Skull base tumor model

Training models and simulators for endoscopic transsphenoidal surgery: a systematic review

Endoscopic transsphenoidal surgery is a novel surgical technique requiring specific training. Different models and simulators have been recently suggested for it, but no systematic review is available. To provide a systematic and critical literature review and up-to-date description of the training models or simulators dedicated to endoscopic transsphenoidal surgery. A search was performed on PubMed and Scopus databases for articles published until February 2023; Google was also searched to document commercially available. For each model, the following features were recorded: training performed, tumor/arachnoid reproduction, assessment and validation, and cost. Of the 1199 retrieved articles, 101 were included in the final analysis. The described models can be subdivided into 5 major categories: (1) enhanced cadaveric heads; (2) animal models; (3) training artificial solutions, with increasing complexity (from "box-trainers" to multi-material, ct-based models); (4) training simulators, based on virtual or augmented reality; (5) Pre-operative planning models and simulators. Each available training model has specific advantages and limitations. Costs are high for cadaver-based solutions and vary significantly for the other solutions. Cheaper solutions seem useful only for the first stages of training. Most models do not provide a simulation of the sellar tumor, and a realistic simulation of the suprasellar arachnoid. Most artificial models do not provide a realistic and cost-efficient simulation of the most delicate and relatively common phase of surgery, i.e., tumor removal with arachnoid preservation; current research should optimize this to train future neurosurgical generations efficiently and safely.

Simulation training in endoscopic skull base surgery: A scoping review

Objective

Proficiency in endoscopic endonasal skull base surgery requires both substantial baseline training and progressive lifelong learning. Endoscopic simulation models continue to evolve in an effort to optimize trainee education and preoperative preparation and improve surgical outcomes. The current scoping review systematically reviews all available literature and synthesizes the current paradigms of simulation models for endoscopic skull base surgery training and skill enhancement.

Methods

In accordance with Preferred Reporting Items for Systemic Review and Meta-Analyses guidelines, we systematically searched PubMed, Embase, CINAHL, and Cochrane databases. Studies were categorized according to the type of simulation models investigated.

Results

We identified 238 unique references, with 55 studies ultimately meeting inclusion criteria. Of these, 19 studies described cadaveric dissection models, 17 discussed three-dimensional (3D) printed models, 14 examined virtual surgical planning and augmented reality-based models, and five 5 articles described task trainers.

Conclusions

There are a wide variety of simulation models for endoscopic skull base surgery, including high-fidelity cadaveric, virtual reality, and 3D-printed models. These models are an asset for trainee development and preoperative surgical preparation.

Human Cadaveric Artificial Lung Tumor-Mimic Training Model

Introduction: An important phase in surgical training is gaining experience in real human anatomical situations. When a cadaver is available it may complement the various artificial practice models. However, it is often necessary to supplement the characteristics of the cadavers with a simulation of a tumor. Our objective was to develop an easy-to-create, realistic artificial tumor-mimic model for peripheral lung tumor resection practice.

Methods: In our work we injected barium sulphate enriched silicone suspension into 10 isolated, non-fixed lungs of human cadavers, through the puncture of the visceral pleura. Four lesions–apical, hilar and two peripheral–were created in each of ten specimens. After fixation CT scans were obtained and analyzed. The implanted tumor-mimics were examined after anatomical preparation and slicing. Also performed CT-guided percutaneous puncture was also performed to create the lesions in situ in two lungs of human cadavers.

Results: Analyzing the CT data of 10 isolated lungs, out of 40 lesions, 34 were nodular (85.0%) and in the nodular group five were spiculated (12.5%). Satellite lesions were formed in two cases (5.0%). Relevant outflow into vessels or airway occurred in five lesions (12.5%). Reaching the surface of the lung occured in 11 lesions (27.5%). The tumor-mimics were elastic and adhered well to the surrounding tissue. The two lesions, implanted via percutaneous puncture, both were nodular and one also showed lobulated features.

Conclusion: Our artificial tumor-mimics were easy to create, varied in shape and size, and with percutaneous implantation the lesions provide a model for teaching every step of a surgical procedure.

Interoptic, Trans-lamina Terminalis, Opticocarotid Triangle, and Caroticosylvian Windows From Mini-Supraorbital, Frontomedial, and Pterional Perspectives: A Comparative Cadaver Study With Artificial Lesions

Introduction: The mini-supraorbital (MSO) and pterional (PT) approaches have been compared in a number of studies focusing on the treatment of aneurysms, craniopharyngiomas, and meningiomas. The goal of this study was to analyze the surgical exposure to different artificial lesions through interoptic (IO), trans-lamina terminalis (TLT), opticocarotid triangle (OCT), and caroticosylvian (CS) windows from the MSO, frontomedial (FM), and PT perspectives. Methods: The MSO, PT, and FM approaches were performed sequentially in two fixed cadaver heads. Three colored spheres were placed around the optic chiasm: (1) between the optic nerves; (2) between the optic nerve and the internal carotid artery; and (3) between the internal carotid artery and the oculomotor nerve. The surgical exposures to these structures by using the IO, TLT, OCT, and CS windows were compared. Results: (1) IO window: from the MSO and PT approaches, the total surgical exposure mainly allows visualization of contralateral lesions. The FM approach was superior for exploration of both sides of the area between the optic nerves. (2) TLT pathway: the MSO and PT approaches mainly expose the contralateral third ventricle wall. (3) OCT window: the PT approach allows exposure of a larger part of the sphere between the optic nerve and the internal carotid artery than the MSO approach. (4) CS window: the PT approach allows a better exposure of lateral structures such as the oculomotor nerve and of the medial prepontine area in comparison to the MSO approach. Conclusion: Simulation of the surgical situation with artificial lesions is a good model for comparing surgical perspectives and for analyzing feasibility of lesion exposure and resection.

Simulation Training Methods in Neurological Surgery

Simulation training plays a paramount role in medicine, especially when it comes to mastering surgical skills. By simulating, students gain not only confidence, but expertise, learning to apply theory in a safe environment. As the technological arsenal improved, virtual reality and physical simulators have developed and are now an important part of the Neurosurgery training curriculum. Based on deliberate practice in a controlled space, simulation allows psychomotor skills augment without putting neither patients nor students at risk. When compared to the master-apprentice ongoing model of teaching, simutation becomes even more appealing as it is time-efficient, shortening the learning curve and ultimately leading to error reduction, which is reflected by diminished health care costs in the long run. In this chapter we will discuss the current state of neurosurgery simulation, highlight the potential benefits of this approach, assessing specific training methods and making considerations towards the future of neurosurgical simulation.

Skull Base Neuroendoscopic Training Model Using a Fibrous Injectable Tumor Polymer and the Nico Myriad

The Myriad is an innovative, high precision tool for tumor resection, designed to work within narrow endoscopic corridors. Due to its application in technically demanding situations, the learning curve associated with its use might be extremely challenging and time-consuming.The authors describe the application of an already validated training model, the skull base injectable tumor model (ITM), to allow trainees to practice with the use of the Myriad during endoscopic skull base procedures.A formalin embalmed cadaveric head was used for technical assessment. Stratathane resin ST-504 derived polymer was injected to mimic skull base tumors and Myriad was used for tumor resection during different endoscopic procedures.An endoscopic endonasal transsphenoidal, a trans-planum trans-tuberculum, and a trans-clival approach have been performed after ITM injection. The Myriad was used for tumor debulking and blunt manipulation, qualitatively evaluating the technical challenges in performing the surgical dissection.Injectable tumor model demonstrates to be a valuable educational tool to train surgeons in the use of Myriad, potentially speeding up the learning curve in the acquirement of necessary technical skills in manipulating the instrument, even in case of demanding surgical situation.

Systematic review of surgical training on reperfused human cadavers

BACKGROUND

The role of reperfused human cadavers in surgical training has not been established.

METHODS

Reports describing reperfused human cadaver models in terms of simulated surgeries, the use of tools to assess technical competency and skills transfer to patients, cadaver status and reperfusion techniques were included.

RESULTS

Thirty-five reports were included. Most participants practised vascular (n = 27), flap (n = 6) and trauma (n = 4) procedures. Training progression was evaluated objectively in only two studies. In two publications, flap techniques were practised on cadavers and repeated successfully in patients. Eighteen studies employed whole bodies. Fresh and embalmed cadavers were both used in 17 publications. Most embalmed cadavers were formalin-fixed (n = 10), resulting in stiffness. Few trainings were offered on soft Thiel-embalmed cadavers (n = 5). Only arteries were reperfused in 20 studies, while in 13 publications, the arteries and veins were filled. Arteries and/or veins were mostly pressurized (n = 21) and arterial flow was generated in 14 studies.

CONCLUSIONS

Various reperfused human cadaver models exist, enabling practise of mainly vascular procedures. Preservation method determines the level of simulation fidelity. Thorough evaluation of these models as surgical training tools and transfer effectiveness is still lacking.

Quantitative evaluation of different far lateral approaches to the cranio-vertebral junction using the microscope and the endoscope: a cadaveric study using a tumor model

BACKGROUND

Several far lateral approaches have been proposed to deal with cranio-vertebral junction (CVJ) tumors including the basic, transcondylar, and supracondylar far lateral approaches (B-FLA, T-FLA, and S-FLA). However, the indications on when to use one versus the other are not well systematized yet. Our purpose is to evaluate in an experimental cadaveric setting which approach is best suited to remove tumors of different sizes.

METHODS

We implanted at the CVJ, using a transoral approach, tumor models of different sizes (five 1-cm³ and five 3-cm³ tumors) in ten embalmed cadaveric heads. The artificial tumors were exposed via the three approaches using endoscopic-assisted microneurosurgical technique and neuronavigation. The skull base area exposed and the maneuverability linked to each approach were evaluated using neuronavigation.

RESULTS

In 1-cm³ tumors, the T-FLA and the S-FLA exposed a significantly larger skull base area than the B-FLA both using the microscope and the endoscope (P < 0.05); the T-FLA executed with the microscope provided wider vertical and horizontal maneuverability than the B-FLA (P = 0.030 and 0.017, respectively); the S-FLA executed with the endoscope provided wider vertical maneuverability than the T-FLA (P = 0.031). The S-FLA executed using the microscope and the endoscope provided wider vertical maneuverability than the B-FLA both in 1 and 3-cm³ tumors (P < 0.05).

CONCLUSIONS

In 1-cm³ tumors, the S-FLA and the T-FLA expose a wider skull base area than the B-FLA. In larger tumors, the exposure is similar for all three approaches. Use of the endoscope in an assistive mode may further increase the surgical exposure and maneuverability.

A morphometric and analytical cadaver dissection study of a tumor-simulation balloon model

We quantified the effects on anatomical cadaver dissection of a balloon-inflation tumor model positioned in the parasellar region and approached through an orbitozygomatic (OZ) craniotomy. A modified supraorbital OZ was performed bilaterally on 5 silicon-injected cadaver heads. Ten predetermined anatomical points assigned using a frameless stereotactic device were used to measure the working area of exposure, degree of surgical freedom, and horizontal and vertical angles of attack to specific target points before and after inflation of a balloon catheter mimicking a parasellar tumor. Balloon inflation displaced the central anatomical structures (pituitary stalk, lamina terminalis, anterior chiasm, and internal carotid artery [ICA]-posterior communicating artery and ICA-A1 junctions) by 14-51% (p ≤ .05). With tumor simulation, the vertical angle of attack increased by 67% (p < .01), while the area of exposure increased by 83% (p < .01) and surgical freedom increased by 58% (p < .01). This tumor model also significantly displaced central anatomical sella-associated structures. Compared to a normal anatomical configuration, the tumor simulation (balloon) opened surgical corridors (especially vertical) and acted as a natural retractor, widening the angle of access to the infundibular apex-hypothalamic junction. Although this model cannot exactly mimic a tumor mass in a patient, the effects of tumor compression and sequential displacement of important structures can be combined into and then assessed in a cadaveric neurosurgical anatomical scenario for training and research.

Tumor model for surgical simulation to assess a minimally invasive endoscopic approach for midcheek mass removal

INTRODUCTION

The midcheek is considered one of the most important facial area due to its involvement in mimic expression and communication. Pathology of this district is complex due to the variety of soft tissue belonging to the face. We propose a surgical simulation, to assess the feasibility of a new minimally invasive endoscopic approach for midcheek mass removal.

TECHNICAL REPORT

This study was performed on four cadavers, at the Anatomy Laboratory of the University of Tubingen. In all the cadavers 3 cm³ of Acquasil Dent Sply Ultra were injected via trans-cutaneous along the nasolabial fold to simulate a midcheek mass. Three incisions in concealed areas were performed to create an access to reach the anterior compartment of the face. By using the Optical Dissector with distal spatula and a 30° endoscope we provided a wide surgical window and a greater exposure to isolate, dissect and remove the midcheek tumor model safely.

CONCLUSION

The proposed endoscopic technique allowed us to visualize and preserve all the key anatomic structures of the midcheek region. Due to its nature, the suggested material may provide a valid tumor model for surgical training also in other districts.

Lifelike Vascular Reperfusion of a Thiel-Embalmed Pig Model and Evaluation as a Surgical Training Tool

BACKGROUND

Vascular reperfusion of Thiel cadavers can aid surgical and anatomical instruction. This study investigated whether ideal embalming circumstances provide lifelike vascular flow, enabling surgical practice and enhancing anatomical reality.

METHODS

Pressure-controlled pump-driven administration of blue embalming solution was assessed directly postmortem in a pig model (n = 4). Investigation of subsequent pump-driven vascular injection of red paraffinum perliquidum (PP) included assessment of flow parameters, intracorporeal distribution, anatomical alterations, and feasibility for surgical training. The microscopic distribution of PP was analyzed in pump-embalmed pig and gravity-embalmed human small intestines.

RESULTS

Embalming lasted 50-105 min, and maximum arterial pressure was 65 mm Hg. During embalming, the following consecutive alterations were observed: arterial filling, organ coloration, venous perfusion, and further tissue coloration during the next weeks. Most organs were adequately preserved. PP generated low arterial pressures (<30 mm Hg) and drained through the venous cannula. Generally, realistic reperfusion and preservation of original anatomy were observed, but leakage in the pleural, abdominal, and retroperitoneal cavities occurred, and computed tomography showed edematous spleen and liver. Reduction of arterial flow rates after venous drainage is a prerequisite to prevent anatomical deformation, allowing simulation of various surgeries. In pump-embalmed pig small intestines, PP flowed from artery to vein through the capillaries without extravasation. In contrast, arterioles were blocked in gravity-embalmed human tissues.

CONCLUSIONS

In a pig model, immediate postmortem pressure-controlled pump embalming generates ideal circumstances for (micro)vascular reperfusion with PP, permitting lifelike anatomy instruction and surgical training.

Petroclival tumor model--technical note and educational implications

Petroclival area lesions are rare, and their surgery is challenging due to the deep location and to the complex relationships between the tumor and the neurovascular structures. The objective is to present a petroclival tumor model simulating the distorted anatomy of a real petroclival lesion and propose its use to practice microsurgical removal while preserving neurovascular structures. Four embalmed cadaver heads were used in this study. An endoscopic endonasal transclival approach was used to access the dura in front of the trigeminal nerve; a pediatric Foley was inserted above the trigeminal nerve and was gradually inflated (one-balloon technique). If a larger tumor model was desired, an additional balloon was placed below the trigeminal nerve (two-balloon technique). A pre-mixed tumor polymer was injected into the petroclival space and allowed to harden to create an implanted tumor. A post-implant CT scan was done to evaluate the location and volume of the implanted artificial tumor. Tumors were subsequently excised via retrosigmoid and anterior petrosal approaches. Six petroclival tumors were successfully developed: three were small (9.41-10.36 ml) and three large (21.05-23.99 ml). During dissection, distorted anatomy created by the tumor model mimicked that of real surgery. We have established a petroclival tumor model with adjustable size which offers opportunities to study the distorted anatomy of the area and that is able to be used as a training tool to practice microsurgical removal of petroclival lesions. The practice dissection of this tumor model can be a bridge between a normal anatomic dissection and real surgery.

Design and Validation of an Open-Source, Partial Task Trainer for Endonasal Neuro-Endoscopic Skills Development: Indian Experience

BACKGROUND

Box trainers are ideal simulators, given they are inexpensive, accessible, and use appropriate fidelity.

OBJECTIVE

The development and validation of an open-source, partial task simulator that teaches the fundamental skills necessary for endonasal skull-base neuro-endoscopic surgery.

METHODS

We defined the Neuro-Endo-Trainer (NET) SkullBase-Task-GraspPickPlace with an activity area by analyzing the computed tomography scans of 15 adult patients with sellar suprasellar parasellar tumors. Four groups of participants (Group E, n = 4: expert neuroendoscopists; Group N, n =19: novice neurosurgeons; Group R, n = 11: neurosurgery residents with multiple iterations; and Group T, n = 27: neurosurgery residents with single iteration) performed grasp, pick, and place tasks using NET and were graded on task completion time and skills assessment scale score.

RESULTS

Group E had lower task completion times and greater skills assessment scale scores than both Group N and R (P ≤ 0.03, 0.001). The performance of Groups N and R was found to be equivalent; in self-assessing neuro-endoscopic skill, the participants in these groups were found to have equally low pretraining scores (4/10) with significant improvement shown after NET simulation (6, 7 respectively). Angled scopes resulted in decreased scores with tilted plates compared with straight plates (30° P ≤ 0.04, 45° P ≤ 0.001). With tilted plates, decreased scores were observed when we compared the 0° with 45° endoscope (right, P ≤ 0.008; left, P ≤ 0.002).

CONCLUSIONS

The NET, a face and construct valid open-source partial task neuroendoscopic trainer, was designed. Presimulation novice neurosurgeons and neurosurgical residents were described as having insufficient skills and preparation to practice neuro-endoscopy. Plate tilt and endoscope angle were shown to be important factors in participant performance. The NET was found to be a useful partial-task trainer for skill building in neuro-endoscopy.

"Live cadavers" for training in the management of intraoperative aneurysmal rupture

OBJECT

Intraoperative rupture occurs in approximately 9.2% of all cranial aneurysm surgeries. This event is not merely a surgical complication, it is also a real surgical crisis that requires swift and decisive action. Neurosurgical residents may have little exposure to this event, but they may face it in their practice. Laboratory training would be invaluable for developing competency in addressing this crisis. In this study, the authors present the "live cadaver" model, which allows repetitive training under lifelike conditions for residents and other trainees to practice managing this crisis.

METHODS

The authors have used the live cadaver model in 13 training courses from 2009 to 2014 to train residents and neurosurgeons in the management of intraoperative aneurysmal rupture. Twenty-three cadaveric head specimens harboring 57 artificial and 2 real aneurysms were used in these courses. Specimens were specially prepared for this technique and connected to a pump that sent artificial blood into the vessels. This setting created a lifelike situation in the cadaver that simulates live surgery in terms of bleeding, pulsation, and softness of tissue.

RESULTS

A total of 203 neurosurgical residents and 89 neurosurgeons and faculty members have practiced and experienced the live cadaver model. Clipping of the aneurysm and management of an intraoperative rupture was first demonstrated by an instructor. Then, trainees worked for 20- to 30-minute sessions each, during which they practiced clipping and reconstruction techniques and managed intraoperative ruptures. Ninety-one of the participants (27 faculty members and 64 participants) completed a questionnaire to rate their personal experience with the model. Most either agreed or strongly agreed that the model was a valid simulation of the conditions of live surgery on cerebral aneurysms and represents a realistic simulation of aneurysmal clipping and intraoperative rupture. Actual performance improvement with this model will require detailed measurement for validating its effectiveness. The model lends itself to evaluation using precise performance measurements.

CONCLUSIONS

The live cadaver model presents a useful simulation of the conditions of live surgery for clipping cerebral aneurysms and managing intraoperative rupture. This model provides a means of practice and promotes team management of intraoperative cerebrovascular critical events. Precise metric measurement for evaluation of training performance improvement can be applied.

The use of simulation in neurosurgical education and training

Object

There is increasing evidence that simulation provides high-quality, time-effective training in an era of resident duty-hour restrictions. Simulation may also permit trainees to acquire key skills in a safe environment, important in a specialty such as neurosurgery, where technical error can result in devastating consequences. The authors systematically reviewed the application of simulation within neurosurgical training and explored the state of the art in simulation within this specialty. To their knowledge this is the first systematic review published on this topic to date.

Methods

The authors searched the Ovid MEDLINE, Embase, and PsycINFO databases and identified 4101 articles; 195 abstracts were screened by 2 authors for inclusion. The authors reviewed data on study population, study design and setting, outcome measures, key findings, and limitations.

Results

Twenty-eight articles formed the basis of this systematic review. Several different simulators are at the neurosurgeon's disposal, including those for ventriculostomy, neuroendoscopic procedures, and spinal surgery, with evidence for improved performance in a range of procedures. Feedback from participants has generally been favorable. However, study quality was found to be poor overall, with many studies hampered by nonrandomized design, presenting normal rather than abnormal anatomy, lack of control groups and long-term follow-up, poor study reporting, lack of evidence of improved simulator performance translating into clinical benefit, and poor reliability and validity evidence. The mean Medical Education Research Study Quality Instrument score of included studies was 9.21 ± 1.95 (± SD) out of a possible score of 18.

Conclusions

The authors demonstrate qualitative and quantitative benefits of a range of neurosurgical simulators but find significant shortfalls in methodology and design. Future studies should seek to improve study design and reporting, and provide long-term follow-up data on simulated and ideally patient outcomes.

Postmortem pump-driven reperfusion of the vascular system of porcine lungs: towards a new model for surgical training

PURPOSE

The objective of this experiment is to establish a continuous postmortem circulation in the vascular system of porcine lungs and to evaluate the pulmonary distribution of the perfusate. This research is performed in the bigger scope of a revascularization project of Thiel embalmed specimens. This technique enables teaching anatomy, practicing surgical procedures and doing research under lifelike circumstances.

METHODS

After cannulation of the pulmonary trunk and the left atrium, the vascular system was flushed with paraffinum perliquidum (PP) through a heart-lung machine. A continuous circulation was then established using red PP, during which perfusion parameters were measured. The distribution of contrast-containing PP in the pulmonary circulation was visualized on computed tomography. Finally, the amount of leak from the vascular system was calculated.

RESULTS

A reperfusion of the vascular system was initiated for 37 min. The flow rate ranged between 80 and 130 ml/min throughout the experiment with acceptable perfusion pressures (range: 37-78 mm Hg). Computed tomography imaging and 3D reconstruction revealed a diffuse vascular distribution of PP and a decreasing vascularization ratio in cranial direction. A self-limiting leak (i.e. 66.8% of the circulating volume) towards the tracheobronchial tree due to vessel rupture was also measured.

CONCLUSIONS

PP enables circulation in an isolated porcine lung model with an acceptable pressure-flow relationship resulting in an excellent recruitment of the vascular system. Despite these promising results, rupture of vessel walls may cause leaks. Further exploration of the perfusion capacities of PP in other organs is necessary. Eventually, this could lead to the development of reperfused Thiel embalmed human bodies, which have several applications.

Endoscope-assisted retrosigmoid resection of a medium size vestibular schwannoma tumor model: a cadaveric study

OBJECTIVE

To demonstrate a flexible endoscope assisted technique to perform microsurgical resection using a retrosigmoid approach of an artificial polymer tumor model that mimics a medium size (15-20mm diameter) vestibular schwannoma.

METHODS

Twelve bilateral retrosigmoid dissections were performed in 6 glutaraldehyde embalmed, colored silicone injected, adult cadaveric heads. Using a standard retrosigmoid approach, we first implanted the tumor model at the cerebellopontine angle (CPA) and then we resected the tumor under simultaneous endoscopic and microscopic visualizations. The resection was performed by first creating a corridor by removing the lower portion of the tumor and then by inserting through the same corridor the flexible endoscope mounted on a surgical instrument in order to accomplish early visualization of the VII-VIII complex. This early visualization of the VII-VIII complex made possible expeditious removal of the model with preservation of the VII-VIII complex.

RESULTS

We were able to successfully implant the artificial tumor in all the specimens. The post-tumor implantation CT scan confirmed the optimal CPA location of the model with its intra-porus extension. The exposure of the facial and the adjoining neuro-vascular structures was excellent during all stages of the surgical removal and was accomplished with minimal cerebellar retraction, under intermittent endoscopic-assisted control. Early visualization of the facial and vestibular cochlear nerves complex led to unhindered removal of the tumor model.

CONCLUSIONS

The endoscopic-assisted microsurgical removal of a tumor model simulating a medium size vestibular schwannoma was feasible in our tumor model study emulating real surgery. Visualization of the acousticofacial bundle at the early stage of the surgical removal should theoretically decrease the risk of its inadvertent injuries as well as facilitate complete removal of the tumor. Clinical studies to validate this laboratory study are necessary.

An endoscopic-assisted technique for retrosellar access during the extended retrosigmoid approach: a cadaveric feasibility study and quantitative analysis of retrosellar working area

The retrosigmoid approach has been advocated for certain petroclival tumors but provides limited access to any retrosellar extension of tumor, necessitating a two-stage operation. Our purpose was to demonstrate preliminary feasibility of an endoscopic-assisted technique to provide retrosellar access during the extended retrosigmoid approach and compare microscopic and endoscopic retrosellar working area. Standard retrosigmoid craniectomy and partial petrosectomy respecting inner ear structures were performed on six embalmed cadaveric heads. Two balloons were inflated to simulate a 15 mm petroclival tumor. Retrosellar clival and brainstem working area and ipsilateral oculomotor nerve and posterior cerebral artery (PCA) working distance were measured using the endoscope and microscope. Artificial tumors were implanted and resected using the endoscopic-assisted technique to assess feasibility. The endoscope provided significantly greater mean working area/distance on the clivus (201.6 vs 114.8 mm(2), p < 0.01), brainstem (223.5 vs 121.2 mm(2), p < 0.01), ipsilateral oculomotor nerve (10.8 vs 6.4 mm, p < 0.01), and ipsilateral PCA (13.7 vs 8.9 mm, p = 0.01). Petrous dissection to create a 10 × 10 mm working channel and artificial tumor resection was feasible in all dissections. The superior petrosal vein required ligation in 9 (75%) cases. Air cells were exposed in 1 (8%) case. The described endoscopic-assisted technique can provide retrosellar access during the extended retrosigmoid approach to access petroclival tumors with retrosellar extension. Risks include superior petrosal vein sacrifice, bleeding that can impair visualization, injury to the trigeminal nerve during endoscopic insertion/manipulation or injury to the brainstem while working in the medial limits of exposure. Further work is necessary to determine clinical feasibility, safety, and efficacy.

Shortening the learning curve in endoscopic endonasal skull base surgery: a reproducible polymer tumor model for the trans-sphenoidal trans-tubercular approach to retro-infundibular tumors

BACKGROUND

Endoscopic endonasal skull base surgery attracts an increasing number of young neurosurgeons. This recent technique requires specific technical skills for the approaches to non-pituitary tumors (expanded endoscopic endonasal surgery). Actual residents' busy schedules carry the risk of compromising their laboratory training by limiting significantly the dedicated time for dissections.

OBJECTIVE

To enhance and shorten the learning curve in expanded endoscopic endonasal skull base surgery, we propose a reproducible model based on the implantation of a polymer via an intracranial route to provide a pathological retro-infundibular expansive lesion accessible to a virgin expanded endoscopic endonasal route, avoiding the ethically-debatable need to hundreds of pituitary cases in live patients before acquiring the desired skills.

METHODS

A polymer-based tumor model was implanted in 6 embalmed human heads via a microsurgical right fronto-temporal approach through the carotido-oculomotor cistern to mimic a retro-infundibular tumor. The tumor's position was verified by CT-scan. An endoscopic endonasal trans-sphenoidal trans-tubercular trans-planum approach was then carried out on a virgin route under neuronavigation tracking.

RESULTS

Dissection of the tumor model from displaced surrounding neurovascular structures reproduced live surgery's sensations and challenges. Post-implantation CT-scan allowed the pre-removal assessment of the tumor insertion, its relationships as well as naso-sphenoidal anatomy in preparation of the endoscopic approach.

CONCLUSION

Training on easily reproducible retro-infundibular approaches in a context of pathological distorted anatomy provides a unique opportunity to avoid the need for repetitive live surgeries to acquire skills for this kind of rare tumors, and may shorten the learning curve for endoscopic endonasal surgery.

Practical guidelines for setting up an endoscopic/skull base cadaver laboratory

Adequate training based on cadaveric dissection is essential to acquire a practical knowledge of surgical anatomy and microsurgical/endoscopic dissection techniques. Endoscopic procedures for the treatment of pathologies of the skull base are becoming increasingly common. The endoscopic training curve for tool handling and a detailed knowledge of the topographic anatomy of the skull base require intensive training on cadavers before approaching living patients, which is why cadaver laboratory experience should be mandatory for every resident and surgeon preparing to use microsurgical and endoscopic techniques. We describe the basic principles of the philosophy of anatomic dissection and the equipment necessary to set up an endoscopic cadaver laboratory.

Setting up a microneurosurgical skull base lab: technical and operational considerations

Microneurosurgical cadaveric dissections have become popular due to their usefulness in obtaining a working knowledge of the microneurosurgical anatomy in a controlled environment. This same controlled environment is also conducive to experiment with new surgical approaches. These factors have increased the number of microneurosurgical anatomic laboratories. Despite the increase in microneurosurgical laboratories, there is very little literature regarding the logistics of starting and maintaining a new neurosurgical laboratory. The aim of this paper is to provide a general road map and basic guidelines in starting and running a microneurosurgical dissection laboratory. The information in this paper is based on a review of the literature and on the experience we gained in organizing and managing the Dardinger Microneurosurgical Skull Base Laboratory at The Ohio State University.