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Cover Journal of Neurosurgery: Case Lessons

Single-stage cranioplasty with customized polyetheretherketone implant after tumor resection using virtual reality and augmented reality for precise implant customization and placement: illustrative case

Christian I. Rios-Vicil, Daniela Barbery, Phuong Dang, and Walter C. Jean

BACKGROUND

Cranioplasties are routinely performed to restore cosmesis and to protect intracranial contents after trauma, resection of tumors, or other pathologies. Traditionally done as a second-stage procedure, new single-stage cranioplasty protocols have been developed to minimize recovery periods, decrease complications, and improve patient satisfaction. These protocols, however, still require the use of larger than planned implants or use larger than ideal incisions to accommodate three-dimensional (3D) templates, which may not be optimal in regions with complex bony anatomy.

OBSERVATIONS

A 50-year-old woman with a painful and progressively enlarging hemangioma of the left frontal bone underwent a single-stage resection followed by custom cranioplasty using a new extended reality (XR)-based workflow. Excellent cosmetic results, decreased operative time, and a feasible workflow were achieved.

LESSONS

The use of an XR-based visualization platform allows the surgeon to treat lesions and perform custom cranioplasties in one session while avoiding common pitfalls of current single-stage workflows, such as increased operative times for tailoring implants, as well as minimizing the use of 3D overlay models, which may not appropriately conform to complex regional bony anatomy intraoperatively.

Open access

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Cover Journal of Neurosurgery: Case Lessons

Middle cerebellar peduncle approach for Nocardia brainstem abscess: illustrative case

Aadit Mehta, Chase H. Foster, Christian I. Rios-Vicil, and Walter C. Jean

BACKGROUND

Nocardia cyriacigeorgica represents a rare cause of cerebral abscesses. Rarer still are brainstem abscesses caused by this bacterial species in immunocompetent hosts. In fact, only one such brainstem abscess case has been described in the neurosurgical literature to our knowledge to date. Herein, a case of Nocardia cyriacigeorgica abscess in the pons is reported, as well as a description of its surgical evacuation via the transpetrosal fissure, middle cerebellar peduncle approach. The authors review the utility of this well-described approach in treating such lesions safely and effectively. Finally, the authors briefly review, compare, and contrast related cases to this one.

OBSERVATIONS

Augmented reality is additive to and useful for well-described safe entry corridors to the brainstem. Despite surgical success, patients may not regain previously lost neurological function.

LESSONS

The transpetrosal fissure, middle cerebellar peduncle approach is safe and effective in evacuating pontine abscesses. Augmented reality guidance supplements but does not replace thorough knowledge of operative anatomy for this complex procedure. A reasonable degree of suspicion for brainstem abscess is prudent even in immunocompetent hosts. A multidisciplinary team is critical to the successful treatment of central nervous system Nocardiosis.

Open access

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Cover Neurosurgical Focus: Video

Augmented-reality template guided transorbital approach for intradural tumors

Walter C. Jean, Kenneth D. Sack, and Andrew R. Tsen

For “minimally invasive” approaches to a deep-lying skull base lesion, the bone opening must be precisely placed and adequately wide to accomplish the surgical goal. Surgical rehearsal in virtual reality (VR) can generate navigation-integrated augmented reality (AR) templates to ensure precise surgical openings.

In this video, the authors used AR templates for the transpalpebral, transorbital approach for intradural tumors. VR renderings of patient-specific anatomy were used in surgical rehearsal. The optimal openings were saved and, at surgery, projected into the eyepiece of the navigation-tracked microscope. The template enhanced the planning of the incision and soft-tissue exposure and guided the drill toward the target.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21172

Restricted access

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Cover Journal of Neurosurgery

Effects of continuous localized infusion of granulocyte—macrophage colony—stimulating factor and inoculations of irradiated glioma cells on tumor regression

Margaret A. Wallenfriedman, John A. Conrad, Lance DelaBarre, Patrick C. Graupman, Gina Lee, Michael Garwood, Dale S. Gregerson, Walter C. Jean, Walter A. Hall, and Walter C. Low

Object. Glioblastoma multiforme (GBM) is a malignant tumor of the central nervous system that directly suppresses immunological defenses in vitro and in vivo. The authors used the peripheral delivery of continuously infused granulocyte—macrophage colony-stimulating factor (GM-CSF) in the presence of irradiated tumor antigens as a tumor-specific stimulant to dendritic cells to initiate an immune response to GBM in rats.

Methods. The 9L gliosarcoma tumors were established in the flanks of syngeneic Fischer 344 rats. Osmotic minipumps implanted in the animals' contralateral flanks continuously delivered recombinant GM-CSF (0, 0.1, 1, or 10 ng/day) for 28 days. Irradiated gliosarcoma cells were intermittently injected at the site of the GM-CSF infusion. Animals in the saline control group (0 ng/day GM-CSF) died on Day 59 with average tumor volumes greater than 30,000 mm3. This control group was significantly different from the GM-CSF—treated animals, which all survived with average tumor volumes that peaked on Day 23 and later regressed completely. Tumor growth as well as peak tumor volumes (5833 ± 2284 mm3, 3294 ± 1632 mm3, and 1979 ± 1142 mm3 for 0.1, 1, and 10 ng/day GM-CSF, respectively) in the different treatment groups reflected a significant dose-response relationship with the GM-CSF concentrations. All animals treated with GM-CSF and irradiated cells were resistant to additional challenges of peripheral and intracerebral gliosarcoma, even when they were inoculated 8 months after initial immunotherapy. The colocalization of GM-CSF and inactivated tumor antigens was required to stimulate immunoprotection. To test the efficacy of a peripherally administered immunological therapy on intracerebral brain tumors the authors transplanted 106 gliosarcoma cells into the striatum of treated and control animals. Subcutaneous pumps that released GM-CSF (10 ng/day) and irradiated gliosarcoma cells were placed in the treated animals. The control animals all died within 31 days after intracerebral tumor implantation. In contrast, 40% of the animals receiving GM-CSF—irradiated cell vaccinations survived beyond 300 days. These long-term survivors showed no evidence of gliosarcoma at the injection site on evaluation by magnetic resonance imaging.

Conclusions. These results suggest that the continuous localized delivery of subcutaneous GM-CSF in conjunction with inactivated tumor antigens can initiate a systemic response that leads to the regression of distant peripheral and intracerebral tumors. The success of this treatment illustrates the feasibility of tumor-specific peripheral immunological stimulation after tumor resection to prevent the recurrence of malignant brain tumors.

Free access

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Cover Neurosurgical Focus

A system divided: the state of neurosurgical training in modern-day Vietnam

Walter C. Jean, Trong Huynh, Tuan A. Pham, Hung M. Ngo, Hasan R. Syed, and Daniel R. Felbaum

The current report is the first of its kind in describing the neurosurgical training in modern-day Vietnam. Starting with in-depth face-to-face interviews, followed by electronically distributed questionnaires, a detailed picture of the training systems emerged.

Neurosurgical training in Vietnam is multifaceted and dichotomous. The country of nearly 100 million people currently has only one neurosurgery-specific residency program, at the University of Medicine and Pharmacy at Ho Chi Minh City (UMPHCMC). This program lasts for 3 years, and Westerners might recognize many similarities to programs native to their countries. A similar training program exists in the north, at the Hanoi Medical University, but at this institution, trainees focus on neurosurgery only in the final year of their 3-year training. Neurosurgical training that resembles the program in Hanoi permeates the rest of the country, and the goal for all of the programs is to rapidly produce surgeons who can be dispersed throughout the country to treat patients requiring urgent neurosurgical procedures who are medically unsuitable for transfer to large urban centers and multispecialty hospitals. For the privilege of practicing elective neurosurgery, trainees around the country are required to acquire further training in Ho Chi Minh City or Hanoi or during fellowships abroad.

A clear description of the neurosurgical training systems in Vietnam is hard to achieve, as there exist many diverse pathways and no standard definition of the endpoint for training. Unification and a clearer certification standard will likely help to elevate the standards of training and the state of neurosurgical practice in Vietnam.

Free access

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Cover Neurosurgical Focus

Mixed reality in neurosurgery: redefining the paradigm for arteriovenous malformation planning and navigation to improve patient outcomes

Edinson Najera, Gavin Lockard, Miguel Saez-Alegre, Keaton Piper, and Walter C. Jean

OBJECTIVE

Brain arteriovenous malformations (AVMs) present significant challenges in neurosurgery, requiring detailed planning and execution. In this study, the authors aimed to evaluate the efficacy of mixed reality (MxR), a synergistic application of virtual reality (VR) and augmented reality (AR), in the surgical management of AVMs.

METHODS

A retrospective review was conducted on 10 patients who underwent AVM resection between 2021 and 2023. Preoperative planning used patient-specific 360° VR models, while intraoperative guidance used AR markers for targeted disconnection of arterial feeders. Data were analyzed for surgical duration, blood loss, and postoperative outcomes, stratified by Spetzler-Martin (SM) and supplemented Spetzler-Martin (Supp-SM) grades.

RESULTS

In 10 patients with cerebral AVMs, MxR significantly facilitated the identification of 21 arterial feeders, including challenging deep feeders. MxR-assisted surgeries demonstrated efficient identification and disconnection of arterial feeders, contributing to precise AVM resection. The mean surgical duration was approximately 5 hours 11 minutes, with a mean intraoperative blood loss of 507.5 ml. Statistically significant variations in surgical duration and blood loss were observed based on SM and supplemented Supp-SM grades. Two patients experienced worsened postoperative neurological deficits, underscoring the inherent risks of AVM surgeries. The marked difference in hospital stays between patients with ruptured and those with unruptured AVMs, particularly for SM grade III, highlights the significant impact of rupture status on postoperative recovery.

CONCLUSIONS

In this study, the authors delineated a novel paradigm using MxR for the surgical intervention of AVMs. Using 3D VR for preoperative planning and AR for intraoperative guidance, they achieved unparalleled precision and efficiency in targeting deep arterial feeders. While the results are promising, larger studies are needed to further validate this approach.

Free access

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Cover Neurosurgical Focus

Introduction. Virtual and augmented reality in neurosurgery: a timeline

Walter C. Jean, Gavin W. Britz, Francesco DiMeco, Adrian Elmi-Terander, and Cameron McIntyre

Open access

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Cover Neurosurgical Focus: Video

Feasibility of exoscopic keyhole surgery: case series

Miguel Sáez-Alegre, Christian Ríos-Vicil, Keaton Piper, Edinson Najera, and Walter C. Jean

Keyhole approaches, performed with the endoscope, microscope, or exoscope, aim to minimize tissue traumatization while maximizing surgical view. The exoscope can provide better ergonomics than the microscope without restricting the space inside of the keyhole, as when using the endoscope. However, a frequently quoted reason for intraoperative exoscope-to-microscope conversion is the absence of sufficient light. In this video, the authors present 4 patients who underwent posterior fossa keyhole surgery without intraoperative conversion. The surgical objective was achieved in all patients without associated morbidity. After adequate adaptation, the exoscope allows sufficient light in the surgical field to perform safe keyhole surgery.

The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23116

Free access

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Cover Neurosurgical Focus

A systematic review of endovascular stent-electrode arrays, a minimally invasive approach to brain-machine interfaces

Sauson Soldozy, Steven Young, Jeyan S. Kumar, Stepan Capek, Daniel R. Felbaum, Walter C. Jean, Min S. Park, and Hasan R. Syed

OBJECTIVE

The goal of this study was to systematically review the feasibility and safety of minimally invasive neurovascular approaches to brain-machine interfaces (BMIs).

METHODS

A systematic literature review was performed using the PubMed database for studies published between 1986 and 2019. All studies assessing endovascular neural interfaces were included. Additional studies were selected based on review of references of selected articles and review articles.

RESULTS

Of the 53 total articles identified in the original literature search, 12 studies were ultimately selected. An additional 10 articles were included from other sources, resulting in a total of 22 studies included in this systematic review. This includes primarily preclinical studies comparing endovascular electrode recordings with subdural and epidural electrodes, as well as studies evaluating stent-electrode gauge and material type. In addition, several clinical studies are also included.

CONCLUSIONS

Endovascular stent-electrode arrays provide a minimally invasive approach to BMIs. Stent-electrode placement has been shown to be both efficacious and safe, although further data are necessary to draw comparisons between subdural and epidural electrode measurements given the heterogeneity of the studies included. Greater access to deep-seated brain regions is now more feasible with stent-electrode arrays; however, further validation is needed in large clinical trials to optimize this neural interface. This includes the determination of ideal electrode material type, venous versus arterial approaches, the feasibility of deep brain stimulation, and more streamlined computational decoding techniques.

Free access

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Cover Neurosurgical Focus

Study of comparative surgical exposure to the petroclival region using patient-specific, petroclival meningioma virtual reality models

Walter C. Jean, Yang Yang, Aneil Srivastava, Alexander X. Tai, Aalap Herur-Raman, H. Jeffrey Kim, Da Li, and Zhen Wu

OBJECTIVE

Despite advancement of surgical techniques, the attachments of petroclival meningiomas near the central clival depression (CCD) remain difficult to visualize. With existing methods, the amount of tumor near the CCD that is inaccessible through various approaches cannot be compared. Tumors distort the brainstem, changing the size of the operative corridor for some but not all approaches; therefore, using cadavers with normal posterior fossae makes it impossible to compare different approaches to the tumor. The authors used virtual reality (VR) models created from the imaging data of patients to compare various surgical approaches that have otherwise been incomparable in previous studies.

METHODS

CT and MRI data obtained in 15 patients with petroclival meningiomas were used to create anatomically accurate 3D VR models. For each model, various surgical approaches were performed, and the surgical freedom to 6 targets of the regions were measured. Furthermore, portions of the tumor that were visually blocked by the brainstem or bony structures were segmented and recorded as blinded volumes for comparison.

RESULTS

The extended retrosigmoid approach generated excellent exposure of the petroclival region, but for most specimens, there was inaccessible tumor volume adjacent to the brainstem (mean 641.3 mm3, SE 161.8). In contrast, the brainstem sides of the tumors were well-visualized by all the transpetrosal approaches. The blinded volume of the tumor was largest for the retrolabyrinthine approach, and this was statistically significant compared with all other approaches (mean 2381.3 mm3, SE 185.4).

CONCLUSIONS

The authors performed a novel laboratory study by using patient CT and MRI data to generate 3D virtual models to compare surgical approaches. Since it is impossible to perform various approaches in separate surgeries in patients for comparison, VR represents a viable alternative for such comparative investigations.