Background and objectives: The superior eyelid endoscopic transorbital approach has rapidly gained popularity among neurosurgeons for its advantages in the treatment, in a minimally invasive fashion, of a large variety of skull base pathologies. In this study, an anatomic description of the internal carotid artery (ICA) is provided to identify risky zones related to lesions that may be approached using this technique. In this framework, a practical roadmap can help the surgeon to avoid potentially life-threatening iatrogenic vascular injuries.

Methods: Eight embalmed adult cadaveric specimens (16 sides) injected with a mixture of red latex and iodinate contrast underwent superior eyelid transorbital endoscopic approach, followed by interdural dissection of the cavernous sinus, extradural anterior clinoidectomy, and anterior petrosectomy, to expose the entire "transorbital" pathway of the ICA. Furthermore, the distance of each segment of the ICA explored by means of the superior eyelid endoscopic transorbital approach was quantitatively analyzed using a neuronavigation system.

Results: We exposed 4 distinct ICA segments and named the anatomic window in which they are displayed in accordance with the cavernous sinus triangles distribution of the middle cranial fossa: (1) clinoidal (Dolenc), (2) infratrochlear (Parkinson), (3) anteromedial (Mullan), and (4) petrous (Kawase). Critical anatomy and key surgical landmarks were defined to further identify the main danger zones during the different steps of the approach.

Conclusion: A detailed knowledge of the reliable surgical landmarks of the course of the ICA as seen through an endoscopic transorbital route and its relationship with the cranial nerves are essential to perform a safe and successful surgery.

Objective: The endoscopic superior eyelid transorbital approach has garnered significant consideration and gained popularity in recent years. Detailed anatomical knowledge along with clinical experience has allowed refinement of the technique as well as expansion of its indications. Using bone as a consistent reference, the authors identified five main bone pillars that offer access to the different intracranial targeted areas for different pathologies of the skull base, with the aim of enhancing the understanding of the intracranial areas accessible through this corridor.

Methods: The authors present a bone-oriented review of the anatomy of the transorbital approach in which they conducted a 3D analysis using Brainlab software and performed dry skull and subsequent cadaveric dissections.

Results: Five bone pillars of the transorbital approach were identified: the lesser sphenoid wing, the sagittal crest (medial aspect of the greater sphenoid wing), the anterior clinoid, the middle cranial fossa, and the petrous apex. The associations of these bone targets with their respective intracranial areas are reported in detail.

Conclusions: Identification of consistent bone references after the skin incision has been made and the working space is determined allows a comprehensive understanding of the anatomy of the approach in order to safely and effectively perform transorbital endoscopic surgery in the skull base.

Indications corridor and limits of exposure: The major indications of endoscopic transorbital approach include spheno-orbital meningiomas, cavernous sinus lesions, and Meckel cave lesion such as trigeminal schwannomas. It can avoid excessive brain retraction and allows for a fast recovery to the normal daily living activity.

Anatomic essentials need for preoperative planning and assessment: To access the cavernous sinus, the sagittal crest and meningo-orbital band should be identified and cut.

Essential steps of the procedure: 1. Skin incision along the superior eyelid is performed. 2. Careful dissection of the soft tissue under the orbicularis is required not to injure the orbital septum. 3. After the lateral orbital rim is exposed, the periosteum and periorbita are elevated from the lateral orbital wall. 4. Drilling of the zygomatic bone within the orbit exposes the temporalis muscle first followed by the exposure of the temporal dura. It is essential to obtain adequate working room when the base of the greater sphenoidal wing is drilled. The sagittal crest should be removed, and the meningo-orbital band should be cut to expose the lateral cavernous sinus wall.

Pitfalls/avoidance of complications: For successful access through the orbit, endoscopic transorbital approach needs to minimize the retraction of the orbit. To achieve this goal, retraction of the orbit should be limited to a maximum of 10 minutes.

Variants and indications of their use: This approach can be combined with lateral orbitotomy. It provides a wider working room and makes surgery easier to access the lateral temporal lobe.The patient consented to the procedure, and the participants and any identifiable individuals consented to publication of his/her image. 

Objective: The endoscopic transorbital approach (ETOA) and transorbital anterior clinoidectomy have been suggested as novel procedures through which to reach the superolateral compartments of the orbit, allowing optic canal decompression. However, there is limited literature describing the technical details and surgical outcomes of these procedures. In this study, the authors aimed to analyze the feasibility and efficacy of endoscopic transorbital decompression of the optic canal through anterior clinoidectomy for compressive optic neuropathic lesions.

Methods: Between 2016 and 2022, the authors performed ETOA for compressive optic neuropathic lesions in 14 patients. All these patients underwent transorbital anterior clinoidectomy through the surgically defined "intraorbital clinoidal triangle," which is composed of the roof of the superior orbital fissure, the medial margin of the optic canal, the medial border of the superior orbital fissure, and the optic strut. Demographic data, tumor characteristics, pre- and postoperative imaging, pre- and postoperative visual examinations, and surgical outcomes were retrospectively reviewed.

Results: The mean age at the time of ETOA was 53.3 years (range 41-64 years), and the mean follow-up was 16.8 months (range 6.7-51.4 months). The inclusion criterion in this study was having a meningioma (14 patients). In the preoperative visual function examination, 7 patients with a meningioma showed progressive visual impairment. After endoscopic transorbital optic canal decompression, visual function improved in 5 patients, remained unchanged in 8 patients, and worsened in 1 patient. No new-onset neurological deficit was associated with ETOA and anterior clinoidectomy in any patients.

Conclusions: Endoscopic transorbital decompression of the optic canal with extradural anterior clinoidectomy is a safe and feasible technique that avoids significant injury to the clinoidal internal carotid artery and surrounding neurovascular structures.

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

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

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

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

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