Facial Nerve Preserving Subtotal Excision for Large Vestibular Schwannoma: An Institution-Based Functional Outcome Study.

BACKGROUND: The ideal goal of treatment for medium to large vestibular schwannoma is complete tumor removal with preservation of all cranial nerves. However, despite the advancements in microsurgery and intraoperative monitoring, the risk of facial nerve dysfunction following total resection varies between 31% and 57%. Currently, the goal of treatment for large tumors is shifting from total excision to facial nerve preservation. OBJECTIVE: To evaluate the facial nerve outcome in patients who underwent subtotal excision with or without subsequent gamma knife radiosurgery for large vestibular schwannomas in our institute. METHODS AND MATERIAL: All patients who underwent primary surgery for large vestibular schwannomas between January 2012 and December 2016 were analyzed retrospectively. Cases where total excision was not done and a residue was left behind to prevent facial nerve injury during surgery were included in the study. RESULTS: A total of 52 patients who met the inclusion criteria were analyzed. At final follow-up, 70% of patients had good facial nerve function (H-B grade 1 and 2). In patients with normal facial nerve function preoperatively, 81% (25/31) of them had good facial nerve outcomes (H-B grade 1 and 2), whereas in patients with preexisting facial nerve deficits, nearly 62% (13/21) of them either maintained or had improvement in their facial nerve grades. CONCLUSION: Good facial nerve outcomes and tumor control rate is obtained by subtotal excision of VS followed by upfront or delayed GKRS; however, there is a need for long-term follow-up to detect recurrences in these slow-growing tumors.

Navigating the void: outcomes and adaptations during parotid surgery in the absence of posterior belly of digastric muscle.

It is well known that the digastric posterior belly is one of the essential landmarks for facial nerve identification during parotid surgery. While there were multiple reports about variations of the digastric anterior belly, only a few anatomical variations of the posterior belly of the digastric muscle have been described.In this article, we describe an anatomical variation of the posterior belly of digastric muscle found during superficial parotidectomy of a patient with pleomorphic adenoma. This anatomical variation also led to an anatomical variation in the position of the facial nerve.To our knowledge, this is the first report of an absent posterior belly of digastric muscle found during live parotid surgery. The knowledge of current anatomical variation may help to avoid facial nerve injury during parotid surgery and preserve the function of muscles of facial expression.

Modified Endaural Approach With a Peripheral Dissection of the Superficial Musculoaponeurotic System to Access the Temporomandibular Joint to Prevent Facial Nerve Injury.

The purpose of this study was to assess the effects of protecting the facial nerve with a modified endaural approach with a peripheral dissection of the superficial musculoaponeurotic system to access the temporomandibular joint which allows an excellent operative field of visualization, multiple surgical procedures of the temporomandibular joint, and general care which improves the immediate postoperative period, making this a less morbid surgery. This study included 33 patients (39 sides) who underwent surgical treatment for disorders of the temporomandibular joint from the years 2021 to 2023 at the maxillofacial department of the clinic "Colsanitas" located in Bogota, Colombia. Therapeutic results were evaluated by postoperative facial nerve injury, with the House-Brackman scale; every patient was examined for adequate facial musculature function immediately after surgery. Notably, zero patients presented facial nerve injury. These results imply that the modified endaural approach with a peripheral dissection of the superficial musculoaponeurotic system to access the temporomandibular joint reduces the incidence of facial nerve injuries, improves operative site exposure, and lowers the frequency of complications.

[A sampling survey of intraoperative facial nerve monitoring in China].

Objective: This study aims to investigate the current application and the level of knowledge of intraoperative facial nerve monitoring among medical staff in China. Methods: A comprehensive online questionnaire was conducted among medical professionals across different regions in China from October 2022 to February 2023. The survey exclusively targeted departments specializing in otolaryngology, head and neck surgery, neurosurgery, and oral and maxillofacial surgery. The questionnaire covered various aspects including general information, intraoperative facial nerve monitoring practices, training history, indications for monitoring, parameters used during monitoring procedures, as well as factors influencing its implementation. Results: A total of 417 participants from 31 provincial, municipal, and autonomous regions were included. Intraoperative facial nerve monitoring was found to be implemented in 227 (54.4%,227/417) repondents of 53 institutions (24.9%, 53/213). The top three indications for implementing this technique were acoustic neuroma, parotid gland surgery, and modified middle ear surgery (mastoidectomy). Herein 81.1%(184/227) medical staff involved in intraoperative facial nerve monitoring had received relevant training, 57.3%(130/227)-92.1%(209/227) reported a lack of clear description regarding recording thresholds, stimulation currents/frequencies/wave widths. Conclusion: The majority of the institutions surveyed have not yet adopted intraoperative facial nerve monitoring. Furthermore, significant gaps concerning the procedure exist. It is imperative to establish standards or guidelines to promote its better development and application.

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.

The "low preauricular" transmasseteric anteroparotid (TMAP) technique as a standard way to treat extracapsular condylar fractures.

Condylar fracture treatment is a debated topic among maxillofacial surgeons. Various surgical techniques are used today, each one with advantages and disadvantages. The aim of this study is to present and evaluate our technique adopted for treatment of any type of extracapsular condylar fractures. Between 2020 and 2022, 16 condylar fractures were treated. In two patients with bilateral condylar fractures, the present technique was compared to the mini-retromandibular approach. All the patients were checked for clinical and radiological outcomes, facial nerve injury, scar visibility and presence of salivary complications. Dental occlusion was always restored, and facial nerve damage or salivary disorders were not observed. The skin incision, limited to the caudal two-thirds of the auricle, made the scar almost invisible and greatly improved the surgical field in the condylar neck area, facilitating the treatment. The proposed technique provides easier internal fixation for both neck and base condylar fractures with good cosmetic results, ensuring better protection of the facial nerve and parotid gland. The surgical technique described has not shown disadvantages in terms of operational difficulty, results, and complications. This novel surgical technique could represent a new choice in the treatment of extracapsular condylar fractures, although further studies are needed to support this new proposal.

Topography of the frontal branch of the facial nerve and its clinical implication for temporal direct browplasty.

Due to anatomic proximity to the surgical site, iatrogenic trauma to the frontal branch of the facial nerve (FbFN) with resultant brow paralysis is a recognized major complication of temporal direct browplasty. This study was aimed to elucidate the course of the FbFN in the area superolateral to the brow in order to facilitate safer temporal direct browplasty by preventing facial nerve injury. Forty-five hemifaces from 32 embalmed Korean cadavers were dissected. A horizontal line connecting the tragion to lateral canthus was established. Then, an oblique line passing through the lateral canthus and 45° to the horizontal line was used as reference line. The mean distance from the lateral canthus to the points where the FbFN cross the reference line was measured. The angle between the FbFN and reference line at the crossing points were also recorded. After crossing the zygomatic arch, FbFN continues in an anteriorly inclining curve across the temporal region, passing near the lateral end of the brow as it heads toward frontalis muscles. During the course, the FbFN laying in the innominate fascial layer was divided into 3 branches. The anterior and posterior branch of FbFN crossed the reference line superiorly and laterally at 3 and 4 cm from the lateral canthus, respectively. In conclusion, the oculofacial surgeon must bring the dissection plane of the forehead tissue more superficially around the 3 cm superolaterally to the lateral canthus in the direction of 45° from the horizontal line in order to avoid nerve injury.

Predicting postoperative facial nerve paralysis by using intraoperative nerve monitoring during parotid surgery.

OBJECTIVES: To investigate a method for predicting postoperative facial nerve paralysis (POFNP) during parotid surgery using intraoperative nerve monitoring (IONM). METHODS: We assessed prediction for POFNP by using IONM, comparing between stimulation in the facial nerve trunk and each branch by using facial nerve monitoring. The amplitude response ratio (ARR) was calculated for the trunk/periphery. In addition, we then examined the correlation between ARR and time to recovery of paralyzed branches. RESULTS: 372 branches of 93 patients did not develop POFNP and were classified as group A. Among 20 patients who developed POFNP, 51 branches without POFNP were classified as group B, and 29 branches with POFNP were classified as group C. The ARR was approximately 1 in group A and B. but less than 0.5 in all branches in Group C. When the cut off value of ARR was set at 0.55, the sensitivity, specificity, and accuracy of POFNP diagnosis by ARR were 96.5%, 93.1%, and 96.8%, respectively. CONCLUSION: Using IONM during parotid surgery enables easy prediction of POFNP.

Feasibility of facial nerve monitoring using adhesive surface electrodes during parotidectomy: a comparative study with needle electrodes.

PURPOSE: Electrophysiological monitoring of the facial nerve during parotidectomy has been reported as an adjunctive method to prevent facial nerve injury. Classically, a needle electrode is used to obtain electromyographic (EMG) signals from facial muscles during facial nerve monitoring (FNM) of parotid surgery, likewise adhesive surface electrodes. This study aimed to investigate the feasibility of performing FNM with surface electrodes during parotid surgery and to compare EMG values with needle electrodes. METHODS: Thirty patients who underwent parotidectomy under FNM using adhesive surface and needle electrodes were included. Two pairs of adhesive surface electrodes and needle electrodes were used for FNM during parotid surgery. Mean amplitudes were collected after electrical facial nerve stimulation at 1 mA after specimen removal. RESULTS: The mean amplitude of the adhesive surface electrodes was 226.50 ± 118.44 µV (orbicularis oculi muscle) and 469.6 ± 306.06 µV (orbicularis oris muscle), respectively. The mean amplitude of the needle electrodes was 449.85 ± 248.10 µV (orbicularis oculi muscle) and 654.66 ± 395.71 µV (orbicularis oris muscle), respectively. The mean amplitude of the orbicularis oris muscle was significantly greater than that of the orbicularis oculi. The amplitude values measured in the orbicularis oculi muscle showed significant differences between the needle and skin electrodes. CONCLUSIONS: Facial nerve monitoring (FNM) using adhesive surface electrodes is feasible in parotid surgery. Although the mean amplitude value of the surface electrode was relatively lower than that of the needle electrode, the surface electrode is considered a feasible and safe EMG recording device for FNM in parotid surgery.

Extratemporal facial nerve branching patterns: systematic review of 1497 cases.

OBJECTIVE: The aim of this systematic review was to analyse the complex anatomy of the extratemporal portion of the facial nerve with an accurate description of the branching patterns based on the Davis classification. METHOD: Medline, ScienceDirect and the Cochrane Library databases as well as other sources were searched by two independent reviewers. RESULTS: Analysis of 21 studies with a total of 1497 cases showed that type III is the most common branching pattern accounting for 26.8 per cent of cases. The type I pattern, previously considered as the normal anatomy in most textbooks, was the fourth most common branching pattern at 16.3 per cent. The majority of specimens (96.4 per cent) were found to have a bifurcated main trunk, and only 3.2 per cent were found with a trifurcated main trunk. CONCLUSION: Surgeons should be aware of anatomical variations in the course of the facial nerve. An early identification of the branching pattern during surgery reduces the risk for iatrogenic facial nerve injury.

Intraoperative Corticobulbar Motor Evoked Potential in Cerebellopontine Angle Surgery: A Clinically Meaningful Tool to Predict Early and Late Facial Nerve Recovery.

BACKGROUND: Intraoperative neuromonitoring is crucial for facial nerve preservation in cerebellopontine angle (CPA) surgery. Among the available techniques, the role of intraoperative corticobulbar facial motor evoked potentials (FMEPs) is unclear. OBJECTIVE: To evaluate the significance of intraoperative FMEPs as indicators for early and late postoperative facial nerve function (FNF) in CPA tumor resection and the feasibility of their integration with standard monitoring techniques. METHODS: An institutional series of 83 patients who underwent surgery under intraoperative monitoring for CPA extra-axial tumor resection was reported. A pair of needle electrodes was used to record FMEP from orbicularis oculi (OOc) and orbicularis oris (OOr) muscles at baseline, at the end of surgery and minimum values recorded. From FMEP amplitudes, minimum-to-baseline amplitude ratio (MBR), final-to-baseline amplitude ratio (FBR), and recovery value, intended as FBR minus MBR, were calculated. These indices were correlated with early and late postoperative FNF. RESULTS: Our analysis demonstrated that higher FBR (both from OOc and OOr) and MBR (from OOr only) were associated with a good early and late FNF; a higher MBR from OOc was significantly associated with a good late FNF. The most accurate index in predicting early FNF was FBR measured from OOr with a cutoff of 35.56%, whereas the most accurate index in predicting late FNF was FBR as measured from OOc with a cutoff of 14.29%. CONCLUSION: Our study confirmed that FMEPs are reliable predictors of early and late postoperative FNF in CPA surgery and could be easily integrated with standard intraoperative neuromonitoring techniques.

Midline Facial Nerve Monitoring: Single-Center Experience and Review of Literature.

BACKGROUND: Facial nerve monitoring system has enabled facial muscle activity detection using electrodes placed over the target muscles. In an effort to enable the best and minimally invasive surgical approach, a midline facial nerve monitor was applied during bilateral cochlear implantation surgical intervention in our center and the feasibility of placing midline facial nerve monitor electrodes during bilateral cochlear implantation operations was evaluated. METHODS: The medical records and operative notes of all patients who underwent bilateral cochlear implantation surgery between January 2017 and April 2018 in a quaternary care center were retrospectively reviewed and divided into 2 groups based on the facial nerve monitoring methods: facial nerve monitoring with the midline (midline facial nerve monitor) or bilateral (bilateral facial nerve monitor) electrode placements. Basic demographic information, comorbidities, and facial nerve status (pre- and postoperatively) were collected from patient electronic medical charts. The operative notes were reviewed for abnormal facial nerve findings, as well as for any reported difficulties with the identification or stimulation of facial nerve. The primary outcome was facial nerve identification postoperative function. RESULTS: Seventy-eight patients met our inclusion criteria. Midline facial nerve monitor was used in 49 patients and bilateral facial nerve monitor was used in 29 patients. No documented difficulty was identified at the step of facial nerve identification in either group, and none of the patients developed facial nerve weakness postoperatively. CONCLUSION: Midline facial nerve monitor is a safe and reliable method that can be used in bilateral cochlear implantation surgeries and other surgeries requiring facial nerve monitoring.

Effect of two fascial incision options for access to the temporomandibular joint on facial nerve function: objective investigation.

This study was performed to compare the effects on facial nerve (FN) function of the deep supra-temporalis muscle subfascial approach (DSFA) and traditional fascial approach (TFA) for access to the temporomandibular joint (TMJ), via qualitative and quantitative evaluations. Thirty patients requiring open TMJ surgery were randomly allocated to one of two groups: group A patients underwent the DSFA approach, while group B patients underwent the TFA approach. The TMJ was accessed via modified endaural incision with temporal extension. Clinical examinations, FN conduction tests, and electromyography (EMG) of the frontalis and orbicularis oculi muscles were used to assess FN function. A FN function deficit was noted in 50% of the whole sample population immediately after surgery, with no statistically significant difference between the groups (P = 0.082). Overall, 37.5% of the total study population experienced temporary loss of frontalis muscle activity, while zygomatic nerve injury was seen only in 25% of group A. Within 2-6 months, normal function returned in both groups. Nerve conduction studies showed no statistically significant difference between the groups in terms of nerve amplitude or latency after surgery. However, EMG of orbicularis oculi activity showed a significant difference between the groups after 6 months (P = 0.010). The results suggest that the traditional dissection approach is more protective of the FN, especially the zygomatic branch, than the deeper dissection technique.

The spiral ladder technique of facial nerve trunk identification during parotidectomy: A convenient roadmap for the beginners.

The intricate relationship between the facial nerve and the parotid gland makes the surgeries involving the gland challenging. Though several landmarks have been described to locate the nerve trunk, variations do exist due to the physical and racial characteristics of an individual. The spiral ladder technique described here uses multiple landmarks that appear in a stepwise manner as a beginner proceeds through the surgery as a road map to the nerve trunk. This simple adoption of a cluster of existing landmarks increases the certainty factor. This method may help beginners and in turn, reduce the chances of iatrogenic facial nerve injuries.

Accuracy and outcomes of diffusion tensor imaging tractography in resection for vestibular schwannoma for facial nerve preservation.

BACKGROUND: Impairment of facial nerve (FN) function is a common postoperative complication in surgical resections of Vestibular Schwannomas (VS). Diffusion tensor imaging (DTI) tractography creates in vivo imaging of the anatomical location of white matter tracts that can be preoperatively used to visualize the displaced FN. We present an analysis of patients who underwent DTI tractography imaging prior to VS resection. METHODS: Patient charts were reviewed from March 2012 to April 2015 who underwent DTI tractography prior to surgical resection for VS. Reliability of this measure was compared to the intraoperative FN location as determined by the surgeon. House Brackmann (HB) score was used to assess facial nerve function. RESULTS: A total of 11 patients were included with a mean age of 43 years (range: 19-64) and mean follow-up length of 11.9 months (range: 3.1-34.2). The average maximum tumor diameter was 2.82 cm (range: 1.7-4.2). DTI tractography was accurate in 90.9% (10/11) of patients. Postoperatively, 72.7% (8/11) had a HB score of I or II, 18.2% (2/11) had a HB score of III, and 9.1% (1/11) had a HB score of IV. CONCLUSIONS: Facial nerve visualization for VS resection can be accurately visualized using DTI tractography. This modality may lead to reduction of postoperative FN damage.

Indications for Facial Nerve Monitoring During Parotidectomy.

Facial nerve injury is the most feared complication during parotid surgery. Intraoperative electromyographic nerve monitoring can be used to identify the facial nerve, map its course, identify surgical maneuvers detrimental to the nerve, and provide prognostic information. Data regarding outcomes with facial nerve monitoring are heterogeneous. In contrast, the incidence of permanent weakness has not been shown to be significantly affected by use of nerve monitoring. For revision surgery, studies show that monitored patients had (1) weakness that was less severe with quicker recovery and (2) shorter operative times compared with unmonitored patients.

Best Practices in Facial Nerve Monitoring.

OBJECTIVES/HYPOTHESIS: Facial nerve monitoring (FNM) has evolved into a widely used adjunct for many surgical procedures along the course of the facial nerve. Even though majority opinion holds that FNM reduces the incidence of iatrogenic nerve injury, there are few if any studies yielding high-level evidence and no practice guidelines on which clinicians can rely. Instead, a review of the literature and medicolegal cases reveals significant variations in methodology, training, and clinical indications. STUDY DESIGN: Literature review and expert opinion. METHODS: Given the lack of standard references to serve as a resource for FNM, we assembled a multidisciplinary group of experts representing more than a century of combined monitoring experience to synthesize the literature and provide a rational basis to improve the quality of patient care during FNM. RESULTS: Over the years, two models of monitoring have become well-established: 1) monitoring by the surgeon using a stand-alone device that provides auditory feedback of facial electromyography directly to the surgeon, and 2) a team, typically consisting of surgeon, technologist, and interpreting neurophysiologist. Regardless of the setting and the number of people involved, the reliability of monitoring depends on the integration of proper technical performance, accurate interpretation of responses, and their timely application to the surgical procedure. We describe critical steps in the technical set-up and provide a basis for context-appropriate interpretation and troubleshooting of recorded signals. CONCLUSIONS: We trust this initial attempt to describe best practices will serve as a basis for improving the quality of patient care while reducing inappropriate variations. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:S1-S42, 2021.