Endoscopic endonasal approach to the vidian nerve and its relation to the surrounding structures: an anatomic cadaver study

Radiologic evaluation of the Vidian canal in the pediatric population

PURPOSE

This examination aimed to display the size and topographic position of the Vidian canal (VC) in normal children.

METHODS

180 pediatric subjects aged 1-18 years were included this computed tomography examination. The distances of VC to certain landmarks, and VC length were measured. The locations of VC according to the sphenoid sinus, and the medial plate of pterygoid process were classified as three types, separately.

RESULTS

The distances of VC to the vomerine crest, midsagittal plane, round foramen, and the superior wall of sphenoid sinus were measured as 12.68 ± 3.17 mm, 10.76 ± 2.52 mm, 8.62 ± 2.35 mm, and 14.16 ± 5.00 mm, respectively. The length and angle of VC were measured as 12.00 ± 2.52 mm, and 16.60 ± 9.76°, respectively. According to the sphenoid bone, VC location was identified as Type 1 in 113 sides (47.5%), as Type 2 in 70 sides (29.4%), and as Type 3 in 55 sides (23.1%). According to the medial plate of pterygoid process, VC location was identified as Type A in 274 sides (76.1%), as Type B in 55 sides (15.3%), and as Type C in 31 sides (8.6%). VC location types correlated with pediatric ages, but not sex or side.

CONCLUSION

With advancing pediatric age, the protrusion of VC into the sphenoid sinus increases, and VC shifts from medial to lateral side of the medial plate of pterygoid process.

Anatomical localization of horizontal segment of the petrous internal carotid artery in transnasal endoscopic skull base surgery

OBJECTIVE

To discuss the localization of horizontal segment of petrous internal carotid artery in transnasal endoscopic skull base surgery, and to provide anatomical data for clinical surgery.

METHODS

The horizontal segment of the petrous internal carotid artery of 5 adult cadaveric heads were exposed by endoscopic transnasal and microscopic open approaches respectively, and the relevant data and images were measured and collected.

RESULTS

The medial wall of the foramen spinosum is the lateral wall of the isthmus of the eustachian tube, and the thickness of the bone is 0.5 ± 0.2 mm. The medial wall of the isthmus of the eustachian tube is the lateral wall of the posterior genu of the carotid canal and the thickness of the bone is 0.2 ± 0.1 mm. The vidian nerve originates from the anterior genu of the petrous internal carotid artery. The distance from the base of vidian nerve to the isthmus of eustachian tube is 19.2 ± 2.8 mm.

CONCLUSION

The foramen spinosum is the landmark of isthmus of the Eustachian tube. The isthmus of the Eustachian tube is the landmark of the posterior genu of the internal carotid artery. The line between the base of the vidian nerve and the isthmus of the Eustachian tube ioks the landmark of horizontal segment of the petrous internal carotid artery.

The Pterygosphenoidal Triangle: Surgical Anatomy and Case Series in Endoscopic Endonasal Skull Base Surgery

BACKGROUND

Safe exposure of the lacerum segment of the carotid artery remains a challenge in endoscopic endonasal surgery.

OBJECTIVE

To introduce the pterygosphenoidal triangle as a novel and reliable landmark for facilitating access to the foramen lacerum.

METHODS

Fifteen colored silicone-injected anatomic specimens were dissected using an endoscopic endonasal approach to the foramen lacerum region in a stepwise manner. Twelve dried skulls were studied and 30 high-resolution computed tomography scans were analyzed to measure the borders and angles of the pterygosphenoidal triangle. Surgical cases incorporating the foramen lacerum exposure between July 2018 and December 2021 were reviewed to provide surgical outcomes of the proposed surgical technique.

RESULTS

The pterygosphenoidal triangle is delineated by the pterygosphenoidal fissure medially and the vidian nerve laterally. The palatovaginal artery is located at the base of the triangle anteriorly, while the apex is formed by the pterygoid tubercle posteriorly, which leads to the anterior wall of the foramen lacerum and lacerum internal carotid artery. In the reviewed surgical cases, 39 patients underwent 46 foramen lacerum approaches for resection of pituitary adenoma (12 patients), meningioma (6 patients), chondrosarcoma (5 patients), chordoma (5 patients), or other lesions (11 patients). There were no carotid injuries or ischemic events. Near-total resection was achieved in 33 (85%) of 39 patients (gross-total in 20 [51%]).

CONCLUSION

This study details the pterygosphenoidal triangle as a novel and practical anatomic surgical landmark for safe and effective exposure of the foramen lacerum in endoscopic endonasal surgery.

Advances in Pituitary Surgery

Pituitary surgery has advanced considerably in recent years with the exploration and development of various endoscopic approaches and techniques. Different endoscopic skull base approaches are being applied to access sellar tumors in different locations. Moreover, extracapsular dissection and cavernous sinus exploration have enabled gross total resection of sellar tumors where it could not have been achieved in the past. Techniques for skull base reconstruction have also progressed, allowing surgeons to remove larger and more complicated tumors than before. This review article discusses different endoscopic skull base approaches, surgical techniques for removing pituitary adenomas, and reconstruction methods for repairing postoperative low-flow and high-flow cerebrospinal fluid leakage.

Anatomical Variants of Post-ganglionic Fibers within the Pterygopalatine Fossa: Implications for Endonasal Skull Base Surgery

Objectives The vidian nerve provides parasympathetic innervation to the nasal cavity and the lacrimal gland. Previous anatomic studies have primarily focused on preservation or severance of the vidian nerve proximal to the pterygopalatine ganglion (PPG). This study aimed to assess its neural fibers within the pterygopalatine fossa after synapsing at the PPG, and to explore potential clinical implications for endoscopic endonasal skull base surgery.

Methods An endonasal transpterygoid approach was performed on eight cadaveric specimens (16 sides). The PPG and maxillary nerve within the pterygopalatine fossa were divided. The vidian nerve was traced retrograde into the foramen lacerum, and postganglionic fibers distal to the PPG were dissected following the zygomatic nerve into the orbit. Potential communicating branches between the ophthalmic nerve (V1) and the PPG were also explored.

Results All sides showed a plexus of neural communications between the PPG and the maxillary nerve. The zygomatic nerve exits the maxillary nerve close to the foramen rotundum, piercing the orbitalis muscle to enter the orbit in all sides. The zygomatic nerve was identified running beneath the inferior rectus muscle toward a lateral direction. In 7/16 sides (43.75%), a connecting branch between V1 and the pterygopalatine ganglion was observed.

Conclusion Neural communications between the PPG and the maxillary nerve were present in all specimens. A neural branch from V1 to the PPG potentially contributes additional postganglionic parasympathetic function to the lacrimal gland.

Comparative Analysis of Surgical Exposure among Endoscopic Endonasal Approaches to Petrosectomy: An Experimental Study in Cadavers

Objectives  Endoscopic endonasal approaches (EEAs) for petrosectomies are evolving to reduce perioperative brain injuries and complications. Surgical terminology, techniques, landmarks, advantages, and limitations of these approaches remain ill defined. We quantitatively analyzed the anatomical relationships and differences between EEA exposures for medial, inferior, and inferomedial petrosectomies. Design  This study presents anatomical dissection and quantitative analysis. Setting  Cadaveric heads were used for dissection. EEAs were performed using the medial petrosectomy (MP), the inferior petrosectomy (IP), and the inferomedial petrosectomy (IMP) techniques. Participants  Six cadaver heads (12 sides, total) were dissected; each technique was performed on four sides. Main Outcomes and Measures  Outcomes included the area of exposure, visible distances, angles of attack, and bone resection volume. Results  The IMP technique provided a greater area of exposure ( p  < 0.01) and bone resection volume ( p  < 0.01) when compared with the MP and IP techniques. The IMP technique had a longer working length of the abducens nerve (cranial nerve [CN] VI) than the MP technique ( p  < 0.01). The IMP technique demonstrated higher angles of attack to specific neurovascular structures when compared with the MP (midpons [ p  = 0.04], anterior inferior cerebellar artery [ p  < 0.01], proximal part of the cisternal CN VI segment [ p  = 0.02]) and IP (flocculus [ p  = 0.02] and the proximal [ p  = 0.02] and distal parts [ p  = 0.02] of the CN VII/VIII complex) techniques. Conclusion  Each of these approaches offers varying degrees of access to the petroclival region, and the surgical approach should be appropriately tailored to the pathology. Overall, the IMP technique provides greater EEA surgical exposure to vital neurovascular structures than the MP and the IP techniques.

The endoscopic prelacrimal recess approach to the paramedian middle cranial base: An anatomical study

BACKGROUND

Endoscopic endonasal approach to paramedian cranial base implies sacrifice of the nasal structures.

OBJECTIVE

The present study aimed to illustrate the anatomy and provide critical anatomical landmarks for the endoscopic prelacrimal recess approach (PLRA) to the paramedian middle cranial base.

METHODS

Anatomical dissections were performed in 10 cadaveric specimens.

RESULTS

Successful access to the paramedian middle cranial base was achieved in all dissections via the PLRA with the removal of the pterygoid process. For the dissection of the infratemporal fossa and pterygopalatine fossa, the buccal nerve and infraorbital neurovascular bundle can serve as important anatomic landmarks to identify the detailed structures. In the upper parapharyngeal space, the stylopharyngeal aponeurosis can present as anatomical barriers to protect the parapharyngeal segment of the internal carotid artery (PPICA); while the levator veli palatini muscle can be considered as a landmark to locate the PPICA. For the dissection of the Eustachian tube (ET), the isthmus of the ET and ET sulcus can serve as useful landmarks to identify the posterior genu of the ICA and horizontal segment of the petrous ICA respectively.

CONCLUSION

The PLRA to the paramedian middle cranial base is anatomically feasible and can facilitate preservation of the integrity of nasal structures. The buccal nerve, infraorbital neurovascular bundle, levator veli palatini muscle, stylopharyngeal aponeurosis, the isthmus of the ET, and ET sulcus can serve as critical anatomic landmarks in their respective region and may facilitate the application of this approach.

Endonasal endoscopic approach to the pterygopalatine and infratemporal fossae

The pterygopalatine fossa and infratemporal fossa are spaces located under the skull base, housing important neurovascular structures. Surgical access to these spaces is challenging because of their deep location and complex anatomy. Their surgical access has been classically carried out through multiple craniofacial approaches until the advent of endoscopic endonasal surgery at the end of the XX^th century. Our goal is to describe the transmaxillary-transsphenoidal-transpterygoid approach to the pterygopalatine and infratemporal fossae through endonasal endoscopic surgery based on anatomo-surgical dissection and an illustrative clinical case. We conclude that after careful radiologic evaluation of the feasibility of this technique, the endonasal endoscopic access to these spaces for tumor resection is efficient with reduced surgical morbidities. The endonasal approach is versatile and can be fashioned according to the nature and extent of the lesion.

The anatomical and radiological evaluation of the Vidian canal on cone-beam computed tomography images

INTRODUCTION

The aim of this study is to explore the anatomy of the Vidian nerve to elucidate the appropriate surgical approach based on preoperative cone-beam computed tomography (CBCT) images.

MATERIALS AND METHODS

The Vidian canal and its surrounding structures were morphometrically evaluated retrospectively in CBCT images of 400 cases by the Planmeca Romexis program. The types of the Vidian canal were determined and seven parameters were measured from the images.

RESULTS

Three types of the Vidian canal according to the relationship with the sphenoid bone were found as follows: the Vidian canal totally protruded into the sphenoid sinus (19.75%), partially protruded into sphenoid sinus (44.37%) and embedded inside bony tissue of the body of sphenoid bone (35.87%). The position of the Vidian canal was medial (34.62%), on the same line (55.12%) and lateral (10.25%) to the medial plate of the pterygoid process. The distance between the Vidian canal and the vomerine crest, the mid-sagittal plane, the round foramen, the palatovaginal canal, and the superior wall of the sphenoid sinus, the length of the Vidian canal and the angle between the Vidian canal and the sagittal plane was found to be 16.69 ± 2.14, 13.80 ± 2.00, 8.88 ± 1.60, 5.83 ± 1.37, 23.98 ± 2.68, 13.29 ± 1.71 mm and 25.78° ± 3.68° in males, 14.62 ± 1.66, 11.43 ± 1.28, 8.51 ± 1.63, 5.78 ± 0.57, 22.37 ± 2.07, 12.91 ± 1.26 mm and 23.43° ± 3.07° in females, respectively.

CONCLUSIONS

Our results may assist with proper treatment for surgical procedures around the Vidian canal with a high success rate and minimal complications. Therefore, the results obtained in this study contribute to the literature.