The Endoscopic Transorbital Approach for Vascular Surgery: An Anterior Circulation Anatomic Study, 2-Dimensional Operative Video.

BACKGROUND AND OBJECTIVES: Minimally invasive endoscopic approaches in cranial base surgery have been developing in the past decades. The transorbital (TO) route is one promising alternative, yet its adequacy for intracranial vascular lesions remains unclear. The present anatomic work aimed to test the feasibility and to provide a qualitative description of the endoscopic TO approach for the anterior circulation, namely the internal carotid artery and the middle cerebral artery. METHODS: Seven embalmed adult cadaveric specimens (12 sides) were used in the study. Each side was approached in 3 successive steps: (1) Superior-eyelid TO approach, with great and lesser sphenoid wing removal. (2) Removal of anterior clinoid process (ACP). (3) Removal of the lateral orbital rim. All the procedures were performed under endoscopic view. RESULTS: The TO approach without removing the ACP allowed to dissect the sphenoidal and lateral segments of the Sylvian fissure with an adequate identification of the middle cerebral artery bifurcation in all specimens. The removal of the ACP allowed further dissection toward the opticocarotid cistern, with the identification of the ophthalmic, posterior communicating, and the anterior choroidal arteries. The internal carotid artery bifurcation and A1 segment were also readily identified. Finally, removal of the lateral orbital rim provided a wider and more comfortable access to the above-mentioned vascular structures. CONCLUSION: According to our anatomic data, the TO approach can be used to reach the main vascular components of the anterior circulation. This opens the field for exploring its application in the treatment of vascular pathology, particularly aneurysms.

Transorbital Route to Intracranial Space.

The endoscopic superior eyelid transorbital approach has emerged as a notable and increasingly utilized surgical technique in recent years. This chapter presents an overview of the approach, tracing its historical development and highlighting its growing acceptance within the skull base community.Beginning with an introduction and historical perspective, the chapter outlines the evolution of the transorbital approach, shedding light on its origins and the factors driving its adoption. Subsequently, a comprehensive exploration of the anatomic bone pillars and intracranial spaces accessible via this approach is provided. Hence, five bone pillars of the transorbital approach were identified, namely the lesser sphenoid wing, the anterior clinoid, the sagittal crest, the middle cranial fossa, and the petrous apex. A detailed correlation of those bone targets with respective intracranial areas has been reported.Furthermore, the chapter delves into the practical application of the technique through a case example, offering insights into its clinical utility, indications, and limitations.

Endoscopic transorbital approach to the petrous apex: is orbital rim removal worthwhile for the exposure? An anatomical study with illustrative case.

OBJECTIVE: The endoscopic transorbital approach (ETOA) has been demonstrated to be a feasible ventral route to the petrous apex. Yet, it has been pointed to as a deep and narrow corridor for anterior petrosectomy; particularly, medialization of the instruments can become an issue when targeting the petroclival area. To overcome this limitation, an ETOA with orbital rim removal (ETOA-OR) has been suggested, but not de facto compared, with a transorbital approach without removal of the rim. This addition could augment the surgical exposure and freedom of movement when accessing the petrous apex area. METHODS: Five human cadaveric heads (10 sides) were dissected. First, anterior petrosectomy was performed via a conventional ETOA (without orbital rim removal). Second, en bloc removal of the orbital rim was performed, with enlargement of the orbital craniectomy and, subsequently, further drilling of the medial petrous apex. Qualitative and quantitative comparisons are provided. An illustrative surgical case is also shown. RESULTS: The transorbital route allowed the authors to perform an anterior petrosectomy in all specimens. The landmarks of bone removal are superposed onto those in the transcranial route. The ETOA-OR increased the volume of craniectomy (from 4.0 mL to 5.5 mL), the lateromedial angulation, and superoinferior angulation of the instruments within the petrous area. Thus, this approach improved the exposure of the medial petroclival area, allowing for an augmented petrosectomy (from 1.4 mL to 2.0 mL, 39.5% increase) and for increased maneuverability, both in the petrous area (from 44.1 cm2 to 76.5 cm2, 73.3% increase) and in the posterior fossa (from 20.2 cm2 to 52.0 cm2, 158% increase). The ETOA-OR was also pragmatically applied to treat a recurrent petroclival meningioma. Complete removal was achieved, the abducens nerve palsy improved, and the trigeminal neuralgia decreased in severity, yet still required medication. CONCLUSIONS: The authors provide the first formal anatomical comparison between the transorbital approach with preservation of the orbital rim and a transorbital approach with removal of the rim to access the petrous apex. In addition, an illustrative case is used as a proof of concept and feasibility. According to the authors' data, the ETOA-OR significantly improves surgical exposure and the surgeon's comfort in this deep region. The bony defect can be reconstructed to avoid cosmetic deformities, maintaining the minimally disruptive concept of transorbital surgery.

Effects of the Use of Neuronavigation in Patients with Supratentorial Brain Gliomas: A Cohort Study.

OBJECTIVE: Despite the growing acceptance of neuronavigation in the field of neurosurgery, there is limited comparative research with contradictory results. This study aimed to compare the effectiveness (tumor resection rate and survival) and safety (frequency of neurological complications) of surgery for brain gliomas with or without neuronavigation. METHODS: This retrospective cohort study evaluated data obtained from electronic records of patients who underwent surgery for gliomas at Dr. Alejandro Dávila Bolaños Military Hospital and the Clinic Hospital of Barcelona between July 2016 and September 2022. The preoperative and postoperative clinical and radiologic characteristics were analyzed and compared according to the use of neuronavigation. RESULTS: This study included 110 patients, of whom 79 underwent surgery with neuronavigation. Neuronavigation increased gross total resection by 57% in patients in whom it was used; gross total resection was performed in 56% of patients who underwent surgery with neuronavigation as compared with 35.5% in those who underwent surgery without neuronavigation (risk ratio [RR], 1.57; P=0.056). The incidence of postoperative neurologic deficits (transient and permanent) decreased by 79% with the use of neuronavigation, (12% vs. 33.3%; RR, 0.21; P=0.0003). Neuronavigation improved survival in patients with grade IV gliomas (15 months vs. 13.8 months), but it was not statistically significant (odds ratio (OR), 0.19; P=0.13). CONCLUSIONS: Neuronavigation improved the effectiveness (greater gross total resection of tumors) and safety (fewer neurological deficits) of brain glioma surgery. However, neuronavigation does not significantly influence the survival of patients with grade IV gliomas.

Transorbital approach to the cavernous sinus: an anatomical study of the related cranial nerves.

Background: The cavernous sinus (CS) is a demanding surgical territory, given its deep location and the involvement of multiple neurovascular structures. Subjected to recurrent discussion on the optimal surgical access, the endoscopic transorbital approach has been recently proposed as a feasible route for selected lesions in the lateral CS. Still, for this technique to safely evolve and consolidate, a comprehensive anatomical description of involved cranial nerves, dural ligaments, and arterial relations is needed. Objective: Detailed anatomical description of the CS, the course of III, IV, VI, and V cranial nerves, and C3-C7 segments of the carotid artery, all described from the ventrolateral endoscopic transorbital perspective. Methods: Five embalmed human cadaveric heads (10 sides) were dissected. An endoscopic transorbital approach with lateral orbital rim removal, anterior clinoidectomy, and petrosectomy was performed. The course of the upper cranial nerves was followed from their apparent origin in the brainstem, through the middle fossa or cavernous sinus, and up to their entrance to the orbit. Neuronavigation was used to follow the course of the nerves and to measure their length of surgical exposure. Results: The transorbital approach allowed us to visualize the lateral wall of the CS, with cranial nerves III, IV, V1-3, and VI. Anterior clinoidectomy and opening of the frontal dura and the oculomotor triangle revealed the complete course of the III nerve, an average of 37 (±2) mm in length. Opening the trigeminal pore and cutting the tentorium permitted to follow the IV nerve from its course around the cerebral peduncle up to the orbit, an average of 54 (±4) mm. Opening the infratrochlear triangle revealed the VI nerve intracavernously and under Gruber's ligament, and the extended petrosectomy allowed us to see its cisternal portion (27 ± 6 mm). The trigeminal root was completely visible and so were its three branches (46 ± 2, 34 ± 3, and 31 ± 1 mm, respectively). Conclusion: Comprehensive anatomic knowledge and extensive surgical expertise are required when addressing the CS. The transorbital corridor exposes most of the cisternal and the complete cavernous course of involved cranial nerves. This anatomical article helps understanding relations of neural, vascular, and dural structures involved in the CS approach, essential to culminating the learning process of transorbital surgery.

Endoscopic transorbital approach bone pillars: a comprehensive stepwise anatomical appraisal.

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.

Neurophysiologic Monitoring of Oculomotor Nerves During Transorbital Surgery: Proof of Concept and Anatomic Demonstration.

BACKGROUND AND OBJECTIVES: Transorbital neuroendoscopic surgery (TONES) is continuously evolving and gaining terrain in approaching different skull base pathologies. The objective of this study was to present our methodology for introducing recording electrodes, which includes a new transconjunctival pathway, to monitor the extraocular muscle function during TONES. METHODS: A translational observational study was performed from an anatomic demonstration focused on the transconjunctival electrode placement technique to a descriptive analysis in our series of 6 patients operated using TONES in association with intraoperative neurophysiologic monitoring of the oculomotor nerves from 2017 to 2023. The stepwise anatomic demonstration for the electrode placement and correct positioning in the target muscle was realized through cadaveric dissection. The descriptive analysis evaluated viability (obtention of the electromyography in each cranial nerve [CN] monitored), security (complications), and compatibility (interference with TONES). RESULTS: In our series of 6 patients, 16 CNs were correctly monitored: 6 (100%) CNs III, 5 (83.3%) CNs VI, and 5 (83.3%) CNs IV. Spontaneous electromyography was registered correctly, and compound muscle action potential using triggered electromyography was obtained for anatomic confirmation of structures (1 CN III and VI). No complications nor interference with the surgical procedure were detected. CONCLUSION: The methodology for introducing the recording electrodes was viable, secure, and compatible with TONES.

Optimizing the Endoscopic Transorbital Approach: MacCarty Keyhole for Enhanced Surgical Exposure in the Opticocarotid Region.

BACKGROUND: In recent years, the endoscopic transorbital (TO) approach has gained increasing interest for the treatment of middle cranial fossa lesions. We propose a technical refinement to the conventional superior eyelid TO approach, which improves the surgical exposure and augments the working angles when targeting the opticocarotid region. METHODS: Four embalmed adult cadaveric specimens (8 sides) were dissected at the Laboratory of Surgical Neuroanatomy of our institution. A TO approach was performed, with removal of the anterior clinoid process and the lateral orbital rim. Subsequently, the MacCarty keyhole was drilled in the superolateral orbital wall. Given that the lesser sphenoid wing was already drilled in the conventional TO craniectomy, the opening of the keyhole was essentially a lateral extension of the craniectomy. RESULTS: The procedure was successfully conducted in all 4 orbits. Clinoidectomy was performed either before or after extending the craniectomy to the MacCarty point. Extending the craniectomy made anterior clinoidectomy easier, by increasing the surgical exposure, and allowing a more lateral entrance for the endoscope. The extension also facilitated frontal lobe retraction, and it facilitated the optic nerve and carotid artery manipulation. Postoperative computed tomography scans showed a minimal 10-mm craniectomy extension, which remained covered by the temporal muscle after reconstruction. CONCLUSIONS: The modified endoscopic TO approach with the extension of the craniectomy to MacCarty point improves surgical access and visualization of the opticocarotid region. This facilitates anterior clinoidectomy and optic nerve decompression. Although it implies judicious instrument manipulation and a larger incision size, further studies can define its potential benefits.