Endoscopic identification of the pharyngeal (palatovaginal) canal: an overlooked area

Abstract

Objective The pharyngeal or palatovaginal canal (PC) is a small tunnel that lies between the sphenoid process of the palatine bone and the vaginal process of the sphenoid bone. Currently, little endoscopic information is available about this region. Design and Setting Endoscopic endonasal cadaveric study. Subjects and Methods Twenty sides in 10 adult cadaver heads were studied endoscopically. The sphenopalatine foramen (SPF) and the adjacent pterygopalatine fossa were exposed. Dissection medial to the vidian canal demonstrated a tunnel that runs posteromedially in the sphenoid floor. Endoscopic data were documented. Additionally, canal measurements were obtained on 20 sides from coronal CT scans of paranasal sinuses. Results The PC was identifiable in 85% of the sides, although thickness of its bony wall was variable. The endoscopic relationship of the canal and its artery with other landmarks is described. Radiologically, the diameter of the PC averaged 1.7 mm, and the mean distance from the PC to the vidian canal was 3.78 mm. Conclusion The current study provides a novel endoscopic identification of an overlooked canal. The pharyngeal artery can be a source of bleeding during extended endoscopic procedures. The PC itself could be a place for finger-like projections of anatomically related neoplasms.

Keywords: endoscopic sinus surgery; epistaxis; palatovaginal canal; pharyngeal artery; pharyngeal canal; pterygopalatine fossa; sphenopalatine foramen; vidian canal.

Figure 1

Endoscopic exposure of the sphenopalatine foramen and the sphenopalatine artery (SPA) (left side): (a) An incision is performed just behind the posterior fontanelle (PF), in front of the tail of the middle turbinate (MT). NS, nasal septum; PC, posterior choana. (b) Exposure of the vertical plate of the palatine bone (VPP) and its orbital process (OP) that forms the anterior boundary of the sphenopalatine foramen. The basal lamella (BL) is detached form the ethmoid crest (EC), which is used as a landmark to identify the SPA; the latter being posterolateral to the crest. (c) Endoscopic exposure of the septal (s) and the posterolateral nasal (n) branches of the SPA.

Figure 2

Endoscopic exposure of the pharyngeal canal (PC) (left side): The orbital process of the palatine bone and the adjoining part of the posterior maxillary wall have been removed. The sphenopalatine foramen is thus opened and the sphenopalatine artery (SPA) is retracted laterally. C, clivus; FLS, floor of the sphenoid sinus; pcICA, paraclival ICA; SF, sellar floor. (a) The thin sphenoid process (SP) of the vertical plate of the palatine bone (VPP) is easily fractured using a Cottle elevator. This process forms the inferomedial wall of the PC that transmits the pharyngeal artery and nerve. (b) The thick SP is drilled to expose the pharyngeal artery (as shown in Fig. 3a).

Figure 3

Endoscopic exposure of the pharyngeal artery (PA) (left side): C, clivus; pcICA, paraclival ICA; PPF: pterygopalatine fossa; SF, sellar floor. (a) The thick sphenoid process of the vertical plate of the palatine bone (VPP) has been drilled to expose the pharyngeal artery (PA) running posterosuperiorly in the floor of the sphenoid sinus. (b) The PA is divided and the contents of the PPF are retracted (r) laterally to expose the vidian canal (VC) just medial to the pharyngeal canal. (c) The pharyngeal groove (PG) is shown after removal of the contents the pharyngeal canal. The groove lies in the vaginal process of the sphenoid floor. BPP, base of pterygoid process.

Figure 4

Endoscopic exposure of the posterior wall of the pterygopalatine fossa and related regions: (a) Three openings are identified in the posterior wall of the pterygopalatine fossa. Form medial to lateral, these are (1) the pharyngeal canal (PC) running from the posteromedial angle of the pterygopalatine fossa into the floor of the sphenoid sinus, (2) the vidian canal (VC) running posteriorly in the lateral part of the sphenoid floor and pointing at the anterolateral aspect (FR) of the supralacerum (second) genu of the ICA, and (3) the foramen rotundum more superiorly and laterally transmitting the maxillary nerve (V2) from its cavernous portion in the lateral wall of the sphenoid sinus (V2s) to its pterygopalatine portion (V2p). The posteromedial end of the superior orbital fissure (SOF) lies above the FR. ICA, internal carotid artery; OT, optic tract; PPG, pterygopalatine ganglion; pwMS, posterior wall of the maxillary sinus; SP, sphenoid process of the palatine bone; SPA: sphenopalatine artery. (b) The SPA and the PPG have been retracted (r) inferolaterally to additionally expose the base of the pterygoid process (BPP) that forms the posterior wall of the pterygopalatine fossa. IMA, internal maxillary artery in the infratemporal fossa.

Figure 5

Coronal computed tomography (CT) scan at the level of the posterior wall of pterygopalatine fossa (PPF): three openings are identified in the posterior wall of the PPT. Form medial to lateral, these are (1) the pharyngeal canal (PC) running into the floor of the sphenoid sinus, (2) the vidian canal (VC) running posteriorly in the lateral part of the sphenoid floor, and (3) the foramen rotundum (FR) more superiorly and laterally.