Driscoll, Colin L. W.

OBJECTIVE Preoperative differentiation of facial nerve schwannoma (FNS) from vestibular schwannoma (VS) can be challenging, and failure to differentiate between these two pathologies can result in potentially avoidable facial nerve injury. This study presents the combined experience of two high-volume centers in the management of intraoperatively diagnosed FNSs. The authors highlight clinical and imaging features that can distinguish FNS from VS and provide an algorithm to help manage intraoperatively diagnosed FNS. METHODS Operative records of 1484 presumed sporadic VS resections between January 2012 and December 2021 were reviewed, and patients with intraoperatively diagnosed FNSs were identified. Clinical data and preoperative imaging were retrospectively reviewed for features suggestive of FNS, and factors associated with good postoperative facial nerve function (House-Brackmann [HB] grade ≤ 2) were identified. A preoperative imaging protocol for suspected VS and recommendations for surgical decision-making following an intraoperative FNS diagnosis were created. RESULTS Nineteen patients (1.3%) with FNSs were identified. All patients had normal facial motor function preoperatively. In 12 patients (63%), preoperative imaging demonstrated no features suggestive of FNS, with the remainder showing subtle enhancement of the geniculate/labyrinthine facial segment, widening/erosion of the fallopian canal, or multiple tumor nodules in retrospect. Eleven (57.9%) of the 19 patients underwent a retrosigmoid craniotomy, and in the remaining patients, a translabyrinthine (n = 6) or transotic (n = 2) approach was used. Following FNS diagnosis, 6 (32%) of the tumors underwent gross-total resection (GTR) and cable nerve grafting, 6 (32%) underwent subtotal resection (STR) and bony decompression of the meatal facial nerve segment, and 7 (36%) underwent bony decompression only. All patients undergoing subtotal debulking or bony decompression exhibited normal postoperative facial function (HB grade I). At the last clinical follow-up, patients who underwent GTR with a facial nerve graft had HB grade III (3 of 6 patients) or IV facial function. Tumor recurrence/regrowth occurred in 3 patients (16%), all of whom had been treated with either bony decompression or STR. CONCLUSIONS Intraoperative diagnosis of an FNS during a presumed VS resection is rare, but its incidence can be reduced further by maintaining a high index of suspicion and undertaking further imaging in patients with atypical clinical or imaging features. If an intraoperative diagnosis does occur, conservative surgical management with bony decompression of the facial nerve only is recommended, unless there is significant mass effect on surrounding structures.

Intraoperative electrocochleography (ECOG) is performed using a single low-frequency acoustic stimulus (e.g., 500 Hz) to monitor cochlear microphonics (CM) during cochlear implant (CI) electrode insertion. A decrease in CM amplitude is commonly associated with cochlear trauma and is used to guide electrode placement. However, advancement of the recording electrode beyond the sites of CM generation can also lead to a decrease in CM amplitude and is sometimes interpreted as cochlear trauma, resulting in unnecessary electrode manipulation and increased risk of cochlear trauma during CI electrode placement. In the present study, multi-frequency ECOG was used to monitor CM during CI electrode placement. The intraoperative CM tracings were compared with electrode scan measurements, where CM was measured for each of the intracochlear electrodes. Comparison between the peak CM amplitude measured during electrode placement and electrode scan measurements was used to differentiate between different mechanisms for decrease in CM amplitude during CI electrode insertion. Analysis of the data shows that both multi-frequency electrocochleography and electrode scan could potentially be used to differentiate between different mechanisms for decreasing CM amplitude and providing appropriate feedback to the surgeon during CI electrode placement.

Objective To characterize the effect of the COVID-19 pandemic on national cochlear implantation utilization by age using inclusive cochlear implantation data from two manufacturers between 2015 and 2020. Study Design Analysis of prospectively registered consecutive patient data from two major cochlear implant (CI) manufacturers in the United States. Patients Children or adults who received CIs. Interventions Cochlear implantation. Main Outcome Measures Annual implantation utilization by age. Results A total of 46,804 patients received CIs from the two participating manufacturers between 2015 and 2020. The annual number of implant recipients increased significantly during the first 5 years of the study period for both children and adults, from a total of 6,203 in 2015 to 9,213 in 2019 (p < 0.001). During 2020, there was a 13.1% drop in national cochlear implantation utilization across all ages compared with 2019, including a drop of 2.2% for those ≤3 years old, 3.8% for those 4–17 years old, 10.1% for those 18–64 years old, 16.6% for those 65–79 years old, and 22.5% for those ≥80 years old. In a multivariable linear regression model, the percent drop in CIs differed significantly by age-group (p = 0.005). Conclusions Especially in light of the prepandemic projected CI counts for 2020, the COVID-19 pandemic reduced national cochlear implantation utilization by over 15% among Medicare-aged patients and by almost 25% among those ≥80 years old, resulting in more than a 3-year setback in total annual CIs. Children were less affected, with those ≤3 years old experiencing minimal interruption during 2020.

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. Intervention(s) Diagnostic only. Main Outcome Measure(s) 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.

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.

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.

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.