Hearing preservation in acoustic neurinoma surgery

Intraoperative neurophysiology monitoring utilization in the USA during the period 2006-2022

OBJECTIVE

To describe the secular trends in utilization of intraoperative neurophysiology monitoring (IONM).

METHODS

Retrospective descriptive study of a large claims database of privately-insured patients in the USA during the period 2006-2022.

RESULTS

Among 3917 cerebellopontine angle tumor resections in 3779 patients [median (p25-p75) age: 49 (38-56) years, 59 % females], 910 (23.2 %) had both brainstem auditory evoked potentials (BAEP) and cranial nerve monitoring. Among 36,392 carotid endarterectomies in 33,017 patients [60 (56-62) years, 40 % females], 1676 (4.6 %) had both electroencephalogram (EEG) and somatosensory evoked potentials (SSEP) monitoring. Among 26,131 spinal fusion surgeries in 24,741 patients [15 (13-23) years, 68 % females], 9080 (34.8 %) had SSEP, motor evoked potentials (MEP), and electromyogram (EMG) monitoring. Among 5193 tethered cord release surgeries in 4976 patients [8 (2-17) years, 59 % females], 324 (6.2 %) had SSEP, MEP, EMG, and sphincter EMG monitoring. Among 5105 thoracoabdominal aortic repair surgeries in 4764 patients [58 (50-62) years, 26 % female], 187 (3.7 %) had both SSEP and MEP monitoring. On multivariable analysis, factors associated with receiving intraoperative neurophysiology monitoring included recency of surgery, urban residence, employment type, and certain USA regions. The proportion of surgeries with IONM tended to increase over the period 2006-2022.

CONCLUSION

Only a minority of surgeries in which IONM is indicated had IONM. The proportion of surgeries with IONM tended to increase in 2006-2022.

Intraoperative Neurophysiological Monitoring in Neurosurgery

Intraoperative neurophysiological monitoring (IONM) is a crucial advancement in neurosurgery, enhancing procedural safety and precision. This technique involves continuous real-time assessment of neurophysiological signals, aiding surgeons in timely interventions to protect neural structures. In addition to inherent limitations, IONM necessitates a detailed anesthetic plan for accurate signal recording. Given the growing importance of IONM in neurosurgery, we conducted a narrative review including the most relevant studies about the modalities and their application in different fields of neurosurgery. In particular, this review provides insights for all physicians and healthcare professionals unfamiliar with IONM, elucidating commonly used techniques in neurosurgery. In particular, it discusses the roles of IONM in various neurosurgical settings such as tumoral brain resection, neurovascular surgery, epilepsy surgery, spinal surgery, and peripheral nerve surgery. Furthermore, it offers an overview of the anesthesiologic strategies and limitations of techniques essential for the effective implementation of IONM.

Prognostic Factors for Hearing Preservation Surgery in Small Vestibular Schwannoma

OBJECTIVE

to evaluate recent contributions to the literature on prognostic factors of hearing preservation in small vestibular schwannoma microsurgery.

METHODS

review of the most recent studies.

RESULTS

factors such as tumor size, preoperative hearing status, tumor growth rate, tumor origin, surgical approach, radiological characteristics, results of preoperative neurophysiological tests, preoperative symptoms and demographic features have been investigated and some of them reported to be significant in the prediction of hearing preservation.

CONCLUSIONS

tumor size and preoperative hearing status are the most impactful factors and play a key role in patient selection for hearing preservation surgery. Other features such as fundal extension, tumor origin and impaired ABR could have prognostic value on hearing preservation. Tumor growth rate, preoperative impedance, cVEMPs and age have also recently been found to be significant, but more studies are needed. The role of preoperative tinnitus, vertigo and gender is lacking and controversial, whereas the differences between available surgical approaches have been smoothed out in recent years.

The Validity of the Koos Classification System With Respect to Facial Nerve Function

BACKGROUND

The Koos classification of vestibular schwannomas is designed to stratify tumors based on extrameatal extension and compression of the brainstem. Our prior study demonstrated excellent reliability. No study has yet assessed its validity.

OBJECTIVE

To present a retrospective study designed to assess the validity of the Koos grading system with respect to facial nerve function following treatment of 81 acoustic schwannomas.

METHODS

We collected data retrospectively from 81 patients with acoustic schwannomas of various Koos grades who were treated with microsurgical resection or stereotactic radiosurgery. House-Brackmann (HB) scores were used to assess facial nerve function and obtained at various time points following treatment. We generated Spearman's rho and Kendall's tau correlation coefficients along with a logistic regression curve.

RESULTS

We found no significant difference in the presence or absence of facial dysfunction by Koos classification when looking at all patients. There was a positive but fairly weak correlation between HB score and Koos classification, which was only significant at the first postoperative clinic appointment. There was a statistically significant difference in the presence or absence of facial dysfunction between patients treated with surgery vs radiation, which we expected. We found no statistically significant difference when comparing surgical approaches. Logistic regression modeling demonstrated a poor ability of the Koos grading system to predict facial nerve dysfunction following treatment.

CONCLUSION

The Koos grading system did not predict the presence of absence of facial nerve dysfunction in our study population. There were trends within subgroups that require further exploration.

Hearing Preservation Outcomes and Prognostic Factors in Acoustic Neuroma Surgery: Predicting Cutoffs

OBJECTIVE

To investigate the outcomes of hearing preservation surgery (HPS) for acoustic neuroma and quantify tumor and patient characteristics predictive of hearing preservation after surgery.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary referral center.

PATIENTS

A total of 100 consecutive patients diagnosed with acoustic neuroma from 2000 to 2012.

INTERVENTION

Hearing preservation surgery through microscopic retrosigmoid approach combined with a retrolabyrinthine meatotomy.

MAIN OUTCOME MEASURE

Pre- and postoperative hearing stratified according to the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) and the Tokyo classifications. The most accurate cutoff was identified for each tumor and patients' variable affecting the outcome by calculating the Youden index. A multivariable analysis was undertaken at these cutoffs to identify prognostic factors for hearing preservation.

RESULTS

Preoperative hearing class was preserved after surgery in 31% (AAO-HNS), and 39% (Tokyo classification) of patients. According to the AAO-HNS classification, the tumor size in the cerebello-pontine angle, pure-tone average (PTA), and speech discrimination score cutoffs for predicting good postoperative hearing function were 7 mm, 21 dB, and 90%, respectively. With the Tokyo classification, only the PTA cutoff differed, with 27 dB. On multivariable analysis, tumor size and PTA were independent prognostic factors for postoperative hearing with high model's goodness of fit (area under the curve  = 0.784; 95% CI = 0.68-0.88 and area under the curve  = 0.813; 95% CI = 0.72-0.90), according to both the hearing classifications.

CONCLUSIONS

The estimated cutoffs for tumor size and PTA were independently associated with HPS. These factors should be prospectively investigated before they are adopted as selection criteria for HPS.

Congress of Neurological Surgeons Systematic Review and Evidence-Based Guidelines on Hearing Preservation Outcomes in Patients With Sporadic Vestibular Schwannomas

Question 1

What is the overall probability of maintaining serviceable hearing following stereotactic radiosurgery utilizing modern dose planning, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled that there is moderately high probability (>50%-75%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 2

Among patients with AAO-HNS (American Academy of Otolaryngology-Head and Neck Surgery hearing classification) class A or GR (Gardner-Robertson hearing classification) grade I hearing at baseline, what is the overall probability of maintaining serviceable hearing following stereotactic radiosurgery, utilizing modern dose planning, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled that there is a high probability (>75%-100%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 3

What patient- and tumor-related factors influence progression to nonserviceable hearing following stereotactic radiosurgery using ≤13 Gy to the tumor margin?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled regarding the probability of successful hearing preservation based on the following prognostic data: the most consistent prognostic features associated with maintenance of serviceable hearing are good preoperative word recognition and/or pure tone thresholds with variable cut-points reported, smaller tumor size, marginal tumor dose ≤12 Gy, and cochlear dose ≤4 Gy. Age and sex are not strong predictors of hearing preservation outcome.

Question 4

What is the overall probability of maintaining serviceable hearing following microsurgical resection of small to medium-sized sporadic vestibular schwannomas early after surgery, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering microsurgical resection should be counseled that there is a moderately low probability (>25%-50%) of hearing preservation immediately following surgery, moderately low probability (>25%-50%) of hearing preservation at 2 yr, moderately low probability (>25%-50%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 5

Among patients with AAO-HNS class A or GR grade I hearing at baseline, what is the overall probability of maintaining serviceable hearing following microsurgical resection of small to medium-sized sporadic vestibular schwannomas early after surgery, at 2, 5, and 10 yr following treatment?

Recommendation

Level 3: Individuals who meet these criteria and are considering microsurgical resection should be counseled that there is a moderately high probability (>50%-75%) of hearing preservation immediately following surgery, moderately high probability (>50%-75%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 6

What patient- and tumor-related factors influence progression to nonserviceable hearing following microsurgical resection of small to medium-sized sporadic vestibular schwannomas?

Recommendation

Level 3: Individuals who meet these criteria and are considering microsurgical resection should be counseled regarding the probability of successful hearing preservation based on the following prognostic data: the most consistent prognostic features associated with maintenance of serviceable hearing are good preoperative word recognition and/or pure tone thresholds with variable cut-points reported, smaller tumor size commonly less than 1 cm, and presence of a distal internal auditory canal cerebrospinal fluid fundal cap. Age and sex are not strong predictors of hearing preservation outcome.

Question 7

What is the overall probability of maintaining serviceable hearing with conservative observation of vestibular schwannomas at 2, 5, and 10 yr following diagnosis?

Recommendation

Level 3: Individuals who meet these criteria and are considering observation should be counseled that there is a high probability (>75%-100%) of hearing preservation at 2 yr, moderately high probability (>50%-75%) of hearing preservation at 5 yr, and moderately low probability (>25%-50%) of hearing preservation at 10 yr.

Question 8

Among patients with AAO-HNS class A or GR grade I hearing at baseline, what is the overall probability of maintaining serviceable hearing with conservative observation at 2 and 5 yr following diagnosis?

Recommendation

Level 3: Individuals who meet these criteria and are considering stereotactic radiosurgery should be counseled that there is a high probability (>75%-100%) of hearing preservation at 2 yr, and moderately high probability (>50%-75%) of hearing preservation at 5 yr. Insufficient data were available to determine the probability of hearing preservation at 10 yr for this population subset.

Question 9

What patient and tumor-related factors influence progression to nonserviceable hearing during conservative observation?

Recommendation

Level 3: Individuals who meet these criteria and are considering observation should be counseled regarding probability of successful hearing preservation based on the following prognostic data: the most consistent prognostic features associated with maintenance of serviceable hearing are good preoperative word recognition and/or pure tone thresholds with variable cut-points reported, as well as nongrowth of the tumor. Tumor size at the time of diagnosis, age, and sex do not predict future development of nonserviceable hearing during observation.  The full guideline can be found at: https://www.cns.org/guidelines/guidelines-manage-ment-patients-vestibular-schwannoma/chapter_3.

Koos Classification of Vestibular Schwannomas: A Reliability Study

BACKGROUND

The Koos classification of vestibular schwannomas is designed to stratify tumors based on extrameatal extension and compression of the brainstem. While this classification system is widely reported in the literature, to date no study has assessed its reliability.

OBJECTIVE

To assess the intra- and inter-rater reliability of the Koos classification system.

METHODS

After institutional review board approval was obtained, a cross-sectional group of the Magnetic Resonance imagings of 40 patients with vestibular schwannomas varying in size comprised the study sample. Four raters were selected to assign a Koos grade to 50 total scans. Inter- and intrarater reliability were calculated and reported using Fleiss’ kappa, Kendall's W, and Intraclass correlation coefficient (ICC).

RESULTS

Inter-rater reliability was found to be substantial when measured using Fleiss' kappa (.71), extremely strong using Kendall's W (.92), and excellent as calculated by ICC (.88).

Intrarater reliability was perfect for 3 out of 4 raters as assessed using weighted kappa, Kendall's W and ICC, with the intrarater agreement for the fourth rater measured as extremely high.

CONCLUSION

We have demonstrated that the Koos classification system for vestibular schwannoma is a reliable method for tumor classification. This study lends further support to the results of current literature using Koos grading system. Further studies are required to evaluate its validity and utility in counseling patients with regard to outcomes.

The Changing Paradigm for the Surgical Treatment of Large Vestibular Schwannomas

Objective  Planned subtotal resection followed by Gamma Knife surgery (GKS) in patients with large vestibular schwannoma (VS) has emerged during the past decade, with the aim of a better functional outcome for facial and cochlear function. Methods  We prospectively collected patient data, surgical, and dosimetric parameters of a consecutive series of patients treated by this method at Lausanne University Hospital during the past 8 years. Results  A consecutive series of 47 patients were treated between July 2010 and January 2018. The mean follow-up after surgery was 37.5 months (median: 36, range: 0.5-96). Mean presurgical tumor volume was 11.8 mL (1.47-34.9). Postoperative status showed normal facial nerve function (House-Brackmann I) in all patients. In a subgroup of 28 patients, with serviceable hearing before surgery and in which cochlear nerve preservation was attempted at surgery, 26 (92.8%) retained serviceable hearing. Nineteen had good or excellent hearing (Gardner-Robertson class 1) before surgery, and 16 (84.2%) retained it after surgery. Mean duration between surgery and GKS was 6 months (median: 5, range: 3-13.9). Mean residual volume as compared with the preoperative one at GKS was 31%. Mean marginal dose was 12 Gy (11-12). Mean follow-up after GKS was 34.4 months (6-84). Conclusion  Our data show excellent results in large VS management with a combined approach of microsurgical subtotal resection and GKS on the residual tumor, with regard to the functional outcome and tumor control. Longer term follow-up is necessary to fully evaluate this approach, especially regarding tumor control.

Systematic review and meta-analysis of the technique of subtotal resection and stereotactic radiosurgery for large vestibular schwannomas: a “nerve-centered” approach

OBJECTIVE

During the last decade, the primary objective for large vestibular schwannoma (VS) management has progressively shifted, from tumor excision to nerve preservation by using a combined microsurgical and radiosurgical approach. The aim of this study was to provide a systematic review and meta-analysis of the available literature regarding the combined strategy of subtotal resection (STR) followed by stereotactic radiosurgery (SRS) for large VSs.

METHODS

The authors performed a systematic review and meta-analysis in compliance with the PRISMA guidelines for article identification and inclusion using the PubMed, Embase, and Cochrane databases. Established inclusion criteria were used to screen all identified relevant articles published before September 2017 without backward date limit.

RESULTS

The authors included 9 studies (248 patients). With a weighted mean follow-up of 46 months (range 28–68.8 months), the pooled rate of overall tumor control was 93.9% (95% CI 91.0%–96.8%). Salvage treatment (second STR and/or SRS) was necessary in only 13 (5.24%) of 18 patients who experienced initial treatment failure. According to the House-Brackmann (HB) grading scale, functional facial nerve preservation (HB grade I–II) was achieved in 96.1% of patients (95% CI 93.7%–98.5%). Serviceable hearing after the combined approach was preserved in 59.9% (95% CI 36.5%–83.2%).

CONCLUSIONS

A combined approach of STR followed by SRS was shown to have excellent clinical and functional outcomes while still achieving a tumor control rate comparable to that obtained with a total resection. Longer-term follow-up and larger patient cohorts are necessary to fully evaluate the rate of tumor control achieved with this approach.

Preserving normal facial nerve function and improving hearing outcome in large vestibular schwannomas with a combined approach: planned subtotal resection followed by gamma knife radiosurgery

Objective

To perform planned subtotal resection followed by gamma knife surgery (GKRS) in a series of patients with large vestibular schwannoma (VS), aiming at an optimal functional outcome for facial and cochlear nerves.

Methods

Patient characteristics, surgical and dosimetric features, and outcome were collected prospectively at the time of treatment and during the follow-up.

Results

A consecutive series of 32 patients was treated between July 2010 and June 2016. Mean follow-up after surgery was 29 months (median 24, range 4–78). Mean presurgical tumor volume was 12.5 cm³ (range 1.47–34.9). Postoperative status showed normal facial nerve function (House–Brackmann I) in all patients. In a subgroup of 17 patients with serviceable hearing before surgery and in which cochlear nerve preservation was attempted at surgery, 16 (94.1%) retained serviceable hearing. Among them, 13 had normal hearing (Gardner–Robertson class 1) before surgery, and 10 (76.9%) retained normal hearing after surgery. Mean duration between surgery and GKRS was 6.3 months (range 3.8–13.9). Mean tumor volume at GKRS was 3.5 cm³ (range 0.5–12.8), corresponding to mean residual volume of 29.4% (range 6–46.7) of the preoperative volume. Mean marginal dose was 12 Gy (range 11–12). Mean follow-up after GKRS was 24 months (range 3–60). Following GKRS, there were no new neurological deficits, with facial and hearing functions remaining identical to those after surgery in all patients. Three patients presented with continuous growth after GKRS, were considered failures, and benefited from the same combined approach a second time.

Conclusion

Our data suggest that large VS management, with planned subtotal resection followed by GKRS, might yield an excellent clinical outcome, allowing the normal facial nerve and a high level of cochlear nerve functions to be retained. Our functional results with this approach in large VS are comparable with those obtained with GKRS alone in small- and medium-sized VS. Longer term follow-up is necessary to fully evaluate this approach, especially regarding tumor control.

Hearing preservation in acoustic neuroma resection: Analysis of petrous bone measurement and intraoperative application

Background:

There is an increased risk for labyrinthine injury for the resection of acoustic neuromas (AN) on the suboccipital, retrosigmoid approach. Prognostic factors should be analyzed for the postoperative hearing function.

Methods:

We examined 51 patients with ANs using preoperative intact hearing function. Audiological data were obtained by pure tone audiogram (PTA) and speech audiogram. The preoperative and postoperative anatomical localization of the labyrinth was measured with specific distances regarding the tumor and corresponding anatomy of the posterior fossa by high-resolution magnetic resonance imaging (MRI).

Results:

Postoperative MRI controls confirmed no injuries to the labyrinth (0%). The postoperative hearing results showed 100% hearing preservation for T1-tumors (<1 ml/<1.1 cm), 50% for T2-tumors (1–4 ml/1.1–1.8 cm), 40% for T3-tumors (4–8 ml/1.8–2.3 cm) and 18% for T4-tumors (>8 ml/>2.3 cm). Postoperative deafness was seen in all cases with ventral tumor extension higher than 5.5 mm. Postoperative loss of hearing was seen in all cases with hearing preservation with 6–8% of speech discrimination and an increase in the hearing threshold of 12 dB in the PTA compared to the preoperative hearing status.

Conclusion:

Petrous bone measurement by high-resolution MRI data enables safe surgical exposure of the internal acoustic canal with avoidance of injury to the labyrinth and a better postoperative prognosis, especially for intrameatal ANs and for the resection of intrameatal portions of larger neuromas. The prognostic factors enable the patients and the surgeon a better estimation of postoperative results regarding deafness and postoperative hypacusis and support a consolidated treatment planning.

Hearing Preservation Surgery in Vestibular Schwannoma: The Hidden Truth

To compare the results of hearing preservation surgeries using different approaches — the enlarged middle cranial fossa approach and the retrosigmoid approach — and different classification systems, stressing the importance of preserving “normal hearing,” we performed a retrospective case review in a tertiary care medical center. The charts of 107 patients with vestibular schwannoma who underwent tumor resection were reviewed. Hearing preservation was reported according to 2 different classification systems: the modified Sanna classification and the classification of the American Academy of Otolaryngology—Head and Neck Surgery. The facial nerve results were graded according to the House-Brackmann scale. The hearing preservation rates differed markedly depending on the classification used. We conclude that hearing preservation in acoustic neuroma is a more difficult proposition than most surgeons appreciate, especially in terms of serviceable hearing.

Clinical and Radiographic Factors Predicting Hearing Preservation Rates in Large Vestibular Schwannomas

Objectives Postoperative hearing preservation rates for patients with large vestibular schwannomas range from 0 to 43%. The clinical and radiographic factors predicting hearing preservation in smaller vestibular schwannomas are well described; however, their importance in larger tumors is unclear. We investigated factors predicting hearing preservation in large vestibular schwannomas. Design Retrospective review. Setting Quaternary care academic center. Participants A total of 85 patients with unilateral vestibular schwannomas > 3 cm underwent retrosigmoid resections. Main Outcomes Measures Preoperative and postoperative serviceable hearing rates. Methods Clinical and radiographic data including preoperative and postoperative audiograms, preoperative symptoms, magnetic resonance imaging features, and postoperative facial weakness were analyzed. Results Hearing was preserved in 41% of patients (17 of 42) with preoperative serviceable hearing. Hypertension and diabetes increased the likelihood of preoperative hearing loss. Preoperative tinnitus predicted a lower likelihood of hearing preservation. No radiographic factors predicted hearing preservation; however, larger tumor size, smaller fourth ventricular width, and the presence of a cerebrospinal fluid cleft surrounding the tumor predicted postoperative facial weakness. Conclusion Systemic comorbidities may influence hearing loss preoperatively in patients with large vestibular schwannomas. The absence of tinnitus may reflect hearing reserve and propensity for hearing preservation. Preoperative radiographic features did not predict hearing preservation despite some associations with postoperative facial weakness.

Microsurgery versus stereotactic radiation for small vestibular schwannomas: a meta-analysis of patients with more than 5 years' follow-up

OBJECTIVE

To compare the long-term outcome of hearing and tumor outcome of small vestibular schwannomas treated with stereotactic radiation and microsurgery.

DATA SOURCES

A thorough search for English-language publications and "in process" articles dating from 1948 to December 2011 was conducted using Ovid MEDLINE.

STUDY SELECTION

The principal criteria were patients having had microsurgery or radiation therapy as their sole treatment, with a follow-up of at least 5 years, and a useful hearing level at diagnosis.

DATA EXTRACTION

Sixteen studies met our criteria. Hearing preservation outcome (worse or preserved) and tumor outcome (failure, control) data, as well as all other significant observations, were collected from the articles. Stereotactic radiation was the only radiation therapy analyzed.

DATA SYNTHESIS

The Pearson χ test was our primary statistical analysis.

CONCLUSION

Stereotactic radiation showed significantly better long-term hearing preservation outcome rates than microsurgery (p < 0.001). However, long-term tumor outcome was not significantly different in stereotactic radiation as compared with microsurgery (p = 0.122). Although stereotactic radiation demonstrates a more favorable long-term hearing preservation outcome as compared with microsurgery, additional studies are required to provide the medical field with a better understanding of vestibular schwannoma treatment.

The impact of comorbidities, regional trends, and hospital factors on discharge dispositions and hospital costs after acoustic neuroma microsurgery: a United States nationwide inpatient data sample study (2005-2009)

OBJECT

Hospitalization cost and patient outcome after acoustic neuroma surgery depend on several factors. There is a paucity of data regarding the relationship between demographic features such as age, sex, race, insurance status, and patient outcome. Apart from demographic factors, there are several hospital-related factors and regional issues that can affect outcomes and hospital costs. To the authors' knowledge, no study has investigated the issue of regional disparity across the country in terms of cost of hospitalization and discharge disposition.

METHODS

The authors analyzed the Nationwide Inpatient Sample (NIS) database over the years 2005-2009. Several variables were analyzed from the database, including patient demographics, comorbidities, and surgical complications. Hospital variables, such as bedsize, rural/urban location, teaching status, federal or private ownership, and the region, were also examined. Patient outcome and increased hospitalization costs were the dependent variables studied.

RESULTS

A total of 2589 admissions from 242 hospitals were analyzed from the NIS data over the years 2005-2009. The mean age was 48.99 ± 13.861 years (± SD), and 304 (11.7%) of the patients were older than 65 years. The cumulative cost incurred by the hospitals from 2005 to 2009 was $948.77 million. The mean expenditure per admission was $76,365.09 ± $58,039.93. The mean total charges per admission rose from $59,633.00 in 2005 to $97,370.00 in 2009. The factors that predicted most significantly with other than routine (OTR) disposition outcome were age older than 65 years (OR 2.22, 95% CI 1.411-3.518; p < 0.001), aspiration pneumonia (OR 16.085, 95% CI 4.974-52.016; p < 0.001), and meningitis (OR 11.299, 95% CI 3.126-40.840; p < 0.001). When compared with patients with Medicare and Medicaid, patients with private insurance had a protective effect against OTR disposition outcome. Higher comorbidities predicted independently for OTR disposition outcome (OR 1.409, 95% CI 1.072-1.852; p = 0.014). The West region predicted negatively for OTR disposition outcome. Large hospitals were independently associated with higher hospital charges (OR 4.269, 95% CI 3.106-5.867; p < 0.001). The West region had significantly higher (p < 0.001) mean hospital charges than the other regions. Patient factors such as meningitis and aspiration pneumonia were strong independent predictors of increased hospital charges (p < 0.001). Higher comorbidities (OR 1.297, 95% CI 1.036-1.624; p = 0.023) and presence of neurofibromatosis Type 2 (OR 2.341, 95% CI 1.479-3.707; p < 0.001) were associated with higher hospital charges.

CONCLUSIONS

The authors' study shows that several factors can affect patient outcome and hospital charges for patients who have undergone acoustic neuroma surgery. Factors such as younger age, higher ZIP code income, less comorbidity, private insurance, elective surgery, and the West region predicted for better disposition outcome. However, the West region, higher comorbidities, and weekend admissions were associated with higher hospitalization costs.

Intraoperative neuromonitoring techniques in the surgical management of acoustic neuromas

Unfavorable outcomes such as facial paralysis and deafness were once unfortunate probable complications following resection of acoustic neuromas. However, the implementation of intraoperative neuromonitoring during acoustic neuroma surgery has demonstrated placing more emphasis on quality of life and preserving neurological function. A modern review demonstrates a great degree of recent success in this regard. In facial nerve monitoring, the use of modern electromyography along with improvements in microneurosurgery has significantly improved preservation. Recent studies have evaluated the use of video monitoring as an adjunctive tool to further improve outcomes for patients undergoing surgery. Vestibulocochlear nerve monitoring has also been extensively studied, with the most popular techniques including brainstem auditory evoked potential monitoring, electrocochleography, and direct compound nerve action potential monitoring. Among them, direct recording remains the most promising and preferred monitoring method for functional acoustic preservation. However, when compared with postoperative facial nerve function, the hearing preservation is only maintained at a lower rate. Here, the authors analyze the major intraoperative neuromonitoring techniques available for acoustic neuroma resection.

Hearing preservation: microsurgery

PURPOSE OF REVIEW

To evaluate the recent and significant contributions to the literature that examine hearing preservation outcomes and prognostic factors in vestibular schwannoma microsurgery.

RECENT FINDINGS

Hearing preservation rates overall range considerably between 2 and 93% in recent studies. There are a number of factors that have been reported to be significant in the prediction of hearing preservation. Characteristics such as approach, results of preoperative neurophysiological testing, tumor size and nerve of origin have long been reported. A more recent contribution to the literature has included the association between MRI T2 signal in the fundus of the internal auditory canal and hearing preservation. This review provides a summary of some of the landmark studies in conjunction with more recent work detailing the prognostic factors for hearing preservation in the surgical management of vestibular schwannoma.

SUMMARY

Hearing preservation in vestibular schwannoma surgery has undergone tremendous evolution over the past 50 years. In this review, we outline the prognostic factors that predict hearing preservation and describe recent contributions.

Evaluation of variation in the course of the facial nerve, nerve adhesion to tumors, and postoperative facial palsy in acoustic neuroma

Objective To investigate the variation in the course of the facial nerve (FN) in patients undergoing acoustic neuroma (AN) surgery, its adhesion to tumors, and the relationship between such adhesions and postoperative facial palsy. Methods The subjects were 356 patients who underwent AN surgery in whom the course of the FN could be confirmed. Patients were classified into six groups: ventro-central surface of the tumor (VCe), ventro-rostral (VR), ventro-caudal (VCa), rostral (R), caudal (C), and dorsal (D). Results The FN course was VCe in 185 cases, VR in 137, VCa in 19, R in 10, C in 4, and D in one. For tumors < 1.5 cm, VCe was most common. For tumors ≥ 1.5 cm, the proportion of VR increased. No significant difference was observed between the course patterns of the FN in terms of postoperative FN function, but for tumors > 3.0 cm, there was an increasing tendency for the FN to adhere strongly to the tumor capsule, and postoperative facial palsy was more severe in patients with stronger adhesions. Conclusions The VCe pattern was most common for small tumors. Strong or less strong adhesion to the tumor capsule was most strongly associated with postoperative FN palsy.

Surgery for vestibular schwannomas: a systematic review of complications by approach

Object

Various studies report outcomes of vestibular schwannoma (VS) surgery, but few studies have compared outcomes across the various approaches. The authors conducted a systematic review of the available data on VS surgery, comparing the different approaches and their associated complications.

Methods

MEDLINE searches were conducted to collect studies that reported information on patients undergoing VS surgery. The authors set inclusion criteria for such studies, including the availability of follow-up data for at least 3 months, inclusion of preoperative and postoperative audiometric data, intraoperative monitoring, and reporting of results using established and standardized metrics. Data were collected on hearing loss, facial nerve dysfunction, persistent postoperative headache, CSF leak, operative mortality, residual tumor, tumor recurrence, cranial nerve (CN) dysfunction involving nerves other than CN VII or VIII, and other neurological complications. The authors reviewed data from 35 studies pertaining to 5064 patients who had undergone VS surgery.

Results

The analyses for hearing loss and facial nerve dysfunction were stratified into the following tumor categories: intracanalicular (IC), size (extrameatal diameter) < 1.5 cm, size 1.5–3.0 cm, and size > 3.0 cm. The middle cranial fossa approach was found to be superior to the retrosigmoid approach for hearing preservation in patients with tumors < 1.5 cm (hearing loss in 43.6% vs 64.3%, p < 0.001). All other size categories showed no significant difference between middle cranial fossa and retrosigmoid approaches with respect to hearing loss. The retrosigmoid approach was associated with significantly less facial nerve dysfunction in patients with IC tumors than the middle cranial fossa method was; however, neither differed significantly from the translabyrinthine corridor (4%, 16.7%, 0%, respectively, p < 0.001). The middle cranial fossa approach differed significantly from the translabyrinthine approach for patients with tumors < 1.5 cm, whereas neither differed from the retrosigmoid approach (3.3%, 11.5%, and 7.2%, respectively, p = 0.001). The retrosigmoid approach involved less facial nerve dysfunction than the middle cranial fossa or translabyrinthine approaches for tumors 1.5–3.0 cm (6.1%, 17.3%, and 15.8%, respectively; p < 0.001). The retrosigmoid approach was also superior to the translabyrinthine approach for tumors > 3.0 cm (30.2% vs 42.5%, respectively, p < 0.001). Postoperative headache was significantly more likely after the retrosigmoid approach than after the translabyrinthine approach, but neither differed significantly from the middle cranial fossa approach (17.3%, 0%, and 8%, respectively; p < 0.001). The incidence of CSF leak was significantly greater after the retrosigmoid approach than after either the middle cranial fossa or translabyrinthine approaches (10.3%, 5.3%, 7.1%; p = 0.001). The incidences of residual tumor, mortality, major non-CN complications, residual tumor, tumor recurrence, and dysfunction of other cranial nerves were not significantly different across the approaches.

Conclusions

The middle cranial fossa approach seems safest for hearing preservation in patients with smaller tumors. Based on the data, the retrosigmoid approach seems to be the most versatile corridor for facial nerve preservation for most tumor sizes, but it is associated with a higher risk of postoperative pain and CSF fistula. The translabyrinthine approach is associated with complete hearing loss but may be useful for patients with large tumors and poor preoperative hearing.

Dorsal location of the cochlear nerve on vestibular schwannoma: preoperative evaluation, frequency, and functional outcome

The cochlear nerve is most commonly located on the caudoventral portion of the capsule of vestibular schwannomas and rarely on the dorsal portion. In such a condition, total removal of the tumor without cochlear nerve dysfunction is extremely difficult. The purpose of our study was to identify the frequency of this anatomical condition and the status of postoperative cochlear nerve function; we also discuss the preoperative radiological findings. The study involved 114 patients with unilateral vestibular schwannomas operated on via a retrosigmoid (lateral suboccipital) approach. Locations of the cochlear nerve on the tumor capsule were ventral, dorsal, caudal, and rostral. Ventral and dorsal locations were further subdivided into rostral, middle, and caudal third of the tumor capsule. The postoperative cochlear nerve function and preoperative magnetic resonance (MR) findings were reviewed retrospectively. In 56 patients that had useful preoperative hearing, useful hearing was retained in 50.0% (28 of 56) of patients after surgery. The cochlear nerve was located on the dorsal portion of the tumor capsule in four patients (3.5%), and useful hearing was preserved in only one of these patients (25%) in whom the tumor had been partially resected. This tumor-nerve anatomical relationship was identified in all tumors of <2 cm at preoperative MR cisternography. MR cisternography has the potential to identify the tumor-nerve anatomical relationship, especially in small-sized tumors that usually require therapeutic intervention that ensures hearing preservation. Hence, careful evaluation of the preoperative MR cisternography is important in deciding the therapeutic indications.

Use of piezosurgery for internal auditory canal drilling in acoustic neuroma surgery

BACKGROUND

Piezosurgery is based on microvibrations generated by the piezoelectrical effect and has a selective bone-cutting ability with preservation of soft tissue. This study examined the applicability of Piezosurgery compared to rotating drills (RD) for internal auditory canal (IAC) opening in acoustic neuroma (AN) surgery.

MATERIALS AND METHODS

Piezosurgery was used in eight patients for IAC drilling in AN surgery. After exposition of the IAC and tumor, the posterior wall of the IAC was drilled using Piezosurgery instead of RD. Piezosurgery was evaluated with respect to practicability, safety, preciseness of bone cutting, preservation of cranial nerves, influences on neurophysiological monitoring, and facial nerve and hearing outcome.

RESULTS

Piezosurgery was successfully used for selective bone cutting, while cranial nerves were structurally and functionally preserved, which could be measured by means of neuromonitoring. Piezosurgery guaranteed a safe and precise cut by removing bone layer by layer in a shaping way. Compared to RD, limited influence on neurophysiological monitoring attributable to Piezosurgery was noted, allowing for continuous neuromonitoring. No disadvantage due to microvibrations was noticed concerning hearing function. The angled tip showed better handling in right-sided than in left-sided tumors in the hands of a right-handed surgeon. The short, thick handpiece may be improved for more convenient handling.

CONCLUSION

Piezosurgery is a safe tool for selective bone cutting for opening of the IAC with preservation of facial nerve and hearing function in AN surgery. Piezosurgery has the potential to replace RD for this indication because of its safe and precise bone-cutting properties.

Management of large vestibular schwannoma. Part I. Planned subtotal resection followed by Gamma Knife surgery: radiological and clinical aspects

OBJECT

In large vestibular schwannoma (VS), microsurgery is the main treatment option, and complete resection is considered the primary goal. However, previous studies have documented suboptimal facial nerve outcomes in patients who undergo complete resection of large VSs. Subtotal resection is likely to reduce the risk of facial nerve injury but increases the risk of lesion regrowth. Gamma Knife surgery (GKS) can be performed to achieve long-term growth control of residual VS after incomplete resection. In this study the authors report on the results in patients treated using planned subtotal resection followed by GKS with special attention to volumetric growth, control rate, and symptoms.

METHODS

Fifty consecutive patients who underwent the combined treatment strategy of subtotal microsurgical removal and GKS for large VSs between 2002 and 2009 were retrospectively analyzed. Patients with neurofibromatosis Type 2 were excluded. Patient charts were reviewed for clinical symptoms. Audiograms were evaluated to classify hearing pre- and postoperatively. Preoperative and follow-up contrast-enhanced T1-weighted MR images were analyzed using volume-measuring software.

RESULTS

Surgery was performed via a translabyrinthine (25 patients) or retrosigmoid (25 patients) approach. The median follow-up was 33.8 months. Clinical control was achieved in 92% of the cases and radiological control in 90%. One year after radiosurgery, facial nerve function was good (House-Brackmann Grade I or II) in 94% of the patients. One of the two patients who underwent surgery to preserve hearing maintained serviceable hearing after resection followed by GKS.

CONCLUSIONS

Considering the good tumor growth control and facial nerve function preservation as well as the possibility of preserving serviceable hearing and the low number of complications, subtotal resection followed by GKS can be the treatment option of choice for large VSs.

Management of large vestibular schwannoma. Part II. Primary Gamma Knife surgery: radiological and clinical aspects

OBJECT

In large vestibular schwannomas (VSs), microsurgery is the main treatment option. A wait-and-scan policy or radiosurgery are generally not recommended given concerns of further lesion growth or increased mass effect due to transient swelling. Note, however, that some patients do not present with symptomatic mass effect or may still have serviceable hearing. Moreover, others may be old, suffer from severe comorbidity, or refuse any surgery. In this study the authors report the results in patients with large, growing VSs primarily treated with Gamma Knife surgery (GKS), with special attention to volumetric growth, control rate, and symptoms.

METHODS

The authors retrospectively analyzed 33 consecutive patients who underwent GKS for large, growing VSs, which were defined as > 6 cm(3) and at least indenting the brainstem. Patients with neurofibromatosis Type 2 were excluded from analysis, as were patients who had undergone previous treatment. Volume measurements were performed on contrast-enhanced T1-weighted MR images at the time of GKS and during follow-up. Medical charts were analyzed for clinical symptoms.

RESULTS

Radiological growth control was achieved in 88% of cases, clinical control (that is, no need for further treatment) in 79% of cases. The median follow-up was 30 months, and the mean VS volume was 8.8 cm(3) (range 6.1-17.7 cm(3)). No major complications occurred, although ventriculoperitoneal shunts were placed in 2 patients. The preservation of serviceable hearing and facial and trigeminal nerve function was achieved in 58%, 91%, and 86% of patients, respectively, with any facial and trigeminal neuropathy being transient. In 92% of the patients presenting with trigeminal hypesthesia before GKS, the condition resolved during follow-up. No patient- or VS-related feature was correlated with growth.

CONCLUSIONS

Primary GKS for large VSs leads to acceptable radiological growth rates and clinical control rates, with the chance of hearing preservation. Although a higher incidence of clinical control failure and postradiosurgical morbidity is noted, as compared with that for smaller VSs, primary radiosurgery is suitable for a selected group of patients. The absence of symptomatology due to mass effect on the brainstem or cerebellum is essential, as are close clinical and radiological follow-ups, because there is little reserve for growth or swelling.

Issues in the optimal selection of a cranial nerve monitoring system

Intraoperative nerve monitoring (IONM) is a safe technique that is of clear clinical value in the preservation of cranial nerves in skull base surgery and is rapidly becoming the standard of care. Available nerve monitoring systems vary widely in capabilities and costs. A well-informed surgeon may best decide on monitoring needs based on surgical case selection, experience, operating room space, availability of monitoring personnel, and cost. Key system characteristics that should be reviewed in the decision-making process include the monitoring technique (electromyography, pressure transducer, direct nerve monitoring, brainstem auditory evoked potential) and the stimulus technique (stimulating parameters, probe selection). In the past, IONM has been primarily employed in posterior fossa and temporal bone surgery, but the value of IONM is being recognized in more skull base and head and neck surgeries. Suggested IONM strategies for specific surgeries are presented.

Factors influencing hearing preservation in acoustic tumor surgery

In patients who underwent neurosurgery for excision of acoustic tumors, we used correlation and multivariate logistic regression analysis to study relationships among nine variables thought to have value in predicting hearing preservation. These variables included auditory perceptual, auditory neurophysiologic, and imaging-related characteristics of acoustic tumor dimensions. The univariate correlations showed two general trends. The first trend demonstrated relationships among imaging-related acoustic tumor dimensions (size or porus acousticus widening) with either postoperative hearing or brainstem auditory evoked potential (BAEP) abnormalities (tumor size and postoperative hearing; porus acousticus widening and postoperative hearing; tumor size and preoperative BAEP abnormalities). The second trend reflected interrelationships among preoperative audiometric variables that were not related to postoperative hearing outcome. Logistic regression analysis of eight independent variables on the presence or absence of postoperative hearing found that porus acousticus widening was the best prognostic indicator for hearing outcome. When the porus acousticus was widened, the odds ratio was 11:1 that hearing would be lost postoperatively. Viewed as a whole, the literature on prognostic variables related to hearing preservation has been limited, almost entirely, to univariate relationships. To determine more accurately which preoperative variables have unique prognostic value, more complex multivariate, analysis procedures will be required. Additionally, standardized criteria for assessment and reporting of auditory test results are also needed.

Continuous retrograde monitoring of the facial nerve: preliminary experience during acoustic neuroma surgery

Continuous electromyographical (EMG) monitoring of the facial nerve is widely used during acoustic tumor surgery. Mechanical stimulation of the facial nerve is capable of eliciting synchronous and asynchronous EMG responses alerting the surgeon to damaging maneuvers performed on the nerve. Mechanical stimulation, however, elicits EMG responses only when the nerve has been injured by the underlying pathology or previous surgical maneuvers, and the technique is sensitive to administration of muscular blockers. In addition, EMG is unable to furnish quantitative information about the damage. The present paper illustrates an alternative technique for intraoperative facial nerve monitoring, that is, the recording of facial nerve antidromic potentials (FNAPs).Eleven subjects operated on by acoustic neuroma surgery via a retrosigmoid approach (tumor sizes ranging from 12 to 28 mm) participated in the investigation. Bipolar electrical stimulation of the marginalis mandibulae was performed to elicit FNAPs. Stimulus intensity ranged from 2 to 6 mA with a delivery rate of 7/second. A silver-wire electrode positioned on the proximal portion of the acoustic-facial bundle was used to record action potentials. Changes in latency and amplitude of FNAPs were analyzed as a function of the main surgical steps. FNAP monitoring provided quantitative real-time information about damaging maneuvers performed on the nerve and allowed prediction of postoperative facial function.

Iatrogenic impairment of hearing during surgery for acoustic neuroma

Isolated or combined labyrinthine, neural, and vascular damage account for failure to preserve hearing during removal of acoustic neuromas. However, the specific mechanisms of auditory impairment remain unclear unless surgical maneuvers can be related to peri- and postoperative hearing on the basis of intraoperative monitoring of auditory function.Among the different auditory monitoring techniques, recording of cochlear nerve action potentials (CNAPs) from the intracranial portion of the nerve has proven particularly useful for identifying the mechanisms of iatrogenic auditory injury.The present investigation analyzes intra- and postoperative auditory impairment in relation to surgical steps in a group of 38 subjects with acoustic neuroma (size ranging from 5 to 24 mm) undergoing removal via a retrosigmoid approach.Coagulation close to the cochlear nerve, drilling of the internal auditory canal, and removal of the intrameatal portion of the acoustic neuroma have prove to be the most critical surgical steps in hearing preservation.Changes were correlated with intra- and extrameatal tumor size, the relationship between the internal auditory canal and vestibule, and internal auditory canal enlargement, anatomic involvement of the cochlear nerve, preoperative auditory level, and ABR and ENG test findings.Changes in CNAP morphology and latency are detailed, and mechanisms of injury are analyzed and discussed as a function of these variables.

Hearing preservation after microsurgical resection of large vestibular schwannomas

BACKGROUND

Hearing, which is often still clinically useful at presentation even with larger tumors, is a major determinant of quality of life in vestibular schwannoma (VS) patients.

OBJECTIVE

To present the hearing preservation rate after surgery in patients with large (>or=3 cm) VSs and identify clinical or radiologic predictors of hearing preservation.

METHODS

From April 2003 to March 2009, 192 patients underwent resection of a VS, including 46 large (>or=3 cm) tumors, of whom 28 had serviceable hearing preoperatively. Six of 28 patients (21.4%) had preserved hearing postoperatively.

RESULTS

Mean tumor diameter was 3.6 cm (range, 3.0-5.0 cm) and tumor volume was 17.2 mL (range, 6.9-45.2 mL). For patients with grade A Sanna-Fukushima hearing, the hearing preservation rate was 4 of 11 (36.4%). Complete resection was achieved in 6 of 6 cases with hearing preservation (41/47 for all patients). Six of 6 patients with preserved hearing had a cerebrospinal fluid cleft in the internal auditory canal (IAC) compared with 9 of 16 patients without preoperative hearing and 9 of 20 for patients with serviceable hearing that was lost postoperatively (P=.045). Six of 6 patients with preserved hearing had less than 35% of the tumor anterior to the longitudinal axis of the IAC compared with 13 of 20 in the serviceable hearing that was lost group (P=.036).

CONCLUSION

Our series demonstrates hearing preservation is possible for patients with large VSs and should be attempted in all patients with preoperative hearing. The quality of preoperative hearing, a cerebrospinal fluid cleft at the apex of the IAC, and a smaller proportion of tumor anterior to the IAC were positively associated with hearing preservation.

Preservation of facial nerve function after resection of vestibular schwannoma

OBJECTIVE

Most data regarding facial nerve function in patients undergoing microsurgical resection of vestibular schwannomas predominantly include series performed at a single institution. In an effort to minimise individual surgeon or institutional bias, we performed an analysis of the published literature on facial nerve outcomes following microsurgical resection of vestibular schwannomas. The objective of this study was to provide a comprehensive assessment of reported outcomes for facial nerve preservation after VS surgery.

MATERIALS AND METHODS

We identified a total of 296 studies involving over 25,000 patients that included outcome data for facial nerve function of vestibular schwannoma patients treated surgically. Data regarding surgical approach, tumour size, patient age, and use of intra-operative monitoring were extracted and correlated with facial nerve function after surgery. Patients with preoperative facial nerve dysfunction (House-Brackmann score 3 or higher) were excluded and 'facial nerve preservation' was defined as grade I or II House-Brackmann function at last follow-up visit.

RESULTS

A total of 79 articles reporting on 11,873 patients met our inclusion criteria contributing to our analysis. Patients treated with the middle cranial fossa approach had a trend towards higher overall facial nerve preservation rate (85%), compared to the translabyrinthine approach (81%, p = 0.07) , and did statistically better than the retrosigmoid approach (78%, p < 0.0001). Patients with an average tumour size <20 mm had significantly improved facial nerve preservation rates, compared to larger tumours (90% vs. 67%, p < 0.0001). Patients under 65 years of age had a lower facial nerve preservation rate (71% vs. 84%, p < 0.001). Finally, the use of intra-operative monitoring improved the facial nerve preservation rate (76% vs. 71%, p < 0.001).

CONCLUSION

Factors that appear to be associated with facial nerve preservation after microsurgical resection of a vestibular schwannoma include tumour size <20 mm, use of the middle fossa approach and use of neuromonitoring during surgery. These data provide a summary assessment of the published literature regarding facial nerve preservation after microsurgical resection of vestibular schwannoma.

Microsurgical excisions of vestibular schwannomas: A tumor-size-based analysis of neurological outcomes and surgical complications

INTRODUCTION

Vestibular schwannomas (VS) are benign tumors originating from Schwann cells in vestibulocochlear nerve. This study aimed at evaluating outcomes of microsurgical resections of VS based on tumor sizes in a South Asian country.

METHODS

The chart notes of 71 patients who underwent microsurgical resections of VS at a single academic center over a 20-year period (1990-2009) were reviewed, and relevant information was extracted. For analyzing outcomes, patients were divided into two groups based on tumor size at initial presentation: (1) Group A (tumor size ≤ 4 cm) and (2) Group B (tumor size > 4 cm). Pearson's chi-square and Fisher's exact tests were used for comparison of proportions; the independent sample t-test was used for comparison of means.

RESULTS

The average tumor diameter was 4.1 ± 1.5 (range, 1-6.6) cm. Complete resection was achieved more frequently in patients in Group A (P < 0.001). Duration of hospital stay and cost of treatment were significantly higher in Group B patients (P < 0.003 and P < 0.04, respectively). The severity of postoperative facial nerve injury, assessed by House-Brackmann grading system, was significantly higher in Group B (P < 0.01). Cerebrospinal fluid (CSF) leak and lower cranial nerve deficits also occurred more frequently after resection in Group B (P = 0.031 and P = 0.003, respectively).

CONCLUSION

We conclude that advanced stage tumors suggestive of delayed presentation are fairly common in Pakistan, and limit curative resection in the majority of patients. Postoperative morbidity is significantly higher in patients with tumor size > 4 cm.

Critical Assessment of Operative Approaches for Hearing Preservation in Small Acoustic Neuroma Surgery

BACKGROUND

For hearing preservation in acoustic neuroma (AN) surgery, the middle fossa (MF) or retrosigmoid (RS) approach can be used. Recent literature advocates the use of the MF approach, especially for small ANs.

OBJECTIVE

To present our critical analysis of operative results comparing these 2 approaches.

METHODS

We reviewed 504 consecutive AN resections performed between November 1998 and September 2007 and identified 43 MF and 82 RS approaches for tumors smaller than 1.5 cm during hearing preservation surgery. Individual cases were examined postoperatively with respect to hearing ability, facial nerve activity, operative time, blood loss, and symptoms resulting from retraction of the cerebellar or temporal lobes.

RESULTS

Good hearing function (American Academy of Otolaryngology-Head and Neck Surgery class B or better) was preserved in 76.7% of patients undergoing surgery via the MF approach and in 73.2% of the RS group (P = .9024). Temporary facial nerve weakness was more frequent in the MF group (P = .0249). However, late (8–12 months) follow-up examinations showed good recovery in both groups. The mean operative time was 7.45 hours for the MF group and 5.2 hours for the RS group (P = .0318). The mean blood loss was 280.5 mL for the MF group and 80.8 mL for the RS group (P &lt; .0001). Temporary symptoms of temporal lobe edema (drowsiness or speech disturbance) were noted in 6 MF cases. No cerebellar dysfunction was noted in the RS group.

CONCLUSIONS

Although hearing and facial nerve function assessed at approximately 1 year was similar with these 2 approaches, the RS approach provided several advantages over the MF approach for ANs smaller than 1.5 cm.

Trends in the management of vestibular schwannomas at Johns Hopkins 1997-2007

OBJECTIVES/HYPOTHESIS

To assess trends in the management of unilateral vestibular schwannomas over an 11-year period and to identify disease- and provider-related influences.

STUDY DESIGN

Retrospective chart review.

METHODS

Subjects presented to the Department of Otolaryngology-Head and Neck Surgery and the Department of Neurosurgery for management of unilateral vestibular schwannoma from 1997 through 2007, with at least two visits within the first year of presentation. The proportion of patients for whom initial management consisted of observation, surgical resection, or radiation therapy was determined, and the relative influence of study year, patient age, hearing status, and tumor size was analyzed.

RESULTS

Over the study period there was an increase in the proportion of cases that were observed with follow-up scanning (10.5% to 28.0%) and recommended for radiation (0% to 4.0%), whereas the proportion of operated cases declined (89.5% to 68.0%). There were no changes in mean age or hearing status at diagnosis, but mean tumor size declined significantly. Compared to those undergoing surgery, patients choosing observation and radiation therapy were on average 11.7 and 4.5 years older, respectively. Tumors that were surgically removed were on average 11.6 mm larger than those that were observed. The increasing frequency over time of observation relative to surgery was significant even after controlling for age, hearing status, and tumor size.

CONCLUSIONS

Among patients managed by our center, there has been a significant shift in management of vestibular schwannomas over the last decade, with increasing tendency towards observation. This trend implies changing provider philosophy and patient expectations.

Hearing preservation in surgery for large vestibular schwannomas

OBJECT

Hearing preservation remains a challenging problem in vestibular schwannoma (VS) surgery. The ability to preserve hearing in patients with large tumors is subject to particular difficulty. In this study, the authors focus on hearing preservation in patients harboring large VSs.

METHODS

A total of 344 consecutive patients underwent surgical removal of VSs over the past 9 years. Of these 344 cases, 195 VSs were > 20 mm in maximum cisternal diameter. Of the 195 cases, hearing preservation surgery was attempted for 54 patients who had a Class A, B, C, or D preoperative hearing level; that is, a pure tone average <or= 60 dB and speech discrimination score >or= 50% according to the Sanna/Fukushima classification. The tumors were classified as moderately large (21-30 mm based on the largest extrameatal diameter), large (31-40 mm), and giant (>or= 41 mm) according to the international criteria. The authors categorized patients with Class A, B, C, D, or E hearing (pure tone average <or= 80 dB and speech discrimination score >or= 40%) as having preserved hearing postoperatively.

RESULTS

Forty-one tumors (75.9%) were totally removed and 13 (24.1%) had near-total removal. Of the 54 patients, 29 maintained their hearing postoperatively; the overall hearing preservation rate was 53.7%. Analysis based on the preoperative hearing level showed that hearing was preserved in 14 (77.8%) of 18 cases for Class A; in 8 (47.1%) of 17 cases for Class B; in 4 (57.1%) of 7 cases for Class C; and in 3 (25.0%) of 12 cases for Class D. In addition, according to the analysis based on the tumor size, 20 (52.6%) of 38 patients with moderately large tumors retained their hearing, as did 5 (50.0%) of 10 patients with large tumors and 4 (66.7%) of 6 patients with giant tumors. Complications included 2 cases of bacterial meningitis that were cured by intravenous injection of antibiotics, 3 cases of subcutaneous CSF leakage that resolved without any surgical repair, and 1 case of temporary abducent nerve palsy. There were no deaths in this series.

CONCLUSIONS

The results indicate that successful hearing preservation surgery in large VSs is possible with meticulous technique and attention to adhesions between the tumor and the cochlear nerves.

Hearing preservation and facial nerve function after microsurgery for intracanalicular vestibular schwannomas: comparison of middle fossa and retrosigmoid approaches

PURPOSE

Therapeutic options for vestibular schwannomas (VS) include microsurgery, stereotactic radiosurgery and conservative management. Early treatment of intracanalicular vestibular schwannomas (IVS) may be advisable because their spontaneous course will show hearing loss in most cases. Advanced microsurgical techniques and continuous intraoperative monitoring of cranial nerves may allow hearing preservation (HP) without facial nerve damage. However, there are still controversies about the definition of hearing preservation, and the best surgical approach that should be used.

METHODS

In this study, we reviewed the main data from the recent literature on IVS surgery and compared hearing, facial function and complication rates after the retrosigmoid (RS) and middle fossa (MF) approaches, respectively.

RESULTS

The results showed that the average HP rate after IVS surgery ranged from 58% (RS) to 62% (MF). HP varied widely depending on the audiometric criteria that were used for definition of serviceable hearing. There was a trend to show that the MF approach offered a better quality of postoperative hearing (not statistically significant), whereas the RS approach offered a better facial nerve preservation and fewer complications (not statistically significant).

CONCLUSIONS

We believe that the timing of treatment in the course of the disease and selection between radiosurgical versus microsurgical procedure are key issues in the management of IVS. Preservation of hearing and good facial nerve function in surgery for VS is a reasonable goal for many patients with intracanalicular tumors and serviceable hearing. Once open surgery has been decided, selection of the approach mainly depends on individual anatomical considerations and experience of the surgeon.

Current concepts in management of meningiomas and schwannomas

Meningiomas and schwannomas are the two most common extra-axial intracranial tumors in adults. Since their initial discovery, these often-benign lesions have shared a parallel metamorphosis in their management. The goal of this article is to provide a review of the current literature surrounding the mainstays of therapy for these lesions.

Hypofractionated CyberKnife stereotactic radiosurgery for acoustic neuromas with and without association to neurofibromatosis Type 2

CyberKnife stereotactic radiosurgery (CKSRS) has been proved effective in treating intra-cranial lesions. To treat acoustic neuroma (AN) patients with or without neurofibromatosis Type 2 (NF2) associations, the functional preservation of hearing, trigeminal nerve, and facial nerve are important. Twenty-one patients were treated with hypofractionated CKSRS. Fourteen non-NF2 and seven NF2 patients were enrolled. Cranial nerve function, audiograms, and magnetic resonance images (MRI) were monitored. Mean follow-up was 15 month. Tumors with volumes ranging from 0.13 to 24.8 cm3 (mean 5.4 cm3) were irradiated with the marginal dose 1800-2000 cGy/3 fractions. Tumors were treated with an 80 to 89% isodose line (mean 83%) and mean 97.9% tumor coverage. Two patients experienced hearing deterioration (16.7%) in the non-NF2 group, and 3 patients (50%) in the NF2 group. No facial or trigeminal dysfunction, brain stem toxicity, or cerebellar edema occurred. Tumor regression was seen in 9 patients (43%) and stable in 12 patients (57%). 100% tumor control rate was achieved. Hypofractionated CKSRS was not only effective in tumor control but also excellent in hearing preservation for non-NF2 AN. But for NF2 patients, although the tumor control was remarkable, hearing preservation was modest as in non-NF2 patients.

Vestibular schwannoma volume as a predictor of hearing outcome after surgery

OBJECTIVES

To validate the prognostic capacity of several preoperative and intraoperative parameters of hearing preservation after vestibular schwannoma surgery.

STUDY DESIGN

A retrospective study of a consecutive series of 29 patients treated with the enlarged middle cranial fossa approach. Quantitative parameters were tumor volume, linear tumor size, pure-tone and speech audiometry, pure-tone average, speech discrimination score, speech reception threshold, auditory brainstem response (ABR; intra-aural interpeak latency I-V, interaural wave V latency difference), and the vestibular caloric test (speed and frequency). Qualitative parameters were fundus involvement by the tumor (in magnetic resonance imaging and surgical record), nerve of tumor origin (in magnetic resonance imaging and surgical record), ABR parameters (well-shaped ABRs: waves I, III, and V present; presence of wave V).

METHODS

All patients were divided into 2 groups on the basis of postoperative hearing: preserved hearing (55%) or nonpreserved hearing (45%). The Kolmogorov-Smirnov test was used to evaluate normality of distribution for continuous data. The t test was applied for normally distributed continuous data and the Mann-Whitney test for nonnormally distributed continuous data. The chi2 test was used for comparisons of categoric data.

RESULTS

Tumor volume was found to be the only statistically significant prognostic parameter for hearing preservation (p = 0.007). The cutoff point for the "critical" tumor volume for hearing preservation was calculated to 0.20 cm. None of the other parameters reached statistical significance.

CONCLUSION

Tumor size is a predictive factor for hearing preservation after vestibular schwannoma surgery, and patients with smaller tumors, based on volume measurement, have significantly better chances for retaining hearing. This has an impact on decision making and timing of surgery.

Safety and efficacy of fractionated stereotactic radiotherapy for acoustic neuromas

BACKGROUND

The treatment of acoustic neuromas (AN) has historically involved surgical excision or stereotactic radiosurgery, with a relatively limited number of reports available describing the use of fractionated stereotactic radiotherapy (FSRT). To enhance the existing knowledge regarding the safety and efficacy of this treatment modality, we describe our initial experience with FSRT for AN.

METHODS

From 1999-2005, 20 patients (12F, 8M) with AN underwent FSRT. All patients were treated using the Radionics X-Knife 4.0 3D planning system, receiving 54 Gy in 1.8 Gy daily fractions with a prescription isodose line of 90%. Treatments were delivered stereotactically using a dedicated Varian 6/100 linear accelerator, with immobilization achieved via the Gill-Thomas-Cosman relocatable frame. Median tumor size (maximum diameter) was 2.1 cm (range, 1.1-3.4 cm). Median patient age was 49.5 years, with median follow-up of 22 months (range, 1-66 months). All patients were evaluated with pre- and post-gadolinium-enhanced magnetic resonance imaging.

RESULTS

Following FSRT, local tumor control was achieved in every patient, with the treatment well-tolerated by all patients. No patient experienced acute complications or facial nerve weakness. Two patients experienced permanent trigeminal nerve morbidity manifesting as facial numbness. All nine patients with preserved hearing before treatment had hearing preservation at last follow-up, although four of these patients experienced hearing decline following FSRT.

CONCLUSION

In our series of 20 patients with AN, all had local tumor control following FSRT, with minimal morbidity. These results support the growing body of literature demonstrating the safety and efficacy of FSRT in achieving local control for AN, further validating the viability of FSRT as a treatment modality for this patient population.

Endolymphatic Duct Status During Middle Fossa Dissection of the Internal Auditory Canal: A Human Temporal Bone Radiographic Study

OBJECTIVE

Successful hearing preservation after acoustic neuroma resection is sometimes complicated by delayed hearing deterioration. The middle fossa approach appears to offer superior long-term hearing results when compared to the retrosigmoid surgical approach. The goal of this study is to investigate the hypothesis that internal auditory canal (IAC) drilling during middle fossa acoustic neuroma removal is associated with a lower incidence of endolymphatic duct (ELD) injury, a potential cause of delayed hearing loss (HL) known to accompany retrosigmoid hearing preservation dissection techniques.

STUDY DESIGN

A human temporal bone anatomic and radiographic study complemented with a literature review.

METHODS

Twenty human temporal bones were analyzed with high-resolution multislice computed tomography (HRMCT) and subjected to standard extended middle fossa IAC dissection with labyrinthine preservation and follow-up HRMCT for analyses of the ELD.

RESULTS

Zero of 20 (0%) temporal bones were found to have violation of the ELD with preservation of the labyrinthine structures and the endolymphatic sac. Reviews of human and animal studies indicate that injury to the ELD may create endolymphatic hydrops, a known cause of hearing deterioration.

CONCLUSION

The ELD is not vulnerable to injury during IAC dissection using the middle fossa approach. A previous radiographic study has shown that the ELD is violated in 24% of temporal bones during retrosigmoid dissection of the IAC. These findings support and may help explain other outcome studies that show that long-term hearing results are superior with the use of the middle fossa approach when compared to results following retrosigmoid dissection.

Preoperative predictive factors for hearing preservation in vestibular schwannoma surgery

OBJECTIVES

We performed a retrospective chart review to evaluate the various predictive factors for postoperative hearing preservation in the surgical management of vestibular schwannoma.

METHODS

Of 792 patients operated on for vestibular schwannoma between April 1987 and July 2002, 107 were candidates for hearing preservation surgery. These patients were divided into group 1 (hearing preserved) and group 2 (hearing not preserved), and both of these groups were evaluated for age, sex, pure tone average, sound discrimination score, tumor size, and auditory brain stem response parameters. A corrected chi2 test and a corrected t-test were used for statistical analysis. Multiple regression analysis was further done to evaluate independent predictive factors, either alone or in combination. The results were evaluated by use of the modified Sanna classification and the guidelines of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS).

RESULTS

Preoperative pure tone average and tumor size were the 2 predictive factors in our study. A Pearson correlation test showed that there was no multicollinearity between the factors. On multiple regression analysis by backward elimination of nonsignificant factors, we found that tumor size is an independent predictive factor for postoperative hearing. According to the modified Sanna classification, postoperative hearing was preserved in 11.2% of patients (equivalent to class A of AAO-HNS guidelines).

CONCLUSIONS

In our series, preoperative pure tone average and tumor size were found to be predictors of postoperative hearing levels.

Conservative management versus surgery for small vestibular schwannomas

A high rate of deterioration in hearing function and the loss of patient compliance during conservative management should be taken into account when considering hearing preservation strategies for patients with vestibular schwannoma (VS). To compare conservative management with surgery for solitary small VS. Among 693 patients followed up for VS between 1991 and 2002, 114 (16%) intracanalicular VSs (stage 1) and 302 (44%) VSs measuring <15 mm in the cerebellopontine angle (stage 2) were included in this study. Initially, surgery was performed in 305 (73%) cases (50 stage 1, 255 stage 2) and 111 (27%) were managed conservatively (64 stage 1, 54 stage 2) by means of annual MRI scans and audiometry. Conservative management was chosen in patients aged >60 years and in those who refused surgery. In this subgroup, the mean follow-up period was 33 months (range 6-111 months). In the conservative management group, 47% of VSs showed significant growth, 47% were stable and 6% showed regression. Seventeen patients (15%) were operated on secondarily for tumour growth and 1 (1%) was irradiated for tumour growth and because surgery was contraindicated. Deterioration of hearing function by > or =1 class was observed in 56% of cases, 34% of patients were initially in hearing class D and only 10% showed stable hearing function. Of the conservative management group, 17% were lost during follow-up. After surgery, grade 1 or 2 facial function was obtained in 86% of cases. Following hearing preservation attempts (n=137), 54% of patients were in hearing classes A-C.

Staged Stereotactic Irradiation for Acoustic Neuroma

OBJECTIVE:

Stereotactic radiosurgery has proven effective in the treatment of acoustic neuromas. Prior reports using single-stage radiosurgery consistently have shown excellent tumor control, but only up to a 50 to 73% likelihood of maintaining hearing at pretreatment levels. Staged, frame-based radiosurgery using 12-hour interfraction intervals previously has been shown by our group to achieve excellent tumor control while increasing the rate of hearing preservation at 2 years to 77%. The arrival of CyberKnife (Accuray, Inc., Sunnyvale, CA) image-guided radiosurgery now makes it more practical to treat acoustic neuroma with a staged approach. We hypothesize that such factors may further minimize injury of adjacent cranial nerves. In this retrospective study, we report our experience with staged radiosurgery for managing acoustic neuromas.

METHODS:

Since 1999, the CyberKnife has been used to treat more than 270 patients with acoustic neuroma at Stanford University. Sixty-one of these patients have now been followed up for a minimum of 36 months and form the basis for the present clinical investigation. Among the treated patients, the mean transverse tumor diameter was 18.5 mm, whereas the total marginal dose was either 18 or 21 Gy using three 6- or 7-Gy fractions. Audiograms and magnetic resonance imaging were obtained at 6-months intervals after treatment for the first 2 years and then annually thereafter.

RESULTS:

Of the 61 patients with a minimum of 36 months of follow-up (mean, 48 mo), 74% of patients with serviceable hearing (Gardner-Robinson Class 1–2) maintained serviceable hearing at the last follow-up, and no patient with at least some hearing before treatment lost all hearing on the treated side. Only one treated tumor (2%) progressed after radiosurgery; 29 (48%) of 61 decreased in size and 31 (50%) of the 61 tumors were stable. In no patients did new trigeminal dysfunction develop, nor did any patient experience permanent injury to their facial nerve; two patients experienced transient facial twitching that resolved in 3 to 5 months.

CONCLUSION:

Although still preliminary, these results indicate that improved tumor dose homogeneity and a staged treatment regimen may improve hearing preservation in acoustic neuroma patients undergoing stereotactic radiosurgery.