Intraoperative electromyography for predicting facial function in vestibular schwannoma surgery.

OBJECTIVE: To assess the validity of intraoperative minimal stimulation threshold (MST) for predicting long-term facial function after vestibular schwannoma surgery. STUDY DESIGN: Prospective blinded study. METHODS: MST after tumor dissection and postoperative clinical facial function, assessed using the House Brackmann grading system (HB), were used to predict long-term clinical facial function, recorded at least 6 months after surgery. RESULTS: Two hundred and nine consecutive patients fulfilled selection criteria and 184 had successful intraoperative electrophysiologic monitoring and were eligible for further study. MST of 0.05 mA had moderate accuracy for predicting good long-term facial function, with 94% sensitivity, 91% positive predictive value (PPV), 60% specificity, and 70% negative predictive value (NPV). A more relevant group of 77 patients with poor postoperative facial function (HB III-VI) were assessed for predicting good long-term function. Applying this criteria, test accuracy fell, with 83% sensitivity, 64% PPV, 60% specificity, and 75% NPV. Postoperative clinical facial function had a greater accuracy for predicting good long-term function, with 83% sensitivity, 79% PPV, 75% specificity, and 79% NPV. A model of predicted probabilities of good outcome (HB I and II) was derived from a logistic regression with two additive predictors (postoperative HB and MST). This demonstrated that for patients with postoperative HB grade V, MST aided prediction. CONCLUSIONS: Intraoperative stimulation thresholds, when assessed against a relevant group of patients with poor postoperative facial function, had poor predictive accuracy. The severity of immediate postoperative clinical facial function was the most accurate predictor of long-term outcome. MST aided long-term prediction in a small but relevant group of patients with postoperative HB grade V facial function.     

Factors which influence the facial nerve outcome in vestibular schwannoma surgery

A series of 276 patients with a unilateral vestibular schwannoma has been analysed with respect to the factors affecting post-operative facial nerve outcome. Age, tumour size, operative approach and the use of intra-operative facial nerve monitoring have been examined. The tumours were removed via either a translabyrinthine or a retrosigmoid approach. In this series increasing age and increasing tumour size were associated with a worse facial nerve outcome. The use of intra-operative facial nerve monitoring and the retrosigmoid approach were both associated with a better facial nerve outcome. Those patients having a retrosigmoid approach had a facial nerve result that was over one House grade better than those having translabyrinthine tumour removal.     

Hearing preservation and facial nerve function in vestibular schwannoma surgery

The objective of this study was the assessment of hearing preservation in vestibular schwannoma surgery. This study reports a prospective cohort of 40 patients with clinically useful hearing from a consecutive series of 191 patients with unilateral vestibular schwannoma. The patients were managed in a tertiary centre by a combined team of Neurosurgeon, Otologist and Neuro-monitoring Scientist via a neuro-oto-surgical-retrosigmoid approach. Pure tone speech audiometry was conducted preoperatively and 6 months to 9 years following surgery. Using the AA0-HNS classification, useful hearing, i.e. grades A, B and C, was preserved in 47.5% of patients. Thirty-eight per cent achieved grade A or B. Using appropriate surgical and monitoring techniques, it is possible to preserve useful hearing in approximately 50% of patients following removal of a vestibular schwannoma via the retro-sigmoid approach.     

Comparison between intraoperative observations and electromyographic monitoring data for facial nerve outcome after vestibular schwannoma surgery

A four-channel device may enhance the sensitivity of electromyography (EMG). Determination of stimulation thresholds (STs) below 0.05 mA improves facial prognostic information after vestibular schwannoma (VS) surgery.To compare intraoperative observations with electromyographic data for predicting the immediate facial function outcome after VS surgery.A total of 111 VS patients operated on and intraoperatively monitored using four-channel facial EMG between October 2002 and September 2003 were included in this multicentre, prospective study. Mascular activity detection was performed in the frontal, orbicularis oculi, orbicularis oris and platysma muscles. Intraoperative observations were made concerning adhesion and nerve stretch, and facial function was graded (House-Brackmann classification) at postoperative Days 1 and 8.Facial function at postoperative Days 1 and 8 was related to the intraoperative nerve STs at the brainstem and in the adhesion zone (range 0.01-3 mA for a response > 100 microV). At postoperative Day 8, good facial function (Grades 1 or 2) was observed in 93% of cases for STs in the adhesion zone of 0.01-0.04 mA, 85% for STs of 0.05-0.3 mA and 79% for STs > 0.3 mA. These STs were related to the degree of tumor adhesion and not to the nerve stretch. The maximal EMG response was detected in the frontal or platysma muscles in 26% of cases, and in the orbicularis oris and orbicularis oculi muscles in 74%.     

Comparison between intraoperative observations and electromyographic monitoring data for facial nerve outcome after vestibular schwannoma surgery

Conclusions

A four-channel device may enhance the sensitivity of electromyography (EMG). Determination of stimulation thresholds (STs) below 0.05 mA improves facial prognostic information after vestibular schwannoma (VS) surgery.

Objective

To compare intraoperative observations with electromyographic data for predicting the immediate facial function outcome after VS surgery.

Material and methods

A total of 111 VS patients operated on and intraoperatively monitored using four-channel facial EMG between October 2002 and September 2003 were included in this multicentre, prospective study. Mascular activity detection was performed in the frontal, orbicularis oculi, orbicularis oris and platysma muscles. Intraoperative observations were made concerning adhesion and nerve stretch, and facial function was graded (House–Brackmann classification) at postoperative Days 1 and 8.

Results

Facial function at postoperative Days 1 and 8 was related to the intraoperative nerve STs at the brainstem and in the adhesion zone (range 0.01–3 mA for a response?>?100 µV). At postoperative Day 8, good facial function (Grades 1 or 2) was observed in 93% of cases for STs in the adhesion zone of 0.01–0.04 mA, 85% for STs of 0.05–0.3 mA and 79% for STs?>?0.3 mA. These STs were related to the degree of tumor adhesion and not to the nerve stretch. The maximal EMG response was detected in the frontal or platysma muscles in 26% of cases, and in the orbicularis oris and orbicularis oculi muscles in 74%.     

面神经与前庭神经鞘膜瘤的空间位置对术后面神经功能恢复的影响

目的：探讨面神经（FN）与前庭神经鞘膜瘤（VS）空间位置对于术后FN功能恢复的影响。方法：101例单侧VS患者,采用扩大迷路径路显微全切除肿瘤,观察术中FN-VS空间位置,分为4型：第1位置为FN位于VS前方,第2位置为FN位于VS前上方,第3位置为FN位于VS上方,第4位置为FN位于VS后方。根据House-Brackmann面神经分级法评价患者术后7、30、90、180d的FN功能。结果：术中FN解剖保留率达98％,术中发现FN—VS空间位置有43％为第1位置,33％为第2位置,24％为第3位置,未发现第4位置。术后180d 73％FN功能良好,且随VS直径增大,术后FN功能良好率递减。FN—VS空间位置与术后FN功能呈显著相关,第1位置至第3位置术后FN功能良好率呈递减关系。结论：术中FN解剖保留率并不平行于术后FN功能良好率,VS直径与术后FN功能良好率相关,而FN—VS空间位置能够预测术后FN功能良好率。     

Evolution of facial nerve prognosis in vestibular schwannoma surgery by translabyrinthine approach

OBJECTIVES OF THE STUDY: To evaluate our results on the postoperative facial function, its pre and preoperative predictive factors, and the application of the surgical technique to lesions of decreasing size. PATIENTS AND METHODS: A series of 248 patients operated of an unilateral vestibular schwannoma has been reviewed. We have compared the results gathered over two periods corresponding to the evolution of our surgical technique since 1998. RESULTS: Immediate and 1 year postoperative facial function is significantly better among patients operated after 1998 (satisfactory in 75 and 88% respectively). This trend marked by the improvement of the results since 1998 has to be discussed according to other predictive factors. One of predictive factor is the decrease of the size of the lesion during the same period. The other factors are the hearing level, deafness duration, trigeminal nerve involved, vestibular status and ABR desynchronization. CONCLUSION: The positive predictive factors are usually correlated with the size of the tumour This implies the necessity of an early diagnosis of the schwannomas. The second predictive factor of the facial function is the use of a soft surgical technique.     

Total facial paralysis after vestibular schwannoma surgery: probability of regaining normal function

The aim of the present study was to ascertain the precise fraction of vestibular schwannoma cases that recover to normal function after postoperative total facial nerve paralysis and to compare our results with those presented in the literature. This was a retrospective case review of 631 cases. Among the 132 cases with immediate postoperative facial nerve palsy (House Brackmann [HB] grade VI), only 2 (1.5%) recovered to normal function (HB grade I). In an attempt to compare our results with those of other series in the literature, we found a large variation in the incidence of recovery of this group of patients to grade I, ranging from 0% to 50%. Our analysis of the reported data revealed widely varying methods of data collection and presentation, making a scientifically valid comparison particularly difficult. According to our data, complete (HB grade I) or near-complete (HB grade II) facial nerve function recovery from an immediate postoperative grade VI palsy is extremely rare.     

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.     

Functional outcome of retrosigmoid approach in vestibular schwannoma surgery

CONCLUSION: The retrosigmoid approach for small vestibular schwannomas (VS) yields a high rate of facial function preservation. Hearing preservation rates depend on tumor size and preoperative hearing. OBJECTIVES: To report the results and to investigate the prognostic factors for hearing preservation after removal of small VS by a retrosigmoid approach. PATIENTS AND METHODS: From October 1994 to July 2005, 110 VS removed through a retrosigmoid approach were included in this retrospective study. Preoperative and postoperative clinical, audiometric, videonystagmographic, and imaging data were collected. The mean follow-up period was 23+/-20.7 months (range 1-110). RESULTS: The preservation of a good facial function (House and Brackmann grade 1-2) was achieved in 91% of patients at 1-2 years after surgery. Among patients with a preoperative class A or B (n=99), a postoperative serviceable hearing (AAO-HNS classes A and B) was preserved in 36% and a useful hearing (classes A, B, and C) in 44%. Hearing preservation appeared to be influenced by tumor size and preoperative hearing. Multiple regression analysis of the preoperative factors influencing the hearing outcome showed that preoperative high frequency pure tone thresholds associated with tumor size were better correlated to postoperative pure tone average (PTA) than preoperative low frequencies.     

Primary parotid malignoma surgery in patients with normal preoperative facial nerve function: outcome and long-term postoperative facial nerve function

Objectives/Hypothesis: Most patients with primary parotid cancer present with normal facial nerve function. The common surgical strategy for these patients is to perform a parotidectomy with facial nerve preservation. Nevertheless, the functional outcome for the facial nerve and oncological outcome is unclear. Study Design: Medical records of 211 patients treated from 1986 to 2000 in an university hospital were reviewed. One hundred seven patients with primary surgery for primary parotid cancer and long‐term follow‐up were analyzed retrospectively. Methods: The characteristics, treatment, and oncological outcome were evaluated using hospital chart data. All patients with postoperative facial paresis were had follow‐up with electromyography until recovery or permanent paresis became apparent. Results: Ninety‐one patients had a normal preoperative function. Facial nerve preservation during surgery by total parotidectomy was possible in 79 patients, whereas in 28 patients a radical parotidectomy was necessary. Otherwise, the oncological characteristics of both groups were not different. Directly after total parotidectomy, half of the patients presented a facial paresis but only two patients (2%) developed a permanent partial paresis. The 5‐year disease‐free rate and the 5‐ and 10‐year survival rates were 65%, 83%, and 54%, respectively. After radical parotidectomy, the results were not significantly different. The 5‐year disease‐free rate and the overall 5‐ and the 10‐year survival rates were 56%, 62%, and 42%, respectively. Conclusion: Treatment of primary parotid cancer with preoperatively normal facial nerve function by standardized parotidectomy and precise microsurgical preservation of the facial nerve is often possible. This approach demonstrates favorable oncological results with a low level of long‐term facial nerve morbidity.     

Management of facial nerve schwannoma in patients with favorable facial function

OBJECTIVE: We report six cases of facial nerve schwannomas in which surgical management allowed the preservation of facial nerve function. Specifically, this paper reports that a stripping surgery may provide favorable functional outcomes. STUDY DESIGN: A retrospective review of preoperative and postoperative data for six patients with facial nerve schwannoma that had normal facial nerve function or a House-Brackmann grade II facial palsy before the surgery. METHODS: Stripping surgery, which removed the schwannoma from the remaining nerve fascicle, was attempted on the six patients. Postoperative facial nerve function and imaging (magnetic resonance imaging) were evaluated. RESULTS: Stripping surgery with gross total tumor removal of the mass was performed in four cases. In the two remaining cases, the stripping surgery was not possible, and decompression alone was performed. Favorable preservation of facial function was achieved in all six cases. CONCLUSION: It was possible to preserve facial function after surgery to remove facial nerve schwannoma. We suggest that stripping surgery, focused on the preservation of continuity of the facial nerve, may be attempted for facial nerve schwannoma in which favorable facial function has been preserved.     

Pre- and intraoperative predictive factors of facial palsy in vestibular schwannoma surgery

CONCLUSION:S These results support previous ones with regard to FN risk factors in VS surgery. However, they also provide new preoperative factors that influence postoperative FN function, such as clinical symptoms, the nature of the surgical procedure (use of laser) and ABR results. OBJECTIVE: To determine pre- and perioperative factors influencing facial nerve (FN) outcome in vestibular schwannoma (VS) surgery. MATERIAL AND METHODS: A total of 424 patients undergoing VS surgery were included in this retrospective study. Patients were divided into two groups according to the existence or absence of a FN palsy during the 8 days following surgery (Groups 1 and 2, respectively). Various parameters were evaluated preoperatively as follows. Quantitative parameters: age; duration of clinical symptoms; pure-tone audiometry (PTA) results; speech reception threshold; speech discrimination score; auditory brainstem response (ABR) results; and transient-evoked otoacoustic emission amplitude. Qualitative parameters: gender; side of the tumor; angle between the tumor and the internal auditory canal (VS/IAC angle) < or = or > 30 degrees; MRI aspect (n = 69); surgical approach; ease of the surgical procedure, the use or non-use of laser dissection; and the histological Antoni's type of the tumor. RESULTS Pre- and perioperative factors that differed significantly between Groups 1 and 2 were as follows. Quantitative factors: tinnitus duration was longer and PTA and ABR results were worse in Group 1. Qualitative factors: heterogenous/cystic MRI aspect, use of retrosisgmoid and middle fossa approaches, easy surgical procedure, dissection without laser and Antoni's type A were more frequently found in Group 1.     

颞骨面神经鞘瘤显微手术预后因素分析

目的探讨影响颞骨面神经鞘瘤显微手术疗效的因素。方法回顾分析13例颞骨面神经鞘瘤患者的临床及随访资料，并运用统计软件SPSS10．0进行Spearman等级相关分析和非参数两独立样本Mann—WhitneyU检验。结果13例患者均接受显微外科手术治疗，11例同时接受了面神经重建，1例失访，接受随访者皆无肿瘤残留或复发，术后面神经功能达House-Brackman（HB）分级Ⅱ～Ⅴ。Spearman相关分析表明术后面神经功能分级与术前面神经麻痹持续时间（r=0．925，P〈0．01）和术前面神经功能分级（r=0．712，P〈0．05）相关。经非参数两独立样本Mann—Whitney U检验，发现面神经受累部位对面神经重建功能的影响无统计学意义（P〉0．05）。结论术前面神经麻痹持续时问越长和术前面神经功能越差，术后面神经功能越差；对于面肌已失神经支配，但仍存在面肌电图纤颤电位者，或高位面神经鞘瘤者，仍应考虑面神经重建。     

伴或不伴轻微面神经麻痹的面神经鞘瘤的诊治分析

目的 探讨伴或不伴轻微面神经麻痹的面神经鞘瘤的临床表现、诊断及治疗.方法 回顾性分析8例资料完整、面神经功能House-Brackmann分级(HB)≤Ⅱ级的面神经鞘瘤患者诊断及治疗过程.结果 8例患者均不以面神经麻痹为首发症状且均有误诊史,其中6例存在误治史.术前均行CT和(或)MRI检查,证实肿瘤位于面神经的不同位置.4例术中保留面神经行肿瘤切除术,术后随访17～180个月,面神经功能(HB)Ⅱ～Ⅲ级;2例术中发现肿瘤侵犯广泛,破坏耳蜗及前庭,与面神经无法分离,予以牺牲神经切除肿瘤,行耳大神经移植术,术后分别随访56和79个月,面神经功能(HB)Ⅳ级;1例拒绝牺牲面神经,术中行面神经减压术,术后11个月面神经功能Ⅱ级,肿瘤无增大;1例术中发现肿瘤来源于鼓索神经,予以牺牲面神经分支,并行面神经减压术,术后11个月面神经功能Ⅱ级.结论 面神经功能分级(HB)≤Ⅱ级的面神经鞘瘤多不以面神经麻痹为首发症状,诊断困难.手术方法取决于肿瘤的特点、范围和患者的意愿.对明确面神经来源的肿瘤,如果肿瘤与面神经之间容易分离,可以保留面神经行肿瘤切除;如果不易分离,当肿瘤侵犯桥小脑角、内听道、耳蜗、前庭时,可以考虑牺牲面神经;对拒绝牺牲面神经者,可行面神经减压术,并定期影像学随访.     

Facial nerve monitoring parameters as a predictor of postoperative facial nerve outcomes after vestibular schwannoma resection.

OBJECTIVE: To evaluate whether the intraoperative stimulus threshold and response amplitude measurements from facial electromyography can predict facial nerve function at 1 year after vestibular schwannoma resection. STUDY DESIGN: Prospective study. SETTING: Tertiary academic center. PATIENTS: Seventy-four consecutive vestibular schwannoma patients. INTERVENTION: The minimal stimulus intensity (in milliamperes) and electromyographic response amplitude (in microvolts) were recorded during stimulation applied to the proximal facial nerve after vestibular schwannoma removal. MAIN OUTCOME MEASURE: Facial nerve outcomes at 1 year were evaluated using the House-Brackmann scale. Analysis was then performed to evaluate whether these electrophysiologic recordings and tumor size could predict facial nerve functional outcomes. RESULTS: Of the 74 patients, 66 of 74 (89%) had House-Brackmann Grade I or II facial nerve function and 8 of 74 (11%) had House-Brackmann Grade III-VI function at 1 year after surgery. If standards were set for intraoperative minimal stimulus intensity of 0.05 mA or less and response amplitude of 240 microV or greater, the authors were able to predict a House-Brackmann Grade I or II outcome in 56 of 66 (85%) patients at 1 year after surgery. With these same electrophysiologic parameters, only 1 of 8 (12%) House-Brackmann Grade III-VI patients also met this standard and thus gave a false-positive result. Logistic regression analysis of the data showed that both a stimulus threshold of 0.05 mA or less and a response amplitude of 240 microV or greater predicted a House-Brackmann Grade I or II outcome with a 98% probability. However, stimulus threshold or response amplitude alone had a much lower probability of the same result. In addition, although tumor size was found to independently predict facial nerve outcomes at 1 year, it did not improve the ability to predict facial nerve function over a model using stimulus intensity and amplitude alone. CONCLUSION: Individually, minimal stimulus intensity or response amplitude was less successful in predicting long-term postoperative facial nerve function. However, if both parameters are considered together, the study demonstrates that they are good prognostic indicators for facial nerve function at 1 year after surgery.     

Outcome on hearing and facial nerve function in microsurgical treatment of small vestibular schwannoma via the middle cranial fossa approach

Encouraging results regarding hearing preservation and facial nerve function as well as increasing understanding of the natural behaviour of vestibular schwannomas have led to the recommendation of an early treatment in small VS. The aim of the present study was to evaluate current data on functional outcome of patients with small VS treated by middle cranial fossa (MCF) approach. A retrospective chart study of all cases treated by MCF approach between October 2007 and September 2011 was performed. Records were analyzed regarding demographical data, tumor size, hearing status, vestibular function and facial nerve function. Facial nerve function was classified according to the House–Brackmann scale (HB). Hearing status was classified according to the American Association of Otolaryngology-Head and Neck Surgery (AAO-HNS) and a modified classification of Gardner and Robertson (GR). Eighty-nine patients were included in the study; 41 % of VS was classified as intracanalicular (stage 1) and 59 % as stage 2. From 65 patients with a preoperative hearing status according to AAO-HNS A or B, 74 % still presented with A or B after surgery. Using a modified GR classification, from 70 patients categorized as class I or II prior to surgery, 70 % were still class I or II. Looking to the facial nerve function 1 week after surgery, 82 % of patients presented with HB 1 or 2. Three to twelve months later, 96 % demonstrated HB 1 or 2. A persisting facial palsy was recorded in four patients. Preoperative hearing status was evaluated as a prognostic factor for postoperative hearing, whereas no influence was detected in ABR, vestibular function and tumor length. Early diagnosis of small VS due to high-sensitive MRI requires the management of this tumor entity. Natural behaviour of VS in many cases demonstrates an increase of tumor size over time with deterioration of hearing status. The presented data underline the recommendation of an early surgical treatment in small VS as a valuable option for hearing preservation in the therapy of VS.     

Preservation of the auditory nerve function after translabyrinthine removal of vestibular schwannoma

OBJECTIVE: To evaluate the function of the postoperative auditory nerve preserved after translabyrinthine (TL) vestibular schwannoma (VS) removal. METHODS: Fifteen patients, who underwent unilateral VS resection via a TL approach, were preserved auditory nerve anatomically. The size and location of VS were measured on MRI preoperatively. After surgery, the electrical stimulation test (EST) or electrically evoked auditory brainstem response (EABR) was performed. RESULTS: Four cases (27%) out of fifteen patients were retained the functional integrity of the auditory nerve after surgery. The maximum tumor size in the group with a positive response to EST or EABR was significantly smaller than that in the group with a negative response to EST. It seems to be difficult to preserve auditory nerve function in cases where a tumor extends to the fundus of internal auditory canal. CONCLUSION: These results suggest that size of tumor and/or extension of tumor to the fundus might be important factors in preserving the auditory nerve function even if using a TL approach.