Postoperative Facial Function Research Articles

Tumor biomechanical stiffness by magnetic resonance elastography predicts surgical outcomes and identifies biomarkers in vestibular schwannoma and meningioma

Variations in the biomechanical stiffness of brain tumors can not only influence the difficulty of surgical resection but also impact postoperative outcomes. In a prospective, single-blinded study, we utilize pre-operative magnetic resonance elastography (MRE) to predict the stiffness of intracranial tumors intraoperatively and assess the impact of increased tumor stiffness on clinical outcomes following microsurgical resection of vestibular schwannomas (VS) and meningiomas. MRE measurements significantly correlated with intraoperative tumor stiffness and baseline hearing status of VS patients. Additionally, MRE stiffness was elevated in patients that underwent sub-total tumor resection compared to gross total resection and those with worse postoperative facial nerve function. Furthermore, we identify tumor microenvironment biomarkers of increased stiffness, including αSMA + myogenic fibroblasts, CD163 + macrophages, and HABP (hyaluronic acid binding protein). In a human VS cell line, a dose-dependent upregulation of HAS1-3, enzymes responsible for hyaluronan synthesis, was observed following stimulation with TNFα, a proinflammatory cytokine present in VS. Taken together, MRE is an accurate, non-invasive predictor of tumor stiffness in VS and meningiomas. VS with increased stiffness portends worse preoperative hearing and poorer postoperative outcomes. Moreover, inflammation-mediated hyaluronan deposition may lead to increased stiffness.

A nomogram to predict long-term facial nerve function after vestibular schwannoma resection: a contemporary multi-institutional study

OBJECTIVE The objective of this study was to develop a nomogram to predict long-term facial nerve (FN) function after vestibular schwannoma (VS) resection. METHODS A retrospective cohort study of two tertiary academic skull base referral centers was performed. Consecutive adults > 18 years of age with sporadic unilateral VS who underwent resection between September 2016 and May 2021 were included. FN function in the immediate postoperative period and at the most recent evaluation was measured. RESULTS A total of 306 patients (mean age 49 years, 63% female) were included, with a mean follow-up of 18 months. The mean maximum tumor diameter was 19 mm (range 1–50 mm), and 80 (26.1%) tumors were > 25 mm. Overall, 85% of patients showed good immediate postoperative FN function (House-Brackmann [HB] grade I or II) and 89% maintained good FN function at > 12 months of follow-up. An intraoperative FN electromyographic (EMG) response ≥ 100 µV to 0.05 mA of stimulation (OR 18.6, p < 0.001) was the strongest predictor of good HB grade in the immediate postoperative period. EMG response ≥ 100 µV (OR 5.70, p < 0.001), tumor size ≤ 25 mm (OR 3.09, p < 0.05), and better immediate postoperative HB grade (OR 1.48, p = 0.005) predicted good long-term FN function on multivariable analysis. A point-of-care nomogram based on these data predicted long-term FN function with a sensitivity of 89% and specificity of 69%. CONCLUSIONS Better immediate postoperative HB grade, intraoperative FN EMG response ≥ 100 µV, and tumor size ≤ 25 mm strongly predicted good long-term FN function after VS resection. A point-of-care nomogram based on these variables could serve as a useful tool for postoperative counseling and prognosis of long-term FN recovery.

Electromyographic Study of Facial Nerve Function Using Two Different Surgical Approaches in Low Condylar Fractures of the Mandible: A Randomized Controlled Clinical Trial

Facial nerve (FN) dysfunction is a potential complication during open reduction of mandibular condylar fractures. The purpose of this study was to measure and compare the postoperative FN function following transparotid (TP) and transmasseteric anterior parotid (TMAP) operative approaches in open reduction and internal fixation of condylar fractures using electromyogram. A randomized controlled clinical trial was designed. The study was conducted in a single tertiary-care hospital in the inpatient setting. Patients aged above 18years with unilateral condylar fracture of the jaw or bilateral condylar fractures undergoing surgery on only 1 side were included. Patients were excluded if they had fractures of the head, bilateral condylar fractures with surgery planned on both sides, a previous history of surgery in the retromandibular area, existing lacerations to approach condyle, preoperative signs of FN weakness, or a history of parotid surgery. The predictor variable was the operative approach and the subjects were allocated randomly to TMAP and TP. The primary outcome variable was postoperative FN function in the surgical approach employed using the House-Brackmann scale and electromyography (EMG) to record any subtle weakness in nerve function. The FN function is recorded at 3 time intervals postoperatively 1week (T1), 1month (T2), and 3months (T3). The secondary outcomes studied were operating time and any other complications recorded. Age, sex, fracture pattern with classification of condylar fractures into condylar neck or base fractures according to Loukata etal.4 Any associated fracture of mandible describing the anatomical location viz symphysis and parasymphysis (anterior mandible), body, contralateral condyle or greater than 1 associated fracture were recorded. Similarly, the presence or absence of any associated midface fracture was also recorded to suggest that the study participants were homogenous in all aspects. Analytical statistics included χ2 test, t-test, and repeated measures ANOVA followed by post hoc test to compare EMG data (mean power and mean amplitude) between 2 operative approaches (TP vs TMAP) for facial muscles including frontalis, oculi, and buccinator at different time intervals (T0, T1, T2, T3). Patients within each group were also analyzed to check for nerve recovery occurring during the follow-up period. The level of significance was set at P<.05. The study sample was composed of 22 patients with a mean age of 32.82±11.21years in TMAP and 27.82±8.54years in the TP group respectively (P=.26); male predominance of 81.8 and 90.9% in TMAP and TP group respectively (P=.53) was noted. The FN deficit as assessed by the House-Brackmann scale clinically, was at 54% (T1), 36.4% (T2), and 9.1% (T3) for the TP group and 27% (T1),9% (T2), and 0% (T3) for TMAP group; however, the results were statistically insignificant (P=.31). In surface EMG evaluation, the mean power for the frontalis muscle was significantly higher in the TMAP approach at the T3 time (105.03±9.7 vs 89.56±10; 95% confidence interval -24.28 to -6.65 with P value=.002). TP approach was faster with a mean exposure time of 9.9minutes. The results show that both approaches give comparable long-term results with the TMAP group showing better frontalis muscle activity.

Analysis of the effect of different facial nerve managements applied to tumor resection in the jugular foramen region

Objective:To summarize the results of different facial nerve management modalities applied to tumor resection in the jugular foramen region. Methods:The clinical data of 54 patients with tumors in the jugular foramen region who underwent surgery from January 2015 to March 2023 were retrospectively analyzed: 18 males and 36 females; Age ranges from 21 to 67 years, with an average age of 44.4 years; and median follow-up time: 12 months. The House-Brackmann（HB） grading system was applied to assess the patients' facial nerve function before surgery, 1-2 weeks after surgery and at the final follow-up （HBⅠ-Ⅱ grade for good function）: 42 cases with preoperative HB grades Ⅰ-Ⅱ; partial facial nerve transposition（9 cases）, complete facial nerve transposition（28 cases）, and facial nerve excision and re-construction（17 cases） were used, respectively（stage Ⅰor Ⅱ）. Relevant factors affecting postoperative facial nerve function were analyzed. Results:Postoperative pathology confirmed 39 cases of paraganglioma, 9 cases of nerve sheath tumor, 3 cases of meningioma, and 1 case each of fibromucinous sarcoma, chondrosarcoma, and intravascular myofibroma. Facial nerve function after partial facial nerve transposition was HB grade Ⅰ-Ⅱ in 89%（8/9）; after complete facial nerve transposition was HB grade Ⅰ-Ⅱ in 86%（24/28） in 28 cases; after facial nerve severance and reconstruction was HB grade Ⅰ-Ⅱ in 2/7（Stage Ⅰ） and 0/3（Stage Ⅱ）, respectively. Tumor size and surgical approach were correlated with postoperative facial nerve function in patients with facial nerve transposition（P<0.05）. There was no statistically significant difference in facial nerve function after complete and partial facial nerve transposition（P>0.05）. Conclusion:Intraoperative stretching of the facial nerve may be an important factor affecting facial nerve function during surgical treatment of tumors in the jugular venous foramen region; for patients with facial nerve dissection, facial nerve reconstruction should be adopted according to the situation, aiming at the recovery of facial nerve function.

Postoperative effect analysis of different surgical techniques used in facial nerve reconstruction

Objective:To investigate the factors and efficacy of different surgical techniques used in facial nerve（FN） reconstruction. Methods:A retrospective analysis was conducted on 24 patients who underwent facial nerve reconstruction surgery in our department from January 2016 to January 2021. The duration of total facial nerve paralysis was less than 18 months. The study included 5 surgical techniques, including 6 cases of FN anastomosis（Group A）, 5 cases of FN grafting（sural nerve or great auricular nerve）（Group B）, 5 cases of side-to-end facial-hypoglossal nerve anastomosis（Group C）, 4 cases of side-to-end FN grafting（sural nerve or great auricular nerve） hypoglossal nerve anastomosis（Group D）, and 4 cases of dual nerve reanimation（Group E）. The postoperative follow-up period was ≥1 year. Results:The HB-Ⅲ level of FN function at 1 year after surgery was 83.3%（5/6） in group A, 60.0%（3/5） in group B, 40.0%（2/5） in group C, 25.0%（1/4） in group D, and 50.0%（2/4） in group E. In patients without multiple FN repair, the incidence of synkinesis was 15.0%（3/20）, while no cases of synkinesis were observed in patients with dual nerve reanimation. The patients who underwent hypoglossal-facial side-to-end anastomosis showed no hypoglossal nerve dysfunction. Conclusion:Different FN repair techniques result in varying postoperative FN function recovery, as personalized repair should be managed. Among the various techniques, FN end-to-end anastomosis after FN transposition is recommended as to reduce the number of anastomotic stoma, while hypoglossal-facial side-to-end anastomosis is advocated as to prevent postoperative hypoglossal nerve dysfunction. Additionally, dual nerve repair can effectively improve smile symmetry and reduce synkinesis, which enhances patients' quality.

Facial nerve protection in surgery for rare tumors of the internal auditory canal

Objective:To explore strategies for preserving facial nerve function during surgeries for rare tumors of the internal auditory canal. Methods:A total of 235 cases of internal auditory canal tumors treated between 2010 and 2023 were included, encompassing vestibular schwannomas, cavernous hemangiomas, meningiomas, and other rare tumors. Various data, including clinical presentations, imaging classifications, and treatment processes, were meticulously analyzed to delineate the characteristics of rare tumors and assess pre-and postoperative facial nerve function. Results:Among all internal auditory canal tumors, vestibular schwannomas accounted for 91.9%. In rare tumors, facial nerve schwannomas constituted 5.3%, cavernous hemangiomas 26.3%, meningiomas 15.8%, and arterial aneurysms 10.5%. Significantly, patients with cavernous hemangiomas displayed pronounced invasion of the facial nerve by the tumor, in contrast to other tumor types where clear boundaries with the facial nerve were maintained. During surgery, individualized approaches and strategies for facial nerve protection were implemented for different tumor types, involving intraoperative dissection, tumor excision, and facial nerve reconstruction. Conclusion:Preservation of the facial nerve is crucial in the surgical management of rare tumors of the internal auditory canal. Accurate preoperative diagnosis, appropriate timing of surgery, selective surgical approaches, and meticulous intraoperative techniques can maximize the protection of facial nerve function. Personalized treatment plans and strategies for facial nerve functional reconstruction are anticipated to enhance surgical success rates, reduce the risk of postoperative facial nerve dysfunction, and ultimately improve the quality of life for patients.

Clinical Outcomes of Salvage Microsurgical Resection after Radiation Therapy for Sporadic Vestibular Schwannomas

Abstract Background The purpose of this study was to evaluate clinical outcomes after salvage microsurgery for vestibular schwannoma (VS) treated initially with modern radiotherapy techniques as compared to those treated with primary microsurgical resection. Methods Patients who underwent microsurgical resection of sporadic VS undergoing a translabyrinthine approach at a single academic skull base tertiary referral center were included. Baseline and postoperative dynamic gait index, functional gait assessment, House–Brackmann facial nerve grading, and completeness of resection were prospectively recorded. Results Of the 265 patients reviewed, 21 (7.9%) patients underwent prior radiation. Median age of the cohort was 55 years (interquartile range: 51–63). The likelihood of achieving a gross total resection was significantly lower for radiated as compared to nonradiated patients (odds ratio: 0.18, 95% confidence interval: 0.05–0.53, p = 0.004) when controlling for tumor size. Radiated patients had better postoperative facial nerve function on the first postoperative day, but this difference was not significant at long-term follow-up. Radiated patients had lower preoperative postural stability scores than nonradiated patients on FGA (26 vs. 23, p = 0.035). Postoperatively, radiated patients had comparable outcomes compared to nonradiated patients when controlling for age and tumor size. Conclusions Compared to patients with VS treated with surgery alone, previously radiated patients are less likely to achieve gross total resection in the salvage setting. Radiated patients scored better on facial nerve outcomes compared to nonradiated patients in the initial postoperative period but demonstrated similar long-term outcomes.

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

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. 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. 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). 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.

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

ObjectiveThe 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. MethodsData 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. ResultsValid 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%). ConclusionsBR can compensate for the deficiencies of the FCoMEPs. The combination of BR and FCoMEPs can be used in CPA tumor surgery. SignificanceThe 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.

1246 The Impact of Latency Variations on the Predictive Value of Facial Nerve Proximal-to-distal Amplitude Ratio During Vestibular Schwannoma Surgery

INTRODUCTION: Intraoperative facial nerve (FN) electromyographic (EMG) monitoring is now considered an essential part of vestibular schwannoma (VS) surgery and is used for both intraoperative monitoring and postoperative outcome prediction. METHODS: Forty-eight patients underwent FN stimulation at the brainstem (proximal) and the internal acoustic meatus (distal) using a current intensity of 2 mA. The proximal latency and the P/D amplitude ratio were assessed. House-Brackmann grades I-II indicated good FN function; and grades III-VI were considered fair/poor function. A P/D amplitude ratio &gt;0.6 was used as a cutoff to indicate good FN function, while a ratio of =0.6 indicated fair/poor FN function. RESULTS: The P/D amplitude ratio was measured for all patients, and the calculated sensitivity (SE), specificity (SP), positive predictive value (PPV), and negative predictive value (NPV) were 85.2%, 85.7%, 88.5%, and 81.8% respectively. Then the CMAPs from the mentalis muscle were classified based on their proximal latency into: Group I (&lt;6 msec); group II (6-8 msec); and group III (&gt;8 msec). The SE, SP, PPV, and NPV became 90.5%, 90.9%, 95%, and 83.3% respectively in group II. In group I, SE and NPV increased whereas, SP and PPV decreased. While in group III, SP and PPV increased, whereas SE and NPV decreased. CONCLUSIONS: At a latency between 6-8msec, the P/D amplitude ratio was predictive of outcome with high SE and SP. When the latency was &lt;6 msec or &gt;8 msec, the same predictive ability was not observed. Knowing the impact of latency variations of P/D amplitude ratio measurement is important for a better understanding of the ability and limitations of this method in predicting postoperative FN function.

Direct visualization of intraparotid facial nerve assisting in parotid tumor resection

Precise recognition of the intraparotid facial nerve (IFN) is crucial during parotid tumor resection. We aimed to explore the application effect of direct visualization of the IFN in parotid tumor resection. Fifteen patients with parotid tumors were enrolled in this study and underwent specific radiological scanning in which the IFNs were displayed as high-intensity images. After image segmentation, IFN could be preoperatively directly visualized. Mixed reality combined with surgical navigation were applied to intraoperatively directly visualize the segmentation results as real-time three-dimensional holograms, guiding the surgeons in IFN dissection and tumor resection. Radiological visibility of the IFN, accuracy of image segmentation and postoperative facial nerve function were analyzed. The trunks of IFN were directly visible in radiological images for all patients. Of 37 landmark points on the IFN, 36 were accurately segmented. Four patients were classified as House–Brackmann Grade I postoperatively. Two patients with malignancies had postoperative long-standing facial paralysis. Direct visualization of IFN was a feasible novel method with high accuracy that could assist in recognition of IFN and therefore potentially improve the treatment outcome of parotid tumor resection.

Analysis of the outcome of 12 cases of facial nerve tumors

Objective:This study aims to provide a comprehensive summary of the pathogenesis, screening modalities, treatment strategies, repair modalities and preliminary results associated with facial nerve tumors. Methods:A retrospective analysis was conducted on the clinical data of 12 patients with facial nerve tumors who were admitted to our department between May 2018 and February 2023. The study population consisted of 5 males and 7 females, with ages ranging from 35 to 90 years. Clinical symptoms observed in these patients included facial nerve palsy, hearing loss, tinnitus, headache, and otalgia, etc. The severity of facial nerve dysfunction was assessed using the House-Brackmann（H-B） facial nerve function classification, with 3 cases classified as grade Ⅰ, 4 cases as grade Ⅲ, 2 cases as grade Ⅳ, and 3 cases as grade Ⅴ. There was a total of 11 patients who presented with hearing loss. Among these patients, 7 cases were diagnosed with conductive hearing loss, 2 cases with sensorineural hearing loss, and 2 cases with mixed hearing loss. The selection of the observation or surgical route for tumor localization was based on clinical symptoms, facial nerve function grading, and imaging examination results including temporal bone CT and enhanced MRI. Specifically, the location of the tumor was selected for observation or the best surgical route: 2 cases were followed up for observation, 1 case underwent biopsy, and 9 cases underwent tumor resection（7 cases of trans-mastoid approach, 2 cases of combined parotid-mastoidal approach）, concurrent repair of the facial nerve（4 cases of auricular nerve grafting, 3 cases of facial nerve diversion anastomosis, 2 cases of peroneal nerve grafting）. （4 cases of auricular nerve graft, 3 cases of facial nerve diversion anastomosis and 2 cases of peroneal nerve grafting）. Periodic postoperative evaluation of facial nerve function was conducted. Results:1-year follow-up was available. Intraoperatively, it was observed that 66.7%（6 out of 9） of the facial nerve tumors were present in multiple segments. Among these segments, the vertical segment had the highest proportion, accounting for 77.8%（7 out of 9）, followed by the labyrinthine segment/geniculate ganglion with 66.7%（6 out of 9） and the horizontal segment with 55.6%（5 out of 9）. Postoperative pathology confirmed 8 cases with nerve sheath meningioma, Ⅰ with seminal fibroma and 1 with hemangioma. Postoperative facial nerve function was graded as H-B grade I in one patient）, grade Ⅲ in three, grade Ⅳ in four, grade Ⅴ in 2, and grade Ⅵ in 2 patients. The auditory outcomes following surgery are as follows: 8 individuals experienced postoperative hearing loss, while 2 individuals demonstrated postoperative hearing preservation. Conclusion:In the case of patients presenting with facial nerve palsy as their initial symptom, it is imperative to consider the potential presence of a facial nerve tumor. To determine the appropriate course of action, it is necessary to ascertain the size and location of the tumors through imaging examinations. This information will aid in the decision making process regarding whether surgical intervention is warranted, and so, the most suitable approach. Additionally, the choice of repair method during the operation should be guided by the extent of facial nerve defect.

Predictive value of facial motor–evoked potential and electromyography for facial motor function in vestibular schwannoma surgery

PurposeIntraoperative neuromonitoring (IONM) aims to preserve facial nerve (FN) function during vestibular schwannoma (VS) surgery. However, current techniques such as facial nerve motor evoked potentials (FNMEP) or electromyography (fEMG) alone are limited in predicting postoperative facial palsy (FP). The objective of this study was to analyze a compound fEMG/FNMEP approach.MethodsIntraoperative FNMEP amplitude and the occurrence of fEMG-based A-trains were prospectively determined for the orbicularis oris (ORI) and oculi (OCU) muscle in 322 VS patients. Sensitivity and specificity of techniques to predict postoperative FN function were calculated. Confounding factors as tumor size, volume of intracranial air, or IONM duration were analyzed.ResultsA relevant immediate postoperative FP was captured in 105/322 patients with a significant higher risk in large VS. While fEMG demonstrated a high sensitivity (77% and 86% immediately and 15 month postoperative, respectively) for identifying relevant FP, specificity was low. In contrast, FNMEP have a significantly higher specificity of 80.8% for predicting postoperative FP, whereas the sensitivity is low. A retrospective combination of techniques demonstrated still an incorrect prediction of FP in ~ 1/3 of patients.ConclusionsFNMEP and fEMG differ in sensitivity and specificity to predict postoperative FP. Although a combination of IONM techniques during VS surgery may improve prediction of FN function, current techniques are still inaccurate. Further development is necessary to improve IONM approaches for FP prediction.

Subclassification of Koos grade 4 vestibular schwannoma: insights into tumor morphology for predicting postoperative facial nerve function.

Koos grade 4 vestibular schwannoma (KG4VS) is a large tumor that causes brainstem displacement and is generally considered a candidate for surgery. Few studies have examined the relationship between morphological differences in KG4VS other than tumor size and postoperative facial nerve function. The authors have developed a landmark-based subclassification of KG4VS that provides insights into the morphology of this tumor and can predict the risk of facial nerve injury during microsurgery. The aims of this study were to morphologically verify the validity of this subclassification and to clarify the relationship of the position of the center of the vestibular schwannoma within the cerebellopontine angle (CPA) cistern on preoperative MR images to postoperative facial nerve function in patients who underwent microsurgical resection of a vestibular schwannoma. In this paper, the authors classified KG4VSs into two subtypes according to the position of the center of the KG4VS within the CPA cistern relative to the perpendicular bisector of the porus acusticus internus, which was the landmark for the subclassification. KG4VSs with ventral centers to the landmark were classified as type 4V, and those with dorsal centers as type 4D. The clinical impact of this subclassification on short- and long-term postoperative facial nerve function was analyzed. In this study, the authors retrospectively reviewed patients with vestibular schwannoma who were treated surgically via a retrosigmoid approach between January 2010 and March 2020. Of the 107 patients with KG4VS who met the inclusion criteria, 45 (42.1%) were classified as having type 4V (KG4VSs with centers ventral to the perpendicular bisector of the porous acusticus internus) and 62 (57.9%) as having type 4D (those with centers dorsal to the perpendicular bisector). Ventral extension to the perpendicular bisector of the porus acusticus internus was significantly greater in the type 4V group than in the type 4D group (p < 0.001), although there was no significant difference in the maximal ventrodorsal diameter. The rate of preservation of favorable facial nerve function (House-Brackmann grades I and II) was significantly lower in the type 4V group than in the type 4D group in terms of both short-term (46.7% vs 85.5%, p < 0.001) and long-term (82.9% vs 96.7%, p = 0.001) outcomes. Type 4V had a significantly negative impact on short-term (OR 7.67, 95% CI 2.90-20.3; p < 0.001) and long-term (OR 6.05, 95% CI 1.04-35.0; p = 0.045) facial nerve function after surgery when age, tumor size, and presence of a fundal fluid cap were taken into account. The authors have delineated two different morphological subtypes of KG4VS. This subclassification could predict short- and long-term facial nerve function after microsurgical resection of KG4VS via the retrosigmoid approach. The risk of postoperative facial palsy when attempting total resection is greater for type 4V than for type 4D. This classification into types 4V and 4D could help to predict the risk of facial nerve injury and generate more individualized surgical strategies for KG4VSs with better facial nerve outcomes.

Transcanal Endoscopic Facial Nerve Decompression in Posttraumatic Facial Paralysis: A Tertiary Care Experience

Purpose: Facial nerve decompression (FND) for traumatic facial palsy with lesion at geniculate ganglion and tympanic segment can be done through transcanal approach, by a microscope or an endoscope without opening the mastoid. The study analyzes the outcomes of transcanal endoscopic approach (TEA) for FND with regard to improvement in facial nerve (FN) function and hearing status, in lesions limited to perigeniculate and tympanic segment of FN. Methodology: This was a retrospective analysis of the case series from a tertiary care center, of the patients with posttraumatic FN paralysis, surgically treated with TEA. From January 2014 to December 2018, nine patients of traumatic facial palsy were selected for surgery. The patients posted for surgery were selected only when they had immediate-onset FN paralysis after trauma and not responding to treatment of systemic corticosteroid for 14 days with, House Brackmann grading (HBG) IV–VI, lesions confined to perigeniculate ganglion and tympanic segment of FN. Outcome analysis following TEA for FND was performed in terms of postoperative FN function and hearing improvement. Results: The TEA showed a postoperative improvement of FN function (HBG I/II) in 77.7% of patients within 6-month follow-up period. There was no significant improvement in FN function between 6th and 12th month. Postoperative hearing improvement was seen in eight cases, and there was no improvement in one case due to preoperative sensorineural hearing loss. Conclusion: TEA for FND is a direct approach for lesions confined to perigeniculate ganglion area and tympanic segment without involvement of mastoid segment of FN. It requires minimal bone drilling, provides proper visualization, and accurate surgical site assessment. Surgeries performed even in late presentations may have favorable outcomes.

Continuous intraoperative neuromonitoring of the facial nerve predicts postoperative facial palsy in parotid surgery: a prospective study.

Facial palsy (FP) is the most significant complication of parotidectomy. Currently, the use of intermittent intraoperative neuromonitoring (iIONM) in parotid surgery facilitates nerve detection, which is paramount to nerve protection. Continuous IONM (cIONM), as applied in thyroid surgery, enables real-time information on electrophysiological nerve status through continuous nerve stimulation, thereby allowing consequent amplitude analysis. To date, the application of cIONM in parotid surgery has not been noted in literature. We performed parotidectomies with anterograde facial nerve visualization using cIONM in 32 consecutive patients in a prospective study (German Register of clinical studies-DRKS 00011051) during the period October 2016 to January 2020. After the facial trunk had been exposed, an atraumatic stimulation electrode was placed and the nerve was stimulated at 3Hz, at a low threshold (0.62 ± 0.06mA), for the entire duration of the preparation. Selected electrophysiological parameters were collected and compared to postoperative facial nerve function, measured by the House-Brackmann grading system. In the post hoc analysis, a significant correlation between a drop in amplitude (< 50% of the "baseline" amplitude) and postoperative FP was recorded (p = 0.001). True positive prediction of FP was noted in 14 out of 16 patients and true negative in 10 out of 16. The sensitivity was 87.5% (AUC 0.75), with a high negative predictive value of 83.3%. cIONM has significant value in predicting postoperative FP in parotidectomy. Future development of an acoustic/optic warning system in IONM devices could prevent nerve injury in real time.

Analysis of the influencing factors of short-term and long-term facial nerve function after vestibular schwannoma resection via suboccipital retrosigmoid approach

Objective: To summarize the experience of facial nerve(FN) preservation in microsurgical treatment of vestibular schwannoma (VS) resection via suboccipital retrosigmoid approach and to analyze the influencing factors of facial function prognosis in short-term and long-term period. Methods: Patients with VS who underwent microsurgery via suboccipital retrosigmoid approach by the skull base surgery team in Huashan Hospital from January 2013 to February 2018 were enrolled. A total of 308 patients were included in this study, including 132 males and 176 females. The average age was 47.9 year-old (Range: 17-79 year-old). The patient's clinical data and FN function prognosis were recorded. Univariate and multivariate analysis by SPSS 23.0 statistical software were performed to evaluate the factors affecting facial function prognosis and its recovery. Results: Gross total resection was achieved in 304 cases, and subtotal resection was in 4 cases. The facial nerve preservation rate anatomically was 99.4%. The facial nerve of 2 cases was thin due to large tumor compression and severed, and a one-stage reconstruction was performed during surgery.Of the 308 patients, 300 cases were successfully followed up, and 8 cases were lost to follow-up. The mean follow-up time was 52 months. In short-term (2 weeks after surgery), satisfactory facial nerve function (House-Brackmann (H-B) grade Ⅰ-Ⅱ) was achieved in 96 cases, and 212 cases were unsatisfactory function (H-B grade Ⅲ-Ⅵ). After 1 year, 198 were satisfactory function and 97 were unsatisfactory. After 3 years, 219 were satisfactory function and 75 were unsatisfactory. Five years later, 155 were satisfactory function and 34 were unsatisfactory. According to the results of logistic regression analysis, the impact factors of FN function in short-term were tumor size (P=0.011) and stimulation threshold (ST) of EMG monitoring (P<0.001). The impact factors in long-term were tumor size (P=0.005), ST of EMG monitoring (P=0.005) and FN rehabilitation training. Conclusions: Tumor diameter is an independent factor related to FN function, and the larger the tumor, the worse the postoperative FN function. The ST of EMG (ST≤0.05 mA) can predict short-term and long-term FN function. The systematic facial rehabilitation training can effectively promote the recovery of FN after surgery.

The value of radiographic features in predicting postoperative facial nerve function in vestibular schwannoma patients: Aretrospective study and nomogram analysis.

The purpose of this study was to identify significant prognostic factors associated with facial paralysis after vestibular schwannoma (VS) surgery and develop a novel nomogram for predicting facial nerve (FN) outcomes. Retrospective data were retrieved from 355 patients who underwent microsurgery via the retrosigmoid approach for VS between December 2017 and December 2022. Univariate and multivariate logistic regression analysis were used to construct a radiographic features-based nomogram to predict the risk of facial paralysis after surgery. Following a thorough screening process, a total of 185 participants were included. The univariate and multivariate logistic regression analysis revealed that tumor size (p = 0.005), fundal fluid cap (FFC) sign (p = 0.014), cerebrospinal fluid cleft (CSFC) sign (p < 0.001), and expansion of affected side of internal auditory canal (IAC) (p = 0.033) were independent factors. A nomogram model was constructed based on these indicators. When applied to the validation cohort, the nomogram demonstrated good discrimination and favorable calibration. Then we generated a web-based calculator to facilitate clinical application. Tumor size, FFC and CSFC sign, and the expansion of the IAC, serve as good predictors of postoperative FN outcomes. Based on these factors, the nomogram model demonstrates good predictive performance.

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

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. 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. 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%). 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.

Facial and Cochlear Nerves Outcomes in the Surgical Resection of Giant Vestibular Schwannoma: Is There Any Predictive Value for Intraoperative Neuromonitoring of the Facial Nerve?

Background: Giant vestibular schwannoma (VS) represents one of the most challenging interventions in skull base surgery. Preserving facial and cochlear nerves requires effective surgical planning and nuanced techniques. Objectives: The present study evaluates the role of intraoperative neuromonitoring (IONM) in predicting the outcome of facial and cochlear nerves. Methods: This retrospective cohort comprised 34 patients with a giant (Samii IV/IVb grade) VS during 2016 - 2019. The retrosigmoid approach was used for tumor resection. Pre- and postoperative facial exams were graded according to the House-Brackmann Scale. Hearing ability was also classified according to the Hannover Hearing Classification. Intraoperative findings included the location of the nerve complex, tumor consistency, the surgical plane of the tumor from the facial nerve/ brainstem, and the level of internal auditory canal (IAC) decompression. Intraoperative neuromonitoring was used for all surgeries. The amplitude required for a positive response was recorded during the facial nerve's direct electrical stimulation (DES). All patients were followed 6 and 12 months postoperative. Results: The preoperative facial nerve function was normal in 91.2% of patients, and 8.8% had slight facial nerve impairment (FNI). Considering preoperative hearing status, 9 cases (26.5%) had moderate hearing loss or impairment, while 25 patients (73.5%) complained of severe hearing impairment. The mean intraoperative direct facial nerve stimulation threshold was 1.38 ± 0.89. Hearing impairment was moderately severe in 7 (20.6%) and severe in 25 patients (73.5%) postoperation. In addition, postoperative assessment revealed 13 (38.2%) cases with moderate FNI and 12 (35.2%) with moderately severe FNI. The tumor size did not affect the postoperative hearing loss, and the postoperative hearing loss did not improve significantly (P = 0.32). There was no statistically significant correlation between the intensity of intraoperative DES and postoperative facial nerve function (P &gt; 0.05). No significant correlation was observed between tumor consistency and postoperative hearing status (P &gt; 0.05). Conclusions: The retrosigmoid approach combined with IONM appears to be associated with favorable facial and cochlear nerve outcomes in giant VS. The postoperative facial nerve function may improve, but sensorineural hearing status may not improve significantly. Moreover, the intensity of intraoperative DES may not predict the postoperative facial function. Therefore, the findings of IONM should be interpreted carefully.