The Vestibular Schwannoma Surgery Learning Curve Mapped by the Cumulative Summation Test for Learning Curve

Translabyrinthine versus Retrosigmoid Approach for Vestibular Schwannoma: A Systematic Review and An Updated Meta-Analysis

OBJECTIVE

Several approaches can be used in the surgical treatment of vestibular schwannoma (VS), and the best approach remains uncertain in the literature. This systematic review and meta-analysis aim to compare the translabyrinthine approach (TLA) with the retrosigmoid approach (RSA) for VS in terms of postoperative complications.

DATA SOURCES

PubMed, Web of Science, Embase, and Cochrane.

REVIEW METHODS

The primary outcome was cerebrospinal fluid (CSF) leak; secondary outcomes were facial nerve dysfunction (FND), length of stay (LOS), and meningitis. Statistical analysis was performed using RStudio 2024.04.1 + 748. Heterogeneity was assessed with I² statistics. We performed sensitivity analysis with subgroup analysis and meta-regression. Risk of bias was assessed using ROBINS-I.

RESULTS

Out of 1140 potential articles, 21 met the inclusion criteria. Among the 4572 patients, 2687 and 1885 patients in the TLA and RSA groups, respectively. No significant differences were found in CSF leak (odds ratio [OR] 1.03; 95% confidence interval [CI] 0.81,1.32; P = .794) or meningitis (OR 1.05; 95% CI 0.45, 2.43; P = .73). Meta-regression showed no association with CSF leak and the number of cases per center or publication year. The TLA is associated with a shorter LOS (MD -1.20; 95% CI -1.39, -1.01; P < .01) and a higher chance of having and HB 4 or lower compared to patients who underwent RSA (OR 0.30; 95% CI 0.10, 0.89; P = .03).

CONCLUSION

There was no difference in the odds of CSF leak or meningitis between the groups. In addition, the TLA has a shorter LOS and a higher chance of a better facial nerve outcome compared to the RSA.

Is There a Plateau to the Learning Curve for Acoustic Neuroma Resection?-Experience and Outcomes from a Single Interdisciplinary Team Over Thirty Years

Objective  The evolution of acoustic neuroma (AN) care continues to shift focus on balancing optimized tumor resection and control with preservation of neurological function. Prior learning curve analyses of AN resection have demonstrated a plateau between 20 and 100 surgeries. In this study of 860 consecutive AN surgeries, we investigate the presence of an extended learning curve tail for AN resection. Methods  A retrospective cohort study of AN resections by a single interdisciplinary team between 1988 and 2018 was performed. Proportional odds models and restricted cubic splines were used to determine the association between the timing of surgery and odds of improved postoperative outcomes. Results  The likelihood of improved postoperative House-Brackmann (HB) scores increased in the first 400 procedures, with HB 1 at 36% in 1988 compared with 79% in 2004. While the probability of a better HB score increased over time, there was a temporary decrease in slope of the cubic spline between 2005 and 2009. The last 400 cases continued to see improvement in optimal HB outcomes: adjusted odds of HB 1 score were twofold higher in both 2005 to 2009 (adjusted odds ratio [aOR]: 2.11, 95% confidence interval [CI]: 1.38-3.22, p  < 0.001) and 2010 to 2018 (aOR: 2.18, 95% CI: 1.49-3.19, p  < 0.001). Conclusion  In contrast to prior studies, our study demonstrates the steepest growth for learning, as measured by rates of preservation of facial function outcomes (HB 1), occurs in the first 400 AN resections. Additionally, improvements in patient outcomes continued even 30 years into practice, underlining the importance of lifelong learning.

Generating Operative Workflows for Vestibular Schwannoma Resection: A Two-Stage Delphi's Consensus in Collaboration with the British Skull Base Society. Part 1: The Retrosigmoid Approach

Objective  An operative workflow systematically compartmentalizes operations into hierarchal components of phases, steps, instrument, technique errors, and event errors. Operative workflow provides a foundation for education, training, and understanding of surgical variation. In this Part 1, we present a codified operative workflow for the retrosigmoid approach to vestibular schwannoma resection. Methods  A mixed-method consensus process of literature review, small-group Delphi's consensus, followed by a national Delphi's consensus, was performed in collaboration with British Skull Base Society (BSBS). Each Delphi's round was repeated until data saturation and over 90% consensus was reached. Results  Eighteen consultant skull base surgeons (10 neurosurgeons and 8 ENT [ear, nose, and throat]) with median 17.9 years of experience (interquartile range: 17.5 years) of independent practice participated. There was a 100% response rate across both Delphi's rounds. The operative workflow for the retrosigmoid approach contained three phases and 40 unique steps as follows: phase 1, approach and exposure; phase 2, tumor debulking and excision; phase 3, closure. For the retrosigmoid approach, technique, and event error for each operative step was also described. Conclusion  We present Part 1 of a national, multicenter, consensus-derived, codified operative workflow for the retrosigmoid approach to vestibular schwannomas that encompasses phases, steps, instruments, technique errors, and event errors. The codified retrosigmoid approach presented in this manuscript can serve as foundational research for future work, such as operative workflow analysis or neurosurgical simulation and education.

Postoperative intracerebral haematomas following stereotactic biopsies: Poor planning or poor execution?

BACKGROUND

Postoperative intracerebral haematomas represent a serious complication following stereotactic biopsy. We investigated the possible underlying causes - poor planning or poor execution - of postoperative intracerebral haematomas following stereotactic biopsies.

METHODS

We performed a technical investigation using a retrospective single-centre consecutive series of robot-assisted stereotactic biopsies for a supratentorial diffuse glioma in adults. Each actual biopsy trajectory was reviewed to search for a conflict with an anatomical structure at risk.

RESULTS

From 379 patients, 12 (3.2%) presented with a postoperative intracerebral haematoma ≥20 mm on postoperative CT-scan (3 requiring surgical evacuation); 11 of them had available intraoperative imaging (bi-planar stereoscopic teleangiography x-rays at each biopsy site). The actual biopsy trajectory was similar to the planned biopsy trajectory in these 11 cases. In 72.7% (8/11) of these cases, the actual biopsy trajectory was found to contact a structure at risk (blood vessel and cerebral sulcus) and identified as the intracerebral haematoma origin.

CONCLUSIONS

Robot-assisted stereotactic biopsy is an accurate procedure. Postoperative intracerebral haematomas mainly derive from human-related errors during trajectory planning.

Vestibular Schwannoma Surgery: Outcome and Complications in Lateral Decubitus Position versus Semi-sitting Position-A Personal Learning Curve in a Series of 544 Cases over 3 Decades

OBJECTIVE

To retrospectively evaluate influence of intraoperative positioning (semisitting vs. lateral decubitus) and surgeon's learning curve with regard to functional outcome of patients with vestibular schwannoma.

METHODS

This study included 544 patients (median age 57 years) and spanned 3 decades: 1991-1999 (n = 103), 2000-2009 (n = 210), and 2010-2019 (n = 231). Surgery was performed in the lateral decubitus position in 318 patients and the semisitting position in 163 patients. Large T3 and T4 tumors were present in 77% of patients.

RESULTS

Complete tumor removal was achieved in 94.3% of patients. A significant reduction in surgery duration and blood loss was observed over 3 decades for T3 (from 325 to 261 minutes, P < 0.001) and T4 (from 440 to 330 minutes, P < 0.001), but not for T1 and T2, tumors. The semisitting position diminished surgical time in T3 and T4 tumors by 1 more hour (P < 0.001). Over 3 decades, facial nerve outcome improved significantly from 59.8% House-Brackmann grade 1-2 in the first decade to 81.7% in the last decade (P < 0.001). Furthermore, hearing was preserved in 45.3%: 23.3% of patients in the first decade and 50.5% in the last decade (P = 0.03). However, neither facial nerve outcome nor hearing preservation significantly differed in patients operated on in the lateral decubitus versus the semisitting position. The most common complication was cerebrospinal fluid leak (6.1%) followed by hemorrhage (3.5%) and pulmonary embolism (2.2%).

CONCLUSIONS

Follow-up over 3 decades illustrates a learning curve with significantly improved results. While the semisitting position accelerates the procedure and is associated with reduced blood loss, it does not significantly influence functional outcome.

Postoperative Hearing Preservation in Patients Undergoing Retrosigmoid Craniotomy for Resection of Vestibular Schwannomas: A Systematic Review of 2034 Patients

BACKGROUND

Vestibular schwannomas (VS) are benign tumors derived from Schwann cells ensheathing the vestibulocochlear nerve. The retrosigmoid (RS) surgical approach is useful to resect tumors of multiple sizes while affording the possibility of preserving postoperative hearing.

OBJECTIVE

To conduct a systematic review of published literature investigating hearing preservation rates in patients who underwent the RS approach for VS treatment.

METHODS

The PubMed, Scopus, and Embase databases were surveyed for studies that reported preoperative and postoperative hearing grades on VS patients who underwent RS treatment. Hearing preservation rates were calculated, and additional patient demographic data were extracted. Tumor size data were stratified to compare hearing preservation rates after surgery for intracanalicular, small (0-20 mm), and large (>20 mm) tumors.

RESULTS

Of 383 deduplicated articles, 26 studies (6.8%) met eligibility criteria for a total of 2034 patients with serviceable preoperative hearing, for whom postoperative hearing status was evaluated. Aggregate hearing preservation was 31% and 35% under a fixed and random effects model, respectively. A mixed effects model was used to determine hearing preservation rates depending on tumor size, which were determined to be 57%, 37%, and 12% for intracanalicular, small, and large tumors, respectively. Significant cross-study heterogeneity was found (I2 = 93%, τ2 = .964, P < .01; Q = 287.80, P = < .001), with rates of hearing preservation ranging from 0% to 100%.

CONCLUSION

Tumor size may have an effect on hearing preservation rates, but multiple factors should be considered. Discussion of a patient's expectations for hearing preservation is critical when deciding on VS treatment plans.

The predictive value of preoperative apparent diffusion coefficient (ADC) for facial nerve outcomes after vestibular schwannoma resection: clinical study

OBJECT

Diffusion MRI has been used to predict intraoperative consistency of tumors. Apparent diffusion coefficient (ADC) has shown predictive value as an imaging biomarker in many CNS tumors but has not been studied in a large cohort of patients with vestibular schwannoma. In this study, we examine the utility of ADC as a predictive biomarker for intraoperative tumor characteristics and postoperative facial nerve outcome.

METHODS

A retrospective review of patients who underwent vestibular schwannoma resection at our institution from 2008 to 2018 yielded 87 patients, of which 72 met inclusion criteria. Operative reports and clinical records were reviewed for clinical data; MRI data were interpreted in a blinded fashion for qualitative and quantitative biomarkers, including tumor ADC.

RESULTS

Mean tumor ADC values did not predict intraoperative consistency or adherence (p = 0.63). Adherent tumors were associated with worse facial nerve outcomes (p = 0.003). Regression tree analysis identified 3 ADC categories with statistically different facial nerve outcomes. The categories identified were ADC < 1006.04 × 10^-6 mm^2/s; ADC 1006.04-1563.93 × 10^-6 mm^2/s and ADC ≥ 1563.94 × 10^-6 mm^2/s. Postoperative and final House-Brackmann (HB) scores were significantly higher in the intermediate ADC group (2.3, p = 0.0038). HB outcomes were similar between the group with ADC < 1006.04 × 10^-6 mm^2/s and ≥ 1563.94 × 10^-6 mm^2/s (1.3 vs 1.3).

CONCLUSIONS

Middle-range preoperative ADC in vestibular schwannoma suggests a less favorable postoperative HB score. Preoperative measurement of ADC in vestibular schwannoma may provide additional information regarding prognostication of facial nerve outcomes.

Does Hospital Volume Affect Outcomes in Patients Undergoing Vestibular Schwannoma Surgery?

OBJECTIVE

To determine the effect of hospital surgical case volume on the outcomes of vestibular schwannoma surgery.

STUDY DESIGN

Retrospective case review.

SETTING

University HealthSystem Consortium member hospitals (includes nearly every US academic medical center).

PATIENTS

Three thousand six hundred ninety-seven patients who underwent vestibular schwannoma resection over a 3-year timespan (2012-2015) grouped by race, age, comorbidities, payer, and sex.

INTERVENTION

Surgical resection of vestibular schwannoma.

MAIN OUTCOME MEASURES

Morbidity and mortality following vestibular schwannoma excision are compared by hospital volume (low, medium, and high) including deciles.

RESULTS

There was significantly longer length of stay (p ≤ 0.005) among groups with low-volume hospitals followed by medium-volume hospitals and high-volume hospitals. Low-volume hospitals had a significantly higher rate of complications including stroke, aspiration, and respiratory failure (p ≤ 0.0175). Patient characteristics of age, sex, sex, and baseline comorbidities were similar between hospital groups. However, patients at high-volume hospitals were more likely to be Caucasian (83.1%, p = 0.0001) and have private insurance (76.7%, p < 0.0001). There was a strong negative correlation between complication rates and hospital volume (r = -0.8164, p = 0.0040).

CONCLUSION

The volume of vestibular schwannoma surgeries performed at a hospital impacts length of stay and rates of postoperative complications. Demographics among hospital groups were similar though high-volume hospitals had significantly more patients who were privately insured and Caucasian.

Translabyrinthine microsurgical resection of small vestibular schwannomas

OBJECTIVE

Translabyrinthine resection is one of a number of treatment options available to patients with vestibular schwannomas. Though this procedure is hearing destructive, the authors have noted excellent clinical outcomes for patients with small tumors. The authors review their experience at a tertiary acoustic neuroma referral center in using the translabyrinthine approach to resect small vestibular schwannomas. All operations were performed by a surgical team consisting of a single neurosurgeon and 1 of 7 neurotologists.

METHODS

Data from a prospectively maintained clinical database were extracted and reviewed. Consecutive patients with a preoperative diagnosis of vestibular schwannoma that had less than 1 cm of extension into the cerebellopontine angle, operated on between 2008 and 2013, were included. Patents with neurofibromatosis Type 2, previous treatment, or preexisting facial weakness were excluded. In total, 107 patients were identified, 74.7% of whom had poor hearing preoperatively.

RESULTS

Pathologically, 6.5% of patients were found to have a tumor other than vestibular schwannoma. Excluding two malignancies, the tumor control rates were 98.7%, as defined by absence of radiographic disease, and 99.0%, as defined by no need for additional treatment. Facial nerve outcome was normal (House-Brackmann Grade I) in 97.2% of patients and good (House-Brackmann Grade I–II) in 99.1%. Complications were cerebrospinal fluid leak (4.7%) and sigmoid sinus thrombosis (0.9%), none of which led to long-term sequelae.

CONCLUSIONS

Translabyrinthine resection of small vestibular schwannomas provides excellent results in terms of complication avoidance, tumor control, and facial nerve outcomes. This is a hearing-destructive operation that is advocated for selected patients.

Early-Career Surgical Practice for Cerebellopontine Angle Tumors in the Era of Radiosurgery

We analyzed the outcomes of patients with large cerebellopontine angle (CPA) tumors treated by a skull-base team in which two surgeons (one neurosurgeon and one otological surgeon) were in the beginning of their careers (<40 years old). Data of patients operated on between April 2012 and March 2016 were reviewed. All factors related to surgical training were considered. Thirty-one patients had vestibular schwannomas, while 26 had meningiomas. Mean tumor diameter was 30.6 mm (range, 23-49 mm) for schwannomas and 35 mm (range, 22-51 mm) for meningiomas. Satisfactory postoperative facial nerve function (House-Brackmann's grade I or II) was achieved in 20 (64.5%) schwannoma patients and 21 (80.7%) meningioma patients. Gross total and near-total resections (residual tumor < 5 mm) were achieved in 21 (67.7%) and 9 (29%) schwannoma patients, respectively. Gross total resection (Simpson's grade II) was achieved in 18 (69.2%) meningioma patients. In both groups, the retrosigmoid approach was the most common approach. Regarding surgical training of the two younger surgeons, during the residency period, they attended high-volume centers for CPA tumors. Application of microsurgical techniques was systematically applied from the beginning of their personal series in every intracranial pathology case. During the first 2 years of the series, they were supervised by more experienced surgeons and followed a stepwise sharing of increasingly difficult surgical phases; by comparing results of this period with the last 2 years of the series, where they acquired a complete autonomy, no relevant difference was detected. Our results suggest that young surgeons may achieve good results even at the beginning of their careers, if specific conditions related to training and mentorship are met.

Training Performance in Diagnosis of Congenital Uterine Anomalies With 3-Dimensional Sonography: A Learning Curve Cumulative Summation Analysis

OBJECTIVES

We evaluated learning curve cumulative summation (CUSUM) of 3-dimensional (3D) sonography for diagnosis of congenital uterine anomalies and the deviations of the level of trainees' performance at the control-stage CUSUM.

METHODS

First-year (R1), second-year (R2), and third-year (R3) residents in obstetrics and gynecology received a training program to learn how to analyze 3D sonographic volumes and to classify congenital uterine anomalies. Each trainee worked on 155 3D sonographic volumes from preselected patients. Their results were evaluated by learning curve CUSUM and standard CUSUM. The time for each volume analysis was calculated for the expert examiner and the trainees.

RESULTS

Trainees R1, R2, and R3 reached competence at the 85th, 58th, and 40th evaluations, respectively, with success rates of 80%, 81%, and 85%, and kept the process under control with error levels of less than 4.5% until the end of the test. The trainees significantly reduced the average time of the evaluation per volume (P < .001).

CONCLUSIONS

Learning curve CUSUM provided quantitative indicators of the learning evolution of 3D sonography for diagnosis of congenital uterine anomalies by obstetrics and gynecology residents. The training received by the residents was adequate for diagnosis of congenital uterine anomalies using 3D sonography.

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

Object

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

Methods

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

Results

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

Conclusions

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