A Cadaveric Feasibility Study of the Biportal Endoscopic Transfrontal Sinus Approach: A Minimally Invasive Approach to the Anterior Cranial Fossa.

BACKGROUND AND OBJECTIVES: The trans-sinus transglabellar and bifrontal approaches offer direct access to the anterior cranial fossa. However, these approaches present potential drawbacks. We propose the biportal endoscopic transfrontal sinus (BETS) approach, adapting endoscopic endonasal approach (EEA) techniques for minimally invasive access to the anterior fossa, reducing tissue manipulation, venous sacrifice, and brain retraction. METHODS: Six formalin specimens were used. BETS approach involves 2 incisions over the medial aspect of both eyebrows from the supraorbital notch to the medial end of the eyebrow. A unilateral pedicled pericranial flap is harvested. A craniotomy through the anterior table of the frontal sinus (FS) and a separate craniotomy through the posterior table are performed. Two variants of the approach (preservative vs cranialization) are described for opening and reconstruction of the FS based on the desired pathology to access. Bone flap replacement can be performed with titanium plates and filling of the external table defect with bone cement. RESULTS: Like in EEA, this approach provides access for endoscope and multiple working instruments to be used simultaneously. The approach allows wide access to the anterior cranial fossa, subfrontal, and interhemispheric corridors, all the way up to the suprachiasmatic corridor and through the lamina terminalis to the third ventricle. BETS provides direct access to the anterior fossa, minimizing the level of frontal lobe retraction and providing potentially less tissue disruption and improved cosmesis. Cerebrospinal fluid fistula risk remains one of the major concerns as the narrow corridor limits achieving a watertight closure which can be mitigated with a pedicled flap. Mucocele risk is minimized with full cranialization or reconstruction of the FS. CONCLUSION: The BETS approach is a minimally invasive approach that translates the concepts of EEA to the FS. It allows excellent access to the anterior cranial fossa structures with minimal frontal lobe retraction.

Minimally Invasive Bilateral Duo-Keyhole Approach for Giant Falcine Meningioma: 2 Dimensional Operative Video.

One of the key concepts behind minimally invasive keyhole cranial surgery is that as the operative corridor deepens, it also widens. The corridor should therefore be designed parallel to the long-axis of the tumor to optimize visualization.1 These ideas were applied in a duo-keyhole operation for a falcine meningioma. The patient is a 79-year-old woman diagnosed with a large falcine meningioma compressing both frontal lobes. Her tumor was oriented with the long-axis, perpendicular to the superior sagittal sinus, and has bulbous extensions on both sides of the falx. Incisions on the falx, anterior and posterior to the tumor, in addition to a cut between it and the undersurface of the superior sagittal sinus, would render it practically devascularized and "free-floating.2" One keyhole was insufficient, but one anterior and another posterior to the tumor would make the falcine cuts feasible. The operation was performed with the above scheme and the posterior keyhole to the left and anterior one to the right of midline to facilitate surface vascular detachment on both sides. The patient recovered well and was discharged home after 4 days. This procedure highlights that flexible application of the principles of minimally invasive keyhole. Neurosurgery can tailor-make an operation to precisely fit the unique features of a patient and the tumor. The procedure was performed under the ethical guidelines of our hospital. No Institutional Review Board consent was required or sought because the patient gave specific consent to the procedure and publication of her image.

Extended reality in cranial and spinal neurosurgery - a bibliometric analysis.

PURPOSE: This bibliometric analysis of the top 100 cited articles on extended reality (XR) in neurosurgery aimed to reveal trends in this research field. Gender differences in authorship and global distribution of the most-cited articles were also addressed. METHODS: A Web of Science electronic database search was conducted. The top 100 most-cited articles related to the scope of this review were retrieved and analyzed for trends in publications, journal characteristics, authorship, global distribution, study design, and focus areas. After a brief description of the top 100 publications, a comparative analysis between spinal and cranial publications was performed. RESULTS: From 2005, there was a significant increase in spinal neurosurgery publications with a focus on pedicle screw placement. Most articles were original research studies, with an emphasis on augmented reality (AR). In cranial neurosurgery, there was no notable increase in publications. There was an increase in studies assessing both AR and virtual reality (VR) research, with a notable emphasis on VR compared to AR. Education, surgical skills assessment, and surgical planning were more common themes in cranial studies compared to spinal studies. Female authorship was notably low in both groups, with no significant increase over time. The USA and Canada contributed most of the publications in the research field. CONCLUSIONS: Research regarding the use of XR in neurosurgery increased significantly from 2005. Cranial research focused on VR and resident education while spinal research focused on AR and neuronavigation. Female authorship was underrepresented. North America provides most of the high-impact research in this area.

Feasibility of exoscopic keyhole surgery: case series.

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.

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

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.

Does Head Positioning After Percutaneous Glycerol Rhizotomy for Trigeminal Neuralgia Matter?

BACKGROUND: Percutaneous glycerol rhizotomy (PGR) is a minimally invasive procedure for patients with trigeminal neuralgia who are not candidates for microvascular decompression. PGR has widely varying success rates. It has been postulated that differences in post-injection head positioning might account for the various success rates. METHODS: By comparing glycerol dispersion after injection at various head positions, we provide the first evidence supporting post-injection head flexion positioning. Furthermore, we study the clival-Meckel cave (CMC) angle as a predictor of beneficial glycerol flow, measured on computed tomography images. Twenty-two dissected cadaveric specimens were injected with dyed glycerol through the Hartel approach. The glycerol dispersion was measured at prespecified intervals for 1 hour. The Mann-Whitney U and χ2 tests were used to determine the most ideal angle of head flexion to avoid posterior glycerol dispersion and ensure V1-V3 branch glycerol submersion. RESULTS: We found that 30° of anterior head flexion provided optimal trigeminal nerve glycerol submersion (81.82%) in comparison to neutral (27.27%) and 15° (68.18%), P < 0.001. There was minimal unfavorable dispersion beyond 30 minutes at all angles. More obtuse CMC angles were associated with higher rates of unfavorable BC dispersion (U = 6.0; P = 0.001). For specimens with CMC angles >75°, unfavorable BC dispersion was prevented by head flexion (U = 4.5; P = 0.021). We show that 30° of lateral head tilt achieves V1 submersion in all specimens by 30 minutes [X2(1,N = 44) = 22.759; P < 0.001]. CONCLUSIONS: We found that 30° anterior head flexion for >30 minutes provides ideal conditions for PGR to avoid BC dispersion and ensure V1-V3 branches achieve glycerol submersion. For patients with V1 symptoms, contralateral head flexion might help optimize treatment effects.

The Paramedian Supracerebellar Infratentorial Approach: 2-Dimensional Operative Video.

INDICATIONS: The supracerebellar-infratentorial approach uses the plane between the tentorium and the superior surface of the cerebellum to expose the pineal region. ANATOMIC ESSENTIALS: The bone opening is just underneath the level of the transverse sinus, and so its position must be noted preoperatively. The anatomy of the internal cerebral veins and the veins of Galen and Rosenthal should be examined as well. ESSENTIALS STEPS OF THE PROCEDURE: The sitting position allows gravity-assisted expansion of the supracerebellar corridor, and a paramedian approach provides the biggest working space in the TIGER triangle, delineated by the tentorial surface of the cerebellum, the internal cerebral vein/Galen complex, and the vein of Rosenthal. The veil of arachnoid beyond the triangle must be carefully opened to expose the pineal region. PITFALLS/AVOIDANCE OF COMPLICATIONS: For the sitting position, the operative team must be careful about air emboli. A patent foramen ovale is a contraindication for the position. The deep veins must be handled delicately to avoid complications. VARIANTS AND INDICATIONS FOR THEIR USE: Several variations are shown in this video. For visualization, augmented reality is helpful, but since current augmented reality technology is microscope-based, its use can be ergonomically challenging if the tentorium is steep. 1 Our current preference is to use the exoscope for the major portion of the procedure until most of the tumor is out and then switch to hand-held endoscopes with various angles to finish the operation.The patients consented to the surgery, and all relevant participants consented to publication of their images.

Transorbital Surgical Corridor: An Anatomic Analysis of Ocular Globe Retraction and the Associated Exposure for the Transpalpebral Orbital Rim Preserving Endoscopic Orbitotomy (TORPEDO) Approach.

BACKGROUND AND OBJECTIVES: The transorbital approach varies by the extent of bony removal and the target. Orbital rim-sparing transorbital approach with removal of only the orbit's posterior wall provides optimal cosmetic results, without the need for reconstruction. The size of this corridor, limited by the medial globe retraction, has not yet been defined and is difficult to determine in cadavers because of postmortem tissue desiccation. By using patient-specific models in virtual reality, precise areas and degrees of surgical freedom (AOF and DOF, respectively) provided by globe retraction were calculated. These measurements define a potential maximum safe AOF and DOF, as well as the globe retraction, needed to achieve a sufficient surgical corridor. METHODS: Using a virtual reality system, transorbital rim-preserving craniectomies were performed. The axial and sagittal DOF as well as AOF were calculated lateral to the globe, limited by the orbital rim and globe, with an anterior clinoid target. The DOFs and AOFs were calculated for each degree of medial globe retraction and analyzed using paired t tests. RESULTS: With only 5 mm of retraction, the AOF was 886 mm 2 , while at 10 mm, the AOF was 1546 mm 2 . This increase between 5 and 10 mm allowed for the largest increase in surgical working corridor ( P = .02). At 15 mm of retraction (previously studied point at which intraocular pressure raises), the AOF averaged 2189 mm 2 and axial DOF averaged 23.1°. Eighteen DOF (a previously studied point needed to achieve sufficient working space for 2 instruments) was achieved at 11 mm on average, generating 1675 mm 2 AOF. CONCLUSION: Globe retraction of 11 mm is needed to achieve sufficient DOF for 2 surgical instruments, and 15 mm of retraction is a conservative limit that provides comparable AOFs with similar cranial approaches.

The Inaugural "Century" of Mixed Reality in Cranial Surgery: Virtual Reality Rehearsal/Augmented Reality Guidance and Its Learning Curve in the First 100-Case, Single-Surgeon Series.

BACKGROUND AND OBJECTIVE: Virtual reality (VR) refers to a computer-generated three-dimensional space in which a surgeon can interact with patient-specific anatomic models for surgical planning. Augmented reality (AR) is the technology that places computer-generated objects, including those made in VR, into the surgeon's visual space. Together, VR and AR are called mixed reality (MxR), and it is gaining importance in neurosurgery. MxR is helpful for selecting and creating templates for an optimal surgical approach and identifying key anatomic landmarks intraoperatively. By reporting our experience with the first 100 consecutive cases planned with VR and executed with AR, our objective is to detail the learning curve and encountered obstacles while adopting the new technology. METHODS: This series includes the first 100 consecutive complex cranial cases of a single surgeon for which MxR was intended for use. Effectiveness of the VR rehearsal and AR guidance was analyzed for four specific contributions: (1) opening size, (2) precise craniotomy placement, (3) guidance toward anatomic landmarks or target, and (4) antitarget avoidance. Seventeen cases in the study cohort were matched with historical non-MxR cases for comparison of outcome parameters. The cases in which MxR failed were plotted over time to determine the nature of the "learning curve." RESULTS: AR guidance was abandoned in eight operations because of technical problems, but problem-free application of MxR increased between the 44th and 63rd cases. This provides some evidence of proficiency acquisition in between. Comparing the 17 pairs of matched MxR and non-MxR cases, no statistically significant differences exist in the groups regarding blood loss, length of stay nor duration of surgery. Cases where MxR had above-expectation performances are highlighted. CONCLUSION: MxR is a powerful tool that can help tailor operations to patient-specific anatomy and provide efficient intraoperative guidance without additional time for surgery or hospitalization.

The TIGR triangle of the pineal region: a virtual reality anatomic study.

BACKGROUND: In this morphometric study, we describe the anatomy of the TIGR triangle, which is bordered by the tentorial surface of the cerebellum, the internal cerebral vein and vein of Galen complex, and the vein of Rosenthal. These structures define the window, or deep keyhole, to access the pineal region in non-midline supracerebellar infratentorial approaches. METHODS: The posterior fossa anatomy of 16 patients was studied in virtual reality (VR), and the TIGR triangles were defined and measured with special attention on its angular orientation in the posterior fossa. The angular expanse of the posterior fossa was measured and recorded as the transverse-sigmoid junction (TSJ) angle. Because a perpendicular corridor through an anatomic aperture provides the best exposure, we studied the starting point along the TSJ angle that offers the best exposure of TIGR. RESULTS: In the 31 posterior fossa sides included in the study, the perpendicular trajectory through the TIGR triangle was on average 27.13° CI 95% (range: 5.97°-48.53°) from the midline. When comparing the SCIT variants, both the paramedian and lateral approaches provided near-perpendicular trajectory through the TIGR triangle in a majority of specimens. However, the modified paramedian approach, with starting point defined as TSJ angle/3, provided the most perpendicular path through the TIGR triangle. CONCLUSION: We studied the size, spatial orientation, and morphology of the TIGR triangle. Our data indicated that the best exposure of TIGR is through a modified paramedian SCIT approach, in which the starting point one third of the way from midline to the TSJ.

Anterior Transpetrosal Approach: 2-Dimensional Operative Video.

INDICATIONS CORRIDOR AND LIMITS OF EXPOSURE: The anterior transpetrosal approach uses the subtemporal corridor to access the Meckel cave and the upper petroclival region from the dorsum sellae down to the cerebellopontine angle. ANATOMIC ESSENTIALS NEED FOR PREOPERATIVE PLANNING AND ASSESSMENT: The boundaries of posteromedial triangle of the middle fossa must be adequately visualized for the anterior petrosectomy. They are V3 anteriorly, the petrous ridge medially, GSPN laterally, and the meatal plane posteriorly. ESSENTIALS STEPS OF THE PROCEDURE: The position is supine with the head fully turned. After a temporal craniotomy, the dura is stripped off the floor of the middle fossa. The middle meningeal artery is coagulated and cut, and the greater superficial petrosal nerve is released to allow access to the petrous apex. The extent of the anterior petrosectomy is case-specific, tailored to the exposure needed. The posterior fossa dura is cut where exposed by the petrosectomy and the middle fossa dura just above level of the tentorium and parallel to it. The superior petrosal sinus is ligated and with tentorial incision up to the incisura, the approach is complete. PITFALLS/AVOIDANCE OF COMPLICATIONS: The contents of the petrous temporal bone, such as the cochlea and labyrinthine, and the point of crossing of the carotid artery under V3 must be examined preoperatively to avoid injury during drilling. VARIANTS AND INDICATIONS FOR THEIR USE: The anterior transpetrosal approach can be combined with other approaches to expand surgical access. Two examples of this are included in this video.The patients consented to the surgery and to publication of their images.Image at 0:36 from Kawase T, Toya S, Shiobara R, Mine T, Transpetrosal approach for aneurysm of the lower basilar artery, J Neurosurg , 1981;63(6):857-861, with permission from JNSPG; Image at 1:03 from Jean, Skull Base Surgery: Strategies, edition 1 (9781626239579), with permission from Thieme Publishers.

Middle cerebellar peduncle approach for Nocardia brainstem abscess: illustrative case.

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.

Augmented-reality template guided transorbital approach for intradural tumors.

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.

The Virtual Vision of Neurosurgery: How Augmented Reality and Virtual Reality are Transforming the Neurosurgical Operating Room.

BACKGROUND: In this era of imagination and technological innovation, mixed reality systems such as virtual reality (VR) and augmented reality (AR) are contributing to a wide array of neurosurgical care, from the betterment of surgical planning and surgical comfort to novel treatments and improved resident education. These systems can augment procedures that require high-level dexterity such as minimally invasive surgery and tumor excisions, as well as peripheral and neurovascular surgery. We define and compare the technological features, indications, and characterized outcomes of VR and AR systems in the context of neurosurgery through a review of the literature to date. Moreover, this review discusses the limitations of VR and AR and includes an overview of the cost-effectiveness of each of these systems. METHODS: An extensive review of the literature on AR and VR was performed using PubMed, OVID Medline, and Embase from January 1, 2006 to April 2, 2022. Terms used for the search included AR, spinal surgery, VR, and neurosurgery. RESULTS: The search yielded full-text English language-related articles regarding VR and AR application, limitations, and functional outcomes in neurosurgery. An initial set of 121 studies were screened and reviewed for content. Thirteen studies were included, which involved 162 patients, 550 screw placements, 58 phantom spines, and learning points from simulation training of 276 involved residents. CONCLUSIONS: This literature review examines recent research into VR and AR applications in neurosurgical care. The literature establishes that there are technological features, indications, outcomes, limitations, and cost-effectiveness differences between these systems. Based on ongoing and evolving applications of the VR and AR systems, the innovative potential that they make available to the future of neurosurgical patient care makes clear the need for further studies to understand the nuances between their differing technological advances.