Improved preservation of hearing and facial nerve function in vestibular schwannoma surgery via the retrosigmoid approach in a series of 200 patients

Combined use of diffusion tensor tractography and multifused contrast-enhanced FIESTA for predicting facial and cochlear nerve positions in relation to vestibular schwannoma

OBJECT

The authors assessed whether the combined use of diffusion tensor tractography (DTT) and contrast-enhanced (CE) fast imaging employing steady-state acquisition (FIESTA) could improve the accuracy of predicting the courses of the facial and cochlear nerves before surgery.

METHODS

The population was composed of 22 patients with vestibular schwannoma in whom both the facial and cochlear nerves could be identified during surgery. According to DTT, depicted fibers running from the internal auditory canal to the brainstem were judged to represent the facial or vestibulocochlear nerve. With regard to imaging, the authors investigated multifused CE-FIESTA scans, in which all 3D vessel models were shown simultaneously, from various angles. The low-intensity areas running along the tumor from brainstem to the internal auditory canal were judged to represent the facial or vestibulocochlear nerve.

RESULTS

For all 22 patients, the rate of fibers depicted by DTT coinciding with the facial nerve was 13.6% (3/22), and that of fibers depicted by DTT coinciding with the cochlear nerve was 63.6% (14/22). The rate of candidates for nerves predicted by multifused CE-FIESTA coinciding with the facial nerve was 59.1% (13/22), and that of candidates for nerves predicted by multifused CE-FIESTA coinciding with the cochlear nerve was 4.5% (1/22). The rate of candidates for nerves predicted by combined DTT and multifused CE-FIESTA coinciding with the facial nerve was 63.6% (14/22), and that of candidates for nerves predicted by combined DTT and multifused CE-FIESTA coinciding with the cochlear nerve was 63.6% (14/22). The rate of candidates predicted by DTT coinciding with both facial and cochlear nerves was 0.0% (0/22), that of candidates predicted by multifused CE-FIESTA coinciding with both facial and cochlear nerves was 4.5% (1/22), and that of candidates predicted by combined DTT and multifused CE-FIESTA coinciding with both the facial and cochlear nerves was 45.5% (10/22).

CONCLUSIONS

By using a combination of DTT and multifused CE-FIESTA, the authors were able to increase the number of vestibular schwannoma patients for whom predicted results corresponded with the courses of both the facial and cochlear nerves, a result that has been considered difficult to achieve by use of a single modality only. Although the 3D image including these prediction results helped with comprehension of the 3D operative anatomy, the reliability of prediction remains to be established.

Facial Nerve Outcome after Vestibular Schwannoma Resection: A Comparative Meta-Analysis of Endoscopic versus Open Retrosigmoid Approach

The minimal access retrosigmoid endoscopic approach to vestibular schwannoma (VS) resection has been used with promising results. However, it has not been compared with the standard open approach in the literature. We performed a meta-analysis review for all articles describing both approaches for VS from 1996 to 2011. We found 1861 articles. After review and discussion, we narrowed our study to 25 articles, 4 endoscopic and 21 open. The total number of patients was 3026 for open and 790 for endoscopic. The mean tumor sizes in the open and endoscopic series were 2.5 cm and 2.7 cm, respectively. Good facial nerve outcome was achieved in 67% of the open series patients and in 94% of the endoscopic series patients. Other outcomes in the open and endoscopic series were the following: gross total resection, 91% versus 97%; functional hearing, 22.6% versus 46%; wound infection, 1.3% versus 2.6%; and recurrence, 5.4% versus 2.2%. We acknowledge the limitations of our study, but we can state that the endoscopic approach is not inferior to the standard open approach. In expert hands the endoscopic approach can offer as good a result as the open, with potential benefits such as less pain and a shorter length of stay in the hospital. There is a need for more controlled studies for a definitive comparison.

The intermedius nerve as a confounding variable for monitoring of the free-running electromyogram

OBJECTIVE

A-trains, a facial nerve EMG-pattern, are correlated with postoperative functional impairment. However, an unknown confounder is suspected to cause false positive monitoring results. The intermedius nerve contains motor fibers targeting lower facial muscles; their significance for facial nerve monitoring is yet unknown.

METHODS

Intraoperative videotapes and free-running 9-channel facial nerve EMG assessed from 87 patients undergoing surgery for vestibular schwannoma were evaluated, and presence/absence of an identifiable intermedius nerve was determined. The prognostic value of train time, a quantitative measure for A-train activity, was evaluated for both the groups with and without an identifiable intermedius nerve.

RESULTS

Correlation between traintime and outcome (Spearman's Rho) rose to 0.73 (p<0.001) when only patients without an identified intermedius nerve were considered, and fell to 0.43 (p<0.05) with the other patient group. This difference was statistically significant (p=0.036), was more prominent in the channels monitoring perioral facial muscles, and resulted from additional A-train activity in patients with an identifiable intermedius nerve.

CONCLUSIONS

A separate intermedius nerve may be more prone to manipulation, leading to A-train activity without clinical correlate, thus causing false positive monitoring results.

SIGNIFICANCE

For interpretation of the free-running EMG, the intermedius nerve needs to be taken into account as a confounder.

The extracisternal approach in vestibular schwannoma surgery and facial nerve preservation

The classical surgical technique for the resection of vestibular schwannomas (VS) has emphasized the microsurgical anatomy of cranial nerves. We believe that the focus on preservation of the arachnoid membrane may serve as a safe guide for tumor removal. Method The extracisternal approach is described in detail. We reviewed charts from 120 patients treated with this technique between 2006 and 2012. Surgical results were evaluated based on the extension of resection, tumor relapse, and facial nerve function. Results Overall gross total resection was achieved in 81% of the patients. The overall postoperative facial nerve function House-Brackmann grades I-II at one year was 93%. There was no recurrence in 4.2 years mean follow up. Conclusion The extracisternal technique differs from other surgical descriptions on the treatment of VS by not requiring the identification of the facial nerve, as long as we preserve the arachnoid envelope in the total circumference of the tumor.

Retrosigmoid removal of small acoustic neuroma: curative tumor removal with preservation of function

Object

Management of small acoustic neuromas (ANs) consists of 3 options: observation with imaging follow-up, radiosurgery, and/or tumor removal. The authors report the long-term outcomes and preservation of function after retrosigmoid tumor removal in 44 patients and clarify the management paradigm for small ANs.

Methods

A total of 44 consecutively enrolled patients with small ANs and preserved hearing underwent retrosigmoid tumor removal in an attempt to preserve hearing and facial function by use of intraoperative auditory monitoring of auditory brainstem responses (ABRs) and cochlear nerve compound action potentials (CNAPs). All patients were younger than 70 years of age, had a small AN (purely intracanalicular/cerebellopontine angle tumor ≤ 15 mm), and had serviceable hearing preoperatively. According to the guidelines of the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology–Head and Neck Surgery Foundation, preoperative hearing levels of the 44 patients were as follows: Class A, 19 patients; Class B, 17; and Class C, 8. The surgical technique for curative tumor removal with preservation of hearing and facial function included sharp dissection and debulking of the tumor, reconstruction of the internal auditory canal, and wide removal of internal auditory canal dura.

Results

For all patients, tumors were totally removed without incidence of facial palsy, death, or other complications. Total tumor removal was confirmed by the first postoperative Gd-enhanced MRI performed 12 months after surgery. Postoperative hearing levels were Class A, 5 patients; Class B, 21; Class C, 11; and Class D, 7. Postoperatively, serviceable (Class A, B, or C) and useful (Class A or B) levels of hearing were preserved for 84% and 72% of patients, respectively. Better preoperative hearing resulted in higher rates of postoperative hearing preservation (p = 0.01); preservation rates were 95% among patients with preoperative Class A hearing, 88% among Class B, and 50% among Class C. Reliable monitoring was more frequently provided by CNAPs than by ABRs (66% vs 32%, p < 0.01), and consistently reliable auditory monitoring was significantly associated with better rates of preservation of useful hearing. Long-term follow-up by MRI with Gd administration (81 ± 43 months [range 5–181 months]; median 7 years) showed no tumor recurrence, and although the preserved hearing declined minimally over the long-term postoperative follow-up period (from 39 ± 15 dB to 45 ± 11 dB in 5.1 ± 3.1 years), 80% of useful hearing and 100% of serviceable hearing remained at the same level.

Conclusions

As a result of a surgical technique that involved sharp dissection and internal auditory canal reconstruction with intraoperative auditory monitoring, retrosigmoid removal of small ANs can lead to successful curative tumor removal without long-term recurrence and with excellent functional outcome. Thus, the authors suggest that tumor removal should be the first-line management strategy for younger patients with small ANs and preserved hearing.

Preoperative identification of facial nerve in vestibular schwannomas surgery using diffusion tensor tractography

OBJECTIVE

Facial nerve palsy is a common complication of treatment for vestibular schwannoma (VS), so preserving facial nerve function is important. The preoperative visualization of the course of facial nerve in relation to VS could help prevent injury to the nerve during the surgery. In this study, we evaluate the accuracy of diffusion tensor tractography (DTT) for preoperative identification of facial nerve.

METHODS

We prospectively collected data from 11 patients with VS, who underwent preoperative DTT for facial nerve. Imaging results were correlated with intraoperative findings. Postoperative DTT was performed at postoperative 3 month. Facial nerve function was clinically evaluated according to the House-Brackmann (HB) facial nerve grading system.

RESULTS

Facial nerve courses on preoperative tractography were entirely correlated with intraoperative findings in all patients. Facial nerve was located on the anterior of the tumor surface in 5 cases, on anteroinferior in 3 cases, on anterosuperior in 2 cases, and on posteroinferior in 1 case. In postoperative facial nerve tractography, preservation of facial nerve was confirmed in all patients. No patient had severe facial paralysis at postoperative one year.

CONCLUSION

This study shows that DTT for preoperative identification of facial nerve in VS surgery could be a very accurate and useful radiological method and could help to improve facial nerve preservation.

Endoscope-assisted retrosigmoid resection of a medium size vestibular schwannoma tumor model: a cadaveric study

OBJECTIVE

To demonstrate a flexible endoscope assisted technique to perform microsurgical resection using a retrosigmoid approach of an artificial polymer tumor model that mimics a medium size (15-20mm diameter) vestibular schwannoma.

METHODS

Twelve bilateral retrosigmoid dissections were performed in 6 glutaraldehyde embalmed, colored silicone injected, adult cadaveric heads. Using a standard retrosigmoid approach, we first implanted the tumor model at the cerebellopontine angle (CPA) and then we resected the tumor under simultaneous endoscopic and microscopic visualizations. The resection was performed by first creating a corridor by removing the lower portion of the tumor and then by inserting through the same corridor the flexible endoscope mounted on a surgical instrument in order to accomplish early visualization of the VII-VIII complex. This early visualization of the VII-VIII complex made possible expeditious removal of the model with preservation of the VII-VIII complex.

RESULTS

We were able to successfully implant the artificial tumor in all the specimens. The post-tumor implantation CT scan confirmed the optimal CPA location of the model with its intra-porus extension. The exposure of the facial and the adjoining neuro-vascular structures was excellent during all stages of the surgical removal and was accomplished with minimal cerebellar retraction, under intermittent endoscopic-assisted control. Early visualization of the facial and vestibular cochlear nerves complex led to unhindered removal of the tumor model.

CONCLUSIONS

The endoscopic-assisted microsurgical removal of a tumor model simulating a medium size vestibular schwannoma was feasible in our tumor model study emulating real surgery. Visualization of the acousticofacial bundle at the early stage of the surgical removal should theoretically decrease the risk of its inadvertent injuries as well as facilitate complete removal of the tumor. Clinical studies to validate this laboratory study are necessary.

Changing times and early debates

The machine was soon being called the Gamma Knife. Its spread led to increasing numbers of papers from different centers but particularly Pittsburgh. As mentioned in the preface, the introduction of new methods in medicine is seldom without problems. There were a number of squabbles about the treatment of various indications. It was suggested that for AVMs, the GKS was unnecessary. For meningiomas, there was marked skepticism within the milieu itself in the early days. Metastases were not treated in Stockholm because of Leksell's opposition to the treatment of malignant disease, and indeed, these tumors became generally popular indications rather later. There was a thought that pituitary adenomas could be better treated with GKS but it proved too unreliable, and for these tumors, GKS remains an ancillary treatment method. The most marked disagreements were with respect of the vestibular schwannomas. This discussion continues to the present.

Contemporary surgical management of vestibular schwannomas: analysis of complications and lessons learned over the past decade

BACKGROUND

Despite advanced microsurgical techniques, more refined instrumentation, and expert team management, there is still a significant incidence of complications in vestibular schwannoma surgery.

OBJECTIVE

To analyze complications from the microsurgical treatment of vestibular schwannoma by an expert surgical team and to propose strategies for minimizing such complications.

METHODS

Surgical outcomes and complications were evaluated in a consecutive series of 410 unilateral vestibular schwannomas treated from 2000 to 2009. Clinical status and complications were assessed postoperatively (within 7 days) and at the time of follow-up (range, 1-116 months; mean, 32.7 months).

RESULTS

Follow-up data were available for 357 of the 410 patients (87.1%). Microsurgical tumor resection was performed through a retrosigmoid approach in 70.7% of cases. Thirty-three patients (8%) had intrameatal tumors and 204 (49.8%) had tumors that were <20 mm. Gross total resection was performed in 306 patients (74.6%). Hearing preservation surgery was attempted in 170 patients with tumors <20 mm, and good hearing was preserved in 74.1%. The main neurological complication was facial palsy (House-Brackmann grade III-VI), observed in 14% of patients (56 cases) postoperatively; however, 59% of them improved during the follow-up period. Other neurological complications were disequilibrium in 6.3%, facial numbness in 2.2%, and lower cranial nerve deficit in 0.5%. Nonneurological complications included cerebrospinal fluid leaks in 7.6%, wound infection in 2.2%, and meningitis in 1.7%.

CONCLUSION

Many of these complications are avoidable through further refinement of operative technique, and strategies for avoiding complications are proposed.

Surgery of the ear and the lateral skull base: pitfalls and complications

Surgery of the ear and the lateral skull base is a fascinating, yet challenging field in otorhinolaryngology. A thorough knowledge of the associated complications and pitfalls is indispensable for the surgeon, not only to provide the best possible care to his patients, but also to further improve his surgical skills. Following a summary about general aspects in pre-, intra-and postoperative care of patients with disorders of the ear/lateral skull base, this article covers the most common pitfalls and complications in stapes surgery, cochlear implantation and surgery of vestibular schwannomas and jugulotympanal paragangliomas. Based on these exemplary procedures, basic "dos and don'ts" of skull base surgery are explained, which the reader can easily transfer to other disorders. Special emphasis is laid on functional aspects, such as hearing, balance and facial nerve function. Furthermore, the topics of infection, bleeding, skull base defects, quality of life and indication for revision surgery are discussed. An open communication about complications and pitfalls in ear/lateral skull base surgery among surgeons is a prerequisite for the further advancement of this fascinating field in ENT surgery. This article is meant to be a contribution to this process.

Facial nerve preservation with preoperative identification and intraoperative monitoring in large vestibular schwannoma surgery

BACKGROUND

Microsurgery is an option of choice for large vestibular schwannomas (VSs). Anatomical and functional preservation of facial nerve (FN) is still a challenge in these surgeries. FNs are often displaced and morphologically changed by large VSs. Preoperative identification of FN with magnetic resonance (MR) diffusion tensor tracking (DTT) and intraoperative identification with facial electromyography (EMG) may be desirable for improving functional results of FN.

METHOD

In this retrospective study, eight consecutive cases with large VS (≥30 mm in maximal extrameatal diameter) were retrospectively studied. FN DTT was performed in each case preoperatively. All the cases underwent microsurgical resection of the tumor with intraoperative FN EMG monitoring. Correctness of prediction for FN location by DTT was verified by the surgeon's inspection. Postoperative FN function of each patient was followed up.

RESULTS

Preoperative identification of FN was possible in 7 of 8 (87.5 %) cases. FN location predicted by preoperative DTT agreed to surgical finding in all the 7 cases. FN EMG was helpful to locate and protect the FN. Total resection was achieved in 7 of 8 (87.5 %). All FNs were anatomically preserved. All cases had excellent facial nerve function (House-Brackmann Grade I-II).

CONCLUSIONS

FN DTT is a powerful technique in preoperatively identification of FN in large VS cases. Continuous intraoperative FN EMG monitoring is contributive to locating and protecting FNs. Radical resection of large VSs as well as favorable postoperative FN outcome is available with application of these techniques.

Long-term hearing outcome after retrosigmoid removal of vestibular schwannoma

Although many investigators have reported the hearing function in the immediate postoperative period in patients with vestibular schwannoma (VS), little is known about the long-term outcomes of the postoperative hearing. The aim of this study was to analyze the long-term hearing outcomes at a mean follow-up of 5 years in patients with unilateral VS treated via the retrosigmoid approach. Twenty-four patients with immediate postoperative serviceable hearing who underwent repeated audiogram or phone interview were included in this study. During the mean follow-up period (68.8 ± 30.2 months, range 14–123 months), serviceable hearing was preserved in 20 out of the 24 patients (83%). Pure tone average (PTA) was reevaluated within 6 months in seven patients. In the two patients whose PTA deteriorated ≥ 5 dB in 6 months after surgery, their PTA worsened ≥ 15 dB compared to the immediate postoperative PTA. In the remaining five patients whose PTA deteriorated < 5 dB in 6 months after surgery, PTA was maintained within a 15-dB deterioration at the final follow-up (p = 0.04, Fisher's exact test). According to Kaplan–Meier survival plots, the 5-year or 7-year preservation rate of serviceable hearing was 86.2% or 71.8%, respectively. Further study will be needed to clarify the mechanism underlying the long-term decline of serviceable hearing; however, the deterioration of PTA in the early postoperative period may help to predict the long-term outcomes of hearing.

Fluid-fluid level in cystic vestibular schwannoma: a predictor of peritumoral adhesion

OBJECT

The aim of this study was to evaluate the clinical results and surgical outcomes of cystic vestibular schwannomas (VSs) with fluid-fluid levels.

METHODS

Forty-five patients with cystic VSs and 86 with solid VSs were enrolled in the study. The patients in the cystic VSs were further divided into those with and without fluid-fluid levels. The clinical and neuroimaging features, intraoperative findings, and surgical outcomes of the 3 groups were retrospectively compared.

RESULTS

Peritumoral adhesion was significantly greater in the fluid-level group (70.8%) than in the nonfluid-level group (28.6%) and the solid group (25.6%; p < 0.0001). Complete removal of the VS occurred significantly less in the fluid-level group (45.8%, 11/24) than in the nonfluid-level group (76.2%, 16/21) and the solid group (75.6%, 65/86; p = 0.015). Postoperative facial nerve function in the fluid-level group was less favorable than in the other 2 groups; good/satisfactory facial nerve function 1 year after surgery was noted in 50.0% cases in the fluid-level group compared with 83.3% cases in the nonfluid-level group (p = 0.038).

CONCLUSIONS

Cystic VSs with fluid-fluid levels more frequently adhered to surrounding neurovascular structures and had a less favorable surgical outcome. A possible mechanism of peritumoral adhesion is intratumoral hemorrhage and consequent inflammatory reactions that lead to destruction of the tumor-nerve barrier. These findings may be useful in predicting surgical outcome and planning surgical strategy preoperatively.

Radiological and Clinical Factors Predicting the Facial Nerve Outcome following Retrosigmoid Approach for Large Vestibular Schwannomas (VSs)

Objective The aim of our study was to identify the radiological and clinical factors that predict postoperative facial nerve outcome following retrosigmoid approach for large vestibular schwannomas (VSs). Methods A total of 72 patients with large (≥ 3 cm) vestibular schwannomas was included in this retrospective study. Various parameters evaluated were age, gender, clinical presentation, tumor diameter in three planes, intrameatal extension, and pattern of growth. Results Age of the patient and presenting symptoms such as headache, ataxia, or preoperative facial nerve dysfunction correlated with poorer facial nerve outcome (p < 0.05). Patients with larger tumor volumes and extrameatal growth experienced a worse outcome (p < 0.05). Anterior and caudal extension (p = 0.001) correlated with poorer outcome, as well. Intrameatal extension and bony changes of the internal acoustic meatus did not correlate with the outcome (p > 0.05). Of the various examined factors, preoperative facial nerve function independently predicted postoperative facial nerve outcome. Conclusion Our study suggests that young patients with small tumor volume and normal facial nerve function at presentation are more likely to experience a good postoperative facial nerve outcome. These clinical and radiological parameters can be used to predict facial nerve outcome prior to surgery.

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.

Facial nerve schwannoma arising from the cerebellopontine angle

A 74-year-old female suffered hearing disturbance in the right ear persisting for several years, followed by sudden onset of right facial nerve palsy. Her symptoms gradually worsened and neuroradiological imaging revealed a 4-cm cerebellopontine angle (CPA) tumor. Intraoperatively, the tumor was found to originate from the facial nerve. Total removal of the tumor was achieved, followed by a split hypoglossal-facial nerve anastomosis. Facial nerve schwannomas are rare and extremely difficult to preoperatively distinguish from vestibular schwannomas, especially if arising from the CPA and the internal auditory canal. However, preoperative diagnosis of facial nerve schwannomas is important because functional preservation of the facial nerve is more challenging than for vestibular schwannomas. Facial nerve palsy is one of the most unique symptoms in patients with facial nerve schwannomas, but is rare with vestibular schwannomas. Facial nerve schwannomas should be included in the differential diagnosis of CPA tumors with atypical clinical manifestations, and patients should be informed before surgery of the possibility of facial nerve dysfunction and the consequent need for facial nerve graft or reconstruction.

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.

An update on unilateral sporadic small vestibular schwannoma

Advances in neuroimaging have increased the detection rate of small vestibular schwannomas (VSs, maximum diameter < 25 mm). Current management modalities include observation with serial imaging, stereotactic radiosurgery, and microsurgical resection. Selecting one approach over another invites speculation, and no standard management consensus has been established. Moreover, there is a distinct clinical heterogeneity among patients harboring small VSs, making standardization of management difficult. The aim of this article is to guide treating physicians toward the most plausible therapeutic option based on etiopathogenesis and the highest level of existing evidence specific to the different cohorts of hypothetical case scenarios. Hypothetical cases were created to represent 5 commonly encountered scenarios involving patients with sporadic unilateral small VSs, and the literature was reviewed with a focus on small VS. The authors extrapolated from the data to the hypothetical case scenarios, and based on the level of evidence, they discuss the most suitable patient-specific treatment strategies. They conclude that observation and imaging, stereotactic radiosurgery, and microsurgery are all important components of the management strategy. Each has unique advantages and disadvantages best suited to certain clinical scenarios. The treatment of small VS should always be tailored to the clinical, personal, and social requirements of an individual patient, and a rigid treatment protocol is not practical.

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.

Clinical features of intracranial vestibular schwannomas

The aim of the present study was to discuss the clinical features of intracranial vestibular schwannomas and to evaluate the symptoms and signs as well as their correlation with tumor extension. The records of 1,009 patients who were treated in Shanghai Huashan Hospital were reviewed retrospectively. According to the Samii classification of 1997, the patients were grouped into a T3 and a T4 group based on the radiological findings. We focused our analysis on the incidence of subjective disturbances versus objective morbidity, and symptomatology versus tumor size and extension. Of the 1,009 cases, 424 patients (42.0%) were defined as T3 while 585 patients (58%) were defined as T4. The most frequent clinical symptoms were hearing loss (85.8%), facial numbness (48.9%), ataxia (44.6%), tinnitus (40.1%), deafness (26.3%) and facial paralysis (21.1%). The ratios of gender, vertigo and facial paralysis were significantly different between the T3 and T4 groups (P<0.05); however, none of the clinical symptoms had a positive likelihood ratio (PLR) greater than 10 for T4 prediction. The most frequent cranial nerve disturbance was associated with the cochlear nerve (92.6%) and trigeminal nerve (53.5%). Disturbance of the facial nerve was more severe in T3 than T4 patients (P<0.05). Hearing deficit, facial paresthesia, ataxia and tinnitus are key symptoms of huge vestibular schwannomas. Cochlear, trigeminal and facial nerves were the most commonly affected cranial nerves in cases of large tumors. Gender and tumor size were associated with tumor extension. Although the predictive value was limited, the symptoms of vertigo, facial paralysis and hearing loss may be indicators of tumor growth.

Assessment of antiangiogenic effect of imatinib mesylate on vestibular schwannoma tumors using in vivo corneal angiogenesis assay

Object

Angiogenesis and the platelet-derived growth factor (PDGF) pathway are active in the pathogenesis of vestibular schwannomas (VSs). The purpose of this study was to test whether imatinib mesylate (Gleevec), a PDGF receptor (PDGFR) blocker, reduces angiogenic capacity in sporadic VS and in VS associated with neurofibromatosis Type 2 (NF2) using a corneal angiogenesis assay.

Methods

From 121 VS tissue samples stored in the tumor bank at the Marmara University Institute of Neurological Sciences, 10 samples (6 from sporadic cases, 4 from NF2-associated cases) were selected at random for use in this study. Expression of PDGF-A and PDGF-B and their receptors was evaluated in sporadic and NF2-associated VS as well as in glioblastoma (GBM) and normal brain tissue by means of immunohistochemistry and Western blot analysis. Corneal angiogenesis assay was then used to evaluate the angiogenic capacity of tissue specimens from sporadic and NF2-associated VS with and without imatinib treatment as well as positive and negative controls (GBM and normal brain tissue).

Results

The angiogenic potential of the sporadic and NF2-associated VS tumor tissue differed significantly from that of the positive and negative control tissues (p <0.05). Furthermore, NF2-associated VS showed significantly lower angiogenic potential than sporadic VS (p <0.05). Imatinib treatment significantly reduced the angiogenic potential in both the sporadic VS and the NF2-associated VS groups. The level of PDGF-A and PDGFR-α as well as PDGF-B and PDGFR-β expression in sporadic VS and NF2-associated VS also differed significantly (p <0.05) from the levels in controls. Additionally the level of PDGFR-β was significantly higher in sporadic VS than in NF2-associated VS (p <0.05).

Conclusions

The findings of this study indicate that NF2-associated VS has significantly more angiogenic potential than sporadic VS and normal brain tissue. Additionally, imatinib reduces the angiogenic activity of both sporadic and NF2-associated VS. The authors conclude that imatinib may be a potential treatment for VS, especially for NF2-associated lesions that cannot be cured with resection or radiosurgery.

Neuroanatomical correlation of the House-Brackmann grading system in the microsurgical treatment of vestibular schwannoma

Avoidance of facial nerve injury is one of the major goals of vestibular schwannoma (VS) surgery because functional deficits of the facial nerve can lead to physical, cosmetic, and psychological consequences for patients. Clinically, facial nerve function is assessed using the House-Brackmann grading scale, which also allows physicians to track the progress of a patient's facial nerve recovery. Because the facial nerve is a peripheral nerve, it has the ability to regenerate, and the extent of its functional recovery depends largely on the location and nature of its injury. In this report, the authors first describe the facial nerve anatomy, the House-Brackmann grading system, and factors known to be predictors of postoperative facial nerve outcome. The mechanisms and pathophysiology of facial nerve injury during VS surgery are then discussed, as well as factors affecting facial nerve regeneration after surgery.

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.

Do cystic vestibular schwannomas have worse surgical outcomes? Systematic analysis of the literature

Object

The goal of this study was to perform a systematic quantitative comparison of the surgical outcomes between cystic vestibular schwannomas (CVSs) and solid vestibular schwannomas (SVSs).

Methods

A review of English-language literature published between 1990 and 2011 was performed using various search engines including PubMed, Google Scholar, and the Cochrane database. Only studies that reported surgical results of CVSs in comparison with SVSs were included in the analysis. The primary end point of this study was surgical outcomes, defined by the following: 1) facial nerve outcomes at latest follow-up; 2) mortality rates; or 3) non–facial nerve complication index. Secondary end points included extent of resection and brainstem adherence.

Results

Nine studies comprising 428 CVSs and 1287 SVSs were included in the study. The mean age of patients undergoing surgery was 48.3 ± 6.75 and 47.1 ± 9 years for CVSs and SVSs, respectively (p = 0.8). The mean tumor diameter for CVSs was 3.9 ± 0.84 cm and that for SVSs was 3.7 ± 1.2 cm (p = 0.7). There was no significant difference in the extent of resection among CVSs and SVSs (81.2% vs 80.7%, p = 0.87) Facial nerve outcomes were significantly better in the cohort of patients with SVSs than in those with CVSs (52.1% vs 39%, p = 0.0001). The perioperative mortality rates for CVSs and SVSs were not significantly different (3% and 3.8%, respectively; p = 0.6). No significant difference was noted between the cumulative non–facial nerve complication rate (including mortality) among patients with CVSs and SVSs (24.5% and 25.6%, respectively; p = 0.75)

Conclusions

Facial nerve outcomes are worse in patients undergoing resection for CVSs than in patients undergoing resection for SVSs. There were no significant differences in the extent of resection or postoperative morbidity and mortality rates between the cohorts of patients with vestibular schwannomas.

Technical nuances of resection of giant (> 5 cm) vestibular schwannomas: pearls for success

Removal of vestibular schwannomas (VSs, or acoustic neuromas) remains one of the most challenging operations in neurosurgery. Giant or huge tumors (> 5 cm) heighten these challenges, and technical nuances play a special role in maximizing tumor resection while minimizing complications. In this article, the senior author describes his technical experience with microsurgical excision of giant VSs. The accompanying video further illustrates these details.

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.

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.

Facial nerve damage following surgery for cerebellopontine angle tumours. Prevention and comprehensive treatment

Facial nerve (CN VII) palsy or even its transient paresis causes physical disability but is also a psychosocial problem. Immediately after vestibular schwannoma removal, different degrees of CN VII paresis occur in 20-70% of patients. Facial nerve paresis is observed in 10-40% after surgery of cerebellopontine angle meningiomas. Postoperative facial nerve weakness significantly reduces or completely withdraws with time in the majority of cases. However, even if prognosis for CN VII regeneration is good, proper management is needed because of the potential for serious ophthalmic complications. In this paper, the authors raise the issue of perioperative prophylaxis and comprehensive treatment of postoperative paresis of CN VII. Prophylaxis and treatment of ophthalmic complications are discussed. Current trends in the treatment of intraoperative loss of facial nerve continuity, management of facial paresis with good prognosis and dealing with facial palsy with no spontaneous recovery are also described in the paper.

Surgical treatment of patients with vestibular schwannomas after failed previous radiosurgery

OBJECT

An increasing number of patients with vestibular schwannomas (VSs) are being treated with radiosurgery. Treatment failure or secondary regrowth after radiosurgery, however, has been observed in 2%-9% of patients. In large tumors that compress the brainstem and in patients who experience rapid neurological deterioration, surgical removal is the only reasonable management option.

METHODS

The authors evaluated the relevance of previous radiosurgery for the outcome of surgery in a series of 28 patients with VS. The cohort was further subdivided into Group A (radiosurgery prior to surgery) and Group B (partial tumor removal followed by radiosurgery prior to current surgery). The functional and general outcomes in these 2 groups were compared with those in a control group (no previous treatment, matched characteristics). RESULTS There were 15 patients in Group A, 13 in Group B, and 30 in the control group. The indications for surgery were sustained tumor enlargement and progression of neurological symptoms in 12 patients, sustained tumor enlargement in 15 patients, and worsening of neurological symptoms without evidence of tumor growth in 1 patient. Total tumor removal was achieved in all patients in Groups A and B and in 96.7% of those in the control group. There were no deaths in any group. Although no significant differences in the neurological morbidity or complication rates after surgery were noted, the risk of new cranial nerve deficits and CSF leakage was highest in patients in Group B. Patients who underwent previous radiosurgical treatment (Groups A and B) tended to be at higher risk of developing postoperative hematomas in the tumor bed or cerebellum. The rate of facial nerve anatomical preservation was highest in those patients who were not treated previously (93.3%) and decreased to 86.7% in the patients in Group A and to 61.5% in those in Group B. Facial nerve function at follow-up was found to correlate to the previous treatment; excellent or good function was seen in 87% of the patients from the control group, 78% of those in Group A, and 68% of those in Group B.

CONCLUSIONS

Complete microsurgical removal of VSs after failed radiosurgery is possible with an acceptable morbidity rate. The functional outcome, however, tends to be worse than in nontreated patients. Surgery after previous partial tumor removal and radiosurgery is most challenging and related to worse outcome.

Stage II vestibular schwannoma: predictive factors for postoperative hearing loss and facial palsy

OBJECTIVES

To assess predictive factors for deafness and facial palsy after vestibular schwannoma surgery on a translabyrinthine or retrolabyrinthine approach, and to compare sequela results to those for gamma knife radiosurgery.

PATIENTS AND METHODS

A retrospective study included 70 patients operated on for stage II vestibular schwannoma (Koos classification). Postoperative hearing was assessed on pure-tone average and speech discrimination score, and facial palsy on the House and Brackmann classification, preoperatively and at 1 year postoperatively. Various predictive factors were assessed for both. Statistical analysis used the Fischer exact test, with a significance threshold of P<0.05.

RESULTS

Hearing was conserved in 18.9% of patients operated on with a retrolabyrinthine approach, with 8.1% conserving useful hearing. Facial function was conserved in 91.4%. Predictive factors for hearing conservation did not achieve statistical significance, but showed trends for: preoperative pure-tone average threshold≤30dB and speech discrimination score≥ 70%, age less than 55 years, tinnitus, nearly normal auditory brainstem response (ABR) latency, and homogeneous tumor on MRI. Predictive factors for conserved facial function likewise did not achieve statistical significance, but showed trends for: age less than 55 years, deafness of progressive onset, absence of cardiovascular risk factors, nearly normal ABR latency and tumor size<13.5mm on MRI.

CONCLUSION

Facial nerve risk is largely the same with surgery or gamma knife radiosurgery. Concerning hearing, gamma knife radiosurgery seems to provide better hearing conservation, but only over the short term.

Diffusion tensor imaging–based fiber tracking for prediction of the position of the facial nerve in relation to large vestibular schwannomas

Object

The reliable preoperative visualization of facial nerve location in relation to vestibular schwannoma (VS) would allow surgeons to plan tumor removal accordingly and may increase the safety of surgery. In this prospective study, the authors attempted to validate the reliability of facial nerve diffusion tensor (DT) imaging–based fiber tracking in a series of patients with large VSs. Furthermore, the authors evaluated the potential of this visualization technique to predict the morphological shape of the facial nerve (tumor compression–related flattening of the nerve).

Methods

Diffusion tensor imaging and anatomical images (constructive interference in steady state) were acquired in a series of 22 consecutive patients with large VSs and postprocessed with navigational software to obtain facial nerve fiber tracking. The location of the cerebellopontine angle (CPA) part of the nerve in relation to the tumor was recorded during surgery by the surgeon, who was blinded to the results of the fiber tracking. A correlative analysis was performed of the imaging-based location of the nerve compared with its in situ position in relation to the VS.

Results

Fibers corresponding to the anatomical location and course of the facial nerve from the brainstem to the internal auditory meatus were identified with the DT imaging–based fiber tracking technique in all 22 cases. The location of the CPA segment of the facial nerve in relation to the VS determined during surgery corresponded to the location of the fibers, predicted by the DT imaging–based fiber tracking, in 20 (90.9%) of the 22 patients. No DT imaging–based fiber tracking correlates were found with the 2 morphological types of the nerve (compact or flat).

Conclusions

The current study of patients with large VSs has shown that the position of the facial nerve in relation to the tumor can be predicted reliably (in 91%) using DT imaging–based fiber tracking. These are preliminary results that need further verification in a larger series.

Petrous bone pneumatization is a risk factor for cerebrospinal fluid fistula following vestibular schwannoma surgery

BACKGROUND

For the prevention of postoperative CSF fistula a better understanding of origins and risk factors is necessary.

OBJECTIVE

To identify the petrous bone air cell volume as a risk factor for developing CSF fistula, we performed a retrospective analysis.

METHODS

From 2000 to 2007 519 patients had a retrosigmoidal surgical removal of a vestibular schwannoma. The 22 who had a postoperative CSF fistula were chosen for evaluation in addition to 78 patients who were randomly selected in 4 equally sized cohorts: male/female with small/large tumors. Preoperative CT scans were analyzed regarding petrous bone air cell volume, area of visible pneumatization at the level of the internal auditory canal (IAC), tumor grade, and sex.

RESULTS

: Women developed nearly half as many CSF fistulas (2.7%) as men (5.2%). The mean volume of the petrous bone air cells was 10.97 mL (SD, 4.9; range, 1.38-27.25). It was significantly lower for women (mean, 9.23 mL; SD, 3.8) than for men (mean, 12.5 mL; SD, 5.28; P = .0008). The mean air cell volume of CSF-fistula patients was 13.72 mL (SD, 5.22). The difference concerning the air cell volume between patients who developed CSF fistulas and patients from the control group was significant (P = .0042). There was a significant positive correlation between the air cell volume and the area of pneumatization in one CT slide at the level of the IAC.

CONCLUSION

The higher incidence of CSF fistulas in men compared with women can be explained by means of differently pneumatized petrous bones. A high amount of petrous bone pneumatization has to be considered as a risk factor for the development of postoperative CSF fistula after vestibular schwannoma surgery.

How obliteration of petrosal air cells by vestibular schwannoma influences the risk of postoperative CSF fistula

INTRODUCTION

For postoperative CSF-fistula prevention a better understanding of its origins and risk factors is necessary. To identify the role of the tumor growth for the risk to develop CSF-fistula we performed a retrospective analysis.

METHODS

519 patients between the years 2000 and 2007 had a retrosigmoidal surgical removal of vestibular schwannoma in a standardized procedure. 22 CSF-fistula-patients were chosen for evaluation. 78 patients were randomly selected as control group in four equally sized cohorts: male/female with small/large tumors. Preoperative CT-scans were analyzed regarding IAC-length, diameter of the IAC porus (IAP), tumor size and pneumatization of the posterior wall (PW) of the IAC.

RESULTS

The mean length of the IAC was 1.2 cm, SD 0.17. There was a significant difference between the diameter of the IAP in cases of small tumors and those of large tumors. Patients with small tumors also showed a larger fraction with visible pneumatization of the PW (34.88%) in the CT-scan than patients with large tumors (24.07%). There is a positive correlation between tumor grade and diameter of the IAP. At the same time there is an inverse correlation between tumor grade and pneumatization of the PW.

CONCLUSIONS

Widening of the IAC by tumor growth may leads to obliteration of air cells in the PW and therefore can be protective concerning CSF-fistula. At the same time patients with small tumors and a visible pneumatization in the PW must be expected to have a higher risk of CSF-fistula.