Meckel's cave access: anatomic study comparing the endoscopic transantral and endonasal approaches.

Recent advances in endonasal endoscopy have facilitated the surgical access to the lateral skull base including areas such as Meckel's cave. This approach has been well documented, however, few studies have outlined transantral specific access to Meckel's. A transantral approach provides a direct pathway to this region obviating the need for extensive endonasal and transsphenoidal resection. Our aim in this study is to compare the anatomical perspectives obtained in endonasal and transantral approaches. We prepared 14 cadaveric specimens with intravascular injections of colored latex. Eight cadavers underwent endoscopic endonasal transpterygoid approaches to Meckel's cave. Six additional specimens underwent an endoscopic transantral approach to the same region. Photographic evidence was obtained for review. 30 CT scans were analyzed to measure comparative distances to Meckel's cave for both approaches. The endoscopic approaches provided a direct access to the anterior and inferior portions of Meckel's cave. However, the transantral approach required shorter instrumentation, and did not require clearing of the endonasal corridor. This approach gave an anterior view of Meckel's cave making posterior dissection more difficult. A transantral approach to Meckel's cave provides access similar to the endonasal approach with minimal invasiveness. Some of the morbidity associated with extensive endonasal resection could possibly be avoided. Better understanding of the complex skull base anatomy, from different perspectives, helps to improve current endoscopic skull base surgery and to develop new alternatives, consequently, leading to improvements in safety and efficacy.

Anatomic analysis specific for the endoscopic approach to the inferior, medial and lateral orbit.

INTRODUCTION: The endoscopic approaches to the medial and inferior orbital walls have continued to grow in popularity. The ability to provide a safe approach to the orbit through this technique has been described in a handful of studies. Even though metric analyses have been conducted on orbital anatomy, few have outlined the anatomical relations pertinent to endoscopic surgery. The goal is to provide improved understanding of the complex anatomy encountered through anatomical dissections and metric analysis of the orbit. This information could assist in approach selection during preoperative planning. METHODS: Anatomical dissections via transantral and endonasal approaches were used to define the limits with current endoscopic sinus surgery instrumentation. The surface area was then calculated of the floor and medial wall to assess access created by the approaches. The path of the infraorbital canal was conducted to assess its placement within the orbital floor. RESULTS: The transantral and endonasal approaches to the orbit provided an adequate surgical window inferiorly and medially. This was confirmed by the surface area calculations. Access laterally was also possible, however, it became limited as dissection advanced superior to the lateral rectus muscle. The infraorbital canal was located consistently at midline on the orbital floor. CONCLUSION: Endoscopic access to the medial and inferior parts of the orbit is feasible and creates adequate access with current instrumentation. Knowing the surgical boundaries and the amount of exposure created can assist the surgeon in deciding a minimally invasive approach.

Anatomical and computed tomographic analysis of the transcochlear and endoscopic transclival approaches to the petroclival region.

OBJECTIVES/HYPOTHESIS: Advances in the field of skull base surgery aim to maximize anatomical exposure while minimizing patient morbidity. The petroclival region of the skull base presents numerous challenges for surgical access due to the complex anatomy. The transcochlear approach to the region provides adequate access; however, the resection involved sacrifices hearing and results in at least a grade 3 facial palsy. An endoscopic endonasal approach could potentially avoid negative patient outcomes while providing a desirable surgical window in a select patient population. STUDY DESIGN: Cadaveric study. METHODS: Endoscopic access to the petroclival region was achieved through an endonasal approach. For comparison, a transcochlear approach to the clivus was performed. Different facets of the dissections, such as bone removal volume and exposed surface area, were computed using computed tomography analysis. RESULTS: The endoscopic endonasal approach provided a sufficient corridor to the petroclival region with significantly less bone removal and nearly equivalent exposure of the surgical target, thus facilitating the identification of the relevant anatomy. The lateral approach allowed for better exposure from a posterolateral direction until the inferior petrosal sinus; however, the endonasal approach avoided labyrinthine/cochlear destruction and facial nerve manipulation while providing an anteromedial viewpoint. The endonasal approach also avoided external incisions and cosmetic deficits. The endonasal approach required significant sinonasal resection. CONCLUSIONS: Endoscopic access to the petroclival region is a feasible approach. It potentially avoids hearing loss, facial nerve manipulation, and cosmetic damage.

Endoscopic repair of an injured internal carotid artery utilizing femoral endovascular closure devices.

OBJECTIVES/HYPOTHESIS: Injury to the internal carotid artery is a feared complication of endoscopic endonasal surgery of the skull base. Such an event, although rare, is associated with high morbidity and mortality. Even if bleeding is controlled, permanent neurological defects frequently persist. Many techniques have been developed to manage internal carotid artery rupture with varying degrees of success. The purpose of this study was to explore endoscopic management of arterial damage with endovascular closure devices used for a femoral arteriotomy. The ability to remotely suture a damaged artery permits the possible adaptation of this technology in managing endoscopic arterial complications. STUDY DESIGN: Technical note. METHODS: After the creation of an endoscopic endonasal corridor in a cadaveric specimen, an arteriotomy was created at the cavernous portion of the internal carotid artery. The Angio-Seal, StarClose, and MynxGrip vascular closure devices were utilized under endoscopic guidance to repair the arteriotomy. Angiography was then done on a cadaver sutured with the StarClose. RESULTS: Both the Angio-Seal and StarClose were deployed quickly and appeared to provide sufficient closure of the arteriotomy. The Angio-Seal required the use of a guidewire and was longer to deploy when compared with the StarClose. The StarClose deployment was quick and facile. The MynxGrip also deployed without difficulty. CONCLUSIONS: The Angio-Seal and StarClose systems were both successfully deployed utilizing an endoscopic endonasal approach. The MynxGrip was the easiest to deploy and has the greatest potential to be of benefit in this application. Further studies with hemodynamic models are required to properly assess the appropriateness in this setting. LEVEL OF EVIDENCE: NA.

Landmarks for endoscopic approach to the parapharyngeal internal carotid artery: a radiographic and cadaveric study.

OBJECTIVES/HYPOTHESIS: To define transnasal endoscopic surgical landmarks for the parapharyngeal segment of the internal carotid artery (ppICA) using radiographic analysis and cadaveric dissection. STUDY DESIGN: Cadaveric and radiographic study. METHODS: One hundred seventy-nine computed tomography angiography studies of the head and neck were analyzed using Osirix third-party software (Pixmeo, Geneva, Switzerland). Dissection of a cadaveric specimen was used as a correlate to radiographic findings. The posterior aspect of the lateral pterygoid process and posterior border of the mandibular ramus were used as bony landmarks for the ppICA. RESULTS: At the level of the nasal floor, the distance from the ppICA to the posterolateral pterygoid process and to the posterior mandibular ramus was 2.36 cm and 1.94 cm, respectively, in males, and 2.37 cm and 1.99 cm, respectively, in females. At the level of the skull base, the distance from the ppICA to the posterolateral pterygoid process and to the posterior mandible was 2.33 cm and 1.49 cm, respectively, in males, and 2.20 cm and 1.57 cm, respectively, in females. Cadaver dissection demonstrated the utility of identifying these landmarks. CONCLUSIONS: The posterior border of the mandibular ramus and the posterolateral aspect of the pterygoid process may serve as consistent bony landmarks for identification of the ppICA.

Minimally invasive access to the posterior cranial fossa: an anatomical study comparing a retrosigmoidal endoscopic approach to a microscopic approach.

OBJECTIVES: The central location and complex neurovascular structures of the posterior cranial fossa make tumor resection in this region challenging. The traditional surgical approach is a suboccipital craniotomy using a microscope for visualization. This approach necessitates a large surgical window and cerebellar retraction, which can result in patient morbidity. With the advances in endoscopic technology, minimally invasive access to the cerebellopontine angle can be achieved with minimal manipulation of uninvolved structures, reducing the complications associated with the suboccipital approach. METHODS: An endoscopic and microscopic approach was completed on anatomic specimens. To access the central structures of the posterior cranial fossa, a retrosigmoidal approach was undertaken. A keyhole craniotomy was made in the occipital bone posterior to the junction of the transverse and sigmoid sinuses. The endoscope was advanced and photographs were obtained for review. The exposure was compared with that obtained with a microscope. RESULTS: The endoscopic retrosigmoidal approach to the posterior cranial fossa provided increased exposure to the midline structures while minimizing the surgical window. The relevant anatomy was identified without difficulty. CONCLUSION: An endoscopic retrosigmoidal approach to the midline structures of the posterior cranial fossa is anatomically feasible. The morbidity associated with retraction of the cerebellum could possibly be avoided, improving patient outcomes. Retrosigmoidal endoscopy provides access to anatomical structures that is not possible using a microscope in a suboccipital approach. Further understanding of the endoscopic anatomy of the posterior fossa can allow for advances in cranial base surgery with improved safety and efficacy.

Access to the parapharyngeal space: an anatomical study comparing the endoscopic and open approaches.

OBJECTIVES/HYPOTHESIS: A subtemporal preauricular approach to the infratemporal fossa and parapharyngeal space has been the traditional path to tumors of this region. The morbidity associated with this procedure has lead to the pursuit of less invasive techniques. Endoscopic access using a minimally invasive transmaxillary/transpterygoid approach potentially may obviate the drawbacks associated with open surgery. The anatomy of the parapharyngeal space is complex and critical; therefore, a comparison of the anatomy exposed by these different approaches could aid in the decision making toward a minimally invasive surgical corridor. STUDY DESIGN: Technical Note. METHODS: The parapharyngeal space was accessed endonasally by removal of the medial and posterior walls of the maxillary sinus. To allow better visualization and increased triangulation of a bimanual dissection technique, a sublabial canine fossa antrostomy was created. The medial and lateral pterygoid plates were removed. Further lateral dissection exposed the relevant anatomy of the parapharyngeal space. A subtemporal preauricular infratemporal approach was also completed. RESULTS: The endoscopic approach provided sufficient access to the superior portion of the parapharyngeal space. The open approach also provided adequate access; however, it required a larger surgical window, causing greater injury. A significant advantage of the subtemporal approach is the improved access to the petrous portion of the internal carotid artery. Conversely, the endonasal approach provided improved access to the anterior and medial portions of the superior parapharyngeal space. CONCLUSION: Endoscopic endonasal access utilizing a transmaxillary/transpterygoid approach provides a sufficient surgical window for tumor extirpation. Utilization of this approach obviates some of the morbidity associated with an open procedure. LEVEL OF EVIDENCE: 5.

What is the Best Route to the Meckel Cave? Anatomical Comparison between the Endoscopic Endonasal Approach and a Lateral Approach.

Background Traditionally, a pterional approach is utilized to access the Meckel cave. Depending on the tumor location, extradural dissection of the Gasserian ganglion can be performed. An endoscopic endonasal access could potentially avoid a craniotomy in these cases. Methods We performed an endoscopic endonasal approach as well as a lateral approach to the Meckel cave on six anatomic specimens. To access the Meckel cave endoscopically, a complete sphenoethmoidectomy and maxillary antrostomy followed by a transpterygoid approach was performed. For lateral access, a pterional craniotomy with extradural dissection was performed. Results The endoscopic endonasal approach allowed adequate access to the Gasserian ganglion. All the relevant anatomy was identified without difficulty. Both approaches allowed for a similar exposure, but the endonasal approach avoided brain retraction and improved anteromedial exposure of the Gasserian ganglion. The lateral approach provided improved access posterolaterally and to the superior portion. Conclusion The endoscopic endonasal approach to the Meckel cave is anatomically feasible. The morbidity associated with brain retraction from the open approaches can be avoided. Further understanding of the endoscopic anatomy within this region can facilitate continued advancement in endoscopic endonasal surgery and improvement in the safety and efficacy of these procedures.