The pterygopalatine fossa (PPF) is a small fat-filled space deep within the head on the lateral skull base. It serves as a site of communication between the infratemporal fossa, nasal cavity, nasopharynx, middle cranial fossa and the orbit, creating a pathway for infection and malignant spread. Its complex anatomy often makes diagnosis and treatment of pathologies in this region difficult. Moreso, the vital structures within this region makes comprehension of this region key for safe surgical resections. Here we develop an anatomically accurate 3D model for the PPF and the integral structures contained within. Neurovasculature, musculature, and openings of the PPF were segmented and measured from the Computerized Tomography (CT) angiogram of a healthy 29-year-old woman. Data related to variations, relationships, and dimensions of structures from anatomical studies were also used to deduce accurate relationships and identify known common anatomical variants of structures within the PPF. Finally, a medical illustrator used these data to develop a 3D anatomical model. The PPF is a clinically important area that transmits structures necessary for many functions in the head, including tear production, sensation over the maxilla, and supply of inner facial and nasopharyngeal structures. The final 3D model created in this project may serve to improve education and training for clinical applications. This includes identifying pathways of disease transmission and learning best surgical practices, such as approaches, nerve blocks, endoscopic techniques, and surgical landmark identification.
Introduction
The pterygopalatine fossa (PPF) is a small space deep in the skull base housing important neurovascular structures, including the pterygopalatine ganglion, the maxillary nerve, the vidian nerve and maxillary artery. , Pyramidal in shape, it serves as a site of communication between the oral cavity, nasopharynx, nasal cavity, middle cranial fossa, infratemporal fossa and the orbit. Consequently, it serves as a site by which infection and malignancy spread with ease from one space to the next. Malignant tumors involving this space often have a poor prognosis and frequent disease progression due to the ability for tumors to spread to adjacent spaces of the head and neck, involving critical structures difficult to resect or otherwise treat.
Understanding the complex 3-dimensional (3D) shape and anatomy of this space is key to diagnosis and treatment of diseases within this region. Although 2-dimensional (2D) models aim to teach the anatomy, true mastery requires comprehension of these structures and their spatial relationship in 3-dimensions. 3D models can therefore serve to facilitate clear depictions of anatomy which are often difficult to achieve by traditional 2D atlases. Here, we aim to develop an anatomically accurate, digital 3D model of the PPF, and the integral structures contained within, by combining segmented cross sectional imaging data, published cadaveric anatomical studies, and 3D medical illustration.
Methods
The methods of this manuscript have been previously described by Silver et al. In brief, CT angiography scans from a healthy 29-year-old female were segmented and uploaded to a 3D rendering program, ZBrush (Maxon, Bad Homburg, Germany). Artifacts were removed and objects were subsequently refined using anatomical data from cadaver-based peer-reviewed anatomic literature. Since several structures cannot be seen, and hence segmented) on radiologic imaging structures of the PPF and relevant surgical landmarks were added by the medical illustrator using data from the literature. Where variations existed in structural descriptions, the model represented the most common variant in the peer-reviewed literature that was best supported by specimen count, figure renders and overall quality of anatomical descriptions. The final 3D model was uploaded to an online viewer for interactive viewing (Medreality, Thyng, LLC, IL).
Results
The PPF is an inverted, pyramid-shaped space deep in the skull base, between the infratemporal fossa laterally and the nasopharynx medially. , The space of the PPF lies between several bones of the skull, including the maxilla, sphenoid, and palatine bones. , In this section, we will describe the complex anatomy of the PPF, including the borders and surrounding bony anatomy, communications to other anatomic regions, and the neurovascular contents that lie within the space. While describing this anatomy, we will first build a simplified 3D inverted trapezoidal model and then an anatomic 3D rendering.
To begin building the 3D trapezoidal model, we first define the borders of the space in detail as depicted in Figure 1 and Figure 2 . The anterior border, highlighted in Figure 1 (light grey), of the PPF is formed by the posterior wall of the maxillary sinus, which itself is part of the maxilla. The posterior border (red) is formed by 2 areas of the sphenoid bone—the pterygoid base and the inferior aspect of the greater wing of the sphenoid. The lateral border, highlighted in Figure 2 (green), is composed of the pterygomaxillary fissure, which is an open space between the maxilla anteriorly, and the pterygoid base posteriorly. The medial border (purple) is formed by the perpendicular (vertical) plate of the palatine bone and includes the sphenopalatine foramen. The roof, or superior border (blue), is made up of both the inferior surface of the greater wing of the sphenoid and the orbital process of the palatine bone, and the space between the two, known as the inferior orbital fissure. , The floor, or inferior border (yellow), is formed by the pyramidal process of the palatine bone. ,
As mentioned above, the PPF communicates directly with the nasal cavity, nasopharynx, oral cavity, infratemporal fossa, orbit, and middle cranial fossa via various foramina and fissures. These communications are outlined in Figure 3 .
Posteriorly the PPF communicates with the middle cranial fossa via 2 bony canals: the foramen rotundum laterally and superiorly, and the pterygoid/vidian canal slightly more medially and inferiorly. Along the posterior border lies the palatosphenoidal canal, also known as the palatovaginal canal, which communicates with the nasopharynx. Laterally, the pterygomaxillary fissure, which makes up the “border” of the PPF, is a space that communicates directly with the infratemporal fossa. , On the medial border of the PPF lies the sphenopalatine foramen, which is formed by the notch between the orbital and sphenoidal processes of the palatine bone. , Via this foramen, the PPF communicates directly with the posterior nasal cavity. Superiorly, the inferior orbital fissure serves as a direct connection to the orbit. , Last, of the connections is that inferiorly with the oral cavity via the greater and lesser palatine canal. This canal harbors neurovasculature that arises from PPF structures and descends to supply the palate. The neurovascular contents of the PPF as they traverse the communications highlighted above are described in detail in Figure 4 .
Pterygopalatine ganglion
At the core of the PPF lies the pterygopalatine ganglion (PPG), sometimes known as the sphenopalatine ganglion. The ganglion is the largest of 4 parasympathetic ganglia in the head and serves as an important nerve hub which carries predominantly parasympathetic fibers, along with some sympathetic and sensory fibers, to the nasal, oral, and pharyngeal regions. , The PPG is classically described as a single morphologic structure with an inverted conical shape that is similar in shape to the structure of the fossa it lies within. , According to an anatomical study done by Rusu et al., while 70% of PPGs are a single structure as classically described, 30% of cadavers had a partitioned PPG structure. In general, the ganglion is consistently located in the same plane as the vidian canal, and it receives both preganglionic parasympathetic and postganglionic sympathetic fibers from the vidian nerve within this canal. , The majority of these parasympathetics synapse within the PPG, and the postganglionic fibers exit the ganglion via branches to the maxillary division of the trigeminal nerve (V2), including the communicating ganglionic branches from V2 (otherwise known as pterygopalatine nerves), and the zygomatic nerve. , The sympathetic fibers often pass through the ganglion without synapsing. ,
Lateral communications
Pterygomaxillary fissure
The pterygomaxillary fissure is an inverted triangular opening that forms the lateral border of the PPF and serves as the passageway between the PPF and the infratemporal fossa. The inferior apex of the space is formed by the articulation of 3 bones: the posterior surface of the maxilla, the lateral pterygoid plate of the sphenoid, and the pyramidal process of the palatine bone. This area is otherwise known as the pterygomaxillary junction. Moving superiorly, the remainder of the triangular space is formed by the divergence of the pterygoid and maxilla. Though the fissure dimensions vary in size and shape, , it is noted to be slightly larger in males vs females. Structures traversing the pterygomaxillary fissure include the third part of the maxillary artery and the posterior superior alveolar nerve.
(Internal) maxillary artery
The maxillary artery, traditionally misnamed as the internal maxillary artery, is a branch of the external carotid artery and is commonly divided into 3 segments: the mandibular, pterygoid, and pterygopalatine segments. The 3rd segment of the maxillary artery, the pterygopalatine segment, arises once the artery enters the PPF via the pterygomaxillary fissure and from the infratemporal fossa, where it courses between the 2 heads of the lateral pterygoid muscle. Within the PPF the maxillary artery gives rise to several branches before exiting the PPF as the sphenopalatine artery via the sphenopalatine foramen. The branches of the maxillary artery in this region include: the pharyngeal, greater palatine, vidian, descending palatine, infraorbital and posterior superior alveolar arterial branches. The greater palatine artery gives rise to the lesser palatine branch, the sphenopalatine to the posterior lateral nasal wall and posterior septal arteries, and the infraorbital branches into the anterior superior alveolar artery. The anatomic course, orientation, and exact branching pattern of this segment of the maxillary artery is highly variable. In general, the maxillary artery enters the PMF coursing anteriorly in the medial and superior direction. The posterior superior alveolar artery and infraorbital arteries arise near the posterior wall of the maxilla and exit the PPF via the posterosuperior alveolar foramen and the infraorbital fissure, respectively. The maxillary artery continues medially and then divides into the descending palatine artery, vidian artery and sphenopalatine artery. This branching pattern was found in 87% of specimens (18/21 cadavers) in a cadaveric study by Choi 2003. In the same study, the posterior superior alveolar artery (PSAA) and infraorbital artery (IOA) branches together in 57.1% of specimens and the PSAA before the IOA in 42.9% of specimens. This common branching pattern was also noted in Otake 2011.
Posterior superior alveolar nerve, artery, and vein
After branching from the maxillary artery, the PSAA divides into 2 branches, the gingival branch, providing vascularization to the cheek, and the dental branch, which travels anteriorly and inferiorly before rising upwards towards the orbit to form an intraosseous anastomosis with the infraorbital artery. , The PSAA runs close to the periosteum of the maxillary tuberosity, entering the lateral wall of the maxillary sinus via the posterior superior alveolar foramen. Alongside it courses the posterior superior alveolar vein, draining the upper posterior gums and serving as tributary to the pterygoid venous plexus. The posterior superior alveolar nerve is a branch of the maxillary nerve coursing closely to the artery. It arises prior to the infraorbital canal, traveling with the PSAA where it descends anteriorly and inferiorly into the foramen on the infratemporal surface of the maxillary sinus. , , , Notably, several posterior alveolar nerves can arise from the maxillary nerve; however, most commonly this is limited to 2 branches. , Th remain branch pierces the infratemporal surface of the maxilla above the most inferior point of the maxillary tuberosity supplying the posterior, upper gums, and teeth of the maxilla.
Medial communications
Sphenopalatine foramen
The sphenopalatine foramen (SPF) is a vertically-oriented ovular opening on the medial border of the PPF which connects the PPF directly with the posterior nasal cavity. The foramen is formed inferiorly by a notch between the orbital and sphenoidal processes of the palatine bone, and the articulation of these processes with the sphenoid bone. The crista ethmoidalis, a small crest of the perpendicular plate or ascending process of the palatine bone that meets the middle turbinate, lies just anterior and within 1mm of the opening, and can often serve as a surgical landmark. It is generally located in the superomedial corner of the PPF, at or just superior to the midpoint of a line joining the skull base and the hard palate. Although its exact relation with the middle turbinate is varied, it can generally be found near the attachment of the middle turbinate to the lateral nasal wall posteriorly. Through the sphenopalatine and posterior nasal arteries pass through the SPF, both arise from the maxillary artery. Nerves passing through the SPF include the nasopalatine nerve as it accompanies the SPA, and the posterior nasal nerve, both branches of V2. Notably, the sphenopalatine ganglion, vidian nerve, and maxillary nerve all course superior to the horizontal plane of the SPF.
Sphenopalatine artery, posterior septal artery, and posterior lateral nasal artery
As discussed above, the sphenopalatine artery (SPA) arises from the pterygopalatine segment of the maxillary artery as it reaches the medial aspect of the PPF. The SPA serves as the dominant blood supply to the posterior mucosa of the nasal cavity by giving rise to 2 main branches: the posterior lateral nasal artery and the posterior septal artery (sometimes called the posterior nasal artery). The precise location of branching of the SPA into these tributaries varies. ,
One cadaveric study on 64 specimens and 128 PPFs found that 89% of the maxillary arteries branched into the terminal branches prior to exiting the SPF into the nose. In these specimens, the most common branching pattern was into 2 branches (69%), though some specimens branched into 3 and 4 vessels (19% and 2%, respectively). Another cadaveric study on 50 specimens corroborates that 2 divisions is the most common branching pattern (76% of specimens). However, in a separate study, Bryant et al. found that the maxillary artery entered the SPF as a single artery the majority of the time (77%), and in only 23% of specimens did the artery first give rise to 2 branches prior to exiting the PPF.
The posterior lateral nasal artery exits the SPF and runs inferiorly along the perpendicular plate of the palatine bone and continues along the lateral nasal wall. , The posterior septal artery also exits the PPF via the SPF and runs along the anterior wall of the sphenoid sinus, continuing medial to supply the posterior septum. , One anatomic study showed that the posterior septal artery ran as either a single or dual branch below the sphenoid ostium (43.5% vs 56.5%, resepectively) toward the septum. Sometimes the posterior septal arteries are referred to as “nasoseptal arteries,” in reference to their utilization in a nasoseptal flap reconstruction.
Nasopalatine nerve posterior nasal nerves
Derived from the PPG, the nasopalatine nerve exits the PPF via the SPF. It travels in close association with the posterior septal branches of the SPA, traversing the frontal wall of the sphenoid sinus to then run along the septum. It provides sensory innervation to the septum and part of the anterior hard palate. The posterior nasal nerves are classically thought to enter the nasal cavity via the SPF before giving rise to several branches, including the posterior superior lateral nasal nerve, which is thought to provide a significant portion of the autonomic innervation to the lateral nasal wall. A complex network of accessory posterior nasal nerves enters the nasal cavity via the SPF and other accessory ostia to supply the lateral nasal wall. ,
Posterior communications
The posterior border of the PPF, made up by various parts of the sphenoid bone, communicates with the middle cranial fossa and nasopharynx via 3 separate foramina. Laterally, buried within the sphenoid bone, are the foramen rotundum and the pterygoid (vidian) canal. These foramina are separated by the pterygoid ridge, a bony ridge on the posterior surface of the pterygoid process, with the foramen rotundum located superolateral to the vidian canal. , Across 2 cadaveric studies, the distance between the foramen rotundum and vidian canal was noted to be about 5.1mm in both men and women. ,
Foramen rotundum
The foramen rotundum is a bony opening in the sphenoid bone, which lies in the superolateral corner of the posterior wall of the PPF. , It is described as running anterolaterally at 70° to the coronal plane of the skull base with the inner foramen diameter decreasing as it moves anteroposteriorly, although mild variations can be noted. , The foramen rotundum is separated from the superior orbital fissure by a bony bridge called maxillary strut. This foramen transmits the maxillary division of the trigeminal nerve (V2, or maxillary nerve) from the middle cranial fossa into the PPF.
Maxillary division of CN V (V2)
The maxillary nerve (V2) is a large structure found within the PPF that provides sensory innervation to the mid face including the skin of the midfacial region, the lower eyelid, side of nose and upper lip; the mucous membrane of the nasopharynx, maxillary sinus, soft palate, palatine tonsil, roof of the mouth, and the maxillary gingivae. , It originates at the trigeminal ganglion, between the ophthalmic and mandibular nerves, traveling anteriorly, low in the lateral wall of the cavernous sinus, to the foramen rotundum, which serves as the conduit for the nerve to enter the PPF. , As it courses through the foramen rotundum, it changes shape, from compressed to cylindrical and compact. Here, V2 enters the PPF on the posterolateral aspect and courses through the superior portion of the fossa, giving rise to several branches within the PPF before it exits the inferior orbital fissure superiorly as the infraorbital nerve (ION). , , The maxillary nerve is documented to have up to 15 branches within the PPF; some of those identified in literature include the ganglionic branches, zygomatic, orbital, orbital branches, pharyngeal, posterior palatine, middle palatine, anterior palatine (greater palatine), lateral posterior superior nasal branches, medial posterior superior nasal branches, posterior inferior nasal branches, nasopalatine, and the posterior superior alveolar, however, we will focus on the most commonly documented branches.
First, the zygomatic nerve, is a branch of V2 that arises either within the foramen rotundum prior to entering the PPF, or just shortly after entering the PPF. This nerve then exits the PPF via the inferior orbital fissure alongside the infraorbital nerve. It is discussed in more detail below under the subsection: Inferior Orbital Fissure. After giving off the zygomatic nerve, V2 then connects with the PPG via the ganglionic branches (or pterygopalatine nerves) that carry parasympathetic fibers from the vidian nerve to V2.
Pterygoid (vidian) canal
The pterygoid canal, also known as the vidian canal, is another foramen found within the sphenoid bone that also provides communication between the PPF and the middle cranial fossa. It receives the vidian neurovascular bundle from the maxillary artery, vein, and nerve. The foramen is typically bilaterally symmetrical and oval in shape, while the canal takes a slightly curved track from the medio-anterior to latero-posterior axis in an arc shape. The pterygoid canal diameter can vary in size but generally widens in the anterior direction and typically lies within the sphenoid sinus floor.
Vidian nerve, artery and vein
Coursing from anterior to posterior along the pterygoid canal, the vidian artery provides arterial supply to the Eustachian tube and portions of the pharynx and tympanic cavity. It is a branch of the maxillary artery, typically arising just after the greater palatine artery branches, and just before the maxillary artery gives rise to the sphenopalatine artery. , However, 1 study found that the vidian artery frequently arose directly from the greater palatine artery. In some variations, it will anastomose with the internal carotid artery via a second vidian artery arising on the posterior portion of the petrous ICA. In Osawa et al., this additional vascularization from the petrous carotid was noted in 45% of specimens. Together, the vidian vasculature subsequently gives small branches which supply the vidian nerve, pterygoid canal and its periosteum. The vidian nerve, which traverses the vidian canal alongside its artery and vein, arises from the PPF as a branch from the maxillary nerve.
Pharyngeal canal (palatosphenoidal canal)
Also on the posterior wall of the PPF, the pharyngeal canal offers direct communication with the nasopharynx. , Also named the palatovaginal canal, it transmits the pharyngeal nerve, artery, and vein. It lies medial to the vidian canal and posteromedial to the foramen rotundum. Specifically, it can be found in the same coronal plane at the same horizontal level as the vidian canal but occasionally appears obliquely. Both canals can be noted to have a divergent trajectory from the PPF. It courses posteromedially in the roof of the nasopharynx into the roof of the nasopharynx , The nasopharyngeal opening of the canal is consistently anterior to the vaginal process of the sphenoid bone. The neurovascular bundle is enclosed within a common periosteal sheath continuous with that of the PPF. ,
Pharyngeal nerve, artery and vein
The pharyngeal artery is a branch of the proximal portion of the SPA (or the distal portion of internal maxillary artery) within the PPF The pharyngeal nerve roots at the PPG, leave posteriorly and entering the pharynx via the palatovaginal canal with a pharyngeal branch of the maxillary artery (MA) to reach the sphenoid sinus and nasopharynx.
Superior communications
Inferior orbital fissure
Superiorly, the inferior orbital fissure, also known as the sphenomaxillary fissure or infraorbital fissure, is a space between the maxilla and sphenoid bone that connects the orbit with the infratemporal fossa, PPF and temporal fossa. It is most narrow at its center and has a long axis that lies along the line between the zygomaticofacial foramen and optic canal. It gives passage to multiple structures, including the infraorbital neurovascular bundle, the zygomatic nerve, and the orbital branches of the pharyngeal nerve.
Infraorbital nerve and artery
The infraorbital artery courses alongside the infraorbital nerve to supply the lower eyelid, midface, and upper lip regions. It originates from the deep branches of the maxillary artery as one of the first branches arising within the PPF. , Though some variation exists, it is most commonly found to branch at a common trunk with the PSAA. This branching was found to occur at the posterior wall of the maxilla. While in some studies, the IOA was noted to branch directly from the PSAA, there exists significant variation in the reported branching patterns. In general, the infraorbital nerve (ION) branches from the pterygopalatine ganglion or the posterior superior alveolar nerve, traveling laterally at a slightly upward trajectory to enter the inferior orbital fissure. Though some studies suggest it is equally likely the posterior alveolar branch emerges from the ION. The ION travels linearly from the foramen rotundum and is found to be lateral to the pterygoid ridge. ,
Zygomatic branch of the maxillary nerve
Originating in the PPF the zygomatic branch of the maxillary nerve enters the orbit via the inferior orbital fissure. It travels along the lateral wall before branching into the zygomaticotemporal and zygomaticofacial nerves. , The Zygomaticotemporal nerve continues along the inferolateral angle of the orbit before giving rise to the lacrimal nerve. Commonly, accessory branches arise anterior to, lateral to or within the immediate vicinity of the main branch. The zygomaticofacial nerve also courses the inferolateral angle of the orbit to the zygomaticofacial foramen. Both branches are described to have anastomoses with the zygomatic branch of the facial nerve. ,
Inferior communications
Greater palatine canal
Situated at the posterior hard palate, the greater palatine foramen (GPF) provides direct communication between the PPF and the oral cavity. The greater palatine canal is formed between the articulation of the maxilla and the greater palatine sulcus of the palatine bone. It is often termed the pterygopalatine canal and from it, arises a smaller accessory canal, the lesser palatine canal. Literature’s description of the foramen’s location on the hard palate, varies greatly, with some investigators reporting it lies between the 2nd and 3rd maxillary molar teeth, , opposite the 2nd maxillary molar teeth, opposite the 3rd maxillary molar teeth or distal to the 3rd maxillary molar. , These differences in anatomical location appear related to differences between males and females. , Moreover, while it was common to see only 1 GPF in the majority of cases, double or triple openings have also been documented. Nevertheless, this bony opening is most often described as either oval in shape, , , , or lancet or round. , The direction in which the cavity opens into the oral cavity is still up for debate, with significant heterogeneity reported but main reports suggesting either an inferiorly antero-medially vs inferiorly antero-laterally directionality. ,
Greater palatine artery, nerve, vein
Coursing within the greater palatine canal, is the greater palatine neurovascular bundle, including the artery, nerve and vein, which enter the oral cavity via the greater palatine foramen and runs anteriorly in a bony groove between the junction of the maxillary alveolar ridge and the horizontal plate of the maxilla, on the inferior surface of the hard palate. , Here, it anastomoses with branches of the nasopalatine bundle from the nasal cavity. The bundle travels as a thick bundle adjacent to the molars whose diameter begins to decrease gradually at the level of the premolars. Similar findings were noted across 2 cadaveric studies in which the diameter decreased from approximately 2.65 ± 1.3 mm) at the GPF, gradually decreased to 1.96 ± 0.9 mm at the first premolar area and 1.1 ± 0.5 mm at the incisive foramen. , Branching of the greater palatine artery is observed along the entire course. This study also noted mild differences in branching between males and females, in which the greater palatine artery had the most branches at the first premolar in women (38%) and was commonly observed at the first and second premolars in men (56%). The greater palatine nerve is noted to travel medial to the descending palatine artery.
Lesser palatine nerves
The lesser palatine nerve arises from the maxillary division of the trigeminal nerve, just after emerging from the foramen rotundum where it enters the PPF. It leaves the PPF via the lesser palatine canal, just posterior to the greater palatine canal. It emerges on the hard palate through the lesser palatine foramen and continues to supply the uvula, soft palate and palatine tonsils.
Descending palatine artery
The internal maxillary artery gives rise to the descending palatine artery upon entering the PPF. This branch then travels through the greater palatine canal in an inferior, anterior, and slightly medial direction to the nasal floor and then exits the greater palatine foramen. It travels a short distance and divides into the greater and lesser palatine arteries within the greater palatine canal.
Discussion
Historically, approaches to the PPF have been invasive open craniofacial approaches. These include an anterior approach, popularized by Crockett and Barbosa in the 1960s, , and a lateral approach, popularized by Conley and Dingman in 1970. , These techniques involved significant facial and/or oral incisions, oftentimes with midfacial degloving and disturbances to the facial skeleton. The transmaxillary approach was first introduced in the 1890s by Caldwell for approach to the maxillary sinus. Later this approach was popularized for access to disease involving the PPF and beyond.
An endoscopic approach to this region was first described by Klossek et al. in 1994 for an approach to a schwannoma of the PPF. This approach was later described and modified by Alfieri et al. in 2003. Over the ensuing decades, this endoscopic approach has been heavily studied and honed, and is now the most commonly employed approach to the PPF. Not only can a minimally invasive endoscopic approach offer access to the PPF, but it can also provide access to spaces beyond the PPF, including the lateral recess of the sphenoid sinus and the middle cranial fossa.
There are several variations of the endoscopic approach, including the ipsilateral transnasal approach, the endoscopic transmaxillary approach (endoscopic Caldwell-Luc), the combined transnasal and transmaxillary approach, , a contralateral transnasal transseptal approach, and a transorbital approach. Of these, the endoscopic ipsilateral transnasal approach is the most employed. In this technique, the PPF is first accessed via a wide maxillary antrostomy and removal of the crista ethmoidalis, along with the related vertical portion and orbital process of the palatine bone. This step effectively removes the medial wall of the PPF. Next, the posterior wall of the maxillary sinus, which forms the anterior wall of the PPF, is carefully removed. From here, the sphenopalatine artery and the remaining contents of the PPF can be accessed for disease directly involving the PPF, or these contents can be mobilized and retracted laterally for access to disease involving spaces deeper within the skull. ,
Aside from tumor resection, endoscopic surgery is also utilized to perform both vascular and neural procedures involving various clinically relevant structures that lie within the PPF. From a vascular standpoint, recall that the sphenopalatine artery arises from the maxillary artery and then exits the PPF via the sphenopalatine foramen on its way to the posterior nasal cavity. The sphenopalatine artery and its subsequent branches supply various regions of nasal and septal mucosa and are frequent culprits that cause posterior epistaxis. This diagnosis often involves severe nasal bleeding which requires nasal packing, and often control of epistaxis in the operating room via ligation of the sphenopalatine artery. Outside of epistaxis, the sphenopalatine artery’s supply of the posterior septal mucosa is leveraged surgically as a tool for reconstruction via the nasoseptal flap. In this technique, the septal mucosa is lifted off the underlying septal cartilage and vomer, and the pedicle of mucosa that carries the posterior septal artery, from the sphenopalatine artery, is kept intact and serves as the fulcrum for rotation of the flap towards skull base defects in need of repair. The PPF itself can become more intimately involved in the raising of a nasoseptal flap when additional length of the flap is needed to reach the point of reconstruction. , To achieve this, the surgeon can access the PPF and release the sphenopalatine artery, and even mobilize the internal maxillary artery to achieve the necessary reach.
Lastly, we will address surgical intervention on the vidian nerve. As discussed previously, the vidian nerve enters the PPF through the vidian canal, and synapses at the PPG prior to continuing on to provide parasympathetic innervation to the nasal mucosa, palate, and lacrimal gland. A vidian neurectomy is a transnasal endoscopic procedure that is employed to transect the vidian nerve in order to reduce parasympathetic innervation to the mucosa. This is sometimes utilized in the management of vasomotor rhinitis, a syndrome of frequent rhinorrhea without a known allergic or infectious trigger, thought to be due to an imbalance in the sympathetic and parasympathetic innervation to the nasal mucosa. In cases refractory to medical management, vidian neurectomy may be employed. The approach to the vidian nerve can vary, but 1 technique involves a similar approach as to that used for access to the sphenopalatine artery for ligation. After the SPA is identified and ligated, the orbital and sphenoidal processes of the palatine bone are removed to expose the periosteum overlying the PPF contents. Next, the vidian nerve is identified as it exits the vidian canal and is transected. While an excellent application of the anatomy of the PPF and surrounding structures, vidian neurectomy has largely been replaced by an in-office procedure involving cryoablation of the posterior nasal nerves.
Conclusion
The PPF is a complex anatomical region that is best appreciated in 3D. It is a clinically relevant space frequently encountered by otolaryngologists dealing with neoplastic spread, infection, or vascular anomalies. By combining technologic advances in 3D medical illustration, 3D modeling from cross sectional imaging, and cadaveric peer reviewed literature an accurate 3D model of the PPF was constructed. A detailed understanding of this complex surgical anatomy is vital to the surgeon. To our knowledge, this surgically accurate 3D model is unprecedented and will serve as an educational tool for learners seeking an intimate knowledge of the PPF.
Model QR code
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
The present study received internal departmental funding, without commercial support or sponsorship.
Presented at the Minnesota Academy of Otolaryngology 2024 Annual Meeting on January 20, 2024.
References
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