Compartmental Endoscopic Surgical Anatomy of the Inferior Intraconal Orbital Space

Anatomy of the medial wall of the orbit undergoing an endoscopic endonasal approach: An inferomedial and superomedial approach

Background

Endoscopic endonasal corridor is valuable for accessing and treating midline skull base pathologies. In the present work, we will discuss the anatomy of the medial wall of the orbit from an endonasal endoscopic perspective.

Methods

Six human cadaveric specimens underwent endonasal endoscopic dissection at the Surgical Neuroanatomy Laboratory of the Mexican Faculty of Medicine of La Salle University. We used a 0°, 4 mm diameter, and 18 cm length rigid endoscope using a 4K high-definition neuro-endoscopic visualization system, specialized surgical instruments for endonasal endoscopic surgery, and a high-speed drilling system.

Results

In the endonasal endoscopic to the medial wall of the orbit, we describe two approaches: the superomedial approach (SMA) and the inferomedial approach (IMA). The SMA is located between the lower border of the superior oblique muscle and the superior border of the medial rectus muscle (MRM), and the IMA is located between the inferior border of the MRM and the superior border of the inferior rectus muscle. The topographic anatomy of the contents of each approach is described.

Conclusion

The endoscopic endonasal corridor safely reaches the medial half of the orbit through the inferomedial and SMAs.

Endoscopic Endonasal Approach to Intraconal Orbital Tumors: Outcomes and Lessons Learned

BACKGROUND

Lesions involving the intraconal space of the orbit are rare and challenging to manage. Operative techniques and outcomes for the endoscopic endonasal approach (EEA) to tumors in the medial intraconal space (MIS) remain poorly characterized.

OBJECTIVE

We present our experience with a wide range of isolated intraconal pathology managed via an EEA.

METHODS

A retrospective review of all cases (2014-2021) performed by a single skull base team in which the EEA was employed for the management of an intraconal orbital lesion.

RESULTS

Twenty patients (13 men, 7 women) with a mean age of 59 years (range, 40-89 years) were included. All lesions were isolated to the MIS, pathology addressed included: cavernous hemangioma (6), schwannoma (4), lymphoma (4), inflammatory pseudotumor (2), chronic invasive fungal sinusitis (2), and metastatic disease (2). Either a biopsy (10/20) or a complete resection (10/20) was performed. In all cases, the MIS was accessed via an endonasal corridor between the medial and inferior rectus muscles. Retraction and safe, intra-orbital dissection of the lesion was performed using a two-surgeon, multi-handed technique. Gross total resection of benign lesions was achieved in 90% (9/10) of cases; a pathologic diagnosis was achieved in 100% (10/10) of biopsy cases. No orbital reconstruction was required. Visual acuity returned to normal in 80% (8/10) of planned resection cases and postoperative diplopia resolved by 3 months in 90%. Mean follow-up was 15 months.

CONCLUSION

This study demonstrates that the EEA is safe and effective for accessing lesions in the MIS. This technique affords very favorable outcomes with minimal postoperative morbidity.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:47-55, 2024.

Morphometric Analysis of the Ophthalmic and Central Retinal Arteries via the Endoscopic Endonasal Trans-ethmoidal Approach: Surgical Relevance of Vascular Components Within the Medial Intraconal Zones

BACKGROUND

The endoscopic endonasal approach (EEA) offers a minimally invasive route to treat medial intraconal space (MIS) lesions. Understanding the configuration of the ophthalmic artery (OphA) and the central retinal artery (CRA) is crucial.

METHODS

An EEA to the MIS was performed on 30 orbits. The description of the intraorbital part of the OphA was divided into 3 segments and classified as type 1 and type 2 and the MIS was divided into three surgical zones (A, B, C). The CRA's origin, course, and point of penetration (PP) were analyzed. The relationship between the position of the CRA in the MIS and the OphA type was analyzed.

RESULTS

The OphA type 2 was present in 20% of specimens. The site of origin of the CRA from the OphA was found on the medial surface in type 1 and on the lateral surface of type 2. The point of penetrationof the central retinal arterywas found in 87% of the specimens on the inferomedial surface, just anterior to the inferior muscular trunk, at an average distance of 9.5 mm ± 1 from the globe and 17 mm ± 1.5 from the AZ. The presence of the CRA in Zone C was associated only with OphA type 1.

CONCLUSIONS

OphA type 2 is a common finding and can compromise the feasibility of an EEA to the MIS. A detailed preoperative analysis of the OphA and CRA should be conducted prior to approaching the MIS due to the implications of the anatomical variations that can compromise safe intraconal maneuverability during an EEA.

Comparative endoscopic techniques of medial rectus muscle retraction for approaching intraconal tumors: Our experience with five cases

Objective

To examine the role of transnasal endoscopic approaches in the management of intraconal tumors and demonstrate the use of an eyelid speculum in comparison with different techniques of medial rectus muscle (MRM) retraction.

Methods

Retrospective data of five patients with intraconal tumors operated on and followed up by the senior authors between December 2019 and April 2022 was collected. Presenting symptoms, technical details, imaging and histology findings, outcomes, and complications were evaluated.

Results

Four primary and one recurrent tumor were identified. The mean patient age was 50 (range, 29–64) years. One tumor was located lateral to the optic nerve, one central and three medial. A complete surgical resection was obtained in four primary cases and a partial resection was achieved in the recurrent case. The MRM was retracted using three different techniques: (1) an infant eyelid speculum creating an operative window between the medial and inferior rectus muscle, (2) external MRM disinsertion transconjunctivally, (3) a four-handed technique performed transseptally by two surgeons. Transient postoperative ophthalmoplegia was recorded in four cases and transient ptosis in one. Three patients completely recovered in 2–3 months while one undergoing MRM disinsertion ended up in restricted strabismus at 15-month follow-up. No other long-term complications have been noted in all five patients with a mean follow-up of 22 (range, 14–32) months. No patients with primary tumors have required additional surgery for tumor recurrence.

Conclusion

The indication of endoscopic intraconal surgery may expand to lesions lateral to the optic nerve when the nerve is not in its natural position. The well-known advantages of the endoscopic techniques, namely the lack of external scars, better visualization, less bleeding, and fewer complications, were confirmed. An eye speculum provides a better surgical corridor and eases the pressure exerted on the MRM, which has a promising application prospect.

Endoscopic sublabial transmaxillary approach to the inferior orbit: pearls and pitfalls-A comparative anatomical study

OBJECTIVE

Although orbital surgery has always represented a challenge for neurosurgeons, keyhole and endoscopic techniques are gradually surging in popularity maximizing functional and esthetic outcomes. This quantitative anatomical study first compared the surgical operability achieved through three endoscopic approaches within the inferior orbit: the endoscopic sublabial transmaxillary (ESTMax), the endoscopic endonasal transethmoidal (EETEth), and the endoscope-assisted lateral orbitotomy (ELO).

METHODS

Each of these approaches was performed bilaterally on five specimens. We described the ESTMax step-by-step, underlining its advantages and pitfalls in comparison with EETEth and ELO. Then, we assessed surgical measurements and operability in ESTMax, EETEth, and ELO.

RESULTS

The ESTMax provided the most favorable operative window (278.9 ± 43.8 mm²; EETEth: 240.8 ± 21.5 mm², p < 0.001; ELO: 263.1 ± 19.8 mm², p = 0.006), the broadest surgical field area (415.9 ± 26.4 mm²; EETEth: 386.7 ± 30.1 mm², p = 0.041; ELO: 305.2 ± 26.3 mm², p < 0.001), surgical field depths significantly shorter than EETEth (p < 0.001) but similar to ELO, the widest surgical angles of attack (45°-65°; EETEth: 20°-30°, p < 0.001; ELO: 25°-50°, p < 0.001), and the greatest surgical mobility areas (EETEth: p < 0.001; ELO: p < 0.001). Furthermore, the ESTMax allowed multi-angled exposure and handy maneuverability around all the inferior intraorbital targets. Small anterior antrostomy, blunt intraorbital dissections, direct targets' approach, orbital floor reconstruction, and maxillary bone flap replacement may limit the ESTMax morbidity rates.

CONCLUSIONS

The ESTMax is a minimally invasive "head-on" orbital approach that exploits endoscopic surgery advantages avoiding the cranio-orbital and trans-nasal approach limitations and possible complications. It represents a promising alternative to EETEth and ELO because of its optimal operability for resecting lesions extending into the entire inferior orbit.

Radioanatomic Characteristics of the Posteromedial Intraconal Space: Implications for Endoscopic Resection of Orbital Lesions

BACKGROUND AND PURPOSE

Imaging is essential in the diagnostic work-up of patients with orbital lesions. The position of an orbital lesion relative to the inferomedial muscular trunk of the ophthalmic artery determines endoscopic resectability, anticipated technical difficulty, and patient morbidity. Although the inferomedial muscular trunk is not readily identifiable on preoperative imaging, we hypothesize that it is spatially approximate to the location where the ophthalmic artery crosses the optic nerve. Our aim was to determine whether the ophthalmic artery-optic nerve crosspoint anatomically approximates the inferomedial muscular trunk in a cadaver study and can be appreciated on imaging of known posteromedial orbital lesions.

MATERIALS AND METHODS

Dissection was performed on 17 fresh-frozen cadaver orbits to assess the relationship between the inferomedial muscular trunk and ophthalmic artery-optic nerve crosspoint. Retrospective review of imaging in 9 patients with posteromedial orbital lesions assessed posteromedial orbital compartment characteristics and the ability to locate the ophthalmic artery-optic nerve crosspoint.

RESULTS

In our cadaver study, the mean distance between the ophthalmic artery-optic nerve crosspoint and the inferomedial muscular trunk was 1.21 ± 0.64 mm. Retrospectively, the ophthalmic artery-optic nerve crosspoint was identifiable in 9/9 patients, whereas the inferomedial muscular trunk was not identifiable in any patient. Total or partial effacement of the posteromedial intraconal fat triangle was observed in 9/9 patients.

CONCLUSIONS

This study of neurovascular relationships within the posteromedial orbit demonstrates that the ophthalmic artery-optic nerve crosspoint closely approximates the inferomedial muscular trunk and can be seen in patients with posteromedial orbital lesions. Posteromedial intraconal fat effacement may help to localize these lesions. These findings may facilitate multidisciplinary communication and help predict lesion resectability and patient outcomes.

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.

Endoscopic Endonasal Approaches to the Medial Intraconal Space: Comparison of Transethmoidal and Prelacrimal Corridors

BACKGROUND

Endoscopic transethmoidal and prelacrimal approaches can access the medial intraconal space (MIS).

OBJECTIVE

This study aimed to compare advantages and drawbacks of these two approaches, and to explore their appropriate indications for management of lesions at various locations within the MIS.

METHODS

Six injected cadaveric specimens were dissected using an endonasal approach performing a transethmoidal approach on one side and a prelacrimal approach on the contralateral side. The MIS was divided into three Zones: Zone 1 was defined as the area above the superior border of the medial rectus muscle (MRM), Zone 2 as the area between the MRM and the optic nerve, and Zone 3 as the area below the inferior border of MRM. The exposure provided by these two approaches to various Zones within the MIS was assessed and compared.

RESULTS

The average height of Zone 1 to 3 was 10.35 ± 0.45 mm, 11.07 ± 0.59 mm, and 6.53 ± 0.59 mm, respectively. Both approaches provided adequate exposure of Zone 2 and 3; however, the prelacrimal approach provided direct exposure of the posterosuperior aspect of Zone 2 without retraction of MRM. Retraction of MRM was unavoidable using a transethmoidal approach to enhance further exposure. Access to Zone 1 was adequately achieved through the corridor between superior oblique muscle and MRM via a transethmoidal corridor.

CONCLUSION

Conceptualizing the MIS into the three aforementioned Zones seems beneficial to select the optimal approach for lesions restricted to each specific Zone. Both the transethmoidal and prelacrimal approaches provide adequate exposure for select lesions in the MIS.

Transnasal prelacrimal approach to the inferior intraconal space: a feasibility study

BACKGROUND

Endonasal access to the inferomedial and inferolateral intraconal space via the orbital floor has not been reported. The primary purpose of this study was to assess the feasibility of accessing the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. Secondarily, it aims to highlight anatomical relationships of neurovascular structures in this space, as a requirement to prevent complications.

METHODS

Six cadaveric heads (12 sides) were dissected using a transnasal prelacrimal approach. The orbital floor, medial to the infraorbital canal, was removed and the periorbita opened to expose the inferior rectus muscle. The inferomedial and inferolateral intraconal space was accessed alongside the medial and lateral border of inferior rectus muscle, respectively. Various anatomical relationships of adjacent neurovascular structures were recorded, and the distances among the recti muscles and optic nerve were also measured.

RESULTS

The infraorbital nerve is located at the inferolateral aspect of inferior rectus muscle. In the inferomedial intraconal space, we identified the inferomedial muscular trunk of the ophthalmic artery, optic nerve, and branches of the oculomotor nerve; whereas the inferolateral intraconal space contained the inferolateral muscular trunk of ophthalmic artery, branches of the oculomotor and nasociliary nerve, and abducens nerve. Distances from the medial, inferior, and lateral recti muscles to the optic nerve were (mean ± standard deviation) 4.70 ± 1.18 mm, 5.60 ± 0.93 mm, and 7.98 ± 1.99 mm, respectively. Distances from the inferior rectus muscle to the inferior borders of medial and lateral recti muscles were 4.45 ± 1.23 mm and 8.77 ± 1.80 mm.

CONCLUSION

It is feasible to access the inferior intraconal space through the orbital floor via a transnasal prelacrimal approach. The access may be subdivided into inferomedial and inferolateral corridors according to the entry point at the medial or lateral border of the inferior rectus muscle. Neurovascular structures in the inferior intraconal space are visualized directly, which should enhance their preservation.

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.