Prediction of postoperative facial nerve function in acoustic neuroma surgery

There is a need for an uncomplicated, consistent method to predict facial nerve function after acoustic neuroma surgery. A prospective study with a 2-year follow-up of 35 patients undergoing acoustic neuroma surgery was performed assessing how well intraoperative facial nerve monitor electrophysiological thresholds and facial function postsurgery can predict ultimate nerve function. Tumour size was a strong predictor of immediate (P-value < 0.0005) and long-term facial nerve function (P-value = 0.004). Immediate facial nerve function was strongly predicted by stimulus intensity (P-value = 0.007) and there was a suggestion of a relationship between long-term facial nerve response and stimulus intensity. It was not possible to predict delayed facial dysfunction nor the extent or timing of recovery of abnormal function. It is concluded that the combination of facial function at 1 month postsurgery with tumour size and stimulus thresholds is the best available indicator of ultimate facial function.     

Prediction of facial nerve function following acoustic neuroma resection using intraoperative facial nerve stimulation

Methods of monitoring the facial nerve during posterior fossa surgery continue to evolve. In an effort to predict acute and final facial nerve function following acoustic neuroma resection, the lowest current applied to the facial nerve at the brainstem necessary to elicit facial muscle response was measured using strain gauge and electromyographic facial nerve monitors. A retrospective analysis of 121 patients who had undergone acoustic neuroma surgery was performed. Sixty-five patients had intraoperative facial nerve monitoring and 44 had sufficient data for inclusion in this study. The acute and final facial nerve functions, according to the House-Brackmann classification, were assessed with regard to intraoperative stimulation-current thresholds. Nineteen of 20 patients who required 0.10 mA or less to elicit a facial muscle response had a House-Brackmann grade I facial nerve outcome. The upper limit of the 95% confidence interval of stimulation threshold for patients with a final grade I facial nerve function is 0.17 mA. All of the patients in this study, with stimulation thresholds ranging up to 0.84 mA, had a final grade III or better result. A poor outcome in our series, a final grade III facial nerve function, is best predicted by a poor acute result, specifically an acute grade VI_A facial nerve function. We suggest that it is possible to predict the facial nerve function based on intraoperative threshold testing.     

Preservation of hearing and facial nerve function in resection of acoustic neuroma.

The surgical results in 78 recent cases of total removal of unilateral acoustic neuroma in which an attempt was made to preserve cochlear function have been added to the authors' previous series of 66 cases to evaluate the factors influencing the ability to preserve useful hearing. Useful hearing was defined by speech reception threshold no poorer than 70 dB and a discrimination score of at least 15%. Analysis using a logistic regression model showed that certain preoperative clinical parameters such as tumor size, speech discrimination score, and gender were significantly correlated with hearing outcome. Favorable outcome was significantly correlated with smaller tumor size, higher preoperative speech discrimination score, and male sex. From this data, an explicit formula was devised for predicting hearing outcome for an individual patient. In four cases with useful hearing preserved, there was improvement of greater than 15 percentage points in speech discrimination scores. While preoperative auditory brainstem responses were not predictive of hearing preservation, monitoring of intraoperative auditory evoked potentials was predictive of hearing outcome in selected cases. Specifically, when wave V was unchanged at the end of the operation, even if it may have been transiently lost during surgery, useful hearing was invariably preserved.     

Preservation of hearing and facial nerve function in surgery for acoustic neuroma]

The results concerning the preservation of hearing and facial nerve function in 71 patients with 74 acoustic neuromas operated on from 1979 to 1990 are presented. All patients have been operated on in half-sitting position by one surgeon using the suboccipital-transmeatal approach. Postoperative facial nerve function was good (House degree I or degrees II) in 42/73 patients (58%), moderate (House degrees III or degrees IV) in 13/37 (18%), and poor (House degrees V or degrees VI) in 18/73 (24%). Preservation of useful hearing was achieved in 17%. The smaller the tumour and the easier the preparation the better was the functional result. Beside anatomic integrity of nerves and endolymphatic system the internal auditory artery as the most important vessel for the inner ear blood supply should be respected. The cochlear nerve intact in 47 patients we only found one case with recurrent tumour in a patient with neurofibromatosis 2. Preservation of the cochlear nerve did not have an increased risk of tumour recurrence in our group of patients.     

神经电生理监测下听神经瘤显微手术中面神经的保护

目的总结分析术中神经电生理监测结合显微手术操作技巧在听神经瘤手术中预防面神经损伤的作用。方法选取我科2011～2012年施行乙状窦后入路显微手术的大型及中型听神经瘤（肿瘤直径≥2.4 cm）患者62例,术中应用神经电生理监测技术对手术进行综合监护,同时密切留意骨性解剖、蛛网膜解剖、神经与血管解剖关系。术后随访6个月,评估肿瘤切除程度并根据House-Brack-mann面神经功能分级对患者面神经功能进行评估。结果肿瘤全切除58例（93.5%）,次全切除4例（6.5%）;无围手术期死亡患者。面神经功能评定：Ⅰ级57例（91.9%）,Ⅱ级5例（8.1%）。结论对于大型和中型听神经瘤患者,术中进行综合电生理监护,同时操作时注意典型的解剖位置与熟练的显微手术技术,可达到较高的肿瘤全切除率,并尽可能地保全面神经功能。     

Hypoglossal‐facial nerve anastomosis: assessment of clinical results and patient benefit for facial nerve palsy following acoustic neuroma excision

Despite advances in neuro‐otological techniques permanent complete facial palsy may still occur in up to 10% of patients undergoing removal of cerebellopontine angle tumours. Hypoglossal‐facial nerve anastomosis is the procedure of choice in our unit for facial reanimation in such patients and below we report the results of hypoglossal‐facial nerve anastomosis performed on 29 patients. Assessment of patient benefit from hypoglossal‐facial nerve anastomosis was obtained using a questionnaire based on the Glasgow Benefit Inventory. The results showed all patients to have an improvement in their House Brackmann grade following hypoglossal‐facial anastomosis with 65% achieving grade III or better. Of the 20 patients who completed the questionnaire, 18 showed a positive benefit (median score 59.5, range 40–77). There was a significant correlation (P < 0.045) between the Glasgow benefit inventory score and House Brackmann grade. Outcome was not affected by the time interval between the acoustic neuroma surgery and performing the hypoglossal‐facial nerve anastomosis, sex or length of follow‐up. However the Glasgow benefit score was significantly influenced by age (P = 0.023) with younger patients showing more benefit independent of improvement in facial nerve function.     

Distance from acoustic neuroma to fundus and a postoperative facial palsy.

OBJECTIVE/HYPOTHESIS: Generally, patients with small acoustic neuroma have less facial palsy after its removal. The middle cranial fossa approach is mainly applied to the small acoustic neuroma and tumor size does not influence the prognosis of facial palsy. The internal auditory canal cannot be fully opened in the middle cranial fossa approach, and the facial nerve is tightly attached in the fundus. According to these anatomical factors, we hypothesized that acoustic neuromas located away from the fundus might be removed with less facial nerve damage. We investigated the distance between the acoustic neuroma and fundus and its clinical relationship. STUDY DESIGN: Retrospective study of 45 patients with acoustic neuroma who underwent a middle cranial fossa approach. METHODS: The distance between the acoustic neuroma and fundus and the tumor diameter were measured on T2-weighted and contrast-enhanced magnetic resonance images, respectively. These data were compared with the postoperative facial nerve function. RESULTS: The mean distance was 3.0 +/- 1.8 mm (range, 0-10 mm), and the mean diameter was 11.3 +/- 3.7 mm (means +/- standard deviation; range, 4-20 mm). Neither the distance nor the diameter had any correlation to the degrees of postoperative facial palsy either immediately or at 3 months after surgery. CONCLUSIONS: As far as the nerve was anatomically preserved, postoperative facial nerve function seemed to be influenced by factors other than surgical manipulation among small acoustic neuromas. Although the tumor fills in the fundus, it may not influence postoperative facial nerve function and also may not interfere with indication of the middle cranial fossa approach for removal of the acoustic neuroma.     

Hypoglossal-facial nerve anastomosis: assessment of clinical results and patient benefit for facial nerve palsy following acoustic neuroma excision

Despite advances in neuro-otological techniques permanent complete facial palsy may still occur in up to 10% of patients undergoing removal of cerebellopontine angle tumours. Hypoglossal-facial nerve anastomosis is the procedure of choice in our unit for facial reanimation in such patients and below we report the results of hypoglossal-facial nerve anastomosis performed on 29 patients. Assessment of patient benefit from hypoglossal-facial nerve anastomosis was obtained using a questionnaire based on the Glasgow Benefit Inventory. The results showed all patients to have an improvement in their House Brackmann grade following hypoglossal-facial anastomosis with 65% achieving grade III or better. Of the 20 patients who completed the questionnaire, 18 showed a positive benefit (median score 59.5, range 40-77). There was a significant correlation (P < 0.045) between the Glasgow benefit inventory score and House Brackmann grade. Outcome was not affected by the time interval between the acoustic neuroma surgery and performing the hypoglossal-facial nerve anastomosis, sex or length of follow-up. However the Glasgow benefit score was significantly influenced by age (P = 0.023) with younger patients showing more benefit independent of improvement in facial nerve function.     

Role of post-operative electroneuronography in predicting facial nerve recovery after acoustic neuroma removal: a pilot study

Complete clinical facial paralysis immediately after acoustic neuroma removal occurs in between 40 to 90 per cent of patients despite the fact that the facial nerve has been preserved anatomically. Some of these patients improve rapidly with adequate cosmetic and functional recovery. Others however, have incomplete or no return of useful function. A pilot study to assess the prognostic value of electroneuronography (ENOG) in 14 patients following acoustic neuroma removal was performed. The results suggest that post operative ENOG is of value in dividing those patients with anatomically intact facial nerves yet complete clinical paralysis post-operatively into groups: one with rapid improvement to an acceptable functional and cosmetic result and one with prolonged paralysis with incomplete or no recovery. Electroneuronography may thus be used to predict the initial recovery profile in patients with complete facial paralysis after surgery.     

Causes of facial nerve paresis after translabyrinthine surgery for acoustic neuroma.

Forty-six consecutive video-recorded translabyrinthine operations at Gentofte Hospital, for tumors of 5 to 25 mm, were investigated for possible damage to the facial nerve from cauterization, suction, stretching, pushing, and other instrumental trauma at the following regions: fundus, internal meatus, porus, cerebellopontine angle, and brain stem. House-Brackmann grading of the postoperative facial nerve function was determined from the patient records for the 1st, 3rd, and 10th days and 3 months and 6 months postoperatively, as well as the final status. Suction on the nerve seems to be the most important factor for perioperative facial nerve damage. The most common site of damage was the porus region. This investigation shows thermic drilling lesions to be very relevant. There was no correlation between the degree and character of damage and the postoperative facial nerve function. In eight patients we cannot explain the postoperative facial palsy.     

听神经瘤患者术前面神经及耳蜗神经显影技术

听神经瘤是最常见的桥小脑角良性肿瘤,手术可引起面瘫、听力下降等并发症,术前定位面神经、耳蜗神经可降低其发生率。本文对近年来发展的颅内神经显影技术做一综述,主要集中于听神经瘤患者的面神经、耳蜗神经定位手段。     

Early rehabilitation of facial nerve deficit after acoustic neuroma surgery

OBJECTIVE: To determine whether an early physical rehabilitative program could improve and/or accelerate recovery from a postoperative deficit of facial nerve (FN) function. MATERIAL AND METHODS: A retrospective study of the charts of patients who presented a postoperative FN deficit after surgery for acoustic neuroma (AN) was carried out. Twenty-nine patients were enrolled and divided into 2 groups: 18 who underwent early physical rehabilitation and 11 who did not undergo rehabilitation. All the AN patients underwent translabyrinthine removal and were classified preoperatively according to the House-Brackmann staging system. Physical rehabilitation was performed according to Kabat (i.e. neuromuscular facilitation). FN function was assessed postoperatively and classified according to the House-Brackmann grading system. RESULTS: In Grade IV and V patients, early rehabilitation allowed a faster and better recovery with respect to AN patients for whom rehabilitation was not carried out. CONCLUSION: Early physical rehabilitation has proved to be effective as a helpful tool for recovery from FN deficit and it is therefore advisable to use it soon after surgery, especially for FN deficits worse than Grade IV.     

大型听神经瘤的显微手术技巧及面神经保护

目的探讨大型听神经瘤的显微手术技巧、效果及术中面神经的保护。方法回顾性分析解放军总医院耳鼻咽喉头颈外科2010年1月~2010年12月收治的采用显微外科手术治疗30例大型听神经瘤患者的临床资料。其中男性18例,女性12例;年龄19～71岁,平均39.6±4.2岁;病程3个月～2年。主要临床表现为桥小脑角综合征和颅内压增高征,首发症状表现为耳鸣、听力下降12例,头痛、恶心、呕吐10例,行走不稳4例,面部麻木7例,三叉神经痛2例,面瘫6例。30例术中均行面神经监测,显微镜下切除肿瘤,术毕刺激面神经的脑干端对术后面神经功能进行预测。结果本组30例大型听神经瘤全切除28例,次全切除1例,部分切除1例。术中面神经完整保留29例(96.67%),无死亡病例。肿瘤切除后,面神经刺激阈值的大小与术后面神经功能存在明显的相关性。刺激阈值越小,术后面神经功能越好。结论熟练地采用显微外科技术选择合适的手术入路可明显提高肿瘤的全切除率和面神经的解剖及功能保留率。手术入路的正确选择,娴熟的显微外科操作技术,术中应用面神经监测技术,能有效地保护桥小脑角周围的重要结构及面神经功能,并可预测术后面神经功能。     

Facial nerve outcome in acoustic neuroma surgery.

Patients consider facial paralysis the most concerning sequelae following acoustic tumor resection. Surgical and anesthetic refinements have lowered operative mortality to allow the surgeon to focus on preserving facial nerve function. Tumor size, microsurgical technique, and intraoperative monitoring are the most important factors that define the risk of postoperative facial paralysis. A protocol for uniform surgical reporting is proposed.     

Long-term prognosis of profound facial nerve paralysis secondary to acoustic neuroma resection

The long-term prognosis of profound facial nerve paralysis was reviewed in 107 patients who, despite preserved nerve continuity, showed no facial movement after acoustic neuroma resection. Spontaneous recovery occurred in 77 patients. However, there was no apparent recovery in 30 patients. Twenty-two of these patients underwent hypoglossal-facial nerve anastomosis 7-33 months after tumor resection. When spontaneous recovery occurred, the first sign of remission was observed between 3 and 4 months after surgery in nearly half of the patients. Such a sign did not appear after 12 months. The recovery of facial movement deteriorated depending on how long remission onset was delayed. However, the quality of facial movement in patients with such delayed remission was still identical or better than that in those after hypoglossal-facial nerve anastomosis. These results showed that hypoglossal-facial nerve anastomosis should be performed approximately 1 year after tumor resection if no sign of remission has been observed by then.     

Preoperative appearance of facial muscles on magnetic resonance predicts final facial function after acoustic neuroma surgery.

OBJECTIVE: Several previous studies have shown that muscle appearance on magnetic resonance is a sensitive indicator of muscle denervation. Previous attempts at determining preoperative indicators of final facial function after acoustic neuroma removal has been mostly unsuccessful. The goal of this study was to determine if the appearance of the facial muscles on preoperative imaging is predictive of final facial function after surgical removal of vestibular schwannomas. STUDY DESIGN: We conducted a retrospective chart and magnetic resonance review. SETTING: This study was conducted at a tertiary referral center. PATIENTS: We included all patients who underwent vestibular schwannoma removal between January 1, 1997, and December 31, 2001, with available preoperative magnetic resonance images and a minimum of 12 months follow up. INTERVENTIONS: We used translabyrinthine, middle fossa, and suboccipital approaches for tumor removal. A neuroradiologist, blinded to preoperative or final facial function after tumor removal, retrospectively reviewed preoperative magnetic resonance images. MAIN OUTCOMES MEASURES: Facial muscles were evaluated on magnetic resonance and classified as symmetric or asymmetric. Facial function was graded using the House-Brackmann scale. Preoperative facial function was noted on the preoperative physical examination. Final function was determined at least 12 months postoperatively. RESULTS: A total of 247 patients underwent tumor removal during the study period. One hundred thirty-two patients had adequate preoperative magnetic resonance images. Patients with preoperative facial muscle asymmetry seen on preoperative magnetic resonance indicating muscle atrophy had significantly worse final facial function, regardless of tumor size. CONCLUSION: The preoperative appearance of facial muscles provides valuable insight into the physiology of the facial nerve in the presence of vestibular schwannomas. Patients with pre-operative facial muscle symmetry have significantly better facial function than those with atrophy.     

大型听神经瘤肌电图监护与术后面神经功能的相关性研究

目的　研究面肌肌电图与大型听神经瘤术后面神经功能预后的关系 ,探讨可以预测术后面神经功能的面肌肌电图的定量指标。方法　对 32例大型听神经瘤在面肌肌电图监护下行显微手术切除 ,测定面神经脑干端与内听道端刺激阈值 ,计算其比值 ,并对比值与术后的面神经功能进行相关分析。结果　 2 9例于面神经的脑干端和内听道端刺激后均引出动作电位 ,脑干端的刺激阈值为 (3.6 4± 5 .80 )mA(0 .5～ 31.5 0mA) ,内听道端刺激阈值为 (3.0 0± 5 .11)mA(0 .4～ 2 8.0 0mA) ,脑干端刺激阈值与内听道端刺激阈值的比值为 :1.2 4± 0 .16 (1.0 0～1.6 0 ) ;用Spearman相关分析表明 ,脑干端刺激阈值与内听道端刺激阈值与术后 1d、3d、1周、3个月、6个月和 1年的面神经功能无相关性 (P >0 .0 5 ) ,而脑干端刺激阈值与内听道端刺激阈值的比值与术后 6个月和 1年的面神经功能呈正相关 (r =0 .5 2 1,P =0 .0 18;r =0 .6 14 ,P =0 .0 0 4 )。结论　面肌EMG术中监护可以帮助术者早期辨认和确定大型听神经瘤面神经的走行方向 ,肿瘤切除后确认面神经结构是否完整 ,脑干端刺激阈值与内听道端刺激阈值的比值可以预测面神经功能的预后。     

Electroneurography: preoperative facial nerve assessment in acoustic neuroma surgery: a preliminary study

Preservation of facial nerve function during acoustic tumor resection is an important goal. Patients with acoustic tumors who present with facial weakness may be at increased risk of postoperative facial paralysis. Subclinical tumor involvement of the facial nerve may be more frequent than is commonly recognized. A preliminary study was undertaken to assess the incidence of subclinical involvement of the facial nerve and to discern if such involvement had prognostic implications. Preoperative facial electroneurography (ENoG) was performed in thirteen patients undergoing surgical resection of acoustic tumors. Three of thirteen patients demonstrated preoperative facial weakness and ENoG was abnormal in all three of these patients. Of the ten patients with normal facial function preoperatively, eight revealed amplitude reduction on ENoG testing. Further study is required to discern the prognostic value of preoperative ENoG abnormalities.     

Continuous intraoperative facial nerve monitoring in predicting postoperative injury during parotidectomy

OBJECTIVES/HYPOTHESIS: To assess whether the use of continuous intraoperative facial nerve monitoring correlates to postoperative facial nerve injury during parotidectomy. STUDY DESIGN: A retrospective analysis. METHODS: Forty-five consecutive parotidectomies were performed using an electromyograph (EMG)-based intraoperative facial nerve monitor. Of those, 37 had complete data for analysis. Intraoperative findings and final interpretation of the EMGs were analyzed by a senior neurologist and neurophysiologist. All patients were analyzed, including those with preoperative weakness and facial nerve sacrifice. RESULTS: The overall incidence of facial paralysis (House-Brackmann scale > 1) was 43% for temporary and 22% for permanent deficits. This includes an 11% incidence of preoperative weakness and 14% with intraoperative sacrifice. An abnormal EMG occurred in only 16% of cases and was not significantly associated with permanent or temporary facial nerve paralysis (chi, P < 1.0; Fisher's exact P < .68). Of the eight patients with permanent paralysis, only two had abnormalities on the facial nerve monitor. Also, only one of five patients with intraoperative sacrifice of the facial nerve had an abnormal EMG. Factors significantly associated with the incidence of facial paralysis include malignancy, advanced age, extent of parotidectomy, and dissection beyond the parotid gland (chi and Fisher's, P < .05). CONCLUSIONS: The results suggest that abnormalities on the intraoperative continuous facial nerve monitor during parotidectomy do not predict facial nerve injury. The incidence of permanent and temporary facial nerve paralysis compare favorably with the literature given that this study includes patients with revision surgery, intraoperative sacrifice, and preoperative paralysis. Standard of care implications will be discussed.