Endoscopic superior eyelid transorbital approach: how I do it

The meningo-orbital band from an endoscopic transorbital approach: an anatomical study

Introduction

The meningo-orbital band (MOB) is an intricate dural structure extending between the periorbita, the frontal dura, and the temporal dura. The endoscopic transorbital approach (ETOA) provides a more thorough understanding of its anatomy.

Materials and methods

Anatomical dissections were performed on 15 human head specimens (30 orbits) at the Laboratory of Surgical Neuroanatomy (LSNA) at the University of Barcelona. The specimens were preserved using a Cambridge solution for optimal fixation. An endoscopic transorbital approach (ETOA) was used to isolate the meningo-orbital band (MOB). A rigid 4-mm endoscope with an HD camera and light source was used for the procedure. Multislice helical CT scans were performed both before and after the dissections to document the anatomical features. Additionally, a specialized software (The ImagingSource®) was used to calculate the variability in the angle between the first two bone pillars of the ETOA: the sagittal crest (SC) and the lesser sphenoid wing (LSW). The vascularization of the MOB was studied by longitudinally cutting the band and using red and blue latex injections into the carotid arteries and jugular veins, respectively, to highlight the cerebral vasculature.

Results

In the endoscopic transorbital approach (ETOA), key structures, including the greater and lesser sphenoid wings, are excised, exposing the meningo-orbital band (MOB). The MOB extends from the periorbita medially to the frontal and temporal dura laterally and is firmly attached to the anterior clinoid process (ACP). Anatomical dissection reveals the MOB's complex three-dimensional structure and its relationships with cranial nerves III, IV, and V1 along the lateral wall of the cavernous sinus and the superior orbital fissure (SOF). The ACP serves as a protective barrier between the MOB and the paraclinoid segment of the internal carotid artery (ICA). Additionally, the MOB is vascularized by the MOB artery (MOBA), a branch of the middle meningeal artery, which bifurcates into the frontal and temporal branches.

Conclusion

This study highlights the key anatomical relationships of the meningo-orbital band (MOB) with critical structures, including cranial nerves III, IV, and V1, as well as the ICA. These findings are essential for refining surgical planning and improving the safety and precision of skull base surgery.

Transorbital Transsylvian Selective Amygdalohippocampectomy: A Feasibility Anatomic Investigation

BACKGROUND AND OBJECTIVES

Several surgical techniques have been developed to treat mesial temporal lobe epilepsy, the most common form of drug-resistant epilepsy. Although surgical treatment for mesial temporal lobe epilepsy has proven to be highly effective in controlling seizures and improving patients' quality of life, it carries potential risk to critical neurovascular structures, which can result in significant complications. With the advent of endoscopic techniques, the transorbital route has emerged as a potential alternative for mesial temporal lobe surgery. This study aims to assess the feasibility, potential advantages, and disadvantages of the transorbital transsylvian selective amygdalohippocampectomy (TTSA) and to provide a step-by-step anatomic description of this approach.

METHODS

A TTSA was performed on three injected cadaveric specimens (six sides). Computer tomography and MRI scans were performed before and after each dissection to demonstrate the extent of amygdalohippocampectomy. Neuronavigation was used to identify the optimal trajectory and the position of intra-axial structures, including the amygdala and hippocampus. For each side, a TTSA was performed and all the anatomic landmarks verified from the standard transcranial perspective through a frontotemporal craniotomy.

RESULTS

The dissection procedure was organized into four sequential steps: (1) the extradural approach, (2) identification and opening of the sylvian fissure, (3) identification and removal of the amygdala, and (4) identification and removal of the hippocampus and parahippocampal gyrus. The intradural steps were performed in accordance with the technique described by Yasargil. Furthermore, a unique and educational comparison between the transorbital anatomic view and the related standard transcranial perspective was provided.

CONCLUSION

The described technique represents an innovative and feasible approach for amygdalohippocampectomy, achieving comparable surgical resection with traditional open surgery in cadaveric specimens, with potential advantages for neurological and neuropsychological outcomes. However, clinical series and further studies are imperative to validate these findings.

How I do It: Endoscopic transorbital resection of sphenoid osseous meningioma via the lateral orbital 'sliding coach door' approach

BACKGROUND

A 63-year-old presented with reduced left visual acuity and V1 sensation. Imaging demonstrated left sphenoid osseous meningioma narrowing superior orbital fissure with intracranial extension to superior temporal gyrus.

METHOD

Endoscopic transorbital approach utilising novel lateral orbit 'sliding coach door' osteotomy performed. Lateral canthal incision with lateral canthal ligament division mobilises and decompresses globe infero-medially. Osteotomy performed, tethered by temporalis. Osteotomy slides postero-laterally creating working space lateral to inferior and superior orbital fissures.

CONCLUSION

This technique requires reduced soft tissue dissection and facilitates reconstruction. Adequate working space enabled satisfactory resection with residual dural tail requiring future surveillance. Cosmesis was satisfactory.

Navigating the Intersection Between the Orbit and the Skull Base: The "Mirror" McCarty Keyhole During Transorbital Approach: An Anatomic Study With Surgical Implications

BACKGROUND AND OBJECTIVES

McCarty keyhole (MCK) is the most important entry point during orbitocranial and cranio-orbital approaches; nevertheless, its anatomic coordinates have never been detailedly described from transorbital perspective. To provide the spatial coordinates for intraorbital projection of the "mirror" MCK by using the well-established main anatomic-surgical bony landmarks met along transorbital corridor.

METHODS

MCK was identified in 15 adult dry skulls (30 sides) on exocranial surface of pterional region based on the well-defined external bony landmarks: on the frontosphenoid suture, 5 to 6 mm behind the joining point (JP) of frontozygomatic suture (FZS), frontosphenoid suture (FSS), and sphenozygomatic suture (SZS). A 1-mm burr hole was performed and progressively enlarged to identify the intracranial and intraorbital compartments. Exit site of the intraorbital part of burr hole was referenced to the FZS on the orbital rim, the superior orbital fissure, and the inferior orbital fissure and to the JP of FZS, FSS, and SZS. To electronically validate the results, 3-dimensional photorealistic and interactive models were reconstructed with photogrammetry. Finally, for a further validation, McCarty mirror keyhole was also exposed, based on results achieved, through endoscopic transorbital approach in 10 head specimens (20 sides).

RESULTS

Intraorbital projection of MCK was identified on the FSS on intraorbital surface, 1.5 ± 0.5 mm posterior to JP, 11.5 ± 1.1 mm posterior to the FZS on orbital rim following the suture, 13.0 ± 1.2 mm from most anterior end of superior orbital fissure, 15.5 ± 1.4 mm from the most anterior end of the inferior orbital fissure in vertical line, on measurements under direct macroscopic visualization (mean ± SD). These values were electronically confirmed on the photogrammetric models with mean difference within 1 mm.

CONCLUSION

To be aware of exact position of intraorbital projection of MCK during an early stage of transorbital approaches provides several surgical, clinical, and aesthetic advantages.

The Endoscopic Transorbital Approach for Vascular Surgery: An Anterior Circulation Anatomic Study, 2-Dimensional Operative Video

BACKGROUND AND OBJECTIVES

Minimally invasive endoscopic approaches in cranial base surgery have been developing in the past decades. The transorbital (TO) route is one promising alternative, yet its adequacy for intracranial vascular lesions remains unclear. The present anatomic work aimed to test the feasibility and to provide a qualitative description of the endoscopic TO approach for the anterior circulation, namely the internal carotid artery and the middle cerebral artery.

METHODS

Seven embalmed adult cadaveric specimens (12 sides) were used in the study. Each side was approached in 3 successive steps: (1) Superior-eyelid TO approach, with great and lesser sphenoid wing removal. (2) Removal of anterior clinoid process (ACP). (3) Removal of the lateral orbital rim. All the procedures were performed under endoscopic view.

RESULTS

The TO approach without removing the ACP allowed to dissect the sphenoidal and lateral segments of the Sylvian fissure with an adequate identification of the middle cerebral artery bifurcation in all specimens. The removal of the ACP allowed further dissection toward the opticocarotid cistern, with the identification of the ophthalmic, posterior communicating, and the anterior choroidal arteries. The internal carotid artery bifurcation and A1 segment were also readily identified. Finally, removal of the lateral orbital rim provided a wider and more comfortable access to the above-mentioned vascular structures.

CONCLUSION

According to our anatomic data, the TO approach can be used to reach the main vascular components of the anterior circulation. This opens the field for exploring its application in the treatment of vascular pathology, particularly aneurysms.

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.

Elucidation of the Cranial Arterial Anatomy Using the Transorbital Endoscopic Approach

New surgical techniques that access the orbit and intracranial cavity have been developed in recent years called transorbital neuroendoscopic surgery. The superior eyelid route, as a transorbital corridor, is a clinically feasible route to access selected anterior and middle skull base pathologies. However, studies regarding the suitability of this approach in vascular surgery are lacking. In this study, transorbital endoscopic dissections were performed bilaterally in 4 cadavers through the superior eyelid approach. The authors aimed to define the arterial vascular structures that can be accessed through this approach. In this study, the M1 and M2 segments of the middle cerebral artery and the branches originating from it were accessible with a 0 degree endoscope after an appropriate dissection. Thus, the endoscopic superior eyelid approach may be a novel alternative approach for some cranial pathologies.

Neurophysiologic Monitoring of Oculomotor Nerves During Transorbital Surgery: Proof of Concept and Anatomic Demonstration

BACKGROUND AND OBJECTIVES

Transorbital neuroendoscopic surgery (TONES) is continuously evolving and gaining terrain in approaching different skull base pathologies. The objective of this study was to present our methodology for introducing recording electrodes, which includes a new transconjunctival pathway, to monitor the extraocular muscle function during TONES.

METHODS

A translational observational study was performed from an anatomic demonstration focused on the transconjunctival electrode placement technique to a descriptive analysis in our series of 6 patients operated using TONES in association with intraoperative neurophysiologic monitoring of the oculomotor nerves from 2017 to 2023. The stepwise anatomic demonstration for the electrode placement and correct positioning in the target muscle was realized through cadaveric dissection. The descriptive analysis evaluated viability (obtention of the electromyography in each cranial nerve [CN] monitored), security (complications), and compatibility (interference with TONES).

RESULTS

In our series of 6 patients, 16 CNs were correctly monitored: 6 (100%) CNs III, 5 (83.3%) CNs VI, and 5 (83.3%) CNs IV. Spontaneous electromyography was registered correctly, and compound muscle action potential using triggered electromyography was obtained for anatomic confirmation of structures (1 CN III and VI). No complications nor interference with the surgical procedure were detected.

CONCLUSION

The methodology for introducing the recording electrodes was viable, secure, and compatible with TONES.

Complications of the Superior Eyelid Endoscopic Transorbital Approach to the Skull Base: Preliminary Experience With Specific Focus on Orbital Outcome

BACKGROUND

The endoscopic superior eyelid approach is a relatively novel mini-invasive technique that is currently investigating for skull base cancers. However, questions remain regarding specific approach-related complications when treating different skull base tumors. This study aims to analyze any surgical complications that occurred in our preliminary consecutive experience, with specific focus on orbital outcome.

METHODS

A retrospective and consecutive cohort of patients treated via a superior eyelid endoscopic transorbital approach at the Division of Neurosurgery of the Hospital Clinic in Barcelona was analyzed. Patients features were described in detail. Complications were divided into 2 groups to analyze separately the approach-related complications, and those resulting from tumor removal. The ocular complications were subdivided into early ocular status (<3 weeks), late ocular status (3-8 weeks), and persistent ocular complications. The "Park questionnaire" was used to determine patient's satisfaction related to the transorbital approach.

RESULTS

A total of 20 patients (5 spheno-orbital meningiomas, 1 intradiploic Meningioma, 2 intraconal lesions, 1 temporal pole lesion, 2 trigeminal schwannoma, 3 cavernous sinus lesions, and 6 petroclival lesions) were included in the period 2017-2022. Regarding early ocular status, upper eyelid edema was detected in all cases (100%) associated with diplopia in the lateral gaze in 30% of cases, and periorbital edema in 15% of cases. These aspects tend to resolve at late ocular follow-up (3-8 weeks) in most cases. Regarding persistent ocular complications, in one case of intraconal lesion, a limitation of eye abduction was detected (5%). In another patient with intraconal lesion, an ocular neuropathic pain was reported (5%). In 2 cases of petroclival menigioma, who were also treated with a ventriculo-peritoneal shunt, slight enophthalmus was observed as a persistent complication (10%). According to the Park questionnaire, no cosmetic complaints, no head pain, no palpable cranial irregularities, and no limited mouth opening were reported, and an average of 89% of general satisfaction was encountered.

CONCLUSIONS

The superior eyelid endoscopic transorbital approach is a safe and satisfactory technique for a diversity of skull base tumors. At late follow-up, upper eyelid edema, diplopia, and periorbital edema tend to resolve. Persistent ocular complications are more frequent after treating intraconal lesions. Enophthalmus may occur in patients with associated ventriculo-peritoneal shunt. According to patient's satisfaction, fairly acceptable results are attained.

Exo- and endoscopic lateral orbital wall approach for the medial temporal lobe glioma: how I do it

BACKGROUND

The endoscopic transorbital approach provides a direct access to the medial temporal lobe (MTL). However, when excising a highly vascular tumour, a wider access route that enables the concurrent use of standard neurosurgical instruments with both hands is preferable.

METHOD

We described the concept and technique of the lateral orbital wall approach (LOWA), which comprises orbitotomy and mini-craniotomy to treat MTL lesions using an exoscope and endoscope.

CONCLUSION

The LOWA provides a safe and natural surgical corridor to the MTL and enables 2- or 3-hand surgery. Hence, LOWA can potentially improve safety and efficiency to treat MTL lesions.

360 Degrees Endoscopic Access to and Through the Orbit

The treatment of pathologies located within and surrounding the orbit poses considerable surgical challenges, due to the intricate presence of critical neurovascular structures in such deep, confined spaces. Historically, transcranial and craniofacial approaches have been widely employed to deal with orbital pathologies. However, recent decades have witnessed the emergence of minimally invasive techniques aimed at reducing morbidity. Among these techniques are the endoscopic endonasal approach and the subsequently developed endoscopic transorbital approach (ETOA), encompassing both endonasal and transpalpebral approaches. These innovative methods not only facilitate the management of intraorbital lesions but also offer access to deep-seated lesions within the anterior, middle, and posterior cranial fossa via specific transorbital and endonasal corridors. Contemporary research indicates that ETOAs have demonstrated exceptional outcomes in terms of morbidity rates, cosmetic results, and complication rates. This study aims to provide a comprehensive description of endoscopic-assisted techniques that enable a 360° access to the orbit and its surrounding regions. The investigation will delve into indications, advantages, and limitations associated with different approaches, while also drawing comparisons between endoscopic approaches and traditional microsurgical transcranial approaches.

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.

Endoscopic transorbital resection of the temporal lobe: anatomic qualitative and quantitative study

Objective

Starting from an anatomic study describing the possibility of reaching the temporal region through an endoscopic transorbital approach, many clinical reports have now demonstrated the applicability of this strategy when dealing with intra-axial lesions. The study aimed to provide both a qualitative anatomic description of the temporal region, as seen through a transorbital perspective, and a quantitative analysis of the amount of temporal lobe resection achievable via this route.

Material and methods

A total of four cadaveric heads (eight sides) were dissected at the Laboratory of Surgical Neuroanatomy (LSNA) of the University of Barcelona, Spain. A stepwise description of the resection of the temporal lobe through a transorbital perspective is provided. Qualitative anatomical descriptions and quantitative analysis of the amount of the resection were evaluated by means of pre- and post-dissection CT and MRI scans, and three-dimensional reconstructions were made by means of BrainLab®Software.

Results

The transorbital route gives easy access to the temporal region, without the need for extensive bone removal. The resection of the temporal lobe proceeded in a subpial fashion, mimicking what happens in a surgical scenario. According to our quantitative analysis, the mean volume removed was 51.26%, with the most superior and lateral portion of the temporal lobe being the most difficult to reach.

Conclusion

This anatomic study provides qualitative and quantitative details about the resection of the temporal lobe via an endoscopic transorbital approach. Our results showed that the resection of more than half of the temporal lobe is possible through this surgical corridor. While the anterior, inferior, and mesial portions of the temporal lobe were easily accessible, the most superior and lateral segment was more difficult to reach and resect. Our study serves as an integration to the current anatomic knowledge and clinical practice knowledge highlighting and also as a starting point for further anatomic studies addressing more selected segments of the temporal lobe, i.e., the mesial temporal region.

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 Transorbital Approach for Spheno-Orbital Tumors: Case Series and Systematic Review of Literature

BACKGROUND

Transorbital neuroendoscopic surgery (TONES) comprises a group of approaches with indications expanding from orbital tumors to more complex skull base lesions. We analyzed the role of the endoscopic transorbital approach (eTOA) for spheno-orbital tumors, reporting the results of our clinical series and of a systematic review of the literature.

MATERIALS AND METHODS

All patients operated on from 2016 to 2022 at our institution for a spheno-orbital tumor through an eTOA were included in a clinical series, and a systematic review of the literature was performed.

RESULTS

Our series consisted of 22 patients (16 females, mean age 57 ± 13 years). Gross tumor removal was achieved in 8 patients (36.4%) after the eTOA and in 11 (50.0%) after a multistaged strategy combining the eTOA with the endoscopic endonasal approach. Complications included 1 chronic subdural hematoma and 1 permanent extrinsic ocular muscle deficit. Patients were discharged after 2.4 ± 1.3 days. The most common histotype was meningioma (86.4%). Proptosis improved in all cases, visual deficit in 66.6%, and diplopia in 76.9%. These results were confirmed by the review of the 127 cases reported in the literature.

CONCLUSIONS

Despite its recent introduction, a significant number of spheno-orbital lesions treated with an eTOA are being reported. Its main advantages are favorable patient outcome and optimal cosmetic results, with minimal morbidity and quick recovery. This approach can be combined with other surgical routes or adjuvant therapies for complex tumors. However, it is a technically demanding procedure, requiring specific skills in endoscopic surgery, that should be reserved to dedicated centers.

Endoscopic Transorbital Approach for the Management of Spheno-Orbital Meningiomas: Literature Review and Preliminary Experience

OBJECTIVE

The endoscopic transorbital approach (ETOA) is a minimally invasive approach that could be particularly appropriate for management of spheno-orbital meningiomas. The aim of this study was to perform a systematic review of the literature on the management of spheno-orbital meningiomas via the minimally invasive ETOA, searching for clinical scenarios in which this approach could be best indicated. A secondary aim was to describe 4 illustrative cases.

METHODS

A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data including patient demographics, tumor features, and surgical and postoperative outcomes were collected. Cases from our initial experience with ETOA were included in the data.

RESULTS

Data of 58 patients from 9 selected records and from our surgical series were collected. Subtotal, near-total, and gross total resection rates were 44.8%, 10.3%, and 32.7%, respectively. Symptom improvement after surgery was 100% for proptosis, 93% for visual impairment, and 87% for ophthalmoplegia. The most common postoperative complications were transient ophthalmoplegia and maxillary nerve hypoesthesia. Cerebrospinal fluid leak was reported in 2 patients.

CONCLUSIONS

Our findings support the use of the ETOA for management of spheno-orbital meningiomas, particularly in at least 3 clinical scenarios: 1) when predominant hyperostotic bone is present; 2) when a globular tumor not showing excessive medial or inferior infiltration is being treated; 3) as part of a multistage treatment for diffuse lesions.

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.

Alternative Path for Optic Nerve Decompression in Pseudotumor Cerebri With Full Endoscopic Lateral Transorbital Approach

Endonasal endoscopic approaches are the most preferred surgical methods in patients with pseudotumor cerebri because of easy access to the optic nerve, but the choice of this technique may not apply to all endoscopic endonasal cases. Moreover, there may be difficulties in practice in some cases, including the coronavirus disease 2019 pandemic. This study aimed to suggest an alternative endoscopic approach by lateral orbitotomy for optic nerve decompression in patients with pseudotumor cerebri. The study was performed using 5 fresh-frozen cadaver heads (bilaterally, total of 10 sides) injected intravenously with colored silicone preserved in the cold chain. An average of 2.5 cm skin incision was made to fit the lateral orbitotomy. The lengths of the recurrent meningeal artery (mm), the meningo-orbital band (mm), and the optic nerve (mm) to the orbital margin were measured. After these morphometric measurements, optic nerve decompression was performed endoscopically, and the length of the decompression was measured (mm). The average length (mm) between the orbital rim and meningeal recurrent artery (or meningolacrimal branch) was 16.2 mm, between the orbital rim and the meningo-orbital band was 18.5 mm, and between the orbital rim and optic nerve was 44.1 mm. The average optic nerve decompression length was 4.4 mm. The endoscopic lateral orbitotomy approach provides easy access to the optic nerve by anatomically following the recurrent meningeal artery and the meningo-orbital band. It can be a safe second-line approach after endonasal approaches for optic nerve decompression in pseudotumor cerebri.

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.

Multiportal Combined Endoscopic Endonasal and Transorbital Pathways: Qualitative and Quantitative Anatomic Studies of the "Connection" Skull Base Areas

BACKGROUND

Combined endonasal and transorbital multiportal surgery has been recently described for selected skull base pathologies. Nevertheless, a detailed anatomic description and a quantitative comprehensive anatomic study of the skull base areas where these 2 endoscopic routes converge, a so-called connection areas, are missing in the scientific literature.

OBJECTIVE

To identify all the skull base areas and anatomic structures where endonasal and transorbital endoscopic avenues could be connected and combined.

METHODS

Five cadaveric specimens (10 sides) were used for dissection. Qualitative description and quantitative analysis of each connection areas were performed.

RESULTS

At the anterior cranial fossa, the connection area was found at the level of the sphenoid planum; in the middle cranial fossa, it was at the Mullan triangle; finally, in the posterior cranial fossa, the connection area was just behind the medial portion of the petrous apex. The average extradural working areas through the transorbital approach were 4.93, 12.93, and 1.93 cm 2 and from the endonasal corridor were 7.75, 10.45, and 7.48 cm 2 at the level of anterior, middle, and posterior cranial fossae, respectively.

CONCLUSION

The combined endonasal and transorbital endoscopic approach is an innovative entity of skull base neurosurgery. From the anatomic point of view, our study demonstrated the feasibility of this combined approach to access the entire skull base, by both corridors, identifying a working connection area in each cranial fossa. These data could be extremely useful during the surgical planning to predict which portion of a lesion could be removed through each route and to optimize patients' care.

Transorbital endoscopic-assisted management of intraorbital lesions: Experience of 11 cases

Purpose

To present our experience in the management of selected extraconal orbital roof lesions utilizing the transorbital endoscopic approach.

Methods

A retrospective case series of patients who underwent transorbital endoscopic orbital surgery in a single medical center between 2015 to 2020.

Results

Eleven patients underwent transorbital endoscope assisted surgery for various indications. The mean age at surgery was 31.9 years (range, 6–73 years). Mean follow-up time was 18 months (range, 1–30). The aim of surgery was curative in 10 cases and diagnostic in one patient. Adequate specimen for tissue diagnosis was obtained from all patients. In 8 patients the procedure was completed through a superior eyelid crease incision, and in three patients a combined approach including functional endoscopic sinus surgery was used for achieving complete excision. None of the patients required conversion to an external wider orbital procedure. Intraoperative complication included cerebrospinal fluid leak in one case, which was addressed immediately; and postoperative complications included one case of pre-septal orbital cellulitis treated by intravenous antibiotics with complete resolution.

Conclusion

Endoscopic-assisted transorbital approach enabled safe removal of selected lesions involving the orbital roof and provides an effective and less invasive alternative to a traditional frontal craniotomy or lateral orbitotomy.

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 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.