Toward an optimal cadaveric brain model for neurosurgical education: assessment of preservation, parenchyma, vascular injection, and imaging

OBJECTIVE

We assessed types of cadaveric head and brain tissue specimen preparations that are used in a high throughput neurosurgical research laboratory to determine optimal preparation methods for neurosurgical anatomical research, education, and training.

METHODS

Cadaveric specimens (N = 112) prepared using different preservation and vascular injection methods were imaged, dissected, and graded by 11 neurosurgeons using a 21-point scale. We assessed the quality of tissue and preservation in both the anterior and posterior circulations. Tissue quality was evaluated using a 9-point magnetic resonance imaging (MRI) scale.

RESULTS

Formalin-fixed specimens yielded the highest scores for assessment (mean ± SD [17.0 ± 2.8]) vs. formalin-flushed (17.0 ± 3.6) and MRI (6.9 ± 2.0). Cadaver assessment and MRI scores were positively correlated (P < 0.001, R2 0.60). Analysis showed significant associations between cadaver assessment scores and specific variables: nonformalin fixation (β = -3.3), preservation within ≤72 h of death (β = 1.8), and MRI quality score (β = 0.7). Formalin-fixed specimens exhibited greater hardness than formalin-flushed and nonformalin-fixed specimens (P ≤ 0.006). Neurosurgeons preferred formalin-flushed specimens injected with colored latex.

CONCLUSION

For better-quality specimens for neurosurgical education and training, formalin preservation within ≤72 h of death was preferable, as was injection with colored latex. Formalin-flushed specimens more closely resembled live brain parenchyma. Assessment scores were lower for preparation techniques performed > 72 h postmortem and for nonformalin preservation solutions. The positive correlation between cadaver assessment scores and our novel MRI score indicates that donation organizations and institutional buyers should incorporate MRI as a screening tool for the selection of high-quality specimens.

Exosomes in Vascular/Neurological Disorders and the Road Ahead

Neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), stroke, and aneurysms, are characterized by the abnormal accumulation and aggregation of disease-causing proteins in the brain and spinal cord. Recent research suggests that proteins linked to these conditions can be secreted and transferred among cells using exosomes. The transmission of abnormal protein buildup and the gradual degeneration in the brains of impacted individuals might be supported by these exosomes. Furthermore, it has been reported that neuroprotective functions can also be attributed to exosomes in neurodegenerative diseases. The potential neuroprotective functions may play a role in preventing the formation of aggregates and abnormal accumulation of proteins associated with the disease. The present review summarizes the roles of exosomes in neurodegenerative diseases as well as elucidating their therapeutic potential in AD, PD, ALS, HD, stroke, and aneurysms. By elucidating these two aspects of exosomes, valuable insights into potential therapeutic targets for treating neurodegenerative diseases may be provided.

Infragalenic triangle as a gateway to dorsal midbrain and posteromedial thalamic lesions: descriptive and quantitative analysis of microsurgical anatomy

OBJECTIVE

Anatomical triangles provide neurosurgeons with the specificity required to access deep targets, supplementing more general instructions, such as craniotomy and approach. The infragalenic triangle (IGT), bordered by the basal vein of Rosenthal (BVR), precentral cerebellar vein (PCV), and the quadrangular lobule of the cerebellum, is one of a system of anatomical triangles recently introduced to guide dissection to brainstem cavernous malformations and has not been described in detail. This study aimed to quantitatively analyze the anatomical parameters of the IGT and present key nuances for its microsurgical use.

METHODS

A midline supracerebellar infratentorial (SCIT) approach through a torcular craniotomy was performed on 5 cadaveric heads, and the IGT was identified in each specimen bilaterally. Anatomical measurements were obtained with point coordinates collected using neuronavigation. Three cadaveric brains were used to illustrate relevant brainstem anatomy, and 3D virtual modeling was used to simulate various perspectives of the IGT through different approach angles. In addition, 2 illustrative surgical cases are presented.

RESULTS

The longest edge of the IGT was the lateral edge formed by the BVR (mean ± SD length 19.1 ± 2.3 mm), and the shortest edge was the medial edge formed by the PCV (13.9 ± 3.6 mm). The mean surface area of the IGT was 110 ± 34.2 mm2 in the standard exposure. Full expansion of all 3 edges (arachnoid dissection, mobilization, and retraction) resulted in a mean area of 226.0 ± 48.8 mm2 and a 2.5-times increase in surface area exposure of deep structures (e.g., brainstem and thalamus). Thus, almost the entire tectal plate and its relevant safe entry zones can be exposed through an expanded unilateral IGT except for the contralateral inferior colliculus, access to which is usually hindered by PCV tributaries. Exposure of bilateral IGTs may be required to resect larger midline lesions to increase surgical maneuverability or to access the contralateral pulvinar.

CONCLUSIONS

The IGT provides a safe access route to the dorsal midbrain and reliable intraoperative guidance in the deep and complex anatomy of the posterior tentorial incisura. Its potential for expansion makes it a versatile anatomical corridor not only for intrinsic brainstem lesions but also for tumors and vascular malformations of the pineal region, dorsal midbrain, and posteromedial thalamus.

Intraoperative in vivo confocal laser endomicroscopy imaging at glioma margins: can we detect tumor infiltration?

OBJECTIVE

Confocal laser endomicroscopy (CLE) is a US Food and Drug Administration-cleared intraoperative real-time fluorescence-based cellular resolution imaging technology that has been shown to image brain tumor histoarchitecture rapidly in vivo during neuro-oncological surgical procedures. An important goal for successful intraoperative implementation is in vivo use at the margins of infiltrating gliomas. However, CLE use at glioma margins has not been well studied.

METHODS

Matching in vivo CLE images and tissue biopsies acquired at glioma margin regions of interest (ROIs) were collected from 2 institutions. All images were reviewed by 4 neuropathologists experienced in CLE. A scoring system based on the pathological features was implemented to score CLE and H&E images from each ROI on a scale from 0 to 5. Based on the H&E scores, all ROIs were divided into a low tumor probability (LTP) group (scores 0-2) and a high tumor probability (HTP) group (scores 3-5). The concordance between CLE and H&E scores regarding tumor probability was determined. The intraclass correlation coefficient (ICC) and diagnostic performance were calculated.

RESULTS

Fifty-six glioma margin ROIs were included for analysis. Interrater reliability of the scoring system was excellent when used for H&E images (ICC [95% CI] 0.91 [0.86-0.94]) and moderate when used for CLE images (ICC [95% CI] 0.69 [0.40-0.83]). The ICCs (95% CIs) of the LTP group (0.68 [0.40-0.83]) and HTP group (0.68 [0.39-0.83]) did not differ significantly. The concordance between CLE and H&E scores was 61.6%. The sensitivity and specificity values of the scoring system were 79% and 37%. The positive predictive value (PPV) and negative predictive value were 65% and 53%, respectively. Concordance, sensitivity, and PPV were greater in the HTP group than in the LTP group. Specificity was higher in the newly diagnosed group than in the recurrent group.

CONCLUSIONS

CLE may detect tumor infiltration at glioma margins. However, it is not currently dependable, especially in scenarios where low probability of tumor infiltration is expected. The proposed scoring system has excellent intrinsic interrater reliability, but its interrater reliability is only moderate when used with CLE images. These results suggest that this technology requires further exploration as a method for consistent actionable intraoperative guidance with high dependability across the range of tumor margin scenarios. Specific-binding and/or tumor-specific fluorophores, a CLE image atlas, and a consensus guideline for image interpretation may help with the translational utility of CLE.

Mandibular Fossa Approach to Petroclival and Anterior Pontine Lesions

Objective  To describe the anatomy related to a novel approach to the petroclival region through the mandibular fossa for the treatment of petroclival and anterior pontine lesions. Design  Five dry skulls were examined for surgical approach. Three adult cadaveric heads underwent bilateral dissection. One cadaveric head was evaluated with computed tomography after dissection. Setting  This study was performed in an academic medical center. Participants  Neurosurgical anatomy researchers performed this study using dry skulls and cadaveric heads. Main Outcome Measurements  This was a proof-of-concept anatomical study. Results  The mandibular fossa approach uses a vertical preauricular incision above the facial nerve branches. Removal of the temporomandibular joint exposes the mandibular fossa. The anterior boundary is the mandibular nerve at the foramen ovale, and the posterior boundary is the jugular foramen. The chorda tympani, eustachian tube, and tensor tympani muscle are sectioned. The carotid artery is transposed out of the petrous canal, and a petrosectomy is performed from Meckel's cave to the foramen magnum and anterior occipital condyle. Dural opening exposes the anterior pons, vertebrobasilar junction, bilateral vertebral arteries, and the ipsilateral anterior and posterior inferior cerebellar arteries. At completion, the temporomandibular joint is reconstructed with a prosthetic joint utilizing a second incision along the mandible. Conclusions  The mandibular fossa approach is a new trajectory to the petroclival region and the anterior pons. It combines the more anterior angle of endoscopic approaches along with the enhanced control of open approaches. Further study is necessary before this approach is used clinically.

Step-by-Step Dissection of the Extreme Lateral Transodontoid Approach to the Anterior Craniovertebral Junction: Surgical Anatomy and Technical Nuances

BACKGROUND

Multicompartmental lesions of the anterior craniovertebral junction require aggressive management. However, the lesions can be difficult to reach, and the surgical procedure is difficult to understand. The aim of this study was to create a procedural, stepwise microsurgical educational resource for junior trainees to learn the surgical anatomy of the extreme lateral transodontoid approach (ELTOA).

METHODS

Ten formalin-fixed, latex-injected cadaveric heads were dissected under an operative microscope. Dissections were performed under the supervision of a skull base fellowship-trained neurosurgeon who has advanced skull base experience. Key steps of the procedure were documented with a professional camera and a high-definition video system. A relevant clinical case example was reviewed to highlight the principles of the selected approach and its application. The clinical case example also describes a rare complication: a pseudoaneurysm of the vertebral artery.

RESULTS

Key steps of the ELTOA include patient positioning, skin incision, superficial and deep muscle dissection, vertebral artery dissection and transposition, craniotomy, clivus drilling, odontoidectomy, and final extradural and intradural exposure.

CONCLUSIONS

The ELTOA is a challenging approach, but it allows for significant access to the anterior craniovertebral junction, which increases the likelihood of gross total lesion resection. Given the complexity of the approach, substantial training in the dissection laboratory is required to develop the necessary anatomic knowledge and to minimize approach-related morbidity.

Interactive microsurgical anatomy education using photogrammetry 3D models and an augmented reality cube

OBJECTIVE

This study sought to assess the use of an augmented reality (AR) tool for neurosurgical anatomical education.

METHODS

Three-dimensional models were created using advanced photogrammetry and registered onto a handheld AR foam cube imprinted with scannable quick response codes. A perspective analysis of the cube anatomical system was performed by loading a 3D photogrammetry model over a motorized turntable to analyze changes in the surgical window area according to the horizontal rotation. The use of the cube as an intraoperative reference guide for surgical trainees was tested during cadaveric dissection exercises. Neurosurgery trainees from international programs located in Ankara, Turkey; San Salvador, El Salvador; and Moshi, Tanzania, interacted with and assessed the 3D models and AR cube system and then completed a 17-item graded user experience survey.

RESULTS

Seven photogrammetry 3D models were created and imported to the cube. Horizontal turntable rotation of the cube translated to measurable and realistic perspective changes in the surgical window area. The combined 3D models and cube system were used to engage trainees during cadaveric dissections, with satisfactory user experience. Thirty-five individuals (20 from Turkey, 10 from El Salvador, and 5 from Tanzania) agreed that the cube system could enhance the learning experience for neurosurgical anatomy.

CONCLUSIONS

The AR cube combines tactile and visual sensations with high-resolution 3D models of cadaveric dissections. Inexpensive and lightweight, the cube can be effectively implemented to allow independent co-visualization of anatomical dissection and can potentially supplement neurosurgical education.

Arteriovenous malformation with unique drainage through the emissary vein of the foramen ovale: illustrative case

BACKGROUND

As part of the laterotrigeminal venous system (LTVS), the emissary vein of the foramen ovale (EVFO) is an underrecognized venous structure communicating between the cavernous sinus and pterygoid plexus. The sphenobasal sinus is an anatomical variation of the sphenoparietal sinus that drains directly into the EVFO. The authors present the case of a ruptured arteriovenous malformation (AVM) with a unique drainage pattern through the sphenobasal sinus and EVFO.

OBSERVATIONS

A 9-year-old female initially presented with loss of consciousness and was subsequently found to have a ruptured AVM in the left basal frontal area. She underwent an immediate decompressive hemicraniectomy, with a computed tomography angiogram demonstrating a unique anatomical variation in which the sphenobasal sinus communicated with the EVFO and LTVS. The final venous drainage returned to the pterygoid plexus and external jugular vein. Postoperatively, the patient made a substantial recovery, with generalized right-sided weakness remaining as the sole deficit.

LESSONS

The authors present the case of a ruptured AVM with unique venous drainage into the sphenobasal sinus and EVFO, for which the current literature remains limited. As exemplified by this illustrative case, technique modification may be warranted in the setting of this unique anatomical variation to avoid venous sinus injury.

The biportal transorbital approach: quantitative comparison of the anterior subfrontal craniotomy, bilateral transorbital endoscopic, and microscopic approaches

OBJECTIVE

The aim of this study was to assess the surgical use and applicability of a biportal bitransorbital approach. Single-portal transorbital and combined transorbital transnasal approaches have been used in clinical practice, but no study has assessed the surgical use and applicability of a biportal bitransorbital approach.

METHODS

Ten cadaver specimens underwent midline anterior subfrontal (ASub), bilateral transorbital microsurgery (bTMS), and bilateral transorbital neuroendoscopic surgery (bTONES) approaches. Morphometric analyses included the length of the bilateral cranial nerves I and II, the optic tract, and A1; the area of exposure of the anterior cranial fossa floor; craniocaudal and mediolateral angles of attack (AOAs); and volume of surgical freedom (VSF; maximal available working volume for a specific surgical corridor and surgical target structure normalized to a height of 10 mm) of the bilateral paraclinoid internal carotid arteries (ICAs), bilateral terminal ICAs, and anterior communicating artery (ACoA). Analyses were conducted to determine whether the biportal approach was associated with greater instrument freedom.

RESULTS

The bTMS and bTONES approaches provided limited access to the bilateral A1 segments and the ACoA, which were inaccessible in 30% (bTMS) and 60% (bTONES) of exposures. The average total frontal lobe area of exposure (AOE) was 1648.4 mm2 (range 1516.6-1958.8 mm2) for ASub, 1658.9 mm2 (1274.6-1988.2 mm2) for bTMS, and 1914.9 mm2 (1834.2-2014.2 mm2) for bTONES exposures, with no statistically significant superiority between any of the 3 approaches (p = 0.28). The bTMS and bTONES approaches were significantly associated with decreases of 8.7 mm3 normalized volume (p = 0.005) and 14.3 mm3 normalized volume (p < 0.001) for VSF of the right paraclinoid ICA compared with the ASub approach. No statistically significant difference in surgical freedom was noted between all 3 approaches when targeting the bilateral terminal ICA. The bTONES approach was significantly associated with a decrease of 105% in the (log) VSF of the ACoA compared with the ASub (p = 0.009).

CONCLUSIONS

Although the biportal approach is intended to improve maneuverability within these minimally invasive approaches, these results illustrate the pertinent issue of surgical corridor crowding and the importance of surgical trajectory planning. A biportal transorbital approach provides improved visualization but does not improve surgical freedom. Furthermore, although it affords impressive anterior cranial fossa AOE, it is unsuitable for addressing midline lesions because the preserved orbital rim restricts lateral movement. Further comparative studies will elucidate whether a combined transorbital transnasal route is preferable to minimize skull base destruction and maximize instrument access.

Modified Puerto Rico Recurrence Scale for chronic subdural hematomas: augmenting the grading scale with postoperative pneumocephalus volume

BACKGROUND

Chronic subdural hematomas (CSDHs) are common in the elderly, with a relatively high rate of recurrence after initial surgical intervention. Our research team previously created a predictive grading system, the Puerto Rico Recurrence Scale (PRRS), to identify patients at high risk of CSDH recurrence. In this study, we introduce a modification of the (mPRRS) that includes pneumocephalus volume, which has been independently associated with recurrence.

METHODS

A single-center Puerto Rican population-based retrospective study was performed to analyze data for patients treated for CSDH at 1 institution between July 1, 2017, and December 31, 2019. Univariate and multivariate analyses were used to create a grading scale predictive of recurrence. Retrospective validation was conducted for the cohort.

RESULTS

Of 108 patients included in the study, 42 had recurrence, and 66 had nonrecurrence. Postoperative subdural space, postoperative midline shift, and pneumocephalus volume were all higher with recurrence (P = 0.002, P = 0.009, and P < 0.001, respectively). Multivariate analysis was used to create a 6-point grading scale comprising 3 variables (pneumocephalus volume [< 10, 10-20, 21-30, and > 30 cm3], postoperative midline shift [< 0.4, 0.41-1.0, and > 1.0 cm], and laterality [unilateral and bilateral]). Recurrence rates progressively increased in low-risk to high-risk groups (2/18 [11%] vs 21/34 [62%]; P < 0.003).

CONCLUSION

The mPRRS incorporating pneumocephalus measurement improves CSDH recurrence prediction. The mPRRS indicated that patients with higher scores have a greater risk of recurrence and emphasized the importance of measuring postoperative variables for prediction. The mPRRS grading scale for CSDHs may be applicable not only to the Puerto Rican population but also to the general population.

Combined subtarsal contralateral transmaxillary retroeustachian and endoscopic endonasal approaches to the infrapetrous region

OBJECTIVE

The eustachian tube (ET) limits endoscopic endonasal access to the infrapetrous region. Transecting or mobilizing the ET may result in morbidities. This study presents a novel approach in which a subtarsal contralateral transmaxillary (ST-CTM) corridor is coupled with the standard endonasal approach to facilitate access behind the intact ET.

METHODS

Eight cadaveric head specimens were dissected. Endoscopic endonasal approaches (EEAs) (i.e., transpterygoid and inferior transclival) were performed on one side, followed by ST-CTM and sublabial contralateral transmaxillary (SL-CTM) approaches on the opposite side, along with different ET mobilization techniques on the original side. Seven comparative groups were generated. The length of the cranial nerves, areas of exposure, and volume of surgical freedom (VSF) in the infrapetrous regions were measured and compared.

RESULTS

Without ET mobilization, the combined ST-CTM/EEA approach provided greater exposure than EEA alone (mean ± SD 288.9 ± 40.66 mm2 vs 91.7 ± 49.9 mm2; p = 0.001). The VSFs at the ventral jugular foramen (JF), entrance to the petrous internal carotid artery (ICA), and lateral to the parapharyngeal ICA were also greater in ST-CTM/EEA than in EEA alone (p = 0.002, p = 0.002, and p < 0.001, respectively). EEA alone, however, provided greater VSF at the hypoglossal canal (HGC) than did ST-CTM/EEA (p = 0.01). The SL-CTM approach did not increase the EEA exposure (p = 0.48). The ST-CTM/EEA approach provided greater exposure than EEA with extended inferolateral (EIL) or anterolateral (AL) ET mobilization (p = 0.001 and p = 0.02, respectively). The ST-CTM/EEA also increased the VSF lateral to the parapharyngeal ICA in comparison with EEA/EIL ET mobilization (p < 0.001) but not with EEA/AL ET mobilization (p = 0.36). Finally, the VSFs at the HGC and JF were greater in EEA/AL ET mobilization than in ST-CTM/EEA without ET mobilization (p = 0.002 and p = 0.004, respectively).

CONCLUSIONS

Combining the EEA with the more laterally and superiorly originating ST-CTM approach allows greater exposure of the infrapetrous and ventral JF regions while obviating the need for mobilizing the ET. The surgical freedom afforded by the combined approaches is greater than that obtained by EEA alone.

Artery of Uchimura: origin and evolution of identification of the vascular supply to the hippocampus

In 1928, neuroscientist Yushi Uchimura (1897-1980) published a landmark study detailing the hippocampal vasculature. Working in Walther Spielmeyer's Munich laboratory (1925-1927), Uchimura sought evidence for a vascular theory of Ammon's horn sclerosis (AHS). He described an artery supplying the vulnerable sector of the hippocampus, where pathognomonic changes of AHS were noted, and characterized the artery as particularly susceptible to circulatory disturbances. Discovery of this artery led to new concepts and new terminology pertaining to the hippocampus. In addition to having a distinguished career in psychiatry and academia (including a position as University of Tokyo dean), Uchimura was, before attending medical school, one of Japan's best baseball pitchers; he was eventually named Nippon Professional Baseball Organization commissioner and inducted into the Japan Baseball Hall of Fame. Uchimura's description of hippocampal vasculature, which is still subject to debate after nearly a century, brought international attention to AHS and epilepsy and showed the hippocampal vasculature to be variable and vulnerable; important considerations for later neurosurgeons in the development of selective mesial temporal surgery. Prominent figures in neurosurgery have since developed classification systems for the hippocampal vasculature in which the artery of Uchimura remains central. Perhaps no other brain artery has been the nexus for such intense investigation and debate about its association to structure, function, disease, and treatment methodology.

Intraoperative confocal laser endomicroscopy for interpretation of a sellar hemangioblastoma: illustrative case

BACKGROUND

Intraoperative frozen sections play a critical role in surgical strategy because of their ability to provide rapid histopathological information. In cases in which intraoperative biopsy carries a significant risk of bleeding, intraoperative confocal laser endomicroscopy (CLE) can assist in decision-making.

OBSERVATIONS

The authors present a rare case of a large sellar hemangioblastoma. Preoperative radiographic imaging and normal pituitary function suggested a differential diagnosis that included hemangioblastoma. The patient underwent partial preoperative embolization and a right-sided pterional craniotomy for resection of the lesion. Gross intraoperative examination revealed a highly vascular sellar lesion requiring circumferential dissection to minimize blood loss. The serious vascularity precluded intraoperative frozen section analysis, and CLE imaging was performed. CLE imaging provided excellent visualization of the remarkable vascular structure and characteristic histoarchitecture with microvasculature, intracytoplasmic vacuoles, and atypical cells consistent with hemangioblastoma. Resection and decompression of the chiasm was accomplished, and the patient was discharged with improved vision. The final histopathological diagnosis was hemangioblastoma.

LESSONS

When the benefits of obtaining intraoperative frozen sections greatly outweigh the associated risks, CLE imaging can aid in decision-making. CLE imaging offers real-time, on-the-fly evaluation of intraoperative tissue without the need to biopsy a vascular lesion.

Large, Wide-Neck, Side-Wall Aneurysm Treatment in Canines Using NeuroCURE: A Novel Liquid Embolic

BACKGROUND

Untreated intracranial aneurysms can rupture and result in high rates of morbidity and mortality. Although there are numerous approved endovascular aneurysm treatment devices, most require dual anti-platelet therapy, are minimally biocompatible, or are prone to recanalization. Neurovascular Controlled Uniform Rapid Embolic (NeuroCURE) is an innovative polymer gel material with long-term stability, biocompatibility, and hemocompatibility developed for the treatment of large, wide-neck aneurysms.

METHODS

Sidewall aneurysms were surgically created in 10 canines and NeuroCURE was injected through a 0.025 microcatheter under a single balloon inflation period. Aneurysm treatment was angiographically assessed post-embolization and pre-term with Raymond-Roy occlusion classification and a qualitative flow grade scale. Aneurysm neck stability and biocompatibility was histologically assessed to grade platelet/fibrin thrombus, percent endothelialization, and neointimal formation. Aneurysm sac stability was assessed by NeuroCURE sac content, inflammation, and neo-angiogenesis scales.

RESULTS

Explanted aneurysms exhibited a smooth surface at the aneurysm neck with nearly complete neointimal coverage at 3-months. By 6-months, neck endothelialization was 100% in all animals (average Raymond-Roy occlusion classification of 1.2), with no instances of aneurysm recanalization or parent vessel flow compromise. Biocompatibility assessments verified a lack of inflammatory response, neo-angiogenesis, and platelet/fibrin thrombus formation.

CONCLUSION

The NeuroCURE material promotes progressive occlusion of wide-necked side wall aneurysms over time without the need for dual antiplatelet agents. NeuroCURE also promotes neointimal tissue infill without dependence on thrombus formation and thus resists aneurysm recanalization. NeuroCURE remains a compelling investigational device for the treatment of intracranial aneurysms.

Predictors of Outcome in Management of Paediatric Head Trauma in a Tertiary Healthcare Institution in North-Central Nigeria

OBJECTIVE

Trauma is a leading causes of death and disability in all ages. The aim of this study was to describe the demography and characteristics of paediatric head trauma in our institution and examine the predictors of outcome and incidence of injury related mortality.

METHODS

We examined our institutional Trauma Registry over a 2 year period.

RESULTS

A total of 1100 trauma patients were seen over the study period. Of the 579 patients who had head injury 99 were in the paediatric age group. Of the paediatric head trauma patients 79 had documented Glasgow coma score (GCS), 38 (48.1%), 17 (21.5%) and 24 (30.4%) had mild, moderate and severe head injury respectively. The percentage mortality of head injury in the paediatric age group was 6.06% (6/99). There is an association between mortality and GCS (p=0.008), necessity for intensive care unit (ICU) admission (p=0.0001), associated burns (p=0.0001) and complications such as aspiration pneumonia (p=0.0001). The significant predictors of outcome are aspiration (p=0.004), the need for ICU admission (p=0.0001) and associated burns (p=0.005) using logistic binary regression. During the study period 46 children underwent surgical intervention with extradural haematoma 16 (34.8%), depressed skull fracture 14 (30.4%) and chronic subdural haematoma five (10.9%) being the commonest indication for surgeries.

CONCLUSION

Paediatric head injury accounted for 9.0% (99/1100) of all trauma admissions. Majority of patients had mild or moderate injuries. Burns, aspiration pneumonitis and the need for ICU admission were important predictors of outcome in children with traumatic brain injury.

Quantification of motion during microvascular anastomosis simulation using machine learning hand detection

OBJECTIVE

Microanastomosis is one of the most technically demanding and important microsurgical skills for a neurosurgeon. A hand motion detector based on machine learning tracking technology was developed and implemented for performance assessment during microvascular anastomosis simulation.

METHODS

A microanastomosis motion detector was developed using a machine learning model capable of tracking 21 hand landmarks without physical sensors attached to a surgeon's hands. Anastomosis procedures were simulated using synthetic vessels, and hand motion was recorded with a microscope and external camera. Time series analysis was performed to quantify the economy, amplitude, and flow of motion using data science algorithms. Six operators with various levels of technical expertise (2 experts, 2 intermediates, and 2 novices) were compared.

RESULTS

The detector recorded a mean (SD) of 27.6 (1.8) measurements per landmark per second with a 10% mean loss of tracking for both hands. During 600 seconds of simulation, the 4 nonexperts performed 26 bites in total, with a combined excess of motion of 14.3 (15.5) seconds per bite, whereas the 2 experts performed 33 bites (18 and 15 bites) with a mean (SD) combined excess of motion of 2.8 (2.3) seconds per bite for the dominant hand. In 180 seconds, the experts performed 13 bites, with mean (SD) latencies of 22.2 (4.4) and 23.4 (10.1) seconds, whereas the 2 intermediate operators performed a total of 9 bites with mean (SD) latencies of 31.5 (7.1) and 34.4 (22.1) seconds per bite.

CONCLUSIONS

A hand motion detector based on machine learning technology allows the identification of gross and fine movements performed during microanastomosis. Economy, amplitude, and flow of motion were measured using time series data analysis. Technical expertise could be inferred from such quantitative performance analysis.

5-aminolevulinic acid, fluorescein sodium, and indocyanine green for glioma margin detection: analysis of operating wide-field and confocal microscopy in glioma models of various grades

Introduction

Surgical resection remains the first-line treatment for gliomas. Several fluorescent dyes are currently in use to augment intraoperative tumor visualization, but information on their comparative effectiveness is lacking. We performed systematic assessment of fluorescein sodium (FNa), 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX), and indocyanine green (ICG) fluorescence in various glioma models using advanced fluorescence imaging techniques.

Methods

Four glioma models were used: GL261 (high-grade model), GB3 (low-grade model), and an in utero electroporation model with and without red fluorescence protein (IUE +RFP and IUE -RFP, respectively) (intermediate-to-low-grade model). Animals underwent 5-ALA, FNa, and ICG injections and craniectomy. Brain tissue samples underwent fluorescent imaging using a wide-field operative microscope and a benchtop confocal microscope and were submitted for histologic analysis.

Results

Our systematic analysis showed that wide-field imaging of highly malignant gliomas is equally efficient with 5-ALA, FNa, and ICG, although FNa is associated with more false-positive staining of the normal brain. In low-grade gliomas, wide-field imaging cannot detect ICG staining, can detect FNa in only 50% of specimens, and is not sensitive enough for PpIX detection. With confocal imaging of low-intermediate grade glioma models, PpIX outperformed FNa.

Discussion

Overall, compared to wide-field imaging, confocal microscopy significantly improved diagnostic accuracy and was better at detecting low concentrations of PpIX and FNa, resulting in improved tumor delineation. Neither PpIX, FNa, nor ICG delineated all tumor boundaries in studied tumor models, which emphasizes the need for novel visualization technologies and molecular probes to guide glioma resection. Simultaneous administration of 5-ALA and FNa with use of cellular-resolution imaging modalities may provide additional information for margin detection and may facilitate maximal glioma resection.

Liquid Embolic Agents for Endovascular Embolization: A Review

Endovascular embolization (EE) has been used for the treatment of blood vessel abnormalities, including aneurysms, AVMs, tumors, etc. The aim of this process is to occlude the affected vessel using biocompatible embolic agents. Two types of embolic agents, solid and liquid, are used for endovascular embolization. Liquid embolic agents are usually injectable and delivered into the vascular malformation sites using a catheter guided by X-ray imaging (i.e., angiography). After injection, the liquid embolic agent transforms into a solid implant in situ based on a variety of mechanisms, including polymerization, precipitation, and cross-linking, through ionic or thermal process. Until now, several polymers have been designed successfully for the development of liquid embolic agents. Both natural and synthetic polymers have been used for this purpose. In this review, we discuss embolization procedures with liquid embolic agents in different clinical applications, as well as in pre-clinical research studies.

Three-Dimensional Modeling and Extended Reality Simulations of the Cross-Sectional Anatomy of the Cerebrum, Cerebellum, and Brainstem

BACKGROUND

Understanding the anatomy of the human cerebrum, cerebellum, and brainstem and their 3-dimensional (3D) relationships is critical for neurosurgery. Although 3D photogrammetric models of cadaver brains and 2-dimensional images of postmortem brain slices are available, neurosurgeons lack free access to 3D models of cross-sectional anatomy of the cerebrum, cerebellum, and brainstem that can be simulated in both augmented reality (AR) and virtual reality (VR).

OBJECTIVE

To create 3D models and AR/VR simulations from 2-dimensional images of cross-sectionally dissected cadaveric specimens of the cerebrum, cerebellum, and brainstem.

METHODS

The Klingler method was used to prepare 3 cadaveric specimens for dissection in the axial, sagittal, and coronal planes. A series of 3D models and AR/VR simulations were then created using 360° photogrammetry.

RESULTS

High-resolution 3D models of cross-sectional anatomy of the cerebrum, cerebellum, and brainstem were obtained and used in creating AR/VR simulations. Eleven axial, 9 sagittal, and 7 coronal 3D models were created. The sections were planned to show important deep anatomic structures. These models can be freely rotated, projected onto any surface, viewed from all angles, and examined at various magnifications.

CONCLUSION

To our knowledge, this detailed study is the first to combine up-to-date technologies (photogrammetry, AR, and VR) for high-resolution 3D visualization of the cross-sectional anatomy of the entire human cerebrum, cerebellum, and brainstem. The resulting 3D images are freely available for use by medical professionals and students for better comprehension of the 3D relationship of the deep and superficial brain anatomy.

Anatomic Depth Estimation and 3-Dimensional Reconstruction of Microsurgical Anatomy Using Monoscopic High-Definition Photogrammetry and Machine Learning

BACKGROUND

Immersive anatomic environments offer an alternative when anatomic laboratory access is limited, but current three-dimensional (3D) renderings are not able to simulate the anatomic detail and surgical perspectives needed for microsurgical education.

OBJECTIVE

To perform a proof-of-concept study of a novel photogrammetry 3D reconstruction technique, converting high-definition (monoscopic) microsurgical images into a navigable, interactive, immersive anatomy simulation.

METHODS

Images were acquired from cadaveric dissections and from an open-access comprehensive online microsurgical anatomic image database. A pretrained neural network capable of depth estimation from a single image was used to create depth maps (pixelated images containing distance information that could be used for spatial reprojection and 3D rendering). Virtual reality (VR) experience was assessed using a VR headset, and augmented reality was assessed using a quick response code-based application and a tablet camera.

RESULTS

Significant correlation was found between processed image depth estimations and neuronavigation-defined coordinates at different levels of magnification. Immersive anatomic models were created from dissection images captured in the authors' laboratory and from images retrieved from the Rhoton Collection. Interactive visualization and magnification allowed multiple perspectives for an enhanced experience in VR. The quick response code offered a convenient method for importing anatomic models into the real world for rehearsal and for comparing other anatomic preparations side by side.

CONCLUSION

This proof-of-concept study validated the use of machine learning to render 3D reconstructions from 2-dimensional microsurgical images through depth estimation. This spatial information can be used to develop convenient, realistic, and immersive anatomy image models.

Virtual neurosurgery anatomy laboratory: A collaborative and remote education experience in the metaverse

Background:

Advances in computer sciences, including novel 3-dimensional rendering techniques, have enabled the creation of cloud-based virtual reality (VR) interfaces, making real-time peer-to-peer interaction possible even from remote locations. This study addresses the potential use of this technology for microsurgery anatomy education.

Methods:

Digital specimens were created using multiple photogrammetry techniques and imported into a virtual simulated neuroanatomy dissection laboratory. A VR educational program using a multiuser virtual anatomy laboratory experience was developed. Internal validation was performed by five multinational neurosurgery visiting scholars testing and assessing the digital VR models. For external validation, 20 neurosurgery residents tested and assessed the same models and virtual space.

Results:

Each participant responded to 14 statements assessing the virtual models, categorized under realism (n = 3), usefulness (n = 2), practicality (n = 3), enjoyment (n = 3), and recommendation (n = 3). Most responses expressed agreement or strong agreement with the assessment statements (internal validation, 94% [66/70] total responses; external validation, 91.4% [256/280] total responses). Notably, most participants strongly agreed that this system should be part of neurosurgery residency training and that virtual cadaver courses through this platform could be effective for education.

Conclusion:

Cloud-based VR interfaces are a novel resource for neurosurgery education. Interactive and remote collaboration between instructors and trainees is possible in virtual environments using volumetric models created with photogrammetry. We believe that this technology could be part of a hybrid anatomy curriculum for neurosurgery education. More studies are needed to assess the educational value of this type of innovative educational resource.

Seven bypasses simulation set: description and validity assessment of novel models for microneurosurgical training

OBJECTIVE

Microsurgical training remains indispensable to master cerebrovascular bypass procedures, but simulation models for training that accurately replicate microanastomosis in narrow, deep-operating corridors are lacking. Seven simulation bypass scenarios were developed that included head models in various surgical positions with premade approaches, simulating the restrictions of the surgical corridors and hand positions for microvascular bypass training. This study describes these models and assesses their validity.

METHODS

Simulation models were created using 3D printing of the skull with a designed craniotomy. Brain and external soft tissues were cast using a silicone molding technique from the clay-sculptured prototypes. The 7 simulation scenarios included: 1) temporal craniotomy for a superficial temporal artery (STA)-middle cerebral artery (MCA) bypass using the M4 branch of the MCA; 2) pterional craniotomy and transsylvian approach for STA-M2 bypass; 3) bifrontal craniotomy and interhemispheric approach for side-to-side bypass using the A3 branches of the anterior cerebral artery; 4) far lateral craniotomy and transcerebellomedullary approach for a posterior inferior cerebellar artery (PICA)-PICA bypass or 5) PICA reanastomosis; 6) orbitozygomatic craniotomy and transsylvian-subtemporal approach for a posterior cerebral artery bypass; and 7) extended retrosigmoid craniotomy and transcerebellopontine approach for an occipital artery-anterior inferior cerebellar artery bypass. Experienced neurosurgeons evaluated each model by practicing the aforementioned bypasses on the models. Face and content validities were assessed using the bypass participant survey.

RESULTS

A workflow for model production was developed, and these models were used during microsurgical courses at 2 neurosurgical institutions. Each model is accompanied by a corresponding prototypical case and surgical video, creating a simulation scenario. Seven experienced cerebrovascular neurosurgeons practiced microvascular anastomoses on each of the models and completed surveys. They reported that actual anastomosis within a specific approach was well replicated by the models, and difficulty was comparable to that for real surgery, which confirms the face validity of the models. All experts stated that practice using these models may improve bypass technique, instrument handling, and surgical technique when applied to patients, confirming the content validity of the models.

CONCLUSIONS

The 7 bypasses simulation set includes novel models that effectively simulate surgical scenarios of a bypass within distinct deep anatomical corridors, as well as hand and operator positions. These models use artificial materials, are reusable, and can be implemented for personal training and during microsurgical courses.

Intraoperative confocal laser endomicroscopy: prospective in vivo feasibility study of a clinical-grade system for brain tumors

OBJECTIVE

The authors evaluated the feasibility of using the first clinical-grade confocal laser endomicroscopy (CLE) system using fluorescein sodium for intraoperative in vivo imaging of brain tumors.

METHODS

A CLE system cleared by the FDA was used in 30 prospectively enrolled patients with 31 brain tumors (13 gliomas, 5 meningiomas, 6 other primary tumors, 3 metastases, and 4 reactive brain tissue). A neuropathologist classified CLE images as interpretable or noninterpretable. Images were compared with corresponding frozen and permanent histology sections, with image correlation to biopsy location using neuronavigation. The specificities and sensitivities of CLE images and frozen sections were calculated using permanent histological sections as the standard for comparison. A recently developed surgical telepathology software platform was used in 11 cases to provide real-time intraoperative consultation with a neuropathologist.

RESULTS

Overall, 10,713 CLE images from 335 regions of interest were acquired. The mean duration of the use of the CLE system was 7 minutes (range 3-18 minutes). Interpretable CLE images were obtained in all cases. The first interpretable image was acquired within a mean of 6 (SD 10) images and within the first 5 (SD 13) seconds of imaging; 4896 images (46%) were interpretable. Interpretable image acquisition was positively correlated with study progression, number of cases per surgeon, cumulative length of CLE time, and CLE time per case (p ≤ 0.01). The diagnostic accuracy, sensitivity, and specificity of CLE compared with frozen sections were 94%, 94%, and 100%, respectively, and the diagnostic accuracy, sensitivity, and specificity of CLE compared with permanent histological sections were 92%, 90%, and 94%, respectively. No difference was observed between lesion types for the time to first interpretable image (p = 0.35). Deeply located lesions were associated with a higher percentage of interpretable images than superficial lesions (p = 0.02). The study met the primary end points, confirming the safety and feasibility and acquisition of noninvasive digital biopsies in all cases. The study met the secondary end points for the duration of CLE use necessary to obtain interpretable images. A neuropathologist could interpret the CLE images in 29 (97%) of 30 cases.

CONCLUSIONS

The clinical-grade CLE system allows in vivo, intraoperative, high-resolution cellular visualization of tissue microstructure and identification of lesional tissue patterns in real time, without the need for tissue preparation.

Improving the metric of surgical freedom in the laboratory based on a novel concept of volume

BACKGROUND

In laboratory-based neuroanatomical studies, surgical freedom, the most important metric of instrument maneuverability, has been based on Heron's formula. Inaccuracies and limitations hinder this study design's applicability. A new methodology, volume of surgical freedom (VSF), may produce a more realistic qualitative and quantitative representation of a surgical corridor.

METHODS

Overall, 297 data set measurements assessing surgical freedom were completed for cadaveric brain neurosurgical approach dissections. Heron's formula and VSF were calculated specifically to different surgical anatomical targets. Quantitative accuracy and the results of an analysis of human error were compared.

RESULTS

Heron's formula for irregularly shaped surgical corridors resulted in overestimation of the respective areas (minimum overestimation 31.3%). In 92% (188/204) of data sets reviewed for influence of offset, areas calculated on the basis of measured data points were larger than areas calculated on the basis of the translated best-fit plane points (mean [SD] overestimation of 2.14% [2.62%]). Variability in the probe length attributable to human error was small (mean [SD] calculated probe length 190.26 mm [5.57 mm]).

CONCLUSIONS

VSF is an innovative concept that can develop a model of a surgical corridor producing better assessment and prediction of the ability to maneuver and manipulate surgical instruments. VSF corrects for deficits in Heron's method by generating the correct area for an irregular shape using the shoelace formula, adjusting the data points to account for offset, and attempting to correct for human error. VSF produces 3-dimensional models and, therefore, is a preferable standard for assessing surgical freedom.

Comprehensive microsurgical anatomy of the middle cranial fossa: Part II-neurovascular anatomy

In order to master the surgical approaches to the middle cranial fossa, the surgeon needs to understand the relevant bony anatomy. However, she/he also needs to have a clear and sound understanding of the neural and vascular anatomy because, oftentimes, the osseous anatomy (except for the optic apparatus) should be removed to expose and protect the neurovascular anatomy. This is the second of a two-part article discussing the neurovascular anatomy of the middle cranial fossa. A brief discussion of the surgical approaches follows.

Comprehensive microsurgical anatomy of the middle cranial fossa: Part I-Osseous and meningeal anatomy

The middle cranial fossa is one of the most complex regions in neurosurgery and otolaryngology-in fact, the practice of skull base surgery originated from the need to treat pathologies in this region. Additionally, great neurosurgeons of our present and past are remembered for their unique methods of treating diseases in the middle fossa. The following article reviews the surgical anatomy of the middle fossa. The review is divided into the anatomy of the bones, dura, vasculature, and nerves-in two parts. Emphasis is paid to their neurosurgical significance and applications in skull base surgery. Part I focuses on the bony and dural anatomy.

Nervus intermedius: Microsurgical and anatomic relationships to the cerebellopontine angle neurovascular complex

Background

The nervus intermedius (NI) comprises fibers originating from the trigeminal, superior salivary, and solitary tract nuclei, which join the facial nerve (cranial nerve [CN] VII). Neighboring structures include the vestibulocochlear nerve (CN VIII), the anterior inferior cerebellar artery (AICA), and its branches. Microsurgical procedures at the cerebellopontine angle (CPA) benefit from understanding NI anatomy and relationships, especially for the microsurgical treatment of geniculate neuralgia, where the NI is transected. This study sought to characterize common relationships between the NI rootlets, CN VII, CN VIII, and the meatal loop of AICA at the internal auditory canal (IAC).

Methods

Seventeen cadaveric heads underwent retrosigmoid craniectomy. Following complete unroofing of the IAC, the NI rootlets were individually exposed to identify their origins and insertion points. The AICA and its meatal loop were traced to assess their relationship with the NI rootlets.

Results

Thirty-three NIs were identified. The median number of NI rootlets was 4 per NI (interquartile range, 3-5). The rootlets mainly originated from the proximal premeatal segment of CN VIII (81 of 141, 57%) and inserted onto CN VII at the IAC fundus (89 of 141, 63%). When crossing the acoustic-facial bundle, the AICA most frequently passed between the NI and CN VIII (14 of 33, 42%). Five composite patterns of neurovascular relationships were identified regarding NI.

Conclusion

Although certain anatomical trends can be identified, the NI has a variable relationship with the adjacent neurovascular complex at the IAC. Therefore, anatomical relationships should not be used as the sole method of NI identification during CPA surgery.

Toward "bigger" data for neurosurgical anatomical research: a single centralized quantitative neurosurgical anatomy platform

Quantitative neurosurgical anatomy research aims to produce surgically applicable knowledge for improving operative decision-making using measurements from anatomical dissection and tools such as stereotaxis. Although such studies attempt to answer similar research questions, there is little standardization between them, offering minimal comparability. Modern technology has been incorporated into the research methodology, but many scientific principles are lacking, and results are not broadly applicable or suitable for evaluating big-data trends. Advances in information technology and the concept of big data permit more accessible and robust means of producing valuable, standardized, reliable research. A technology project, "Inchin," is presented to address these needs for neurosurgical anatomy research. This study applies the concept of big data to neurosurgical anatomy research, specifically in quantifying surgical metrics. A remote-hosted web application was developed for computing standard neurosurgical metrics and storing measurement data. An online portal (Inchin) was developed to produce a database to facilitate and promote neurosurgical anatomical research, applying optimal scientific methodology and big-data principles to this recent and evolving field of research. Individual data sets are not insignificant, but a collective of data sets present advantages. Large data sets allow confidence in data trends that are usually obscured in smaller numbers of samples. Inchin, a single centralized software platform, can act as a global database of results of neurosurgical anatomy studies. A calculation tool ensuring standardized peer-reviewed methodology, Inchin is applied to the analysis of neurosurgical metrics and may promote efficient study collaboration within and among neurosurgical laboratories.

Complement C3a Receptor (C3aR) Mediates Vascular Dysfunction, Hippocampal Pathology, and Cognitive Impairment in a Mouse Model of VCID

Vascular contributions to cognitive impairment and dementia (VCID) secondary to chronic mild-moderate cerebral ischemia underlie a significant percentage of cases of dementia. We previously reported that either genetic deficiency of the complement C3a receptor (C3aR) or its pharmacological inhibition protects against cerebral ischemia in rodents, while others have implicated C3aR in the pathogenesis seen in rodent transgenic models of Alzheimer's disease. In the present study, we evaluated the role of complement C3a-C3aR signaling in the onset and progression of VCID. We utilized the bilateral common carotid artery stenosis (BCAS) model to induce VCID in male C57BL/6 wild-type and C3aR-knockout (C3aR-/-) mice. Cerebral blood flow (CBF) changes, hippocampal atrophy (HA), white matter degeneration (WMD), and ventricular size were assessed at 4 months post-BCAS using laser speckle contrast analysis (LSCI) and magnetic resonance imaging (MRI). Cognitive function was evaluated using the Morris water maze (MWM), and novel object recognition (NOR), immunostaining, and western blot were performed to assess the effect of genetic C3aR deletion on post-VCID outcomes. BCAS resulted in decreased CBF and increased HA, WMD, and neurovascular inflammation in WT (C57BL/6) compared to C3aR-/- (C3aR-KO) mice. Moreover, C3aR-/- mice exhibited improved cognitive function on NOR and MWM relative to WT controls. We conclude that over-activation of the C3a/C3aR axis exacerbates neurovascular inflammation leading to poor VCID outcomes which are mitigated by C3aR deletion. Future studies are warranted to dissect the role of cell-specific C3aR in VCID.

P13.05.A Image annotation guideline for invivo confocal laser endomicroscopy, interrater reliability and how to learn from medical consensus for machine learning algorithms

Background

Intraoperative confocal laser endomicroscopy (CLE) is an in vivo imaging technique increasingly studied in neurosurgery and neuropathology. It can be affected by artifacts introduced by the CLE device or related to the intraoperative setting. We developed and evaluated an image annotation guideline (AGL) to detect and eliminate images bearing no valuable information as a result of such artifacts. Images ware classified into good and bad quality, based on defined technical criteria, which are also considered relevant by clinical experts.

Material and Methods

Datasets were created from intraoperative CLE in vivo specimens of patients resected for brain tumors. The process from data collection to development of the ML algorithm followed 7 steps: data quality specification, image and metadata collection, AGL development, annotation, data allocation for clinical validation, clinical validation, and, optionally, algorithm development. Final diagnoses were obtained by pathological analysis. Artifacts were grouped into three categories: diminished signal-to-noise-ratio (dSNR), optical distortions (movement/perturbations), and contrast/brightness artifacts. Images were annotated by 4 medical data annotators (T4). For clinical validation, 500 images were excluded from the training data and additionally annotated by 3 board certified neuropathologists (NPs 1-3) with experience in CLE imaging, to determine the medical consensus on good and bad images. All raters (NPs) were compared against each other and against T4; T4 was also compared against the medical consensus. Cohen’s Kappa and overall percentage agreement (OPA) were used to evaluate inter-rater reliability. Positive percent agreement (PPA) and negative percentage agreement (NPA) were also used to evaluate agreement between medical consensus and T4.

Results

21,616 CLE images and corresponding clinical metadata were collected from 94 patients and annotated. For each case between 27 and 815 CLE images were acquired over the course of the surgery (mean=175 images per case, SD=170.6). 11% and 13% of images were labeled as dSNR and distortion, respectively, and 34% as class contrast. 42% of the images represented the good quality images. Interrater agreement between the 3 NPs ranged between 0.30 and 0.59. Agreement between T4 and the medical consensus was substantial (Cohen’s Kappa &gt;=0.61). OPA between T4 and the medical consensus was 80.60%, PPA 72.34% and NPA 87.92%.

Conclusion

Annotations according to a well-structured and expertly curated AGL show higher values for Cohen’s Kappa and Overall Percent Agreement (OPA) with the medical consensus, than that of individual experts among one another. Such an AGL can be considered appropriate and produces on par results with annotations by a group of experts in the field and can be further employed for training machine learning (ML) algorithms.

Introduction of In Vivo Confocal Laser Endomicroscopy and Real-Time Telepathology for Remote Intraoperative Neurosurgery-Pathology Consultation

BACKGROUND

Precise communication between neurosurgeons and pathologists is crucial for optimizing patient care, especially for intraoperative diagnoses. Confocal laser endomicroscopy (CLE) combined with a telepathology software platform (TSP) provides a novel venue for neurosurgeons and pathologists to review CLE images and converse intraoperatively in real-time.

OBJECTIVE

To describe the feasibility of integrating CLE and a TSP in the surgical workflow for real-time review of in vivo digital fluorescence tissue imaging in 3 patients with intracranial tumors.

METHODS

Although the neurosurgeon used the CLE probe to generate fluorescence images of histoarchitecture within the operative field that were displayed on monitors in the operating room, the pathologist simultaneously remotely viewed the CLE images. The neurosurgeon and pathologist discussed in real-time the histological structures of intraoperative imaging locations.

RESULTS

The neurosurgeon placed the CLE probe at various locations on and around the tumor, in the surgical resection bed, and on surrounding brain tissue with communication through the TSP. The neurosurgeon oriented the pathologist to the location of the CLE, and the pathologist and neurosurgeon discussed the CLE images in real-time. The TSP and CLE were integrated successfully and rapidly in the operating room in all 3 cases. No patient had perioperative complications.

CONCLUSION

Two novel digital neurosurgical cellular imaging technologies were combined with intraoperative neurosurgeon-pathologist communication to guide the identification of abnormal histoarchitectural tissue features in real-time. CLE with the TSP may allow rapid decision-making during tumor resection that may hold significant advantages over the frozen section process and surgical workflow in general.

Management of injuries on the 16th-century battlefield: Ambroise Paré’s contributions to neurosurgery and functional recovery

During the 1536 siege of Turin in northern Italy, a young French barber-surgeon abandoned the conventional treatment of battle-inflicted wounds, launching a revolution in military medicine and surgical techniques. Ambroise Paré (1510–1590) was born into a working-class Huguenot family in Laval, France, during an era when surgery was not considered a respectable profession. He rose from humble origins as a barber-surgeon, a low-ranked occupation in the French medical hierarchy, to become a royal surgeon (chirurgien ordinaire du Roi) serving 4 consecutive French monarchs. His innovative ideas and surgical practice were a response to the environment created by new military technology on 16th-century European battlefields. Gunpowder weapons caused unfamiliar, complicated injuries that challenged Paré to develop new techniques and surgical instruments. Although Paré’s contributions to the treatment of wounds and functional prosthetics are documented, a deeper appreciation of his role in military neurosurgery is needed. This paper examines archives, primary texts, and written accounts by Paré that reveal specific patient cases highlighting his innovative contributions to neurotrauma and neurosurgery during demanding and harrowing circumstances, on and off the battlefield, in 16th-century France. Notably, trepanation indications increased because of battlefield head injuries, and Paré frequently described this technique and improved the design of the trepan tool. His contribution to neurologically related topics is extensive; there are more chapters devoted to the nervous system than to any other organ system in his compendium, Oeuvres. Regarding anatomical knowledge as fundamentally important and admiring the contemporary contributions of Andreas Vesalius, Paré reproduced many images from Vesalius’ works at his own great expense. The manner in which Paré’s participation in military expeditions enabled collaboration with multidisciplinary artisans on devices, including surgical tools and prosthetics, to restore neurologically associated functionality is also discussed. Deeply religious, in a life filled with adventure, and serving in often horrendous conditions during a time when Galenic dogma still dominated medical practice, Paré developed a reputation for logic, empiricism, technology, and careful treatment. "I have [had] the opportunity to praise God, for what he called me to do in medical operation, which is commonly called surgery, which could not be bought with gold or silver, but by only virtue and great experimentation."

Quantitative Anatomic Comparison of the Extreme Lateral Transodontoid vs Extreme Medial Endoscopic Endonasal Approaches to the Jugular Foramen and Craniovertebral Junction

BACKGROUND

Large, destructive intracranial and extracranial lesions at the jugular foramen (JF) and anterior craniovertebral junction (CVJ) are among the most challenging lesions to resect.

OBJECTIVE

To compare the extreme lateral transodontoid approach (ELTOA) with the extreme medial endoscopic endonasal approach (EMEEA) to determine the most effective surgical approach to the JF and CVJ.

METHODS

Seven formalin-fixed cadaveric heads were dissected. Using neuronavigation, we quantitatively measured and compared the exposure of the intracranial and extracranial neurovascular structures, the drilled area of the clivus and the C1 vertebra, and the area of exposure of the brainstem.

RESULTS

The mean total drilled area of the clivus was greater with the EMEEA than with the ELTOA (1043.5 vs 909.4 mm2, P = .02). The EMEEA provided a longer exposure of the extracranial cranial nerves (CNs) IX, X, and XI compared with the ELTOA (cranial nerve [CN] IX: 18.8 vs 12.0 mm, P = .01; CN X: 19.2 vs 10.4 mm, P = .003; and CN XI, 18.1 vs 11.9 mm, P = .04). The EMEEA, compared with the ELTOA, provided a significantly greater area of exposure of the contralateral ventromedial medulla (289.5 vs 80.9 mm2, P < .001) and pons (237.5 vs 86.2 mm2, P = .005) but less area of exposure of the ipsilateral dorsolateral medulla (51.5 vs 205.8 mm2, P = .008).

CONCLUSION

The EMEEA and ELTOA provide optimal exposures to different aspects of the CVJ and JF. A combination of these approaches can compensate for their disadvantages and achieve significant exposure.

Characterization of ex vivo and in vivo intraoperative neurosurgical confocal laser endomicroscopy imaging

Background

The new US Food and Drug Administration-cleared fluorescein sodium (FNa)-based confocal laser endomicroscopy (CLE) imaging system allows for intraoperative on-the-fly cellular level imaging. Two feasibility studies have been completed with intraoperative use of this CLE system in ex vivo and in vivo modalities. This study quantitatively compares the image quality and diagnostic performance of ex vivo and in vivo CLE imaging.

Methods

Images acquired from two prospective CLE clinical studies, one ex vivo and one in vivo, were analyzed quantitatively. Two image quality parameters – brightness and contrast – were measured using Fiji software and compared between ex vivo and in vivo images for imaging timing from FNa dose and in glioma, meningioma, and intracranial metastatic tumor cases. The diagnostic performance of the two studies was compared.

Results

Overall, the in vivo images have higher brightness and contrast than the ex vivo images (p < 0.001). A weak negative correlation exists between image quality and timing of imaging after FNa dose for the ex vivo images, but not the in vivo images. In vivo images have higher image quality than ex vivo images (p < 0.001) in glioma, meningioma, and intracranial metastatic tumor cases. In vivo imaging yielded higher sensitivity and negative predictive value than ex vivo imaging.

Conclusions

In our setting, in vivo CLE optical biopsy outperforms ex vivo CLE by producing higher quality images and less image deterioration, leading to better diagnostic performance. These results support the in vivo modality as the modality of choice for intraoperative CLE imaging.

Multiple hippocampal transection for mesial temporal lobe epilepsy: A systematic review

PURPOSE

Multiple hippocampal transection (MHT) is a surgical technique that offers adequate seizure control with minimal perioperative morbidity. However, there is little evidence available to guide neurosurgeons in selecting this technique for use in appropriate patients. This systematic review analyzes patient-level data associated with MHT for intractable epilepsy, focusing on postoperative seizure control and memory outcomes.

METHODS

The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant articles were identified from 3 databases (PubMed, Medline, Embase) up to August 1, 2021. Inclusion criteria were that the majority of patients had received a diagnosis of intractable epilepsy, the article was written in English, MHT was the primary procedure, and patient-level metadata were included.

RESULTS

Fifty-nine unique patients who underwent MHT were identified across 11 studies. Ten (17%) of 59 patients underwent MHT alone. Forty-three (75%) of 57 patients who had a follow-up 12 months or longer were seizure free at last follow-up. With respect to postoperative verbal memory retention, 9 of 38 (24%) patient test scores did not change, 14 (37%) decreased, and 16 (42%) increased. With respect to postoperative nonverbal memory retention, 12 of 38 (34%) patient test scores did not change, 13 (34%) decreased, and 13 (33%) increased.

CONCLUSION

There are few reported patients analyzed after MHT. Although the neurocognitive benefits of MHT are unproven, this relatively novel technique has shown promise in the management of seizures in patients with intractable epilepsy. However, structured trials assessing MHT in isolation are warranted.

Analyzing international medical graduate research productivity for application to US neurosurgery residency and beyond: A survey of applicants, program directors, and institutional experience

Background

The authors investigated perceived discrepancies between the neurosurgical research productivity of international medical graduates (IMGs) and US medical graduates (USMGs) through the perspective of program directors (PDs) and successfully matched IMGs.

Methods

Responses to 2 separate surveys on neurosurgical applicant research productivity in 115 neurosurgical programs and their PDs were analyzed. Neurosurgical research participation was analyzed using an IMG survey of residents who matched into neurosurgical residency within the previous 8 years. Productivity of IMGs conducting dedicated research at the study institution was also analyzed.

Results

Thirty-two of 115 (28%) PDs responded to the first research productivity survey and 43 (37%) to the second IMG research survey. PDs expected neurosurgery residency applicants to spend a median of 12–24 months on research (Q₁-Q₃: 0–12 to 12–24; minimum time: 0–24; maximum time: 0–48) and publish a median of 5 articles (Q₁-Q3: 2–5 to 5–10; minimum number: 0–10; maximum number: 4–20). Among 43 PDs, 34 (79%) ranked “research institution or associated personnel” as the most important factor when evaluating IMGs' research. Forty-two of 79 (53%) IMGs responding to the IMG-directed survey reported a median of 30 months (Q₁-Q₃: 18–48; range: 4–72) of neurosurgical research and 12 published articles (Q₁-Q₃: 6–24; range: 1–80) before beginning neurosurgical residency. Twenty-two PDs (69%) believed IMGs complete more research than USMGs before residency. Of 20 IMGs conducting dedicated neuroscience/neurosurgery research at the study institution, 16 of 18 who applied matched or entered a US neurosurgical training program; 2 applied and entered a US neurosurgical clinical fellowship.

Conclusion

The research work of IMGs compared to USMGs who apply to neurosurgery residency exceeds PDs' expectations regarding scientific output and research time. Many PDs perceive IMG research productivity before residency application as superior to USMGs. Although IMGs comprise a small percentage of trainees, they are responsible for a significant amount of US-published neurosurgical literature. Preresidency IMG research periods may be improved with dedicated mentoring and advising beginning before the research period, during the period, and within a neurosurgery research department, providing a formal structure such as a research fellowship or graduate program for IMGs aspiring to train in the US.

Puerto Rico Recurrence Scale: Predicting chronic subdural hematoma recurrence risk after initial surgical drainage

Background:

Chronic subdural hematoma (CSDH) commonly affects older individuals and is associated with a relatively high rate of recurrence after surgery. Many studies have created grading systems to identify patients at high risk of CSDH recurrence after the initial surgery. However, no system has been adopted widely. The authors present the first CSDH grading system created from a population-based single-center data set.

Methods:

A single-center Puerto Rican population-based retrospective analysis was performed on consecutive patients treated for a CSDH at a designated institution from July 1, 2017 to December 31, 2019. Univariate and multivariate analyses were used to create a CSDH recurrence grading scale. Retrospective validation was conducted on this sample population.

Results:

The study included 428 patients. Preoperative midline shift, postoperative midline shift, and size of postoperative subdural space differed between the recurrence and nonrecurrence groups (P = 0.03, 0.002, and 0.002, respectively). A multivariate analysis was used to create a 10-point grading scale comprising four independent variables. Recurrence rates progressively increased from the low-risk (0–3 points) to high-risk (8–10 points) groups (2.9% vs. 20.3%; P < 0.001).

Conclusion:

A 10-point grading scale for CSDH recurrence was developed with four components: preoperative midline shift (≤1 and >1 cm), laterality (bilateral, unilateral-right, and unilateral-left), size of postoperative subdural space (≤1.6 and >1.6 cm), and pneumocephalus (present or absent). Patients who scored higher on the scale had a higher risk of recurrence. This CSDH grading scale has implications for Puerto Rico and the general population as the elderly population increases worldwide.

Real-time intraoperative surgical telepathology using confocal laser endomicroscopy

OBJECTIVE

Communication between neurosurgeons and pathologists is mandatory for intraoperative decision-making and optimization of resection, especially for invasive masses. Handheld confocal laser endomicroscopy (CLE) technology provides in vivo intraoperative visualization of tissue histoarchitecture at cellular resolution. The authors evaluated the feasibility of using an innovative surgical telepathology software platform (TSP) to establish real-time, on-the-fly remote communication between the neurosurgeon using CLE and the pathologist.

METHODS

CLE and a TSP were integrated into the surgical workflow for 11 patients with brain masses (6 patients with gliomas, 3 with other primary tumors, 1 with metastasis, and 1 with reactive brain tissue). Neurosurgeons used CLE to generate video-flow images of the operative field that were displayed on monitors in the operating room. The pathologist simultaneously viewed video-flow CLE imaging using a digital tablet and communicated with the surgeon while physically located outside the operating room (1 pathologist was in another state, 4 were at home, and 6 were elsewhere in the hospital). Interpretations of the still CLE images and video-flow CLE imaging were compared with the findings on the corresponding frozen and permanent H&E histology sections.

RESULTS

Overall, 24 optical biopsies were acquired with mean ± SD 2 ± 1 optical biopsies per case. The mean duration of CLE system use was 1 ± 0.3 minutes/case and 0.25 ± 0.23 seconds/optical biopsy. The first image with identifiable histopathological features was acquired within 6 ± 0.1 seconds. Frozen sections were processed within 23 ± 2.8 minutes, which was significantly longer than CLE usage (p < 0.001). Video-flow CLE was used to correctly interpret tissue histoarchitecture in 96% of optical biopsies, which was substantially higher than the accuracy of using still CLE images (63%) (p = 0.005).

CONCLUSIONS

When CLE is employed in tandem with a TSP, neurosurgeons and pathologists can view and interpret CLE images remotely and in real time without the need to biopsy tissue. A TSP allowed neurosurgeons to receive real-time feedback on the optically interrogated tissue microstructure, thereby improving cross-functional communication and intraoperative decision-making and resulting in significant workflow advantages over the use of frozen section analysis.

Development and Validation of a Novel Methodological Pipeline to Integrate Neuroimaging and Photogrammetry for Immersive 3D Cadaveric Neurosurgical Simulation

Background

Visualizing and comprehending 3-dimensional (3D) neuroanatomy is challenging. Cadaver dissection is limited by low availability, high cost, and the need for specialized facilities. New technologies, including 3D rendering of neuroimaging, 3D pictures, and 3D videos, are filling this gap and facilitating learning, but they also have limitations. This proof-of-concept study explored the feasibility of combining the spatial accuracy of 3D reconstructed neuroimaging data with realistic texture and fine anatomical details from 3D photogrammetry to create high-fidelity cadaveric neurosurgical simulations.

Methods

Four fixed and injected cadaver heads underwent neuroimaging. To create 3D virtual models, surfaces were rendered using magnetic resonance imaging (MRI) and computed tomography (CT) scans, and segmented anatomical structures were created. A stepwise pterional craniotomy procedure was performed with synchronous neuronavigation and photogrammetry data collection. All points acquired in 3D navigational space were imported and registered in a 3D virtual model space. A novel machine learning-assisted monocular-depth estimation tool was used to create 3D reconstructions of 2-dimensional (2D) photographs. Depth maps were converted into 3D mesh geometry, which was merged with the 3D virtual model’s brain surface anatomy to test its accuracy. Quantitative measurements were used to validate the spatial accuracy of 3D reconstructions of different techniques.

Results

Successful multilayered 3D virtual models were created using volumetric neuroimaging data. The monocular-depth estimation technique created qualitatively accurate 3D representations of photographs. When 2 models were merged, 63% of surface maps were perfectly matched (mean [SD] deviation 0.7 ± 1.9 mm; range −7 to 7 mm). Maximal distortions were observed at the epicenter and toward the edges of the imaged surfaces. Virtual 3D models provided accurate virtual measurements (margin of error <1.5 mm) as validated by cross-measurements performed in a real-world setting.

Conclusion

The novel technique of co-registering neuroimaging and photogrammetry-based 3D models can (1) substantially supplement anatomical knowledge by adding detail and texture to 3D virtual models, (2) meaningfully improve the spatial accuracy of 3D photogrammetry, (3) allow for accurate quantitative measurements without the need for actual dissection, (4) digitalize the complete surface anatomy of a cadaver, and (5) be used in realistic surgical simulations to improve neurosurgical education.

Comparison of Anatomic Exposure After Petrosectomy Using Anterior Transpetrosal and Endoscopic Endonasal Approaches: Experimental Cadaveric Study

OBJECTIVE

Transcranial anterior petrosectomy (AP) is a classic approach; however, it is associated with adverse consequences. The endoscopic endonasal approach (EEA) has been developed as an alternative. We describe surgical techniques for AP and EEA and compare the anatomic exposures of each.

METHODS

Ten cadaveric heads (20 sides) were dissected. Specimens were divided into 4 groups: 1) AP, 2) EEA for medial petrosectomy (MP), 3) EEA for inferior petrosectomy (IP), and 4) EEA for inferomedial petrosectomy (IMP). Outcomes were areas of exposure, angles of attack to neurovascular structures, and bone resection volumes.

RESULTS

AP had a greater area of exposure than did MP and IP (P = 0.30, P < 0.01) and had a higher angle of attack to the distal part of the facial nerve-vestibulocochlear nerve (cranial nerve [CN] VII/VIII) complex than did IP and IMP (P < 0.01). MP had a lower angle of attack than IMP to the midpons (P = 0.04) and to the anterior inferior cerebellar artery (P < 0.01). Compared with IMP, IP had a lower angle of attack to the proximal part of the CN VII/VIII complex (P < 0.01) and the flocculus (P < 0.01). The bone resection volume in AP was significantly less than that in MP, IP, and IMP (P < 0.01).

CONCLUSIONS

AP and all EEA techniques had specific advantages for each specific area. We suggest AP for the ventrolateral pons and the anterior superior internal auditory canal, MP for the midline clivus, IP for the ventrolateral brainstem, and IMP to enhance the lateral corridor of the abducens nerve.

Hydrogel Check-Valves for the Treatment of Hydrocephalic Fluid Retention with Wireless Fully-Passive Sensor for the Intracranial Pressure Measurement

Hydrocephalus (HCP) is a neurological disease resulting from the disruption of the cerebrospinal fluid (CSF) drainage mechanism in the brain. Reliable draining of CSF is necessary to treat hydrocephalus. The current standard of care is an implantable shunt system. However, shunts have a high failure rate caused by mechanical malfunctions, obstructions, infection, blockage, breakage, and over or under drainage. Such shunt failures can be difficult to diagnose due to nonspecific systems and the lack of long-term implantable pressure sensors. Herein, we present the evaluation of a fully realized and passive implantable valve made of hydrogel to restore CSF draining operations within the cranium. The valves are designed to achieve a non-zero cracking pressure and no reverse flow leakage by using hydrogel swelling. The valves were evaluated in a realistic fluidic environment with ex vivo CSF and brain tissue. They display a successful operation across a range of conditions, with negligible reverse flow leakage. Additionally, a novel wireless pressure sensor was incorporated alongside the valve for in situ intracranial pressure measurement. The wireless pressure sensor successfully replicated standard measurements. Those evaluations show the reproducibility of the valve and sensor functions and support the system’s potential as a chronic implant to replace standard shunt systems.

A two-stage combined anterolateral and endoscopic endonasal approach to the petroclival region: an anatomical study and clinical application

OBJECT

The pretemporal transcavernous anterior petrosal (PTAP) approach and the combined petrosal (CP) approach have been used to resect petroclival meningiomas (PCMs). In this cadaveric anatomical study, a two-stage combined PTAP and endoscopic endonasal far medial (EEFM) approach (the PTAPE approach) was compared morphometrically to the CP approach. A case study provides a clinical example of using the PTAPE approach to treat a patient with a PCM. The key elements of the approach selection process are outlined.

METHODS

Five cadaveric specimens underwent a CP approach and 5 underwent a PTAPE approach. The area of drilled clivus, length of multiple cranial nerves (CNs), and the area of brain stem exposure were measured, reported as means (standard deviations) by group, and compared.

RESULTS

The total area of the clivus drilled in the PTAPE group (695.3 [121.7] mm²) was greater than in the CP group (88.7 [17.06] mm², P < 0.01). Longer segments of CN VI were exposed via the PTAPE than the CP approach (35.6 [9.07] vs. 16.3 [6.02] mm, P < 0.01). CN XII (8.8 [1.06] mm) was exposed only in the PTAPE group. Above the pontomedullary sulcus, the total area of brain stem exposed was greater with the PTAPE than the CP approach (1003.4 [219.5] mm² vs. 437.6 [83.7] mm², P < 0.01). Similarly, the total exposure of the medulla was greater after the PTAPE than the CP exposure (240.2 [57.06] mm² vs. 48.1 [19.9] mm², P < 0.01).

CONCLUSION

A combined open-endoscopic paradigm is proposed for managing large PCMs. This approach incorporates the EEFM approach to address the limitations of the PTAP and the CP approach in a systematic fashion. Understanding the anatomical findings of this study will aid in tailoring surgical approaches to patients with these complex lesions.

Tracking glioblastoma progression after initial resection with minimal reaction-diffusion models

We describe a preliminary effort to model the growth and progression of glioblastoma multiforme, an aggressive form of primary brain cancer, in patients undergoing treatment for recurrence of tumor following initial surgery and chemoradiation. Two reaction-diffusion models are used: the Fisher-Kolmogorov equation and a 2-population model, developed by the authors, that divides the tumor into actively proliferating and quiescent (or necrotic) cells. The models are simulated on 3-dimensional brain geometries derived from magnetic resonance imaging (MRI) scans provided by the Barrow Neurological Institute. The study consists of 17 clinical time intervals across 10 patients that have been followed in detail, each of whom shows significant progression of tumor over a period of 1 to 3 months on sequential follow up scans. A Taguchi sampling design is implemented to estimate the variability of the predicted tumors to using 144 different choices of model parameters. In 9 cases, model parameters can be identified such that the simulated tumor, using both models, contains at least 40 percent of the volume of the observed tumor. We discuss some potential improvements that can be made to the parameterizations of the models and their initialization.

Surgical Anatomy of the Middle Communicating Artery and Guidelines for Predicting the Feasibility of M2-M2 End-to-End Reimplantation

BACKGROUND

M2-M2 end-to-end reimplantation that creates a middle communicating artery has recently been proposed as a reconstruction technique to treat complex aneurysms of the middle cerebral artery that are not amenable to clipping.

OBJECTIVE

To examine the surgical anatomy, define anatomic variables, and explore the feasibility of this bypass.

METHODS

Sixteen cadaver heads were prepared for bypass simulation. After the middle cerebral artery bifurcation was approached, the proximal insular (M2) segments and perforators were explored. To define the maximal distance between the M2 segments that allows the bypass to be performed, the M2 segments were mobilized and reimplanted in an end-to-end fashion.

RESULTS

Successful reimplantation was performed in all specimens. The mean maximal distance between the M2 segments to create the proposed reimplantation was 9.1 ± 3.2 mm. The mean vessel displacement was significantly greater for the superior (6.0 ± 2.3 mm) M2 segment than for the inferior (3.2 ± 1.4 mm) M2 segment (P < .001).

CONCLUSION

In this cadaveric study, the stumps of the M2 segments located at a distance of ≤9.1 mm could be approximated to create a feasible M2-M2 end-to-end anastomosis. Intraoperative inspection of the M2 segments and their perforators could allow further assessment of the feasibility of the procedure before final revascularization decisions are made.

Volumetric 3-Dimensional Analysis of the Supraorbital vs Pterional Approach to Paramedian Vascular Structures: Comprehensive Assessment of Surgical Maneuverability

BACKGROUND

Both the pterional and supraorbital approaches have been proposed as optimal access corridors to deep and paramedian anatomy.

OBJECTIVE

To assess key intracranial structures accessed through the surgical approaches using the angle of attack (AOA) and the volume of surgical freedom (VSF) methodologies.

METHODS

Ten pterional and 10 supraorbital craniotomies were completed. Data points were measured using a neuronavigation system. A comparative analysis of the craniocaudal AOA, mediolateral AOA, and VSF of the ipsilateral paraclinoid internal carotid artery (ICA), terminal ICA, and anterior communicating artery (ACoA) complex was completed.

RESULTS

For the paraclinoid ICA, the pterional approach produced larger craniocaudal AOA, mediolateral AOA, and VSF than the supraorbital approach (28.06° vs 10.52°, 33.76° vs 23.95°, and 68.73 vs 22.59 mm3 normalized unit [NU], respectively; P < .001). The terminal ICA showed similar superiority of the pterional approach in all quantitative parameters (27.43° vs 11.65°, 30.62° vs 25.31°, and 57.41 vs 17.36 mm3 NU; P < .05). For the ACoA, there were statistically significant differences between the results obtained using the pterional and supraorbital approaches (18.45° vs 10.11°, 29.68° vs 21.01°, and 26.81 vs 16.53 mm3 NU; P < .005).

CONCLUSION

The pterional craniotomy was significantly superior in all instrument maneuverability parameters for approaching the ipsilateral paraclinoid ICA, terminal ICA, and ACoA. This global evaluation of 2-dimensional and 3-dimensional surgical freedom and instrument maneuverability by amalgamating the craniocaudal AOA, mediolateral AOA, and VSF produces a comprehensive assessment while generating spatially and anatomically accurate corridor models that provide improved visual depiction for preoperative planning and surgical decision-making.