Coordinated Same- or Next-Day Radiosurgery and Cochlear Implantation for Vestibular Schwannoma.

OBJECTIVE: To describe the experience and results from coordinated and closely scheduled radiosurgery and cochlear implantation (CI) in a vestibular schwannoma (VS) cohort. PATIENTS: Patients with VS who underwent radiosurgery followed by CI on the same or next day. INTERVENTIONS: Interventions included sequential radiosurgery and CI. MAIN OUTCOME MEASURES: Tumor control defined by tumor growth on posttreatment surveillance and audiometric outcomes including consonant-nucleus-consonant words and AzBio sentences in quiet. RESULTS: In total, six patients were identified that met the inclusion criteria, with an age range of 38 to 69 years and tumor sizes ranging from 2.0 to 16.3 mm. All patients successfully underwent radiosurgery and CI on the same or immediately successive day. Postoperatively, all patients obtained open-set speech recognition. Consonant-nucleus-consonant word scores ranged from 40 to 88% correct, and AzBio scores ranged from 44 to 94% correct. During posttreatment magnetic resonance imaging surveillance, which ranged from 12 to 68 months, all tumors were noted to be adequately visualized, and no tumor progression was noted. CONCLUSION: Coordinated radiosurgery and CI can be safely performed in patients with VS on the same or next day, serving to decrease burden on patients and increase access to this vital rehabilitative strategy.

Risk of Monopolar Electrosurgery in Cochlear Implant Recipients is Nominal: Evidence to Guide Clinical Practice.

OBJECTIVE: Comprehensively assess the prevalence of monopolar electrosurgery-related device complications among cochlear implant (CI) recipients. STUDY DESIGN: Multifaceted retrospective review and survey. SETTING: Tertiary medical center. METHODS: Multifaceted approach including: (i) review of the current literature; (ii) historical review of institutional data from an academic, tertiary CI center; (iii) review of industry data provided by 3 Food and Drug Administration-approved CI manufacturers; and (iv) survey of high-volume CI centers. RESULTS: Literature review identified 9 human studies, detailing 84 devices with 199 episodes of device-cautery exposure. From studies reporting on patients records, no implant showed evidence of damage after exposure. One cadaveric study using dental cautery reported 1 episode of device damage. Review of institutional records did not identify any CI damage in 84 instances of exposure. Data from the 3 major implant manufacturers showed a single report of damage that could be reasonably linked to monopolar electrosurgery, out of a possible 689,426 CIs. Last, a survey of 8 high-volume CI centers did not identify any adverse events associated with monopolar cautery. CONCLUSION: These data estimate the risk of adverse device-related events or tissue injury to be extraordinarily low. Short of operating in immediate proximity to the CI (ie, the ipsilateral temporoparietal scalp), these data indicate that monopolar electrosurgery can be used in the body and the head-and-neck of CI recipients with nominal risk. These findings may guide decision-making in cases that are optimally or preferably performed with monopolar electrocautery and can be used to counsel CI patients following inadvertent exposures.

Comparing Speech Recognition Outcomes Between Cochlear Implants and Auditory Brainstem Implants in Patients With NF2-Related Schwannomatosis.

OBJECTIVE: To compare cochlear implant (CI) and auditory brainstem implant (ABI) performance in patients with NF2-related schwannomatosis (NF2). STUDY DESIGN: Historical cohort. SETTING: Tertiary academic center. PATIENTS: A total of 58 devices among 48 patients were studied, including 27 ABIs implanted from 1997 to 2022 and 31 CIs implanted from 2003 to 2022. Three patients had bilateral ABIs, three had bilateral CIs, three had an ABI on one side and a CI on the other, one had a CI that was later replaced with an ipsilateral ABI, and one had an ABI and CI concurrently on the same side. INTERVENTIONS: CI or ABI ipsilateral to vestibular schwannoma. MAIN OUTCOME MEASURES: Open-set speech perception, consonant-nucleus-consonant word scores, and AzBio sentence in quiet scores. RESULTS: Among all patients, 27 (47%) achieved open-set speech perception, with 35 (61%) daily users at a median of 24 months (interquartile range [IQR], 12-87 mo) after implantation. Comparing outcomes, CIs significantly outperformed ABIs; 24 (77%) CIs achieved open-set speech perception compared with 3 (12%) ABIs, with median consonant-nucleus-consonant and AzBio scores of 31% (IQR, 0-52%) and 57% (IQR, 5-83%), respectively, for CIs, compared with 0% (IQR, 0-0%) and 0% (IQR, 0-0%), respectively, for ABIs. Patients with ABIs were younger at diagnosis and at implantation, had larger tumors, and were more likely to have postoperative facial paresis. CONCLUSION: Many patients with NF2-associated vestibular schwannoma achieved auditory benefit with either a CI or an ABI; however, outcomes were significantly better in those patients who were able to receive a CI. When disease and anatomy permit, hearing rehabilitation with a CI should be considered over an ABI in these patients. Tumor management strategies that increase the ability to successfully use CIs should be strongly considered given the high risk of losing bilateral functional acoustic hearing in this population.

Natural History of Serviceable Hearing During Active Surveillance of Nongrowing Sporadic Vestibular Schwannoma Supports Consideration of Initial Wait-and-Scan Management.

OBJECTIVE: The treatment paradigm of vestibular schwannoma (VS) focuses on preservation of neurologic function, with small tumors increasingly managed with active surveillance. Often, tumor size and hearing outcomes are poorly correlated. The aim of the current work was to describe the natural history of hearing among patients with nongrowing VS during observational management. STUDY DESIGN: Historical cohort study. PATIENTS: Adults with sporadic VS. INTERVENTION: Wait-and-scan management. MAIN OUTCOME MEASURE: Maintenance of serviceable hearing (SH) after diagnosis. RESULTS: Among 228 patients with nongrowing VS, 157 patients had SH at diagnosis. Rates of maintaining SH (95% CI; number still at risk) at 1, 3, and 5 years after diagnosis were 94% (89-98; 118), 81% (74-89; 65), and 78% (71-87; 42), respectively. Poorer hearing at diagnosis (hazard ratio [HR] per 10 dB hearing level increase in pure-tone average of 2.51, p < 0.001; HR per 10% decrease in word recognition score of 1.70, p = 0.001) was associated with increased likelihood of developing non-SH during observation. When controlling for baseline hearing status, tumors measuring 5 mm or greater in the internal auditory canal or with cerebellopontine angle extension were associated with significantly increased risk of developing non-SH (HR, 4.87; p = 0.03). At 5 years after diagnosis, 95% of patients with nongrowing intracanalicular VS measuring less than 5 mm maintained SH. CONCLUSIONS: Hearing worsens during periods of nongrowth in sporadic VS. Patients with small (<5 mm) intracanalicular tumors demonstrate robust maintenance of SH over time, reinforcing the consideration of initial observation in this patient subset.

Initial Experiences with the Envoy Acclaim® Fully Implanted Cochlear Implant.

Introduction: Cochlear implantation has become the standard of care for the treatment of moderate-to-profound bilateral sensorineural hearing loss. However, current technologies, all of which rely on an external sound processor, have intrinsic limitations that prevent certain activities and diagnostics, thus hampering full integration into a patient's lifestyle. The Envoy Medical (White Bear Lake, MN, USA) Acclaim® fully implanted cochlear implant is a new device currently undergoing testing that has been designed to alleviate many of the current constraints by housing all components within the patient, thus allowing for near-constant use in many environments that are not conducive to a traditional cochlear implant. Methods: As part of an Early Feasibility Study, three adult implant candidates were implanted with the Acclaim® cochlear implant. Surgical video and photography were taken, and initial observations were recorded. Implantation with the Acclaim® device is largely similar to a traditional cochlear implant, with modifications to allow room for the implanted sensor as well as the implantation of a battery in the subcutaneous tissues of the chest. Results: This study demonstrates a step-by-step overview of implanting the Acclaim® and discusses initial insight and experiences with the first three implantations with this new device. Conclusions: All three surgeries proceeded without complication, and at activation, all three patients were hearing through their devices. Surgery is more technically challenging compared to a standard cochlear implant, but the skills needed can all be mastered by a dedicated otologic surgeon.

Cochlear Implant Outcomes between Patients with Sporadic and Neurofibromatosis Type 2-Associated Vestibular Schwannoma.

OBJECTIVE: Compare cochlear implant (CI) performance between patients with ipsilateral sporadic vestibular schwannoma (VS) and NF2-related schwannomatosis (NF2). Compare CI performance according to VS management modality. STUDY DESIGN: Historical cohort. SETTING: Tertiary academic center. PATIENTS: Forty-nine patients (52 ears) undergoing cochlear implantation in the setting of ipsilateral sporadic (n = 21) or NF2-associated VS (n = 28). INTERVENTIONS: CI ipsilateral to VS. MAIN OUTCOME MEASURES: Auditory thresholds, consonant-nucleus-consonant (CNC) word scores, and AzBio sentences in quiet scores. RESULTS: Among all patients, median post-CI pure tone average was 28 dB HL (interquartile range [IQR], 21-38), CNC word score was 39% (IQR, 6-62), and AzBio sentences in quiet score was 60% (IQR, 11-83) at a median of 12.5 months postimplantation. Despite the NF2 cohort having larger tumors, when comparing patients with sporadic versus NF2-associated VS, there were no statistically significant differences in CNC word (49% [30-70] vs. 31% [0-52]) or AzBio sentences in quiet (66% [28-80] vs. 57% [5-83]) scores. Regardless of NF2 status, all patients managed with observation, and radiosurgery achieved open-set speech. In patients who underwent microsurgery, 6 (46%) of 13 with NF2 achieved open-set speech recognition compared with 4 (67%) of 6 with sporadic disease. CONCLUSION: Select patients with VS achieve successful hearing rehabilitation with a CI. In this cohort, tumor management strategy significantly influenced CI performance, whereas differences in NF2 status exhibited less effect. Specifically, all patients managed with observation or radiosurgery achieved open-set speech perception, whereas approximately half of people with NF2-related VS and two-thirds of people with sporadic VS achieved this outcome after tumor microsurgery. When disease permits, observation and radiosurgery should be considered in patients who may later pursue a CI.

The Effect of Age on Facial Nerve Recovery After Vestibular Schwannoma Resection.

OBJECTIVE: The objective of this study is to assess the influence of age on facial nerve recovery after microsurgical resection of sporadic vestibular schwannoma. STUDY DESIGN: A historical cohort study was performed. SETTING: The study was performed at a tertiary referral center. PATIENTS: The studied cohort included patients with a House-Brackmann (HB) Grade III or worse in the immediate postoperative period. INTERVENTIONS: The studied intervention was microsurgical resection. MAIN OUTCOME MEASURES: The main outcome measure was complete recovery of facial nerve function to HB Grade I at least 12 months postoperatively. RESULTS: There were six patients with intracanalicular tumors and 100 with cerebellopontine angle (CPA) tumors eligible for study. Given the few patients with intracanalicular tumors, no further analysis was pursued in this subset. For patients with CPA tumors, a multivariable analysis of several patient and tumor characteristics demonstrated age at surgery (odds ratio for 10-year increase of 0.68; 95% confidence interval [CI], 0.47-0.98; p = 0.04) and immediate postoperative HB grade (odds ratio for one-grade increase of 0.27; 95% CI, 0.15-0.50; p < 0.001) to be jointly significantly associated with complete recovery to HB Grade I, indicating that the likelihood of complete facial nerve recovery was higher for younger patients and for those with better immediate postoperative HB grades. For example, the predicted probability of complete facial nerve recovery for a 30-year-old with immediate postoperative HB Grade III was 0.76 (or 76% when expressed as a percentage), whereas the predicted probability for a 50-year-old with immediate postoperative HB Grade V was only 0.10. CONCLUSIONS: After considering immediate postoperative HB grade, younger age at surgery was independently significantly associated with complete facial nerve recovery, which can assist in intraoperative decision-making regarding extent of resection and postoperative counseling.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Far Lateral Approach.

Introduction Skull base neuroanatomy is classically taught using surgical atlases. Although these texts are critical and rich resources for learning three-dimensional (3D) relationships between key structures, we believe they could be optimized and complemented with step-by-step anatomical dissections to fully meet the learning needs of trainees. Methods Six sides of three formalin-fixed latex-injected specimens were dissected under microscopic magnification. A far lateral craniotomy was performed by each of three neurosurgery resident/fellow at varying stages of training. The study objective was the completion and photodocumentation of the craniotomy to accompany a stepwise description of the exposure to provide a comprehensive, intelligible, and anatomically oriented resource for trainees at any level. Illustrative case examples were prepared to supplement approach dissections. Results The far lateral approach provides a wide and versatile corridor for posterior fossa operation, with access spanning the entire cerebellopontine angle (CPA), foramen magnum, and upper cervical region. Key Steps Include The study includes the following steps: positioning and skin incision, myocutaneous flap, placement of burr holes and sigmoid trough, fashioning of the craniotomy bone flap, bilateral C1 laminectomy, occipital condyle/jugular tubercle drilling, and dural opening. Conclusion Although more cumbersome than the retrosigmoid approach, a far lateral craniotomy offers unparalleled access to lesions centered lower or more medially in the CPA, as well as those with significant extension into the clival or foramen magnum regions. Dissection-based neuroanatomic guides to operative approaches provide a unique and rich resource for trainees to comprehend, prepare for, practice, and perform complex cranial operations, such as the far lateral craniotomy.

Predictive Value of K i -67 Index in Evaluating Sporadic Vestibular Schwannoma Recurrence: Systematic Review and Meta-analysis.

Introduction K i -67 is often used as a proliferation index to evaluate how aggressive a tumor is and its likelihood of recurrence. Vestibular schwannomas (VS) are a unique benign pathology that lends itself well to evaluation with K i -67 as a potential marker for disease recurrence or progression following surgical resection. Methods All English language studies of VSs and K i -67 indices were screened. Studies were considered eligible for inclusion if they reported series of VSs undergoing primary resection without prior irradiation, with outcomes including both recurrence/progression and K i -67 for individual patients. For published studies reporting pooled K i -67 index data without detailed by-patient values, we contacted the authors to request data sharing for the current meta-analysis. Studies reporting a relationship between K i -67 index and clinical outcomes in VS for which detailed patients' outcomes or K i -67 indices could not be obtained were incorporated into the descriptive analysis, but excluded from the formal (i.e., quantitative) meta-analysis. Results A systematic review identified 104 candidate citations of which 12 met inclusion criteria. Six of these studies had accessible patient-specific data. Individual patient data were collected from these studies for calculation of discrete study effect sizes, pooling via random-effects modeling with restricted maximum likelihood, and meta-analysis. The standardized mean difference in K i -67 indices between those with and without recurrence was calculated as 0.79% (95% confidence interval [CI]: 0.28-1.30; p = 0.0026). Conclusion K i -67 index may be higher in VSs that demonstrate recurrence/progression following surgical resection. This may represent a promising means of evaluating tumor recurrence and potential need for early adjuvant therapy for VSs.

Classifying the Large Vestibular Aqueduct: Morphometry to Audiometry.

OBJECTIVE: Large vestibular aqueduct (LVA) is the most common inner ear dysplasia identified in patients with hearing loss. Our objective was to systematically quantify LVA morphologies and correlate imaging findings with established audiometric outcomes. STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: Patients with large vestibular aqueduct identified radiographically, with or without hearing loss. INTERVENTIONS: Diagnostic only. MAIN OUTCOME MEASURES: Vestibular aqueduct (VA) width at midpoint, width at external aperture, and length were measured on cross-sectional imaging. Morphology was classified as type I (borderline), type II (tubular), or type III (funneled). Audiometric endpoints included air/bone conduction, pure tone averages, and air-bone gaps at 250 and 500 Hz. Statistical associations were evaluated using linear regression models, adjusted for age at first audiogram and sex. RESULTS: One hundred seventeen patients (197 ears) were included, with mean age at first audiogram of 22.2 years (standard deviation, 21.7 yr). Imaging features associated with poor audiometric outcomes were increasing VA width at midpoint and external aperture, decreasing VA length, dilated extraosseous endolymphatic sac, cochleovestibular malformations, and increasing VA type (III > II > I). CONCLUSIONS: Quantitative LVA measurements and a standardized morphologic classification system aid in prediction of early audiometric endpoints.

Salvage radiosurgery following subtotal resection of vestibular schwannomas: does timing influence tumor control?

OBJECTIVE: The goal of microsurgical resection of vestibular schwannoma (VS) is gross-total resection (GTR) to provide oncological cure. However, a popular strategy is to halt the resection if the surgical team feels the risk of cranial nerve injury is imminent, achieving a maximally safe subtotal resection (STR) instead. The tumor remnant can then be treated with stereotactic radiosurgery (SRS) once the patient has recovered from the immediate postoperative period, or it can be followed with serial imaging and treated with SRS in a delayed fashion if residual tumor growth is seen. In this study, the authors evaluated the efficacy of this multimodality approach, particularly the influence of timing and dose of SRS on radiological tumor control, need for salvage treatment, and cranial nerve function. METHODS: VS patients treated with initial microsurgery and subsequent radiosurgery were retrospectively included from two tertiary treatment centers and dichotomized depending on whether SRS was given upfront (defined as before 12 months) or later. Radiological tumor control was defined as less than 20% tumor volume expansion and oncological tumor control as an absence of salvage treatment. Facial and cochlear nerve functions were assessed after surgery, at the time of SRS, and at last follow-up. Finally, a systematic literature review was conducted according to PRISMA guidelines. RESULTS: A total of 110 VS patients underwent SRS following microsurgical resection, with a mean preradiosurgical tumor volume of 2.2 cm3 (SD 2.5 cm3) and mean post-SRS follow-up time of 5.8 years (SD 4.1 years). The overall radiological tumor control and oncological tumor control were 77.3% and 90.9%, respectively. Thirty-five patients (31.8%) received upfront SRS, while 75 patients (68.2%) were observed for a minimum of 12 months prior to SRS. The timing of SRS did not influence the radiological tumor control (p = 0.869), the oncological tumor control (p = 0.560), or facial nerve (p = 0.413) or cochlear nerve (p = 0.954) function. An escalated marginal dose (> 12 Gy) was associated with greater tumor shrinkage (p = 0.020) and superior radiological tumor control (p = 0.020), but it did not influence the risk of salvage treatment (p = 0.904) or facial (p = 0.351) or cochlear (p = 0.601) nerve deterioration. CONCLUSIONS: Delayed SRS after close observation of residuals following STR is a safe alternative to upfront SRS regarding tumor control and cranial nerve preservation in selected patients.

Fluorescein-Assisted Microsurgical Resection of Vestibular Schwannoma: A Prospective Feasibility Study.

OBJECTIVE: To evaluate the optimal dose and timing of administration of sodium fluorescein (SF) for selective fluorescence of sporadic vestibular schwannoma (VS) during microsurgery with the YELLOW 560-nm microscope filter (YE560) and to characterize the potential benefit of this fluorescence as determined by intraoperative surgeon assessment. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary referral center. PATIENTS: Adult patients undergoing VS microsurgery. INTERVENTIONS: Intraoperative intravenous administration of SF and visualization with the YE560. MAIN OUTCOME MEASURES: Time to differential fluorescence, duration of fluorescence, correlation of fluorescence of VS with electrostimulation and white light microscopy visual assessment, and likelihood of surgeons to use SF with the YE560 in future cases. RESULTS: Novel use of SF and YE560 during microsurgery achieved selective fluorescence of VS with capabilities to differentiate nerve fascicles and tumor approximately 30 minutes after administration. Nuances of SF administration and timing are discussed. Seventy-five percent of surgeons observed an excellent correlation of selective fluorescence with white light microscopy. Representative images and cases are presented. CONCLUSIONS: SF and YE560 may be used in VS microsurgery to visually differentiate VS from surrounding nerves. Potential benefits include enhanced visualization of the tumor-nerve interface for tumor dissection and detection of any residual disease, such as in the fundus after hearing preservation microsurgery.

Right posterior petrosectomy for resection of petroclival meningioma.

Petroclival meningiomas, which arise from the upper two-thirds of the clivus and are medial to the trigeminal nerve, carry significant surgical risk. Patients whose operations are tailored to maximize tumor resection while minimizing neurological morbidity have favorable outcomes. Subtotally resected tumors can be subsequently considered for radiosurgery in an attempt to limit recurrence. Here the authors report the case of a 40-year-old woman with postpartum trigeminal neuropathy secondary to a petroclival meningioma. The patient underwent an aggressive subtotal resection via a posterior petrosal approach with preservation of neurological function followed by adjuvant radiosurgery. The video can be found here: https://stream.cadmore.media/r10.3171/2022.1.FOCVID21227.

Relationship Between Intraoperative Electrocochleography Responses and Immediate Postoperative Bone Conduction Thresholds in Cochlear Implantation.

OBJECTIVE: To determine the relationship between intraoperative electrocochleography (ECochG) measurements and residual hearing preservation after cochlear implant (CI) surgery by comparing differences between preoperative and immediate postoperative bone conduction thresholds. STUDY DESIGN: Prospective cohort study. SETTING: Tertiary academic referral center. PATIENTS: Sixteen patients with preoperative residual hearing and measurable (no-vibrotactile) bone conduction thresholds at 250 and/or 500 Hz who underwent cochlear implantation. MAIN OUTCOME MEASURE: Intraoperative ECochG and air and bone conduction thresholds. RESULTS: Nine patients showed no significant drop (<30%) in ECochG amplitude during CI surgery with an average preoperative and immediate postoperative BC threshold of 46 and 39 dB HL, respectively, at 500 Hz. Seven patients with a decrease in ECochG amplitude of 30% or greater showed an average preoperative 500 Hz BC threshold of 32 dB HL and immediate postoperative threshold of 55 dB HL. Air and bone conduction thresholds measured approximately 1 month after CI surgery show delayed-onset of hearing loss across our study patients. CONCLUSIONS: A small decrease (<30%) in difference response or cochlear microphonics amplitude correlates with no significant changes in immediate postoperative residual hearing, whereas patients who show larger changes (≥30%) in difference response or cochlear microphonics amplitude during intraoperative ECochG measurements show significant deterioration in BC thresholds. This study reveals the necessity of prompt postoperative bone conduction measurement to isolate the intraoperative cochlear trauma that may be detected during intraoperative ECochG measurements. Although delayed postoperative audiometrics represent longer-term functional hearing, it includes the sum of all postoperative changes during the recovery period, including subacute changes after implantation that may occur days or weeks later. Measuring air and bone conduction thresholds immediately postoperatively will better isolate factors influencing intraoperative, early postoperative, and delayed postoperative hearing loss. This will ultimately help refine surgical technique, device design, and highlight the use of intraoperative ECochG in monitoring cochlear trauma during CI surgery.

Implementation Strategy for Highly-Coordinated Cochlear Implant Care With Remote Programming: The Complete Cochlear Implant Care Model.

OBJECTIVE: To introduce and discuss implementation strategy for the Complete Cochlear Implant Care (CCIC) model, a highly-coordinated cochlear implant (CI) care delivery model requiring a single on-site visit for preoperative workup, surgery, and postoperative programming. STUDY DESIGN: Prospective, nonrandomized, two-arm clinical trial. SETTING: Tertiary referral CI center. PATIENTS: Adults who meet audiologic criteria for cochlear implantation. INTERVENTIONS: Cochlear implantation, coordinated care delivery, including remote programming. MAIN OUTCOME MEASURES: Care delivery model feasibility and process implementation. RESULTS: Patients determined to be likely CI candidates based on routine audiometry are eligible for enrollment. The CCIC model uses telemedicine and electronic educational materials to prepare patients for same-day on-site consultation with CI surgery, same or next-day activation, and postoperative remote programming for 12 months. Implementation challenges include overcoming inertia related to the implementation of a new clinical workflow, whereas scalability of the CCIC model is limited by current hardware requirements for remote programming technology. A dedicated CCIC process coordinator is critical for overcoming obstacles in implementation and process improvement through feedback and iterative changes. Team and patient-facing materials are included and should be tailored to fit each unique CI program looking to implement CCIC. CONCLUSION: The CCIC model has the potential to dramatically streamline hearing healthcare delivery. Implementation requires an adaptive approach, as obstacles may vary according to institutional infrastructure and policies.

Predicting Extent of Microsurgical Resection of Sporadic Vestibular Schwannoma.

OBJECTIVE: Develop a predictive model for incomplete microsurgical resection of sporadic vestibular schwannoma (VS). STUDY DESIGN: Historical cohort. SETTING: Tertiary referral center. PATIENTS: Patients with sporadic VS. INTERVENTIONS: Microsurgery with preoperative intent of gross total resection. MAIN OUTCOME MEASURES: Patient and tumor characteristics that influence extent of resection. RESULTS: Among 603 patients, 101 (17%) had intracanalicular tumors and 502 (83%) had tumors with cerebellopontine angle (CPA) extension. For patients with CPA tumors, 331 (66%) underwent gross total resection and 171 (34%) underwent near-total or subtotal resection (NTR-STR). Multivariable modeling identified older age at surgery, larger linear tumor size, and absence of a fundal fluid cap as predictive of NTR-STR ( p < 0.001). From this model, one can estimate that a 20-year-old with a tumor that has less than 10 mm of CPA extension and a present fundal fluid cap has a predicted probability of NTR-STR of 0.01 (or 1%), whereas a 70-year-old with a tumor that has 30 mm or greater CPA extension and absence of a fundal fluid cap has a predicted probability of NTR-STR of 0.91 (or 91%). Among the 171 patients who underwent NTR-STR, 24 required secondary treatment at the time of last follow-up. CONCLUSION: The primary predictors of incomplete microsurgical resection of VS include older age at surgery, larger linear tumor size, and absence of a fundal fluid cap. These factors can be used to estimate the likelihood of NTR-STR, aiding in preoperative discussions regarding future surveillance and potential need of secondary treatment, as well as shared clinical decision making.

Three-Dimensional Modeling for Augmented and Virtual Reality-Based Posterior Fossa Approach Selection Training: Technical Overview of Novel Open-Source Materials.

BACKGROUND: Selection of skull base approaches is a critical skill for complex cranial surgery, which demands nuanced understanding of neuroanatomy and pathology. OBJECTIVE: To develop novel pedagogical resources for approach selection education and assessment. METHODS: A prospectively maintained skull base registry was screened for posterior fossa tumors amenable to 3-dimensional (3D) modeling of multiple operative approaches. Inclusion criteria were high-resolution preoperative and postoperative computed tomography and MRI studies (≤1 mm) and consensus that at least 3 posterior fossa craniotomies would provide feasible access. Cases were segmented using Mimics and modeled using 3-Matic. Clinical Vignettes, Approach Selection Questionnaire, and Clinical Application Questionnaire were compiled for implementation as a teaching/testing tool. RESULTS: Seven cases were selected, each representing a major posterior fossa approach group. 3D models were rendered using clinical imaging for the primary operative approach, as well as a combination of laboratory neuroanatomic data and extrapolation from comparable craniotomies to generate 2 alternative approaches in each patient. Modeling data for 3D figures were uploaded to an open-sourced database in a platform-neutral fashion (.x3d) for virtual/augmented reality and 3D printing applications. A semitransparent model of each approach without pathology and with key deep structures visualized was also modeled and included for comprehensive understanding. CONCLUSION: We report a novel series of open-source 3D models for skull base approach selection training, with supplemental resources. To the best of our knowledge, this is the first such series designed for pedagogical purposes in skull base surgery or centered on open-source principles.

Cerebrovascular Complications of Vestibular Schwannoma Surgery.

Objective Cerebrovascular complications (CVC) are rare consequences of vestibular schwannoma (VS) surgery. Our objective was to assess incidences of findings suggestive of postoperative CVC in a large single surgeon cohort, as well as potential risk factors, and implications. Study Design A cohort of 591 patients was retrospectively reviewed. Postoperative magnetic resonance images were screened for findings suggestive of stroke, T2 hyperintensity in the cerebellopontine angle structures or new encephalomalacia. Clinical records were queried for findings consistent with postoperative CVC. Results In total, 61 patients had radiographic findings consistent with possible postoperative CVC (10%); of them, eight had documented intraoperative vascular injury (1.4%), and four had postoperative clinical exam changes indicative of CVC (0.7%). Clinically manifest intraoperative vascular injuries occurred in four patients and involved the petrosal venous complex ( n = 3, 5%) or anterior inferior cerebellar artery ( n = 1, 2%); clinical deficits included hemiparesis ( n = 1, 2%), facial anesthesia ( n = 2, 4%), dysphagia ( n = 2, 2%), and unfavorable facial nerve function in two (50%). Three out of four patients in this group required out-of-home placement (75%). Clinical CVCs ( n = 4) were not significantly associated with tumor size, tumor cyst, gross total resection, or length of stay. Patients with clinical CVC were significantly more likely to require posthospitalization rehabilitation (19 vs. 75%, p = 0.02; 14 vs. 100%, p = 0.0002). Conclusion Although radiographic findings suggestive of CVC were unexpectedly common in this cohort, intraoperative vascular injury and postoperative clinical CVC were exceedingly rare. The association between unfavorable facial nerve outcome and clinical CVC is likely a marker for more difficult operations, predisposing to higher risk of complications.

3D Printing for Complex Cranial Surgery Education: Technical Overview and Preliminary Validation Study.

Background 3D printing-also known as additive manufacturing-has a wide range of applications. Reproduction of low-cost, high-fidelity, disease- or patient-specific models presents a key developmental area in simulation and education research for complex cranial surgery. Methods Using cadaveric dissections as source materials, skull base models were created, printed, and tested for educational value in teaching complex cranial approaches. In this pilot study, assessments were made on the value of 3D printed models demonstrating the retrosigmoid and posterior petrosectomy approaches. Models were assessed and tested in a small cohort of neurosurgery resident subjects ( n = 3) using a series of 10 radiographic and 2 printed case examples, with efficacy determined via agreement survey and approach selection accuracy. Results All subjects indicated agreement or strong agreement for all study endpoints that 3D printed models provided significant improvements in understanding of neuroanatomic relationships and principles of approach selection, as compared to 2D dissections or patient cross-sectional imaging alone. Models were not superior to in-person hands-on teaching. Mean approach selection accuracy was 90% (±13%) for 10 imaging-based cases, or 92% (±7%) overall. Trainees strongly agreed that approach decision-making was enhanced by adjunctive use of 3D models for both radiographic and printed cases. Conclusion 3D printed models incorporating skull base approaches and/or pathologies provide a compelling addition to the complex cranial education armamentarium. Based on our preliminary analysis, 3D printed models offer substantial potential for pedagogical value as dissection guides, adjuncts to preoperative study and case preparation, or tools for approach selection training and evaluation.