Endoscopic transorbital route to the petrous apex: a feasibility anatomic study

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.

Assessing the Feasibility of Selective Piezoelectric Osteotomy in Transorbital Approach to the Middle Cranial Fossa: Anatomical and Quantitative Study and Surgical Implications

OBJECTIVE

To verify the feasibility and discuss advantages and disadvantages of a piezoelectric orbitotomy during superior eyelid endoscopic transorbital approach (SETOA). An illustrative case demonstrating the application of this novel technique is also presented.

METHODS

Exoscopic/endoscopic SETOA to middle cranial fossa was performed on 5 adult specimens. The surgical corridor was created via piezoelectric orbitotomy by performing 3 selective and safe micrometric bone cuts providing a 1-piece trapezoid bone flap, which was repositioned and secured at the end of the procedure. A three-dimensional scan of the bone flap allowed us to reconstruct a three-dimensional model and calculate its volume.

RESULTS

Anatomical-morphometric quantitative analysis showed a mean bone volume gain of 1574.26 mm3 by using piezoelectric orbitotomy. Piezoelectric orbitotomy also yielded concrete surgical advantages and theoretical benefits in terms of functional and esthetic outcomes. All osteotomies were micrometric clear-cut and precise, resulting in a very thin bone gap; complete sparing of soft tissues and neurovascular structures in and around the orbit was observed. Lateral orbital wall reconstruction by replacing the bone flap was performed to mitigate the risk of enophthalmos, proptosis, cerebrospinal leakage, pseudomeningocele, and pulsatile headache, which represent significant challenges.

CONCLUSIONS

Piezoelectric orbitotomy may offer a viable, selective, effective, safe alternative to high-speed drilling during SETOA, especially for patients with intra-axial pathologies, in which a watertight closure is mandatory. This procedure could prevent or decrease the risk of some of the main postoperative complications associated with standard SETOA, potentially resulting in better functional and esthetic outcomes.

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.

Management of large Trigeminal Schwannoma: long-term oncologic and functional outcome from a multicentric retrospective cohort

OBJECTIVE

Trigeminal schwannoma (TS), though a rare and benign tumor, becomes a significant surgical challenge due to its intricate location. This study aims to detail the long-term functional outcomes and tumor control post-surgical resection.

METHOD

We analyzed a multicentric retrospective cohort of 39 patients operated on for a TS in five tertiary centers between January 1993 and July 2022.

RESULTS

Six TS (15%) were in the middle fossa (type M), two (5%) in the posterior fossa (type P), and two (5%) were extracranial (type E). Twenty-nine (75%) were Dumbbell shape: Eighteen (47%) were MP type, seven (18%) were MPE type, and four (10%) were ME type. Fifth nerve symptoms were the foremost preoperative complaint: hypesthesia (51%), trigeminal neuralgia (36%), and paresthesia (30%). We report a favorable evolution course for 61% of preexisting deficits (half of patients with preoperative paresthesia and neuralgia improved while only 5% of preoperative hypesthesia improved). Postoperative hypesthesia was the most frequent de novo deficit 14 (74%) and resolved in solely half the cases. Various approaches were used according to tumor type. Gross total resection (GTR), Subtotal resection (STR), and partial resection (PR) were achieved in respectively 33% (N = 13), 10% (N = 4), and 56% (N = 22) of patients. The mean clinical and radiological FU was 63 months (12 - 283 months). GTR led to no sign of recurrence (mean FU: 60 months - range: 12-283 months). For STR or PR (67%): 23 (88%) were assigned to a Wait-&-rescan policy (WS group) which offered stability in 70% (N = 16). Three cases (8%) underwent a complementary GKS (GammaKnife) on the residual lesion (GK group) without tumor change.

CONCLUSION

For large TS, the completeness of resection must consider the potential functional burden of surgery. With giant infiltrating lesions, a strategy of planned subtotal resection, complemented by radiosurgery, either complementary or uppon regrowth, may provide similar oncological outcomes.

Is It Time for a Paradigm Shift in the Surgical Management of Trigeminal Schwannomas? Evaluating the Role of the Transorbital Approach: An Anatomo-Clinical Study and Systematic Literature Review

BACKGROUND

Endoscopic transorbital approach emerged in recent years as an effective, minimally invasive route to access Meckel's cave area. Several case series proved its effectiveness in the surgical treatment of trigeminal schwannomas. This route provides the advantages of a minimally invasive approach associated with low morbidity rates. In this anatomo-clinical study we illustrate the usefulness of the superior eyelid transorbital approach for the surgical treatment of trigeminal schwannoma guiding the clinical applicability of the anatomical findings into real surgical practice.

METHODS

Superior eyelid transorbital endoscopic approach was performed on 8 cadaveric specimens, and the surgical results were confirmed in a retrospective review of all the surgical cases of transorbital surgery performed by the senior authors providing an illustrative case. Finally, we performed a literature review of all the case series of trigeminal schwannomas operated through an endoscopic transorbital approach.

RESULTS

Stepwise dissection was divided in 3 phases: skin, endo-orbital, and endocranial. The illustrative case provided demonstrate gross total resection of a cavernous sinus type trigeminal schwannomas treated through this route. Literature review revealed 68 cases of trigeminal schwannomas that were successfully treated using the transorbital approach.

CONCLUSIONS

The endoscopic transorbital approach may offer a valuable alternative for the surgical treatment of trigeminal schwannomas. This technique provides a minimally invasive, direct and natural "interdural" route to the lateral wall of the cavernous sinus and Meckel's cave.

The Transorbital Approach: A Comprehensive Review of Targets, Surgical Techniques, and Multiportal Variants

The transorbital approach (TOA) is gaining popularity in skull base surgery scenarios. This approach represents a valuable surgical corridor to access various compartments and safely address several intracranial pathologies, both intradurally and extradurally, including tumors of the olfactory groove in the anterior cranial fossa (ACF), cavernous sinus in the middle cranial fossa (MCF), and the cerebellopontine angle in the posterior cranial fossa (PCF). The TOA exists in many variants, both from the point of view of invasiveness and from that of the entry point to the orbit, corresponding to the four orbital quadrants: the superior eyelid crease (SLC), the precaruncular (PC), the lateral retrocanthal (LRC), and the preseptal lower eyelid (PS). Moreover, multiportal variants, consisting of the combination of the transorbital approach with others, exist and are relevant to reach peculiar surgical territories. The significance of the TOA in neurosurgery, coupled with the dearth of thorough studies assessing its various applications and adaptations, underscores the necessity for this research. This extensive review delineates the multitude of target lesions reachable through the transorbital route, categorizing them based on surgical complexity. Furthermore, it provides an overview of the different transorbital variations, both standalone and in conjunction with other techniques. By offering a comprehensive understanding, this study aims to enhance awareness and knowledge regarding the current utility of the transorbital approach in neurosurgery. Additionally, it aims to steer future investigations toward deeper exploration, refinement, and exploration of additional perspectives concerning this surgical method.

Transorbital approach to the cavernous sinus: an anatomical study of the related cranial nerves

Background

The cavernous sinus (CS) is a demanding surgical territory, given its deep location and the involvement of multiple neurovascular structures. Subjected to recurrent discussion on the optimal surgical access, the endoscopic transorbital approach has been recently proposed as a feasible route for selected lesions in the lateral CS. Still, for this technique to safely evolve and consolidate, a comprehensive anatomical description of involved cranial nerves, dural ligaments, and arterial relations is needed.

Objective

Detailed anatomical description of the CS, the course of III, IV, VI, and V cranial nerves, and C3-C7 segments of the carotid artery, all described from the ventrolateral endoscopic transorbital perspective.

Methods

Five embalmed human cadaveric heads (10 sides) were dissected. An endoscopic transorbital approach with lateral orbital rim removal, anterior clinoidectomy, and petrosectomy was performed. The course of the upper cranial nerves was followed from their apparent origin in the brainstem, through the middle fossa or cavernous sinus, and up to their entrance to the orbit. Neuronavigation was used to follow the course of the nerves and to measure their length of surgical exposure.

Results

The transorbital approach allowed us to visualize the lateral wall of the CS, with cranial nerves III, IV, V1-3, and VI. Anterior clinoidectomy and opening of the frontal dura and the oculomotor triangle revealed the complete course of the III nerve, an average of 37 (±2) mm in length. Opening the trigeminal pore and cutting the tentorium permitted to follow the IV nerve from its course around the cerebral peduncle up to the orbit, an average of 54 (±4) mm. Opening the infratrochlear triangle revealed the VI nerve intracavernously and under Gruber's ligament, and the extended petrosectomy allowed us to see its cisternal portion (27 ± 6 mm). The trigeminal root was completely visible and so were its three branches (46 ± 2, 34 ± 3, and 31 ± 1 mm, respectively).

Conclusion

Comprehensive anatomic knowledge and extensive surgical expertise are required when addressing the CS. The transorbital corridor exposes most of the cisternal and the complete cavernous course of involved cranial nerves. This anatomical article helps understanding relations of neural, vascular, and dural structures involved in the CS approach, essential to culminating the learning process of transorbital surgery.

Transorbital Exposure of the Internal Carotid Artery: A Detailed Anatomic and Quantitative Roadmap for Safe Successful Surgery

BACKGROUND AND OBJECTIVES

The superior eyelid endoscopic transorbital approach has rapidly gained popularity among neurosurgeons for its advantages in the treatment, in a minimally invasive fashion, of a large variety of skull base pathologies. In this study, an anatomic description of the internal carotid artery (ICA) is provided to identify risky zones related to lesions that may be approached using this technique. In this framework, a practical roadmap can help the surgeon to avoid potentially life-threatening iatrogenic vascular injuries.

METHODS

Eight embalmed adult cadaveric specimens (16 sides) injected with a mixture of red latex and iodinate contrast underwent superior eyelid transorbital endoscopic approach, followed by interdural dissection of the cavernous sinus, extradural anterior clinoidectomy, and anterior petrosectomy, to expose the entire "transorbital" pathway of the ICA. Furthermore, the distance of each segment of the ICA explored by means of the superior eyelid endoscopic transorbital approach was quantitatively analyzed using a neuronavigation system.

RESULTS

We exposed 4 distinct ICA segments and named the anatomic window in which they are displayed in accordance with the cavernous sinus triangles distribution of the middle cranial fossa: (1) clinoidal (Dolenc), (2) infratrochlear (Parkinson), (3) anteromedial (Mullan), and (4) petrous (Kawase). Critical anatomy and key surgical landmarks were defined to further identify the main danger zones during the different steps of the approach.

CONCLUSION

A detailed knowledge of the reliable surgical landmarks of the course of the ICA as seen through an endoscopic transorbital route and its relationship with the cranial nerves are essential to perform a safe and successful surgery.

Endoscopic transorbital and transcranial multiportal resection of a sphenoorbital meningiomas with custom bone 3D printing reconstruction: Case report

BACKGROUND

Sphenoorbital meningiomas (SOM) harbor intrinsic features that render their surgical management and the reconstruction of the resulting bony defect overtly challenging.

METHODS

A 70-year-old woman, harboring a long-standing left frontotemporal bony swelling conservatively managed, presented with progressive left proptosis. Radiological features were consistent with an en plaque SOM. A one-step multiportal transcranial and endoscopic transorbital approach (TOA) with custom bone three-dimensional (3D) printing reconstruction using polymethylmethacrylate (PMMA) was scheduled.

RESULTS

Postoperative functional and aesthetic results were excellent, with proptosis and calvarian deformity resolution. Tumor subtotal resection was achieved. Histopathological diagnosis confirmed a transitional meningioma (WHO grade I).

CONCLUSIONS

The endoscopic TOA, isolated or as part of a multiportal strategy, has entered the surgical armamentarium for the treatment of SOMs. A customized PMMA cranioplasty can be considered a possible option for the reconstruction of large bony defects in a one-step fashion.

Transorbital Route to Intracranial Space

The endoscopic superior eyelid transorbital approach has emerged as a notable and increasingly utilized surgical technique in recent years. This chapter presents an overview of the approach, tracing its historical development and highlighting its growing acceptance within the skull base community.Beginning with an introduction and historical perspective, the chapter outlines the evolution of the transorbital approach, shedding light on its origins and the factors driving its adoption. Subsequently, a comprehensive exploration of the anatomic bone pillars and intracranial spaces accessible via this approach is provided. Hence, five bone pillars of the transorbital approach were identified, namely the lesser sphenoid wing, the anterior clinoid, the sagittal crest, the middle cranial fossa, and the petrous apex. A detailed correlation of those bone targets with respective intracranial areas has been reported.Furthermore, the chapter delves into the practical application of the technique through a case example, offering insights into its clinical utility, indications, and limitations.

Transorbital and supraorbital uniportal multicorridor approach to the orbit, anterior, middle and posterior cranial fossa: Anatomic study

Introduction

The transorbital route has been proposed for addressing orbital and paramedian skull base lesions. It can be complemented by further marginotomies, as per "extended-transorbital approach" and combined with others ventro-basal approaches featuring the concept of "multiportal surgery". Nevertheless, it cannot address some anatomical regions like the clinoid, carotid bifurcation and the Sylvian fissure. Therefore, we propose a combined transorbital and a supraorbital approach, attainable by a single infra-brow incision, and we called it "Uniportal multicorridor" approach.

Research question

The aim of our study is to verify its feasibility and deep anatomical targets through a cadaveric study.

Materials and methods

Anatomic dissections were performed at the Laboratory of ICLO Teaching and Research Center (Verona, Italy) on four formalin-fixed cadaveric heads injected with colored neoprene latex (8 sides). A stepwise dissection of the supraorbital and transorbital approaches (with an infra-brow skin incision) to the anterior tentorial incisura, clinoid area, lateral wall of the cavernous sinus, middle temporal fossa, posterior fossa, and Sylvian fissure is described.

Results

We analyzed the anatomic areas reached by the transorbital corridor dividing them as follow: lateral wall of the cavernous sinus, middle temporal fossa, posterior fossa, and Sylvian fissure; while the anatomic areas addressed by the supraorbital craniotomy were the clinoid area and the anterior tentorial incisura.

Conclusions

The described uniportal multi-corridor approach combines a transorbital corridor and a supraorbital craniotomy, providing a unique intra and extradural control over the anterior, middle, and posterior fossa, tentorial incisura and the Sylvian fissure, via an infra-brow skin incision.

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.

The anterolateral triangle as window on the foramen lacerum from transorbital corridor: anatomical study and technical nuances

OBJECTIVE

Neurosurgical indications for the superior eyelid transorbital endoscopic approach (SETOA) are rapidly expanding over the last years. Nevertheless, as any new technique, a detailed knowledge of the anatomy of the surgical target area, the operative corridor, and the specific surgical landmark from this different perspective is required for a safest and successful surgery. Therefore, the aim of this study is to provide, through anatomical dissections, a detailed investigation of the surgical anatomy revealed by SETOA via anterolateral triangle of the middle cranial fossa. We also sought to define the relevant surgical landmarks of this operative corridor.

METHODS

Eight embalmed and injected adult cadaveric specimens (16 sides) underwent dissection and exposure of the cavernous sinus and middle cranial fossa via superior eyelid endoscopic transorbital approach. The anterolateral triangle was opened and its content exposed. An extended endoscopic endonasal trans-clival approach (EEEA) with exposure of the cavernous sinus content and skeletonization of the paraclival and parasellar segments of the internal carotid artery (ICA) was also performed, and the anterolateral triangle was exposed. Measurements of the surface area of this triangle from both surgical corridors were calculated in three head specimens using coordinates of its borders under image-guide navigation.

RESULTS

The drilling of the anterolateral triangle via SETOA unfolds a space that can be divided by the course of the vidian nerve into two windows, a wider "supravidian" and a narrower "infravidian," which reveal different anatomical corridors: a "medial supravidian" and a "lateral supravidian," divided by the lacerum segment of the ICA, leading to the lower clivus, and to the medial aspect of the Meckel's cave and terminal part of the horizontal petrous ICA, respectively. The infravidian corridor leads medially into the sphenoid sinus. The arithmetic means of the accessible surface area of the anterolateral triangle were 45.48 ± 3.31 and 42.32 ± 2.17 mm2 through transorbital approach and endonasal approach, respectively.

CONCLUSION

SETOA can be considered a minimally invasive route complementary to the extended endoscopic endonasal approach to the anteromedial aspect of the Meckel's cave and the foramen lacerum. The lateral loop of the trigeminal nerve represents a reliable surgical landmark to localize the lacerum segment of the ICA from this corridor. Nevertheless, as any new technique, a learning curve is needed, and the clinical feasibility should be proven.

Transorbital transposition of the temporoparietal fascia flap to reconstruct the skull base defects: A preclinical study with comparison to the transpterygoid transposition

BACKGROUND

Transpterygoid transposition of the temporoparietal fascia flap (TPFF) is a feasible selection for ventral skull base defect (VSBD) reconstruction, but not anterior skull base defect (ASBD) reconstruction, after expanded endoscopic endonasal approach (EEEA). The goal of this study is to introduce the transorbital transposition of the TPFF for skull base defects reconstruction after EEEA, and make quantitative comparison between the transpterygoid transposition and transorbital transposition.

METHODS

Cadaveric dissections were performed in five adult cadaveric heads with creating three transporting corridors bilaterally, encompassing superior transorbital corridor, inferior transorbital corridor, and transpterygoid corridor. For each transporting corridor, the minimum necessary length of the TPFF for skull base defects reconstruction was measured.

RESULTS

The areas of ASBD and VSBD were 1019.63 ± 176.32 mm2 and 572.99 ± 126.21 mm2 . The length of the harvested TPFF was 149.38 ± 6.21 mm. In contrast to the transpterygoid transposition with incomplete coverage, transorbital transposition of the TPFF allowed full coverage of ASBD with a minimum necessary length of 109.75 ± 8.31 mm. For VSBD reconstruction, transorbital transposition of the TPFF needs shorter minimum necessary length (123.88 ± 4.49 mm) than transpterygoid transposition (138.00 ± 6.28 mm).

CONCLUSIONS

Transorbital corridor is a novel pathway for transporting the TPFF into the sinonasal cavity for skull base defects reconstruction after EEEA. In comparison with transpterygoid transposition, transorbital transposition provides wider coverage of skull base defects with a fixed length of the TPFF.

A New Perspective on the Cavernous Sinus as Seen through Multiple Surgical Corridors: Anatomical Study Comparing the Transorbital, Endonasal, and Transcranial Routes and the Relative Coterminous Spatial Regions

Background: The cavernous sinus (CS) is a highly vulnerable anatomical space, mainly due to the neurovascular structures that it contains; therefore, a detailed knowledge of its anatomy is mandatory for surgical unlocking. In this study, we compared the anatomy of this region from different endoscopic and microsurgical operative corridors, further focusing on the corresponding anatomic landmarks encountered along these routes. Furthermore, we tried to define the safe entry zones to this venous space from these three different operative corridors, and to provide indications regarding the optimal approach according to the lesion's location. Methods: Five embalmed and injected adult cadaveric specimens (10 sides) separately underwent dissection and exposure of the CS via superior eyelid endoscopic transorbital (SETOA), extended endoscopic endonasal transsphenoidal-transethmoidal (EEEA), and microsurgical transcranial fronto-temporo-orbito-zygomatic (FTOZ) approaches. The anatomical landmarks and the content of this venous space were described and compared from these surgical perspectives. Results: The oculomotor triangle can be clearly exposed only by the FTOZ approach. Unlike EEEA, for the exposure of the clinoid triangle content, the anterior clinoid process removal is required for FTOZ and SETOA. The supra- and infratrochlear as well as the anteromedial and anterolateral triangles can be exposed by all three corridors. The most recently introduced SETOA allowed for the exposure of the entire lateral wall of the CS without entering its neurovascular structures and part of the posterior wall; furthermore, thanks to its anteroposterior trajectory, it allowed for the disclosure of the posterior ascending segment of the cavernous ICA with the related sympathetic plexus through the Mullan's triangle, in a minimally invasive fashion. Through the anterolateral triangle, the transorbital corridor allowed us to expose the lateral 180 degrees of the Vidian nerve and artery in the homonymous canal, the anterolateral aspect of the lacerum segment of the ICA at the transition zone from the petrous horizontal to the ascending posterior cavernous segment, surrounded by the carotid sympathetic plexus, and the medial Meckel's cave. Conclusions: Different regions of the cavernous sinus are better exposed by different surgical corridors. The relationship of the tumor with cranial nerves in the lateral wall guides the selection of the approach to cavernous sinus lesions. The transorbital endoscopic approach can be considered to be a safe and minimally invasive complementary surgical corridor to the well-established transcranial and endoscopic endonasal routes for the exposure of selected lesions of the cavernous sinus. Nevertheless, peer knowledge of the anatomy and a surgical learning curve are required.

Transuncal Selective Amygdalohippocampectomy by an Inferolateral Preseptal Endoscopic Approach Through Inferior Eyelid Conjunctival Incision: An Anatomic Study

BACKGROUND

Transorbital endoscopic approaches have been described for pathologies of anterior and middle fossae. Standard lateral orbitotomy gives access to mesial temporal lobe, but the axis of work is partially obscured by the temporal pole and working corridor is limited.

OBJECTIVE

To evaluate the usefulness of an inferolateral orbitotomy to provide a more direct corridor to perform a transuncal selective amygdalohippocampectomy.

METHODS

Three adult cadaveric specimens were used for a total of 6 dissections. A step-by-step description and illustration of the transuncal corridor for a selective amygdalohippocampectomy were performed using the inferolateral orbitotomy through an inferior eyelid conjunctival incision. The anatomic landmarks were demonstrated in detail. Orbitotomies and angles of work were measured from computed tomography scans, and the area of resection was illustrated by postdissection MRI.

RESULTS

Inferior eyelid conjunctival incision was made for exposure of the inferior orbital rim. Inferolateral transorbital approach was performed to access the transuncal corridor. Endoscopic selective amygdalohippocampectomy was performed through the entorhinal cortex without damage to the temporal neocortex or Meyer's loop. The mean horizontal diameter of the osteotomy was 14.4 mm, and the vertical one was 13.6 mm. The mean angles of work were 65° and 35.5° in the axial and sagittal planes, respectively. Complete amygdalohippocampectomy was achieved in all 6 dissections.

CONCLUSION

Transuncal selective amygdalohippocampectomy was feasible in cadaveric specimens using the inferolateral transorbital endoscopic approach avoiding damage to the temporal neocortex and Meyer's loop. The inferior eyelid conjunctival incision may result in an excellent cosmetic outcome.

Cadaveric analysis of transcranial versus endoscopic transorbital petrosectomy: comparison of surgical maneuverability and brainstem exposure

Introduction

While accessing the posterior fossa, the anterior transpetrosal approach (ATPA) and endoscopic transorbital approach (ETOA) use the same bony landmarks during petrous apex drilling. However, owing to their contrasting surgical axes, they are expected to show differences in surgical view, maneuverability, and clinical implications. This study aimed to investigate the feasibility of ETOA in accessing the brainstem and to compare the surgical view and maneuverability of each approach.

Methods

ATPA and ETOA were performed in four human cadaveric heads (eight sides and four sides in each procedure). The angle of attack (AOA) and surgical depth were measured at the target of interest (root exit zone [REZ] of cranial nerve [CN] V, VI, and VII). When measuring the area of exposure, the brainstem was divided into two areas (anterior and lateral brainstem) based on the longitudinal line crossing the entry zone of the trigeminal root, and the area of each was measured.

Results

ATPA showed significantly greater value at the trigeminal REZ in both vertical (31.8 ± 6.7° vs. 14.3 ± 5.3°, p=0.006) and horizontal AOA (48.5 ± 2.9° vs. 15.0 ± 5.2°, p<0.001) than ETOA. The AOA at facial REZ was also greater in ATPA than ETOA (vertical, 27.5 ± 3.9° vs. 8.3 ± 3.3°, p<0.001; horizontal, 33.8 ± 2.2° vs. 11.8 ± 2.9°, p<0.001). ATPA presented significantly shorter surgical depth (CN V, 5.8 ± 0.5 cm vs. 9.0 ± 0.8, p<0.001; CN VII, 6.3 ± 0.5 cm vs. 9.5 ± 1.0, p=0.001) than ETOA. The mean area of brainstem exposure did not differ between the two approaches. However, ATPA showed significantly better exposure of anterior brainstem than ETOA (240.7 ± 9.6 mm² vs. 171.7 ± 15.0 mm², p<0.001), while ETOA demonstrated better lateral brainstem exposure (174.2 ± 29.1 mm² vs. 231.1 ± 13.6 mm², p=0.022).

Conclusions

ETOA could be a valid surgical option, in selected cases, that provides a direct ventral route to the brainstem. Compared with ATPA, ETOA showed less surgical maneuverability, AOA and longer surgical depth; however, it presented comparable brainstem exposure and better exposure of the lateral brainstem.

Comparison of Accessibility to Cavernous Sinus Areas Throughout Endonasal, Transorbital, and Transcranial Approaches: Anatomic Study With Quantitative Analysis

BACKGROUND

The cavernous sinus (CS) is accessed through several approaches, both transcranially and endoscopically. The transorbital endoscopic approach is the newest proposed route in the literature.

OBJECTIVE

To quantify and observe the areas of the CS reach from 2 endoscopic and 1 transcranial approaches to the CS in the cadaver laboratory.

METHODS

Six CSs were dissected through endoscopic endonasal, transorbital endoscopic, and transcranial pterional approaches, with previous implanted references for neuronavigation during the dissection. Point registration was used to mark the CS exposure and limits through each approach for later area and volume quantification through a computerized technique.

RESULTS

The endoscopic endonasal approach reaches most of the CS except part of the sinus's superior, lateral, and posterior regions. The area exposed through this approach was 210 mm 2 , and the volume was 1165 mm 3 . The transcranial pterional approach reached the superior and part of the lateral sides of the sinus, not allowing good access to the medial side. The area exposed through this approach was 306 m 2 , whereas the volume was 815 m 3 . Finally, the transorbital endoscopic approach accessed the whole lateral side of the sinus but not the medial one. The area exposed was the greatest, 374 m 2 , but its volume was the smallest, 754 m 3 .

CONCLUSION

According to our results, the endonasal endoscopic approach is the direct route to access the medial, inferior, and part of the superior CS compartments. The transorbital approach is for the lateral side of the CS. Finally, the transcranial pterional approach is the one for the superior side of the CS.

The feasibility of three port endonasal, transorbital, and sublabial approach to the petroclival region: neurosurgical audit and multiportal anatomic quantitative investigation

PURPOSE

The petroclival region represents the "Achille's heel" for the neurosurgeons. Many ventral endoscopic routes to this region, mainly performed as isolated, have been described. The aim of the present study is to verify the feasibility of a modular, combined, multiportal approach to the petroclival region to overcome the limits of a single approach, in terms of exposure and working areas, brain retraction and manipulation of neurovascular structures.

METHODS

Four cadaver heads (8 sides) underwent endoscopic endonasal transclival, transorbital superior eyelid and contralateral sublabial transmaxillary-Caldwell-Luc approaches, to the petroclival region. CT scans were obtained before and after each approach to rigorously separate the contribution of each osteotomy and subsequentially to build a comprehensive 3D model of the progressively enlarged working area after each step.

RESULTS

The addition of the contralateral transmaxillary and transorbital corridors to the extended endoscopic endonasal transclival in a combined multiportal approach provides complementary paramedian trajectories to overcome the natural barrier represented by the parasellar and paraclival segments of the internal carotid artery, resulting in significantly greater area of exposure than a pure endonasal midline route (8,77 cm² and 11,14 cm² vs 4,68 cm² and 5,83cm², extradural and intradural, respectively).

CONCLUSION

The use of different endoscopic "head-on" trajectories can be combined in a wider multiportal extended approach to improve the ventral route to the most inaccessible petroclival regions. Finally, by combining these approaches and reiterating the importance of multiportal strategy, we quantitatively demonstrate the possibility to reach "far away" paramedian petroclival targets while preserving the neurovascular structures.

Functional and clinical outcomes after superior eyelid transorbital endoscopic approach for spheno-orbital meningiomas: illustrative case and literature review

The pattern of growth of spheno-orbital meningiomas accounts for the main presenting symptoms, such as proptosis, eye motility deficit, visual impairment, diplopia. As these are benign tumors, the postoperative patient's quality of life is an important factor to consider during the preoperative planning. A detailed literature review of superior eyelid transorbital endoscopic approach for spheno-orbital meningiomas, including our own case, was made. A Medline search up to March 2022 in PubMed online electronic database was made using the following key phrases: "superior eyelid endoscopic transorbital approach spheno-orbital meningiomas," "superior eyelid endoscopic transorbital approach," "spheno-orbital meningiomas endoscopic approach." The inclusion criteria were surgical series, reviews, and case reports in English language, as well as papers written in other languages, but including the abstract in English. Cadaveric studies, multiportal combined approaches for SOM, were excluded. The literature review has disclosed five studies for a total of 65 patients, whose demographic, clinical, pathological, surgical, complications, and outcome data were analyzed. Functional and esthetic outcome data after superior eyelid transorbital approach are the following: improvement of proptosis (100%), of visual deficits (66.66%) and of ocular paresis (75%), with only 11 complications (4 trigeminal dysesthesia, 2 CSF leak, 2 wound complications, 1 upper eyelid necrosis, 1 hemorrhage of surgical field, 1 keratitis) reported, but at the expense of extent of resection (gross total resection 33.39%). Based on the outcome data, the superior eyelid transorbital endoscopic approach results in a suitable operative technique for selected spheno-orbital meningiomas.

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.

Superior eyelid endoscopic transorbital approach to the tentorial area: A qualitative and quantitative anatomic study

Objective

Superior eyelid endoscopic transorbital approach (SETOA) is nowadays gaining progressive application in neurosurgical scenarios. Both anatomic and clinical reports have demonstrated the possibility of taking advantage of the orbital corridor as a minimally invasive route to reach anterior and middle cranial fossae and manage selected surgical lesions developing in these areas. The aim of this paper is to further shed light on other anatomic regions of the skull base as seen from a transorbital perspective, namely, the posterior cranial fossa and tentorial area, describing technical feasibility and steps in reaching this area through an extradural-transtentorial approach and providing quantitative evaluations of the "working area" obtained through this route.

Material and methods

Four cadaveric heads (eight sides) were dissected at the Laboratory of Surgical Neuroanatomy (LSNA) of the University of Barcelona, Spain. A stepwise dissection of the transorbital approach to the tentorial area was described. Qualitative anatomical descriptions and quantitative analyses of working were evaluated by using pre- and postdissections CT and MRI scans, and three-dimensional reconstructions were made using Amira software.

Results

With the endoscopic transorbital approach, posterior cranial fossa dura was reached by an extradural middle cranial fossa approach and drilling of the petrous apex. After clipping the superior petrosal sinus, the tentorium was divided and cut. An endoscope was then introduced in the posterior cranial fossa at the level of the tentorial incisura. Qualitative analysis provided a description of the tentorial and petrosal surfaces of the cerebellum, middle tentorial incisura, cerebellopontine fissures, and, after arachnoid dissection, by a 30° endoscopic visualization, the posterior aspect of the cerebellomesencephalic fissure. Quantitative analysis of the "working area" obtained after bone removal was also provided.

Conclusions

This anatomic qualitative and quantitative study sheds light on the anatomy of the posterior cranial fossa contents, such as the tentorial area and incisura, as seen through a transorbital perspective. The first aim of the article is to enrich the anatomical knowledge as seen through this relatively new corridor and to provide quantitative details and insights into the technical feasibility of reaching these regions in a surgical scenario.

Endoscopic Transorbital Approach to the Middle Fossa: Qualitative and Quantitative Anatomic Study

BACKGROUND

The endoscopic superior eyelid transorbital route to the skull base is gaining progressive popularity in the neurosurgical community.

OBJECTIVE

To evaluate the anatomy of the middle cranial fossa from this novel ventral perspective to reach the skull base through the transorbital route and to show limits for possible safe middle fossa drilling from the transorbital route.

METHODS

Anatomic study was performed; 5 cadaveric specimens (ie, 10 sides) and 2 dry skulls (ie, 4 sides) were dissected.

RESULTS

To obtain a functional result, there are boundaries that correspond to neurovascular structures that traverse, enter, or leave the middle fossa that must be respected: inferiorly, the lateral pterygoid muscle; medially, the Gasserian ganglion and the lateral border of the foramen rotundum; laterally, the foramen spinosum with the middle meningeal artery; superiorly, the lesser sphenoid wing; posteriorly, the anterior border of the foramen ovale. Average bone resected was 6.49 ± 0.80 cm3 which is the 63% of total middle fossa floor. The mean axial surgical length calculated was 3.85 cm (3.18-5.19 cm) while the mean sagittal surgical length was 5.23 cm (4.87-6.55 cm). The mean horizontal angle of approach was 38.14° (32.87°-45.63°), while the mean vertical angle of approach was 18.56° (10.81°-26.76°).

CONCLUSION

Detailed anatomy of the middle cranial fossa is presented, and herewith we demonstrated that from the endoscopic superior eyelid transorbital approach removal of middle cranial fossa floor is possible when anatomic landmarks are respected.

Endoscopic transorbital avenue to the skull base: Four-step conceptual analysis of the anatomic journey

Background

In the last decades, skull base surgery had passed through an impressive evolution. The role of neuroanatomic research has been uppermost, and it has played a central role in the development of novel techniques directed to the skull base. Indeed, the deep and comprehensive study of skull base anatomy has been one of the keys of success of the endoscopic endonasal approach to the skull base. In the same way, dedicated efforts expended in the anatomic lab has been a powerful force for the growth of the endoscopic transorbital approach to the lateral skull base.

Therefore, in this conceptual paper, the main steps for the anatomic description of the endoscopic transorbital approach to the skull base have been detailed.

Methods

The anatomic journey for the development of the endoscopic transorbital approach to the skull base has been analyzed, and four “conceptual” steps have been highlighted.

Results

As neurosurgeons, the eyeball has always represented a respectful area: to become familiar with this complex and delicate anatomy, we started by examining the orbital anatomy on a dry skull (step 1). Hence, step 1 is represented by a detailed bone study; step 2 is centered on cadaveric dissection; step 3 consists in 3D quantitative assessment of the novel endoscopic transorbital corridor; and finally, step 4 is the translation of the preclinical data in the real surgical scenario by means of dedicated surgical planning.

Conclusions

The conceptual analysis of the anatomic journey for the description of the endoscopic transorbital approach to the skull base resulted in four main methodological steps that should not be thought strictly consequential but rather interconnected. Indeed, such steps should evolve following the drives that can arise in each specific situation. In conclusion, the four-step anatomic rehearsal can be relevant for the description, diffusion, and development of a novel technique in order to facilitate the application of the endoscopic transorbital approach to the skull base in a real surgical scenario.

Endoscopic transorbital eyelid approach for the removal of an extraconal cavernous venous malformation: Case report

Cavernous venous malformations (CVMs) are one of the most common benign primary orbital lesions in adults and the second most frequent cause of unilateral proptosis. Extraconal location is extremely rare, representing a favorable condition as compared to intraconal, as lesions at this level often adhere to orbital muscles and optic nerve. Herein, we report the case of a 50-year-old patient, who came to our attention because of progressive painless right axial proptosis. Magnetic resonance images were consistent with an extraconal CVM, occupying the superior temporal compartment of the orbit. Successful removal of the lesion was achieved through an endoscopic transorbital eyelid approach. The present case confirms the safety and efficacy of the endoscopic transorbital eyelid approach.

Extended endoscopic transorbital approach with superior-lateral orbital rim osteotomy: cadaveric feasibility study and clinical implications (SevEN-007)

OBJECTIVE

The endoscopic transorbital approach (ETOA) has been developed, permitting a new surgical corridor. Due to the vertical limitation of the ETOA, some lesions of the anterior cranial fossa are difficult to access. The ETOA with superior-lateral orbital rim (SLOR) osteotomy can achieve surgical freedom of vertical as well as horizontal movement. The purpose of this study was to confirm the feasibility of the ETOA with SLOR osteotomy.

METHODS

Anatomical dissections were performed in 5 cadaveric heads with a neuroendoscope and neuronavigation system. ETOA with SLOR osteotomy was performed on one side of the head, and ETOA with lateral orbital rim (LOR) osteotomy was performed on the other side. After analysis of the results of the cadaveric study, the ETOA with SLOR osteotomy was applied in 6 clinical cases.

RESULTS

The horizontal and vertical movement range through ETOA with SLOR osteotomy (43.8° ± 7.49° and 36.1° ± 3.32°, respectively) was improved over ETOA with LOR osteotomy (31.8° ± 5.49° and 23.3° ± 1.34°, respectively) (p < 0.01). Surgical freedom through ETOA with SLOR osteotomy (6025.1 ± 220.1 mm3) was increased relative to ETOA with LOR osteotomy (4191.3 ± 57.2 mm3) (p < 0.01); these values are expressed as the mean ± SD. Access levels of ETOA with SLOR osteotomy were comfortable, including anterior skull base lesion and superior orbital area. The view range of the endoscope for anterior skull base lesions was increased through ETOA with SLOR osteotomy. After SLOR osteotomy, the space for moving surgical instruments and the endoscope was widened. Anterior clinoidectomy could be achieved successfully using ETOA with SLOR osteotomy. The authors performed ETOA with SLOR osteotomy in 6 cases of brain tumor. In all 6 cases, complete removal of the tumor was successfully accomplished. In the 3 cases of anterior clinoidal meningioma, anterior clinoidectomy was performed easily and safely, and manipulation of the extended dural margin and origin dura mater was possible. There was no complication related to this approach.

CONCLUSIONS

The authors evaluated the clinical feasibility of ETOA with SLOR osteotomy based on a cadaveric study. ETOA with SLOR osteotomy could be applied to more diverse disease groups that do not permit conventional ETOA or to cases in which surgical application is challenging. ETOA with SLOR osteotomy might serve as an opportunity to broaden the indication for the ETOA.

Endoscopic endonasal and transorbital approaches to petrous apex lesions

OBJECTIVE

The petrous apex (PA) is one of the most challenging areas in skull base surgery because it is surrounded by numerous critical neurovascular structures. The authors analyzed the clinical outcomes of patients who underwent endoscopic endonasal approach (EEA) and transorbital approach (TOA) procedures for lesions involving PA to determine the perspectives and proper applications of these two approaches.

METHODS

The authors included patients younger than 80 years with lesions involving PA who were treated between May 2015 and December 2019 and had regular follow-up MR images available for analysis. Patients with meningioma involving petroclival regions were excluded. The authors classified PA into three regions: superior to the petrous segment of the internal carotid artery (p-ICA) (zone 1); posterior to p-ICA (zone 2); and inferior to p-ICA (zone 3). Demographic data, preoperative clinical and radiological findings, surgical outcomes, and morbidities were reviewed.

RESULTS

A total of 19 patients with lesions involving PA were included. Ten patients had malignant tumor (chondrosarcoma, chordoma, and osteosarcoma), and 6 had benign tumor (schwannoma, Cushing's disease, teratoma, etc.). Three patients had PA cephalocele (PAC). Thirteen patients underwent EEA, and 5 underwent TOA. Simultaneous combined EEA and TOA was performed on 1 patient. Thirteen of 16 patients (81.3%) had gross- or near-total resection. Tumors within PA were completely resected from 13 of 16 patients using a view limited to only the PA. Complete obliteration of PAC was achieved in all patients. Postoperative complications included 2 cases of CSF leak, 1 case of injury to ICA, 1 fatality due to sudden herniation of the brainstem, and 1 case of postoperative diplopia.

CONCLUSIONS

EEA is a versatile surgical approach for lesions involving all three zones of PA. Clival tumor spreading to PA in a medial-to-lateral direction is a good indication for EEA. TOA provided a direct surgical corridor to the superior portion of PA (zone 1). Patients with disease with cystic nature are good candidates for TOA. TOA may be a reasonable alternative surgical treatment for select pathologies involving PA.

Clinical applications of the endoscopic transorbital approach for various lesions

BACKGROUND

The endoscopic transorbital approach (ETOA) was recently added to the neurosurgical armamentarium. Although this approach could result in less injury to normal brain tissue, shorter operation times, and smaller scars, its clinical applications have not been fully investigated. We, therefore, sought to share our unique experiences of exploring the application of this approach in various diseases.

METHODS

From June 2017 to March 2019, we conducted ETOAs via the superior eyelid crease in 22 patients for the treatment of lesions confined to the middle fossa with and without slight extension to the posterior fossa. These lesions included 5 gliomas, 11 meningiomas, 3 schwannomas, 1 lymphoma, 1 cavernous hemangioma in the orbital wall, and 1 hemangiopericytoma mimicking schwannoma. Perioperative radiologic findings and clinical outcomes were recorded.

RESULTS

Gross total resection was accomplished in three (60%) patients with gliomas, nine (81.8%) with meningiomas, two (66.7%) with schwannomas, and one (33.3%) with another lesion. The mean bleeding count was 1051.4 ± 961.1 cc, and major complications were observed in only two (9.1%) cases (one major cerebral artery infarction and one reoperation due to a large amount of bleeding). A cerebrospinal fluid leak was reported in two (9.1%) patients, and transient eye movement palsy was noted in four (18.2%) patients without permanent disability.

CONCLUSIONS

The endoscopic transorbital approach could be considered to be feasible for various lesions with different characteristics. After carefully considering the lesion anatomy, consistency, and vascular relationships, using this approach, we could achieve a satisfactory extent of resection without severe complications.

Combined and simultaneous endoscopic endonasal and transorbital surgery for a Meckel's cave schwannoma: technical nuances of a mini-invasive, multiportal approach

OBJECTIVE

Over the years, Meckel's cave pathologies have been judged off-limits because of high rates of morbidity. Even though several studies have defined various surgical routes with tolerable morbidity and mortality rates, controversies related to the optimal avenue to treat different categories of Meckel's cave and cavernous sinus neoplasms persist. With unceasing energy to cultivate minimally invasive neurosurgical approaches, the endoscopic endonasal route has been tested, and the approach effectively performed, to provide a valid surgical window to these areas. In this dynamic and challenging scenario, another ventral endoscopic minimally invasive route-that is, the superior eyelid endoscopic transorbital approach-has been very recently proposed, and used in selected cases, to access the cavernous sinus and Meckel's cave regions.

METHODS

The authors report the technical nuances of a combined and simultaneous endoscopic endonasal and transorbital surgical treatment of a patient with a Meckel's cave schwannoma. The operation involved collaboration among neurosurgery, otorhinolaryngology, and ophthalmology (oculoplastic surgery). The patient recovered well, had no neurological deficits, and was discharged to home 3 days after surgery.

RESULTS

The multiportal combined route was proposed for the following reasons. The endonasal approach, considered to be more familiar to our skull base team, could allow control of possible damage of the internal carotid artery. From the endonasal perspective, the most inferior and medial portion of the tumor could be properly managed. Finally, the transorbital route, by means of opening the lateral wall of the cavernous sinus via the meningoorbital band, could allow control of the superolateral part of the tumor and, most importantly, could permit removal of the portion entering the posterior cranial fossa via the trigeminal pore. Simultaneous surgery with two surgical teams working together was planned in order to reduce operative time, hospital stay, and patient stress and discomfort, and to ensure "one-shot" complete tumor removal, with minimal or no complications.

CONCLUSIONS

This study represents the translation into the real surgical setting of recent anatomical contributions related to the novel endoscopic transorbital approach and its simultaneous integration with the endoscopic endonasal pathway. Accordingly, it may pave the way for future applications related to minimally invasive, multiportal endoscopic surgery for skull base tumors.

Endoscopic transorbital ligation of the maxillary artery through the inferior orbital fissure

OBJECTIVE

Determine the feasibility of accessing the internal maxillary artery (IMA) through a transorbital endoscopic assisted approach through the inferior orbital fissure (IOF).

MATERIALS AND METHODS

Six adult cadaveric specimens were injected intravascularly with colored latex and dissected on 12 sides. A transorbital endoscopic approach was used to expose the IOF and reach the IMA.

RESULTS

The average length and width of the anterolateral segment of the IOF were 7.3 and 4 mm, respectively, on the right side and 6.7 and 3.8 mm, respectively, on the left side. Surgical exposure and modification of the IOF allowed the exposure and control of the IMA in all 12 sides.

CONCLUSIONS

The IOF is a feasible portal to the IMA. The benefits of this approach include vascular control of the distal segment of the maxillary artery. It may provide access in clinical scenarios where endonasal access is not possible (e.g., extensive tumors) or serve as an alternative or complementary surgical route (e.g., control during a total or radical maxillectomy).

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.

Lateral transorbital approach: an alternative microsurgical route for supratentorial cerebral aneurysms

OBJECTIVE

Transorbital approaches for neurosurgery have recently attracted attention and several anatomical studies have aimed to improve these techniques, but significant deficiencies in clinical practice remain, especially for aneurysm surgery. The authors present an alternative microsurgical route and the results of an analysis of patients with intracranial aneurysms who underwent a lateral transorbital approach (LTOA) using lateral orbito-zygoma-sphenotomy (LOZYGS).

METHODS

The clinical and surgical results of a series of 54 consecutive patients with 1 or more aneurysms who underwent surgery via LTOA are reported. A lateral orbitotomy was performed after making a 3-cm skin incision parallel to the lateral orbital rim. A second bone flap, which included the zygoma and sphenoid bones that form the lateral orbital wall, was removed. The lesser sphenoid wing, including the anterior clinoid process, was fully drilled, except in cases of middle cerebral artery (MCA) aneurysms. Cisternal dissection was performed using the classic microsurgical technique starting from the proximal Sylvian fissure and carotid cistern. After the aneurysm was clipped following microsurgical principles, the dura mater was closed in a watertight fashion and 2-piece bone reconstruction was achieved.

RESULTS

Sixty aneurysms in 54 patients were clipped using the LOZYGS route. Twenty-one aneurysms were located on the MCA, 30 on the anterior communicating artery, 8 on the internal carotid artery, and 1 at the apex of the basilar artery. The unruptured-to-ruptured aneurysm ratio was 17:43. The operative field was moved to the orbit using the LTOA to avoid interference by bone and muscle tissues. Early proximal control was achieved using a short working distance and direct exposure of the base of the cerebrum, without any requirement for retraction. Because different view angles and surgical corridors were used, no segment of the aneurysm or the parent artery remained unexposed. Therefore, the introduction of additional tools was not required.

CONCLUSIONS

The LTOA allowed enhanced broad-perspective exposure of the operative field, early proximal control, and satisfactory surgical freedom. This alternative surgical approach safely exposed the target area and the operative field. The LOZYGS route is safe and effective for the LTOA and microsurgical clipping of anterior circulation aneurysms. According to the authors' surgical experience and clinical experience, the LTOA can be considered an alternative surgical route to supratentorial aneurysm surgery.

Endoscopic transorbital approach to the infratemporal fossa and parapharyngeal space: a cadaveric study

OBJECTIVE

The infratemporal fossa (ITF) and parapharyngeal space are anatomical regions that can be challenging to access without the use of complex, cosmetically disfiguring approaches. With advances in endoscopic techniques, a new group of surgical approaches to access the intracranial space through the orbit has been recently referred to as transorbital neuroendoscopic surgery (TONES). The objective of this study was to establish a transorbital endoscopic approach utilizing the inferior orbital fissure (IOF) to gain access to the ITF and parapharyngeal space and provide a detailed endoscopic anatomical description of this approach.

METHODS

Four cadaveric heads (8 sides) were dissected using a TONES approach through the IOF to reach the ITF and parapharyngeal space, providing stepwise dissection with detailed anatomical findings and a description of each step.

RESULTS

An inferior eyelid approach was made with subperiosteal periorbital dissection to the IOF. The zygomatic and greater wing of the sphenoid were drilled, forming the boundaries of the IOF. The upper head of the lateral pterygoid muscle in the ITF and parapharyngeal space was removed, and 7 distinct planes were described, each with its own anatomical contents. The second part of the maxillary artery was mainly found in plane 1 between the temporalis laterally and the lateral pterygoid muscle in plane 2. The branches of the mandibular nerve (V3) and middle meningeal artery (MMA) were identified in plane 3. Plane 4 was formed by the fascia of the medial pterygoid muscle (MTM) and the tensor veli palatini muscle. The prestyloid segment, found in plane 5, was composed mainly of fat and lymph nodes. The parapharyngeal carotid artery in the poststyloid segment, found in plane 7, was identified after laterally dissecting the styloid diaphragm, found in plane 6. V3 and the origin of the levator and tensor veli palatini muscles serve as landmarks for identification of the parapharyngeal carotid artery.

CONCLUSIONS

The transorbital endoscopic approach provides excellent access to the ITF and parapharyngeal space compared to previously described complex and morbid transfacial or transcranial approaches. Using the IOF is an important and useful landmark that permits a wide exposure.

A Case of Petrous Apex Meningocele: Unusual Presentation of Cerebrospinal Fluid Leak Following Adenoidectomy

Cerebrospinal fluid (CSF) leak is possible and can be a cause of recurrent bacterial meningitis. Petrous apex meningocele (PAM) is mostly asymptomatic and is often found during incidental imaging tests. We experienced a case of CSF rhinorrhea with recurrent meningitis in bilateral PAM after adenoidectomy. This report highlights the diagnostic process of CSF leak, identification of leakage site, and surgical approach to petrous apex lesions.

Quantitative comparison of endoscopically assisted endonasal, sublabial and transorbital transmaxillary approaches to the anterolateral skull base

OBJECTIVES

The aim of this anatomical study is to make quantitative comparison among three endoscopic approaches, encompassing contralateral endonasal transseptal transmaxillary transpterygoid approach (contralateral EEA), endoscopic sublabial transmaxillary transalisphenoid (Caldwell-Luc) approach and endoscopic transorbital transmaxillary approach through inferior orbital fissure (ETOA), to the anterolateral skull base for assisting preoperative planning.

DESIGN & PARTICIPANTS

Anatomical dissections were performed in four adult cadaveric heads bilaterally using three endoscopic transmaxillary approaches described above.

SETTING

Skull Base Laboratory at the National Defense Medical Center.

MAIN OUTCOME MEASURES

The area of exposure, angles of attack and depth of surgical corridor of each approach were measured and obtained for statistical comparison.

RESULTS

The ETOA had significantly larger exposure over middle cranial fossa (731.40 ± 80.08 mm² ) than contralateral EEA (266.60 ± 46.74 mm² ) and Caldwell-Luc approach (468.40 ± 59.67 mm² ). In comparison with contralateral EEA and Caldwell-Luc approach, the ETOA offered significantly greater angles of attack and shorter depth of surgical corridor (P < .05 for all comparisons).

CONCLUSIONS

The ETOA is the superior choice for target lesion occupying multiple compartments with its epicentre located in the middle cranial fossa or superior portion of infratemporal fossa.

Endoscopic transcanal transpetrosal approach to the petroclival region: a cadaveric study with comparison to the Kawase approach

This study introduces expanded application of the endoscopic transcanal approach with anterior petrosectomy (ETAP) in reaching the petroclival region, which was compared through a quantitative analysis to the middle fossa transpetrosal-transtentorial approach (Kawase approach). Anatomical dissections were performed in five cadaveric heads. For each head, the ETAP was performed on one side with a detailed description of each step, while the Kawase approach was performed on the contralateral side. Quantitative measurements of the exposed area over the ventrolateral surface of the brainstem, and of the angles of attack to the posterior margin of the trigeminal nerve root entry zone (CN V-REZ) and porus acusticus internus (PAI) were obtained for statistical comparison. The ETAP provided significantly larger exposure over the ventrolateral surface of the pons (93.03 ± 21.87 mm²) than did the Kawase approach (34.57 ± 11.78 mm²). In contrast to the ETAP, the Kawase approach afforded greater angles of attack to the CN V-REZ and PAI in the vertical and horizontal planes. The ETAP is a feasible and minimally invasive procedure for accessing the petroclival region. In comparison to the Kawase approach, the ETAP allows for fully anterior petrosectomy and larger exposure over the ventrolateral surface of the brainstem without passing through the cranial nerves or requiring traction of the temporal lobe.

Endoscopic endonasal and transorbital routes to the petrous apex: anatomic comparative study of two pathways

BACKGROUND AND OBJECTIVE

Surgical approaches to the petrous apex region are extremely challenging; while subtemporal approaches and variations represent the milestone of the surgical modules to reach such deep anatomical target, in a constant effort to develop minimally invasive neurosurgical routes, the endoscopic endonasal approach (EEA) has been tested to get a viable corridor to the petroclival junction. Lately, another ventral endoscopic minimally invasive route, i.e., the superior eyelid endoscopic transorbital approach, has been proposed to access the most lateral aspect of the skull base, including the petrous apex region. Our anatomic study aims to compare and combine such two endoscopic minimally invasive pathways to get full access to the petrous apex. Three-dimensional reconstructions and quantitative and morphometric data have been provided.

MATERIAL AND METHODS

Five human cadaveric heads (10 sides) were dissected. The lab rehearsals were run as follows: (i) preliminary pre-operative CT scans of each specimen, (ii) pre-dissection planning of the petrous apex removal and its quantification, (iii) petrous apex removal via endoscopic endonasal route, (iv) post-operative CT scans, (v) petrous apex removal via endoscopic transorbital route, and (v) final post-operative CT scan with quantitative analysis. Neuronavigation was used to guide all dissections.

RESULTS

The two endoscopic minimally invasive pathways allowed a different visualization and perspective of the petrous apex, and its surrounding neurovascular structures. After both corridors were completed, a communication between the surgical pathways was highlighted, in a so-called connection area, surrounded by the following important neurovascular structures: anteriorly, the internal carotid artery and the Gasserian ganglion; laterally, the internal acoustic canal; superiorly, the abducens nerve, the trigeminal root, and the tentorium cerebelli; inferomedially, the remaining clivus and the inferior petrosal sinus; and posteriorly, the exposed area of the brainstem. Used in a combined fashion, such multiportal approach provided a total of 97% of petrous apex removal. In particular, the transorbital route achieved a mean of 48.3% removal in the most superolateral portion of the petrous apex, whereas the endonasal approach provided a mean of 48.7% bone removal in the most inferomedial part. The difference between the two approaches was found to be not statistically significant (p = 0.67).

CONCLUSION

The multiportal combined endoscopic endonasal and transorbital approach to the petrous apex provides an overall bone removal volume of 97% off the petrous apex. In this paper, we highlighted that it was possible to uncover a common path between these two surgical pathways (endonasal and transorbital) in a so-called connection area. Potential indications of this multiportal approach may be lesions placed in or invading the petrous apex and petroclival regions that can be inadequately reached via transcranial paths or via an endonasal endoscopic route alone.

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.

Expanded exposure and detailed anatomic analysis of the superior orbital fissure: Implications for endonasal and transorbital approaches

This study aimed to ascertain the maximal exposure of the superior orbital fissure (SOF) afforded by combining endonasal and transorbital endoscopic approaches. Six cadaveric specimens (12 sides) were dissected using endonasal and transorbital endoscopic approaches to access the SOF. The order of the approaches was alternated in each specimen (eg, starting with an endonasal approach in one side followed by a transorbital exposure and reversing the order on the contralateral side). Maximal exposure of the SOF and its contents for individual and combined approaches were explored. The endonasal corridor provided adequate access to the inferomedial 1/3 of the SOF and including the proximal segments of cranial nerves (CN) III, V₁ and VI. A transorbital approach was superior accessing the superolateral 2/3's of the SOF, including the superior ophthalmic vein, lacrimal nerve, and distal segment of the CN VI at the lateral aspect; the nasociliary nerve and divisions of CN III centrally; and the frontal nerve and CN IV at the dorsal aspect of levator palpebrae superioris. This study suggests that a combined endonasal and transorbital exposure of the SOF may be advantageous to address lesions in this challenging region.

Endoscopic Endonasal Transsphenoidal Surgery: History and Evolution

In previous decades, extensive and disfiguring transfacial and/or transcranial approaches were used to reach the sellar and parasellar areas. However, these surgical routes were burdened by severe complications and high mortality rates. Recently, the development of endoscopic endonasal techniques has revolutionized the surgical strategies for approaching the sella and adjacent areas and increased the development of transsphenoidal surgery. With these techniques, surgeons have been able to overcome the visual limitations of the open surgical approaches and access areas previously hidden from view. After the contributions of the Pittsburgh duo, Carrau and Jho, pioneers of pure endoscopic surgery, our school began to implement this technique, introducing technical innovations and variations, describing the anatomical details and defining new routes, and playing a key role in its widespread clinical application.

Pituitary Adenomas: What Are the Key Features? What Are the Current Treatments? Where Is the Future Taking Us?

Pituitary tumors are a heterogeneous group of lesions (usually benign) and proper understanding of the anatomy, physiology, and pathology of the hypothalamic/pituitary region is essential to make an accurate diagnosis and define the essential treatment options (i.e., surgery, medical therapies, and radiotherapy, alone or in combination). Surgery is the primary treatment for acromegaly, Cushing disease, thyroid-stimulating hormone-secreting adenomas, resistant prolactinomas, and nonfunctioning pituitary adenomas causing mass effect. Medical and radiation therapy are reserved in cases in which surgery is not possible or does not provide a complete cure. In the last decades, tremendous innovations (i.e., targeted drugs and refined surgical tools and techniques) have expanded the treatment strategies for pituitary adenomas. We herein report the current indications for and depiction of the surgical techniques in pituitary surgery, review current medical treatments, and provide a glimpse of future possibilities.

Endoscopic transorbital surgery for Meckel's cave and middle cranial fossa tumors: surgical technique and early results

OBJECTIVE

Tumors involving Meckel's cave remain extremely challenging because of the surrounding complex neurovascular structures and deep-seated location. The authors investigated a new minimal-access technique using the endoscopic transorbital approach (eTOA) through the superior eyelid crease to Meckel's cave and middle cranial fossa lesions and reviewed the most useful surgical procedures and pitfalls of this approach.

METHODS

Between September 2016 and January 2018, the authors performed eTOA in 9 patients with tumors involving Meckel's cave and the middle cranial fossa. The lesions included trigeminal schwannoma in 4 patients, meningioma in 2 patients, metastatic brain tumor in 1 patient, chondrosarcoma in 1 patient, and dermoid cyst in 1 patient. In 7 of the 9 patients, eTOA alone was performed, while the other 2 patients underwent a combined eTOA and endoscopic endonasal approach or retrosigmoid craniotomy. Data including details of surgical techniques and clinical outcomes were recorded.

RESULTS

Gross-total resection was performed in 7 of the 9 patients (77.8%). Four patients underwent extended eTOA (with lateral orbital rim osteotomy). Drilling of the trapezoid sphenoid floor, a middle fossa "peeling" technique, and full visualization of Meckel's cave were applied to approach the lesions. Tumors were exposed and removed extradurally in 3 patients and intradurally in 6 patients. There was no postoperative CSF leak.

CONCLUSIONS

The eTOA affords a direct route to access Meckel's cave and middle cranial fossa lesions. With experience, this novel approach can be successfully applied to selected skull base lesions. To achieve successful removal of the tumor, emphasis should be placed on the importance of adequately removing the greater sphenoid wing and vertical crest. However, because of limited working space eTOA may not be an ideal approach for posterior fossa lesions.

Endoscopic transorbital approach to anterolateral skull base through inferior orbital fissure: a cadaveric study

BACKGROUND

Endoscopic transorbital approach (eTOA) has been announced as an alternative minimally invasive surgery to skull base. Owing to the inferior orbital fissure (IOF) connecting the orbit with surrounding pterygopalatine fossa (PPF), infratemporal fossa (ITF), and temporal fossa, the idea of eTOA to anterolateral skull base through IOF is postulated. The aim of this study is to access its practical feasibility.

METHODS

Anatomical dissections were performed in five human cadaveric heads (10 sides) using 0-degree and 30-degree endoscopes. A stepwise description of eTOA to anterolateral skull base through IOF was documented. The anterosuperior corner of the maxillary sinus in the horizontal plane of the upper edge of zygomatic arch was defined as reference point (RP). The distances between the RP to the foramen rotundum (FR), foramen ovale (FO), and Gasserian ganglion (GG) were measured. The exposed area of anterolateral skull base in the coronal plane of the posterior wall of the maxillary sinus was quantified.

RESULTS

The surgical procedure consisted of six steps: (1) lateral canthotomy with cantholysis and preseptal lower eyelid approach with periorbita dissection; (2) drilling of the ocular surface of greater sphenoid wing and lateral orbital rim osteotomy; (3) entry into the maxillary sinus and exposure of PPF and ITF; (4) mobilization of infraorbital nerve with drilling of the infratemporal surface of the greater sphenoid wing and pterygoid process; (5) exposure of middle cranial fossa, Meckel's cave, and lateral wall of cavernous sinus; and (6) reconstruction of orbital floor and lateral orbital rim. The distances measured were as follows: RP-FR = 45.0 ± 1.9 mm, RP-FO = 55.7 ± 0.5 mm, and RP-GG = 61.0 ± 1.6 mm. In comparison with the horizontal portion of greater sphenoid wing, the superior and inferior axes of the exposed area were 22.3 ± 2.1 mm and 20.5 ± 1.8 mm, respectively. With reference to the FR, the medial and lateral axes of the exposed area were 11.6 ± 1.1 mm and 15.8 ± 1.6 mm, respectively.

CONCLUSIONS

The eTOA through IOF can be used as a minimally invasive surgery to access whole anterolateral skull base. It provides a possible resolution to target lesion involving multiple compartments of anterolateral skull base.

Endoscopic endo- and extra-orbital corridors for spheno-orbital region: anatomic study with illustrative case

BACKGROUND AND OBJECTIVE

Management of selected spheno-orbital meningiomas via the endoscopic transorbital route has been reported. Surgical maneuverability in a narrow corridor as that offered by the orbit may be challenging. We investigate the additional use of an extra-orbital (EXO) path to be used in combination with the endo-orbital (EO) corridor.

MATERIAL AND METHODS

Three human cadaveric heads (six orbits) were dissected at the Laboratory of Surgical Neuroanatomy at the University of Barcelona. The superior eyelid endoscopic transorbital approach was adopted, introducing surgical instruments via both corridors. Surgical freedom analysis was run to determine directionality of each corridor and to calculate the surgical maneuverability related to three anatomic targets: superior orbital fissure (SOF), foramen rotundum (FR), and foramen ovale (FO). We also reported of a 37-year-old woman with a spheno-orbital meningioma with hyperostosis of the lateral wall of the right orbit, treated with such combined endo-orbital and extra-orbital endoscopic approach.

RESULTS

Combining both endo-orbital and extra-orbital corridors permitted a greater surgical freedom for all the targets compared with the surgical freedom of each corridor alone (EO + EXO to SOF: 3603.8 mm² ± 2452.5 mm²; EO + EXO to FR: 1533.0 mm² ± 892.2 mm²; EO + EXO to FO: 1193.9 mm² ± 782.6 mm²). Analyzing the extra-orbital pathway, our results showed that the greatest surgical freedom was gained in the most medial portion of the considered area, namely the SOF (1180.5 mm² ± 648.3 mm²). Regarding the surgical case, using both pathways, we gained enough maneuverability to nearly achieve total resection with no postoperative complications.

CONCLUSION

An extra-orbital corridor may be useful to increase the instruments' maneuverability, during a pure endoscopic superior eyelid approach, and to reach the most medial portion of the surgical field from a lateral-to-medial trajectory. Further studies are needed to better define the proper indications for such strategy.