function postoperatively and 238 (93.0%) at latest follow-up (mean, 154.8 days). Operative approaches consisted of translabyrinthine (50.8%), retrosigmoid (25.0%), and middle fossa craniotomies (24.2%). Extent of resection was decided intraoperatively, and gross or near total resection was accomplished in 237 (92.6%) cases. Postoperative HB grade correlated with latest HB grade (0.615, P < .001). Factors associated with good postoperative FN function included small tumor size (≤15 mm; odds ratio [OR], 2.425; P = .042), gross or near total resection (OR, 3.170; P = .041), and ≥100-µV intraoperative FN electromyographic response to a 0.05-mA stimulus (OR, 22.242; P < .001). Factors associated with good FN function at latest follow-up included gross total resection (OR, 7.764; P = .003) and ≥100-µV FN electromyographic response (OR, 8.518; P < .001), accounting for surgical approach and tumor size.

CONCLUSION

Microsurgical resection of VS can be accomplished with excellent FN outcomes. Gross total resection and ≥100-µV intraoperative FN electromyographic response predicted excellent FN outcomes. Immediate postoperative FN function is a prognosticator of long-term FN function.

"Large and giant vestibular schwannomas: overall outcomes and the factors influencing facial nerve function"

(1) To study the overall outcomes of patients surgically treated for large/giant vestibular schwannomas (VSs) and (2) to identify and analyze preoperative and intraoperative prognostic factors influencing facial nerve (FN) outcome. A retrospective clinical study was conducted at a quaternary referral otology and skull-base center. A total of 389 cases were enrolled. The inclusion criteria were patients with tumor > 30 mm undergoing surgery with a minimum follow-up of 12 months. Neurofibromatosis-II, previous radiotherapy, revision surgeries, preoperative FN House-Brackmann (HB) grade > I, partial resections, incomplete records, or those lost to follow-up for a minimum period of 1 year were excluded. In addition, partial resections and cases where FN was sacrificed intraoperatively were also excluded and were analyzed separately. The mean duration of symptoms was 35.4 months, pronounced more in elderly (58.3 months) than in younger individuals (28.4 months). Mean tumor diameter was 36 mm and 52.7% was cystic. Total resection (TR), near total resection (NTR), and subtotal resections (STR) were achieved in 77.4%, 9.5%, and 13.2% of cases, respectively. Regrowth was observed only after STR (19.6%). Good (HB I-II), moderate (HB III), and poor (HB IV-VI) FN functions were observed in 36.8%, 51.7%, and 11.6% cases, respectively. Younger individuals underwent TR in 259 (86.9%) cases against 42 (46.2%) in elderly individuals. Non-total resections (NTR/STR) were performed in 49 (53.8%) cases in elderly as against 39(13.1%) in younger individuals. Good FN outcome was observed in 28 (57.1%) cases of non-total resections in elderly as against 13 (33.3%) cases in younger individuals. On multiple logistic regression analysis, size of the tumor, preoperatively prolonged duration of symptoms, profound deafness, and antero-superiorly located FN with respect to the tumor played a detrimental role in the final facial nerve outcome postoperatively. On the contrary, in large tumors (3-3.9 cm), presence of vertigo/disequilibrium had a relatively better impact on final FN outcome. Partial resections accounted for 41(7.8%) cases and FN was interrupted in 71(13.6%) cases in total. Factors detrimental to better FN outcome were giant VSs (> 4 cm), antero-superiorly located FN intratumorally, preoperatively prolonged duration of symptoms, and profound deafness. In large tumors (3-3.9 cm), presence of vertigo/disequilibrium had a better impact on FN outcome. Understandably, cases with TR in comparison with NTR/STR had worse FN outcomes. In comparison with younger patients, elderly patients underwent higher NTR/STR resulting in better FN outcomes. The above factors can be used as prognosticators for patient counseling and surgical decision making.

Improving facial nerve outcome and hearing preservation by different degrees of vestibular schwannoma resection guided by intraoperative facial nerve electromyography

BACKGROUND

Facial nerve (FN) outcome has been improved by deciding upon the degree of vestibular schwannoma (VS) resection guided by intraoperative facial nerve monitoring (IOFM). This study aimed to evaluate hearing and FN outcomes following IOFM-guided VS removal through a retrosigmoid approach (RS).

METHODS

Between January 2015 and August 2017, 77 patients undergoing VS resection through RS, regardless of their preoperative hearing or tumor size, were included in this monocentric retrospective study. Total or near-/subtotal resection was decided intraoperatively according to IOFM. Partial resection was planned preoperatively. Pre- and postoperative FN function (House-Brackmann) and hearing level (AAO-HNS and Gardner-Robertson (GR) scales) were reported. Predictive factors for hearing preservation were analyzed according to a score developed to take into account pre-/postoperative hearing evolution.

RESULTS

The mean extrameatal diameter was 17 ± 8.5 mm. VS resection was total, near-/subtotal, and partial in 71%, 21%, and 8% of cases, respectively. Postoperative grade I and II FN function was achieved in 91% of patients. Serviceable (A+B or GR I+II) hearing and hearing with intelligibility (A+B+C or GR I-III) were preserved in 30% and 43% of cases, respectively. In multivariate analysis, preoperative synchronized auditory brainstem responses (ABR) were the only predictive factor (p = 0.006) imparting a five times greater chance of hearing preservation.

CONCLUSION

IOFM-guided VS excision through RS, whatever the VS size and hearing level, achieved a high rate of good postoperative FN function together with significant hearing preservation, and it should be used if hearing with some intelligibility is still present preoperatively, even in large VS.

Internal Auditory Canal Variability: Anatomic Variation Affects Cisternal Facial Nerve Visualization

BACKGROUND

The internal auditory canal (IAC) is an important landmark during surgery for lesions of the cerebellopontine angle. There is significant variability in the position and orientation of the IAC radiographically, and the authors have noted differences in surgical exposure depending on the individual anatomy of the IAC.

OBJECTIVE

To test the hypothesis that IAC position and orientation affects the surgical exposure of the IAC and facial nerve, especially when performing the translabyrinthine approach.

METHODS

The authors retrospectively reviewed magnetic resonance imaging studies of 50 randomly selected patients with pathologically confirmed vestibular schwannomas. Measurements, including the anterior (APD) and posterior (PPD) petrous distances, the anterior (APA) and posterior (PPA) petro-auditory angles, and the internal auditory angle (IAA), were obtained to quantify the position and orientation of the IAC within the petrous temporal bone.

RESULTS

The results quantitatively demonstrate tremendous variability of the position and orientation of the IAC in the petrous temporal bone. The measurement ranges were APD 10.2 to 26.1 mm, PPD 15.1 to 37.2 mm, APA 104 to 157°, PPA 30 to 96°, and IAA –5 to 40°.

CONCLUSION

IAC variability can have a substantial effect on the surgical exposure of the IAC and facial and vestibulocochlear nerves. Specifically, a horizontally oriented IAC with a small IAA may have significant impact on visualization of the facial nerve within its cisternal segment with the translabyrinthine approach. The retrosigmoid approach is less affected with IAC variability in position and angle.

Prognostic factors of facial nerve function after vestibular schwannoma removal via translabyrinthine approach

BACKGROUND

Prediction of facial function is a major concern when proposing surgery for patients with vestibular schwannoma (VS).

AIMS/OBJECTIVES

To evaluate postoperative facial function of patients who underwent operation of VS via a translabyrinthine approach (TL), and to analyze factors that influence facial functions.

MATERIAL AND METHODS

A total of 91 VS patients, who were operated via a TL approach, between March 1997 and December 2016, were analyzed. Demographics, tumor-related factors, and operative findings were collected. Facial function was assessed according to the House-Brackmann (HB) grading system before surgery, immediately after surgery, and 1-, 3-, 6-months, and 1 year after surgery.

RESULTS

In cases of patients that had a tumor that extended to the CPA, an unsatisfactory facial outcome was noted in 12 (30.0%) patients. FN outcomes after tumor removal depend on tumor size (p = .040). Among FN-related factors, only the FN recovery timing was correlated with facial outcomes (p = .030). Univariable and multivariable analysis revealed that tumor size and the timing of FN recovery were significant as favorable prognostic factors for good facial outcomes.

CONCLUSIONS AND SIGNIFICANCE

Tumor size and the FN recovery timing are significant prognostic factors of facial outcome in VS patients who underwent operations via a TL approach.

[Facial nerve injury in neurosurgery: a rehabilitation potential of botulinum therapy]

Surgical treatment of posterior cranial fossa and cerebellopontine angle tumors is associated with a risk of facial nerve dysfunction. The causes for facial muscle paresis include nerve compression by the tumor, destruction of the nerve structure by the tumor growing from nerve fibers, nerve injury during surgical removal of the tumor, etc. The first 3 months after facial nerve injury are a potential therapeutic window for the use of botulinum toxin type A (BTA). During this period, the drug is introduced both in the healthy side to improve the facial symmetry at rest and during mimetic movements and in the affected side to induce drug-induced ptosis. Post-paralytic syndrome develops 4-6 months after facial nerve injury. At this stage, administration of BTA is also an effective procedure; in this case, drug injections are performed on the affected side at small doses and symmetrically on the healthy side at doses doubling those for the affected side. BTA injections are mandatory in complex treatment of facial muscle paralysis.

Evaluation of the prognostic value of multimodal intraoperative monitoring in posterior fossa surgery patients with cerebellopontine angle tumors

The aim of this study was to compare the outcomes of four intraoperative monitoring approaches in order to compare their prognostic value in surgical complications of the facial nerve. This quasi-experimental study was conducted on 25 patients with Cerebellopontine Angle (CPA) tumors, who were hospitalized in the Valiasr Hospital, affiliated to the Arak University of Medical Sciences, Arak, Iran. The degree of the facial nerve paralysis was assessed based on the House-Brackmann (HB) facial nerve grading system. The Orbicularis oris and Oculi muscles were evaluated by electromyography (EMG) before and after the surgery. Monitoring the facial nerve was performed by the EMG, Facial Nerve Antidromic Potentials (FNAPs), Transcranial Electrical Stimulation (TES), and Brainstem Auditory Evoked Potentials (BAEPs) methods. The mean HB score was 0.36.6±5.83, indicating that the function of the facial muscle was abnormal in all the patients pre-surgery. The comparison of the four monitoring approaches six months after surgery showed that the predictive value of facial nerve TES was higher than the other approaches (P<0.005). Furthemroe, 4% of the patients showed normal function in the facial muscle after the surgery. In addition, 8%, 56%, and 32% of the patients had mild abnormalities, moderate to severe paralysis in the facial muscles, and severe facial nerve dysfunction, respectively. In summary, 36% of the patients showed a mild abnormalities in the follow-up period, and full recovery was observed in 28% of the cases. In conclusion, the transcranial motor evoked potential (TCMEP) is a useful method for monitoring the facial nerve during the surgery along with the continuous EMG recordings.

Surgical treatment of sporadic vestibular schwannoma in a series of 1006 patients

The management of sporadic vestibular schwannoma (VS) has evolved in the last decades. The aim of this study was to analyse the evolution in surgical outcomes of VSs operated by a neurotological team between 1990 and 2006 by different approaches. A monocentric retrospective review of medical charts of 1006 patients was performed. In order to assess eventual changes and progress, the 17-years period was divided in three periods, each one comprehending 268 VS (1990-1996), 299 VS (1997-2001), and 439 VS (2002-2006). Mean follow-up was 5.9 ± 2.4 years. Overall, complete VS removal was achieved in 99.4% of cases. Mortality rate was 0.3%, meningitis and CSF leaks were observed in 1.2 % and 9 % of the cases, respectively. CSF leakage decreased from 11.6% to 7.1% between the first and last period (p < 0.01) as well as revision surgery from 3.4 % to 0.9 % (p < 0.05). Facial nerve was anatomically preserved in 97.7% of cases. At one year, a good facial nerve function was observed in 85.1% of patients (grade I and II of House-Brackmann grading scale), which ranged between the first and last period from 78.4% to 87.6% (p <0.05). At one year, hearing preservation was obtained in 61.6% of patients, which increased from the first period to the last one from 50.9% to 69.0% (p < 0.05) (class A+B+C from the AAO-HNS classification). Useful hearing (class A+B) was observed in 33.5% of cases overall, with 21.8% and 42% in the first and last period, respectively (p < 0.01). Surgical outcomes of sporadic vestibular schwannoma have improved concerning facial nerve function outcomes, hearing preservation and cerebrospinal fluid (CSF) leaks, mainly due to the neuro-otological team's experience. Functional results after complete microsurgical removal of large VS depend on experience gained on small VS removal.

Role of electrophysiology in guiding near-total resection for preservation of facial nerve function in the surgical treatment of large vestibular schwannomas

OBJECTIVE In large vestibular schwannoma (VS) surgery, the facial nerve (FN) is at high risk of injury. Near-total resection has been advocated in the case of difficult facial nerve dissection, but the amount of residual tumor that should be left and when dissection should be stopped remain controversial factors. The objective of this study was to report FN outcome and radiological results in patients undergoing near-total VS resection guided by electromyographic supramaximal stimulation of the FN at the brainstem. METHODS This study was a retrospective analysis of a prospectively maintained database. Inclusion criteria were surgical treatment of a large VS during 2014, normal preoperative FN function, and an incomplete resection due to the strong adherence of the tumor to the FN and the loss of around 50% of the response of supramaximal stimulation of the proximal FN at 2 mA. Facial nerve function and the amount and evolution of the residual tumor were evaluated by clinical examination and by MRI at a mean of 5 days postoperatively and at 1 year postoperatively. RESULTS Twenty-five patients met the inclusion criteria and were included in the study. Good FN function (Grade I or II) was observed in 16 (64%) and 21 (84%) of the 25 patients at Day 8 and at 1 year postoperatively, respectively. At the 1-year follow-up evaluation (n = 23), 15 patients (65%) did not show growth of the residual tumor, 6 patients (26%) had regression of the residual tumor, and only 2 patients (9%) presented with tumor progression. CONCLUSIONS Near-total resection guided by electrophysiology represents a safe option in cases of difficult dissection of the facial nerve from the tumor. This seems to offer a good compromise between the goals of preserving facial nerve function and achieving maximum safe resection.

Multivariate Analysis of Factors Influencing Facial Nerve Outcome following Microsurgical Resection of Vestibular Schwannoma

Objective To assess through multivariate analysis the clinical pre- and intraoperative factors of facial nerve outcomes at day 8 and 1-year recovery of facial palsy, as compared with day 8 status among patients who underwent total resection of unilateral vestibular schwannoma. Study Design Case series with chart review. Setting Tertiary referral center. Subjects and Methods This study included 229 patients with preoperative normal facial function and anatomic preservation of the facial nerve. Clinical, radiologic, and intraoperative factors were assessed according to facial nerve function at day 8 and 1 year. Results We observed that 74% and 84% of patients had good facial function (House-Brackmann [HB] I-II) at day 8 and 1 year, respectively. Of 60 patients, 26 (43%) who had impaired facial function (HB III-VI) at day 8 recovered good facial function (HB I-II) 1 year after surgery. A structured equation model showed that advanced tumor stage and strong facial nerve adhesion were independently associated with facial nerve conduction block at day 8. No predictive factor of impaired facial function recovery was seen at 1 year. In terms of the extracanalicular diameter of the tumor, the cutoff point to minimize the risk of impaired facial function was 16 mm. Conclusion At day 8 after vestibular schwannoma resection, facial function was impaired in the case of large tumors or strong facial nerve adhesion to the tumor. After 1 year, less than half of the patients recovered good facial function, and no predictive factor was found to be associated with this possible recovery.

Surgery for sporadic vestibular schwannoma. Part IV. Predictive factors influencing facial nerve function after surgery

OBJECTIVE

To analyze the impact of various clinical, radiological and perioperative factors that could influence the facial nerve intraoperative disruption risk (CNVII-IDR) and its long-term function (CNVII-LTF) after vestibular schwannoma (VS) surgery.

MATERIAL AND METHODS

The study included 212 patients operated on for sporadic VS with no history of previous treatment for VS or CNVII palsy. The mean size of the tumor was 30 mm. Gross (210) or near-total (2) resections were carried out using the retrosigmoid (210) or translabyrinthine (2) approach. Correlation studies and multivariate regression analysis (RA) were performed.

RESULTS

In correlation studies, the CNVII-IDR was increased by: headaches and cerebellar ataxia if one of them was the first symptom of the tumor (33% and 29%, respectively, p=0.008); preoperative hydrocephalus (40% vs. 9%, p=0.01), tumor size >3 cm (18% vs. 5%, p<0.01), tumor volume >10 cm(3) (19% vs. 4%, p<0.01), right-sided location 15% vs. 6%, p=0.047), lateral "park-bench" position (19% vs. 5% for supine position, p<0.01) and the procedure order (16% for the first 106 procedures vs. 6% for the last 106 procedures, p<0.05). In RA the tumor volume (p=0.012), side of the tumor (p=0.028) and patient's position during surgery (p=0.016) independently affected the CNVII-IDR. The following factors correlated significantly with satisfactory CNVII-LTF (HB grades I-III): tumor stage <T4 (p=0.000), tumor size ≤3 cm (p=0.000), tumor volume ≤10 cm(3) (p=0.001), and left-sided location (p=0.048). Additional factors correlated significantly with very good CNVII-LTF (HB grades I-II): anterior CNVII displacement (p=0.044), nimodipine use (p=0.016), the absence of postoperative complications (p=0.019), CNVII responsive on final intraoperative EMG stimulation (p=0.000) and supine position during surgery (p=0.018). However, an independent impact on very good CNVII-LTF proved to be the tumor size (p=0.0000), side (p=0.0175), and nimodipine use (p=0.0349).

CONCLUSIONS

In our series, the factors related to size and side of the tumor confirmed an independent impact on CNVII-IDR and CNVIILTF. The significance of patient positioning may reflect the impact of learning curve as only the first 91 patients were operated on using the lateral "park-bench" position. An independent impact on CNVII-LTF was exerted by the perioperative use of nimodipine.

Improved preservation of function during acoustic neuroma surgery

OBJECT

Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery.

METHODS

Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone-elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed.

RESULTS

A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade.

CONCLUSIONS

Preservation of function was significantly better for patients who received extended recuperation treatment.

Ptosis as partial oculomotor nerve palsy due to compression by infundibular dilatation of posterior communicating artery, visualized with three-dimensional computer graphics: case report

Oculomotor nerve palsy (ONP) due to internal carotid-posterior communicating artery (PcomA) aneurysm generally manifests as partial nerve palsy including pupillary dysfunction. In contrast, infundibular dilatation (ID) of the PcomA has no pathogenic significance, and mechanical compression of the cranial nerve is extremely rare. We describe a 60-year-old woman who presented with progressive ptosis due to mechanical compression of the oculomotor nerve by an ID of the PcomA. Three-dimensional computer graphics (3DCG) accurately visualized the mechanical compression by the ID, and her ptosis was improved after clipping of the ID. ID of the PcomA may cause ONP by mechanical compression and is treatable surgically. 3DCG are effective for the diagnosis and preoperative simulation.

Intraoperative Transcranial Motor-Evoked Potential Monitoring of the Facial Nerve during Cerebellopontine Angle Tumor Resection

Objective To determine whether transcranial motor-evoked potential (TCMEP) monitoring of the facial nerve (FN) during cerebellopontine angle (CPA) tumor resection can predict both immediate and long-term postoperative FN function. Design Retrospective review. Setting Tertiary referral center. Main Outcome Measures DeltaTCMEP (final-initial) and immediate and long-term facial nerve function using House Brackmann (HB) rating scale. Results Intraoperative TCMEP data and immediate and follow-up FN outcome are reported for 52 patients undergoing CPA tumor resection. Patients with unsatisfactory facial outcome (HB >2) at follow-up had an average deltaTCMEP of 57 V, whereas those with HB I or II had a mean deltaTCMEP of 0.04 V (t = -2.6, p < 0.05.) Intraoperative deltaTCMEP did not differ significantly between groups with satisfactory (HB I, II) and unsatisfactory (HB > 2) facial function in the immediate postoperative period. Conclusion Intraoperative TCMEP of the facial nerve can be a valuable adjunct to conventional facial nerve electromyography during resection of tumors at the CPA. Intraoperative deltaTCMEP >57 V may be worrisome for long-term recovery of satisfactory facial nerve function.

Predictive factors influencing facial nerve outcomes in surgery for small-sized vestibular schwannoma

CONCLUSION

The most important predictive factor of facial nerve outcome in surgery for small-sized vestibular schwannoma (VS) is the adhesion between the tumor and the facial nerve.

OBJECTIVES

To compare the facial nerve outcomes between middle cranial fossa (MCF) and translabyrinthine (TL) approaches, and to analyze the preoperative and intraoperative factors influencing facial nerve outcome after small VS surgery in our neurotologic department.

METHODS

A total of 29 patients were retrospectively analyzed, with 16 in the MCF group and 13 in the TL group. Facial function was serially evaluated according to the House-Brackmann classification at 7 days, 1 month, 3 months, 6 months, and 1 year postoperatively. The effects of variables such as the surgical approach, tumor size, nerve origin, extrameatal extension, intraoperative tumor adhesion to the facial nerve, and facial nerve displacement were determined.

RESULTS

Early and late facial nerve outcomes showed no significant correlation with surgical approach, tumor origin, tumor size, extrameatal extension, or facial nerve displacement pattern. However, a significant correlation was observed with tumor adhesion to the facial nerve and facial nerve outcomes.

Neuroanatomical correlation of the House-Brackmann grading system in the microsurgical treatment of vestibular schwannoma

Avoidance of facial nerve injury is one of the major goals of vestibular schwannoma (VS) surgery because functional deficits of the facial nerve can lead to physical, cosmetic, and psychological consequences for patients. Clinically, facial nerve function is assessed using the House-Brackmann grading scale, which also allows physicians to track the progress of a patient's facial nerve recovery. Because the facial nerve is a peripheral nerve, it has the ability to regenerate, and the extent of its functional recovery depends largely on the location and nature of its injury. In this report, the authors first describe the facial nerve anatomy, the House-Brackmann grading system, and factors known to be predictors of postoperative facial nerve outcome. The mechanisms and pathophysiology of facial nerve injury during VS surgery are then discussed, as well as factors affecting facial nerve regeneration after surgery.

Cyclin D1 expression and facial function outcome after vestibular schwannoma surgery

HYPOTHESIS

The proto-oncogen cyclin D1 has been implicated in the development and behavior of vestibular schwannoma. This study evaluates the association between cyclin D1 expression and other known prognostic factors in facial function outcome 1 year after vestibular schwannoma surgery.

METHODS

Sixty-four patients undergoing surgery for vestibular schwannoma were studied. Immunohistochemistry analysis was performed with anticyclin D1 in all cases. Cyclin D1 expression, as well as other demographic, clinical, radiologic, and intraoperative data, was correlated with 1-year postoperative facial function.

RESULTS

Good 1-year facial function (Grades 1-2) was achieved in 73% of cases. Cyclin D1 expression was found in 67% of the tumors. Positive cyclin D1 staining was more frequent in patients with Grades 1 to 2 (75%) than in those with Grades 3 to 6 (25%). Other significant variables were tumor volume and facial nerve stimulation after tumor resection. The area under the receiver operating characteristics curve increased when adding cyclin D1 expression to the multivariate model.

CONCLUSION

Cyclin D1 expression is associated to facial outcome after vestibular schwannoma surgery. The prognostic value of cyclin D1 expression is independent of tumor size and facial nerve stimulation at the end of surgery.