Quantitative Analysis of the Supraorbital, Transorbital Microscopic, and Transorbital Neuroendoscopic Approaches to the Anterior Skull Base and Paramedian Vasculature

Objectives  Our objective was to compare transorbital neuroendoscopic surgery (TONES) with open craniotomy and analyze the effect of visualization technology on surgical freedom. Design  Anatomic dissections included supraorbital craniotomy (SOC), transorbital microscopic surgery (TMS), and TONES. Setting  The study was performed in a neurosurgical anatomy laboratory. Participants  Neurosurgeons dissecting cadaveric specimens were included in the study. Main Outcome Measures  Morphometric analysis of cranial nerve (CN) accessible lengths, frontal lobe base area of exposure, and craniocaudal and mediolateral angle of attack and volume of surgical freedom (VSF) of the paraclinoid internal carotid artery (ICA), terminal ICA, and anterior communicating artery (ACoA). Results  The mean (standard deviation [SD]) frontal lobe base parenchymal exposures for SOC, TMS, and TONES were 955.4 (261.7) mm 2 , 846.2 (249.9) mm 2 , and 944.7 (158.8) mm 2 , respectively. Access to distal vasculature was hindered when using TMS and TONES. Multivariate analysis estimated that accessing the paraclinoid ICA with SOC would provide an 11.2- mm 3 increase in normalized volume (NV) compared with transorbital corridors ( p  < 0.001). There was no difference between the three approaches for ipsilateral terminal ICA VSF ( p  = 0.71). Compared with TONES, TMS provided more access to the terminal ICA. For the ACoA, SOC produced the greatest access corridor maneuverability (mean [SD] NV: 15.6 [5.6] mm 3 for SOC, 13.7 [4.4] mm 3 for TMS, and 7.2 [3.5] mm 3 for TONES; p  = 0.01). Conclusion  SOC provides superior surgical freedom for targets that require more lateral maneuverability, but the transorbital corridor is an option for accessing the frontal lobe base and terminal ICA. Instrument freedom differs quantifiably between the microscope and endoscope. A combined visualization strategy is optimal for the transorbital corridor.

Volume of Operative Maneuverability as a New Measurement in Neuroanatomical Research: A Methodological Quantitative Study and Translational Use in the Operating Room

OBJECTIVE

The lack of standardized metrics in neuroanatomical research limits the objective assessment of neurosurgical approaches. We introduce a novel volume-based parameter, the Volume of Operative Maneuverability (VOM), and evaluate its utility in quantifying surgical corridor dimensions.

METHODS

Seven microscopic and endoscopic skull base approaches were performed on 4 embalmed latex-injected human cadaveric specimens. A spatial principal component analysis algorithm converted surgical entry and target areas into ellipses, allowing ellipsoidal-based VOM calculations. Corridor length ("target distance") and a fixed 10 mm distance from the target ("standardized VOM" [sVOM]) were also measured. Feasibility and reproducibility were assessed using three-dimensional photogrammetry, preoperative imaging models, and a clinical case.

RESULTS

Endoscopic endonasal and anterior transmaxillary approaches offered sufficient corridor volume and trajectory distance but created longer, narrower surgical corridors with lower sVOM than transcranial approaches. Conversely, pretemporal-orbitozygomatic and subtemporal corridors showed the highest VOM and sVOM. Illustrative examples confirmed consistent measurement in photogrammetry and preoperative imaging. A clinical case involving a right spheno-cavernous meningioma demonstrated a VOM of 2.328 cm³, sVOM of 0.615 cm³, and a target distance of 18 mm during extradural anterior clinoidectomy.

CONCLUSIONS

VOM provides a quantitative, reproducible metric for assessing surgical maneuverability toward irregular target surfaces, overcoming the limitations of traditional qualitative assessments. Preliminary data support its use in quantitative neuroanatomical research and suggest potential integration into surgical planning and intraoperative data collection.

Expanding horizons: the feasibility and challenges of tubular retraction in endoscopic transorbital skull base approaches

PURPOSE

Endoscopic transorbital skull base approaches are always challenging and require good anatomical knowledge.The aim of this study was to describe the anatomical pathways of endoscopic transorbital approaches and to determine the limitations of these procedures. To evaluate the feasibility of the tubular retractor and the difference with manual retractor.

METHODS

The targets of endoscopic transorbital approach were the anterior and middle cranial fossa, mesial temporal region, meckel's cave, petroclival area, opticocarotid region, anterior and lateral walls of the cavernous sinus, etc. Step-by-step anatomical dissections were performed in cadaveric heads using manual and tubular retractors.

RESULTS

Anterior and middle cranial fossa was reached. The branches of the trigeminal nerve, the lateral wall of the cavernous sinus, meckel's cave and gasserian ganglion were exposed by manual and tubular retraction using an endoscopic transorbital approach. Access to the temporal horn of the lateral ventricle and the mesial temporal region was more accessible with a tubular retractor. Also, following the anterior clinoidectomy, the cavernous segment of the internal carotid artery, as well as, the arteries of the anterior circulation were exposed to gain access the vascular skull base lesions.

CONCLUSION

The endoscopic transorbital approach is suitable for the surgical treatment of many pathologies located in the anterior and middle skull base. It provides direct access to vascular and tumoral lesions. We observed that mesial temporal region interventions are possible with this approach. The transtubular technique may have some limitations, but in selected cases it can provide clear vision without brain retraction.

Biportal Endoscopic TransOrbital and transMaxillary Approach to the Cranio-Orbital Region and Middle Cranial Fossa: A Preliminary Analysis of Maneuverability

BACKGROUND AND OBJECTIVES

Traditional and well-established transcranial approaches to the spheno-orbital region and middle cranial fossa guarantee optimal intracranial exposure, and additional orbital and zygomatic osteotomies provide further control over extracranial components to be resected; however, these techniques come at the cost of additional morbidity. The introduction of minimally invasive endoscopic approaches and the conceptualization of the so-called "multiportal" paradigm might provide an alternative route. This preliminary study investigates the feasibility of the combined Biportal Endoscopic TransOrbital and transMaxillary Approach (bETOMA) approach to the spheno-orbital and middle cranial fossa regions.

METHODS

Using 4 silicon-injected adult cadaver heads (8 sides; 16 approaches), we systematically dissected through superior eyelid ETOA and endoscopic TMA approaches. The analysis focused on pterygopalatine, infratemporal, anterior and middle cranial fossae, Meckel cave, and cavernous sinus access. We evaluated the feasibility of bETOMA using linear distances, angles of attack, and exposure areas. We also introduced volume of operative maneuverability, its standardized derivative (sVOM), target distance, visuo-operative angle, and working zone volume as novel metrics.

RESULTS

The analysis revealed comparable angles of attack between approaches. ETOA and TMA exposure areas were 918.38 ± 223.93 mm 2 and 257.07 ± 86.07 mm 2 , respectively. TMA showed a larger VOM in the greater sphenoid wing, but ETOA offered superior distal maneuverability (sVOM: 5.39 ± 1.94 vs 2.54 ± 0.79 cm 3 ) and closer intracranial space access (27.45 vs 50.83 mm). The combined approaches yielded a mean working zone volume of 13.75 ± 3.73 cm 3 in the spheno-orbital interface.

CONCLUSION

The bETOMA approach provides adequate neurovascular exposure and maneuverability to the spheno-orbital region, infratemporal, and anterior and middle cranial fossae, addressing significant limitations of previously investigated monoportal techniques (ie, optic nerve decompression, hyperostotic bone resection, and infratemporal exposure). This combined minimally invasive approach might help manage lesions harbored within the cranio-orbital interface region invading the extracranial space.

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.

Endoscopic Multiportal Approaches to Meckel's Cave: A Cadaveric Study and a Three-Dimensional Anatomical Video

Objective  This cadaveric study aims to illustrate the lateral transorbital (LTO), transantral transpterygoid (TATP), and endoscopic endonasal approaches (EEA) to Meckel's cave (MC), defining their surgical freedom, area of exposure, and advantages and limitations; thus, refining their respective indications. Design  Cadaveric study. Setting  The Anatomical Laboratory for Visuospatial Innovations in Otolaryngology and Neurosurgery (ALT-VISION) at the Ohio State University, Wexner Medical Center. Participants  Bilateral dissections of five injected cadavers (10 sides). Main Outcome Measures  Distance to targets, surgical freedom, and area of exposure provided by the EEA, TATP, and LTO approaches. Results  The TATP approach provides superior surgical freedom to foramen rotundum (167.70 ± 29.762 mm). However, surgical freedom to foramen ovale was best when using the LTO approach (75.01 ± 15.773 mm). The EEA provides a superior exposure of the medial MC (mean area of 587.69 ± 38.59 mm 2 ). The LTO and TATP approaches provide equivalent access to the lateral MC (ranging from 468.90 ± 26.98 mm 2 for TATP to 650.11 ± 35.76 mm 2 for the LTO approach). Combining approaches increases the area of exposure significantly (1,237.79 ± 48.41 mm 2 and 1,056.59 ± 48.12 mm 2 for EEA and LTO vs. EEA and TATP). Conclusion  This study thoroughly emphasizes the pros and cons of the aforementioned approaches. Each approach may be applied in selected cases as a single or as part of a combined technique. However, conventional approaches are still indicated according to extent and pathology. Level of Evidence : V.

Neuroanatomical perspectives on transorbital approaches: A meta-analysis

Background

Transorbital approaches represent a paradigm shift in skull base surgery, focusing on minimally invasive techniques that prioritize patient outcomes and surgical precision. The scientific community, recognizing the significance of these advances, necessitates a possible review and meta-analysis to encapsulate the collective efficacy, safety, and developmental trajectory of these approaches.

Methods

This was a literature review targeting literature in the past 10 years to present evidence for studies on surgical approaches transorbital. The included articles were analyzed. In addition, the references list of the included papers was searched for further articles.

Results

Studies based on the endoscopic endonasal and transorbital approach have emphasized that it is minimally invasive; on the other hand, it offers an advantage to maximal resection success in the case of skull base tumors with advanced endoscopic skills. Transorbital neuroendoscopic surgery was criticized for being highly technical and narrow in its scope, with reduced morbidity. Superior Eyelid Approach involves a direct access with hidden incisions, potential for eyelid complications. Lateral orbitotomy entailed some inherent risks, such as muscle and nerve injury, but it gave excellent exposure to lesions that are lateral in the orbit. The transorbital endoscopic intraconal approach and the transconjunctival approach give direct advantages but are, however, limited to the type of lesion and location.

Conclusion

The main technique focused on in this overview is the approaches through orbits, which greatly contribute to further innovation brought into the surgical panorama of skull base interventions. All such techniques do have their characteristics and applications, keeping them moving toward less invasiveness.

Repair of lateral temporo-sphenoidal encephalocoele via an endoscopic transorbital approach: ex vivo 3D printed simulation followed by in vivo deployment

BACKGROUND

A temporo-sphenoidal encephalocoele occurs when temporal lobe herniates through a defect in the greater wing of the sphenoid bone into the sphenoid air sinus. The natural history is not well-understood, though presentation in adulthood with CSF rhinorrhoea and/or meningitis is typical. Lateral pneumatisation of the sphenoid sinus and elevated BMI may be contributory.

AIMS

We explored the feasibility of a transorbital approach (TOA) for repair, using a combination of 3D modelling and simulation. We then successfully deployed this technique in vivo.

METHODS

CT imaging for three patients who had previously undergone transcranial repair of lateral temporo-sphenoidal encephalocoele was used to generate data allowing 3D printed models of the skull base to be produced. The transorbital approach was simulated by performing a lateral orbitotomy followed by drilling of the sphenoid wing to expose the antero-basal middle fossa. 3D object scanning was used to create virtual models of the skull base post-surgery, from which surgical access was quantified in two ways: the area (mm2) of the middle fossa exposed by the TOA and the vertical attack angle.

RESULTS

The mean surface area of the cranial access window achieved by simulated TOA was 325mm2. The mean vertical attack angle was 25°. One patient was subsequently treated successfully via TOA with no recurrence of their CSF leak, no orbital morbidity, excellent cosmesis, but resolving V2 numbness (follow-up 7 months).

CONCLUSIONS

We have shown that the transorbital approach provides adequate surgical access. In our single case, surgical repair of a lateral temporo-sphenoidal encephalocoele via TOA was feasible, safe, and effective. This approach may offer some advantages compared with transcranial or endonasal approaches.

Surgical Anatomy of the Microscopic and Endoscopic Transorbital Approach to the Middle Fossa and Cavernous Sinus: Anatomo-Radiological Study with Clinical Applications

BACKGROUND

The transorbital approaches (TOAs) have acquired growing notoriety, thanks to their ability to offer alternative corridors to the skull base. However, the limited access and the unfamiliarity with this surgical perspective make recognition of key landmarks difficult, especially for less experienced surgeons. The study wants to offer a detailed description of the anatomy to comprehend the potential and limitations of TOAs.

METHODS

Measurements of the orbit region and the surrounding areas were performed on two hundred high-resolution CT scans and thirty-nine dry skulls. Five specimens were dissected to illustrate the TOA, and one was used to perform the extradural clinoidectomy. Three clinical cases highlighted the surgical applications.

RESULTS

A step-by-step description of the key steps of the TOA was proposed and a comparison with the transcranial anterior clinoidectomy was discussed. The mean work distance was 6.1 ± 0.4 cm, and the lateral working angle increased 20 ± 5.4° after removing the lateral orbital rim.

CONCLUSIONS

TOAs are indicated in selected cases when tumor involves the lateral portion of the cavernous sinus or the middle skull base, obtaining a direct decompression of the optic nerve and avoiding excessive manipulation of the neurovascular structures. Comprehension of surgical anatomy of the orbit and its surrounding structures is essential to safely perform these approaches.

Endoscopic Approaches to the Paramedian Skull Base: An Anatomic Comparison of Contralateral Endonasal and Transmaxillary Strategies

BACKGROUND

The expanded endoscopic endonasal approach (EEA) is limited laterally by the internal carotid artery (ICA). The EEA to the paramedian skull base often requires complex maneuvers such as dissection of the Eustachian tube (ET) and foramen lacerum (FL), and ICA manipulation. An endoscopic contralateral transmaxillary approach (CTMA) has the potential to provide adequate exposure of the paramedian skull base while bypassing manipulation of the aforementioned anatomic structures.

OBJECTIVE

To quantify and compare the surgical nuances of a CTMA and a contralateral EEA when approaching the paramedian skull base in cadaveric specimens.

METHODS

Five adult cadaveric heads were dissected bilaterally (10 sides) using a contralateral EEA and a CTMA to expose targets of interest at the paramedian skull base. For each target in both approaches, the surgical freedom, angle of attack, the corridor's "perspective angle," and "turning angle" to circumvent the ICA, ET, and FL were obtained.

RESULTS

The CTMA achieved superior surgical freedom at all targets ( P < .05) except at the root entry point of cranial nerve XII. The CTMA provided superior vertical and horizontal angles of " attack " to the majority of targets of interest. Except when approaching the root entry point of cranial nerve XII, the CTMA " turning angle " around the ICA, ET, and FL were wider with CTMA for all targets.

CONCLUSION

A CTMA complements the EEA to access the paramedian skull base. A CTMA may limit the need for complex maneuvers such as ICA mobilization and dissection of the ET and FL when approaching the paramedian skull base.

Endoscopic transorbital approach for skull base lesions: a report of 16 clinical cases

Due to the deep location, complex anatomy, and adjacent vital neurovascular structures, skull base surgery is challenging and requires specific approaches. The emerging endoscopic transorbital approach (eTOA) technique provides a new approach to the orbital content, spheno-orbital region, lateral cavernous sinus, and Meckel's cave. In this study, the clinical utility and effectiveness of the eTOA are reported. Sixteen cases who underwent the eTOA were included in the current study. The patients were divided into 3 groups according to tumor location: Group A (intraorbital, 6 cases), group B (spheno-orbital, 7 cases), and group C (cavernous sinus, and Meckel's cave, 3 cases). The clinical data and surgical results were analyzed. Eight meningiomas, 2 hemangiomas, 1 low-grade glioma, 1 instance of inflammatory hyperplasia tissue, 1 Langerhans cell histiocytosis, 1 epidermoid cyst, 1 trigeminal schwannoma, and 1 bone fibrosis hyperplasia were observed. The mean tumor diameter was 2.4 cm. A single case in Group A and Group C underwent biopsy (12.5%), and 1 case of fibrous dysplasia in Group B underwent sufficient orbit decompression (6.25%). The remaining 13 cases underwent gross total tumor resection (81.25%). No cerebral-spinal fluid leak or infection occurred. And no cosmetic problems or significant complications were observed during the follow-up. As a minimally invasive technique, the eTOA has unique advantages for carefully selected skull base lesions because of its direct route, short working distance, and distinct attack angle.

The "Crista Ovale": A Reliable Anatomical Landmark in Transorbital Endoscopic Approaches to the Middle Cranial Fossa

BACKGROUND

Transorbital endoscopic approaches (TOEAs) have emerged as adjunct and alternatives for accessing the middle cranial fossa (MCF). Nuances of the skull base anatomy from a ventral transorbital endoscopic viewpoint remain to be fully described.

OBJECTIVE

To assess the anatomy of the "crista ovale" (COv), described transcranially as the midsubtemporal ridge (MSR), from a ventral transorbital perspective and evaluate its role as a landmark in TOEA to the MCF.

METHODS

Lateral TOEAs to the MCF were performed in 20 adult cadaveric heads (40 sides). The presence of the COv/MSR was evaluated under endoscopic visualization. Anatomic relationships between COv/MSR and surrounding structures were assessed. The presence of COv/MSR was also examined in 30 cadaveric head computed tomography (CT) scans (60 sides).

RESULTS

The COv/MSR was identified in 98% (39/40) of sides at the MCF, as 1 of 4 major configurations. The COv/MSR was found anterolateral to the foramen ovale and foramen spinosum (mean distance: 9.2 ± SD 2.4 mm and 12.3 ± SD 2.6 mm, respectively) directly anterior or anteromedial to the petrous apex (mean distance: 26.2 ± SD 2.6 mm) and at a mean 47.6 ± SD 4.7 mm from the approach's surgical portal. It was recognized in 95% (57/60) of CT scans.

CONCLUSION

The COv/MSR can be readily identified during TOEA to the MCF and on CT. It serves as a reliable landmark to localize the foramen ovale, foramen spinosum, and petrous apex. Further studies may confirm its surgical significance in transorbital endoscopic procedures.

A Frontal Route to Middle and Posterior Cranial Fossa: Quantitative Study for the Lateral Transorbital Endoscopic Approach and Comparison with the Subtemporal Approach

BACKGROUND

Skull base lesions within the middle cranial fossa (MCF) remain challenging. Recent reports suggest that transorbital endoscopic approaches (TOEAs) might be particularly suitable to access the MCF and expose the lateral wall of the cavernous sinus and the Meckel's cave.

METHODS

The present study was developed to compare the nuances of the subtemporal approach (STA) with those of the lateral TOEA (LTOEA) to the MCF and posterior cranial fossa (PCF) in cadaveric specimens. After orbital craniectomy, interdural opening of the cavernous sinus lateral wall (CSlw), exposure of the Gasserian ganglion, and extradural elevation of the temporal lobe was performed. Next, anterior endoscopic petrosectomy was performed and the PCF was accessed. We quantitatively analyzed and compared the angles of attack and distances between LTOEA and STA to different structures at the CSlw, petrous apex (PA), and PCF.

RESULTS

Cadaveric dissection through the LTOEA completely exposed the CSlw and PA. LTOA exhibited larger distances than the STA to all targets. Importantly, these differences were greater at the PA and its surrounding key anatomic landmarks. The horizontal and vertical angles of attack allowed by the LTOA were smaller both for the CSlw and PA. However, these differences were not significant for the vertical angle of attack at the CSlw.

CONCLUSIONS

LTOEA provides a direct ventral route to the medial aspect of MCF, PA, and PCF. Although TOEAs are versatile approaches, the unfamiliar surgical anatomy and limited instrument maneuverability demand extensive cadaveric dissection before moving to the clinical setting.

Supraorbital and mini-pterional keyhole craniotomies for brain tumors: a clinical and anatomical comparison of indications and outcomes in 204 cases

OBJECTIVE

The authors' objective was to compare the indications, outcomes, and anatomical limits of supraorbital (SO) and mini-pterional (MP) craniotomies in patients with intra- and extraaxial brain tumors, and to assess approach selection, utility of endoscopy, and surgical field overlap.

METHODS

A retrospective analysis was conducted of all brain tumor patients who underwent an SO or MP approach. The analyzed characteristics included pathology, endoscopy use, extent of resection, length of stay (LOS), and complications. On the basis of preoperative MRI data, tumor heatmaps were constructed to compare surgical access provided by both routes, including coronal projection heatmaps for parasellar tumors.

RESULTS

From 2007 to 2020, 158 patients underwent 173 (84.8%) SO craniotomies and 30 patients underwent 31 (15.2%) MP craniotomies; 71 (34.8%) procedures were reoperations. Of these 204 operations, 110 (63.6%) SO and 21 (67.7%) MP approaches were for extraaxial tumors (meningiomas in 65% and 76.2%, respectively). Gliomas and metastases together represented 84.1% and 70% of intraaxial tumors accessed with SO and MP approaches, respectively. Overall, 56.1% of tumors accessed with the SO approach and 41.9% of those accessed with the MP approach were in the parasellar region. Axial projection heatmaps showed that SO access extended along the entire ipsilateral and medial contralateral anterior cranial fossa, parasellar region, ipsilateral sylvian fissure, medial middle cranial fossa, and anterior midbrain, whereas MP access was limited to the ipsilateral middle cranial fossa, sylvian fissure, lateral parasellar region, and posterior aspect of anterior cranial fossa. Coronal projection heatmaps showed that parasellar access extended further superiorly with the SO approach compared with that of the MP approach. Endoscopy was utilized in 98 (56.6%) SO craniotomies and 7 (22.6%) MP craniotomies, with further tumor resection in 48 (49%) and 5 (71.4%) cases, respectively. Endoscope-assisted tumor removal was clustered in areas that were generally at farther distances from the craniotomy or in angled locations such as the cribriform plate region where microscopic visualization is limited. Gross-total or near-total resection was achieved in 120/173 (69%) SO approaches and 21/31 (68%) MP approaches. Major complications occurred in 11 (6.4%) SO approaches and 1 (3.2%) MP approach (p = 0.49). The median LOS decreased to 2 days in the last 2 years of the study.

CONCLUSIONS

This clinical experience suggests the SO and MP craniotomies are versatile, safe, and complementary approaches for tumors located in the anterior and middle cranial fossae and perisylvian and parasellar regions. The SO route, used in 85% of cases, achieved greater overall reach than the MP route. Both approaches may benefit from expanded visualization with endoscopy.

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.

Eyebrow incision with a crescent-shaped orbital rim craniotomy for microscopic and endoscopic transorbital approach to the anterior and middle cranial fossa: A cadaveric study and case presentation

•

The transorbital approach combining eyebrow incision and crescent-shaped craniotomy increases the surgical freedom to access the anterior and middle skull-base.

•

The technic allows the use of both endoscope and microscope.

•

The concept is at the crossroad between the supraorbital keyhole and endoscopic trans-orbital approach.

Endoscopic Transorbital Approach to Mesial Temporal Lobe for Intra-Axial Lesions: Cadaveric Study and Case Series (SevEN-008)

BACKGROUND

Endoscopic transorbital approach (ETOA) has been proposed as a minimally invasive technique for the treatment of skull base lesions located around mesial temporal lobe (MTL), mostly extra-axial pathology.

OBJECTIVE

To explore the feasibility of ETOA in accessing intraparenchymal MTL with cadaveric specimens and describe our initial clinical experience of ETOA for intra-axial lesions in MTL.

METHODS

Anatomic dissections were performed in 4 adult cadaveric heads using a 0° endoscope. First, a stepwise anatomical investigation of ETOA to intraparenchymal MTL was explored. Then, ETOA was applied clinically for 7 patients with intra-axial lesions in MTL, predominantly high-grade gliomas (HGGs) and low-grade gliomas (LGGs).

RESULTS

The extradural stage of ETOA entailed a superior eyelid incision followed by orbital retraction, drilling of orbital roof, greater and lesser wing of sphenoid bone, and cutting of the meningo-orbital band. For the intradural stage, the brain tissue medial to the occipito-temporal gyrus was aspirated until the temporal horn was opened. The structures of MTL could be aspirated selectively in a subpial manner without injury to the neurovascular structures of the ambient and sylvian cisterns, and the lateral neocortex. After cadaveric validation, ETOA was successfully performed for 4 patients with HGGs and 3 patients with LGGs. Gross total resection was achieved in 6 patients (85.7%) without significant surgical morbidities including visual field deficits.

CONCLUSION

ETOA provides a logical line of access for intra-axial lesions in MTL. The safe and natural surgical trajectory of ETOA can spare brain retraction, neurovascular injury, and disruption of the lateral neocortex.

Optimal indications and limitations of endoscopic transorbital superior eyelid surgery for spheno-orbital meningiomas

OBJECTIVE

Spheno-orbital meningiomas (SOMs) are complicated tumors that involve multiple structures at initial presentation, such as the orbit, temporalis muscle, sphenoidal bone, cavernous sinus, and temporal or infratemporal fossa. The infiltrative growth and complexity of this type of meningioma make total resection impossible. In this study, the authors evaluated the surgical outcome of the endoscopic transorbital approach (eTOA) for SOM. In addition, they identified optimal indications for the use of eTOA and analyzed the feasibility of this approach as a minimally invasive surgery for SOMs of varying types and locations at presentation.

METHODS

Between September 2016 and December 2019, the authors performed eTOA in 41 patients with SOM with or without orbital involvement at 3 independent tertiary institutions. The authors evaluated the surgical outcomes of eTOA for SOM and investigated several factors that affect the outcome, such as tumor volume, tumor location, and the presence of lateral orbitotomy. Gross-total resection (GTR) was defined as complete resection of the tumor or intended subtotal resection except the cavernous sinus. This study was undertaken as a multicenter project (006) of the Korean Society of Endoscopic Neurosurgery (KOSEN-006).

RESULTS

There were 41 patients (5 men and 36 women) with a median age of 52.0 years (range 24-73 years). Twenty-one patients had tumors that involved the orbital structure, while 14 patients had tumors that presented at the sphenoidal bone along with other structures, such as the cavernous sinus, temporal fossa, and infratemporal fossa. Fifteen patients had the globulous type of tumor and 26 patients had the en plaque type. Overall, GTR was achieved in 21 of 41 patients (51.2%), and complications included CSF leaks in 2 patients and wound complications in 2 patients. Multiple logistic regression analysis showed that the en plaque type of tumor, absence of lateral orbital rim osteotomy, involvement of the temporal floor or infratemporal fossa, and involvement of the orbit and medial one-third of the greater sphenoidal wing were closely associated with lower GTR rates (p < 0.05). Multivariate analysis revealed that the en plaque type of tumor and the absence of lateral orbital rim osteotomy were significant predictors for lower GTR rate.

CONCLUSIONS

The en plaque type of SOM remains a challenge despite advances in technique such as minimally invasive surgery. Overall, clinical outcome of eTOA for SOM was comparable to the transcranial surgery. To achieve GTR, eTOA is recommended, with additional lateral orbital rim osteotomy for globulous-type tumors, without involving the floor of the temporal and infratemporal fossa.

Transorbital Neuroendoscopic Surgery as a Mainstream Neurosurgical Corridor: A Systematic Review

BACKGROUND

Transorbital neuroendoscopic surgery (TONES) offers a new level of minimally invasive, minimally disfiguring skull base surgery with maximal surgical visualization.

METHODS

This review systematically assesses the body of published anatomic (cadaveric) and clinical evidence for the approach. PubMed, Cochrane Library, Ovid MEDLINE, and Embase were systematically searched for articles in which the TONES surgical technique was used in an anatomic, clinical, or combined study. The outcomes of interest included identification of the diseases, operative outcomes, and complication rates.

RESULTS

Twenty-three articles were selected for this systematic review: 10 were purely anatomic, 10 were clinical, and 3 had both clinical and cadaveric components. The articles reported 69 patients undergoing transorbital or combined transorbital and transnasal intervention. A total of 30 cases of cerebrospinal fluid leak were documented; of these, 28 (93%) had successful resolution, 2 (7%) had recurrence, and 5 (15%) experienced complications. A total of 31 tumors were biopsied (n = 1), resected (n = 22), or debulked (n = 8). Meningiomas were the most common lesion managed via TONES, with 5 of 7 patients with meningioma who reported preoperative neurologic deficits experiencing an improvement in extraocular movement impairment, visual acuity, proptosis, and ptosis. Transient postoperative clinical sequelae, including diplopia and ptosis, were increasingly associated with the superior lid crease incision and the sole transorbital approach.

CONCLUSIONS

TONES is a significant development in transorbital skull base surgery. However, comprehensive, robust, comparative analyses and increasing use and generalizability of this technique in skull base surgery are awaited.

Comparative anatomical analysis between the minipterional and supraorbital approaches

OBJECTIVE

Keyhole approaches, namely the minipterional approach (MPTa) and the supraorbital approach (SOa), are alternatives to the standard pterional approach to treat lesions located in the anterior and middle cranial fossae. Despite their increasing popularity and acceptance, the indications and limitations of these approaches require further assessment. The purpose of the present study was to determine the differences in the area of surgical exposure and surgical maneuverability provided by the MPTa and SOa.

METHODS

The areas of surgical exposure afforded by the MPTa and SOa were analyzed in 12 sides of cadaver heads by using a microscope and a neuronavigation system. The area of exposure of the region of interest and surgical freedom (maneuverability) of each approach were calculated.

RESULTS

The area of exposure was significantly larger in the MPTa than in the SOa (1250 ± 223 mm2 vs 939 ± 139 mm2, p = 0.002). The MPTa provided larger areas of exposure in the ipsilateral and midline compartments, whereas there was no significant difference in the area of exposure in the contralateral compartment. All targets in the anterior circulation had significantly larger areas of surgical freedom when treated via the MPTa versus the SOa.

CONCLUSIONS

The MPTa provides greater surgical exposure and better maneuverability than that offered by the SOa. The SOa may be advantageous as a direct corridor for treating lesions located in the contralateral side or in the anterior cranial fossa, but the surgical exposure provided in the midline region is inferior to that exposed by the MPTa.

Transorbital endoscopic approaches to the skull base: a systematic literature review and anatomical description

Transorbital endoscopic approaches are increasing in popularity as they provide corridors to reach various areas of the ventral skull base through the orbit. They can be used either alone or in combination with different approaches when dealing with the pathologies of the skull base. The objective of the current study is to evaluate the surgical anatomy of transorbital endoscopic approaches by cadaver dissections as well as providing objective clinical data on their actual employment and morbidity through a systematic review of the current literature. Four cadaveric specimens were dissected, and step-by-step dissection of each endoscopic transorbital approach was performed to identify the main anatomic landmarks and corridors. A systematic review with pooled analysis of the current literature from January 2000 to April 2020 was performed and the related studies were analyzed. Main anatomical landmarks are presented based on the anatomical study and systematic review of the literature. With emphasis on the specific transorbital approach used, indications, surgical technique, and complications are reviewed through the systematic review of 42 studies (19 in vivo and 23 anatomical dissections) including 193 patients. In conclusion, transorbital endoscopic approaches are promising and appear as feasible techniques for the surgical treatment of skull base lesions. Surgical anatomy of transorbital endoscopic approaches can be mastered through knowledge of a number of anatomical landmarks. Based on data available in the literature, transorbital endoscopic approaches represent an important complementary that should be included in the armamentarium of a skull base team.

Progressive Orbitotomy and Graduated Expansion of the Supraorbital Keyhole: A Comparison with Alternative Minimally Invasive Approaches to the Paraclinoid Region

BACKGROUND

Various minimally invasive approaches, such as supraorbital (SO), minipterional (MPT), and translateral orbital (TLO), can access the paraclinoid region. Studies have described these approaches individually but have not directly compared all of them in the same anatomic specimen.

METHODS

Using virtual reality models generated from computed tomography studies of living subjects, we simulated TLO, MPT, and variations of SO approaches, without and with removal of the orbital rim and sphenoid wing. We measured the area of freedom (AOF), distance, and angle of attack to 4 paraclinoid targets: anterior clinoid process, optic foramen, lateral superior orbital fissure, and maxillary strut.

RESULTS

For superiorly positioned targets, such as anterior clinoid process and optic foramen, MPT provided a larger AOF compared with the supraorbital approach. However, with progressive drilling of the orbital roof and lesser wing of the sphenoid, the SO corridor AOF was equivalent to MPT at the anterior clinoid process and larger at the optic foramen (P = 0.003). To the lateral superior orbital fissure, TLO had the most limited AOF, and MPT had the greatest (P < 0.01 for all comparisons). For the maxillary strut, MPT, TLO, and SO with orbitotomy and sphenoidectomy all provided a similar AOF.

CONCLUSIONS

For surgical targets in the paraclinoid region, MPT provided a greater AOF and shorter distance compared with TLO and limited SO approaches. With progressive enlargement of the SO corridor, SO with orbitotomy and sphenoidectomy matched and occasionally superseded the AOF of MPT. However, the AOF to inferomedial targets such as the maxillary strut was similar among all approaches.

Robotics in Pediatric Otolaryngology-Head and Neck Surgery and Advanced Surgical Planning

Robotic surgery has been shown to be feasible and successful in several areas of pediatric head and neck surgery. However, adoption has been limited. Robotic surgery may be better integrated into practice with advanced preoperative surgical planning and the design of new robotic platforms with instrumentation specific for the application. With continued investigations, computer-aided surgical planning techniques including three-dimensional printing, virtual reality, multiobjective cost function for optimization of approach, mirror image overlay, and flexible robotic instruments may demonstrate value and utility over current practice.

Biportal endoscopic transorbital approach: a quantitative anatomical study and clinical application

BACKGROUND

We devised a biportal endoscopic transorbital approach (BiETOA) to gain surgical freedom by making a port for the endoscope and investigated the benefits and limitations of BiETOA.

METHODS

A cylindrical port was designed and 3-D printed using biocompatible material. The port was inserted through a keyhole between the superolateral side of the orbital rim and the temporal muscle. An endoscope was inserted through the port, and other instruments were inserted through the conventional transorbital route. BiETOA was used to dissect eight cadaveric heads, and the angle of attack and surgical freedom were assessed.

RESULTS

The mean maximal angle of attack was significantly different in BiETOA and endoscopic transorbital approach (ETOA) (P < 0.01) but not in BiETOA and ETOA lateral orbital rim (LOR) osteotomy (P = 0.207, P = 0.21). The mean surgical freedom was significantly different in BiETOA and ETOA (P < 0.01) and in BiETOA and ETOA LOR osteotomy (P < 0.01). In the clinical cases, tumors were removed successfully without any complications.

CONCLUSIONS

BiETOA provided increased surgical freedom and better visibility of deep target lesion and resulted in good surgical and cosmetic outcomes.

Ophthalmic and orbital considerations in the evaluation of skull base malignancies

INTRODUCTION

The orbital contents, afferent and efferent visual pathways, and the cranial nerves involved in eye movement, corneal sensation and eyelid closure traverse the skull base, a region bounded by the intracranial cavity, the paranasal sinuses, and the deep spaces of the face and head. As such, tumors from above or below have potential to affect some aspect of the visual system.

METHODS

We discuss here the clinical ophthalmologic and orbital considerations in the evaluation of patients with these tumors, as well as the ophthalmic sequelae of treatment with radiation or surgery (or both). And for the surgeon, we discuss the ophthalmic and orbital considerations in surgical planning, the role of the orbital surgeon in skull base surgery, and briefly discuss transorbital approaches to the skull base.

RESULTS AND CONCLUSION

Ophthalmic and orbital dysfunction may be the main source of disability in patients with skull base malignancy; it is thus incumbent on those who manage patients with tumors of this region to be aware of the ophthalmic, neuro-ophthalmic and orbital manifestations, so as to best tailor therapy and monitor treatment outcomes.

Comparative Analysis of Endoscopic Transorbital Approach and Extended Mini-Pterional Approach for Sphenoid Wing Meningiomas with Osseous Involvement: Preliminary Surgical Results

OBJECTIVE

Sphenoid wing meningiomas (SWMs) can be treated with complete surgical resection and the recently introduced endoscopic transorbital approach (ETOA) offers a minimally invasive alternative. In this study, the surgical outcome of ETOA and the extended mini-pterional approach (eMPTA) for SWMs with osseous involvement is compared.

METHODS

From October 2015 to May 2019, 24 patients underwent surgery for SWMs with osseous involvement. Among them, tumor resection was performed by ETOA for 11 patients (45.8%) and eMPTA for 13 patients (54.2%). The tumor characteristics, surgical outcome and morbidity, and approach-related aesthetic outcome were analyzed and compared retrospectively between ETOA and eMPTA based on SWM classification.

RESULTS

The location of SWMs was mostly the middle sphenoid ridge (group III) (45.8%), followed by the greater sphenoid wing (group IV) (29.2%). Simpson resection grades I/II were achieved in 9 of 11 patients (81.8%) with ETOA and 11 of 13 patients (84.6%) with eMPTA. There were no differences in tumor characteristics between the 2 approaches. Surgery time, surgical bleeding, and hospital length of stay were significantly shorter with ETOA. Three patients had transient surgical morbidities such as diplopia (n = 1), ptosis (n = 1), and cerebrospinal fluid leak (n = 1) after ETOA. No differences could be seen in surgical morbidities between ETOA and eMPTA.

CONCLUSIONS

ETOA can provide direct access to the sphenoid bone and resectability with a more rapid and minimally invasive exposure than does eMPTA. Maximal subtotal resection with extensive sphenoid bone decompression for tumors with cavernous sinus infiltration is the key to a good clinical outcome, regardless of the surgical approach.

Quantitative Anatomic Study of the Minipterional Craniotomy in the Paraclinoid Region: Benefits of Extradural Anterior Clinoidectomy

BACKGROUND

Extradural anterior clinoidectomy (eAC) via the minipterional craniotomy (MPT) approach (MPT+eAC) has been recently introduced to the neurosurgical armamentarium to improve access to anterior and middle fossa skull base structures using a minimally invasive approach. However, the effect of extradural clinoidectomy on surgical exposure with the minipterional approach has not been evaluated. Moreover, the effect of eAC on surgical maneuverability has not been established for either traditional pterional or minipterional craniotomy. We sought to illustrate the microsurgical anatomy of the MPT+eAC and to evaluate the effect of eAC on surgical exposure and maneuverability.

METHODS

The area of exposure, area of surgical freedom, and maneuverability score for the MPT approach and MPT+eAC were compared in 5 cadaveric heads.

RESULTS

Compared with the MPT approach, the MPT+eAC enlarged the area of exposure approximately twofold (93 cm² vs. 184 cm²; P < 0.001). All targets considered in the paraclinoid region, including the posterior communicating artery origin, prechiasmatic region, and ophthalmic artery origin, showed an increase in surgical freedom and maneuverability after performing eAC. Targets remote from the clinoid such as the internal carotid bifurcation were not affected.

CONCLUSIONS

MPT+eAC offers a larger area of exposure and greater surgical freedom and maneuverability at the paraclinoid region using this minimally invasive approach.