Endoscopic endonasal surgical anatomy of the optic canal: key anatomical relationships between the optic nerve and ophthalmic artery

Origin and Course Cavernous Internal Carotid Artery Branches from the Endoscopic Endonasal Perspective: Cadaveric Study and Analysis Clinical Implications

BACKGROUND AND OBJECTIVE

Endoscopic endonasal approaches to treat cavernous sinus lesions require detailed knowledge of the origin, course, and anatomic variations of the branches of the cavernous internal carotid artery (cICA) because inadvertent avulsion can cause intraoperative ICA injury. We aim to study the origin and course of the branches of the cICA from an endoscopic endonasal perspective and relate these branches to surgically relevant anatomic references.

METHODS

Sixty sides of 30 formalin-fixed specimens were dissected to identify the origin and course of cICA branches, including the inferolateral trunk (ILT), the meningohypophyseal trunk (MHT), anterior and inferior McConnell's capsular arteries (MCAs), and the superolateral trunk (SLT).

RESULTS

The ILT and MHT were bilaterally in all specimens, whereas the anterior and inferior MCAs were identified in 28% and 25% of dissected sides, respectively. The SLT was only found in 3% of sides dissected. The MHT was the most proximal branch of the cICA, and its origin was an average of 8.9 mm anterior to the foramen lacerum and 3.8 mm superior to the sellar floor. The ILT was the second most proximal branch of the cICA, which originated 6.4 mm from the MHT on average. The anterior and inferior MCAs were present in 28% and 25% of specimens, respectively. The SLT, when present, was the second most proximal branch of the cICA, which originated at a mean height of 2.7 mm from the sellar floor. Overall, complete ILT and MHT were identified in 68% and 77% of cases, respectively.

CONCLUSION

The MHT and ILT are constant branches of the cICA, with the MHT originating from the medial cICA posterior bend 4 mm superior to the sellar floor and 9 mm anterior to the foramen lacerum, whereas the ILT arises from the lateral horizontal cICA, 2.3 mm superior to the sellar floor and 6 mm anterior to the MHT.

Cranio-Orbital Approach and Decompression of the Optic Nerves: A 2-Stage, 4-by-4-Step Approach to Improve Vision in Sellar and Parasellar Lesions

BACKGROUND AND OBJECTIVES

Despite advances in cranial base techniques, surgery of the sellar and parasellar regions remains challenging because of complex neurovascular relationships. Lesions within this region frequently present with progressive visual deterioration caused by distortion and compression of the optic chiasm and nerves. In addition to the direct mass effect from mechanical forces acting on the optic apparatus, these lesions alter blood supply and reduce vascular perfusion, prompting surgical treatment to remove the lesion, alleviate compression, and improve blood flow to the optic nerve. We sought to describe a 2-stage, 4-by-4-step approach, broken down and described as a "four-by-four" technique for optic apparatus decompression and a wide approach to different sellar and parasellar lesions.

METHODS

We describe the operative nuances and key anatomic points in the microsurgical removal of sellar and parasellar lesions. The technique is illustrated with examples of different cases with pre- and follow-up MRI imaging and a brief overview of visual outcomes.

RESULTS

The described technique has been demonstrated in various lesions in 5 patients. Patients presented with bilateral visual loss in 4 (80.0%) cases and with unilateral visual loss in 1 (20.0%) case. Improvement in visual function was noted in all cases, confirmed with visual acuity and visual field testing.

DISCUSSION

The transcranial approach ("from above") remains an important surgical option for patients with excellent exposure and visualization of the sellar and parasellar regions. It permits early access to the optic canal for careful microsurgical decompression and relaxation of the optic nerve to preserve and improve its microvascularization and ultimately vision.

CONCLUSION

The authors augmented the 2-stage, 4-by-4-step technique of decompression with elaborate illustrations of diverse sellar and parasellar lesions to demonstrate the versatility of this approach.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Endoscopic Endonasal Approach to the Anterior Cranial Fossa

Introduction  The development of endoscopic techniques has made endoscopic endonasal approaches (EEAs) to the anterior cranial fossa (ACF) increasingly popular. Still, the steps and nuances involved in the approach may be difficult to understand for trainees. Thus, we aim to didactically describe the EEAs to the ACF in an anatomically based, step-by-step manner with supplementary clinical cases. Methods  Six cadaveric head specimens were dissected. Endoscopic endonasal Draf I, IIA, IIB, and III frontal sinusotomies, endoscopic endonasal superior ethmoidectomy, and endoscopic endonasal transcribriform and transplanum approaches were modularly performed. The specimens were photodocumented with endoscopic techniques. Results  Draf I frontal sinusotomy started with the complete removal of the anteromedial portion of the agger nasi cell, exposing the medial orbital wall, cranial base, and anterior cribriform plate. Draf II frontal sinusotomy proceeded with the removal of the floor of the frontal sinus between the lamina papyracea and the middle turbinate (IIa), and the nasal septum (IIb) until the first olfactory filaments were exposed. Draf III proceeded by creating a superior septal window just below the floor of the frontal sinus. The bone of the ACF bounded by the limbus sphenoidale posteriorly, frontal sinus anteriorly, and the medial orbital walls bilaterally was removed; the cribriform plate was removed; and the crista galli was dissected free from the dural leaflets of the falx cerebri and removed. Conclusion  We provide a step-by-step dissection describing basic surgical steps and anatomy of the EEAs to the ACF to facilitate the learning process for skull base surgery trainees.

Endoscopic Optic Nerve Decompression in a Hamamy Syndrome Patient With Bilateral Optic Canal Stenosis

Hamamy Syndrome is an autosomal recessive syndrome with craniofacial, neurological, and osteological implications. Patients most commonly present with repeated long fractures however, other affected systems with their respective clinical presentations warrant a thorough reporting and understanding of this genetic disorder. Herein, the authors, present a 21-year-old male patient diagnosed with Hamamy Syndrome with bilateral stenosis of the optic canals and associated bilateral vision loss. This case report documents the patient's initial presentation 6 years ago, which included a history of right vision loss for 2 months, followed by a 6-year follow-up period during which the patient underwent 3 optic nerve decompression surgeries. There is currently a limited number of reports in the English literature on Hamamy Syndrome, with the primary focus being on genetic, dental, orthopedic, and neuropsychiatric aspects, but the neural foraminal narrowing with associated neuropathy has never been reported.

Endoscopic endonasal decompression of the optic nerve in the setting of compressive lesions: how I do it

BACKGROUND

Many lesions in the anterior skull base may compress the optic nerve (ON), leading to vision loss, and even irreversible blindness. Although decompression of the optic nerve has traditionally been achieved transcranially, the endoscopic endonasal approach (EEA) is gaining traction as a minimally invasive approach recently.

METHOD

We describe the key steps of an EEA ON decompression. The relevant surgical anatomy with illustration is described. Additionally, a video detailing our technique and instruments on an illustrative case is provided.

CONCLUSION

Endoscopic endonasal approach ON decompression with a straight feather blade is a feasible, minimally invasive procedure to decompress the ON in the setting of anterior skull base mass 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.