Imaging as an early biomarker to predict sensitivity to everolimus for progressive NF2-related vestibular schwannoma.

PURPOSE: NF2-related schwannomatosis (NF2) is characterized by bilateral vestibular schwannomas (VS) often causing hearing and neurologic deficits, with currently no FDA-approved drug treatment. Pre-clinical studies highlighted the potential of mTORC1 inhibition in delaying schwannoma progression. We conducted a prospective open-label, phase II study of everolimus for progressive VS in NF2 patients and investigated imaging as a potential biomarker predicting effects on growth trajectory. METHODS: The trial enrolled 12 NF2 patients with progressive VS. Participants received oral everolimus daily for 52 weeks. Brain imaging was obtained quarterly. As primary endpoint, radiographic response (RR) was defined as ≥ 20% decrease in target VS volume. Secondary endpoints included other tumors RR, hearing outcomes, drug safety and quality of life (QOL). RESULTS: Eight participants completed the trial and four discontinued the drug early due to significant volumetric VS progression. After 52 weeks of treatment, the median annual VS growth rate decreased from 77.2% at baseline to 29.4%. There was no VS RR and 3 of 8 (37.5%) participants had stable disease. Decreased or unchanged VS volume after 3 months of treatment was predictive of stabilization at 12 months. Seven of eight participants had stable hearing during treatment except one with a decline in word recognition score. Ten of twelve participants reported only minimal changes to their QOL scores. CONCLUSIONS: Volumetric imaging at 3 months can serve as an early biomarker to predict long-term sensitivity to everolimus treatment. Everolimus may represent a safe treatment option to decrease the growth of NF2-related VS in patients who have stable hearing and neurological condition. TRN: NCT01345136 (April 29, 2011).

Predictors of hearing functional outcome following surgery for cerebellopontine angle meningioma.

OBJECTIVE: Cerebellopontine angle (CPA) meningiomas can affect hearing function and require expeditious treatment to prevent permanent hearing loss. The authors sought to determine the factors associated with functional hearing outcome in CPA meningioma patients treated with surgery and/or radiation therapy in the form of either stereotactic radiosurgery or stereotactic radiation therapy. METHODS: Consecutive patients with CPA meningiomas who had presented at our hospital from 2008 to 2018 were identified through retrospective chart review. Hearing function (as defined by pure tone average (PTA) and speech discrimination score (SDS) on Audiogram) was assessed before and after surgery for CPA meningioma. Audiograms with PTA > 50 dB and SDS < 69% were defined as poor hearing functional outcome. Multivariable Cox Proportional Hazards Regression Model was used to assess the associations between pre-operative hearing functional assessment and post-operative hearing functional outcomes. RESULTS: The study cohort included 31 patients (80.6% females, with a mean age of 61.3 ± 15.2 years) with a median clinical follow-up of 5 months (range: 1 week-98 months). The mean pre-operative PTA and SDS were 23.8 ± 11.2 dB and 64.4 ± 22.2% respectively. At the last visit, there was significant hearing recovery, with an improvement of 29.7 ± 18.0 dB (p < 0.001) and 87.6 ± 17.8% (p < 0.001) in PTA and SDS respectively. After adjusting for age, gender, tumor volume, location, and tumor classification, Multivariable Cox Proportional Hazards Regression Model was conducted which revealed that patients undergoing surgery through retro sigmoid approach [Hazards Ratio (HR): 32.1, 95% Confidence Interval (CI): 2.11-491.0, p = 0.01] and gross total resection (GTR) (HR: 2.99, 95% CI: 1.09-9.32, p = 0.05) had significantly higher risk of poor hearing functional outcome compared to petrosal approach and near/subtotal resection. Moreover, patients with poor preoperative hearing had 85% higher chance of poor hearing functional outcome postoperatively (HR: 0.15, 95%CI: 0.03-0.59, p = 0.007). CONCLUSION: Postoperative improvement in hearing is a reasonable expectation following surgery for CPA meningioma. Preoperative hearing, surgical approach and extent of surgical resection are predictive factors of postoperative hearing function outcome and can therefore aid in identification of patients at higher risk of hearing loss.

Safety of 3 Tesla Magnetic Resonance Imaging in Patients With Auditory Brainstem Implants.

OBJECTIVE: To evaluate the safety of 3 Tesla (T) magnetic resonance imaging (MRI) in patients with auditory brainstem implants (ABI) with the magnet removed at implantation and report incidence of complications. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary neurotology ambulatory practice. PATIENTS: Patients with diagnosis of Neurofibromatosis, type 2 (NF2) with functional ABIs. INTERVENTIONS: Observational recordings. MAIN OUTCOME MEASURES: Of the 89 patients meeting inclusion criteria, 7 patients underwent 3T MRI, with a total of 39 scans done. Three patients had 1 scan each, one patient had 4 scans, one patient had 5 scans, one patient had 6 scans, and one patient had 21 scans. The mean time between ABI placement and first 3 T scan was 118 ±â€Š73 months. The most common indication for imaging was surveillance of NF2 lesions. The most frequent scans were MRI brain (25.6%), followed by MRI of cervical (15%), thoracic (15%) and lumbar (15%) spine, and MRI IAC (8%). There were no reported complications for any of the scans. No scans were interrupted due to patient discomfort. There were no device malfunctions. CONCLUSIONS: 3 T MRIs are safe in patients with ABIs as long as the magnet is removed. It is recommended that the magnet be removed at the time of implantation in all NF2 patients, who require frequent surveillance.

Anatomic Assessment of the Limits of an Endoscopically Assisted Retrolabyrinthine Approach to the Internal Auditory Canal.

Objective Data regarding the surgical advantages and anatomic constraints of a hearing-preserving endoscopic-assisted retrolabyrinthine approach to the IAC are scarce. This study aimed to define the minimum amount of retrosigmoid dural exposure necessary for endoscopic exposure of the IAC and the surgical freedom of motion afforded by this approach. Methods Presigmoid retrolabyrinthine approaches were performed on fresh cadaveric heads. The IAC was exposed under endoscopic guidance. The retrosigmoid posterior fossa dura was decompressed until the fundus of the IAC was exposed. Surgical freedom of motion at the fundus was calculated after both retrolabyrinthine and translabyrinthine approaches. Results The IAC was entirely exposed in nine specimens with a median length of 12 mm (range: 10-13 mm). Complete IAC exposure could be achieved with 1 cm of retrosigmoid dural exposure in eight of nine mastoids. For the retrolabyrinthine approach, the median anterior-posterior surgical freedom was 13 degrees (range: 6-23 degrees) compared with 46 degrees (range: 36-53 degrees) for the translabyrinthine approach ( p = 0.014). For the retrolabyrinthine approach, the median superior-inferior surgical freedom was 40 degrees (range 33-46 degrees) compared with 47 degrees (range: 42-51 degrees) for the translabyrinthine approach ( p = 0.022). Conclusion Using endoscopic assistance, the retrolabyrinthine approach can expose the entire IAC. We recommend at least 1.5 cm of retrosigmoid posterior fossa dura exposure for this approach. Although this strategy provides significantly less instrument freedom of motion in both the horizontal and vertical axes than the translabyrinthine approach, it may be appropriate for carefully selected patients with intact hearing and small-to-medium sized tumors involving the IAC.

Hypercoagulability in Vestibular Schwannoma Surgery.

OBJECTIVE: Patients with vestibular schwannoma who harbor a genetic predisposition for venous thromboembolism require special consideration when determining optimal therapeutic management. The primary objective of the current study was to provide recommendations on treatment of hypercoagulable patients with vestibular schwannoma through a case series and review of the literature. PATIENTS: Two patients who underwent resection of vestibular schwannomas. INTERVENTIONS: Surgical resection and diagnostic testing. MAIN OUTCOME MEASURES: Postoperative venous thromboses. RESULTS: One patient who underwent resection of vestibular schwannoma and suffered several postoperative thrombotic complications consistent with a clinical thrombophilia. One patient with known Factor V Leiden deficiency who underwent resection of vestibular schwannoma followed by postoperative chemoprophylaxis with a direct factor Xa inhibitor and experienced an uneventful postoperative course. CONCLUSIONS: In patients with a known propensity for venous thromboembolism, the skull base surgeon should consider nonsurgical management. If the patient undergoes surgical resection, we recommend careful effort to minimize trauma to the sigmoid sinus. In addition, the surgeon may consider retrosigmoid or middle fossa approaches. Best practice recommendations include the use of pneumatic compression devices, early ambulation, and consideration of postoperative prophylactic anticoagulation in patients with a known genetic predisposition.

Bilateral Auditory Brainstem Implants in Patients With Neurofibromatosis 2.

OBJECTIVE: To discuss indications for bilateral auditory brainstem implants (ABIs), compare audiometric outcomes of unilateral vs bilateral ABIs, and determine if patients have improved outcomes with addition of a second-side implant. STUDY DESIGN: Retrospective review of 24 patients with neurofibromatosis 2 (NF2) who underwent sequential placement of ABIs from 1989 to 2019. SETTING: Tertiary referral center. METHODS: Charts were reviewed for indication for second-side surgery, use of implants, and audiometric outcomes. Implants placed in the past 30 years were included in the study. Northwestern University Children's Perception of Speech (NU-CHIPS) and/or City University of New York (CUNY) sentence scores were compared in unilateral and bilateral conditions. RESULTS: Indications for a second-side implant included first-side implants with severe nonauditory symptoms (11), marginal audiometric results (9), outdated technology (2), or deterioration of first side (2). Seven patients are bilateral users and 1 patient discontinued bilateral use after a year due to no significant improvement over unilateral use. One patient with initial bilateral use was lost to follow-up. Thirteen patients are unilateral users due to nonaudiometric side effects or poor audiometric outcomes with the first side. Two patients are complete nonusers. Seventy-five percent had improved audiometric outcomes after the second-side implant, and 20% had stable findings. CONCLUSIONS: Second-side ABIs should be consider in patients with poor performance from a first-side implant. Most patients demonstrate subjective improvement with the second ABI. More research is needed for better objective assessments of improvements.

Effect of Vestibular Schwannoma Size and Nerve of Origin on Posterior External Auditory Canal Sensation: A Prospective Observational Study.

OBJECTIVE: Posterior external auditory canal (EAC) hypesthesia (Hitselberger's sign) has been previously described to occur in all vestibular schwannomas (1966) but has not been studied since. We hypothesized that sensory loss may be related to tumor size and sought to determine if this clinical sign could predict preoperative characteristics of vestibular schwannomas, intraoperative findings, and/or surgical outcomes. STUDY DESIGN: Prospective observational study. SETTING: Tertiary referral center. PATIENTS: Twenty-five consecutive patients who underwent surgery for vestibular schwannoma. INTERVENTION: Patients were tested for the presence of EAC hypesthesia or anesthesia. MAIN OUTCOME MEASURES: Preoperative, intraoperative, and postoperative findings were recorded, including facial nerve function, hearing function, tumor size, tumor nerve of origin, and extent of resection. RESULTS: Twelve patients (48%) demonstrated either posterior EAC hypesthesia (11 patients) or anesthesia (1 patient). Sensory loss was a significant predictor of size (tumor maximal diameter) (p = 0.004). Median tumor diameter was 1.7 cm in the cohort with intact sensation versus 2.9 cm in the cohort with sensory loss. Patients with sensory loss were also significantly more likely to be associated with a superior vestibular nerve origin tumor (p = 0.01). Preoperative sensory loss did not significantly predict postoperative facial outcome (p = 0.10). CONCLUSION: Neurological exam findings may be overlooked in the workup of brain tumors. Posterior EAC hypesthesia is a predictor of tumor size and superior vestibular nerve origin. These findings may have implications for patient selection, particularly with the middle cranial fossa approach. Furthermore, given this relationship with tumor size, this clinical biomarker should be studied as a potential predictor of tumor growth.

Effect of Anatomic Segment Involvement on Stereotactic Radiosurgery for Facial Nerve Schwannomas: An International Multicenter Cohort Study.

BACKGROUND: Facial nerve schwannomas are rare, challenging tumors to manage due to their nerve of origin. Functional outcomes after stereotactic radiosurgery (SRS) are incompletely defined. OBJECTIVE: To analyze the effect of facial nerve segment involvement on functional outcome for these tumors. METHODS: Patients who underwent single-session SRS for facial nerve schwannomas with at least 3 mo follow-up at 11 participating centers were included. Preoperative and treatment variables were recorded. Outcome measures included radiological tumor response and neurological function. RESULTS: A total of 63 patients (34 females) were included in the present study. In total, 75% had preoperative facial weakness. Mean tumor volume and margin dose were 2.0 ± 2.4 cm3 and 12.2 ± 0.54 Gy, respectively. Mean radiological follow-up was 45.5 ± 38.9 mo. Progression-free survival at 2, 5, and 10 yr was 98.1%, 87.2%, and 87.2%, respectively. The cumulative proportion of patients with regressing tumors at 2, 5, and 10 yr was 43.1%, 63.6%, and 63.6%, respectively. The number of involved facial nerve segments significantly predicted tumor progression (P = .04). Facial nerve function was stable or improved in 57 patients (90%). Patients with involvement of the labyrinthine segment of the facial nerve were significantly more likely to have an improvement in facial nerve function after SRS (P = .03). Hearing worsened in at least 6% of patients. Otherwise, adverse radiation effects included facial twitching (3 patients), facial numbness (2 patients), and dizziness (2 patients). CONCLUSION: SRS for facial nerve schwannomas is effective and spares facial nerve function in most patients. Some patients may have functional improvement after treatment, particularly if the labyrinthine segment is involved.

Hypofractionated Robotic Stereotactic Radiosurgery for Vagal Paragangliomas: A Novel Treatment Strategy for Cranial Nerve Preservation.

OBJECTIVE: To provide the first description of hypofractionated stereotactic radiosurgery (SRS) and evaluate tumor control and safety for vagal paragangliomas (VPs), which begin at the skull base but often have significant extracranial extension. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary-referral neurotology and neurosurgery practice. SUBJECTS AND METHODS: Five VPs in 4 patients (all male, ages 15-56 years) underwent SRS between 2010 and 2018. Outcome measures included tumor dimensions on serial imaging, cranial nerve function, and radiation side effects. RESULTS: CyberKnife hypofractionated SRS was performed. The prescription dose was 24 or 27 Gy (maximum dose 33.4 Gy; range, 29.3-35.5 Gy) delivered in 3 equal fractions. The mean isodose line was 79% (range, 76%-82%). Four VPs were treated primarily, and 1 tumor underwent SRS to treat regrowth 2 years after microsurgical subtotal resection via the modified infratemporal fossa approach. The treatment volume ranged from 8.81 to 86.3 cm3 (mean, 35.7 cm3). All demonstrated stable size (n = 3) or regression (n = 2) at last follow-up, 63 to 85 months after SRS (mean, 76 months). One patient had stable premorbid vocal fold paralysis from a prior ipsilateral glomus jugulare tumor resection. All others demonstrated normal vagal function following SRS. Treatment-related side effects, including dysgeusia (n = 1), mucositis (n = 1), and neck soft-tissue edema (n = 2), were self-limited. CONCLUSIONS: Hypofractionated SRS appears to be both safe and effective for treating VPs, including large-volume and predominantly extracranial tumors, while preserving vagal function. SRS should be considered as a cranial nerve preservation option, especially in settings of contralateral lower cranial nerve deficits or in those with multiple paragangliomas risking both vagal nerves.

Temporal bone resection for lateral skull-base malignancies.

INTRODUCTION: Malignancies involving the temporal bone are increasingly common and require specialized multi-disciplinary care. Given this complex location, involvement of the lateral skull base and local neurovascular structures is common. In this review we discuss general principles for temporal bone resection, as well as alternative and complementary surgical approaches that should be considered in the management of patients with temporal bone cancer. METHODS: A comprehensive review on literature pertaining to temporal bone resection was performed. RESULTS: The primary surgical strategy for malignancies of the temporal bone is temporal bone resection. This may be limited to the ear canal and tympanic membrane (lateral temporal bone resection) or may include the otic capsule and its contents (subtotal temporal bone resection), and/or the petrous apex (total temporal bone resection). Management of adjacent neurovascular structures including the facial nerve, the carotid artery, and the jugular bulb/sigmoid sinus should be considered during surgical planning. Finally, adjunctive procedures such as parotidectomy and neck dissection may be required based on tumor stage. CONCLUSIONS: Temporal bone resection is an important technique in the treatment of lateral skull-base malignancies. This strategy should be incorporated into a multi-disciplinary approach to cancer.

Congenital Cholesteatoma of the Sphenoid, Occipital, and Temporal Bones: 54-Year Follow Up.

OBJECTIVE: To provide long-term follow up of a unique patient with history of massive petrous apex congenital cholesteatoma. PATIENT: 75-year-old man who presented at age 18 with left Gradenigo-like syndrome. INTERVENTION: Staged left radical mastoidectomy and open transsphenoidal marsupialization. Followed with routine in-office cholesteatoma debridement. MAIN OUTCOME MEASURES: Bony erosion on computed tomography (CT), monitoring for new symptoms. RESULTS: Interval development of sensorineural component of hearing loss due to cochlear fistulization. Very slow skull base bony erosion continues without neck destabilization. No new or recurrent cranial neuropathies have developed. CONCLUSIONS: Marsupialized cholesteatoma may be followed with routine debridement and interval imaging for monitoring over many decades.

Skull Base Training and Mentorship.

OBJECTIVE: To review teaching and mentoring techniques of experienced skull base surgeons and educators STUDY DESIGN:: Expert commentary. SETTING: 8th Quadrennial International Conference on vestibular schwannoma and other CPA tumors, panel on teaching, and mentoring. MAIN OUTCOME MEASURES: Experiences and opinions of experienced skull base surgeons, both neurosurgeons and neurotologists, presented and discussed at the conference. CONCLUSIONS: Obtaining surgical mastery is essential for the teachers of skull base surgery. Hard work and practice with immediate and constant feedback on performance is an essential component to success. Creating a patient-centered culture that encourages academic achievement is an accelerator for success of a training program. Both the mentor and the mentee must play an intentional and active role to maximize learning.

Working Toward Consensus on Sporadic Vestibular Schwannoma Care: A Modified Delphi Study.

OBJECTIVE: To address variance in clinical care surrounding sporadic vestibular schwannoma, a modified Delphi study was performed to establish a general framework to approach vestibular schwannoma care. A multidisciplinary panel of experts was established with deliberate representation from key stakeholder societies. External validity of the final statements was assessed through an online survey of registered attendees of the 8th Quadrennial International Conference on Vestibular Schwannoma. STUDY DESIGN: Modified Delphi method. METHODS: The panel consisted of 16 vestibular schwannoma experts (8 neurotology and 8 neurosurgery) and included delegates representing the AAOHNSF, AANS/CNS tumor section, ISRS, and NASBS. The modified Delphi method encompassed a four-step process, comprised of one prevoting round to establish a list of focus areas and three subsequent voting rounds to successively refine individual statements and establish levels of consensus. Thresholds for achieving moderate consensus, at ≥67% agreement, and strong consensus, at ≥80% agreement, were determined a priori. All voting was performed anonymously via the Qualtrics online survey tool and full participation from all panel members was required before procession to the next voting round. RESULTS: Through the Delphi process, 103 items were developed encompassing hearing preservation (N = 49), tumor control and imaging surveillance (N = 20), preferred treatment (N = 24), operative considerations (N = 4), and complications (N = 6). As a result of item refinement, moderate (4%) or strong (96%) consensus was achieved in all 103 final statements. Seventy-nine conference registrants participated in the online survey to assess external validity. Among these survey respondents, moderate (N = 21, 20%) or strong (N = 73, 71%) consensus was achieved in 94 of 103 (91%) statements, and no consensus was reached in 9 (9%). Of the four items with moderate consensus by the expert panel, one had moderate consensus by the conference participants and three had no consensus. CONCLUSION: This modified Delphi study on sporadic vestibular schwannoma codifies 100% consensus within a multidisciplinary expert panel and is further supported by 91% consensus among an external group of clinicians who regularly provide care for patients with vestibular schwannoma. These final 103 statements address clinically pragmatic items that have direct application to everyday patient care. This document is not intended to define standard of care or drive insurance reimbursement, but rather to provide a general framework to approach vestibular schwannoma care for providers and patients.

Radiation-Induced Malignant Peripheral Nerve Sheath Tumor of the Vagus Nerve Following Radiation Treatment of Cervical Paraganglioma.

Radiation-induced sarcoma is a known but rare complication of radiation treatment for skull base paraganglioma. We present the cases of a female patient with multiple paraganglioma syndrome treated with external beam radiation treatment who presented 4 years later with a malignant peripheral nerve sheath tumor of the vagus nerve.

Cochlear implantation and auditory brainstem implantation in neurofibromatosis type 2.

OBJECTIVES/HYPOTHESIS: To report a series of patients with neurofibromatosis type 2 (NF2), where each patient underwent both cochlear implantation and auditory brainstem implantation for hearing rehabilitation, and to discuss factors influencing respective implant success. STUDY DESIGN: Retrospective case series. METHODS: Ten NF2 patients with both cochlear implantations and auditory brainstem implantations were retrospectively reviewed. Speech testing for auditory brainstem implants (ABIs) and cochlear implants (CIs) was performed separately. Scores at last follow-up were obtained for Iowa vowels and consonants, Northwestern University Children's Perception of Speech (NU-CHIPS), and City University of New York (CUNY) sentences. RESULTS: Mean age at time of implant was 37 years for cochlear implantation and 40 years for auditory brainstem implantation (P = .790, t test). Nine of 10 patients had a CI and ABI on contralateral sides, and one had both devices on the same side. Mean duration of deafness in the implanted ear was 4.3 years for both cochlear implantation and auditory brainstem implantation (P = .491, t test). Follow-up range was 1 to 28 years. CI performance on NU-CHIPS was 32% to 100%, and sound + lip-reading CUNY was 56% to 100%. Four patients experienced an eventual decline in CI function to unusable levels. ABI performance on NU-CHIPS was 40% to 80%, and sound + lip-reading CUNY was 38% to 94%. There was no notable decline in ABI function over time. CONCLUSIONS: If the cochlear nerve is intact, cochlear implantation can be an effective strategy for hearing rehabilitation in NF2. However, a significant proportion experience a decline in CI performance related to growing vestibular schwannoma or tumor treatment. Auditory brainstem implantation remains the standard option for surgical hearing rehabilitation in NF2, but peak performance is generally lower than that achievable with cochlear implantation. LEVEL OF EVIDENCE: 4. Laryngoscope, 128:2163-2169, 2018.

Tinnitus Suppression After Auditory Brainstem Implantation in Patients With Neurofibromatosis Type-2.

OBJECTIVE: To evaluate whether an auditory brainstem implant (ABI) can impact levels of tinnitus in neurofibromatosis type-2 (NF2) patients who have undergone translabyrinthine craniotomy for vestibular schwannoma (VS) removal and to evaluate the burden of tinnitus in these patients. STUDY DESIGN: A retrospective case series and patient survey. SETTING: Tertiary neurotologic referral center. PATIENTS: NF2 patients who underwent translabyrinthine removal of VS and ABI placement between 1994 and 2015. INTERVENTIONS: A survey, retrospective review and two validated tinnitus handicap questionnaires (tinnitus handicap inventory [THI] and tinnitus visual analogue scale [VAS]) were used to characterize the degree of tinnitus in NF2 patients and whether an ABI can alter tinnitus levels. MAIN OUTCOME MEASURES(S): Survey results, THI and VAS scores. RESULTS: One hundred twelve ABI users were contacted and 43 patients (38.3)% responded to our survey. Tinnitus was reported in 83.7% of patients. The THI score for responders was 17.8 ±â€Š20.5 standard deviation (SD). For survey participants, the ABI reduced tinnitus levels (mean VAS: Off = 3.5; On 1-h = 2.1; p = 0.048). For patients who subjectively reported that the ABI reduced tinnitus loudness, tinnitus levels were immediately reduced on ABI activation and after 1 hour of use (mean VAS: Off = 4.8; On = 2.4; On 1-h = 1.8; p < 0.01). Suppression did not continue after the device was turned off. Audiological performance with the ABI did not correlate with tinnitus suppression. CONCLUSION: NF2 patients who have undergone removal of VS have a significant tinnitus handicap and benefit from tinnitus suppression through utilization of an ABI possibly through masking or electrical stimulation of the auditory brainstem.

Nerve crush but not displacement-induced stretch of the intra-arachnoidal facial nerve promotes facial palsy after cerebellopontine angle surgery.

Little is known about the reasons for occurrence of facial nerve palsy after removal of cerebellopontine angle tumors. Since the intra-arachnoidal portion of the facial nerve is considered to be so vulnerable that even the slightest tension or pinch may result in ruptured axons, we tested whether a graded stretch or controlled crush would affect the postoperative motor performance of the facial (vibrissal) muscle in rats. Thirty Wistar rats, divided into five groups (one with intact controls and four with facial nerve lesions), were used. Under inhalation anesthesia, the occipital squama was opened, the cerebellum gently retracted to the left, and the intra-arachnoidal segment of the right facial nerve exposed. A mechanical displacement of the brainstem with 1 or 3 mm toward the midline or an electromagnet-controlled crush of the facial nerve with a tweezers at a closure velocity of 50 and 100 mm/s was applied. On the next day, whisking motor performance was determined by video-based motion analysis. Even the larger (with 3 mm) mechanical displacement of the brainstem had no harmful effect: The amplitude of the vibrissal whisks was in the normal range of 50°-60°. On the other hand, even the light nerve crush (50 mm/s) injured the facial nerve and resulted in paralyzed vibrissal muscles (amplitude of 10°-15°). We conclude that, contrary to the generally acknowledged assumptions, it is the nerve crush but not the displacement-induced stretching of the intra-arachnoidal facial trunk that promotes facial palsy after cerebellopontine angle surgery in rats.

Historical perspective on evolution in management of lateral skull base tumors.

This article gives a history of the major advances that have contributed to the current management of lateral skull base lesions. These advances include changes in surgical technique, better understanding of the natural history of these lesions, and the advent of stereotactic radiosurgery. An understanding of how treatment has evolved over time improves understanding of how the current treatment methods have been developed.

Stereotactic radiosurgery for facial nerve schwannomas: meta-analysis and clinical review.

OBJECTIVE: Although several small individual series on stereotactic radiosurgery (SRS) for facial nerve schwannomas (FNSs) have been published, we aim to systematically aggregate data from the literature as well as from our institution to better understand the safety and efficacy of SRS for FNS. DATA SOURCES: PubMed English language search for keywords "facial nerve schwannoma" AND "radiation therapy" published from January 1995 to 2014. Data from our institution were also included in the analysis. STUDY SELECTION: Minimum study inclusion criteria included tumor treatment outcomes yielding 10 studies in the literature. In addition, our institution's data on six patients were included. DATA EXTRACTION: Data included radiation treatment type, radiation dose, tumor size, tumor control, tumor control definition, FN function, hearing outcome, and duration of follow-up. DATA SYNTHESIS: In total, there were 45 patients with at least 2-year follow-up. Forty-two patients (93.3%) had tumor control. Of those patients with described growth/shrinkage definitions, 50.0% had no growth, 43.3% had shrinkage, and 6.7% had growth. Of those articles that included FN functional outcomes, 26 patients (66.6%) had stable FN function, 8 (20.5%) had improved function, and 5 (12.8%) had worsened FN function after treatment. In total, there were 30 patients whose hearing outcomes were discussed in the literature. Of those with serviceable hearing before SRS (n = 14), nine (64.3%) had stable hearing and five (36.7%) had worsened function after SRS. The mean posttreatment follow-up period was 42.1 months. CONCLUSION: SRS seems to be effective at either stabilizing or shrinking FNS. However, significant morbidities of FN paralysis hearing loss do exist.

Cerebellopontine angle and intracanalicular masses mimicking vestibular schwannomas.

OBJECTIVE: To describe the clinical and radiographic characteristics in a series of patients with non-vestibular schwannoma cerebellopontine angle (CPA) and intracanalicular (IAC) masses, who underwent microsurgery for presumed vestibular schwannoma (VS). STUDY DESIGN: Retrospective case series. SETTING: Tertiary neurotologic referral center. PATIENTS: One thousand five hundred ninety-three patients underwent microsurgery for apparent VS from 2002 to 2013. Of these, 53 patients (3%) were discovered to have a diagnosis other than VS. INTERVENTIONS: Middle fossa, translabyrinthine, and retrosigmoid craniotomy. MAIN OUTCOME MEASURES: Clinical presentation, radiologic analysis, and histopathology examination. RESULTS: There were 17 facial schwannomas, 15 meningiomas, 9 hemangiomas, 6 lipochoristomas, 3 inflammatory reactions, and one each of lymphoma, glial heterotopia, solitary fibrous tumor, ependymoma, and a non-diagnostic mass. Excluding facial schwannomas, 23 cases were misdiagnosed as VS in the first half of the study period, compared to only 15 cases in the latter half (p = 0.09). Ninety-six percent of patients presented with some combination of sensorineural hearing loss, balance disturbance, and tinnitus. In the subset of patients with available preoperative MRI scans for retrospective review, only 4 of 28 patients had radiologic findings suggestive of pathology other than VS. The most common missed radiologic diagnoses were facial schwannoma, lipochoristoma, and meningioma. CONCLUSION: A subgroup of patients with CPA and IAC masses who present with radiologic findings diagnostic of VS will have an alternative histopathologic diagnosis. Optimal radiologic imaging and experienced interpretation can improve diagnostic accuracy. The most common tumors that mimic VS despite ideal radiologic imaging are facial schwannomas, meningiomas, and hemangiomas.