Feasibility of ventricular expansion postmortem: a novel laboratory model for neurosurgical training that simulates intraventricular endoscopic surgery

Endoscopic neuroanatomy study using embalmed cadavers

Objectives

A firm understanding of anatomy is foundational for all medical students and residents. As opportunities for cadaveric study dwindle, we propose a simplified perfusion model for formalin fixed cadavers that allow for endoscopic neuroanatomical study and procedural practice. This model is easily accessible, cost effective, and valuable in medical training.

Materials and Methods

Cadavers were fixed through accepted methods that included formalin injection into the cranial vault. The perfusion system was set up using a series of catheters, tubing, and pressurized saline bag that forced saline into the various neuroanatomical spaces chosen for study.

Results

A neuroendoscope was subsequently introduced to explore and identify relevant neuroanatomical structures as well as to perform a 3rd ventriculostomy and filum sectioning.

Conclusion

Using formalin fixed cadavers for neuroendoscopic studies and procedural practice is a cost effective, multipurpose tool that can provide medical trainees with a strong understanding of anatomy as well as procedural practice.

Neuroendoscopic training in neurosurgery: a simple and feasible model for neurosurgical education

BACKGROUND

The development of high levels of technical competence and excellent decision-making skills are key goals of all neurosurgical residency training programs. This acquisition of technical skills is becoming increasingly difficult due to many factors including less exposure to operative cases, demand for more time and cost-effective practices, and resident work hour restrictions. We describe a step-by-step method for how to build a low-cost and feasible model that allows residents to improve their neuroendoscopic skills.

METHODS

The bell pepper-based model was developed as an endoscopic training model. Using continuous irrigation, several hands-on procedures were proposed under direct endoscopic visualization. Endoscope setup, endoscopic third ventriculostomy, septostomy, and tumor biopsy procedures were simulated and video recorded for further edition and analysis.

RESULTS

The model can be setup in less than 15 min with minimal cost and infrastructure requirements. A single model allows simulation of all the exercises described above. The model allows exposure to the camera skills, instrument handling, and hand-eye coordination inherent to most neuroendoscopic procedures.

CONCLUSION

Minimal infrastructure requirements, simplicity, and easily setup models provide a proper environment for regular training. The bell pepper-based model is inexpensive, widely available, and a feasible model for routine training. Neurosurgery residents may benefit from the use of this model to accelerate their learning curve and familiarize themselves with the neuroendoscopic core principles in a risk-free environment without time or resource constraints.

Cerebrospinal Fluid Leak Repair Simulation Model: Face, Content, and Construct Validation

Background

Cerebrospinal fluid leak (CSFL) repair simulation models are scarce; however, these models are valuable tools for skull base reconstruction surgery training.

Objectives

This study aims to assess the face, content, and construct validity of a CSFL repair simulation model.

Method

Eight novices (residents- PGY3) and eight experts have performed skull base reconstruction in multiple sites in twelve human cadaveric heads in simulated surgical environment. The experts completed a post-study 21-item questionnaire to assess the face and content validity. The performances of the participants were recorded and scored by two independent investigators who were blinded to the participant's level. Global Rating Scale of Operative Performance (GRSOP) and a Specific Skull Base Reconstruction Checklist (SBRC) were used to score the performances.

Results

The responses from the expert group for the 21-item questionnaire were high for all items (4.13–4.88 out of 5). The internal consistency reliability of the questionnaire and the intraclass correlation, which was derived by Cronbach’s Alpha, were 0.913 and 0.941 respectively. Differences in construct validity between the two groups were statistically significant for both the GRSOP and SBRS (P-value < 0.001).

Conclusion

We demonstrated the face, content, and construct validity of the CSFL repair simulation model, which facilitates the acquisition of technical skills necessary for skull base reconstruction surgery. The model includes realistic features that make it useful in educational courses.

Development and evaluation of a patient-specific surgical simulator for endoscopic colloid cyst resection

OBJECTIVE

Endoscopic resection of third-ventricle colloid cysts is technically challenging due to the limited dexterity and visualization provided by neuroendoscopic instruments. Extensive training and experience are required to master the learning curve. To improve the education of neurosurgical trainees in this procedure, a synthetic surgical simulator was developed and its realism, procedural content, and utility as a training instrument were evaluated.

METHODS

The simulator was developed based on the neuroimaging (axial noncontrast CT and T1-weighted gadolinium-enhanced MRI) of an 8-year-old patient with a colloid cyst and hydrocephalus. Image segmentation, computer-aided design, rapid prototyping (3D printing), and silicone molding techniques were used to produce models of the skull, brain, ventricles, and colloid cyst. The cyst was filled with a viscous fluid and secured to the roof of the third ventricle. The choroid plexus and intraventricular veins were also included. Twenty-four neurosurgical trainees performed a simulated colloid cyst resection using a 30° angled endoscope, neuroendoscopic instruments, and image guidance. Using a 19-item feedback survey (5-point Likert scales), participants evaluated the simulator across 5 domains: anatomy, instrument handling, procedural content, perceived realism, and confidence and comfort level.

RESULTS

Participants found the simulator's anatomy to be highly realistic (mean 4.34 ± 0.63 [SD]) and appreciated the use of actual instruments (mean 4.38 ± 0.58). The procedural content was also rated highly (mean 4.28 ± 0.77); however, the perceived realism was rated slightly lower (mean 4.08 ± 0.63). Participants reported greater confidence in their ability to perform an endoscopic colloid cyst resection after using the simulator (mean 4.45 ± 0.68). Twenty-three participants (95.8%) indicated that they would use the simulator for additional training. Recommendations were made to develop complex case scenarios for experienced trainees (normal-sized ventricles, choroid plexus adherent to cyst wall, bleeding scenarios) and incorporate advanced instrumentation such as side-cutting aspiration devices.

CONCLUSIONS

A patient-specific synthetic surgical simulator for training residents and fellows in endoscopic colloid cyst resection was successfully developed. The simulator's anatomy, instrument handling, and procedural content were found to be realistic. The simulator may serve as a valuable educational tool to learn the critical steps of endoscopic colloid cyst resection, develop a detailed understanding of intraventricular anatomy, and gain proficiency with bimanual neuroendoscopic techniques.

Perfusion-based human cadaveric specimen as a simulation training model in repairing cerebrospinal fluid leaks during endoscopic endonasal skull base surgery

OBJECTIVE

Competency in endoscopic endonasal approaches (EEAs) to repair high-flow cerebrospinal fluid (CSF) leaks is an essential component of the neurosurgical training process. The objective of this study was to demonstrate the feasibility of a simulation model for EEA repair of anterior skull base CSF leaks.

METHODS

Human cadaveric specimens were utilized with a perfusion system to simulate a high-flow CSF leak. Neurological surgery residents (postgraduate year 3 or greater) performed a standard EEA to repair a CSF leak using a combination of fat, fascia lata, and pedicled nasoseptal flaps. A standardized 5-point Likert questionnaire was used to assess the knowledge gained, techniques learned, degree of safety, benefit of CSF perfusion during repair, and pre- and posttraining confidence scores.

RESULTS

Intrathecal perfusion of fluorescein-infused saline into the ventricular/subarachnoid space was successful in 9 of 9 cases. The addition of CSF reconstitution offered the residents visual feedback for confirmation of intraoperative CSF leak repair. Residents gained new knowledge and a realistic simulation experience by rehearsing the psychomotor skills and techniques required to repair a CSF leak with fat and fascial grafts, as well as to prepare and rotate vascularized nasoseptal flaps. All trainees reported feeling safer with the procedure in a clinical setting and higher average posttraining confidence scores (pretraining 2.22 ± 0.83, posttraining 4.22 ± 0.44, p < 0.001).

CONCLUSIONS

Perfusion-based human cadaveric models can be utilized as a simulation training model for repairing CSF leaks during EEA.

Development of synthetic simulators for endoscope-assisted repair of metopic and sagittal craniosynostosis

OBJECTIVE Endoscope-assisted repair of craniosynostosis is a safe and efficacious alternative to open techniques. However, this procedure is challenging to learn, and there is significant variation in both its execution and outcomes. Surgical simulators may allow trainees to learn and practice this procedure prior to operating on an actual patient. The purpose of this study was to develop a realistic, relatively inexpensive simulator for endoscope-assisted repair of metopic and sagittal craniosynostosis and to evaluate the models' fidelity and teaching content. METHODS Two separate, 3D-printed, plastic powder-based replica skulls exhibiting metopic (age 1 month) and sagittal (age 2 months) craniosynostosis were developed. These models were made into consumable skull "cartridges" that insert into a reusable base resembling an infant's head. Each cartridge consists of a multilayer scalp (skin, subcutaneous fat, galea, and periosteum); cranial bones with accurate landmarks; and the dura mater. Data related to model construction, use, and cost were collected. Eleven novice surgeons (residents), 9 experienced surgeons (fellows), and 5 expert surgeons (attendings) performed a simulated metopic and sagittal craniosynostosis repair using a neuroendoscope, high-speed drill, rongeurs, lighted retractors, and suction/irrigation. All participants completed a 13-item questionnaire (using 5-point Likert scales) to rate the realism and utility of the models for teaching endoscope-assisted strip suturectomy. RESULTS The simulators are compact, robust, and relatively inexpensive. They can be rapidly reset for repeated use and contain a minimal amount of consumable material while providing a realistic simulation experience. More than 80% of participants agreed or strongly agreed that the models' anatomical features, including surface anatomy, subgaleal and subperiosteal tissue planes, anterior fontanelle, and epidural spaces, were realistic and contained appropriate detail. More than 90% of participants indicated that handling the endoscope and the instruments was realistic, and also that the steps required to perform the procedure were representative of the steps required in real life. CONCLUSIONS Both the metopic and sagittal craniosynostosis simulators were developed using low-cost methods and were successfully designed to be reusable. The simulators were found to realistically represent the surgical procedure and can be used to develop the technical skills required for performing an endoscope-assisted craniosynostosis repair.

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.

Surgical Training for the Implantation of Neocortical Microelectrode Arrays Using a Formaldehyde-fixed Human Cadaver Model

This protocol describes a procedure to assist surgeons in training for the implantation of microelectrode arrays into the neocortex of the human brain. Recent technological progress has enabled the fabrication of microelectrode arrays that allow recording the activity of multiple individual neurons in the neocortex of the human brain. These arrays have the potential to bring unique insight onto the neuronal correlates of cerebral function in health and disease. Furthermore, the identification and decoding of volitional neuronal activity opens the possibility to establish brain-computer interfaces, and thus might help restore lost neurological functions. The implantation of neocortical microelectrode arrays is an invasive procedure requiring a supra-centimetric craniotomy and the exposure of the cortical surface; thus, the procedure must be performed by an adequately trained neurosurgeon. In order to provide an opportunity for surgical training, we designed a procedure based on a human cadaver model. The use of a formaldehyde-fixed human cadaver bypasses the practical, ethical and financial difficulties of surgical practice on animals (especially non-human primates) while preserving the macroscopic structure of the head, skull, meninges and cerebral surface and allowing realistic, operating room-like positioning and instrumentation. Furthermore, the use of a human cadaver is closer to clinical daily practice than any non-human model. The major drawbacks of the cadaveric simulation are the absence of cerebral pulsation and of blood and cerebrospinal fluid circulation. We suggest that a formaldehyde-fixed human cadaver model is an adequate, practical and cost-effective approach to ensure proper surgical training before implanting microelectrode arrays in the living human neocortex.

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.

Cerebrospinal fluid reconstitution via a perfusion-based cadaveric model: feasibility study demonstrating surgical simulation of neuroendoscopic procedures

Cadaveric surgical simulation carries the advantage of realistic anatomy and haptic feedback but has been historically difficult to model for intraventricular approaches given the need for active flow of CSF. This feasibility study was designed to simulate intraventricular neuroendoscopic approaches and techniques by reconstituting natural CSF flow in a cadaveric model. In 10 fresh human cadavers, a simple cervical laminectomy and dural opening were made, and a 12-gauge arterial catheter was introduced. Saline was continuously perfused at physiological CSF pressures to reconstitute the subarachnoid space and ventricles. A neuroendoscope was subsequently inserted via a standard right frontal bur hole. In 8 of the 10 cadavers, adequate reconstitution and endoscopic access of the lateral and third ventricles were achieved. In 2 cadavers, ventricular access was not feasible, perhaps because of a small ventricle size and/or deteriorated tissue quality. In all 8 cadavers with successful CSF flow reconstitution and endoscopic access, identifying the foramen of Monro was possible, as was performing septum pellucidotomy and endoscopic third ventriculostomy. Furthermore, navigation of the cerebral aqueduct, fourth ventricle, prepontine cistern, and suprasellar cistern via the lamina terminalis was possible, providing a complementary educational paradigm for resident education that cannot typically be performed in live surgery. Surgical simulation plays a critical and increasingly prominent role in surgical education, particularly for techniques with steep learning curves including intraventricular neuroendoscopic procedures. This novel model provides feasible and realistic surgical simulation of neuroendoscopic intraventricular procedures and approaches.

Design and evaluation of a new synthetic brain simulator for endoscopic third ventriculostomy

OBJECT

Endoscopic third ventriculostomy (ETV) is an effective but technically demanding procedure with significant risk. Current simulators, including human cadavers, animal models, and virtual reality systems, are expensive, relatively inaccessible, and can lack realistic sensory feedback. The purpose of this study was to construct a realistic, low-cost, reusable brain simulator for ETV and evaluate its fidelity.

METHODS

A brain silicone replica mimicking normal mechanical properties of a 4-month-old child with hydrocephalus was constructed, encased in the replicated skull, and immersed in water. Realistic intraventricular landmarks included the choroid plexus, veins, mammillary bodies, infundibular recess, and basilar artery. The thinned-out third ventricle floor, which dissects appropriately, is quickly replaceable. Standard neuroendoscopic equipment including irrigation is used. Bleeding scenarios are also incorporated. A total of 16 neurosurgical trainees (Postgraduate Years 1-6) and 9 pediatric and adult neurosurgeons tested the simulator. All participants filled out questionnaires (5-point Likert-type items) to rate the simulator for face and content validity.

RESULTS

The simulator is portable, robust, and sets up in minutes. More than 95% of participants agreed or strongly agreed that the simulator's anatomical features, tissue properties, and bleeding scenarios were a realistic representation of that seen during an ETV. Participants stated that the simulator helped develop the required hand-eye coordination and camera skills, and the training exercise was valuable.

CONCLUSIONS

A low-cost, reusable, silicone-based ETV simulator realistically represents the surgical procedure to trainees and neurosurgeons. It can help them develop the technical and cognitive skills for ETV including dealing with complications.

Ventricular endoscopy in the pediatric population: review of indications

INTRODUCTION

Neuroendoscopy has greatly impacted pediatric neurosurgery over the past few decades. Improved optics and microsurgical tools have allowed neuroendoscopes to be used for a multitude of neurosurgical procedures.

DISCUSSION

In this review article, we present the breadth of intraventricular neuroendoscopic procedures for the treatment of conditions ranging from hydrocephalus and brain tumors to congenital cysts and other pathologies. We critically discuss treatment indications and reported success rates for neuroendoscopic procedures. We also present novel approaches, technical nuances, and variations from recently published literature and as practiced in the authors' institution.

The incorporation of neuroendoscopy in neurosurgical training programs

Previously considered the domain of the otolaryngologists, the endoscopy is now a common part of the armamentarium of a neurosurgeon. Neuroendoscopy or endoscope-assisted microsurgery is now being used in almost all routine procedures performed in the neurosurgical operating room. Hands-on training has become essential to learn the basics of neuroendoscopy, even for neurosurgeons well accustomed to the use of microscopes. To decrease the slope of the learning curve of residents during their training and reduce complications of procedures, most neurosurgery training programs around the world have incorporated laboratory or dissection programs in their curricula. Preconference workshops held during annual meetings are also an excellent tool to aid in the transition of surgeons from being a resident under the umbrella of an attending neurosurgeon to being a neurosurgeon able to operate independently and with confidence. In this "tech-savvy era," various cadaver or synthetic models are readily available for endoscopy training in a virtually simulated environment. In accord with the results of a surveys conducted by individual groups and societies, the authors firmly believe that incorporation of endoscopy in the neurosurgical curriculum would add a new dimension to the existing protocol. There is an urgent need for dedicated endoscopy training programs similar to postresidency fellowships in addition to translational research and establishment of dedicated societies to formulate guidelines for such research and monitor its progress.

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.

Quality assessment of a new surgical simulator for neuroendoscopic training

Object

Ideal surgical training models should be entirely reliable, atoxic, easy to handle, and, if possible, low cost. All available models have their advantages and disadvantages. The choice of one or another will depend on the type of surgery to be performed. The authors created an anatomical model called the S.I.M.O.N.T. (Sinus Model Oto-Rhino Neuro Trainer) Neurosurgical Endotrainer, which can provide reliable neuroendoscopic training. The aim in the present study was to assess both the quality of the model and the development of surgical skills by trainees.

Methods

The S.I.M.O.N.T. is built of a synthetic thermoretractable, thermosensible rubber called Neoderma, which, combined with different polymers, produces more than 30 different formulas. Quality assessment of the model was based on qualitative and quantitative data obtained from training sessions with 9 experienced and 13 inexperienced neurosurgeons. The techniques used for evaluation were face validation, retest and interrater reliability, and construct validation.

Results

The experts considered the S.I.M.O.N.T. capable of reproducing surgical situations as if they were real and presenting great similarity with the human brain. Surgical results of serial training showed that the model could be considered precise. Finally, development and improvement in surgical skills by the trainees were observed and considered relevant to further training. It was also observed that the probability of any single error was dramatically decreased after each training session, with a mean reduction of 41.65% (range 38.7%–45.6%).

Conclusions

Neuroendoscopic training has some specific requirements. A unique set of instruments is required, as is a model that can resemble real-life situations. The S.I.M.O.N.T. is a new alternative model specially designed for this purpose. Validation techniques followed by precision assessments attested to the model's feasibility.

Minimally invasive endoscopic transventricular hemispherotomy for medically intractable epilepsy: a new approach and cadaveric demonstration

OBJECT

Surgery for medically intractable epilepsy secondary to unihemispheric pathology has evolved from more aggressive hemispherectomy to less aggressive variations of hemispherotomy. The authors propose a novel minimally invasive endoscopic hemispherotomy that should give results comparable to conventional open craniotomy and microsurgery.

METHODS

Endoscopic transventricular hemispherotomy was performed in 5 silicon-injected cadaveric heads in the authors' minimally invasive neurosurgery laboratory. The lateral ventricle was accessed endoscopically through a frontal and occipital bur hole. White matter disconnections were performed to unroof the temporal horn and to disconnect the frontobasal region, corpus callosum, and fornix.

RESULTS

Using an endoscopic transventricular approach, all white matter disconnections were successfully performed in all 5 cadavers.

CONCLUSIONS

The authors have demonstrated the feasibility of endoscopic transventricular hemispherotomy in a cadaveric model. The technique is simple and could be useful in a subgroup of patients with parenchymal volume loss and ventriculomegaly.