Middle fossa versus retrosigmoid-transmeatal approach in vestibular schwannoma surgery: a prospective study

Retrosigmoid versus middle fossa approach for hearing and facial nerve preservation in vestibular schwannoma surgery: A systematic review and comparative meta-analysis

BACKGROUND

Vestibular schwannomas (VS) are benign tumors arising from vestibular nerve's Schwann cells. Surgical resection via retrosigmoid (RS) or middle fossa (MF) is standard, but the optimal approach remains debated. This meta-analysis evaluated RS and MF approaches for VS management, emphasizing hearing preservation and Cranial nerve seven (CN VII) outcomes stratified by tumor size.

METHODS

Systematic searches across PubMed, Cochrane, Web of Science, and Embase identified relevant studies. Hearing and CN VII outcomes were gauged using the American Academy of Otolaryngology-Head and Neck Surgery, Gardner Robertson, and House-Brackmann scores.

RESULTS

Among 7228 patients, 56 % underwent RS and 44 % MF. For intracanalicular tumors, MF recorded 38 % hearing loss, compared to RS's 54 %. In small tumors (<1.5 cm), MF showed 41 % hearing loss, contrasting RS's lower 15 %. Medium-sized tumors (1.5 cm-2.9 cm) revealed 68 % hearing loss in MF and 55 % in RS. Large tumors (>3cm) were only reported in RS with a hearing loss rate of 62 %.

CONCLUSION

Conclusively, while MF may be preferable for intracanalicular tumors, RS demonstrated superior hearing preservation for small to medium-sized tumors. This research underlines the significance of stratified outcomes by tumor size, guiding surgical decisions and enhancing patient outcomes.

Brazilian Society of Otology task force - Vestibular Schwannoma ‒ evaluation and treatment

OBJECTIVE

To review the literature on the diagnosis and treatment of vestibular schwannoma.

METHODS

Task force members were educated on knowledge synthesis methods, including electronic database search, review and selection of relevant citations, and critical appraisal of selected studies. Articles written in English or Portuguese on vestibular schwannoma were eligible for inclusion. The American College of Physicians' guideline grading system and the American Thyroid Association's guideline criteria were used for critical appraisal of evidence and recommendations for therapeutic interventions.

RESULTS

The topics were divided into 2 parts: (1) Diagnosis - audiologic, electrophysiologic tests, and imaging; (2) Treatment - wait and scan protocols, surgery, radiosurgery/radiotherapy, and systemic therapy.

CONCLUSIONS

Decision making in VS treatment has become more challenging. MRI can diagnose increasingly smaller tumors, which has disastrous consequences for the patients and their families. It is important to develop an individualized approach for each case, which highly depends on the experience of each surgical team.

Clinical Studies and Pre-clinical Animal Models on Facial Nerve Preservation, Reconstruction, and Regeneration Following Cerebellopontine Angle Tumor Surgery-A Systematic Review and Future Perspectives

Background and purpose: Tumorous lesions developing in the cerebellopontine angle (CPA) get into close contact with the 1st (cisternal) and 2nd (meatal) intra-arachnoidal portion of the facial nerve (FN). When surgical damage occurs, commonly known reconstruction strategies are often associated with poor functional recovery. This article aims to provide a systematic overview for translational research by establishing the current evidence on available clinical studies and experimental models reporting on intracranial FN injury.

Methods: A systematic literature search of several databases (PubMed, EMBASE, Medline) was performed prior to July 2020. Suitable articles were selected based on predefined eligibility criteria following the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines. Included clinical studies were reviewed and categorized according to the pathology and surgical resection strategy, and experimental studies according to the animal. For anatomical study purposes, perfusion-fixed adult New Zealand white rabbits were used for radiological high-resolution imaging and anatomical dissection of the CPA and periotic skull base.

Results: One hundred forty four out of 166 included publications were clinical studies reporting on FN outcomes after CPA-tumor surgery in 19,136 patients. During CPA-tumor surgery, the specific vulnerability of the intracranial FN to stretching and compression more likely leads to neurapraxia or axonotmesis than neurotmesis. Severe FN palsy was reported in 7 to 15 % after vestibular schwannoma surgery, and 6% following the resection of CPA-meningioma. Twenty-two papers reported on experimental studies, out of which only 6 specifically used intracranial FN injury in a rodent (n = 4) or non-rodent model (n = 2). Rats and rabbits offer a feasible model for manipulation of the FN in the CPA, the latter was further confirmed in our study covering the radiological and anatomical analysis of perfusion fixed periotic bones.

Conclusion: The particular anatomical and physiological features of the intracranial FN warrant a distinguishment of experimental models for intracranial FN injuries. New Zealand White rabbits might be a very cost-effective and valuable option to test new experimental approaches for intracranial FN regeneration. Flexible and bioactive biomaterials, commonly used in skull base surgery, endowed with trophic and topographical functions, should address the specific needs of intracranial FN injuries.

Facial Nerve Outcomes After Vestibular Schwannoma Microsurgical Resection in Neurofibromatosis Type 2

OBJECTIVE

The aim of this study is to investigate facial nerve outcomes after microsurgical resection in neurofibromatosis type 2 (NF2) compared to sporadic tumors.

STUDY DESIGN

Single institutional retrospective chart review.

SETTING

Tertiary referral center.

METHODS

All adult patients with NF2 vestibular schwannoma (VS) or sporadic VS who underwent microsurgical resection from 2008 to 2019 with preoperative magnetic resonance imaging (MRI) and 1 year of postsurgical follow-up were included. The primary outcome measure was postoperative House-Brackmann (HB) facial nerve score measured at first postoperative visit and after at least 10 months.

RESULTS

In total, 161 sporadic VSs and 14 NF2 VSs met inclusion criteria. Both median tumor diameter (NF2, 33.5 mm vs sporadic, 24 mm, P = .0011) and median tumor volume (NF2, 12.4 cm³ vs sporadic, 2.9 cm³, P = .0005) were significantly greater in patients with NF2. The median follow-up was 24.9 months (range, 12-130.1). Median facial nerve function after 1 year for patients with NF2 was HB 3 (range, 1-6) compared to HB 1 (range, 1-6) for sporadic VS (P = .001). With multivariate logistic regression, NF2 tumors (odds ratio [OR] = 13.9, P = .001) and tumor volume ≥3 cm³ (OR = 3.6, P = .025) were significantly associated with HB ≥3 when controlling for age, sex, extent of tumor resection, translabyrinthine approach, and prior radiation.

CONCLUSION

Tumor volume >3 cm³ and NF2 tumors are associated with poorer facial nerve outcomes 1 year following microsurgical resection.

Cochlear Patency after Translabyrinthine and Retrosigmoid Vestibular Schwannoma Surgery

OBJECTIVES

To assess the incidence and onset of cochlear obliteration after translabyrinthine and retrosigmoid vestibular schwannoma surgery.

MATERIALS AND METHODS

We retrospectively identified a consecutive series of eighty ears in eighty vestibular schwannoma patients who were treated via a translabyrinthine or retrosigmoid approach by a single neuro-otological surgical team in a tertiary referral center from May 2011 to January 2018. Postoperative, high- resolution T2-weighted turbo spin echo three-dimensional magnetic resonance (MR) images of the posterior fossa were evaluated at the level of the membranous labyrinth and internal auditory canal. Perilymphatic patency of the vestibule, basal, and apical cochlear turns were scored and classified as patent, hypointense, partially obliterated, or completely obliterated.

RESULTS

Twenty-five vestibular schwannomas were treated with surgery via a translabyrinthine approach, and fifty-five were treated using a retrosigmoid approach; of these, 8% and 65%, respectively, showed no signs of perilymphatic alterations in the basal or apical turns, while 84% and 20%, respectively, showed partial or complete obliteration in the basal or apical turns with a mean postoperative interval of 127 and 140 days, respectively. All the patients who underwent multiple MR scans and had a completely patent perilymphatic system on the first postoperative scan remained patent during subsequent scans; 16% of the patients showed worsened perilymphatic appearance. The onset of cochlear obliteration occurred within 2-7 months in most translabyrinthine patients.

CONCLUSION

These findings may support the need for simultaneous cochlear electrode or dummy implantation in translabyrinthine surgery. Second-stage implantation could be feasible in cases where a retrosigmoid approach is used; however, the implantation should be considered within the initial months to avoid cochlear obliteration. Findings on the first postoperative MR could indicate the need for intensified MR follow-up and may even predict the occurrence of cochlear obliteration.

Prognostic Significance of Preoperative Geometric Changes in the Internal Acoustic Canal for Hearing Preservation in Vestibular Schwannoma Surgery

OBJECTIVE

This study focused on the changes in the internal acoustic canal (IAC) caused by vestibular schwannomas (VSs) and their prognostic significance for postoperative hearing outcome.

METHODS

A total of 125 consecutive cases of VS were included. We used a neuronavigation software to perform the following measurements on both the tumor side and healthy side: volume of the IAC (VIAC), maximal diameter of the IAC (DIAC), and length of the IAC (LIAC). A statistical analysis was realized using Spearman correlation to test the correlation of the morphometric measure of the IAC and postoperative hearing. Multivariate analysis was performed to test the impact of measurements of the IAC and preoperative hearing on postoperative hearing.

RESULTS

The mean VIAC on the tumor side and on the healthy side was 0.271 and 0.169 cm³, respectively. The mean DIAC was 9.438 mm on the tumor side and 7.034 mm contralateral. The correlations tests showed significant correlations of both postoperative hearing deficit and degree of hearing loss with 1) VIAC on the tumor side, 2) difference between VIAC on the tumor side and healthy side, 3) DIAC on the tumor side, and 4) difference between the DIAC on the tumor side and healthy side. The multivariate analysis showed significant impact of the DIAC (P = 0.01) and preoperative hearing status (P = 0.02) on postoperative hearing.

CONCLUSIONS

Enlargement of the VIAC and DIAC are negative prognostic factors for hearing preservation. Reasons may be long-standing compression of the auditory nerve and an increased vulnerability of the inner ear structures during the drilling of the IAC.

The Feasibility of a Modified Exclusive Endoscopic Transcanal Transpromontorial Approach for Vestibular Schwannomas

Objective  We evaluated the feasibility of an exclusive endoscopic transcanal transpromontorial approach (EETTA) for the treatment of small vestibular schwannomas (VSs) limited to the internal auditory canal (IAC), and introduced a modification without external auditory canal closure.

Methods  Between June 2016 and June 2017, seven patients with VS underwent surgery using a modified EETTA. Treatment outcomes, including efficacy of tumor resection, preservation of function, operation time, and quality of life (QOL), were evaluated.

Results  The patients preoperatively exhibited Koos Grade I/II tumors and severe-to-profound hearing loss. Gross total resection was accomplished in all cases. There were no major complications, and all patients exhibited normal facial nerve function immediately after surgery. The mean follow-up period was 12.9 months. The operation time (average 196.3 ± 64.9 minutes) and hospitalization period (average 7.4 ± 1.0 days) were favorable. Short Form-36 scores for QOL showed unremarkable results compared with previous reports.

Conclusions  The modified EETTA was effective in the removal of VSs in the IAC. It can be an alternative surgical option for small VSs.

Middle Fossa Approach for Resection of Vestibular Schwannomas: A Decade of Experience

BACKGROUND

The middle cranial fossa (MCF) approach is a challenging surgical technique for the resection of small and intermediate sized, primarily intracanalicular, vestibular schwannomas (VS), with the goal of hearing preservation (HP).

OBJECTIVE

To describe a decade-long, single institutional experience with the MCF approach for resection of VS.

METHODS

This is a retrospective cohort study of 63 patients who underwent the MCF approach for resection of VS from 2006 to 2016. Audiometric data included pure-tone average (PTA), low-tone pure-tone average (LtPTA), word recognition score, and American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) hearing classification at presentation and follow-up. Patients with postoperative serviceable (AAO-HNS class A-B) and/or useful (AAO-HNS class A-C) hearing were compared to those without HP. Facial nerve function was assessed using the House–Brackmann scale.

RESULTS

The mean age and duration of follow-up were 50 ± 13 yr and 21 ± 21 mo, respectively. The mean tumor size was 10 ± 4 mm. The serviceable and usable HP rates were 54% and 50%, respectively. Some residual hearing was preserved in 71% of patients. Large tumor size (P = .05), volume (P = .03), and extrameatal tumor extension (P = .03) were associated with poor audiometric outcomes. The presence of a fundal fluid cap (P = .01) was a favorable finding. At definitive testing, LtPTA was significantly better preserved than traditional PTA (P = .01). Facial nerve outcomes, tumor control rates, and durability of audiometric outcomes were excellent. 47% of patients pursued aural rehabilitation.

CONCLUSION

In our series, the MCF approach for VS provided excellent rates of tumor and facial nerve function, with durable serviceable HP.

Revision Surgery for Vestibular Schwannomas

Objectives  To describe clinical outcomes of patients undergoing revision surgery for vestibular schwannomas. Design  Retrospective case series. Setting  Tertiary private neurotologic practice. Participants  Patients who underwent revision surgeries for recurrent/residual vestibular schwannomas between 1985 and 2015. Main Outcome Measures  Degree of resection, facial nerve function, cerebrospinal fluid (CSF) leak. Results  A total of 234 patients underwent 250 revision surgeries for recurrent/residual vestibular schwannomas. Of these, 86 carried a diagnosis of neurofibromatosis type 2 (NF2). The mean number of prior surgeries was 1.26, and 197 (85%) prior surgeries had been performed elsewhere. The average age at surgery was 43. The most common approach employed at the time of revision surgery was translabyrinthine (87%), followed by transcochlear (6%), middle fossa (5%), and retrosigmoid (2%). Gross total resection was achieved in 212 revision surgeries (85%). Preoperative House-Brackmann facial nerve function was similar in non-NF2 and NF2 groups (mean: 2.7). Mean postoperative facial nerve function at last follow-up was 3.8 in the non-NF2 group and 3.9 in the NF2 group. History of radiation and the extent of resection were not associated with differences in facial nerve function preoperatively or postoperatively. CSF leaks occurred after 21 surgeries (8%), and six (2%) patients required reoperation. Conclusions  This is the largest series of revision surgery for vestibular schwannomas to date. Our preferred approach is the translabyrinthine craniotomy, which can be readily modified to include the transcochlear approach for improved access. CSF leak rate slightly exceeds that of primary surgery, and gross total resection is achievable in the vast majority of patients.

Surgical exposure of the internal auditory canal through the retrosigmoid approach with semicircular canals anatomical preservation

OBJECTIVE

Evaluate the feasibility of an adequate exposure with anatomical preservation of labyrinth structures through retrosigmoid transmeatal approach (RSA) in surgeries for resection of acoustic neuromas/vestibular schwannomas (VS).

METHOD

Thirty patients underwent surgical resection and were preoperatively evaluated with fine slice high definition CT scans and 3D-MRI volumetric reconstructions. Extension of internal auditory canal (IAC) opening during surgery was measured using 3 mm right-angle calibrated hook and neuronavigation parameters. Postoperatively, the extension of IAC opening and integrity of the labyrinth were confirmed through preoperatively images procedures.

RESULTS

The preoperative length of IACs varied between 7.8 and 12.0 mm (mean 9.3 mm, SD 0.98, 95%CI 8.9 to 9.6, and median 9.0 mm). Postoperative images demonstrated adequate opening of the IAC and semicircular channels integrity.

CONCLUSION

A complete drilling of the posterior wall of IAC through the RSA is feasible and allows direct visualization of the IAC-fundus without damaging the semicircular canals.

Does attempt at hearing preservation microsurgery of vestibular schwannoma affect postoperative tinnitus?

Background. The aim of this study was to analyze the effect of vestibular schwannoma microsurgery via the retrosigmoid-transmeatal approach with special reference to the postoperative tinnitus outcome. Material and Methods. A prospective study was performed in 89 consecutive patients with unilateral vestibular schwannoma indicated for microsurgery. Patient and tumor related parameters, pre- and postoperative hearing level, intraoperative findings, and hearing and tinnitus handicap inventory scores were analyzed. Results. Cochlear nerve integrity was achieved in 44% corresponding to preservation of preoperatively serviceable hearing in 47% and useful hearing in 21%. Main prognostic factors of hearing preservation were grade/size of tumor, preoperative hearing level, intraoperative neuromonitoring, tumor consistency, and adhesion to neurovascular structures. Microsurgery led to elimination of tinnitus in 66% but also new-onset of the symptom in 14% of cases. Preservation of useful hearing and neurectomy of the eighth cranial nerve were main prognostic factors of tinnitus elimination. Preservation of cochlear nerve but loss of preoperative hearing emerged as the main factor for tinnitus persistence and new onset tinnitus. Decrease of THI scores was observed postoperatively. Conclusions. Our results underscore the importance of proper pre- and intraoperative decision making about attempt at hearing preservation versus potential for tinnitus elimination/risk of new onset of tinnitus.

Determining benchmarks in hearing preservation surgery for vestibular schwannoma

Objectives The objectives of this study were to determine minimal benchmarks of success in vestibular schwannoma hearing preservation surgery, wherein the likelihood of having preserved hearing in a single patient is at least as likely as having created a poor facial nerve outcome for a single patient. Design This is a statistical analysis of published literature. Setting Academic Tertiary Medical Center. Main Outcome Measures Based on published natural history data, the number needed to treat (NNT) equation was used to calculate the minimally acceptable hearing preservation rates within various hearing classification schemes. Results Given good facial nerve outcome rates of 85, 90, and 95%, the corresponding hearing preservation rates at 4.7 years that are likely to preserve classes A and B hearing (American Academy of Otolaryngology-Head and Neck Surgery classification) in a single patient as to cause a poor facial nerve outcome are 70, 65, and 60%, respectively. If surgery is limited exclusively to intracanalicular tumors, these rates drop to 62, 57, and 52%, respectively. If the word recognition scoring classification is used, required hearing preservation rates are higher. Conclusion It is possible to use the NNT equation alongside projected facial nerve outcomes to estimate benchmarks of minimally acceptable hearing preservation rates.

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.

Impact of fundal extension on hearing after surgery for vestibular schwannomas

OBJECTIVE

To compare hearing preservation after surgery for intracanalicular vestibular schwannomas with or without fundal extension.

STUDY DESIGN

Retrospective chart review.

PATIENTS

Patients with intracanalicular tumors (≤ 10-m maximal dimension) undergoing retrosigmoid craniotomy between 2001 and 2010.

INTERVENTION

Preoperative and postoperative audiograms, preoperative magnetic resonance imaging, and operative reports were reviewed.

MAIN OUTCOME MEASURES

Preoperative and postoperative hearing (American Academy of Otolaryngology-Head and Neck Surgery classification).

RESULTS

Complete data for 53 patients (27 female and 24 male subjects, sex was not recorded for 2 patients) meeting selection criteria was available. Fundal involvement was identified in 39 (73.6%) of the 53 patients. The remaining 14 patients did not have tumor with fundal extension (26.4%). Average tumor size for patients with fundal extension (+FE) was 6.9 ± 2.2 mm and without fundal extension (-FE) was 8.2 ± 1.9 mm (p = 0.05, Student's t test). Average preoperative speech discrimination score for the entire study was 90.5 ± 11.8 (n = 53). After retrosigmoid approach for tumor resection, 79% of patients (42/53) had preserved hearing defined as American Academy of Otolaryngology-Head and Neck Surgery class A, B, or C. Average postoperative speech discrimination score for these patients was 89.3 ± 12.1, and average postoperative pure-tone average was 35.9 ± 9.1%. Eighty-five percent (33/39) of +FE patients had preserved hearing (class A, B, or C). In contrast, 64% (9/14) of -FE patients had hearing preserved (class A, B, or C; Fisher's exact test, p = 0.034).

CONCLUSION

Hearing preservation rate after retrosigmoid craniotomy for intracanalicular vestibular schwannomas may be superior for tumors with fundal extension compared with tumors that do not extend to the fundus.

The keyhole retrosigmoid approach to the cerebello-pontine angle: indications, technical modifications, and results

OBJECTIVES

Establish the versatility and usefulness of the keyhole retrosigmoid approach to the cerebello-pontine angle (CPA) in various pathologies.

DESIGN

Prospective clinical study.

SETTING

Tertiary referral university hospital.

METHODS

One hundred twenty-one patients with various pathologies of the CPA underwent the relevant investigations and were operated upon by the retrosigmoid microendoscopic approach. The technical modifications and progression of our technique are described.

RESULTS

This group consisted of 121 patients (103 men and 28 women). The pathologies included were 60 acoustic neuromas, 28 vestibular neurectomies, nine meningiomas, and four arachnoid cysts. For nonmass lesions, no additional facial nerve injury or deterioration of hearing occurred. Total excision of mass lesions was achieved in 94.5% of cases. Facial nerve integrity was preserved in 92.3% of cases with mass lesions and permanent facial paralysis occurred in 8.3%. There were no mortalities, and the most frequent complication was a delayed cerebrospinal fluid leak from the site of the wound (15%), which was managed conservatively in all cases.

CONCLUSIONS

The keyhole retrosigmoid approach is a versatile one. It can be used to deal with different pathologies through a unified access, and with the increasing exclusive use of endoscopes, a truly minimally invasive surgery can be achieved.

Guiding patients through the choices for treating vestibular schwannomas: balancing options and ensuring informed consent. 2007

Counseling patients who are diagnosed with vestibular schwannomas, formerly known as acoustic neuromas, can be challenging. The health care provider has the responsibility to explain, in understandable language, to the patient or legal representative the proposed treatment options, risks and complications associated with each form of treatment, and alternatives to treatment, including no therapy. Patients should be encouraged to gather information before making a treatment decision. For the physicians managing these patients, information should be delivered in a balanced way to ensure patient understanding of their options leading to adequate informed consent.

Guiding patients through the choices for treating vestibular schwannomas: balancing options and ensuring informed consent

Counseling patients who are diagnosed with vestibular schwannomas, formerly known as acoustic neuromas, can be challenging. The health care provider has the responsibility to explain, in understandable language, to the patient or legal representative the proposed treatment options, risks and complications associated with each form of treatment, and alternatives to treatment, including no therapy. Patients should be encouraged to gather information before making a treatment decision. For the physicians managing these patients, information should be delivered in a balanced way to ensure patient understanding of their options leading to adequate informed consent.

[Predictive factors of facial palsy of the acoustic neurinoma after retrosigmoid surgery: 230 cases]

OBJECTIVES

To determine predictive factors influencing postoperative facial palsy during retro sigmoid approach in vestibular schwannoma surgery.

MATERIAL AND METHODS

Retrospective study over 230 patients with vestibular schwannoma, mostly stade I and II, operated by retro sigmoid approach, by the same oto neuro chirurgical team between 1993 and 2004. Pre and post operative parameters taken into consideration: quantitative: age and sex, audiometric parameters, duration of clinical symptoms; qualitative: tumor anatomic factors and facial nerve function according to House Brackmann classification.

RESULTS

8 days after surgery, 92% of patients have a normal or subnormal facial nerve function, 5% a facial paresis and 3% a paralysis. After one year, only 4% of patients still have a grade III to VI paralysis. Latency of vertigo with facial nerve paralysis is 4.33 vs. 1.97 year in absence of paralysis. Hearing conservation is 85% without facial nerve paralysis vs. 58% with facial nerve paralysis; Wave III latency (PEAP) with facial nerve paralysis is 4.54 vs. 4.28 ms if not.

CONCLUSION

Significant predictive factors of facial nerve palsy outcome are: age, post surgery hearing conservation, wave III latency, difficulty in tumor dissection, vertigo latency.

An Anatomic and Radiologic Evaluation of Access to the Lateral Internal Auditory Canal Via the Retrosigmoid Approach and Description of an Internal Labyrinthectomy

OBJECTIVE

The retrosigmoid approach to the posterior petrous bone may be used as a hearing preservation operation for extirpation of posterior fossa and internal auditory canal (IAC) lesions. However, it is usually not possible to remove tumor from the most lateral portions of the IAC even after removing the retrolabyrinthine bone down to the posterior semicircular canal. Our goal was to examine the advantages and disadvantages of the retrosigmoid approach with respect to approaching the lateral IAC, to find what is gained by drilling down the retrolabyrinthine bone, and to describe an internal labyrinthectomy whereby the labyrinth is removed via a retrosigmoid approach.

MATERIALS AND METHODS

Using a 3.5-cm craniotomy, a retrosigmoid approach was performed on one side in each of five whole fresh cadaveric heads. The IAC was identified, and the length of the IAC and the depth of the acoustic porus from the center of the craniotomy were measured. The bone posterior to the labyrinth was removed, and the length of the portion of the IAC still inaccessible was measured. These measurements were compared with measurements using computed tomography (CT) scans of each cadaveric head. Additionally, we present the findings of 11 patients who had an internal labyrinthectomy performed by the senior author.

RESULTS

The average length of the IAC based on CT scanning was 11.2 mm (SD, 0.84 mm; range, 10-12 mm, 95% confidence interval [CI], 9.44-12.96). The potential gain predicted by the CT scans was 8.4 mm (SD, 0.9 mm; range, 7-9 mm). In the anatomic study, the average length of the IAC was 11.0 mm (SD, 2.3 mm; range, 8.0-13.0 mm; 95% CI, 9.26-12.78). The average length of the IAC that was inaccessible after removing the retrolabyrinthine bone was 6.7 mm (SD, 1.5 mm; range, 5.0-7.8 mm), or 61%. The average gain in access to the lateral IAC was 4.3 mm (SD, 1.0 mm; range, 2.7-5.2 mm). After performing an internal labyrinthectomy, the fundus was accessible, as was the labyrinthine segment of Cranial Nerve VII and the geniculate ganglion.

CONCLUSION

The retrosigmoid approach provides access to the posterior petrous bone, and removal of the bone posterior to the labyrinth provides some additional access to the lateral IAC. However, an internal labyrinthectomy is necessary to provide access to the fundus of the IAC via the retrosigmoid approach.

Facial Nerve Rerouting in Skull Base Surgery

Facial nerve rerouting techniques were developed to facilitate re-section of extensive tumors occupying the skull base. Facial nerve rerouting has its own limitations and risks, requiring microsurgical expertise, additional surgical time, and often some degree of facial nerve paresis. This article presents different degrees of anterior and posterior facial nerve rerouting, techniques of facial nerve rerouting, and a comprehensive review of outcomes. It then reviews anatomic and functional preservation of the facial nerve in acoustic neuroma resection, technical aspects of facial nerve dissection, intracranial facial nerve repair options, and outcomes for successful acoustic neuroma surgery.

Counseling Patients on Surgical Options for Treating Acoustic Neuroma

The selection of surgical approach for the removal of AN is a complex one, depending on factors related to specific tumor anatomy, patient characteristics, and the familiarity and skill level of the skull base team.Overall, the literature supports that surgical outcomes are acceptable in regard to tumor removal, patient safety, and complication rates. The inconsistent reporting methods in the current literature make it difficult to assess logically the rates for hearing preservation, facial nerve outcome, and complications as controlled for tumor size and other preoperative patient characteristics. The best conclusions would be from prospective surgical trials controlling for patient factors, size of the tumor, and experience of the skull base team. In the absence of such studies, formal meta-analyses may help clarify specific differences among approaches.

Facial Paralysis and Surgical Rehabilitation: A Quality Of Life Analysis in a Cohort of 1,595 Patients after Acoustic Neuroma Surgery

OBJECTIVES

On the basis of survey results of the Acoustic Neuroma Association, we report patient ratings of facial dysfunction and outcomes for various facial rehabilitative therapies after surgical treatment of acoustic neuroma (AN). We assessed patients' perceived quality of life (QOL) and reviewed the literature regarding facial dysfunction and its management associated with AN.

STUDY DESIGN

The Acoustic Neuroma Association mailed a detailed questionnaire to 2,372 members to identify preoperative and postoperative symptoms, complications, and long-term effects on physical and psychosocial function. A cohort of 1,595 (82.2%) respondents who underwent surgical treatment of ANs reported their experiences with facial dysfunction.

PATIENTS

Of all 1,940 survey respondents, 1,682 of 1,875 that had ANs underwent surgical treatment. The study included 1,595 patients with ANs (82.2% of all respondents) who underwent surgical treatment by way of the translabyrinthine, suboccipital, or middle fossa approaches and excluded 87 respondents who did not report the type of surgical approach.

METHODS

Respondents answered questions intended to qualify and quantify the degree that facial dysfunction impacted QOL parameters. Responses were analyzed for tumor size, surgical approach, patient age, and sex. Statistical analysis was performed using SPSS software.

RESULTS

In our analysis, 11% of all respondents experienced some degree of preoperative facial weakness or eye problems. Of all respondents, 45.5% (725 patients) experienced worsened facial weakness caused by surgery, and of these, 72% reported that it was permanent. The most commonly used successful therapy for facial reanimation for 271 (19.6%) patients was placement of a gold weight. The factor most often associated with poor outcome was a large tumor. Of all respondents, 28% felt significantly affected by facial weakness, 63% felt their smile was symmetric, and 70% were content "quite a bit" or "very much" with their QOL.

CONCLUSIONS

In this large cohort study of AN patients, facial dysfunction was a significant morbidity. Physicians should be aware of the risk factors identified, specifically large tumor size and the impact facial dysfunction has on QOL, when counseling patients regarding optimal management of AN.

Retrosigmoid versus middle fossa surgery for small vestibular schwannomas

OBJECTIVES/HYPOTHESIS

The objective was to determine the effect of approach, middle fossa versus retrosigmoid, on the hearing and facial nerve outcome of surgery for small vestibular schwannomas.

STUDY DESIGN

The study had two parts, a case study of patient data entered into a prospectively designed database at the author's institution, and a meta-analysis of similar published data.

METHODS

There were 73 of the author's private practice patients who met the inclusion criteria of intracanalicular vestibular schwannoma and total tumor removal by a retrosigmoid approach. American Academy of Otolaryngology-Head and Neck Surgery standardized hearing and facial nerve classifications of these patients and similar data from 11 other institutions were used to compare results of the two surgical approaches.

RESULTS

Median facial nerve results for all institutions were significantly better with the retrosigmoid approach (grade I: 95% for retrosigmoid and 81% for middle fossa). Median hearing results trended toward better outcome with the middle fossa approach (same preoperative hearing class: 48% for middle fossa and 39% for retrosigmoid). Individual institution had an equal or greater effect on outcome than the choice of surgical approach.

CONCLUSION

Surgical team accounted for more variability in hearing and facial nerve outcome than did approach. Retrosigmoid approach yielded significantly better facial nerve outcome. The trend toward better hearing outcome with the middle fossa approach may never achieve statistical significance across institutions because of high variability among surgical teams and small numbers of teams reporting results.