Endoscopic endonasal anatomy of superior orbital fissure and orbital apex regions: critical considerations for clinical applications

Morphometric evaluation of the anatomical relationships between the superior orbital fissure and the orbital structures based on computed tomography images with clinical implications

PURPOSE

To assist in surgical planning in endoscopic approaches, we analyzed the morphometric measurements of the superior orbital fissure (SOF) and optic canal (OC) by three-dimensional multislice computed tomography (3D MDCT) and evaluated them according to age, gender, and lateralization.

METHODS

The study analyzed 219 MDCT images (114 women, 105 men) from individuals aged 18-90. Measurements of SOF and OC were performed on 3D MDCT images in the axial plane and with 3D-Slicer software.

RESULTS

The distance between the infraorbital foramen and the anterior entrance of the maxillary sinus (CBW) (p < 0.001), the distance between the CBW and the lateral point of the SOF (p = 0.001), and the Angle 1 (p = 0.028) were higher in women than in men. While the SOF length and on 3D the SOF width were higher in women than men (p < 0.001 and (p = 0.001, respectively), the lateral wall length OC was higher in men than women (p = 0.045). According to SOF classification, SOF length was highest in type II and lowest in type VIII (p = 0.025), SOF width was highest in type I and lowest in type VI (p < 0.001). No significant difference was found based on age groups and lateralization in all parameters.

CONCLUSION

We found that as the SOF width increased, the SOF length also increased, and there was a statistically strong positive correlation. These findings can contribute to a more effective and safe operation by improving and updating surgeons' knowledge about safe distances to SOF in endoscopic procedures from a 3D MDCT perspective.

Endoscopic transorbital decompression for traumatic superior orbital fissure syndrome: from cadaveric study to clinical application

PURPOSE

The endoscopic endonasal approach (EEA) is a minimally invasive and promising modality for treating traumatic superior orbital fissure (SOF) syndrome (tSOFS). Recently, the endoscopic transorbital approach (ETOA) has been considered an alternative method for reaching the anterolateral skull base. This study accessed the practicality of using the ETOA to treat SOF decompression using both cadaveric dissection and clinical application.

METHODS

Bilateral anatomic dissections were performed on four adult cadaveric heads using the ETOA and EEA to address SOF decompression. The ETOA procedure for SOF decompression is described, and the extent of SOF decompression was compared between the ETOA and EEA. The clinical feasibility of the ETOA for treating SOF decompression was performed in two patients diagnosed with tSOFS.

RESULTS

ETOA allowed for decompression over the lateral aspect of the SOF, from the meningo-orbital band superolaterally to the maxillary strut inferomedially. By contrast, the EEA allowed for decompression over the medial aspect of the SOF, from the lateral opticocarotid recess superiorly to the maxillary strut inferiorly. In both patients treated using the ETOA and SOF decompression, the severity of ophthalmoplegia got obvious improvement.

CONCLUSIONS

Based on the cadaveric findings, ETOA provided a feasible access pathway for SOF decompression with reliable outcomes, and our patients confirmed the clinical efficacy of the ETOA for managing tSOFS.

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.

Endonasal Endoscopic Anatomy of the Orbito-Cavernous-Pterygopalatine Interface: Multilayer Anatomical Description and Landmarks to Define the Limits of the Compartments

BACKGROUND

Despite growing interest in the endoscopic endonasal approach (EEA) to the medial orbital apex (OA), a comprehensive description of the multilayer topology lying at the intersection of the regional compartments is missing.

METHODS

An EEA to the OA, pterygopalatine fossa, and cavernous sinus was performed in 20 specimens. A 360° layer-by-layer dissection was performed taking into consideration relevant anatomical aspects of the interface and documented with 3-dimensional technologies. Endoscopic landmarks were analyzed to provide an outline of the compartments and identify critical structures. Additionally, the consistency of a previously described reference called orbital apex convergence prominence was analyzed and a method to identify its position was introduced.

RESULTS

The orbital apex convergence prominence was an inconsistent finding (15%). However, a craniometric method introduced in this study proved to be reliable to reach the orbital apex convergence point. Additional structures such as the sphenoethmoidal suture and a 3-suture junction (sphenoethmoidal-palatoethmoidal-palatosphenoidal) helped to identify the posterior limit of the OA and define a keyhole to access the compartments of the interface. We defined the bone limits of the "optic risk zone," an area where the optic nerve is more susceptible to damage. Furthermore, an orbital fusion line (periorbita-dura-periosteum) was identified and divided into 4 segments according to adjacent structures: optic, cavernous, pterygopalatine, and infraorbital.

CONCLUSIONS

Understanding cranial landmarks and the folds of the layers covering the orbito-cavernous-pterygopalatine interface can facilitate tailoring an EEA to the medial orbital space and avoid unnecessary exposure of sensitive anatomy in the vicinity.

Combined endonasal and orbital approach for annulus of Zinn area decompression in dysthyroid optic neuropathy

BACKGROUND

Dysthyroid optic neuropathy (DON) is a serious complication of thyroid-associated ophthalmopathy (TAO) that can cause permanent vision loss from orbital apex syndrome. Urgent management of high-dose corticosteroid pulse therapy is recommended, and salvage orbital apex decompression surgery may require in refractory patients ineffective with corticosteroid pulse therapy.

PURPOSE

To evaluate the short-term efficacy and safety of combined endoscopic endonasal and orbital approach decompression in the annulus of the Zinn (AZ) area in refractory dysthyroid optic neuropathy (DON).

METHODS

In this retrospective study, patients who underwent combined endoscopic endonasal and orbital approach decompression around the AZ area for the treatment of refractory DON from May 2021 to March 2022 were enrolled. A total of 15 orbital apex were decompressed across 9 patients. The demographic, imaging, and surgical data, as well as preoperative and postoperative best corrected visual acuity (BCVA), proptosis degree and Modified-Chinese-TAO-QOL scores, were collected and assessed. The t-test was used to identify differences between preoperative and postoperative parameters: visual acuity, proptosis and QOL scores.

RESULTS

The mean best corrected visual acuity (BCVA) improved from 0.79 ± 0.77 LogMAR preoperatively to 0.21 ± 0.27 LogMAR (P < 0.001) postoperatively. Additionally, proptosis decreased from 22.25 ± 2.01 mm to 18.42 ± 1.85 mm (P < 0.01), with an average decrease of 3.7 mm. The preoperative scores of the visual, psychological, and comprehensive components of QoL were 14.60 ± 9.08, 37.49 ± 6.26 and 26.75 ± 3.70, respectively, which significantly improved postoperatively to 54.18 ± 7.23, 68.78 ± 12.53 and 61.88 ± 9.37, respectively. The postoperative follow-up time ranged from 2 to 11 months, and the median follow-up time was 7 months. There was 1 case of transient postoperative sinusitis and 1 new case of transient diplopia, which was relieved after 3 months.

CONCLUSION

Combined endoscopic endonasal and orbital approach adequate decompression for AZ area significantly improves visual acuity and QOL in patients with DON.

Traumatic oculomotor nerve palsy treated with transnasal endoscopic decompression through the optic strut

Objective

To present a surgical treatment regimen of transnasal endoscopic decompression through the optic strut for traumatic oculomotor nerve palsy based on the anatomical study of the superior orbital fissure and the oculomotor nerve fissure segment.

Methods

The bone structure of the oculomotor nerve fissure segment and the important bone anatomical landmarks of the lateral wall of the sphenoidal sinus were identified on a dried skull and a cadaveric head, respectively, using a nasal endoscope, and a surgical plan was determined. Decompression was conducted on the orbital apex, the superior orbital fissure, the optic canal and the optic strut of the two patients in sequence, after which the degree and range of decompression were identified by three-dimensional (3D) computed tomography (CT).

Results

The oculomotor nerve had a close correlation with the lateral surface of the optic strut. The transnasal endoscope was employed to identify the lateral optic-carotid recess (LOCR), as well as the positions of the optic nerve, internal carotid artery (ICA), and superior orbital fissure, collectively called the "optic strut triangle". The surgical plans for decompression of the orbital apex, superior orbital fissure, optic canal, and optic strut and the necessity of optic strut drilling were determined, and the surgical procedures for safe drilling of the optic strut were elaborated. After surgery, the two patients had significantly improved symptoms, without complications. In addition, their postoperative CT showed that the medial margin of the superior orbital fissure was fully decompressed.

Conclusion

The optic strut triangle is a crucial anatomical landmark in the decompression of the oculomotor nerve, and optic strut drilling is necessary for such decompression. For patients with traumatic oculomotor nerve palsy and fractures of the medial wall of the superior orbital fissure on CT, the oculomotor nerve fissure segment can be decompressed in an effective, complete and safe manner as per the surgical plan of decompressing the orbital apex, superior orbital fissure, optic canal and optic strut in turn under a transnasal endoscope, conducive to the recovery of neurological function of patients.

Endoscopic Transnasal Transmaxillary Approach to Orbital Apex through the Meningo-Orbital Band: A Cadaveric Feasibility Study

Background

Extradural transcranial release of the meningo-orbital band occupying the lateral part of the superior orbital fissure is used to approach the orbital apex and middle cranial fossa. The authors tested the feasibility of the release of the meningo-orbital band via an endonasal transmaxillary approach.

Materials and Methods

Five injected cadaveric heads were assessed for dimensions of superior orbital fissure by computerized tomography. An endonasal transsphenoid transpterygoid approach was done to the superior orbital fissure and annulus of Zinn medially, down to the maxillary nerve. The periorbita was dissected superolaterally to expose the greater wing of the sphenoid and the meningo-orbital band. The superior orbital fissure was decompressed inferiorly by drilling the greater wing of the sphenoid and the maxillary strut after transposition of the maxillary nerve. The meningoorbital band was cut at the junction of the lateral part of the superior orbital fissure and the periorbita exposing the frontotemporal dural junction. The edge of the lesser wing of the sphenoid was drilled toward the annulus of Zinn and the optic canal. The temporal lobe dura was separated from the periorbita and lateral cavernous dural wall at the meningo-orbital band and the ophthalmic nerve.

Results

The superior orbital fissure had an oblique angle (mean: 39 ± 2.75 degrees) to the midsagittal plane, the length of its lateral part corresponding to the meningo-orbital band was (mean: 6.08 ± 2.58 mm) and the distance from its lateral end to midline was (mean 2.97 ± 0.11 cm). The meningo-orbital band was released in 10 cadaveric head sides with a distinct plane between the periorbita and the dura propria. Transmaxillary endoscopy provided less orbital retraction and better visualization of the lateral wall of the cavernous sinus.

Conclusion

Endonasal transmaxillary release of the meningoorbital band is feasible, allowing exposure of the orbital apex and the middle cranial fossa.

Simultaneous Endoscopic Endonasal Decompression of the Optic Canal, Superior Orbital Fissure, and Proper Orbital Apex for Traumatic Orbital Apex Syndrome: Surgical Anatomy and Technical Note

Objectives

Traumatic orbital apex syndrome (TOAS) is an uncommon but severe ocular complication of craniomaxillofacial fracture. The optimal surgical strategy for TOAS has not been determined. To investigate the endoscopic anatomy of the orbital apex region, propose a protocol for simultaneous endoscopic endonasal decompression of the optic canal, superior orbital fissure, and proper orbital apex (EEDCFA) for TOAS and report its use in two patients.

Methods

An endoscopic endonasal approach was utilized to dissect the orbital apex region in two silicon-injected adult cadaveric heads. The details of the procedure used for decompression of the orbital apex were determined. The effects of this procedure were determined in two patients with TOAS who underwent simultaneous decompression of the optic canal, superior orbital fissure, and proper orbital apex.

Results

The orbital apex consisted of three portions, the contents of the optic canal superomedially; the contents of the superior orbital fissure inferolaterally; and the converging portion, or proper orbital apex, anteriorly. From an endoscopic endonasal approach, the optic nerve, superior orbital fissure, and orbital apex convergence prominences were found to form a π-shaped configuration. This π-shaped configuration was indicative of the orbital apex and was an important landmark for decompression of the orbital apex. Endonasal decompression of the orbital apex in the two patients resulted in the satisfactory recovery of extraocular mobility, with no surgical complications.

Conclusions

EEDCFA is feasible, effective, and safe for patients with TOAS caused by direct compression of displaced fracture segments. The π-shaped configuration is a valuable landmark for EEDCFA.

A novel landmark for endonasal surgery of the pterygopalatine fossa and inferior orbital fissure: The orbito-pterygo-sphenoidal ligament

The pterygopalatine fossa contains a dense and complex array of neurovascular structures vulnerable to accidental surgical injury. This study aims to describe a novel landmark, the orbito-pterygo-sphenoidal ligament (OPSL), and implications of this structure for surgery in the pterygopalatine fossa and the inferior orbital fissure. Six cadaveric specimens (12 sides) were dissected using an endonasal approach to expose the periosteal layers associated with the pterygopalatine fossa and orbit. The thickened triangular-shaped ligament at their confluence was termed the OPSL. Dimensions of its lateral, inferior, and medial borders were measured, and their anatomical relationships defined. The pterygopalatine ganglion and the maxillary nerve lie immediately inferior and deep into the OPSL. The superior aspect of the posterior nasoseptal artery and nerve are covered by the medial OPSL. The lateral and inferior borders of the OPSL are contiguous with the periorbita and the periosteum of the pterygopalatine fossa, respectively. Along the medial border of the ligament, the openings of the palatovaginal fissure, vidian canal, and foramen rotundum were sequentially identified in a medial to lateral trajectory. The length of the lateral, inferior, and medial borders of the triangular OPSL were 13.25 ± 0.62, 14.25 ± 0.45, and 12.08 ± 0.90 mm, respectively. The OPSL is a thick, triangular-shaped fascial confluence, which may serve as a landmark for procedures within the pterygopalatine fossa and the inferior orbital fissure.

Surgical anatomy and technical nuances of the endoscopic endonasal approach to the anterior cranial fossa

Endoscopic endonasal approaches (EEA) to the skull base have significantly impacted the management of lesions located in the cranial base. Specifically, lesions arising from the anterior cranial fossa, such as pituitary macroadenomas, craniopharyngiomas meningiomas and craniofacial malignancies have benefited from the development of such approaches. Understanding of the anatomy of the anterior fossa is of utmost importance for the successful selection of the approach and application of surgical techniques in EEA. In the current manuscript, we review the most relevant points of surgical anatomy and nuances of the surgical technique of EEA to the anterior fossa. Anatomical landmarks for the transtuberculum transplanum and transcribriform approaches are discussed and a step-by-step description for those approaches is presented. We reinforce that safe and effective application of such techniques follow the same principles of other skull base surgery techniques: mastering of surgical anatomy, adequate case selection, correct instrumentation and surgical experience.

A systematic review of the surgical anatomy of the orbital apex

Purpose

The orbital apex is the narrowest part of the orbit, housing the link between the intracranial cavity and orbit. Knowledge of orbital apex anatomy is crucial to selecting a surgical approach and reducing the risk of complications. Our purpose is to summarize current knowledge on surgical anatomy and attempt to reach a consensus on definition of the orbital apex.

Methods

The online databases of Embase, the Cochrane library, Web of Science and PubMed (MEDLINE) were queried in a comprehensive bibliographic search on the (surgical) anatomy of the orbital apex and consisted of a combination of two subjects, using indexed terms and free text: “Orbital Apex” and “Orbital Anatomy.”

Results

A total of 114 relevant papers were included in this review. Numerous anatomical variations are described in the literature. Variations of the optic canal include duplication (0.64%) and keyhole anomaly (2.65%). Variations in pneumatization of the anterior clinoid process were unilateral in almost 10%, bilateral in 9%, and normal in 72%. A rare variant of the superior orbital fissure (SOF) is Warwick’s foramen, which appears as if the lowest portion of the SOF was separated from the main fissure by a transverse bony bridge.

Conclusion

The definition of the orbital apex varies in the literature, and further research would most likely identify additional variations. A universal definition reporting these variations and pathology and imaging findings is essential for determining the optimal surgical approach to the orbital apex.

Electronic supplementary material

The online version of this article (10.1007/s00276-020-02573-w) contains supplementary material, which is available to authorized users.

Surgery around the Orbit: How to Select an Approach

Orbital region pathologies may be safely and effectively treated through a various number of approaches. As the concept of "outcome" and minimally invasive surgery keeps gaining popularity in neurosurgery, these approaches-each with specific indications and limitations-together provide the best surgical options.

Orbital Anatomy: Anatomical Relationships of Surrounding Structures

Advances in skull base and orbital surgery have led to an increased need to understand the anatomy of the orbit and surrounding structures to safely perform surgeries in this area. The purpose of this article is to review the surrounding anatomy of the orbit from a practical and operative point of view. We describe the orbit from an inferomedial endoscopic endonasal perspective (focusing on its inferior relationship with the maxillary sinus and related structures and its medial relationship with the ethmoid bone), from a posterior and superolateral intracranial perspective (describing the anatomy of the superior orbital fissure, optic canal, inferior orbital fissure, cavernous sinus, orbitofrontal cortex, and surrounding dura) and from an anterior perspective (focusing on the muscles, connective tissue, lateral and medial canthus, and relevant neurovascular anatomy). A deep knowledge of the critical neurovascular and osseous structures surrounding the orbit is necessary for adequately choosing and performing the most favorable orbital approach in every case.

Endoscopic Endonasal Approach for Intra- and Extraconal Orbital Pathologies

Endoscopic endonasal approaches offer an important alternative in the management of posterior inferomedial orbital pathology. Beginning with endoscopic orbital decompressions for Graves' disease, the endonasal corridor for the management of intra- and extraconal pathologies has continued to evolve. Endonasal removal of orbital cavernous hemangiomas is well described in the literature; however, many other benign and malignant pathologies of the medial orbit can be accessed through this approach. Advantages of the endonasal approach include improved visualization and decreased manipulation of orbital contents in the medial and posterior orbit. Additionally, for tumors that extend from the paranasal sinuses into the orbit, this corridor may be ideal for concurrent management. The current literature for this approach will be reviewed including the oncologic results, complications, limitations, and reconstructive needs along with pertinent anatomy. In addition, data from our own institution will be reviewed.

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.

Clinical Anatomy of the Extradural Neural Axis Compartment: A Literature Review

OBJECTIVE

The extradural neural axis compartment (EDNAC) is an adipovenous zone located between the meningeal and endosteal layers of the dura and has been minimally investigated. It runs along the neuraxis from the orbits down to the coccyx and contains fat, valveless veins, arteries, and nerves. In the present review, we have outlined the current knowledge regarding the structural and functional significance of the EDNAC.

METHODS

We performed a narrative review of the reported EDNAC data.

RESULTS

The EDNAC can be organized into 4 regional enlargements along its length: the orbital, lateral sellar, clival, and spinal segments, with a lateral sellar orbital junction linking the orbital and lateral sellar segments. The orbital EDNAC facilitates the movement of the eyeball and elsewhere allows limited motility for the meningeal dura. The major nerves and vessels are cushioned and supported by the EDNAC. Increased intra-abdominal pressure will also be conveyed along the spinal EDNAC, causing increased venous pressure in the spine and cranium. From a pathological perspective, the EDNAC functions as a low-resistance, extradural passageway that might facilitate tumor encroachment and expansion.

CONCLUSIONS

Clinicians should be aware of the extent and significance of the EDNAC, which could affect skull base and spine surgery, and have an understanding of the tumor spread pathways and growth patterns. Comparatively little research has focused on the EDNAC since its initial description. Therefore, future investigations are required to provide more information on this underappreciated component of neuraxial anatomy.

Assessing the abilities of senior otolaryngology residents and graduated otolaryngologists in recognizing skull base elements in axial CT scan: proposing a new method for differentiating superior orbital fissure and optic canal

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate the ability of recognizing some important elements of the skull base in axial CT-scan cuts, including the optic canal (OC), superior orbital fissure (SOF), vidian canal (VC), foramen rotundum (FR), jugular foramen (JF) and hypoglossal canal (HC).

METHODS

In this study, 25 otolaryngology residents and 25 recently graduated otolaryngologists were evaluated in terms of their recognition of skull base elements, using 30 axial CT-scan cuts. Two months later, the exam related to skull base CT scans was taken in groups after a brief anatomy courses for otolaryngology residents.

RESULTS

The percentage of correct answers from otolaryngology residents regarding OC, SOF, VC, FR, JF, and HC in the first exam were 74 ± 26, 47 ± 34, 65 ± 30, 41 ± 38, 58 ± 26, and 68 ± 32, respectively. The correct answer for each element was similar between groups, and the differences were not statistically significant (p > 0.05). p value for the differences observed regarding the percentage of correct answers for the second exam between trained otolaryngology residents and recent otolaryngology graduates regarding OC and JF was no significant (p > 0.05) but significant for the other elements with better result in trained otolaryngology residents and most for SOF (p > 0.0001).

CONCLUSION

This study showed that the ability of recognition for the mentioned elements in axial CT-scan cuts was low among otolaryngology residents and graduated otolaryngologists. The proposed novel method for distinguishing SOF from OC had a powerful and long-lasting effect on trainee.

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 approaches to orbital lesions: case series and systematic literature review

OBJECTIVE

Surgical treatment of orbital lesions is challenging because complex approaches with a high risk of postoperative sequelae are required. Recently, minimally invasive endoscopic approaches through endonasal (EEA) and transpalpebral (ETP) routes have been proposed. The objective of this study was to assess outcomes of EEA and ETP in the authors' series of patients with orbital lesions.

METHODS

Data from all patients who underwent operations for an orbital tumor through an endoscopic approach at the authors' institution from 2002 to 2018 were retrospectively collected. All patients underwent preoperative MRI and ophthalmological evaluation, which was repeated 3 months after surgery and then at regular follow-up intervals. A systematic review of the literature was also performed using Medline, Embase, and Web of Science databases.

RESULTS

The series includes 23 patients (14 males); the mean patient age was 48 ± 23.9 years. Most of the lesions were intraconal (n = 19, 83%). The more frequent histotype was cavernous hemangioma (n = 5, 22%). Exophthalmos was the most common symptom (21 of 23 patients). EEA was performed in 16 cases (70%) and ETP in 7 (30%). The aim of the surgery was achieved in 94% of the cases after an EEA (successful biopsy in 5 of 6 cases and radical resection in all 10 remaining patients), and in 86% after an ETP (successful biopsy in 2 cases and radical tumor resection in 4 of 5 cases). Complications consisted of 3 cases (13%) of transitory diplopia. One recurrence (4%) was observed at follow-up (mean 59 ± 55 months).

CONCLUSIONS

The EEA and ETP have demonstrated to be safe and effective for tumors located respectively in medial and lateral quadrants, permitting one to approach orbital lesions endoscopically at 360°. Innovative surgical tools, including intraoperative ultrasonography, may be useful to potentially reduce surgical morbidity. Larger series are needed to validate these preliminary suggestions.

Relationship of the Optic Nerve to the Medial Rectus Muscle During Endonasal Dissection of the Medial Intraconal Orbital Apex

BACKGROUND

Few studies have established surgical landmarks for endoscopic endonasal dissection of the intraconal orbital apex (OA).

OBJECTIVE

We describe the optic nerve (ON) anatomy and its relationships, as seen during a fully endoscopic, endonasal approach to the medial intraconal OA.

METHODS

The study question was approached through a cadaver dissection and a radiographic study. Four formalin-fixed, latex-injected cadaver heads were dissected using transnasal endoscopic techniques. Dissection was performed using 0 degree and 30 degree nasal endoscopes and standard endoscopic sinus surgical instrumentation. A bi-nostril 4-handed technique was used. The anatomy of 8 medial OAs was evaluated and recorded. As the radiographic portion, 100 consecutively enrolled patient magnetic resonance images were evaluated, with particular attention given to the relationship of the ON to the medial rectus muscle (MRM) in 200 orbits.

RESULTS

Intraconally, the ON consistently coursed along the superior half of the MRM. Interestingly, the nerve was more easily identified from a superior approach after retracting the MRM inferiorly. With the identification of the nerve at the OA, carrying the dissection of the medial OA was easily accomplished with the ON as the guiding landmark. The radiographic portion of this study revealed a consistent relationship between the superior edge of the ON and the MRM. This relationship was maintained in the orbital apex in 98.4%-100% of the orbits examined.

CONCLUSION

The superior edge of the optic nerve is consistently found coursing along the superior half of the MRM, facilitating facile identification and further dissection navigation.

Augmented endoscopic orbital apex decompression in dysthyroid optic neuropathy

PURPOSE

To describe a modified technique of endoscopic orbital decompression for dysthyroid optic neuropathy nonresponsive to pulsed corticosteroids.

METHODS

Retrospective, interventional single centre case series included 17 consecutive patients with dysthyroid optic neuropathy (DON) who were refractory to pulse corticosteroids. Removal of the posteromedial floor and the orbital process of palatine bone (OPPB) was performed in addition to the endoscopic transethmoidal medial orbital wall decompression (ETMOWD), to achieve maximal orbital apex decompression. Main outcome measures were change in visual acuity (VA), color vision, degree of proptosis reduction, incidence of new-onset diplopia, and any complications.

RESULTS

Seventeen eyes (100%) had a statistically significant improvement in VA from 1.0 ± 0.44 LogMAR to 0.0 ± 0.15, with an average improvement of 0.41 ± 0.30 LogMAR (p 0.05, paired t-test). Fourteen out of 16 eyes had a complete improvement in color vision and two eyes had partial recovery. Afferent pupillary defect (76.5%) resolved in all cases. Five out of 10 cases with preoperative visual field defects demonstrated no residual field defects following surgery. The range of proptosis reduction was 0-5 mm (mean 2.7 ± 1.3 mm). No patients with diplopia (12/17) had worsening or developed new-onset diplopia following surgery.

CONCLUSION

Combined removal of the posterior medial floor including the OPPB with ETMOWD may be a viable alternative in the surgical management of DON.

Development of the international orbital Cavernous Hemangioma Exclusively Endonasal Resection (CHEER) staging system

BACKGROUND

Orbital cavernous hemangiomas (OCH) are the most common adult orbital tumor and represent an ideal index lesion for endonasal orbital tumor surgery. In order to standardize outcomes reporting, an anatomic-based staging system was developed.

METHODS

An international, multidisciplinary panel of 23 experts in orbital tumor surgery was formed. A modified Delphi method was used to develop the cavernous hemangioma exclusively endonasal resection (CHEER) staging system with a total of 2 rounds being completed.

RESULTS

Tumors medial to a plane along the long axis of the optic nerve may be considered amenable for an exclusively endonasal resection. In select cases, tumors may extend inferolaterally if the tumor remains below a plane from the contralateral naris through the long axis of the optic nerve (ie, plane of resectability [POR]). This definition reached consensus with 91.3% of panelists in agreement. Five stages were designed based on increasing technical resection difficulty and potential for morbidity. Stages were based on the relationship of the tumor to the extraocular muscles, the inferomedial muscular trunk of the ophthalmic artery (IMT), and orbital foramina. Staging by anatomic location also reached consensus with 87.0% of panelists in agreement. Size was not included in the staging system due to the lack of agreement on the contribution of size to resection difficulty.

CONCLUSION

Endoscopic orbital tumor surgery is a nascent field with a growing, yet heterogeneous, body of literature. The CHEER staging system is designed to facilitate international, high-quality, standardized studies establishing the safety, efficacy, and outcomes of endonasal resection of OCH.

Pure Endoscopic Lateral Orbitotomy Approach to the Cavernous Sinus, Posterior, and Infratemporal Fossae: Anatomic Study

Objective  The aim of this anatomic study is to describe a fully endoscopic lateral orbitotomy extradural approach to the cavernous sinus, posterior, and infratemporal fossae. Material and Methods  Three prefixed latex-injected head specimens (six orbital exposures) were used in the study. Before and after dissection, a computed tomography scan was performed on each cadaver head and a neuronavigation system was used to guide the approach. The extent of bone removal and the area of exposure of the targeted corridor were evaluated with the aid of OsiriX software (Pixmeo, Bernex, Switzerland). Results  The lateral orbital approach offers four main endoscopic extradural routes: the anteromedial, posteromedial, posterior, and inferior. The anteromedial route allows a direct route to the optic canal by removal of the anterior clinoid process, whereas the posteromedial route allows for exposure of the lateral wall of the cavernous sinus. The posterior route is targeted to Meckel's cave and provides access to the posterior cranial fossa by exposure and drilling of the petrous apex, whereas the inferior route gives access to the pterygopalatine and infratemporal fossae by drilling the floor of the middle cranial fossa and the bone between the second and third branches of the trigeminal nerve. Conclusion  The lateral orbitotomy endoscopic approach provides direct access to the cavernous sinus, posterior, and infratemporal fossae. Advantages of the approach include a favorable angle of attack, minimal brain retraction, and the possibility of dissection within the two dural layers of the cavernous sinus without entering its neurovascular compartment.

Compartmental Endoscopic Surgical Anatomy of the Inferior Intraconal Orbital Space

Objectives  This study aims to define the endoscopic anatomy of inferior intraconal space, in terms of its neurovascular structures and relationship to fixed anatomic landmarks. Design  A cadaveric anatomical study was conducted. Setting  This study was conducted at an academic cranial base center. Participants  Cadaveric subjects have been investigated. Main Outcome Measures  After dissection of the inferior intraconal space, the number and position of ophthalmic artery (OA) and oculomotor nerve (OMN) branches to the inferior rectus muscle (IRM) were quantified relative to the fixed landmark of the posterior maxillary wall. The point where the OMN branch to the inferior oblique muscle (IOM) crossed the lateral IRM margin was quantified. Results  A total of 18 OA branches were identified with a mean ± standard deviation of 2.6 ± 0.53 branches. The mean distance of the OA branch insertion from the posterior maxillary wall was 7.11 ± 5.65 mm. The average number of OMN branches to the IRM was 1.63 ± 0.74 with a mean insertion distance of 1.88 ± 1.89 mm. The OMN branch to the IOM crossed the lateral IRM margin 5.38 ± 5.42 mm from the posterior maxillary wall. Conclusions  This cadaveric study quantifies the variability of two critical neurovascular structures salient to endoscopic approaches to the inferior intraconal space, the OMN, and OA contributions to the IRM. Knowledge of the interrelationship between these structures is essential in safe technique for dissection.

Endoscopic Endonasal-Assisted Resection of Orbital Schwannoma

Orbital schwannomas are rare and despite a variety of external surgical approaches previously utilized, removal of tumors located in the deep orbital apex remains challenging. The endoscopic endonasal approach has been used increasingly for various apical tumours, but few describe this technique for orbital schwannomas. The authors describe 2 cases of orbital schwannoma removed via an endoscopic endonasal assisted approach. The first patient was a 31-year-old Cantonese female who was found to have an 11 × 8 × 8 mm right orbital apical schwannoma which was removed using an endoscopic endonasal sphenoethmoidal approach. The second patient was a 78-year-old white male who had a 28 × 17 × 18 mm orbital schwannoma removed via a transcaruncular and endoscopic endonasal-assisted approach. These findings suggest that the use of an endonasal approach may facilitate the safe removal of selected medially located orbital schwannomas whose posterior margins involve the orbital apex.

Anatomy of the human orbital muscle (OM): Features of its detailed topography, syntopy and morphology

The human orbital muscle (OM) is not readily accessible during ordinary anatomical teaching because of insufficient time and difficulties encountered in the preparation. Accordingly, its few anatomical descriptions are supported only by drawings, but not by photographs. The aim of this study was to present OM in dissected anatomic specimens in more detail. Following microscope-assisted dissection, its location, syntopy and morphology were analyzed in 88 orbits of 51 cadavers. Together with the periorbital connective tissue OM filled the infraorbital fissure (IOF) and extended back to the cavernous sinus. As a new finding, we here report that in 34% of the orbits we observed OM-fibers, which proceeded from IOF caudally to the facies infratemporalis of the maxilla. OM had a mean width of 4±1mm, a mean length of 22±5mm and its mean mass was 0.22±0.19g. The subsequent histological analysis of all specimens showed features of smooth muscle tissue: long, spindle-like cells with a centrally located cell nucleus (hematoxylin-eosin staining) which were innervated by tyrosine-hydroxylase immunopositive adrenergic fibers. We conclude that precise knowledge on OM might be very helpful not only to students in medicine and dentistry during anatomical dissection courses, but also to head and neck surgeons, ear-nose-throat specialists and neurosurgeons working in this field.

Endoscopic endonasal medial-to-lateral and transorbital lateral-to-medial optic nerve decompression: an anatomical study with surgical implications

OBJECTIVE Different surgical routes have been used over the years to achieve adequate decompression of the optic nerve in its canal including, more recently, endoscopic approaches performed either through the endonasal corridor or the transorbital one. The present study aimed to detail and quantify the amount of bone removal around the optic canal, achievable via medial-to-lateral endonasal and lateral-to-medial transorbital endoscopic trajectories. METHODS Five human cadaveric heads (10 sides) were dissected at the Laboratory of Surgical Neuroanatomy of the University of Barcelona (Spain). The laboratory rehearsals were run as follows: 1) preliminary preoperative CT scans of each specimen, 2) anatomical endoscopic endonasal and transorbital dissections and Dextroscope-based morphometric analysis, and 3) quantitative analysis of optic canal bone removal for both endonasal and transorbital endoscopic approaches. RESULTS The endoscopic endonasal route permitted exposure and removal of the most inferomedial portion of the optic canal (an average of 168°), whereas the transorbital pathway allowed good control of its superolateral part (an average of 192°). Considering the total circumference of the optic canal (360°), the transorbital route enabled removal of a mean of 53.3% of bone, mainly the superolateral portion. The endonasal approach provided bone removal of a mean of 46.7% of the inferomedial aspect. This result was found to be statistically significant (p < 0.05). The morphometric analysis performed with the aid of the Dextroscope (a virtual reality environment) showed that the simulation of the transorbital trajectory may provide a shorter surgical corridor with a wider angle of approach (39.6 mm; 46.8°) compared with the simulation of the endonasal pathway (52.9 mm; 23.8°). CONCLUSIONS Used together, these 2 endoscopic surgical paths (endonasal and transorbital) may allow a 360° decompression of the optic nerve. To the best of the authors' knowledge, this is the first anatomical study on transorbital optic nerve decompression to show its feasibility. Further studies and, eventually, surgical case series are mandatory to confirm the effectiveness of these approaches, thereby refining the proper indications for each of them.

640-Slice CT Measurement of Superior Orbital Fissure as Gateway for Light into the Brain: Statistical Evaluation of Area and Distance

OBJECTIVE

Our aim was to provide normative data concerning superior orbital fissure area (SOFA), ocular skin and the substantia nigra (D-SS) and orbital fissure and the substantia nigra (D-SOF-S) distances by CT scan in adult Caucasian population.

METHODS

The area of the superior orbital fissure (SOF), the distance between the ocular skin and the substantia nigra and the distance between the superior orbital fissure and the substantia nigra using CT and 3D-CT images.

RESULTS

Normative data stratified for age and gender were obtained. The data here reported show that some degree of variability in SOFA, D-SS and D-SOF-S measurements can be observed healthy Caucasian subjects. Gender stratified prediction intervals (mean +/- 2 Standard Deviations) for SOFA and D-SOF-S were 69.2 (+/-15.8) and 38.4 (+/-7.6) for male and 56.8 (+/-11.9) and 36.5 (+/-6.1) for female, respectively. Age and gender significantly impacted on D-SS values and normative data were constructed generating data stratified for these two variables. D-SS was 89.4 (+/-10.3) and 86.4 (+/-9.7) for male and female, respectively.

CONCLUSIONS

Here we provide adjunctive anatomical information on specific anatomical cerebral zones. Our data may have implications for surgeons actively committed to treat pathological conditions involving these cerebral areas. Additionally, the anatomical variability found with respect to SOF and the potential different exposure of the substanzia nigra to the bright light could play a role in Parkinson's disease as already speculated in literature.

Endoscopic endonasal study of the cavernous sinus and quadrangular space: Anatomic relationships

BACKGROUND

The quadrangular space permits an anterior entry into Meckel's cave while obviating the need for cerebral or cranial nerve retraction. This avenue is intimately associated with the cavernous sinus; thus, from this ventral perspective, it is feasible to visualize the anteromedial, anterolateral, and Parkinson triangles.

METHODS

Twenty middle cranial fossae were dissected endonasally under direct endoscopic visualization. Measurements of the surface area of the quadrangular space and the ventrally accessible cavernous sinus triangles were performed using 3 coordinates under image-guided navigation.

RESULTS

The surface area of the quadrangular space was 16.36 mm(2) (±2.89 mm(2) ). The anterolateral triangle was the largest (47.27 ± 5.37 mm(2) ), whereas Parkinson's was the smallest (22.46 ± 5.54 mm(2) ); the anteromedial triangle presented an average surface area 36.07 mm(2) (±4.15 mm(2) ).

CONCLUSION

The trajectory of the internal carotid artery (ICA) significantly impacts the quadrangular space area and may be a potential parameter for defining the feasibility of this corridor. © 2016 Wiley Periodicals, Inc. Head Neck 38: E1680-E1687, 2016.

Endonasal identification of the orbital apex

OBJECTIVES/HYPOTHESIS

To describe anatomical landmarks for endoscopic endonasal approaches to the orbital apex and to measure the distances between those landmarks.

METHODS

In this anatomic study, the nasal fossae of 30 adult fresh cadavers were dissected (n = 60 half-skulls). One double-injected orbit was carefully dissected, mainly focusing on the neurovascular structures. The orbital apex was dissected under endoscopic endonasal visualization in all cases. The distances between the ethmoidal crest and choanal arch to the optic canal (OC) and superior orbital fissure (SOF) were measured and recorded.

RESULTS

The sample was predominantly male (63.3%, 19/30 cadavers). The following correlations between measurements according to side were observed: ethmoidal crest to OC, r = 0.748 (P = 0.0001); ethmoidal crest to SOF, r = 0.785 (P = 0.0001); choanal arch to OC, r = 0.835 (P = 0.0001); choanal arch to SOF, r = 0.820 (P = 0.0001).

CONCLUSIONS

In the cadavers studied in this sample, the ethmoidal crest and choanal arch were relevant structures and exhibited consistent measurements. Spearman correlation coefficients were greater than 0.7, which is indicative of good correlation between measurements obtained in the skull halves of each cadaver. Comparison of the measurements obtained in different sides showed similar values, with no statistically significant differences in the distances between any of the proposed anatomic landmarks.

Total removal of a trigeminal schwannoma via the expanded endoscopic endonasal approach. Technical note

BACKGROUND

Because of their deep location surrounded by closed numerous neurovascular structures, skull base tumors of the cavernous sinus are still difficult to manage. Recently, the endoscopic endonasal approach commonly used for pituitary tumor resection has been "expanded" to the parasellar, infratemporal and orbital compartments with some advantages compared to the intracranial route.

METHODS

The authors reported the case of a 49-year-old male presenting a large extradural tumor of the left cavernous sinus with extensions toward the orbit, sphenoid sinus and infratemporal fossa. His ophthalmological examination was normal, and the body CT scan revealed no primary neoplasm.

RESULTS

In this operative video, the approach is described step by step with surgical nuances. The endoscopy provided a close-up panoramic view and various angles of vision. Also, it avoided an invasive craniotomy, cerebral retraction and cranial nerves damages. Thus, it allowed the total removal of this tumor originating from the maxillary branch of the trigeminal nerve. The pathologic examination confirmed a schwannoma.

CONCLUSION

The expanded endoscopic endonasal approach provides an interesting corridor to cavernous sinus tumors with satisfactory control of extensions inferiorly toward the infratemporal fossa, anteriorly via the superior orbital fissure and medially within the sphenoid. Finally, the skull base surgeon has to master this anterior endoscopic route as well as all the other "open" transcranial skull base approaches to propose the best surgical route fitting the tumor characteristics.

Endoscopic Endonasal Management of Orbital Pathologies

Based on the anatomic relationship between sinonasal complex and orbit, endoscopic transnasal procedures could be a smart solution for approaching the medial orbital region. These techniques should be considered a valid option for optic nerve or orbital wall decompression in cases of Graves ophthalmopathy and post-traumatic optic neuropathy as well as for addressing extraconal or intraconal lesions placed medially to the optic nerve course. This article describes the anatomic principles, indications, technical nuances, and limitations of the endoscopic endonasal approaches for the management of selected orbital pathologic abnormalities.

Compartmental endoscopic surgical anatomy of the medial intraconal orbital space

BACKGROUND

Surgical management of intraconal pathology represents the next frontier in endoscopic endonasal surgery. Despite this, the medial intraconal space remains a relatively unexplored region, secondary to its variable and technically demanding anatomy. The purpose of this study is to define the neurovascular structures in this region and introduce a compartmentalized approach to enhance surgical planning.

METHODS

This study was an institutional review board (IRB)-exempt endoscopic anatomic study in 10 cadaveric orbits. After dissection of the medial intraconal space, the pattern and trajectory of the oculomotor nerve and ophthalmic arterial arborizations were analyzed. The position of all vessels as well as the length of the oculomotor trunk and branches relative to the sphenoid face were calculated.

RESULTS

A mean of 1.5 arterial branches were identified (n = 15; range, 1-4) at a mean of 8.8 mm from the sphenoid face (range, 4-15 mm). The majority of the arteries (n = 7) inserted adjacent to the midline of medial rectus. The oculomotor nerve inserted at the level of the sphenoid face and arborized with a large proximal trunk 5.5 ± 1.1 mm in length and multiple branches extending 13.2 ± 2.7 mm from the sphenoid face. The most anterior nerve and vascular pedicle were identified at 17.0 and 15.0 mm from the sphenoid face, respectively.

CONCLUSION

The neurovascular supply to the medial rectus muscle describes a varied but predictable pattern. This data allows the compartmentalization of the medial intraconal space into 3 zones relative to the neurovascular supply. These zones inform the complexity of the dissection and provide a guideline for safe medial rectus retraction relative to the fixed landmark of the sphenoid face.

Endoscopic endonasal approach to the maxillary strut: anatomical review and case series

OBJECTIVES/HYPOTHESIS

The maxillary strut is the bone that separates the foramen rotundum and superior orbital fissure. Tumors involving the lateral wall of the sphenoid sinus, posterior ethmoid, or posterior maxillary sinus may invade this region. The authors detail the anatomy of the strut and present a case series that emphasizes the importance and utility of this useful landmark during an endoscopic endonasal approach to lesions in this region.

STUDY DESIGN

Cadaveric dissections and retrospective case series.

METHODS

Endoscopic endonasal dissections were performed on six formalin-fixed cadaver heads. Morphometric analyses of 100 skulls were conducted using CT scans and BrainLab. Four patients underwent procedures that exposed the maxillary strut.

RESULTS

The maxillary strut was trapezoidal shaped with an average cross-sectional area of 15.25 ± 0.48 mm(2) and average thickness of 4.43 ± 0.10 mm. The maxillary strut was present bilaterally in all skulls examined. Anteroposterior length averaged 4.18 ± 0.15 mm on the right and 3.90 ± 0.14 mm on the left. Our patient series illustrated the clinical utility of the maxillary strut as a landmark during endoscopic approaches to the skull base.

CONCLUSIONS

An endoscopic endonasal approach can be used to expose the maxillary strut. Improved understanding of this anatomy is important to achieving success when using this approach for the biopsy or resection of lesions in the lateral sellar compartment, pterygopalatine fossa, and aspects of the middle cranial fossa.

Quantitative study on endoscopic endonasal approach to the posterior sino-orbito-cranial interface: implications and clinical considerations

The posterior sino-orbito-cranial interface is a critical area in the skull base since it represents a gateway to deeper vital regions. Quantification of the surgical freedom for any given point/area is an objective method for comparing in a reproducible way different surgical approaches. Three freshly injected cadaver heads (six sides) were dissected under the magnetic navigation control system. The surgical freedom (SF) and the angle of attack of fixed target points were determined from the ipsilateral nasal fossa, from the contralateral nasal fossa (after posterior septectomy), and after an anteromedial maxillotomy (according to the Denker procedure). The mean pre-operative SF value resulted to be 403.07 ± 102.73 mm(2) for the ipsilateral nostril, increasing by 126.97 % for the binostril approach, by 118.45 % for the monolateral nostril approach after anteromedial maxillotomy, and by 310.48 % for the binostril approach after bilateral anteromedial maxillotomy. Laterally extended lesions require an anteromedial maxillotomy, while more medially located lesions can be managed by means of a posterior septectomy. When addressing the posterior sino-orbito-cranial interface, the transnasal binostril approach and anteromedial maxillotomy both increase the SF. The choice between them depends on exact position, relationship and clinical behaviour of the lesion to treat.