Refining the anatomic boundaries of the endoscopic endonasal transpterygoid approach: the “VELPPHA area” concept

Abstract

T he endoscopic endonasal transpterygoid approach is a lateral extension of the midline endonasal route; although it was initially described to access only the lateral recess of the sphenoid sinus, currently this route is used to reach the most lateral aspect of the skull base. In this surgical scenario, injury to the internal carotid artery (ICA) is one of the most feared complications.The vidian nerve (VN) has been clearly described as a critical landmark for the safe identification of the petrous ICA in the foramen lacerum (FL) during the endoscopic ABBREVIATIONS ET = eustachian tube; FL = foramen lacerum; ICA = internal carotid artery; VC = vidian canal; VELPPHA = vidian nerve, eustachian tube, foramen lacerum, petroclival fissure, and pharyngobasilar fascia; VN = vidian nerve. OBJECTIVEThe endoscopic endonasal transpterygoid route has been widely evaluated in cadavers, and it is currently used during surgery for specific diseases involving the lateral skull base. Identification of the petrous segment of the internal carotid artery (ICA) is a key step during this approach, and the vidian nerve (VN) has been described as a principal landmark for safe endonasal localization of the petrous ICA at the level of the foramen lacerum. However, the relationship of the VN to the ICA at this level is complex as well as variable and has not been described in the pertinent literature. Accordingly, the authors undertook this purely anatomical study to detail and quantify the peri-lacerum anatomy as seen via an endoscopic endonasal transpterygoid pathway. METHODS Eight human anatomical specimens (16 sides) were dissected endonasally under direct endoscopic visualization. Anatomical landmarks of the VN and the posterior end of the vidian canal (VC) during the endoscopic endonasal transpterygoid approach were described, quantitative anatomical data were compiled, and a schematic classification of the most relevant structures encountered was proposed. RESULTS The endoscopic endonasal transpterygoid approach was used to describe the different anatomical structures surrounding the anterior genu of the petrous ICA. Five key anatomical structures were identified and described: the VN, the eustachian tube, the foramen lacerum, the petroclival fissure, and the pharyngobasilar fascia. These structures were specifically quantified and summarized in a schematic acronym-VELPPHA-to describe the area. The VELPPHA area is a dense fibrocartilaginous space around the inferior compartment of the foramen lacerum that can be reached by following the VC posteriorly; this area represents the posterior limits of the transpterygoid approach and, of utmost importance, no neurovascular structures were observed through the VELPPHA area in this study, indicating that it should be a safe zone for surgery in the posterior end of the endoscopic endonasal transpterygoid approach. CONCLUSIONS The VELPPHA area represents the posterior limits of the endoscopic endonasal transpterygoid approach. Early identification of this area can enhance the safety of the e...

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

“…18 In this study, as well as in others, the vidian nerve was found to run over the superior aspect of the horizontal petrous ICA in all specimens (16 sides). 19 20 Therefore, sharp resection of the fibrocartilaginous tissue below the surface of the vidian nerve carries the risk of damaging the anterior genu of the petrous ICA. The pterygosphenoidal fissure proposed by Wang et al 7 seems to be a useful landmark as well.…”

Combined and simultaneous endoscopic endonasal and transorbital surgery for a Meckel’s cave schwannoma: technical nuances of a mini-invasive, multiportal approach

“…For the endoscopic endonasal route, a transpterygoid approach to the medial wall of the cavernous sinus was accomplished, according to the technique already presented in the literature. [28][29][30] Briefly, a left middle turbinectomy and ethmoidectomy were completed, followed by a wide sphenoidotomy. The medial portion of the posterior wall of the maxillary sinus was therefore resected to expose the posterior wall of the maxillary antrum and the vertical process of the palatine bone that was drilled out, together with exposure of the medial pterygoid process.…”

Surgical Anatomy of the Temporal Bone

“…The horizontal segment of the petrous ICA turns upward at the medial border of the petrous apex to form the anterior genu of the ICA, and then it continues as the lacerum segment, second vertical segment of the ICA. So, the VC-ET junction is a safe and critical landmark for efficient localization of the lacerum segment of the ICA, as part of the transpterygoid extension of EEA [24].…”