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

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.

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.

Intraconal Anatomy of the Anterior Ethmoidal Neurovascular Bundle: Implications for Surgery in the Superomedial Orbit

Background

The anterior ethmoidal artery (AEA) branches from the ophthalmic artery in the superomedial intraconal space. The feasibility of management of lesions arising from the superomedial intraconal space via an endoscopic endonasal approach has not been sufficiently explored.

Objective

To yield a detailed anatomic description of the anterior ethmoidal neurovascular bundle and its variants to serve as the foundation for possible management of lesions in the superomedial intraconal space.

Methods

Eight cadaveric specimens (16 sides) were dissected using an endonasal approach, tracing the AEA proximally through the superomedial intraconal space. Furthermore, the anatomy of adjacent structures was noted, and distances from the anterior ethmoidal foramen to the origin of the AEA at the ophthalmic artery were measured.

Results

Supraorbital cells were found in 13/16 sides (81.25%), and a bony dehiscence of the anterior ethmoidal canal was observed in 5/16 sides (31.25%). The nasociliary nerve, ophthalmic artery, superior division of the oculomotor nerve, superior rectus muscle, and levator palpebrae superioris were routinely identified in the superomedial intraconal space. The AEA passed through a corridor between the medial rectus and superior oblique muscles after arising from the ophthalmic artery (lateral to the foramen) in all specimens. The average distance from its origin to the anterior ethmoidal foramen was 5.19 ± 0.98 mm.

Conclusion

Anatomically, it is feasible to access the superomedial intraconal space via an endoscopic endonasal approach. This study provides the anatomical basis for procedures in the superomedial intraconal space.