Virtual Reality Simulation for the Middle Cranial Fossa Approach: A Validation Study.

BACKGROUND AND OBJECTIVES: Virtual reality (VR) surgical rehearsal is an educational tool that exists in a safe environment. Validation is necessary to establish the educational value of this platform. The middle cranial fossa (MCF) is ideal for simulation because trainees have limited exposure to this approach and it has considerable complication risk. Our objectives were to assess the face, content, and construct validities of an MCF VR simulation, as well as the change in performance across serial simulations. METHODS: Using high-resolution volumetric data sets of human cadavers, the authors generated a high-fidelity visual and haptic rendering of the MCF approach using CardinalSim software. Trainees from Neurosurgery and Otolaryngology-Head and Neck Surgery at two Canadian academic centers performed MCF dissections on this VR platform. Randomization was used to assess the effect of enhanced VR interaction. Likert scales were used to assess the face and content validities. Performance metrics and pre- and postsimulation test scores were evaluated. Construct validity was evaluated by examining the effect of the training level on simulation performance. RESULTS: Twenty trainees were enrolled. Face and content validities were achieved in all domains. Construct validity, however, was not demonstrated. Postsimulation test scores were significantly higher than presimulation test scores ( P < .001 ). Trainees demonstrated statistically significant improvement in the time to complete dissections ( P < .001 ), internal auditory canal skeletonization ( P < .001 ), completeness of the anterior petrosectomy ( P < .001 ), and reduced number of injuries to critical structures ( P = .001 ). CONCLUSION: This MCF VR simulation created using CardinalSim demonstrated face and content validities. Construct validity was not established because no trainee included in the study had previous MCF approach experience, which further emphasizes the importance of simulation. When used as a formative educational adjunct in both Neurosurgery and Otolaryngology-Head and Neck Surgery, this simulation has the potential to enhance understanding of the complex anatomic relationships of critical neurovascular structures.

Non-contrast Enhancing Group A Streptococcus Subdural Empyema: An Illustrative Case Report of a Potential Radiographic Pitfall.

Subdural empyemas (SDEs) are an uncommon complication of intracranial infection, typically presenting as a hypodense collection with peripheral contrast enhancement. Herein, we report two rare cases of SDE without contrast enhancement, both secondary to group A streptococcus. The first is a 27-year-old previously healthy female, at 27 weeks of gestational age who presented with fever, headache, neurological decline, and blood cultures positive for gram-positive cocci. The second case is a previously healthy 48-year-old male who presented with left-sided otalgia, fever, headache, and precipitous decline in altered mental status and hemiplegia. Computed tomography (CT) and magnetic resonance imaging (MRI) in both cases showed a subdural collection without contrast enhancement and without diffusion restriction. Despite appearances similar to subdural effusion, because of a heightened suspicion due to clinical decline, both were taken to surgery for irrigation and debridement which confirmed SDE. Both patients were treated with six weeks of intravenous antibiotics and eventually recovered without neurological deficits. SDEs are uncommon but clinically significant phenomena. These two cases demonstrate that SDEs in rare circumstances may present as non-enhancing subdural collections. Missing the diagnosis of SDE can have significant consequences to patient morbidity and mortality and as such, it not be excluded based on radiographic findings alone.

Malignant Cerebellopontine Angle Peripheral Nerve Sheath Tumor with Divergent Mesenchymal (Cartilaginous) Differentiation Presenting with Catastrophic Hemorrhage: Case Report and Review.

Malignant peripheral nerve sheath tumors of the cerebellopontine angle are rare, especially even outside of the context of neurofibromatosis or malignant transformation of previously radiated vestibular schwannomas. This case report describes a case of a presumed vestibular schwannoma without previous radiation or history of neurofibromatosis presenting with progressive hearing loss, facial weakness, growth, and ultimately catastrophic hemorrhage requiring urgent surgery. Histopathology revealed an exceptionally rare malignant peripheral nerve sheath tumor with divergent mesenchymal (chondrosarcomatous) differentiation with few rigorously interrogated cases in the literature. In retrospect, facial weakness, growth, and early intratumoral hemorrhage were harbingers of atypical malignant pathology. We advocate for a heightened index of suspicion, shorter interval follow-up, and consideration of early surgery in such cases in hopes of preventing potentially catastrophic outcomes.

The user experience design of a novel microscope within SurgiSim, a virtual reality surgical simulator.

PURPOSE: Virtual reality (VR) simulation has the potential to advance surgical education, procedural planning, and intraoperative guidance. "SurgiSim" is a VR platform developed for the rehearsal of complex procedures using patient-specific anatomy, high-fidelity stereoscopic graphics, and haptic feedback. SurgiSim is the first VR simulator to include a virtual operating room microscope. We describe the process of designing and refining the VR microscope user experience (UX) and user interaction (UI) to optimize surgical rehearsal and education. METHODS: Human-centered VR design principles were applied in the design of the SurgiSim microscope to optimize the user's sense of presence. Throughout the UX's development, the team of developers met regularly with surgeons to gather end-user feedback. Supplemental testing was performed on four participants. RESULTS: Through observation and participant feedback, we made iterative design upgrades to the SurgiSim platform. We identified the following key characteristics of the VR microscope UI: overall appearance, hand controller interface, and microscope movement. CONCLUSION: Our design process identified challenges arising from the disparity between VR and physical environments that pertain to microscope education and deployment. These roadblocks were addressed using creative solutions. Future studies will investigate the efficacy of VR surgical microscope training on real-world microscope skills as assessed by validated performance metrics.

A phase II pilot randomized controlled trial to assess the feasibility of the "supra-marginal" surgical resection of malignant glioma (G-SUMIT: Glioma supra marginal incision trial) study protocol.

BACKGROUND: High-grade gliomas are the most common primary malignant brain tumor in adults having a median survival of only 13-16 months. This is despite the current standard of maximal safe surgical resection followed by fractionated radiotherapy and chemotherapy. Extending the tumor resection limit beyond the gadolinium (GAD)-enhancing margin (i.e., supra-marginal resection) could in principle provide an added survival benefit as it has been shown that > 80% of post-operative tumor recurrence is within a 2-cm region surrounding the original GAD-enhancing margin. However, this must be weighed against the risk of potential damage to functional brain tissue. METHODS: In this phase II pilot randomized control trial (RCT), we aim to assess the feasibility of "supra-marginal" resection extending 1 cm beyond the enhancing tumor in adults with radiographic evidence of GAD-enhancing intra-axial tumor consistent with high-grade glioma in a safe anatomical location and a Karnofsky Performance Score > 60. With six academic institutions with established neurosurgical oncology practices in participation, we aim to enroll 72 patients over 2 years. Primary outcomes include evaluating the feasibility of performing a large-scale trial with regard to recruitment, allocation, and outcome documentation as well as safety data. Secondary outcomes include determining if there is an increased survival benefit with supra-marginal resection and impact on quality of life (Modified Rankin Scale (mRS), EuroQol-5D (ED-5D), 30-day all-cause mortality). DISCUSSION: Recent studies have revealed survival advantages comparing supra-marginal resection to standard attempt at gross total resection (GTR) with no additional perioperative surgical risk; however, the current quality of evidence is low and under-powered. Therefore, there are no current practice guidelines, and the philosophy of surgical resection is guided by individual surgeon preferences on an individual patient basis. This creates additional uncertainty and is potentially detrimental to our patients. This clinical equipoise supports the need for an adequately powered RCT to determine whether a supra-marginal resection can have a positive impact on survival for patients with HGGs. Our pilot RCT will test the feasibility of comparing the standard gross total resection of GAD-enhancing tumors and supra-marginal resection to prepare for a larger definitive multicenter RCT. TRIAL REGISTRATION: ClinicalTrials.gov , NCT04737577. Registered on February 4, 2021.

Machine-vision image guided C4-C5 unilateral cervical pedicle screw insertion: case report and review of literature.

Computer-assistance for pedicle screw insertion is becoming increasingly common. As in the case presented below, image guided neuronavigation can be used to improve the accuracy and safety of subaxial cervical pedicle screw placement, given their increased difficulty of cannulation relative to the larger pedicles in the thoracolumbar spine. A 49-year-old man presented with a traumatic sagittal split fracture of C4 (AO Classification type A4) and a left lateral mass fracture of C5 (AO Classification type F1) with anterior depression and 50% height loss. MRI revealed evidence of strain of the interspinous/supraspinous ligaments (AO Classification type B2), as well as fluid within the left C4-C5 facet joint. Along with these fractures, the young patient had Klippel-Feil syndrome with autofusion of the C2-3 posterior elements, and a left vertebral artery dissection. He had neck pain but was otherwise neurologically intact. The patient underwent machine-vision image guided C4-C5 unilateral pedicle screw insertion connected by a fixation rod for stabilization and bone graft to augment the instrumented fusion with good outcome. The use of machine vision spinal navigation was able to provide accurate and precise placement of pedicle screws without significantly increasing surgical time. This method has the potential to allow for the safe and accurate insertion of cervical pedicle screws and to reduce the rate of pedicle breach which could avoid significant neurovascular injury.

High-Fidelity Virtual Reality Simulation for the Middle Cranial Fossa Approach-Modules for Surgical Rehearsal and Education.

BACKGROUND: Virtual reality simulation has gained prominence as a valuable surgical rehearsal and education tool in neurosurgery. Approaches to the internal auditory canal, cerebellopontine angle, and ventral brainstem region using the middle cranial fossa are not well explored by simulation. OBJECTIVE: We hope to contribute to this paucity in simulation tools devoted to the lateral skull base, specifically the middle cranial fossa approach. METHODS: Eight high-resolution microcomputed tomography scans of human cadavers were used as volumetric data sets to construct a high-fidelity visual and haptic rendering of the middle cranial fossa using CardinalSim software. Critical neurovascular structures related to this region of the skull base were segmented and incorporated into the modules. RESULTS: The virtual models illustrate the 3-dimensional anatomic relationships of neurovascular structures in the middle cranial fossa and allow a realistic interactive drilling environment. This is facilitated by the ability to render bone opaque or transparent to reveal the proximity to critical anatomy allowing for practice of the virtual dissection in a graduated fashion. CONCLUSION: We have developed a virtual library of middle cranial fossa approach models, which integrate relevant neurovascular structures with aims to improve surgical training and education. A ready extension is the potential for patient-specific application and pathology.

Endoscopic Treatment of Rathke's Cleft Cysts: The Case for Simple Fenestration.

BACKGROUND: Rathke's cleft cysts (RCC) arise from the pars intermedia because of incomplete regression of the embryologic Rathke pouch. A subset of RCC becomes symptomatic causing headaches, visual and endocrinological disturbances such that surgical intervention is indicated. Several points in surgical management remain controversial including operative strategy (simple fenestration (SF) vs complete cyst wall resection (CWR)) as well as reconstructive techniques. METHODS: A retrospective analysis was conducted of pathologically confirmed RCC operated on by endoscopic endonasal approach from 2006 to 2019. Pre-operative symptoms, imaging characteristics, operative strategy, symptom response, complications and recurrences were recorded. RESULTS: Thirty-nine patients were identified. Thirty-three underwent SF and six underwent CWR. Worsening pituitary function was significantly increased with CWR (50%) compared to SF (3%) (p = 0.008). All patients underwent "closed" reconstruction with a post-operative CSF leak rate of 5% (3% SF vs 16% CWR, p = 0.287). Six (15%) recurrences necessitating surgery were reported. Recurrence rates stratified by surgical technique (18% SF vs 0% CWR, p = 0.564) were not found to be significantly different. CONCLUSIONS: The current series illustrates variability in the surgical management of RCCs. SF with closed reconstruction is a reasonable operative strategy for most symptomatic RCCs cases while CWR can be reserved for selected cases.

Ventriculopleural shunts in a pediatric population: a review of 170 consecutive patients.

OBJECTIVE: The authors sought to determine the outcome of using the pleural space as the terminus for ventricular CSF-diverting shunts in a pediatric population. METHODS: All ventriculopleural (VPl) shunt insertions or revisions done between 1978 and 2018 in patients at Children's Hospital Los Angeles were identified. Data recorded for analysis were age, sex, weight, etiology of hydrocephalus, previous shunt history, reason for VPl shunt insertion or conversion from a ventriculoperitoneal (VP) or ventriculoatrial (VA) shunt, valve type, nature of malfunction, presence of shunt infection or pleural effusion, and conversion to a different distal site. RESULTS: A total of 170 patients (mean age 14 ± 4 years) with a VPl shunt who were followed up for a mean of 57 ± 53 months were identified. The reasons for conversion to a VPl shunt for 167 patients were previous shunt infection in 57 (34%), multiple abdominal procedures in 44 (26%), inadequate absorption of CSF in 34 (20%), abdominal pseudocyst in 25 (15%), and obesity in 7 (4%). No VPl revisions were required in 97 (57%) patients. Of the 73 (43%) patients who did require revision, the most common reason was proximal obstruction in 32 (44%). The next most frequent complication was pleural effusion in 22 (30%) and included 3 patients with shunt infection. All 22 patients with a clinically significant pleural effusion required changing the distal end of the shunt from the pleural space. Pleural effusion was more likely to occur in VPl shunts without an antisiphon valve. Of the 29 children < 10 years old, 7 (24%) developed a pleural effusion requiring a revision of the distal catheter to outside the pleural space compared with 15 (11%) who were older (p = 0.049). There were 14 shunt infections with a rate of 4.2% per procedure and 8.2% per patient. CONCLUSIONS: VPl shunts in children younger than 10 years of age have a significantly higher rate of symptomatic pleural effusion, requiring revision of the shunt's terminus to a different location. VPl shunt complication rates are similar to those of VP shunts. The technical difficulty of inserting a VPl shunt is comparable to that of a VP shunt. In a patient older than 10 years, all else being equal, the authors recommend that the distal end of a shunt be placed into the pleural space rather than the right atrium if the peritoneal cavity is not suitable.

Tau pathology reduction with SM07883, a novel, potent, and selective oral DYRK1A inhibitor: A potential therapeutic for Alzheimer's disease.

Dual-specificity tyrosine phosphorylation-regulated kinase-1A (DYRK1A) is known to phosphorylate the microtubule-associated tau protein. Overexpression is correlated with tau hyperphosphorylation and neurofibrillary tangle (NFT) formation in Alzheimer's disease (AD). This study assessed the potential of SM07883, an oral DYRK1A inhibitor, to inhibit tau hyperphosphorylation, aggregation, NFT formation, and associated phenotypes in mouse models. Exploratory neuroinflammatory effects were also studied. SM07883 specificity was tested in a kinase panel screen and showed potent inhibition of DYRK1A (IC50  = 1.6 nM) and GSK-3ß (IC50  = 10.8 nM) kinase activity. Tau phosphorylation measured in cell-based assays showed a reduction in phosphorylation of multiple tau epitopes, especially the threonine 212 site (EC50  = 16 nM). SM07883 showed good oral bioavailability in multiple species and demonstrated a dose-dependent reduction of transient hypothermia-induced phosphorylated tau in the brains of wild-type mice compared to vehicle (47%, p < 0.001). Long-term efficacy assessed in aged JNPL3 mice overexpressing the P301L human tau mutation (3 mg/kg, QD, for 3 months) exhibited significant reductions in tau hyperphosphorylation, oligomeric and aggregated tau, and tau-positive inclusions compared to vehicle in brainstem and spinal cord samples. Reduced gliosis compared to vehicle was further confirmed by ELISA. SM07883 was well tolerated with improved general health, weight gain, and functional improvement in a wire-hang test compared to vehicle-treated mice (p = 0.048). SM07883, a potent, orally bioavailable, brain-penetrant DYRK1A inhibitor, significantly reduced effects of pathological tau overexpression and neuroinflammation, while functional endpoints were improved compared to vehicle in animal models. This small molecule has potential as a treatment for AD.

The role of botulinum toxin a in the establishment of symmetry in pediatric paralysis of the lower lip.

IMPORTANCE: Botulinum toxin A has been described as an effective adjunct treatment for achieving symmetry in adults with facial paralysis. Few investigators have described the use of botulinum toxin A in pediatric patients with facial paralysis. OBJECTIVE: To present our preliminary experience with botulinum toxin A in pediatric patients presenting with asymmetry of the lower lip. DESIGN, SETTING, AND PARTICIPANTS: We performed a retrospective medical record review of all pediatric patients (age range, 4-17 years; mean [SD] age, 11.2 [4.7] years) with facial paralysis who were treated with botulinum toxin A injections from January 1, 2004, through December 31, 2012. Patients presented for treatment at The Hospital for Sick Children, Toronto, Ontario, Canada, or the Massachusetts Eye and Ear Infirmary, Boston. MAIN OUTCOMES AND MEASURES: Using facial analysis software, we measured lower lip asymmetry in the patients' photographs before and after treatment, at rest, and in a dynamic state. We performed analysis of variance to assess for improvement in symmetry. RESULTS: We identified 18 patients with the following 3 primary indications for treatment: focal lip asymmetry (n = 11), extensive hemifacial asymmetry (n = 5), and focal synkinesis (n = 2). We found no complications related to botulinum toxin A treatment. The mean (SD) dynamic deviation before the injection was 3.5 (1.7) mm, whereas the mean dynamic deviation after the injection was 1.5 (0.8) mm. The mean (SD) deviation correction was evaluated at 61% (6%) and was statistically significant (P = .04). CONCLUSIONS AND RELEVANCE: Botulinum toxin A injection is a safe procedure for improving localized asymmetry in pediatric patients with facial paralysis. Preliminary results indicate that botulinum toxin A may be an effective treatment for lower lip asymmetry in children and adolescents. LEVEL OF EVIDENCE: 4.