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Jacob Ruzevick, Tyler Cardinal, Dhiraj J. Pangal, Ilaria Bove, Ben Strickland, and Gabriel Zada

OBJECTIVE

Intraoperative use of the endoscope to assist in visualization of intracranial tumor pathology has expanded with increasing surgeon experience and improved instrumentation. The authors aimed to study how advancements in endoscopic technology have affected the evolution of endoscope use, with particular focus on blue light–filter modification allowing for discrimination of fluorescent tumor tissue following 5-ALA administration.

METHODS

A retrospective analysis of patients undergoing craniotomy for tumor resection at a single institution between February 2012 and July 2021 was performed. Patients were included if the endoscope was used for diagnostic tumor cavity inspection or therapeutic assistance with tumor resection following standard craniotomy and microsurgical tumor resection, with emphasis on those cases in which blue light endoscopy was used. Medical records were queried for patient demographics, operative reports describing the use of the endoscope and extent of resection, associations with tumor pathology, and postoperative outcomes. Preoperative and postoperative MR images were reviewed for radiographic extent of resection.

RESULTS

A total of 52 patients who underwent endoscope-assisted craniotomy for tumor were included. Thirty patients (57.7%) were men and the average age was 52.6 ± 16.1 years. Standard white light endoscopes were used for assistance with tumor resection in 28 cases (53.8%) for tumors primarily located in the ventricular system, parasellar region, and cerebellopontine angle. A blue light endoscope for detection of 5-ALA fluorescence was introduced into our practice in 2014 and subsequently used for assistance with tumor resection in 24 cases (46.2%) (intraaxial: n = 22, extraaxial: n = 2). Beyond the use of the surgical microscope as the primary visualization source, the blue light endoscope was used to directly perform additional tumor resection in 19/21 cases as a result of improved fluorescence detection as compared to the surgical microscope. No complications were associated with the use of the endoscope or with additional resection performed under white or blue light visualization.

CONCLUSIONS

Endoscopic assistance to visualize intracranial tumors had previously been limited to white light, assisting mostly in the visualization of extraaxial tumors confined to intraventricular and cisternal compartments. Blue light–equipped endoscopes provide improved versatility and visualization of 5-ALA fluorescing tissue beyond the capability of the surgical microscope, thereby expanding its use into the realm of intraaxial tumor resections.

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Vyom Unadkat, Dhiraj J. Pangal, Guillaume Kugener, Arman Roshannai, Justin Chan, Yichao Zhu, Nicholas Markarian, Gabriel Zada, and Daniel A. Donoho

OBJECTIVE

While the utilization of machine learning (ML) for data analysis typically requires significant technical expertise, novel platforms can deploy ML methods without requiring the user to have any coding experience (termed AutoML). The potential for these methods to be applied to neurosurgical video and surgical data science is unknown.

METHODS

AutoML, a code-free ML (CFML) system, was used to identify surgical instruments contained within each frame of endoscopic, endonasal intraoperative video obtained from a previously validated internal carotid injury training exercise performed on a high-fidelity cadaver model. Instrument-detection performances using CFML were compared with two state-of-the-art ML models built using the Python coding language on the same intraoperative video data set.

RESULTS

The CFML system successfully ingested surgical video without the use of any code. A total of 31,443 images were used to develop this model; 27,223 images were uploaded for training, 2292 images for validation, and 1928 images for testing. The mean average precision on the test set across all instruments was 0.708. The CFML model outperformed two standard object detection networks, RetinaNet and YOLOv3, which had mean average precisions of 0.669 and 0.527, respectively, in analyzing the same data set. Significant advantages to the CFML system included ease of use, relatively low cost, displays of true/false positives and negatives in a user-friendly interface, and the ability to deploy models for further analysis with ease. Significant drawbacks of the CFML model included an inability to view the structure of the trained model, an inability to update the ML model once trained with new examples, and the inability for robust downstream analysis of model performance and error modes.

CONCLUSIONS

This first report describes the baseline performance of CFML in an object detection task using a publicly available surgical video data set as a test bed. Compared with standard, code-based object detection networks, CFML exceeded performance standards. This finding is encouraging for surgeon-scientists seeking to perform object detection tasks to answer clinical questions, perform quality improvement, and develop novel research ideas. The limited interpretability and customization of CFML models remain ongoing challenges. With the further development of code-free platforms, CFML will become increasingly important across biomedical research. Using CFML, surgeons without significant coding experience can perform exploratory ML analyses rapidly and efficiently.

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Dhiraj J. Pangal, David J. Cote, Jacob Ruzevick, Benjamin Yarovinsky, Guillaume Kugener, Bozena Wrobel, Elisabeth H. Ference, Mark Swanson, Andrew J. Hung, Daniel A. Donoho, Steven Giannotta, and Gabriel Zada

OBJECTIVE

The utility of robotic instrumentation is expanding in neurosurgery. Despite this, successful examples of robotic implementation for endoscopic endonasal or skull base neurosurgery remain limited. Therefore, the authors performed a systematic review of the literature to identify all articles that used robotic systems to access the sella or anterior, middle, or posterior cranial fossae.

METHODS

A systematic review of MEDLINE and PubMed in accordance with PRISMA guidelines performed for articles published between January 1, 1990, and August 1, 2021, was conducted to identify all robotic systems (autonomous, semiautonomous, or surgeon-controlled) used for skull base neurosurgical procedures. Cadaveric and human clinical studies were included. Studies with exclusively otorhinolaryngological applications or using robotic microscopes were excluded.

RESULTS

A total of 561 studies were identified from the initial search, of which 22 were included following full-text review. Transoral robotic surgery (TORS) using the da Vinci Surgical System was the most widely reported system (4 studies) utilized for skull base and pituitary fossa procedures; additionally, it has been reported for resection of sellar masses in 4 patients. Seven cadaveric studies used the da Vinci Surgical System to access the skull base using alternative, non–TORS approaches (e.g., transnasal, transmaxillary, and supraorbital). Five cadaveric studies investigated alternative systems to access the skull base. Six studies investigated the use of robotic endoscope holders. Advantages to robotic applications in skull base neurosurgery included improved lighting and 3D visualization, replication of more traditional gesture-based movements, and the ability for dexterous movements ordinarily constrained by small operative corridors. Limitations included the size and angulation capacity of the robot, lack of drilling components preventing fully robotic procedures, and cost. Robotic endoscope holders may have been particularly advantageous when the use of a surgical assistant or second surgeon was limited.

CONCLUSIONS

Robotic skull base neurosurgery has been growing in popularity and feasibility, but significant limitations remain. While robotic systems seem to have allowed for greater maneuverability and 3D visualization, their size and lack of neurosurgery-specific tools have continued to prevent widespread adoption into current practice. The next generation of robotic technologies should prioritize overcoming these limitations.

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David J. Cote, Jacob J. Ruzevick, Keiko M. Kang, Dhiraj J. Pangal, Ilaria Bove, John D. Carmichael, Mark S. Shiroishi, Ben A. Strickland, and Gabriel Zada

OBJECTIVE

The aim of this study was to evaluate the association between zip code–level socioeconomic status (SES) and presenting characteristics and short-term clinical outcomes in patients with nonfunctioning pituitary adenoma (NFPA).

METHODS

A retrospective review of prospectively collected data from the University of Southern California Pituitary Center was conducted to identify all patients undergoing surgery for pituitary adenoma (PA) from 2000 to 2021 and included all patients with NFPA with recorded zip codes at the time of surgery. A normalized socioeconomic metric by zip code was then constructed using data from the American Community Survey estimates, which was categorized into tertiles. Multiple imputation was used for missing data, and multivariable linear and logistic regression models were constructed to estimate mean differences and multivariable-adjusted odds ratios for the association between zip code–level SES and presenting characteristics and outcomes.

RESULTS

A total of 637 patients were included in the overall analysis. Compared with patients in the lowest SES tertile, those in the highest tertile were more likely to be treated at a private (rather than safety net) hospital, and were less likely to present with headache, vision loss, and apoplexy. After multivariable adjustment for age, sex, and prior surgery, SES in the highest compared with lowest tertile was inversely associated with tumor size at diagnosis (−4.9 mm, 95% CI −7.2 to −2.6 mm, p < 0.001) and was positively associated with incidental diagnosis (multivariable-adjusted OR 1.72, 95% CI 1.02–2.91). Adjustment for hospital (private vs safety net) attenuated the observed associations, but disparities by SES remained statistically significant for tumor size. Despite substantial differences at presentation, there were no significant differences in length of stay or odds of an uncomplicated procedure by zip code–level SES. Patients from lower-SES zip codes were more likely to require postoperative steroid replacement and less likely to achieve gross-total resection.

CONCLUSIONS

In this series, lower zip code–level SES was associated with more severe disease at the time of diagnosis for NFPA patients, including larger tumor size and lower rates of incidental diagnosis. Despite these differences at presentation, no significant differences were observed in short-term postoperative complications, although patients with higher zip code–level SES had higher rates of gross-total resection.

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Dhiraj J. Pangal, Guillaume Kugener, Tyler Cardinal, Elizabeth Lechtholz-Zey, Casey Collet, Sasha Lasky, Shivani Sundaram, Yichao Zhu, Arman Roshannai, Justin Chan, Aditya Sinha, Andrew J. Hung, Animashree Anandkumar, Gabriel Zada, and Daniel A. Donoho

OBJECTIVE

Experts can assess surgeon skill using surgical video, but a limited number of expert surgeons are available. Automated performance metrics (APMs) are a promising alternative but have not been created from operative videos in neurosurgery to date. The authors aimed to evaluate whether video-based APMs can predict task success and blood loss during endonasal endoscopic surgery in a validated cadaveric simulator of vascular injury of the internal carotid artery.

METHODS

Videos of cadaveric simulation trials by 73 neurosurgeons and otorhinolaryngologists were analyzed and manually annotated with bounding boxes to identify the surgical instruments in the frame. APMs in five domains were defined—instrument usage, time-to-phase, instrument disappearance, instrument movement, and instrument interactions—on the basis of expert analysis and task-specific surgical progressions. Bounding-box data of instrument position were then used to generate APMs for each trial. Multivariate linear regression was used to test for the associations between APMs and blood loss and task success (hemorrhage control in less than 5 minutes). The APMs of 93 successful trials were compared with the APMs of 49 unsuccessful trials.

RESULTS

In total, 29,151 frames of surgical video were annotated. Successful simulation trials had superior APMs in each domain, including proportionately more time spent with the key instruments in view (p < 0.001) and less time without hemorrhage control (p = 0.002). APMs in all domains improved in subsequent trials after the participants received personalized expert instruction. Attending surgeons had superior instrument usage, time-to-phase, and instrument disappearance metrics compared with resident surgeons (p < 0.01). APMs predicted surgeon performance better than surgeon training level or prior experience. A regression model that included APMs predicted blood loss with an R2 value of 0.87 (p < 0.001).

CONCLUSIONS

Video-based APMs were superior predictors of simulation trial success and blood loss than surgeon characteristics such as case volume and attending status. Surgeon educators can use APMs to assess competency, quantify performance, and provide actionable, structured feedback in order to improve patient outcomes. Validation of APMs provides a benchmark for further development of fully automated video assessment pipelines that utilize machine learning and computer vision.

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Justin Chan, Dhiraj J. Pangal, Tyler Cardinal, Guillaume Kugener, Yichao Zhu, Arman Roshannai, Nicholas Markarian, Aditya Sinha, Anima Anandkumar, Andrew Hung, Gabriel Zada, and Daniel A. Donoho

OBJECTIVE

Virtual reality (VR) and augmented reality (AR) systems are increasingly available to neurosurgeons. These systems may provide opportunities for technical rehearsal and assessments of surgeon performance. The assessment of neurosurgeon skill in VR and AR environments and the validity of VR and AR feedback has not been systematically reviewed.

METHODS

A systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted through MEDLINE and PubMed. Studies published in English between January 1990 and February 2021 describing the use of VR or AR to quantify surgical technical performance of neurosurgeons without the use of human raters were included. The types and categories of automated performance metrics (APMs) from each of these studies were recorded.

RESULTS

Thirty-three VR studies were included in the review; no AR studies met inclusion criteria. VR APMs were categorized as either distance to target, force, kinematics, time, blood loss, or volume of resection. Distance and time were the most well-studied APM domains, although all domains were effective at differentiating surgeon experience levels. Distance was successfully used to track improvements with practice. Examining volume of resection demonstrated that attending surgeons removed less simulated tumor but preserved more normal tissue than trainees. More recently, APMs have been used in machine learning algorithms to predict level of training with a high degree of accuracy. Key limitations to enhanced-reality systems include limited AR usage for automated surgical assessment and lack of external and longitudinal validation of VR systems.

CONCLUSIONS

VR has been used to assess surgeon performance across a wide spectrum of domains. The VR environment can be used to quantify surgeon performance, assess surgeon proficiency, and track training progression. AR systems have not yet been used to provide metrics for surgeon performance assessment despite potential for intraoperative integration. VR-based APMs may be especially useful for metrics that are difficult to assess intraoperatively, including blood loss and extent of resection.

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Janelle Cyprich, Dhiraj J. Pangal, Martin Rutkowski, Daniel A. Donoho, Mark Shiroishi, Chia-Shang Jason Liu, John D. Carmichael, and Gabriel Zada

OBJECTIVE

Sociodemographic disparities in health outcomes are well documented, but the effects of such disparities on preoperative presentation of pituitary adenomas (PA) and surgical outcomes following resection are not completely understood. In this study the authors sought to compare the preoperative clinical characteristics and postoperative outcomes in patients undergoing PA resection at a private hospital (PH) versus a safety-net hospital (SNH).

METHODS

The authors conducted a retrospective review over a 36-month period of patients with PAs who underwent endoscopic endonasal transsphenoidal surgery performed by the same attending neurosurgeon at either a PH or an SNH at a single academic medical institution.

RESULTS

A total of 92 PH patients and 69 SNH patients were included. SNH patients were more likely to be uninsured or have Medicaid (88.4% vs 10.9%, p < 0.0001). A larger percentage of SNH patients were Hispanic (98.7% vs 32.6% p < 0.0001), while PH patients were more likely to be non-Hispanic white (39.1% vs 4.3%, p < 0.0001). SNH patients had a larger mean PA diameter (26.2 vs 22.4 mm, p = 0.0347) and a higher rate of bilateral cavernous sinus invasion (13% vs 4.3%, p = 0.0451). SNH patients were more likely to present with headache (68.1% vs 45.7%, p = 0.0048), vision loss (63.8% vs 35.9%, p < 0.0005), panhypopituitarism (18.8% vs 4.3%, p = 0.0031), and pituitary apoplexy (18.8% vs 7.6%, p = 0.0334). Compared to PH patients, SNH patients were as likely to undergo gross-total resection (73.9% vs 76.1%, p = 0.7499) and had similar rates of postoperative improvement in headache (80% vs 89%, p = 0.14) and vision (82% vs 84%, p = 0.74), but had higher rates of postoperative panhypopituitarism (23% vs 10%, p = 0.04) driven by preoperative endocrinopathies. Although there were no differences in tumor recurrence or progression, loss to follow-up was seen in 7.6% of PH versus 18.6% (p = 0.04) of SNH patients.

CONCLUSIONS

Patients presenting to the SNH were more often uninsured or on Medicaid and presented with larger, more advanced pituitary tumors. SNH patients were more likely to present with headaches, vision loss, and apoplexy, likely translating to greater improvements in headache and vision observed after surgery. These findings highlight the association between medically underserved populations and more advanced disease states at presentation, and underscore the likely role of academic tertiary multidisciplinary care teams and endoscopic PA resection in somewhat mitigating sociodemographic factors known to portend poorer outcomes, though longer-term follow-up is needed to confirm these findings.

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Daniel A. Donoho, Dhiraj J. Pangal, Guillaume Kugener, Martin Rutkowski, Alexander Micko, Shane Shahrestani, Andrew Brunswick, Michael Minneti, Bozena B. Wrobel, and Gabriel Zada

OBJECTIVE

Internal carotid artery injury (ICAI) is a rare, life-threatening complication of endoscopic endonasal approaches that will be encountered by most skull base neurosurgeons and otolaryngologists. Rates of surgical proficiency for managing ICAI are not known, and the role of simulation to improve performance has not been studied on a nationwide scale.

METHODS

Attending and resident neurosurgery and otorhinolaryngology surgeons (n = 177) were recruited from multicenter regional and national training courses to assess training outcomes and validity at scale of a prospective educational intervention to improve surgeon technical skills using a previously validated, perfused human cadaveric simulator. Participants attempted an initial trial (T1) of simulated ICAI control using their preferred technique. An educational intervention including personalized instruction was performed. Participants attempted a second trial (T2). Task success (dichotomous), time to hemostasis (TTH), estimated blood loss (EBL), and surgeon heart rate were measured.

RESULTS

Participant rating scales confirmed that the simulation retained face and construct validity across eight instructional settings. Trial success (ICAI control) improved from 56% in T1 to 90% in T2 (p < 0.0001). EBL and TTH decreased by 37% and 38%, respectively (p < 0.0001). Postintervention resident surgeon performance (TTH, EBL, and success rate) was superior to preintervention attending surgeon performance. The most improved quartile of participants achieved 62% improvement in TTH and 73% improvement in EBL, with trial success improvement from 25.6% in T1 to 100% in T2 (p < 0.0001). Baseline surgeon confidence was uncorrelated with T1 success, while posttraining confidence correlated with T2 success. Tachycardia was measured in 57% of surgeon participants, but was attenuated during T2, consistent with development of resiliency.

CONCLUSIONS

Prior to training, many attending and most resident surgeons could not manage the rare, life-threatening intraoperative complication of ICAI. A simulated educational intervention significantly improved surgeon performance and remained valid when deployed at scale. Simulation also promoted the development of favorable cognitive skills (accurate perception of skill and resiliency). Rare, life-threatening intraoperative complications may be optimal targets for educational interventions using surgical simulation.

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Georgios Mantziaris, Stylianos Pikis, Tomas Chytka, Roman Liščák, Kimball Sheehan, Darrah Sheehan, Selcuk Peker, Yavuz Samanci, Shray K. Bindal, Ajay Niranjan, L. Dade Lunsford, Rupinder Kaur, Renu Madan, Manjul Tripathi, Dhiraj J. Pangal, Ben A. Strickland, Gabriel Zada, Anne-Marie Langlois, David Mathieu, Ronald E. Warnick, Samir Patel, Zayda Minier, Herwin Speckter, Zhiyuan Xu, Rithika Kormath Anand, and Jason P. Sheehan

OBJECTIVE

Radiological progression occurs in 50%–60% of residual nonfunctioning pituitary adenomas (NFPAs). Stereotactic radiosurgery (SRS) is a safe and effective management option for residual NFPAs, but there is no consensus on its optimal timing. This study aims to define the optimal timing of SRS for residual NFPAs.

METHODS

This retrospective, multicenter study involved 375 patients with residual NFPAs managed with SRS. The patients were divided into adjuvant (ADJ; treated for stable residual NFPA within 6 months of resection) and progression (PRG) cohorts (treated for residual NFPA progression). Factors associated with tumor progression and clinical deterioration were analyzed.

RESULTS

Following propensity-score matching, each cohort consisted of 130 patients. At last follow-up, tumor control was achieved in 93.1% of patients in the ADJ cohort and in 96.2% of patients in the PRG cohort (HR 1.6, 95% CI 0.55–4.9, p = 0.37). Hypopituitarism was associated with a maximum point dose of > 8 Gy to the pituitary stalk (HR 4.5, 95% CI 1.6–12.6, p = 0.004). No statistically significant difference was noted in crude new-onset hypopituitarism rates (risk difference [RD] = −0.8%, p > 0.99) or visual deficits (RD = −2.3%, p = 0.21) between the two cohorts at the last follow-up. The median time from resection to new hypopituitarism was longer in the PRG cohort (58.9 vs 29.7 months, p = 0.01).

CONCLUSIONS

SRS at residual NFPA progression does not appear to alter the probability of tumor control or hormonal/visual deficits compared with adjuvant SRS. Deferral of radiosurgical management to the time of radiological progression could significantly prolong the time to radiosurgically induced pituitary dysfunction. A lower maximum point dose (< 8 Gy) to the pituitary stalk portended a more favorable chance of preserving pituitary function after SRS.