Factors associated with preservation of facial nerve function after surgical resection of vestibular schwannoma.

Avoidance of facial nerve palsy is one of the major goals of vestibular schwannoma (VS) microsurgery. In this study, we examined the significance of previously implicated prognostic factors (age, tumor size, the extent of resection and the surgical approach) on post-operative facial nerve function. We selected all VS patients from prospectively collected database (1984-2009) who underwent microsurgical resection as their initial treatment for histopathologically confirmed VS. The effect of variables such as surgical approach, tumor size, patient age and extent of resection on rates facial nerve dysfunction after surgery, were analyzed using multivariate logistic regression. Patients with preoperative facial nerve dysfunction (House-Brackman [HB] score 3 or higher) were excluded, and HB grade of 1 or 2 at the last follow-up visit was defined as "facial nerve preservation." A total of 624 VS patients were included in this study. Multivariate logistic regression analysis found that only pre-operative tumor size significantly predicted poorer facial nerve outcome for patients followed-up for ≥6 and ≥12 months (OR 1.27, 95% CI 1.09-1.49, p < 0.01; OR 1.35, 95% CI 1.10-1.67, P < 0.01, respectively). We found no significant relationship between facial nerve function and age, extent of resection, surgical approach, or tumor size (when extent of resection and surgical approach were included in the regression analysis). Because facial nerve palsy is a debilitating and psychologically devastating condition for the patient, we suggest altering surgical aggressiveness in patients with unfavorable tumor anatomy, particularly in cases with large tumors where overaggressive resection might subject the patient to unwarranted risk. Residual disease can be followed and controlled with radiosurgery if interval growth is noted.

Facial nerve preservation after vestibular schwannoma Gamma Knife radiosurgery.

OBJECTIVE: Facial nerve preservation is a critical measure of clinical outcome after vestibular schwannoma treatment. Gamma Knife radiosurgery has evolved into a practical treatment modality for vestibular schwannoma patients, with several reported series from a variety of centers. In this study, we report the results of an objective analysis of reported facial nerve outcomes after the treatment of vestibular schwannomas with Gamma Knife radiosurgery. MATERIALS AND METHODS: A Boolean Pub Med search of the English language literature revealed a total of 23 published studies reporting assessable and quantifiable outcome data regarding facial nerve function in 2,204 patients who were treated with Gamma Knife radiosurgery for vestibular schwannoma. Inclusion criteria for articles were: (1) Facial nerve preservation rates were reported specifically for vestibular schwannoma, (2) Facial nerve functional outcome was reported using the House-Brackmann classification (HBC) for facial nerve function, (3) Tumor size was documented, and (4) Gamma Knife radiosurgery was the only radiosurgical modality used in the report. The data were then aggregated and analyzed based on radiation doses delivered, tumor volume, and patient age. RESULTS: An overall facial nerve preservation rate of 96.2% was found after Gamma Knife radiosurgery for vestibular schwannoma in our analysis. Patients receiving less than or equal to 13 Gy of radiation at the marginal dose had a better facial nerve preservation rate than those who received higher doses (13 Gy = 94.7%, P < 0.0001). Patients with a tumor volume less than or equal to 1.5 cm(3) also had a greater facial nerve preservation rate than patients with tumors greater than 1.5 cm(3) (1.5 cm(3) 95.5%, P < 0.0001). Superior facial nerve preservation was also noted in patients younger than or equal to 60 years of age (96.8 vs. 89.4%, P < 0.0001). The average reported follow up duration in this systematic review was 54.1 +/- 31.3 months. CONCLUSION: Our analysis of case series data aggregated from multiple centers suggests that a facial nerve preservation rate of 96.2% can be expected after Gamma knife radiosurgery for vestibular schwannoma. Younger patients with smaller tumors less than 1.5 cm(3) and treated with lower doses of radiation less than 13 Gy will likely have better facial nerve preservation rates after Gamma Knife radiosurgery for vestibular schwannoma.

Hearing preservation after stereotactic radiosurgery for vestibular schwannoma: a systematic review.

Radiosurgery has evolved into an effective alternative to microsurgical resection in the treatment of patients with vestibular schwannoma. We performed a systematic analysis of the literature in English on the radiosurgical treatment of vestibular schwannoma patients. A total of 254 published studies reported assessable and quantifiable outcome data of patients undergoing radiosurgery for vestibular schwannomas. American Association of Otolaryngology-Head and Neck Surgery (AAO-HNS) class A or B and Gardner-Robertson (GR) classification I or II were defined as having preserved hearing. A total of 5825 patients (74 articles) met our inclusion criteria. Practitioners who delivered an average dose of 12.5 Gy as the marginal dose reported having a higher hearing preservation rate (12.5 Gy=59% vs. >12.5 Gy=53%, p=0.0285). Age of the patient was not a significant prognostic factor for hearing preservation rates (<65 years=58% vs. >65 years=62%; p=0.4317). The average overall follow-up was 41.2 months. Our data suggest that an overall hearing preservation rate of about 57% can be expected after radiosurgical treatment, and patients treated with 12.5 Gy were more likely to have preserved hearing.

Intraoperative electrophysiologic identification of the nervus intermedius.

OBJECTIVE: Although enormous attention has been directed to the localization and preservation of the facial nerve in acoustic neuroma surgery, the nervus intermedius has largely been ignored. In this article, we describe a method for intraoperative electrophysiologic identification of the nervus intermedius. STUDY DESIGN: Retrospective case review. SETTING: University hospital (tertiary care center). PATIENTS: Thirty-three patients who underwent intraoperative facial nerve monitoring for various cerebellopontine angle procedures. Recording electrodes were placed in the orbicularis oculi and orbicularis oris muscles. A constant-voltage stimulator was used to stimulate both the facial nerve and the nervus intermedius. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Electrophysiologic response after stimulation of the nervus intermedius. RESULTS: Stimulation of the nervus intermedius produced long-latency, low-amplitude response recorded only on the orbicularis oris channel. The response had a mean threshold 0.4 V, a mean latency of 11.1 ms, and a mean amplitude of 11.1 microV, all significantly different from responses to stimulation the facial nerve. CONCLUSION: Knowledge of electrophysiologic features of nervus intermedius stimulation can help protect the facial nerve during cerebellopontine angle surgery. The surgeon must recognize that stimulation of the nervus intermedius can cause electromyographic activity in the facial nerve monitoring channels, but the main trunk of the facial nerve may lie in entirely different location in the cerebellopontine angle.

Clinical trials in head injury.

Traumatic brain injury (TBI) remains a major public health problem globally. In the United States the incidence of closed head injuries admitted to hospitals is conservatively estimated to be 200 per 100,000 population, and the incidence of penetrating head injury is estimated to be 12 per 100,000, the highest of any developed country in the world. This yields an approximate number of 500,000 new cases each year, a sizeable proportion of which demonstrate significant long-term disabilities. Unfortunately, there is a paucity of proven therapies for this disease. For a variety of reasons, clinical trials for this condition have been difficult to design and perform. Despite promising pre-clinical data, most of the trials that have been performed in recent years have failed to demonstrate any significant improvement in outcomes. The reasons for these failures have not always been apparent and any insights gained were not always shared. It was therefore feared that we were running the risk of repeating our mistakes. Recognizing the importance of TBI, the National Institute of Neurological Disorders and Stroke (NINDS) sponsored a workshop that brought together experts from clinical, research, and pharmaceutical backgrounds. This workshop proved to be very informative and yielded many insights into previous and future TBI trials. This paper is an attempt to summarize the key points made at the workshop. It is hoped that these lessons will enhance the planning and design of future efforts in this important field of research.

Risk-benefit analysis of using the middle fossa approach for acoustic neuromas with >10 mm cerebellopontine angle component.

OBJECTIVES: To evaluate hearing preservation and facial nerve (FN) outcome in the middle fossa (MF) approach for acoustic neuromas with a cerebellopontine angle (CPA) component >10 mm. STUDY DESIGN: Retrospective review of 193 patients. PATIENT POPULATION: Patients were grouped according to tumor size: intracanalicular tumors (IC; 64), 1 to 9 mm CPA extension (42), and 10 to 18 mm CPA extension (47). Additionally, a group of 40 patients (tumor size 10-18 mm CPA extension) who had undergone a translabyrinthine (TL) approach was studied to assess comparative FN outcome. Hearing and FN function were measured 1 year postoperatively. We defined the success at functional hearing preservation as AAO-HNS class B or better and good FN outcome as House-Brackmann grade II or better. RESULTS: For IC tumors and those with up to 9-mm CPA extension, there was no significant difference in the rate of functional hearing preservation (62.2% vs. 63.1%, P =.931) and good FN outcome (93.7% vs. 97.6%, P =.358). For tumors of 10- to 18-mm CPA extension, the rate of hearing preservation (34%) was lower than the other groups (P =.006 and P =.009). In this group, the rate of good FN outcome was lower compared with the IC and 1- to 9-mm tumors (80.8% vs. 93.7%, P =.037 and 97.6%, P =.012). The rate of good FN outcome following the TL approach in a comparable cohort of patients was 100% (P =.003 in comparison with 10-18 mm tumor resected with the MF approach). CONCLUSIONS: When considering surgical options, patients with >10-mm tumors should be advised that choosing the MF approach for hearing preservation carries a somewhat higher risk of persistent FN dysfunction.

Cerebrospinal fluid leak after acoustic neuroma surgery: a comparison of the translabyrinthine, middle fossa, and retrosigmoid approaches.

OBJECTIVE: To determine whether the choice of surgical approach affects the rate of postoperative cerebrospinal fluid leakage in patients who have undergone surgical resection of acoustic neuroma. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary referral center. PATIENTS: Three hundred patients who underwent surgery for acoustic neuromas were selected by consecutive medical record number until 100 resections via each surgical approach (translabyrinthine, middle fossa, and retrosigmoid) had been gathered. MAIN OUTCOME MEASURES: Surgical approach used, cerebrospinal fluid leak incidence, tumor size, patient age. RESULTS: Postoperative cerebrospinal fluid leak of any severity was observed in 13% of translabyrinthine, 10% of middle fossa, and 10% of retrosigmoid patients. These difference in the rate of cerebrospinal fluid leakage were not statistically significant (p = 0.82). The majority of leaks were managed conservatively with fluid and activity restriction, often accompanied by a period of lumbar subarachnoid drainage. There was a need to return to the operating room for a definitive procedure in 4% of translabyrinthine, 2% of middle fossa, and 3% retrosigmoid patients; again not statistically different among the approaches (p = 0.43). Tumor size was not correlated with cerebrospinal fluid leak rate (p = 0.13). Patient age, for patients older than 50 years, was suggestive of increased odds of cerebrospinal fluid leak (p = 0.06). CONCLUSION: Neither surgical approach nor tumor size affects the rate of postoperative cerebrospinal fluid leakage or the necessity of managing a leak with a return to the operating room. Cerebrospinal fluid leakage rates have remained stable in recent decades despite numerous innovative attempts to improve dural closure, seal transected air cell tracts, and occlude anatomic pathways. The finding that leak rates were similar among three dissimilar surgical techniques suggests that factors other than techniques of wound closure, such as transient postoperative rises in cerebrospinal fluid pressure, may be responsible for these recalcitrant cases.

The fate of the tumor remnant after less-than-complete acoustic neuroma resection.

OBJECTIVES: We sought to determine the recurrence rate after near-total and subtotal resection of acoustic neuroma. STUDY DESIGN, SETTING, AND PATIENTS: We conducted a retrospective chart review of a total of 79 patients: 50 with near-total resections (remnant < or =25 mm(2) and < or =2 mm thick) and 29 with subtotal resections (any larger remnant). Surgical approach included 5 middle fossa, 17 retrosigmoid, and 57 translabyrinthine. MAIN OUTCOME MEASURES: Recurrence was defined as documented tumor growth by serial imaging or the recommendation for further treatment after a single scan. No recurrence was defined as no visible tumor on imaging for a minimum follow-up time of 3 years or tumor remnants that remained unchanged on serial scans (mean, 5-year follow-up). RESULTS: Fifty-two patients were included in the study group. Recurrences were seen in 1 (3%) of 33 patients who had a near-total resection compared with 6 (32%) of 19 patients who had a subtotal resection. After adjustment for follow-up time and large tumor size, the odds ratio for recurrence was 12 times larger for subtotal than for near-total resections (P = 0.033). All recurrences were seen following the translabyrinthine approach in the mid-cerebellopontine angle. None were encountered in the internal auditory canal. The mean time interval from surgery to the detection of a recurrence was 3 years (range, 1 to 5 years). CONCLUSIONS: The recurrence rate when performing a near-total resection is low but is substantially higher with a subtotal resection. Recurrences can be detected within the first 5 postoperative years. We recommend near-total resection in any patient if needed to preserve neural integrity. Subtotal resection is best avoided whenever possible; however, adjunctive treatment with stereotactic radiotherapy may be considered.

Is it worthwhile to attempt hearing preservation in larger acoustic neuromas?

OBJECTIVE: To determine the hearing outcome in patients undergoing surgery via the retrosigmoid approach for acoustic neuromas with a substantial component in the cerebellopontine angle. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: The medical records of all patients undergoing acoustic neuroma removal via the retrosigmoid approach at a tertiary referral center were retrospectively reviewed. Sixty-four patients with both cerebellopontine angle component >or=15 mm and preoperative audiometry of class A or B (American Academy of Otolaryngology-Head and Neck Surgery) were identified. MAIN OUTCOME MEASURES: Postoperative average pure tone threshold and word recognition scores, categorized according to the classification of the American Academy of Otolaryngology-Head and Neck Surgery, were used to assess hearing outcome. RESULTS: Overall, only 6.3% (4 of 63) retained good hearing (class A or B) postoperatively. Hearing preservation rate in the smallest (15- to 19-mm) group was 17.6% (3 of 17), which was better than that for the larger groups. No successful hearing preservation was achieved in tumors with >or=25 mm cerebellopontine angle component (0 of 23). CONCLUSIONS: Surgeon and patient alike would always choose a hearing preservation technique if there was no potential for increased morbidity in making the attempt. When compared with the non-hearing preservation translabyrinthine approach, the retrosigmoid approach had a higher incidence of persistent headache. In addition, efforts to conserve the auditory nerve prolong operating time, increase the incidence of postoperative vestibular dysfunction, and carry a slightly higher risk of tumor recurrence. Nevertheless, even though the probability of success is disappointingly small, when excellent hearing is present we favor offering the option of a hearing conservation attempt when the patient has been well informed of the pros and cons of the endeavor. Factors weighing against undertaking this effort include larger cerebellopontine angle component (>or=25 mm), deep involvement of the fundus, wide erosion of the porus, and marginal residual hearing.

The effect of age on acoustic neuroma surgery outcomes.

OBJECTIVES: To ascertain the effect of age on hearing preservation, facial nerve outcome, and complication rates after acoustic neuroma surgery. STUDY DESIGN: Retrospective chart review. Two study arms were used: a comparison of the authors' oldest patients with their youngest patients (extremes of age arm) and an analysis of all middle fossa surgical procedures (middle fossa arm). SETTING: Tertiary referral center PATIENTS: Total of 329 patients. For the extremes of age arm, 205 patients were studied in two cohorts with 150 older patients (>60 years) compared with 55 younger patients (<40 years). The approaches included 21 middle fossa (MF), 38 retrosigmoid (RS), and 91 translabyrinthine (TL) procedures in the older group versus 25 MF, 17 RS, and 13 TL in the younger. For the middle fossa arm, there were 170 patients (age range 15-76 years) who underwent the MF approach for an attempt at hearing preservation. MAIN OUTCOME MEASURES: Hearing preservation was defined as the maintenance of either class A or class B hearing (AAO-HNS class). Good facial nerve outcome was considered the maintenance of either grade 1 or 2 (House-Brackmann scale). Cerebrospinal fluid leak rates and other postoperative complications were also tabulated. RESULTS: After adjustment for tumor size and surgical approach using multiple logistic regression analysis, the extremes of age study arm demonstrated that there is a lower chance of preserving good hearing in older patients (p = 0.048, odds ratio = 0.30). Age was not associated with a difference in the rate of good facial nerve outcome (p = 0.2). There was a trend toward slightly higher rates of cerebrospinal fluid leak in the older patient group (p = 0.07) but no difference in the rate of other complications (p = 0.9). The middle fossa study arm, after adjustment for tumor size and surgical approach, demonstrated that older patient age is associated with a lower rate of preservation of good hearing (p = 0.01, O.R.=1.044). There was no association between age and good facial outcome (p = 0.7). CONCLUSIONS: Older patient age lowers the chance of hearing preservation but does not affect facial outcomes. There is a trend toward a higher rate of cerebrospinal fluid leak in older patients, but no increased risk of other complications.

Distal anterior inferior cerebellar artery syndrome after acoustic neuroma surgery.

OBJECTIVE: To define a clinicopathologic syndrome associated with persistent cerebellar dysfunction after acoustic neuroma (AN) excision. STUDY DESIGN: Case series derived from radiographic and clinical chart review. SETTING: Tertiary referral center. PATIENTS: In 12 patients with AN, persistent cerebellar dysfunction developed after AN removal. Each case demonstrated abnormality in the ipsilateral cerebellar peduncle on postoperative magnetic resonance imaging. MAIN OUTCOME MEASURES: Cerebellar function and ambulatory status over the first postoperative year. RESULTS: On magnetic resonance imaging scans, the extent of cerebellar peduncle infarcts was variable. It ranged from focal brain injury (<1 cm) involving only one third of the peduncle to diffuse defects (>2 cm) spanning the full thickness of the peduncle. Peduncular infarcts were associated with large tumor size (average 3.8 cm, range 2.0-5.5 cm diameter). The long-term functional outcomes (>1 yr) varied. Dysmetria was unchanged or improved in over half of the patients (6 of 11 patients). Gait recovered to normal or to preoperative levels in 5 patients. In the 6 patients with persistent impaired mobility, 2 had mild gait disturbance, 3 required regular use of a cane, and 1 has been dependent on a walker. One patient had sustained mild motor weakness. Three of 11 patients remained dependent on others for activities of daily living. CONCLUSIONS: Peduncle injury most likely stems from interruption of distal branches of the anterior inferior cerebellar artery (AICA). These small vessels are intimately related to the capsule of the tumor and may supply both the neoplasm and the brain parenchyma. It has long been recognized that interruption of the proximal segment of the AICA results in severe injury to the pons, with devastating neurologic sequelae. A limited AICA syndrome caused by loss of its distal ramifications seems a more plausible explanation for peduncular infarction than either venous insufficiency or direct surgical trauma.

Intratumoral hemorrhage and fibrosis in vestibular schwannoma: a possible mechanism for hearing loss.

OBJECT: Vestibular schwannomas (VSs) are benign lesions with an unpredictable natural history. Perhaps the greatest barrier to predicting which patients need treatment is our poor understanding of how these tumors cause hearing loss in the first place. In this case-control study, the authors investigated the relationship between preoperative hearing loss and histological changes such as intratumoral microhemorrhage and extensive fibrosis. METHODS: From a prospectively collected database, the authors selected all patients with VS who had undergone microsurgical resection as their initial treatment for histopathologically confirmed VS. Histological specimens obtained in 274 of these patients were systematically reviewed by a blinded neuropathologist who graded the extent of microhemorrhage and fibrosis in these tumors. The effect of these variables on preoperative hearing loss was studied using binary logistic regression. RESULTS: On univariate analysis, patients with extensive intratumoral microhemorrhage or fibrosis (p < 0.0001), patients with larger tumors (p < 0.05), and patients 65 years of age or older (p < 0.05) were significantly more likely to have unserviceable hearing at the time of surgery. On multivariate analysis, only patients with extensive intratumoral microhemorrhage or fibrosis had an increased risk of having unserviceable hearing at the time of surgery (OR 3.72, 95% CI 1.3-10; p = 0.01). Older age and tumor size greater than 3 cm were not statistically significant risk factors for hearing loss, controlling for the effect of microhemorrhage and fibrosis. CONCLUSIONS: In this study, the authors have demonstrated a correlation between the extent of nonneoplastic histological changes, such as microhemorrhage and fibrosis, and hearing loss. This alternate hypothesis has the potential to explain many of the exceptions to previously described mechanisms of hearing loss in patients with VS. The advent of high-resolution MR imaging technology to identify microhemorrhages may provide a method to screen for patients with VS at risk for hearing loss.

Extent of resection and the long-term durability of vestibular schwannoma surgery.

OBJECT: With limited studies available, the correlation between the extent of resection and tumor recurrence in vestibular schwannomas (VSs) has not been definitively established. In this prospective study, the authors evaluated 772 patients who underwent microsurgical resection of VSs to analyze the association between total tumor resection and the tumor recurrence rate. METHODS: The authors selected all cases from a prospectively collected database of patients who underwent microsurgical resection as their initial treatment for a histopathologically confirmed VS. Recurrence-free survival was analyzed using Kaplan-Meier analysis. The authors studied the impact of possible confounders such as patient age and tumor size using stepwise Cox regression to calculate the proportional hazard ratio of recurrence while controlling for other cofounding variables. RESULTS: The authors analyzed data obtained in 571, 89, and 112 patients in whom gross-total, near-total, and subtotal resections, respectively, were performed. A gross-total resection was achieved in 74% of the patients, and the overall recurrence rate in these patients 8.8%. There was no significant relation between the extent of resection and the rate of tumor recurrence (p = 0.58). As expected, the extent of resection was highly correlated with patient age, tumor size, and surgical approach (p < 0.0001). Using Cox regression, the authors found that the approach used did not significantly affect tumor control when the extent of resection was controlled for. CONCLUSIONS: While complete tumor removal is ideal, the results presented here suggest that there is no significant relationship between the extent of resection and tumor recurrence.

A prospective study of hearing preservation in untreated vestibular schwannomas.

OBJECT: The authors previously published a systematic review of the English language literature regarding the natural history of untreated vestibular schwannomas (VSs). This analysis found that the best predictor of future hearing loss was tumor growth > 2.5 mm/year on serial imaging, a factor that doubled the rate of hearing loss. In this paper the authors present an analysis of prospectively collected outcomes in patients with untreated VS from their institution that confirms their previous findings. METHODS: Clinical, radiographic, and audiometric data for all patients evaluated for VS at the authors' institution over a 22-year period were prospectively collected in a database. All patients in this database who had serviceable hearing (American Academy of Otolaryngology-Head and Neck Surgery Grade A or B) on initial presentation were selected, and underwent serial observation. Magnetic resonance imaging and audiometric data were analyzed, and the time from presentation until hearing loss was analyzed using Kaplan-Meier analysis. RESULTS: Fifty-nine patients with VS who initially presented with serviceable hearing were treated conservatively over this period. Consistent with the authors' previous findings, patients with a tumor growth rate > 2.5 mm/year at any point during follow-up lost their hearing at a much faster rate than those who had slower growing tumors. The median time to hearing loss was 7.0 years in those patients with tumor growth rate > 2.5 mm/year compared to 14.8 years in the other patients (p < 0.0001). The estimated median time to hearing loss in the 3 initial tumor size groups was 11.6 years in the intracanalicular group, 10.3 years in the group with 0.1-1 cm extension into the CPA cistern, and 9.3 years in the group with > 1 cm extension into the CPA cistern (p value nonsignificant). Initial tumor size, age at diagnosis, and neurofibromatosis Type 2 status did not affect the time to loss of serviceable hearing. Interestingly, many patients who were followed up for more than a decade eventually lost their hearing, regardless of whether the tumor displayed any documented interval growth. CONCLUSION: The authors confirmed the findings of their systematic review of the literature using a prospectively followed group of patients with untreated VS. Collectively, these data suggest that the expectation for more rapid hearing loss should be communicated to patients, and the decision for surgical or other intervention should be made in the context of the known risk of continued observation of fast growing tumors.

Implications of cystic features in vestibular schwannomas of patients undergoing microsurgical resection.

BACKGROUND: Cystic vestibular schwannomas (VSs) are described as being more aggressive than solid tumors. OBJECTIVE: We examined 468 VS patients to evaluate whether the presence of cystic components in VSs may be an important feature for predicting postoperative outcome. METHODS: We selected all VS patients from a prospectively collected database (1984-2009) who underwent microsurgical resection for VS. Hearing data were analyzed using American Association of Otolaryngology-Head and Neck Surgery. Facial nerve dysfunction was analyzed using the House-Brackmann scale. We used univariate comparisons to determine the clinical impact of cystic changes on preoperative and postsurgical hearing and facial nerve preservation. RESULTS: We identified 58 patients (11%) with cystic changes and 410 patients with solid VSs. In this analysis, cystic VS patients tended to have larger tumors (78% of patients with >2.0 cm extrameatal extension) compared with the solid VS group, which consisted of many smaller and medium-sized tumors (P < .0001). Univariate analyses found that tumors with cystic changes did not lead to worse rates of preoperative hearing loss (χ(2), P = not significant) compared with solid VSs. Cystic changes conferred worse postoperative hearing in patients with medium-sized tumors (P = .035). Cystic changes also did not significantly affect facial nerve outcomes (χ(2), P = not significant). CONCLUSION: Cystic tumors tend to be larger than noncystic tumors and affect outcomes by reducing the rate at which hearing preservation is attempted and by worsening hearing outcome in medium-sized tumors. Further, peripheral cysts cause lower rates of hearing preservation compared with centrally located cysts.

A comprehensive analysis of hearing preservation after radiosurgery for vestibular schwannoma.

OBJECT: Gamma Knife surgery (GKS) has evolved into a practical alternative to open microsurgical resection in the treatment of patients with vestibular schwannoma (VS). Hearing preservation rates in GKS series suggest very favorable outcomes without the possible acute morbidity associated with open microsurgery. To mitigate institutional and practitioner bias, the authors performed an analytical review of the published literature on the GKS treatment of vestibular schwannoma patients. Their aim was to objectively characterize the prognostic factors that contribute to hearing preservation after GKS, as well as methodically summarize the reported literature describing hearing preservation after GKS for VS. METHODS: A comprehensive search of the English-language literature revealed a total of 254 published studies reporting assessable and quantifiable outcome data obtained in patients who underwent radiosurgery for VSs. Inclusion criteria for articles were 4-fold: 1) hearing preservation rates reported specifically for VS; 2) hearing status reported using the American Association of Otolaryngology-Head and Neck Surgery (AAO-HNS) or Gardner-Robertson classification; 3) documentation of initial tumor size; and 4) GKS was the only radiosurgical modality in the treatment. In the analysis only patients with AAO-HNS Class A or B or Gardner-Robertson Grade I or II status at the last follow-up visit were defined as having preserved hearing. Hearing preservation and outcome data were then aggregated and analyzed based on the radiation dose, tumor volume, and patient age. RESULTS: The 45 articles that met the authors' inclusion criteria represented 4234 patients in whom an overall hearing preservation rate was 51%, irrespective of radiation dose, patient age, or tumor volume. Practitioners who delivered an average < or = 13-Gy dose of radiation reported a higher hearing preservation rate (60.5% at < or = 13 Gy vs 50.4% at > 13 Gy; p = 0.0005). Patients with smaller tumors (average tumor volume < or = 1.5 cm(3)) had a hearing preservation rate (62%) comparable with patients harboring larger tumors (61%) (p = 0.8968). Age was not a significant prognostic factor for hearing preservation rates as in older patients there was a trend toward improved hearing preservation rates (56% at < 65 years vs 71% at > or = 65 years of age; p < 0.1134). The average overall follow-up in the studies reviewed was 44.4 +/- 32 months (median 35 months). CONCLUSIONS: These data provide a methodical overview of the literature regarding hearing preservation with GKS for VS and a less biased assessment of outcomes than single-institution studies. This objective analysis provides insight into advising patients of hearing preservation rates for GKS treatment of VSs that have been reported, as aggregated in the published literature. Analysis of the data suggests that an overall hearing preservation rate of approximately 51% can be expected approaching 3-4 years after radiosurgical treatment, and the analysis reveals that patients treated with < or = 13 Gy were more likely to have preserved hearing than patients receiving larger doses of radiation. Furthermore, larger tumors and older patients do not appear to be at any increased risk for hearing loss after GKS for VS than younger patients or patients with smaller tumors.

The natural history of untreated sporadic vestibular schwannomas: a comprehensive review of hearing outcomes.

OBJECT: Observation is an important consideration when discussing management options for patients with vestibular schwannoma (VS). Most data regarding clinical outcomes after conservative management come from modestsized series performed at individual centers. The authors performed an analysis of the published literature on the natural history of VSs with respect to hearing outcome. Their objective was to provide a comprehensive and unbiased description of outcomes in patients whose disease was managed conservatively. METHODS: The authors identified a total of 34 published studies containing hearing outcome data in patients with VSs < 25 mm in largest diameter who underwent observation management. The effects of initial tumor size and tumor growth rate on hearing function at latest follow-up were analyzed. Data from individual and aggregated cases were extracted from each study. Patients with poorer hearing (American Association of Otolaryngology-Head and Neck Surgery Classes C or D, or Gardner-Robertson Classes III, IV, or V) at the time of presentation were excluded. RESULTS: A total of 982 patients met the inclusion criteria for this analysis, with a mean initial tumor size of 11.3 +/- 0.68 mm. The mean growth rate was 2.9 +/- 1.2 mm/year. The length of follow-up for these studies ranged from 26 to 52 months. Patients with preserved hearing at latest follow-up had a statistically larger initial tumor size than those whose hearing declined during the observation period (11.5 +/- 2.3 mm vs 9.3 +/- 2.7 mm, p < 0.0001), but the 2-mm difference of means was at the limit of imaging resolution and observer reliability. In contrast, patients with lower rates of tumor growth ( 2.5 mm/year is a better predictor of hearing loss than the initial tumor size for patients undergoing observation management of VSs < 25 mm in largest diameter.

A critical evaluation of vestibular schwannoma surgery for patients younger than 40 years of age.

BACKGROUND: There are few published prospective data sets specifically focusing on patients younger than 40 years old undergoing microsurgery for vestibular schwannoma. OBJECTIVE: We describe functional outcomes and long-term tumor control after surgery in patients younger than 40 years old enrolled in a prospectively collected database over a 25-year period. METHODS: We selected all vestibular schwannoma patients from a prospectively collected database who were younger than 40 years old at the time of surgical resection for a vestibular schwannoma. Rates of tumor control and hearing preservation were analyzed using Kaplan-Meier analysis, and risk factors for facial nerve palsy, hearing loss, and trigeminal neuropathy were analyzed using multivariate logistic regression. RESULTS: A total of 204 patients younger than 40 years of age met our inclusion criteria and were included in the analysis. Our data indicate that surgical resection leads to durable long-term freedom from tumor recurrence or progression in 89% of young patients at 15 years of follow-up. Consistent with other published series, hearing was preserved in 68% of patients with smaller tumors (<3 cm). Facial nerve function was preserved in 76% of patients with smaller tumors and 52% of patients with larger tumors (P<.001). On multivariate logistic regression, tumor size was a significant predictor of hearing loss, whereas gross total resection was nearly a significant predictor of hearing loss controlling for other variables (P=.06). CONCLUSION: We present the largest prospectively studied cohort of young patients undergoing microsurgical resection of vestibular schwannoma. These data suggest that surgical resection provides excellent long-term tumor control in these patients.

The value of intraoperative facial nerve electromyography in predicting facial nerve function after vestibular schwannoma surgery.

The prognostic significance of intraoperative facial nerve electromyography (EMG) changes is not well-established in vestibular schwannoma (VS) surgery. We studied facial nerve EMG with a threshold >0.05mA and performed subgroup analyses based on tumor size, resection approach, and extent of resection, for prediction of long-term facial nerve outcome. A total of 477 surgically treated VS patients were included. Elevated stimulation threshold exceeding >0.05mA is a highly specific (90%), but very insensitive (29%) finding in this cohort. The positive predictive value and negative predictive values (NPV) of facial nerve EMG for detection of permanent facial palsy are 68% and 63%, respectively. The NPV decreased with increasing tumor size (72% versus [vs.] 64% vs. 53%) due to the increasing prevalence of post-operative facial nerve palsy in these patients. In conclusion, while facial nerve EMG is a critical adjunct for locating the facial nerve intraoperatively, its predictive value for facial nerve function remains to be determined.