Vestibular Schwannoma Cerebellopontine Angle Position Impacts Facial Outcome.

OBJECTIVES/HYPOTHESIS: To determine the impact of vestibular schwannoma (VS) position relative to the internal auditory canal (IAC) on postoperative facial nerve function and extent of surgical resection. STUDY DESIGN: Retrospective chart review. METHODS: Retrospective review of patients undergoing resection of large (≥25 mm) VSs. Outcome measures included early (≤1 month) facial function, long-term (≥1 year) facial function and extent of resection. Tumor measurements included the greatest dimension, dimension anterior to the IAC axis, dimension posterior to the IAC axis, and a ratio of posterior-to-anterior dimension (PA ratio). RESULTS: A total of 127 patients met inclusion criteria. In early follow-up, 60% patients had good (House-Brackmann I-II), and 40% patients had poor (House-Brackmann III-VI) facial function. In long-term follow-up, 71% patients had good, and 29% patients had poor facial function. A total of 72% of patients underwent gross total resection (GTR) of their tumors. Patients with good facial function had significantly larger PA ratios than patients with poor function both early and long term; however, greatest dimension was the more clearly significant independent predictor of facial outcomes. A larger PA ratio was observed in patients in whom GTR was achieved, but this association was potentially confounded by surgeon preferences and was not statistically significant after controlling for surgical site. CONCLUSIONS: This study demonstrates that VS position relative to the IAC axis can be used along with tumor size to predict postoperative facial outcomes. A greater proportion of tumor posterior to the IAC axis was associated with significantly better facial outcomes. LEVEL OF EVIDENCE: 4 Laryngoscope, 132:1093-1098, 2022.

Delayed Facial Palsy After Resection of Vestibular Schwannoma: An Analysis of Long-term Facial Nerve Outcomes.

OBJECTIVES: 1) Identify clinical factors associated with delayed facial palsy (DFP) after microsurgical resection of vestibular schwannoma. 2) Determine whether DFP predicts worse facial nerve (FN) outcomes. METHODS: Adult patients (≥18 yrs) who underwent vestibular schwannoma resection between February 2008 and December 2017 were retrospectively reviewed. Postoperative House-Brackmann (HB) FN function was assessed on the day of surgery, daily during patients' inpatient admissions, and at postoperative clinic visits. Follow-up exceeded ≥12 months for all patients. DFP was defined as a decline (≥1 HB grade) in FN function (relative to the preoperative state) occurring between postoperative days 1 and 30. RESULTS: Two hundred ninety-one patients were analyzed. Mean age was 51.5 years (±12.3) and mean tumor size 20.6 mm (±10.8). Immediate FP occurred in 61 (21%) patients, and DFP occurred in 112 (38%) patients. Tumor size was largest in patients with immediate FP (p < 0.0001). On univariate analysis, DFP was associated with better final FN outcomes (OR 0.447, p = 0.0101) compared with immediate FP. Multivariate analysis, however, showed that timing of FP was no longer significant, whereas larger tumor size and preoperative HB2 function predicted worse FN outcomes (OR 2.718, p < 0.0001 and OR 9.196, p = 0.0039, respectively). In patients with DFP, longer time to onset of palsy predicted more favorable FN outcomes. CONCLUSIONS: When accounting for tumor size, the timing of onset of postoperative facial palsy does not predict final FN outcomes. In patients who develop DFP, the longer the interval between surgery and onset of weakness, the better the chances of good long-term FN function.

Preoperative Sudden Hearing Loss May Predict Hearing Preservation After Retrosigmoid Resection of Vestibular Schwannoma.

OBJECTIVES: Describe the effect of preoperative sudden hearing loss (SHL) on likelihood of hearing preservation (HP) after surgical resection of vestibular schwannoma (VS). STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS: Adult patients (≥18 years) who underwent retrosigmoid VS resection for HP between February 2008 and December 2018 were reviewed. All patients had preoperative word recognition score (WRS) of at least 50%. Similarly, HP was defined as postoperative WRS of more than or equal to 50%. Regression analysis was used to describe the effect of SHL on HP, accounting for tumor size, and preoperative hearing quality. INTERVENTIONS: All patients underwent retrosigmoid VS resection for HP. MAIN OUTCOME MEASURES: WRS of at least 50%. RESULTS: Of 160 patients who underwent retrosigmoid VS resection during the study period, 153 met inclusion criteria. Mean tumor size was 14.0 (±6) mm. Hearing was preserved in 41.8% (n = 64). Forty patients (26.1%) had a history of preoperative SHL. Among 138 patients (90.2%) in whom the cochlear nerve was anatomically preserved during surgery, HP was achieved in 61.8% of those with SHL (21 of 34) and 41.3% of those without SHL (43 of 104) (p = 0.0480). On univariate and multivariate analysis (accounting for tumor size and preoperative hearing quality), SHL was a significant positive predictor of HP (odds ratio 2.292, p = 0.0407 and odds ratio 2.778, p = 0.0032, respectively). CONCLUSION: In patients with VS and retained serviceable hearing, SHL is an independent predictor of HP after retrosigmoid microsurgical resection when the cochlear nerve is preserved.

Preoperative Radiographic Predictors of Hearing Preservation After Retrosigmoid Resection of Vestibular Schwannomas.

OBJECTIVE: To identify preoperative radiographic predictors of hearing preservation (HP) after retrosigmoid resection of vestibular schwannomas (VSs). STUDY DESIGN: Retrospective case series with chart review. SETTING: Tertiary skull base referral center. METHODS: Adult patients with VSs <3 cm and word recognition scores (WRSs) ≥50% who underwent retrosigmoid resection and attempted HP between February 2008 and December 2018 were identified. Pure tone average (PTA), WRS, and magnetic resonance imaging radiographic data, including tumor diameter and dimensional extension relative to the internal auditory canal (IAC), were examined. RESULTS: A total of 151 patients were included. The average tumor size was 13.8 mm (range, 3-28). Hearing was preserved in 41.7% (n = 63). HP rates were higher for intracanalicular tumors than tumors with cerebellopontine angle (CPA) components (57.6% vs 29.4%, P = .03). On multivariate analysis, maximal tumor diameter (odds ratio [OR], 0.892; P < .001) and preoperative PTA (OR, 0.974; P = .026) predicted HP, while mediolateral tumor diameter predicted postoperative PTA (OR, 1.21; P = .005) and WRS (OR, -1.89; P < .001). For tumors extending into the CPA, younger age (OR, 0.913; P = .012), better preoperative PTA (OR, 0.935; P = .049), smaller posterior tumor extension (OR, 0.862; P = .001), and smaller caudal extension relative to the IAC (OR, 0.844; P = .001) all predicted HP. CONCLUSION: Rates of HP are highest in patients with small intracanalicular VSs and good preoperative hearing. For tumors extending into the CPA, greater posterior and caudal tumor extension relative to the IAC may portend worse hearing outcomes.

Predicting Long-Term Facial Nerve Outcomes After Resection of Vestibular Schwannoma.

OBJECTIVES: 1) Describe the effect of tumor size on facial nerve (FN) outcomes after microsurgical resection of vestibular schwannoma (VS).2) Describe the effect of surgical approach, preoperative radiation, and early postoperative facial function on long-term FN outcomes. STUDY DESIGN: Retrospective analysis. SETTING: Tertiary referral center. PATIENTS: Adult (≥18 yr) patients underwent translabyrinthine or retrosigmoid VS resection by a single neurotologist and single neurosurgeon between February 2008 and December 2017. MAIN OUTCOME MEASURES: Long-term FN outcomes (≥12 mo) according to House-Brackmann (HB) grade. RESULTS: During the study period, 350 patients underwent VS resection, of whom 290 met inclusion criteria. Translabyrinthine surgery was performed in 54% (n = 158) and retrosigmoid in 45% (n = 131). One patient underwent a combined approach. Among patients who underwent retrosigmoid approach, none had a tumor more than 30 mm. Gross total resection was achieved in 98% (n = 283). Long-term HB1-2 function was achieved in 90% (n = 261). On univariate analysis, tumor size (per cm increase), history of preoperative radiation, and worse HB score at discharge predicted worse FN function. Multivariate analysis showed that tumor size (per cm increase) and history of radiation were independent predictors of FN function. For patients with tumors less than 30 mm, multivariate analysis of tumor size and surgical approach was performed; tumor size remained predictive of worse FN function (odds ratio [OR] 2.362, p = 0.0035), whereas surgical approach was not significantly predictive (p = 0.7569). CONCLUSION: Tumor size and history of radiation predict long-term FN function after VS resection. When accounting for tumor size, the translabyrinthine and retrosigmoid approaches yield equivalent FN results.

The Effect of Tumor Size on Likelihood of Hearing Preservation After Retrosigmoid Vestibular Schwannoma Resection.

OBJECTIVES: 1) Describe the effect of tumor size on the likelihood of hearing preservation after retrosigmoid approach for resection of vestibular schwannoma (VS).2) Describe the effect of preoperative hearing status on the likelihood of hearing preservation. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS: Adult (18 years or older) patients underwent retrosigmoid VS resection and postoperative audiometry between 2008 and 2018 and had a preoperative word recognition score (WRS) of at least 50%. Patients with a history of neurofibromatosis 2, radiation, or previous resection were excluded. INTERVENTIONS: All patients underwent retrosigmoid VS resection with attempted hearing preservation. MAIN OUTCOME MEASURES: WRS of at least 50%. RESULTS: Data from 153 patients were analyzed. Mean age was 50.8 (±11.3) years and mean tumor size 14 (±6) mm. Hearing was preserved and lost in 64 (41.8%) and 89 (58.2%) patients, respectively. Hearing preservation rates were higher for intrameatal tumors than for tumors with extrameatal extension (57.6% versus 29.4%, p = 0.0005). On univariate and multivariate regression analysis, tumor size (per mm increase) was a negative predictor of hearing preservation (odds ratio [OR] 0.893, p = 0.0002 and 0.841, p = 0.0005, respectively). Preoperative American Academy of Otolaryngology-Head & Neck Surgery Hearing Class was also predictive of hearing preservation (p = 0.0044). Class A hearing (compared with class B hearing) was the strongest positive risk factor for hearing preservation (OR 3.149, p = 0.0048 and 1.236, p = 0.0005, respectively). CONCLUSION: Small tumor size and preoperative class A hearing are positive predictors of hearing preservation in patients undergoing the retrosigmoid approach for VS resection.

Factors That Affect Length of Hospital Stay After Vestibular Schwannoma Surgery.

OBJECTIVE: To identify perioperative factors that influence hospital length of stay (LOS) after resection of vestibular schwannoma (VS). STUDY DESIGN: Retrospective case review. SETTING: Tertiary skull base referral center. PATIENTS: Patients who underwent acoustic neuroma resection between January 1, 2007 and January 1, 2014. INTERVENTIONS: Approaches used for VS resection included translabyrinthine and retrosigmoid. MAIN OUTCOME MEASURES: LOS and several perioperative factors that may delay hospital discharge were examined. Factors included were patient demographics (age and sex), tumor characteristics (size), surgical factors (operative time, approach, revision surgery, date of surgery), and immediate postoperative factors (presence of vertigo or immediate postoperative complications). RESULTS: Two hundred eighty-eight patients underwent VS resection during the study period. Two hundred fifty-five patients had complete charts available for review. LOS ranged from 1 to 10 days with an average of 2.66 days and mode of 2 days. One hundred thirty-one patients were admitted for ≤2 days and 124 patients stayed longer. Of the perioperative factors examined with univariate analysis, female gender (p = 0.0266) and presence of postoperative vertigo (p < 0.0001) were statistically significant factors associated with LOS >2 days. On multivariate logistic regression analysis with odds ratios (OR), older patient age (OR = 1.028, p = 0.0177), female gender (OR = 1.810, p = 0.0314), longer operative time (OR = 1.424, p = 0.0007), and presence of postoperative vertigo (OR = 4.904, p < 0.0001) carried a statistically significant increased odds toward a LOS >2 days. CONCLUSIONS: VS surgery and postoperative care can be carried out efficiently with a minimal LOS. Identifying factors that may prolong LOS may help the operative team anticipate and address needs to optimize LOS.

Long-term MRI surveillance after microsurgery for vestibular schwannoma.

OBJECTIVES: To determine the optimal postoperative magnetic resonance imaging (MRI) schedule and length of follow-up for patients undergoing microsurgical excision of vestibular schwannoma (VS). STUDY DESIGN: A retrospective review of patients who underwent microsurgical excision of VS at a single tertiary care center between January 1993 and March 2004. METHODS: Two hundred and twenty subjects were analyzed and characteristics gathered, including tumor size, surgical approach, completeness of resection, and length of follow-up to last MRI. All postoperative MRIs were reviewed. Radiologic progression is defined as a transition to a more advanced MRI grade from a less advanced MRI grade (eg, clean, linear, nodular) and was recorded for each of the subjects' serial MRIs. The MRI categorized findings were also binned into five time periods for summary analyses. Interval-censored survival analysis was performed to model time to recurrence across the population. RESULTS: Of the non-neurofibromatosis type 2 (NF2) cohort, the average tumor size at the time of resection was 1.98 ± 1.02 cm (range 0.4-5 cm); average length of follow-up was 9.0 ± 4.6 years (range 1-19); 102 subjects (47.2%) underwent a retrosigmoid resection; and 110 (50.9%) underwent a translabyrinthine resection. Eight of these subjects (4.1%) demonstrated radiologic progression; of those, four underwent additional treatment. Survival analysis showed early (1-2 years postoperative), middle (2-10 years postoperative), and late (> 10 years postoperative) radiologic progression events. CONCLUSION: The current recommended MRI surveillance schedule after microsurgery for VS includes MRIs at 1, 5, and 10 years postoperatively. Nonparametric survival analysis suggests that a majority of radiologic progression events occur in the first 10 years postoperatively. LEVEL OF EVIDENCE: 4. Laryngoscope, 127:2132-2138, 2017.

Facial nerve function after the extended translabyrinthine approach.

Objective To evaluate facial nerve function after excision of petroclival/anterior cerebellopontine angle (CPA) meningiomas by the extended translabyrinthine (EXTL) approach and compare these with outcomes after the transcochlear and transotic approaches. Design Retrospective chart review. Setting/Participants A search of archived surgical cases at a single institution between January 1, 1995, and January 1, 2012. Main Outcome Measures Facial function measured on the House-Brackmann (HB) scale. Results A total of 16 patients underwent the EXTL approach for primary excision of petroclival meningiomas. Average tumor size was 4.6 cm, and six patients had gross total resection. Average length of follow-up was 36.4 months. Two patients required reoperation for tumor regrowth. Preoperative facial function was HB I or II in all patients with available examinations. Immediate postoperative facial nerve function ranged from HB I to HB VI. In patients with an intact facial nerve at surgery, all but one had long-term facial function of HB I or II. A robust response on intraoperative facial nerve monitoring was prognostic of favorable long-term facial function. Facial function declined in some patients after postoperative radiation or revision surgery. Conclusions The EXTL approach allows excellent exposure of petroclival/anterior CPA lesions and should be favored to improve facial outcomes.

Hearing preservation and vestibular schwannoma: intracochlear FLAIR signal relates to hearing level.

OBJECTIVES: This study aimed to evaluate the relationship between cochlear signal on fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging (MRI) sequences and hearing in patients undergoing hearing preservation surgery for vestibular schwannoma (VS) and to demonstrate a new classification system to be used in imaging evaluation of patients with VS. METHODS: A search of archived surgical cases at a single institution between January 1, 2006, and January 1, 2012, revealed 51 patients who underwent hearing preservation surgery for VS. Tumor size, patient age and sex, and preoperative and postoperative pure-tone average (PTA) and speech discrimination score (SDS) were recorded. Cochleae on the affected side were examined on preoperative FLAIR sequences and classified as limited hyperintensity (LH) or extensive hyperintensity (EH). RESULTS: Mean patient age was 51 years, and mean tumor size was 1.3 cm. Preoperative FLAIR sequences were classified into LH (n = 36) and EH (n = 15) categories. Preoperative PTA and SDS were 29.5 dB (SD, 16.7), 90% (SD, 14) and 40.6 dB (SD, 13.8), 80% (SD, 25) for LH and EH, respectively. On univariate analysis, preoperative PTA was superior in the LH group (p = 0.04). There was a trend toward superior preoperative SDS and postoperative PTA in the LH group, but these differences were not statistically significant (p = 0.08 and p = 0.06, respectively). CONCLUSION: The current study is the first to demonstrate a distinct association between cochlear FLAIR signal and pretreatment hearing levels in patients with VS. A new classification system for evaluating cochlear FLAIR signal is proposed. Improvement in FLAIR sequences will allow further investigation of this association.

Hearing preservation in management of epidermoids of the cerebellopontine angle: CPA epidermoids and hearing preservation.

OBJECTIVES: Surgical approaches for epidermoid cysts of the cerebellopontine angle (CPA) are dictated by tumor location. Previous reports have advocated the sacrifice of usable hearing to achieve maximal tumor resection in a single operation. The aim of the current study is to demonstrate the applicability of hearing preservation approaches in the neurotologic management of epidermoids of the CPA. STUDY DESIGN: Retrospective chart review. METHODS: A search of archived surgical cases at a single institution between January 1, 1997, and December 31, 2011, revealed 18 cases of epidermoid cysts involving the CPA. RESULTS: Eighteen patients with a mean age 40.9 years underwent surgery. Average tumor size was 4.47 cm, and presenting symptoms included headache, vertigo, cranial neuropathies, and seizures. Thirteen patients underwent a retrosigmoid approach, 2 translabyrinthine, 2 pterional, and 1 retrolabyrinthine/presigmoid. Complications included CSF leak, pseudomeningocele, meningitis, cranial nerve dysfunction, and persistent imbalance. All but 5 patients had long-term follow-up imaging to chronicle tumor residua/recurrence, varying from 6 to 149 months postoperatively. The average length of follow-up was 71.4 months, and residual tumor was common, with most patients demonstrating a focal or small area of residual tumor on follow-up imaging. Two patients had undergone previous surgery for epidermoid excision elsewhere. Two patients required reoperation for epidermoid regrowth, and the times between surgeries were 44 and 78 months. Of the patients who underwent a retrosigmoid approach, 9 had postoperative audiograms. All of these patients maintained hearing at or near their preoperative level except for 2 patients whose hearing declined and one whose hearing significantly improved. CONCLUSION: Hearing preservation approaches for epidermoids of the CPA is a feasible option for long-term control of these tumors. Resection from a retrosigmoid approach can provide years of useful hearing, and the majority of patients do not require reoperation.

Impact of fundal extension on hearing after surgery for vestibular schwannomas.

OBJECTIVE: To compare hearing preservation after surgery for intracanalicular vestibular schwannomas with or without fundal extension. STUDY DESIGN: Retrospective chart review. PATIENTS: Patients with intracanalicular tumors (≤ 10-m maximal dimension) undergoing retrosigmoid craniotomy between 2001 and 2010. INTERVENTION: Preoperative and postoperative audiograms, preoperative magnetic resonance imaging, and operative reports were reviewed. MAIN OUTCOME MEASURES: Preoperative and postoperative hearing (American Academy of Otolaryngology-Head and Neck Surgery classification). RESULTS: Complete data for 53 patients (27 female and 24 male subjects, sex was not recorded for 2 patients) meeting selection criteria was available. Fundal involvement was identified in 39 (73.6%) of the 53 patients. The remaining 14 patients did not have tumor with fundal extension (26.4%). Average tumor size for patients with fundal extension (+FE) was 6.9 ± 2.2 mm and without fundal extension (-FE) was 8.2 ± 1.9 mm (p = 0.05, Student's t test). Average preoperative speech discrimination score for the entire study was 90.5 ± 11.8 (n = 53). After retrosigmoid approach for tumor resection, 79% of patients (42/53) had preserved hearing defined as American Academy of Otolaryngology-Head and Neck Surgery class A, B, or C. Average postoperative speech discrimination score for these patients was 89.3 ± 12.1, and average postoperative pure-tone average was 35.9 ± 9.1%. Eighty-five percent (33/39) of +FE patients had preserved hearing (class A, B, or C). In contrast, 64% (9/14) of -FE patients had hearing preserved (class A, B, or C; Fisher's exact test, p = 0.034). CONCLUSION: Hearing preservation rate after retrosigmoid craniotomy for intracanalicular vestibular schwannomas may be superior for tumors with fundal extension compared with tumors that do not extend to the fundus.

Comparison of growth patterns of acoustic neuromas with and without radiosurgery.

OBJECTIVE: To compare the natural history of acoustic neuroma growth to the reported growth rate of acoustic neuromas after radiosurgical therapy, a retrospective review and meta-analysis of the literature was performed. The retrospective review was of one hundred eleven patients (average age, 71 yr) who chose to have their acoustic neuromas managed conservatively in our institution. These patients underwent serial magnetic resonance imaging for assessment of tumor growth for an average period of 38 months. Growth patterns if these untreated tumors were compared to that of radiosurgically treated acoustic neuromas reported in the literature. DATA SOURCES: The English-language literature on the topic was searched systematically by Medline and Pubmed using the following key words: acoustic neuroma, vestibular schwannoma, conservative management, conservative treatment, nonsurgical, age, elderly, growth, observation, untreated, radio-surgery, gamma knife, 13 Gy and 12 Gy. There were no limits to the year of publication. STUDY SELECTION: Articles that fulfilled inclusion criteria (methods) were studied in detail. DATA EXTRACTION: All the articles described in the study selection were used in the review. CONCLUSION: The average growth rate of the untreated tumors was 0.7 +/- 1.4 mm/yr. Eighty-two percent grew less than 1 mm/yr, whereas 18% grew equal to or more than 1 mm/yr. Thirteen percent grew more than 2 mm/yr, with growth being noted at an average of 2.2 years after diagnosis. This represents an 87% control rate if tumor control rate is defined as less than 2-mm growth/yr. Meta-analysis indicates that tumor control rates range in the radiosurgical literature from 86% to 100%. The mean follow-up periods in the radiosurgical literature are generally not reported. Tumor control is not uniformly defined. Based on the results of this study, there is no discernable significant difference between growth patterns of untreated acoustic neuromas and those treated radiosurgically. To establish a significant difference, longer-term follow-up studies with larger sample sizes and tumor control rates are needed. Tumor control should be defined as zero growth.

Approach design and closure techniques to minimize cerebrospinal fluid leak after cerebellopontine angle tumor surgery.

OBJECTIVE: The purpose of the study was to identify specific aspects of surgical approach design and closure technique aimed at reducing the incidence of cerebrospinal fluid leak after cerebellopontine angle tumor surgery. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: All patients undergoing cerebellopontine angle tumor surgery at the study institution from January 1996 through September 2004. MAIN OUTCOME MEASURE: The presence or absence of cerebrospinal fluid leak after various surgical approaches for a wide variety of cerebellopontine angle tumors. RESULTS: Three hundred forty three patients underwent surgery for cerebellopontine angle tumors at the study institution during the study period. Tumor types in descending order of frequency were as follows: acoustic neuroma, 244; cerebellopontine angle meningiomas, 33; petroclival meningiomas, 32; foramen magnum meningiomas, 10; epidermoid tumors, 9; facial nerve tumors, 6; hemangiopericytomas, 3; schwannomas of glossopharyngeal/spinal accessory nerves, 3; and unusual internal auditory canal tumors, 3. Surgical approaches used for tumor resection included translabyrinthine, retrosigmoid, combined transpetrosal, far lateral/transcondylar, middle cranial fossa, and extended middle cranial fossa. During the nearly 8-year study period, four postoperative cerebrospinal fluid leaks were encountered, resulting in a leak rate of 1.2%. Two of these patients required surgical repair of their leaks; the other two stopped spontaneously. The authors describe specific aspects of approach design and closure that appear to have a positive impact on postoperative cerebrospinal fluid leak rates. CONCLUSION: Attention to specific aspects of surgical approach design and wound closure results in a reduced incidence of cerebrospinal fluid leak after surgery for cerebellopontine angle tumors.

A comparison of direct eighth nerve monitoring and auditory brainstem response in hearing preservation surgery for vestibular schwannoma.

OBJECTIVE: The objective of this study was to compare the effectiveness of direct eighth nerve monitoring (DENM) and auditory brainstem response (ABR) in facilitating hearing preservation during vestibular schwannoma resection. STUDY DESIGN: This was a retrospective study. SETTING: : Tertiary referral center. METHODS: We conducted a retrospective clinical study of the use of ABR and DENM during vestibular schwannoma removal. Tumors were removed through a retrosigmoid craniotomy. The rate of hearing preservation between the two monitoring modalities was compared. The additional outcome measures of facial nerve function and cerebral spinal fluid leak rate were also evaluated. RESULTS: Hearing preservation was attempted in 77 patients with vestibular schwannomas. Tumor sizes ranged from 0.5 cm to 2.5 cm. Hearing was preserved in 71% of patients with tumors 1 cm or less and in 32% of patients with tumors between 1 and 2.5 cm when direct eighth nerve monitoring was used. Hearing preservation rates with ABR for tumors 1 cm or less were 41% and 10% in patients with tumors between 1 and 2.5 cm (p=0.03) Facial nerve preservations rates were 94% (House-Brackmann 1-2) for tumors less than 2 cm. CONCLUSIONS: DENM provides significantly higher rates of hearing preservation during vestibular schwannoma resection when compared with ABR.