Translating the simulation of procedural drilling techniques for interactive neurosurgical training

Pituitary surgery in Cushing's disease: first line treatment and role of reoperation

Cushing's disease is the most common cause of endogenous hypercortisolemia, and transsphenoidal surgery remains the first line therapy for removal of the ACTH-secreting adenoma. While post-operative remission rates are high in experienced hands, there remains a 2% risk of recurrence per year. Patients with the highest chance for cure are those with small, non-invasive tumors that are visible on pre-operative MRI and identified during surgery and are performed by high-volume pituitary neurosurgeons. Surgery for persistent or recurrent disease is frequently indicated and is most successful in the hands of experienced surgeons and in cases where tumor is visible on MRI.

Presurgical simulation for neuroendoscopic procedures: Virtual study of the integrity of neurological pathways using diffusion tensor imaging tractography

Background:

White matter (WM) transgression is an unexplored concept in neuroendoscopy. Diffusion tensor image (DTI) tractography could be implemented as a planning and postoperative evaluation tool in functional disconnection procedures (FDPs), which are, currently, the subject of technological innovations. We intend to prove the usefulness of this planning method focused on the assessment of WM injury that is suitable for planning FDPs.

Methods:

Ten cranial magnetic resonance studies (20 sides) without pathological findings were processed. Fascicles were defined by two regions of interest (ROIs) using the fiber assignment method by the continuous tracking approach. Using three-dimensional (3D) simulation and DTI tractography, we created an 8-mm virtual endoscope and an uninjured inferior fronto-occipital fasciculus (IFOF) from two ROIs. The injured tract was generated using a third ROI built from the 3D model of the intersection of the oriented trajectory of the endoscope with the fascicle. Data and images were quantitatively and qualitatively analyzed.

Results:

The average percentage of the injured fibers was 32.0% (range: 12.4%–70%). The average intersected volume was 1.1 cm³ (range: 0.3–2.3 cm³). Qualitative analysis showed the inferior medial quadrant of the inferior fronto-occipital fasciculus (IFOF) as the most frequently injured region. No hemispherical asymmetry was found (P > 0.5).

Conclusion:

DTI tractography is a useful surgical planning tool that could be implemented in several endoscopic procedures. Together with a functional atlas, the presented technique provides a noninvasive method to assess the potential sequelae and thus to optimize the surgical route. The suggested method could be implemented to analyze pathological WM fascicles and to assess the surgical results of FDP such as hemispherotomy or amygdalohippocampectomy. More studies are needed to overcome the limitations of the tractography based information and to develop more anatomically and functionally reliable planning systems.

Technique for Latex Injection and Reuse of Human Heads Preserved in Formaldehyde

Background  Understanding the anatomy of the skull base is paramount for every skull base surgeon, particularly in light of the expanded endoscopic endonasal approaches, and of the refined surgical technique used in both medial and lateral approaches. A comprehensive knowledge of anatomy is the cornerstone for a safe surgery, maximizing resection and minimizing complications. The best study method is the careful dissection of fresh human cadaveric heads in a well-equipped anatomy laboratory. In this study, we describe our protocol for preparing cadaveric specimens without vascular injection, which had been preserved in a formaldehyde solution after treating them with a dimethyldioctadecylammonium chloride/distearyl dimethyl ammonium chloride solution (commercial fabric softener) and injecting the vascular system with latex. Method  Six cadaveric specimens underwent our treatment and subsequent injection of the vascular system and dissection. Results  All specimens showed a good penetration of the latex and a clear improvement of the malleability of the tissues was noticed. The authors agree that this technique improved the quality of the head and facilitated studying. Conclusion  We consider this an effective treatment with latex, reaching small caliber vessels, and a greater malleability and flexibility of tissues, allowing better dissections, and greater anatomical exposure, making them suitable for skull base training, study, and research.

Simulation training in neurosurgery: advances in education and practice

The current simulation technology used for neurosurgical training leaves much to be desired. Significant efforts are thoroughly exhausted in hopes of developing simulations that translate to give learners the "real-life" feel. Though a respectable goal, this may not be necessary as the application for simulation in neurosurgical training may be most useful in early learners. The ultimate uniformly agreeable endpoint of improved outcome and patient safety drives these investments. We explore the development, availability, educational taskforces, cost burdens and the simulation advancements in neurosurgical training. The technologies can be directed at achieving early resident milestones placed by the Accreditation Council for Graduate Medical Education. We discuss various aspects of neurosurgery disciplines with specific technologic advances of simulation software. An overview of the scholarly landscape of the recent publications in the realm of medical simulation and virtual reality pertaining to neurologic surgery is provided. We analyze concurrent concept overlap between PubMed headings and provide a graphical overview of the associations between these terms.

Assessment of White Matter Transgression During Neuroendoscopic Procedures Using Diffusion Tensor Image Fiber Tracking

BACKGROUND

Presurgical planning allows anticipating intraoperative difficulties, increasing efficiency, and reducing risks. Neuroendoscopy is a minimally invasive technique whose related complications have been focused on cortical function and surface vessels injury. However, white matter disruption has been insufficiently acknowledged.

OBJECTIVE

To present a new surgical planning method based on diffusion tensor image that allows quantifying subcortical transgression and optimizing neuroendoscopic trajectories.

METHODS

Ten cranial magnetic resonance studies (20 sides) without pathologic findings were anonymized and processed. A standard transcortical approach to the frontal horn was used to study the transgression of the corpus callosum (CC) and cingulum (Ci) caused by a virtual endoscope (VE) oriented from the Kocher point to the foramen of Monro. An 8-mm VE model was created, oriented, and coregistered. VE-CC and VE-Ci intersections were segmented. The number and volume of injured fibers were measured, intersections were quantified, and the percentage of tract transgression was calculated. The areas damaged by the VE were also recorded.

RESULTS

Among the CC fibers, 16.4% were injured (range: 3.3%-37%) and 26.7% of fibers on Ci (rank: 0%-73.4%). The average intersected volumes were 19.1% (range: 4.2%-53.2%) for CC and 33.2% for Ci (range: 0%-73.7%). Qualitative analysis showed the lateral aspect of both tracts as the most frequently injured region. No hemispherical asymmetry was found (P > 0.05).

CONCLUSION

This method using tractography and oriented models of surgical instruments allows assessing white matter transgression, both qualitatively and quantitatively, for a deep brain trajectory. Thus our method permits surgeons to optimize safety and avoid transgression of eloquent tracts during surgical planning. Nevertheless, more studies are necessary.

Supplementary Educational Models in Canadian Neurosurgery Residency Programs

Background: The proposed implementation of work hour restrictions has presented a significant challenge of maintaining the quality of resident education and ensuring adequate hands-on experience that is essential for novice surgeons. To maintain the level of resident surgical competency, revision of the apprentice model of surgical education to include supplementary educational methods, such as laboratory and virtual reality (VR) simulations, have become frequent topics of discussion. We aimed to better understand the role of supplementary educational methods in Canadian neurosurgery residency training. Methods: An online survey was sent to program directors of all 14 Canadian neurosurgical residency programs and active resident members of the Canadian Neurosurgical Society (N=85). We asked 16 questions focusing on topics of surgeon perception, current implementation and barriers to supplementary educational models. Results: Of the 99 surveys sent, 8 out of 14 (57%) program directors and 37 out of 85 (44%) residents completed the survey. Of the 14 neurosurgery residency programs across Canada, 7 reported utilizing laboratory-based teaching within their educational plan, while only 3 programs reported using VR simulation as a supplementary teaching method. The biggest barriers to implementing supplementary educational methods were resident availability, lack of resources, and cost. Conclusions: Work-hour restrictions threaten to compromise the traditional apprentice model of surgical training. The potential value of supplementary educational methods for surgical education is evident, as reported by both program directors and residents across Canada. However, availability and utilization of laboratory and VR simulations are limited by numerous factors such as time constrains and lack of resources.

Simulator-Based Angiography and Endovascular Neurosurgery Curriculum: A Longitudinal Evaluation of Performance Following Simulator-Based Angiography Training

This study establishes performance metrics for angiography and neuroendovascular surgery procedures based on longitudinal improvement in individual trainees with differing levels of training and experience.

Over the course of 30 days, five trainees performed 10 diagnostic angiograms, coiled 10 carotid terminus aneurysms in the setting of subarachnoid hemorrhage, and performed 10 left middle cerebral artery embolectomies on a Simbionix Angio Mentor™ simulator. All procedures were nonconsecutive. Total procedure time, fluoroscopy time, contrast dose, heart rate, blood pressures, medications administered, packing densities, the number of coils used, and the number of stent-retriever passes were recorded. Image quality was rated, and the absolute value of technically unsafe events was recorded. The trainees’ device selection, macrovascular access, microvascular access, clinical management, and the overall performance of the trainee was rated during each procedure based on a traditional Likert scale score of 1=fail, 2=poor, 3=satisfactory, 4=good, and 5=excellent. These ordinal values correspond with published assessment scales on surgical technique.

After performing five diagnostic angiograms and five embolectomies, all participants demonstrated marked decreases in procedure time, fluoroscopy doses, contrast doses, and adverse technical events; marked improvements in image quality, device selection, access scores, and overall technical performance were additionally observed (p < 0.05). Similarly, trainees demonstrated marked improvement in technical performance and clinical management after five coiling procedures (p < 0.05). However, trainees with less prior experience deploying coils continued to experience intra-procedural ruptures up to the eighth embolization procedure; this observation likely corresponded with less tactile procedural experience to an exertion of greater force than appropriate for coil placement.

Trainees across all levels of training and prior experience demonstrated a significant performance improvement after completion of our simulator curriculum consisting of five diagnostic angiograms, five embolectomy cases, and 10 aneurysm coil embolizations.

A physical simulator for endoscopic endonasal drilling techniques: technical note

In this paper, the authors present a physical model developed to teach surgeons the requisite drilling techniques when using an endoscopic endonasal approach (EEA) to the skull base. EEA is increasingly used for treating pathologies of the ventral and ventrolateral cranial base. Endonasal drilling is a unique skill in terms of the instruments used, the long reach required, and the restricted angulation, and gaining competency requires much practice. Based on the successful experience in creating custom simulators, the authors used 3D printing to build an EEA training model from post-processed thin-cut head CT scans, formulating the materials to provide realistic haptic feedback and endoscope handling. They performed a preliminary assessment at 2 institutions to evaluate content validity of the simulator as the first step of the validation process. Overall results were positive, particularly in terms of bony landmarks and haptic response, though minor refinements were suggested prior to use as a training device.

Comparative study on surface reconstruction accuracy of stereo imaging devices for microsurgery

PURPOSE

Processing stereoscopic image data is an emerging field. Especially in microsurgery that requires sub-millimeter accuracy, application of stereo-based methods on endoscopic and microscopic scenarios is of major interest. In this context, direct comparison of stereo-based surface reconstruction applied to several camera settings is presented.

METHODS

A method for stereo matching is proposed and validated on in-vitro data. Demonstrating suitability for surgical scenarios, this method is applied to two custom-made stereo cameras, a miniaturized, bendable surgical endoscope and an operating microscope. Reconstruction accuracy is assessed on a custom-made reference sample. Subsequent to its fabrication, a coordinate measuring arm is used to acquire ground truth. Next, the sample is positioned by a robot at varying distances to each camera. Surface estimation is performed, while the specimen is localized based on. markers. Finally, the error between estimated surface and ground truth is computed.

RESULTS

Sample measurement with the coordinate measuring arm yields reliable ground truth data with a root-mean-square error of 11.2 μm. Overall surface reconstruction with analyzed cameras is quantified by a root-mean-square error of less than 0.18 mm. Microscope setting with the highest magnification yields the most accurate measurement, while the maximum deviation does not exceed 0.5 mm. Custom-made stereo cameras perform similar but with outliers of increased magnitude. Miniaturized, bendable surgical endoscope produces the maximum error of approximately 1.2 mm.

CONCLUSIONS

Reconstruction results reveal that microscopic imaging outperforms investigated chip-on-the-tip solutions, i.e., at higher magnification. Nonetheless, custom-made cameras are suitable for application in microsurgery. Although reconstruction with the miniaturized endoscope is more inaccurate, it provides a good trade-off between accuracy, outer dimensions and accessibility to hard-to-reach surgical sites.

Simulation Training Curricula for Neurosurgical Residents: Cervical Foraminotomy and Durotomy Repair Modules

INTRODUCTION

Since 2010, the Congress of Neurological Surgeons (CNS) has offered a neurosurgical skills simulation course for residents and medical students. The authors describe their experience with incorporation of two neurosurgical skills simulation modules into the dedicated resident training curriculum of a single ACGME-accredited training program, using lumbar dural repair (5) and posterior cervical laminoforaminotomy modules from the CNS simulation initiative (6).

METHODS

Each of the available 22 neurosurgery residents at a single residency program was given two 20-question pretests for a cervical laminoforaminotomy and durotomy repair module as a basic test of regional anatomy, general disease knowledge, surgical decision making, and recently published literature. This was followed by a faculty-directed skills simulation course and concluded with a final 20 question post-test.

RESULTS

Posterior cervical laminoforaminotomy was performed once by each resident, and grading was conducted using the predetermined OSATs. The overall score was 56.1 (70%, range 26-76, maximum 80 points) with a trend towards higher scores with advanced levels of training. All residents completed the durotomy repair OSATs for a total of three trials. Of a maximum composite score of 60, a mean 37.2 (62%, range 15-58) was scored by the residents (Table 3). The mean OSAT scores for each durotomy trial was 2.66, 3.15, and 3.48 on each success test. A trend towards higher scores in advanced years of training was observed, but did not reach statistical significance (Figure 3).

CONCLUSIONS

Duty hour limitations and regulatory pressure for enhanced quality and outcomes may limit access of neurosurgical residents to fundamental skills training. Fundamental skills training as part of a validated simulation curriculum can mitigate this challenge to residency education. National development of effective technical simulation modules for use in individual residency training programs is a promising strategy to achieve these goals.