Thomas von Arx1 2 Extraoral anatomy in CBCT - Michael M ...€¦ · SWISS DENTAL JOURNAL SSO VOL...

SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020

RESEARCH AND SCIENCE216

SUMMARY

In this review about extraoral anatomy as depict-

ed by cone beam computed tomography, the ret-

romaxillary region is discussed. A medium-sized

(6 × 6 cm) or large (≥ 8 × 8 cm) field of view of the

maxilla will inevitably depict the retromaxillary

region that can be considered a “transition” zone

between the viscerocranium and the neurocrani-

um. Major structures of the region include the

sphenoid bone and the pterygopalatine fossae.

The sphenoid bone is a single but complex bone

located between the maxilla and the brain. It is

composed of a central body, bilateral greater and

lesser wings, and pterygoid processes. Important

neurovascular structures pass through the sphe-

noid bone: the optic nerve and the ophthalmic

artery via the optic canal, the maxillary nerve

via the foramen rotundum, and the pterygoid

nerve via the Vidian canal. The central body of

the sphenoid bone also contains the highly vari-

able sphenoid sinus that is the most posteriorly

located paranasal sinus. The bilateral pterygopal-

atine fossae behind the maxillary sinuses contain

several important neurovascular structures that

supply the maxilla and the midface.

KEYWORDSAnatomy CBCT Retromaxillary region Sphenoid bone Sphenoid sinus Pterygopalatine fossa

Thomas von Arx1

Scott Lozanoff2

Michael M. Bornstein3,4

1 Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Switzerland

2 Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medi-cine, University of Hawaii, Honolulu, USA

3 Oral and Maxillofacial Radiol-ogy, Applied Oral Sciences and Community Dental Care, Faculty of Dentistry, The Uni-versity of Hong Kong, Prince Philip Dental Hospital, Hong Kong SAR, China

4 Department of Oral Health & Medicine, University Center for Dental Medicine Basel UZB, University of Basel, Basel, Switzerland

CORRESPONDENCEProf. Dr. Thomas von ArxKlinik für Oralchirurgie und Stomatologie Zahnmedizinische Kliniken der Universität Bern Freiburgstrasse 7 CH-3010 Bern Tel. +41 31 632 25 66 Fax +41 31 632 25 03 E-mail: [email protected]

SWISS DENTAL JOURNAL SSO 130: 216–228 (2020)Accepted for publication: 16 September 2019

Extraoral anatomy in CBCT - a literature review

Part 3: Retromaxillary region

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217RESEARCH AND SCIENCE

IntroductionThis third literature review about extraoral anatomy as depicted and seen in cone beam computed tomography (CBCT) scans ad-dresses the retromaxillary region. The latter can be defined as the zone immediately posterior to the maxillary bones on both sides. The region includes the sphenoid bone and the pterygo-palatine fossae. Both anatomical structures are usually depicted on CBCT scans of the posterior maxilla and/or the maxillary sinus performed, for example, for treatment planning prior to dental implant placement including sinus floor elevation proce-dures or periapical surgery of molars. The single sphenoid bone presents a complex morphology and it can be regarded as a “transition” bone between the viscerocranium and the neuro-cranium (Fig. 1). The sphenoid bone contributes to the orbital apex, to the anterior and middle cranial fossae, and to the later-al wall of the skull (Budu et al. 2013). The sphenoid bone also contains the highly variable sphenoid sinus that may have clini-cally perilous anatomical relations with the optic nerves and the internal carotid arteries.

The bilateral pterygopalatine fossae are located behind the posterior aspect of the maxillary bones. The fossae are consid-ered the “control center” of the maxilla since they contain the maxillary nerve, the maxillary artery, and the pterygopalatine ganglion, all supplying the maxilla as well as the entire midface. Due to its inherent complex location, the pterygopalatine fossa can potentially act as a natural conduit for the spread of inflam-matory and neoplastic diseases across the various deep spaces of the head and neck (Tashi et al. 2016).

Sphenoid boneThe anatomy of the sphenoid bone (“sphen” in Greek means wedge-shaped) is complicated since it is not a compact struc-ture but rather presents with multiple wings and processes originating from a central body (Chong et al. 1998; Jaquesson et al. 2017) (Fig. 2). Furthermore, the sphenoid bone contains several fissures, canals and foramina that convey neurovascular structures from the middle cranial fossa to the maxillofacial re-gion. The sphenoid bone contributes superiorly to the anterior and middle cranial fossae, anterolaterally to the orbital walls, laterally to the temporal fossae, and inferoanteriorly to the nasal cavities and to the pterygopalatine fossae.

The sphenoid bone has long been recognized as comprising four parts (Fawcett 1910):– central body– greater wings– lesser wings– pterygoid processes

When viewed from anterior, the greater wings resemble the outstretched wings of a bird with the pterygoid processes ap-pearing as extended limbs (Chong et al. 1998).

Central bodyThe central body of the sphenoid bone has a cuboidal shape and is actually hollowed by the sphenoid sinus. The body is the ori-gin for the paired greater and lesser wings as well as for the pterygoid processes (Fig. 2). Superiorly, a bony depression (sella turcica = Turkish saddle) serves as the hypophyseal or pituitary fossa. Anterior (large) and posterior (small) clinoid processes represent the four corners of the sella turcica. Lateral to the sellalies the paired cavernous sinus, a large venous cavity. The dor-sum sellae forms the posterior boundary of the sella turcica and

extends laterally as the posterior clinoid processes (Chong et al. 1998). The sphenoid body also contributes to the clivus that ex-pands posteriorly from the dorsum sellae and slopes downwards to the foramen magnum (Fig. 3). The inferior face of the clivusrepresents the roof of the nasopharynx (Chong et al. 1998).

Three bony canals run through the lateral aspects of the sphe-noid body: superiorly the optic canal, midway the foramen ro-tundum, and inferiorly the pterygoid (Vidian) canal. These ca-nals transmit significant neurovascular structures to the orbits and pterygopalatine fossae (see below).

Sphenoid sinusThe sphenoid sinus (SPS) is located within the central portion of the sphenoid bone, i. e. the sphenoid body (Fig. 3–5). The SPS shows great variability with regard to size, shape and compart-mentalization. The SPS is the most posterior of the paranasal si-nuses. It drains into the sphenoethmoidal recess that is located superior or posterior to the superior nasal turbinate (Anusha et al. 2014; von Arx et al. 2019). Usually, the SPS is divided by an intervening septum into two compartments. Since the septum is rarely located in the midsagittal plane but rather deviated laterally, the SPS has asymmetric cavities. Often, there is a dominant cavity on one side (Tan & Ong 2007). Some SPS may demonstrate subdivision into several recesses by accessory sep-ta. The average volume of the SPS ranges between 3 and 10 ml (Anusha et al. 2014).

The extent of the SPS is commonly divided into three main types (Budu et al. 2013; Anusha et al. 2014): (1) the conchal type represents a very small sinus or pneumatization is completely absent and the “sinus” is filled with trabecular bone; (2) the presellar (or juvenile) type has pneumatization extending to the sella turcica but not posterior to it; (3) the sellar (or adult) type demonstrates complete pneumatization of the sphenoid body.

Fig. 1 The sphenoid bone (highlighted in blue) is a viscerocranial component of the craniofacial skeleton that forms a transition zone articulating with contiguous neurocranial elements.

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Furthermore, the SPS may expand into the greater and lesser sphenoid wings, into the pterygoid processes, as well as into the anterior clinoid processes (Unal et al. 2006; dal Secchi et al. 2018). Pneumatization of the anterior clinoid process by the sphenoid sinus has been reported in 6–29.3% (Anusha et al. 2015). Generally, extensive pneumatization of the SPS can be associated with irregularities in the sinus walls featuring pro-trusions and recesses (dal Secchi et al. 2018).

Four vital structures run along the sphenoid sinus: the optic nerve in the superolateral wall, the internal carotid artery in the midlateral wall, the maxillary division of the trigeminal nerve in the inferolateral wall, and the Vidian nerve in the floor of the si-nus (Tan & Ong 2007). All of these neurovascular structures may indent the walls of the SPS or even show bulging into the sinus cavity (Unal et al. 2006).

The internal carotid artery (ICA) coursing through the lateral wall of the SPS is essentially a reflection of its intracavernous portion (Anusha et al. 2015). In fact, the ICA is the most medial element of the cavernous sinus, and it often has a direct relation with the lateral wall of the SPS. Variations of the ICA position may include dehiscence of the overlying bone or a protrusion of the ICA into the SPS. Depending on the degree of pneumati-zation, bulging of the ICA into the sinus has been reported in 34–93% (Budu et al. 2013). Similarly, the optic canal running through the roof of the SPS may show a dehiscence or may pro-trude from the sinus roof into the SPS (Anusha et al. 2015).

Greater wingsThe paired greater wings originate from the lateral aspects of the central sphenoid body (Fig. 2). The greater wings have three sur-faces: (1) an anterior orbital surface contributing to the lateral orbital wall – the orbital surface is bounded by the superior and inferior orbital fissures; (2) an external surface forming part of the lateral wall of the cranium; and (3) an internal posterior sur-face that is oriented horizontally and contributes to the anterior portion of the middle cranial fossa. The greater wings contain three important foramina, i. e. rotundum, ovale and spinosum. The foramen rotundum is located anteromedially while the fora-men ovale and foramen spinosum are positioned posterolaterally (Chong et al. 1998). The sphenoid spine, a sharp bony projection behind the foramen spinosum, also belongs to the greater wing.

Lesser wingsThe paired lesser wings protrude from the anterosuperior aspect of the central sphenoid body (Fig. 2). They have a triangular shape, fuse anteriorly with the frontal bone, and contribute to the anterior cranial fossa. The lesser wings are oriented in the axial plane and show pointed bony projections extending poste-riorly over the sella turcica, i. e. the anterior clinoid processes.

The medial attachments of the lesser wings to the sphenoid body have two roots that define the optic canal (Chong et al. 1998). The lower root, also known as the optic strut, separates the optic canal from the superior orbital fissure. The optic canal

Fig. 2 Anterior view of the isolated sphenoid bone 1 = body of sphenoid bone; 2 = sphenoid crest; 3 = aperture of sphenoid sinus; 4 = lesser wing; 5 = orbital surface of greater wing; 6 = cranio-orbital foramen; 7 = superior orbital fissure; 8 = anterior opening of optic canal; 9 = foramen rotundum; 10 = pterygoid (Vidian) canal; 11 = vaginal process; 12 = palatovaginal (pharyngeal) canal; 13 = vomerovaginal canal; 14 = lateral plate of pterygoid process; 15 = medial plate of pterygoid process; 16 = sphenoid spine; 17 = dorsum sellae

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is the only structure passing through the lesser wing (Chong et al. 1998).

Optic canalThe paired optic canal (OPC) runs through the superior aspect of the sphenoid body in an anterolateral direction towards the apex of the orbital cavity (Fig. 2). The OPC is the most superior opening of the middle cranial fossa. It transmits the optic nerve (CN II) and the ophthalmic artery to the orbit. The diameter and the length of the canal range between 3.7 and 6.3 mm and 8 and 12 mm, respectively (Edwards et al. 2018).

Foramen rotundumThe foramen rotundum lies in the anteromedial portion of the greater sphenoid wing (Fig. 2 and 5). It represents the gate-way for the maxillary division of the trigeminal nerve (CN V2)

from the middle cranial fossa to the pterygopalatine fossa. The foramen is predominantly circular with an average size of 3.9 × 3.1 mm (Edwards et al. 2018). Berge & Bergman (2001) who evaluated 100 randomly selected dry skulls reported an average size of 3.3 × 2.7 mm (range 2 × 2 to 4.5 × 3.5 mm). In a CT study of 100 patients, the mean distance from the posterior wall of the maxillary sinus to the anterior opening of the foramen rotun-dum was 6.3 mm (range 4.4 to 8.5 mm) (Vuksanovic-Bozaric et al. 2019). The distance from the greater palatine foramen to the foramen rotundum was evaluated in 50 Chilean adult human dry skulls (Soto et al. 2015). The mean lengths were 31.95 mm on the right side and 32.49 mm on the left side.

Foramen ovaleThe foramen ovale (FOv) lies in the posterolateral portion of the greater sphenoid wing (Fig.6–8). The predominant shape of the

Fig. 3 Midsagittal CBCT image of a 55-year-old male 1 = body of sphenoid bone; 2 = sphenoid sinus; 3 = sella turcica; 4 = dorsum sellae; 5 = clivus; 6 = syndesmosis between sphenoid bone and vomer; 7 = vomer; 8 = hard palate; 9 = soft palate; 10 = nasopharynx; 11 = atlas; 12 = dens axis; 13 = body of axis; 14 = base of tongue; 15 = tip of epiglottis

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BB

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Fig. 5 Coronal CBCT images of three patients showing three different config-urations of the sphenoid sinus and its neighboring structures: (A) Foramina rotunda and pterygoid canals are fully embedded in the body of the sphenoid bone (59-year-old female). (B) The sphenoid sinus reaches the level of the pterygoid canals (13-year-old male). (C) The sphenoid sinus extends deep into the base of the pterygoid process (53-year-old female). 1 = sphenoid sinus; 1* swelling of sphenoid sinus membrane; 2 = sphenoid sinus septum; 2* = accessory septum; 3 = foramen rotundum; 4 = pterygoid (Vidian) canal; 5 = base of pterygoid process; 6 = lateral plate of pterygoid process; 7 = medial plate of pterygoid process; 8 = hamulus; 9 = pterygoid fossa; 10 = vomer

Fig. 4 Cadaveric dissection showing midsagittal view of sphenoid sinus and contiguous structures 1 = sphenoid sinus; 2 = sella turcica with hypophysis; 3 = clivus; 4 = lower portion of central body of sphenoid bone; 5 = nasopharynx; 6 = perpendicu-lar plate of ethmoid bone; 7 = vomer; 8 = hard palate; 9 = soft palate

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FOv is oval, with average dimensions of 7.11 × 3.60 mm (range 5 × 2 mm to 8 × 7 mm) (Berge & Bergman 2001). The FOv connects the middle cranial fossa with the infratemporal fossa. Intracra-nially, the internal carotid artery runs directly posterior to the foramen. The FOv transmits the third division of the trigeminal

nerve, i. e. the mandibular nerve (CN V3). It may further contain an accessory branch of the middle meningeal artery, small em-issary veins, or even a small venous plexus joining the pterygoid plexus to the cavernous sinus (Edwards et al. 2018).

The contents of the FOv are frequently interrupted by liga-ments that can ossify. The pterygospinous ligament (ligament of Civinini) that connects the sphenoid spine with the lateral plate of the pterygoid process can ossify and hinder the access to the FOv (Tubbs et al. 2009). Similarly, the pterygoalar liga-ment (Hyrtl’s ligament) can ossify resulting in the porus crota-phiticobuccinatorium (Hyrtl’s foramen or pterygoalar foramen) also potentially compressing branches of the mandibular divi-sion of the trigeminal nerve (Kamath & Vasantha 2014).

Frequently, a small emissary sphenoidal foramen (also known as foramen of Vesalius) is present anteromedially to the FOv (Fig. 7). This foramen contains the emissary sphenoidal vein as an additional venous pathway connecting the cavernous sinus with the pterygoid venous plexus (Natsis et al. 2018). It can ap-pear as single or double openings that are uni- or bilateral (Kale et al. 2009) and vary between 0.5 and 2.86 mm (Boyd 1930; Rey-mond et al. 2005). The foramen of Vesalius is an anatomical vari-ant, but ipsilateral enlargement of this opening may relate to carotid-cavernous fistulas or may also relate to intracranial perineural or nasopharyngeal extension (Lanzieri et al. 1988).

Foramen spinosumThe foramen spinosum (FSp) got its name from the sphenoid spine lying posteriorly to the foramen (Krayenbühl et al. 2008)(Fig. 6 and 7). The FSp is located posterolaterally to the FOv. The average size of the FSp is 2.4 × 2 mm (range 1 × 1 to 4 × 3 mm) (Berge & Bergman 2001). Occasionally, the FSp may be absent or

Fig. 6 Illustration of the central portion of the skull base (inferior view) 1 = horizontal plate of palatine bone; 2 = greater palatine foramen; 3 = lesser palatine foramen; 4 = pyramidal process of palatine bone; 5 = hamulus; 6 = medial plate of pterygoid process; 7 = lateral plate of pterygoid process; 8 = pterygoid fossa; 9 = vomer; 10 = inferior surface of body of sphenoid bone; 11 = pharyngeal opening of palatovaginal canal; 12 = pharyngeal opening of vomerovaginal canal; 13 = posterior opening of pterygoid (Vidian) canal; 14 = inferior surface of greater wing of sphenoid bone; 15 = foramen ovale; 16 = foramen spinosum; 17 = foramen lacerum; 18 = occipital bone

Fig. 7 Inferior perspective of the foramen ovale and contiguous foramina (photograph courtesy of Dr. Robert W. Mann, Dept. of Anatomy, Biochemistry & Physiology, University of Hawaii School of Medicine) 1 = horizontal plate of palatine bone; 2 = greater palatine foramen; 3 = lesser palatine foramen; 4 = posterior nasal spine; 5 = hamulus of medial plate of pterygoid process; 6 = lateral plate of pterygoid process; 7 = foramen of Vesalius; 8 = foramen ovale; 9 = foramen of Arnold; 10 = foramen spinosum; 11 = foramen lacerum; 12 = pharyngeal opening of palatovaginal canal; 13 = vomer; 14 = pharyngeal opening of vomerovaginal canal; 15 = inferior surface of body of sphenoid bone; 16 = occipital bone; 17 = inferior surface of greater wing of sphenoid bone

Fig. 8 Cadaveric dissection of the right retromaxillary region (lateral view). The lateral wall of the maxillary sinus and the lateral plate of the pterygoid process have been removed. 1 = foramen ovale; 2 = mandibular division of trigeminal nerve (CN V3); 3 = foramen spinosum; 4 = middle meningeal artery; 5 = maxillary artery; 6 = external carotid artery; 7 = superficial temporal artery; 8 = inferior alveo-lar nerve; 9 = lingual nerve; 10 = tensor veli palatini muscle; 11 = pterygopala-tine fossa; 12 = infraorbital nerve; 13 = maxillary sinus; 14 = medial plate of pterygoid process; 15 = maxillary tuberosity

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confluent with the FOv (Ginsberg et al. 1994). In a quantitative study of twelve cadaver heads, the median distance between the FSp and the FOv was 4.75 mm (range 2 to 7.5 mm) (Kray-enbühl et al. 2008). The FSp contains the middle meningeal artery and the middle meningeal veins that anastomose with the venous plexus of the FOv or the cavernous sinus. Further-more, the recurrent branch (nervus spinosus) of the mandibular nerve runs through the FSp (Krayenbühl et al. 2008; Edwards et al. 2018).

The foramen petrosum (foramen of Arnold) is a variably ap-pearing foramen between the FSp and FOv (Fig. 7). It transmits the lesser petrosal nerve that runs as a parasympathetic branch of CN IX to innervate the parotid gland.

Pterygoid processThe bilateral pterygoid process (PTP) is the most inferior portion of the sphenoid bone (Fig. 2 and 6). The PTP originates inferolat-erally from the sphenoid body. The PTP is characterized by two bone plates (lamina medialis and lamina lateralis) that fuse superi-orly and anteriorly (Chong et al. 1998). When viewed from pos-teriorly, a bony depression (pterygoid fossa) can be seen be-tween the medial and lateral plates. The medial plates of the PTP form the lateral margins of the choanae.

The medial plates end inferiorly with a slender bony hook, i. e. the pterygoid hamulus. This small bony projection is of great functional importance for several muscles, i. e. the tensor veli palatini curving around the hook, the palatopharyngeus originating inter alia from the hamulus, and the upper portion of the superior pharyngeal constrictor originating from the edge of the medial pterygoid plate and from the hamulus (Oz et al. 2016).

Pterygopalatine fossaThe bilateral pterygopalatine fossa (PPF) is one of the most complex anatomical regions to understand (Bannon et al. 2018) (Fig. 9–11). It is a small and clinically poorly accessible space deep in the face bordered by three bones: maxillary, pal-atine, and sphenoid bones (von Arx & Lozanoff 2017). The PPF is bounded posteriorly by the base of the sphenoid bone and the fusion zone of the plates of the pterygoid process, anteri-orly by the posterior surface of the maxillary bone, and medi-ally by the upper part of the perpendicular plate of the palatine bone (Daniels et al. 1998).

The PPF has a four-sided pyramidal shape with its apex pointing inferiorly towards the maxillary tuberosity. The mean volume of the PPF ranges from 0.7 to 1.2 ml (Coronado et al. 2008; Stojcev Stajcic et al. 2010; Hwang et al. 2011a). Median values of height, width and depth of 159 PPF from Caucasian skulls were reported as 17.5 mm, 5 mm and 14 mm, respectively (Stojcev Stajcic et al. 2010). Rusu et al. (2013) viewed the PPF as an “intersinus space” since it is surrounded by several para-nasal sinuses, i. e. the sphenoid sinus superoposteriorly, the posterior ethmoid sinus superomedially, and the maxillary sinus anteriorly.

The PPF serves as a major crossroad between the middle cra-nial fossa, oral and nasal cavities, nasopharynx and orbit (Erdo-gan et al. 2003; Hwang et al. 2011b; Tashi et al. 2016). The mul-tiple pathways of communication from the PPF to contiguous areas are summarized in Table I. According to Meng et al. (2016),the majority of openings are located in the posterior wall of the PPF, i. e. from superolateral to inferomedial, the foramen ro-tundum, the pterygoid canal, the palatovaginal canal, and the

vomerovaginal canal (Fig. 12). The lateral wall (pterygomaxil-lary fissure), the anterior wall (inferior orbital fissure) and the medial wall (sphenopalatine foramen) each have one opening. Finally, the most inferior opening of the PPF is the pterygopal-atine canal.

Pterygomaxillary fissureThis is the principal opening of the PPF on the lateral aspect to-wards the infratemporal fossa. The main structure entering the fissure is the maxillary artery. Immediately after reaching the

Fig. 9 The four-sided pyramidal shape of the pterygopalatine fossa is taper-ing inferiorly. It has a large lateral opening (pterygomaxillary fissure). The three other walls are hidden inside the skull: anterior wall (red), medial wall (blue), and posterior wall (green). 1 = foramen rotundum; 2 = pterygoid (Vidian) canal; 3 = palatovaginal (pha-ryngeal) canal; 4 = vomerovaginal canal; 5 = sphenopalatine foramen; 6 = inferior orbital fissure; 7 = pterygopalatine canal

Fig. 10 Cadaveric dissection of the left retromaxillary region highlighting the pterygopalatine fossa (triangular dotted outline) 1 = sphenoid sinus; 2 = sella turcica; 3 = clivus; 4 = pterygoid nerve in ptery-goid (Vidian) canal; 5 = pterygopalatine ganglion; 6 = infraorbital nerve; 7 = anterior superior alveolar nerve; 8 = lateral wall of maxillary sinus; 9 = de-scending palatine nerve in pterygopalatine canal; 10 = greater palatine nerve exiting the greater palatine foramen; 11 = hard palate; 12 = soft palate; 13 = lower portion of central body of sphenoid bone

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Fig. 11 Coronal (A) and axial CBCT images at four different levels (B, C, D, E) demonstrating the pterygopalatine fossa and various communications (60-year-old female) 1 = sphenoid sinus; 2 = superior orbital fissure; 3 = foramen rotundum; 4 = foramen lacerum (posterior end of pterygoid canal); 5 = vomer; 6 = optic canal; 7 = ethmoidal air cells; 8 = cranio-orbital foramen; 9 = greater wing (orbital surface) of sphenoid bone; 10 = pterygopalatine fossa; 11 = maxillary sinus; 12 = middle turbinate; 13 = nasolacrimal canal; 14 = sphenopalatine foramen; 15 = palatovaginal (pharyngeal) canal; 16 = pterygoid (Vidian) canal; 17 = vomerovagi-nal canal

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PPF, the maxillary artery gives rise to the posterior superior alveolar artery (PSAA) that, in turn, leaves the PPF in an an-teroinferior direction through the pterygomaxillary fissure. The fissure is bounded anteriorly by the posterior aspect of the os maxilla, superiorly by the body of the sphenoid bone, and posteriorly by the lateral plate of the pterygoid process. Inferi-orly, the pterygomaxillary fissure is tapering and terminates at the pterygomaxillary suture.

Pterygopalatine canalThe pterygopalatine canal is the most inferior opening of the PPF (Fig. 13). It is the only connection from the PPF to the oral cavity. The pterygopalatine canal tapers and runs through the posterolateral wall of the maxillary sinus. Shortly after entering the os maxilla, the pterygopalatine canal divides into the greater and lesser palatine canals before terminating at the homony-mous foramina. Rapado-Gonzalez et al. (2015) measured the width of the pterygopalatine canal at the transition level to the greater and lesser palatine canals in 150 CBCTs. The mean width in the sagittal plane was 2.94 mm (right side) and 2.90 mm (left side), whereas the mean width in the coronal plane amounted to 2.16 mm (right side) and 2.18 mm (left side).

Inferior orbital fissureAnterosuperiorly, the PPF communicates with the orbit via the posteromedial portion of the inferior orbital fissure (for details,

see von Arx et al. 2020). It transmits the infraorbital nerve and vessels as well as the zygomatic branch of the maxillary nerve (Erdogan et al. 2003).

Sphenopalatine foramenThe sphenopalatine foramen (SPF) is located superomedially within the PPF and it connects the fossa with the nasal cavity (von Arx & Lozanoff 2017) (Fig. 14). The foramen is formed by two processes (orbital and sphenoid processes) of the vertical plate of the palatal bone joining the body of the sphenoid bone (Morton & Khan 1991). With regard to its nasal aspect, the SPS is positioned at the posterior end of the superior meatus or at the posterior border of the middle concha (von Arx & Lozanoff 2017). The SPF often has an hour-glass shape with an average horizontal diameter of 5.1 mm (range 4–7 mm) and an average vertical height of 6.2 mm (range 4.5–7.5 mm) (Nalavenkata et al. 2015). In a radiographic analysis of computed tomography in 50 adult patients, the SPS was located on average 26.6 ± 2.6 mm above the nasal floor and 9.2 ± 1.4 mm anterior to the choanal arch (Maxwell et al. 2017).

The SPF transmits the artery and vein of the same name as well as the nasal branches of the maxillary nerve (Erdogan et al. 2003). Variability in the number of SPF with one to three foramina per side has been reported (Scanavine et al. 2009; El-Shaarawy & Hassan 2018), probably due to a branching of the sphenopalatine artery before leaving the PPF.

Tab. I Pterygopalatine fossa (PPF): connections and contents (according to von Arx & Lozanoff 2017)

PPF connection to Location of connection within PPF

Vascular content Neural content Comment

Middle cranial fossa

Foramen rotundum Posterior wall Venous plexus Maxillary nerve (CN V2)

Pterygoid canal Posterior wall Pterygoid artery and vein Pterygoid nerve Also known as Vidian canal

Orbit

Inferior orbital fissure Anterior wall Infraorbital artery and vein Infraorbital nerve; zygo-matic branch of maxillary nerve

Nasal cavity

Sphenopalatine foramen Medial wall Sphenopalatine artery and vein

Nasal branches of maxil-lary nerve

Nasopharynx

Palatovaginal canal Posterior wall Pharyngeal branch of maxillary artery

Pharyngeal branch of maxillary nerve

Also known as pharyngeal canal

Vomerovaginal canal Posterior wall Unspecified small arteries Unspecified small nerves

Palate

Pterygopalatine canal Inferior Descending palatine artery and vein

Greater and lesser palatine nerves

Pterygopalatine canal di-vides inferiorly into greater and lesser palatine canals

Infratemporal fossa

Pterygomaxillary fissure Lateral Maxillary artery (entering),posterior superior alveolar artery (PSAA) (leaving) and vein

Posterior superior alveolar nerve(s) (PSAN)

Main opening to the lateral aspect of the skull

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Foramen rotundumThe foramen rotundum has been discussed above in the section “Sphenoid bone”.

Pterygoid canalThe pterygoid canal (PTC), also termed Vidian canal (Vidius, Ital-ian anatomist, 1509–1569), originates from the foramen lacerum in the middle cranial fossa (Fig. 11, 12 and 14). The PTC transmits the homonymous artery and nerve that comprises complex sym-pathetic and parasympathetic connections (Domenech Mateu & Pueyo Mur 1980). The canal is located within the fusion zone of the pterygoid process and the sphenoid body. It runs through the

floor of the sphenoid body in a downward and medial direction and terminates in the PPF (Osawa et al. 2009). The upper margin of the PTC may protrude from the sinus floor into the SPS de-pending on the extent of pneumatization of the sphenoid body (Chen & Xiao 2015). The PTC is roughly located in the same axial plane as the sphenopalatine foramen (Daniels et al. 1998).

In a quantitative study of 200 adults using computed to-mographic angiography, the mean length of the PTC was 14.6 ± 1.23 mm (Cheng et al. 2016). In another study with CT scans of 137 patients, the mean length of the medial canal wall amounted to 13.6 ± 2.2 mm (Fu et al. 2014). Markedly longer PTC distances were measured in a MRI study of 91 Japanese

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Fig. 12 Depiction of the right pterygopalatine fossa (triangular dotted outline) in a dry skull after partial removal of the zygomatic bone: lateral view (A), high magnification of lateral view (B). Inferior view of skull base (C). Colored cables have been inserted to highlight the pterygoid canal (blue cable), the palatovag-inal canal (green cable), and the vomerovaginal canal (red cable). 1 = medial wall of orbit; 2 = lateral wall of orbit; 3 = optic canal; 4 = superior orbital fissure; 5 = inferior orbital fissure; 6 = foramen rotundum; 7 = sphenopala-tine foramen; 8 = entrance to pterygopalatine canal; 9 = vomer; 10 = inferior surface of body of sphenoid bone; 11 = occipital bone; 12 = foramen lacerum; 13 = foramen ovale; 14 = foramen spinosum

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patients with a mean length of 19.8 mm on the right side and 19.3 mm on the left side (Tsutsumi et al. 2018).

Reported mean diameters of the PTC range from 1.4 to 3.5 mm (Hwang et al. 2011b; Sepahdari & Mong 2013; Fu et al. 2014; Chen & Xiao 2015). Commonly, the pterygoid canal is nar-rowest in its middle portion and widens anteriorly and posteri-orly, thus exhibiting a double funnel shape (Chen & Xiao 2015).The course of the PTC was found to be predominantly straight (41%) or arch-shaped (37%). An ascending or tortuous course was less frequently observed (Tsutsumi et al. 2018).

In a CT study of 100 patients, the mean distance from the posterior wall of the maxillary sinus to the anterior opening of the PTC was 8.3 mm (range 6–9.2 mm) (Vuksanovic-Bozaric et al. 2019).

The contents of the canal include the Vidian nerve (aka, nerve of the pterygoid canal) that comprises both sympathetic and parasympathetic components. The Vidian artery is particularly important since it exists as a potential collateral circulation connecting intra- and extracranial arterial circulatory systems particularly in the event of an occlusive lesion of the internal carotid artery (Takeuchi et al. 2005; Siddiqui & Chen 2009).

Palatovaginal canalThe palatovaginal canal (PVC), also known as the pharyngeal canal, is a short tunnel running below the inferior wall of the sphenoid sinus (Fig. 6, 7 and 12). It originates from the PPF and terminates posteriorly as a groove in the roof of the nasophar-ynx (Meng et al. 2016). It is commonly identified during routine CT and MRI imaging (Rumboldt et al. 2002). Within the sphe-noid body, the PVC is located between the Vidian canal (lateral-ly) and the vomerovaginal canal (medially, see below). The PVC transmits the pharyngeal artery and nerve.

In a quantitative study in 200 adults using computed to-mographic angiography, the mean length of the PVC was 7.8 ± 0.41 mm (Cheng et al. 2016). In a study with CT imaging of the PVC in 10 patients (20 sides), the mean diameter of the PVC was 1.7 mm (range 1.4–2.2 mm) (Herzallah et al. 2012).The same authors also reported a mean distance of 3.8 mm from the PVC to the Vidian canal (range 2.9–4.8 mm).

Vomerovaginal canalThe vomerovaginal canal (VVC) is located between the lateral wing of the vomer and the vaginal process of the sphenoid bone (Meng et al. 2016) (Fig. 6, 7 and 12). The VVC and the PVC are in close proximity or sometimes even overlapping one another, thereby wrongly identifying the medially located VVC as the PVC (Meng et al. 2016). The VVC conveys a branch from the sphenopalatine artery.

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Fig. 13 Sagittal (A), coronal (B) and axial (C) CBCT images depicting the pter-ygopalatine and greater/lesser palatine canals (66-year-old male) 1 = pterygopalatine fossa; 2 = pterygopalatine canal; 3 = greater palatine canal; 4 = lesser palatine canal; 5 = greater palatine foramen; 6 = maxillary sinus; 7 = perpendicular plate of ethmoid bone; 8 = vomer; 9 = inferior turbi-nate; 10 = lesser palatine foramina; 11 = lateral plate of pterygoid process; 12 = posterior nasal spine; 13 = median palatine suture; 14 = nasopalatine canal

Fig. 14 Axial CBCT image at the level of the sphenopalatine foramina (83-year-old female) 1 = pterygopalatine fossa; 2 = pterygomaxillary fissure; 3 = infratemporal fossa; 4 = sphenopalatine foramen; 5 = pterygoid (Vidian) canal; 6 = pala-tovaginal (pharyngeal) canal; 7 = foramen ovale; 8 = foramen spinosum; 9 = sphenoid sinus; 10 = maxillary sinus; 11 = middle turbinate; 12 = maxillary ostium; 13 = nasolacrimal canal; 14 = infraorbital foramen; 15 = vomer; 16 = inferolateral portion of body of sphenoid bone; 17 = glenoid fossa of temporal bone (for mandibular condyle); 18 = external acoustic canal

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DiscussionThis literature review presents an update of the clinical and ra-diological anatomy of the retromaxillary region with regard to CBCT. The retromaxillary region comprises the bilateral ptery-gopalatine fossae, the single sphenoid bone, and the nasophar-ynx. The latter structure will be addressed in detail in part 4 about extraoral anatomy in CBCT, i. e. the pharyngo-cervical region.

The retromaxillary region can be described as the transition zone between the viscerocranium (face) and the neurocranium (brain). The anatomy is complex and many important neuro-vascular structures pass through the retromaxillary region. As the pterygopalatine fossae communicate with multiple ana-tomical regions, the fossae represent major pathways for the spread of inflammatory or neoplastic diseases between these (Rusu et al. 2013).

Many of the discussed anatomical structures become visible in CBCT images of the posterior maxilla and/or the maxillary si-nuses. However, the general dentist is usually not familiar with the anatomy outside the oral cavity, and consequently, the in-terpretation of radiographs depicting the retromaxillary region can be a daunting task.

While all the above-mentioned bones (and their processes, canals or foramina) as well as spaces between bones (fossae, fissures) can be found on the corresponding CBCT images, the most striking anatomical structures of the discussed retromax-illary region include the pterygoid processes of the sphenoid bone and the sphenoid sinus. Once these structures are identi-fied, the observer can easily locate the sphenoid bone with its many canals and foramina.

Since the bilateral pterygoid processes are the most inferior parts of the sphenoid bone, they become readily visible on CBCT images of the retromaxillary region. The medial and later-al plates of the pterygoid processes appear as “extending limbs” from the body of the sphenoid bone. The latter also contains the sphenoid sinus that corresponds with the most posterior para-nasal sinus. As such, it can be easily differentiated from all other paranasal sinuses that are bilateral in contrast to the single and centrally located sphenoid sinus.

AcknowledgementThe authors thank Bernadette Rawyler, medical illustrator, and Ines Badertscher, media designer, School of Dental Medicine, University of Bern, Bern, Switzerland, for the illustrations and preparation of figures. The authors acknowledge the generous donation of the anatomical materials by anonymous individuals in the Willed Body Program, the University of Hawai’i John A. Burns School of Medicine, Honolulu, HI, USA.

We also thank Dr. Odette Engel Brügger, oral surgeon in Nidau, Switzerland, for the French translation of the summary.

Conflict of interestThe authors declare that there are no conflicts of interest related to this review.

AbbreviationsCBCT cone beam computed tomographyCN cranial nerveCT computer tomographyFOv foramen ovaleFSp foramen spinosumICA internal carotid artery

OPC optic canalPC pterygoid canalPPF pterygopalatine fossaPSAA posterior superior alveolar arteryPTP pterygoid processPVC palatovaginal canalSPF sphenopalatine foramenSPS sphenoid sinusVVC vomerovaginal canal

ZusammenfassungIn dieser dritten Arbeit über die extraorale Anatomie im DVT wird die retromaxilläre Region diskutiert. Diese Region gilt als Übergangszone zwischen dem Gesichts- (Viszerokranium) und dem Gehirnschädel (Neurokranium). Wesentliche skelet-tale Bestandteile der retromaxillären Region sind das Os sphe-noidale (Keilbein) sowie die Fossa pterygopalatina. Letztere wird oft auch als «Kontrollzentrum» des Oberkiefers bezeich-net.

Das Os sphenoidale liegt als unpaarer Knochen zentral im Schädelskelett und ist Teil der Orbita, der vorderen und mittle-ren Schädelgrube sowie der Schädelaussenwand. Der massige Körper des Os sphenoidale enthält die Keilbeinhöhle (Sinus sphe-noidalis), die eine grosse Variabilität bezüglich Grösse, Form und Unterteilung mittels Septen zeigt. Der paarige Canalis opticus(für den Sehnerven und die A. ophthalmica) zieht durch den obe-ren Teil des Keilbeinkörpers von der mittleren Schädelgrube zur Augenhöhle. Oberhalb des Keilbeinkörpers findet sich eine ty-pische sattelförmige Einziehung, die sogenannte Sella turcica,in der sich die Hypophyse befindet. Die Unterfläche des Keil-beinkörpers bildet das Dach des Nasopharynx.

Typisch für das Os sphenoidale sind auch seine diversen knö-chernen Fortsätze, wie die Alae minores und majores (lateral) sowie die Processi pterygoidei (inferior). Letztere bestehen aus einem lateralen und medialen Blatt. Am unteren Ende des me-dialen Blattes befindet sich ein kleiner bogenförmiger Fortsatz, der Hamulus. Die beidseitigen medialen Blätter bilden zusam-men mit dem Vomer die Begrenzung der Choanen, also der hin-teren Öffnungen der Nasenhöhlen.

Die beiden grossen Flügel (Alae majores) des Keilbeins enthal-ten drei wichtige Öffnungen: Foramen rotundum (für N. maxilla-ris), Foramen ovale (für N. mandibularis), und Foramen spinosum(für A. meningea media). Während die erstere eine Verbindung von der mittleren Schädelgrube zur Fossa pterygopalatina dar-stellt, ziehen die beiden letzteren zur Fossa infratemporalis. Die beiden kleinen Flügel (Alae minores) des Keilbeins bilden einen Teil der vorderen Schädelgrube. Zwischen den kleinen und grossen Flügeln befindet sich die spaltförmige Fissura orbitalis superior, durch die diverse Hirnnerven zur Augenhöhle gelan-gen.

Die Fossa pterygopalatina (Flügel-Gaumen-Grube) liegt ver-steckt zwischen Oberkiefer und Keilbein. Zugang und Anato-mie sind äusserst komplex. Die Flügel-Gaumen-Grube ist über mehrere Knochenkanäle bzw. Öffnungen mit Nachbarregionen verbunden. Über diese Verbindungen ziehen wichtige neuro-vaskuläre Strukturen zum Mittelgesicht bzw. von dort zum Gehirn. Die grösste Öffnung der Flügel-Gaumen-Grube - die Fissura pterygomaxillaris - befindet sich lateral als Verbindung zur Fossa infratemporalis. Die wesentliche Leitstruktur hier ist die A. maxillaris. Nach unten verjüngt sich die Flügel-Gaumen-Grube trichterförmig zum Canalis pterygopalatinus, der sich in der Hinterwand der Kieferhöhle in den Canalis palatinus major

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et minor aufteilt. Letztere enden im harten Gaumen palatinal der zweiten und dritten Molaren als Foramina palatinum majus et minus.

Als anteriorer Kommunikationsweg von der Flügel-Gaumen-Grube zur Augenhöhle dient die spaltförmige Fissura orbitalis inferior, die auch die hintere Grenze des Orbitabodens darstellt. Durch diese Fissur ziehen N. infraorbitalis und N. zygomaticus, bei-des Äste des N. maxillaris. Nach medial dient das Foramen spheno-palatinum als Verbindung von der Flügel-Gaumen-Grube zur Nasenhöhle. Dieses Foramen befindet sich etwa auf Höhe der hinteren Begrenzung der mittleren Nasenmuschel. Durch das Foramen sphenopalatinum ziehen die gleichnamigen Arterien und Venen zur Nase sowie die nasalen Äste des N. maxillaris.

Am komplexesten sind die Verbindungen von der Flügel-Gau men-Grube nach posterior, da sich hier gleich mehrere Öff-nungen präsentieren: Foramen rotundum, Canalis pterygoideus, Canalis palatovaginalis sowie Canalis vomerovaginalis. Die beiden letzteren ziehen als dünne Kanäle zum Nasopharynx. Der Cana-lis pterygoideus ist deutlich grösser und länger, und verbindet (wie auch das Foramen rotundum) die mittlere Schädelgrube mit der Flügel-Gaumen-Grube. Durch den Canalis pterygoideus ver-laufen die gleichnamigen Arterien und Nerven. Etwas weiter lateral und oberhalb des Canalis pterygoideus befindet sich das Foramen rotundum, dessen Leitstruktur der N. maxillaris ist.

RésuméCe troisième travail au sujet de l’anatomie extraorale au CBCT présente la zone retromaxillaire. Cette zone délimite le splanch-nocrâne du neurocrâne. Ses structures osseuses principales sont l’os sphénoïde et la fosse ptérygopalatine, connue comme « zone de contrôle » du maxillaire supérieur.

L’os sphénoïde est un os impair et médian. Il constitue une part de l’orbite, des fosses crâniennes antérieures et moyennes ainsi que de la base du crâne. Le corps massif du sphénoïde con-tient les sinus sphénoïdaux. Ces derniers ont une dimension et une forme très variables. Ils sont divisés de façon irrégulière par des septums. La structure paire du canal optique, conduisant le nerf optique et l’Arteria ophtalmica, traverse la partie supérieure du sphénoïde reliant la fosse crânienne moyenne à l’orbite. La fosse hypophysaire – une excavation à la face supérieure du corps de l’os sphénoïde – contient l’hypophyse. Elle présente la forme typique d’une selle d’où le nom de selle turcique. La face inférieure de l’os sphénoïde forme le plafond du rhinopha-rynx.

L’os sphénoïde présente différents prolongements osseux : les petites et les grandes ailes en latéral et les processus ptérygoïdes

vers le bas. Ces derniers présentent une lame latérale et une lame médiale. À l’extrémité de la lame médiale se trouve un crochet, l’Hamulus. Les deux lames médiales et le vomer for-ment les choanes, orifices postérieurs internes des fosses na-sales.

Les deux grandes ailes du sphénoïde présentent chacune trois ouvertures importantes : le foramen rond pour le nerf maxillaire reliant la fosse crânienne moyenne à la fosse ptérygopalatine, le foramen ovale pour le nerf mandibulaire et le foramen épineux pour l’artère méningée moyenne, conduisant les deux vers la Fossa infratemporalis. Les deux petites ailes du sphénoïde forment une partie de la fosse crânienne antérieure. La fente sphénoïdale est un espace entre les petites et les grandes ailes du sphénoïde qui conduit plusieurs nerfs crâniens vers l’orbite.

La fosse ptérygopalatine est cachée entre le maxillaire supé-rieur et le sphénoïde. Son accès et son anatomie sont particuliè-rement complexes. Elle présente plusieurs orifices conduisant des structures vasculo-nerveuses vers le cerveau et le massif facial. L’ouverture la plus grande – la fissure ptérygomaxillaire – communique avec la fosse infratemporale et conduit l’Arteria maxillaris comme structure la plus importante. La fosse ptérygo-palatine va s’affiner vers le bas en entonnoir et former le Canalis pterygopalatinus qui longe la paroi postérieure des sinus maxil-laires. Il se poursuit dans les Canalis palatinus major et minor qui se terminent au palais osseux à hauteur des deuxièmes ou troi-sièmes molaires et forment les Foramina palatinum majus et minus.

La fosse ptérygopalatine communique vers l’avant, donc vers l’orbite, par la Fissura orbitalis inferior qui forme aussi la limite postérieure du plancher de l’orbite. Cette fissure conduit les N. infraorbitalis et N. zygomaticus, des branches du N. maxillaris.La fosse ptérygopalatine communique vers médial avec la cavité nasale par le Foramen sphenopalatinum qui aboutit à l’arrière du cornet nasal moyen. Le Foramen sphenopalatinum conduit l’ar-tère et la veine du même nom ainsi que les branches nasales du N. maxillaris.

Les orifices postérieurs de la fosse ptérygopalatine sont les plus complexes : Foramen rotundum, Canalis pterygoideus, Canalis palatovaginalis et Canalis vomerovaginalis. Les deux derniers for-ment de fins canaux vers le rhinopharynx. Le Canalis pterygoi-deus – plus long et plus large – relie comme le Foramen rotundumla fosse crânienne moyenne à la fosse ptérygopalatine. Le canal ptérygoideus conduit l’artère et le nerf du même nom. Le Fora-men rotundum se situe en dessus, légèrement latéralement, du Canalis pterygoideus. La structure principale qu’il conduit est le N. maxillaris.

References

Anusha B, Baharudin A, Philip R, Harvinder S, Shaffie B M: Anatomical variations of the sphe-noid sinus and its adjacent structures: A review of existing literature. Surg Radiol Anat 36: 419–427 (2014)

Anusha B, Baharudin A, Philip R, Harvinder S, Shaffie B M, Ramiza R R: Anatomical variants of surgically important landmarks in the sphenoid sinus: A radiologic study in Southeast Asian pa-tients. Surg Radiol Anat 37: 1183–1190 (2015)

Bannon R, Parihar S, Skarparis Y, Varsou O, Cezay-irli E: 3D printing the pterygopalatine fossa: A negative space model of a complex structure. Surg Radiol Anat 40: 185–191 (2018)

Berge J K, Bergman R A: Variations in size and in symmetry of foramina of the human skull. Clin Anat 14: 406–413 (2001)

Boyd G I: The emissary foramina of the cranium in man and the anthropoids. J Anat 65: 108–121 (1930)

Budu V, Mogoanta C A, Fanuta B, Bulescu I: The an-atomical relations of the sphenoid sinus and their implications in sphenoid endoscopic sur-gery. Rom J Morphol Embryol 54: 13–16 (2013)

Chen J, Xiao J: Morphological study of the ptery-goid canal with high-resolution CT. Int J Clin Exp Med 8: 9484–9490 (2015)

Cheng Y, Gao H, Song G, Li Y, Zhao G: Anatomical study of pterygoid canal (PC) and palatovaginal canal (PVC) in endoscopic trans-sphenoidal ap-proach. Surg Radiol Anat 38: 541–549 (2016)

Chong V F, Fan Y F, Tng C H: Pictorial review: Ra-diology of the sphenoid bone. Clin Radiol 53: 882–893 (1998)

Coronado G C, Suazo G I, Cantin L M, Zavando M D:Relationship between pterygopalatine fossa vol-ume and cephalic and upper facial indexes. Int J Morphol 26: 393–396 (2008)

216-228_T1-1_vonarx_EDF.indd 227 27.02.20 07:23



Dal Secchi M M, Dolci Rll, Teixeira R, Lazarini P R:An analysis of anatomic variations of the sphe-noid sinus and its relationship to the internal carotid artery. Int Arch Otorhinolaryngol 22: 161–166 (2018)

Daniels D L, Mark L P, Ulmer J L, Mafee M F, McDan-iel J, Shah N C, Erickson S, Sether L A, Jara-deh S S: Osseous anatomy of the pterygopalatine fossa. Am J Neuroradiol 19: 1423–1432 (1998)

Domenech Mateu J M, Pueyo Mur F J: Development and arrangement of the tympanic plexus and the nerve of the pterygoid canal during the hu-man embryonic and fetal periods. Acta Morphol Neerl Scand 18: 253–272 (1980)

Edwards B, Wang J M, Iwanaga J, Loukas M, Tubbs R S: Cranial nerve foramina part I: A re-view of the anatomy and pathology of cranial nerve foramina of the anterior and middle fossa. Cureus 10: e2172 (2018)

El-Shaarawy Eaa, Hassan S S: The sphenopalatine foramen in man: Anatomical, radiological and endoscopic study. Folia Morphol (Warsz) 77: 345–355 (2018)

Erdogan N, Unur E, Baykara M: CT anatomy of pterygopalatine fossa and its communications: A pictorial review. Comput Med Imaging Graph 27: 481–487 (2003)

Fawcett E: Notes on the development of the hu-man sphenoid. J Anat Physiol 44: 207–222 (1910)

Fu Z, Chen Y, Jiang W, Yang S, Zhang J, Zhang W, Zhang S, Ke Y: The anatomical and clinical details of the pterygoid canal: A three-dimensional re-constructive virtual anatomic evaluation based on CT. Surg Radiol Anat 36: 181–188 (2014)

Ginsberg L E, Pruett S W, Chen M Y, Elster A D:Skull-base foramina of the middle cranial fossa: Reassessment of normal variation with high-resolution CT. Am J Neuroradiol 15: 283–291 (1994)

Herzallah I R, Amin S, El-Hariri M A, Casiano R R:Endoscopic identification of the pharyngeal (palatovaginal) canal: An overlooked area. J Neurol Surg B Skull Base 73: 352–357 (2012)

Hwang S H, Joo Y H, Seo J H, Kim S W, Cho J H, Kang J M: Three-dimensional computed tomog-raphy analysis to help define an endoscopic en-donasal approach of the pterygopalatine fossa. Am J Rhinol Allergy 25: 346–350 (2011a)

Hwang S H, Seo J H, Joo Y H, Kim B G, Cho J H, Kang J M: An anatomic study using three-di-mensional reconstruction for pterygopalatine fossa infiltration via the greater palatine canal. Clin Anat 24: 576–582 (2011b)

Jacquesson T, Mertens P, Berhouma M, Jouan-neau E, Simon E: The 360 photography: A new anatomical insight of the sphenoid bone. Inter-est for anatomy teaching and skull base surgery. Surg Radiol Anat 39: 17–22 (2017)

Kale A, Aksu F, Ozturk A, Gurses I A, Gayretli O, Zeybek, F G, Bayraktar B, Ari Z, Onder N: Foramen of Vesalius. Saudi Med J 30: 56–59 (2009)

Kamath K, Vasantha K: Anatomical study of the pterygospinous and pterygoalar bar in human skulls with their phylogeny and clinical signifi-cance. J Clin Diagn Res 8: 10–13 (2014)

Krayenbühl N, Isolan G R, Al-Mefty O: The fora-men spinosum: A landmark in middle fossa sur-gery. Neurosurg Rev 31: 397–401 (2008)

Lanzieri C F, Duchesneau P M, Rosenbloom S A, Smith A S, Rosenbaum A E: The significance of asymmetry of the Foramen of Vesalius. Am J Neuroradiol 9: 1201–1204 (1988)

Maxwell A K, Barham H P, Getz A E, Kingdom T T, Ramakrishnan V R: Landmarks for rapid localiza-tion of the sphenopalatine foramen: A radio-graphic morphometric analysis. Allergy Rhinol (Providence) 8: 63–66 (2017)

Meng Q, Lu Y, Shi L, Lei Y: The posterior groove as a landmark for location of the palatovaginal canal in axial computed tomography. Surg Radiol Anat 38: 825–833 (2016)

Morton A L, Khan A: Internal maxillary artery vari-ability in the pterygopalatine fossa. Otolaryngol Head Neck Surg 104: 204–209 (1991)

Nalavenkata S, Meller C, Novakovic D, Forer M, Patel N P: Sphenopalatine foramen: Endoscopic approach with bony landmarks. J Laryngol Otol 129(Suppl 3): S47–52 (2015)

Natsis K, Piagkou M, Repousi E, Tegos T, Gkioka A, Loukas M: The size of the foramen ovale regard-ing to the presence and absence of the emissary sphenoidal foramen: Is there any relationship between them? Folia Morphol (Warsz) 77: 90–98 (2018)

Osawa S, Rhoton A L, Seker A, Shimizu S, Fujii K, Kassam A B: Microsurgical and endoscopic anat-omy of the vidian canal. Neurosurgery 64 (5Suppl 2): 385–411 (2009)

Oz U, Orhan K, Aksoy S, Ciftci F, Özdoganoglu T, Rasmussen F: Association between pterygoid ha-mulus length and apnea hypopnea index in pa-tients with obstructive sleep apnea: A combined three-dimensional cone beam computed to-mography and polysomnographic study. Oral Surg Oral Med Oral Pathol Oral Radiol 121: 330–339 (2016)

Rapado-Gonzalez O, Suarez-Quintanilla J A, Otero- Cepeda X L, Fernandez-Alonso A, Suarez-Cunqueiro M M: Morphometric study of the greater palatine canal: Cone-beam computed tomography. Surg Radiol Anat 37: 1217–1224 (2015)

Reymond J, Charuta A, Wysocki J: The morphology and morphometry of the foramina of the greater wing of the human sphenoid. Folia Morphol 64: 188–193 (2005)

Rumboldt Z, Castillo M, Smith J K: The palatovagi-nal canal: Can it be identified on routine CT and MR imaging? Am J Rontgenol 179: 267–272 (2002)

Rusu M C, Didilescu A C , Jianu A M, Paduraru D: 3D CBCT anatomy of the pterygopalatine fossa. Surg Radiol Anat 35: 143–159 (2013)

Scanavine A B, Nvarro J A, Megale S R, Anselmo-Lima W T: Anatomical study of the sphenopala-tine foramen. Braz J Otorhinolaryngol 75: 37–41 (2009)

Sepahdari A R, Mong S: Skull base CT: Normative values for size and symmetry of the facial nerve canal, foramen ovale, pterygoid canal, and fora-men rotundum. Surg Radiol Anat 35: 19–24 (2013)

Siddiqui A H, Chen R P: Intracranial collateral anas-tomoses: Relevance to endovascular procedures. Neurosurg Clin N Am 20: 279–296 (2009)

Soto R A, Caceres F, Vera C: Morphometry of the greater palatal canal in adult skulls. J Craniofac Surg 26: 1697–1699 (2015)

Stojcev Stajcic L, Gacic B, Popovic N, Stajcic Z: An-atomical study of the pterygopalatine fossa per-tinent to the maxillary nerve block at the fora-men rotundum. Int J Oral Maxillofac Surg 39: 493–496 (2010)

Takeuchi M, Kuwayama N, Kubo M, Umemura K, Hi-rashima Y, Endo S: Vidian artery as a collateral channel between the external and occluded in-ternal carotid arteries – a case report. Neurol Med Chir (Tokyo) 45: 470–471 (2005)

Tan H K, Ong Y K: Sphenoid sinus: An anatomic and endoscopic study in Asian cadavers. Clin Anat 20: 745–750 (2007)

Tashi S, Purohit B S, Becker M, Mundada P: The pterygopalatine fossa: Imaging anatomy, com-munications, and pathology revisited. Insights Imaging 7: 589–599 (2016)

Tsutsumi S, Ono H, Ishii Hisato, Yasumoto Y: Visual-ization of the vidian canal and nerve using mag-netic resonance imaging. Surg Radiol Anat 40: 1391–1396 (2018)

Tubbs R S, May Wr J R, Apaydin N, Shoja M M, Shok-ouhi G, Loukas M, Cohen-Gadol A A: Ossification of ligaments near the foramen ovale: An ana-tomic study with potential clinical significance regarding transcutaneous approaches to the skull base. Neurosurgery 65: 60–64 (2009)

Unal B, Bademci G, Bilgili Y K, Batay F, Avci E: Risky anatomic variations of sphenoid sinus for sur-gery. Surg Radiol Anat 28: 195–201 (2006)

von Arx T, Lozanoff S: Clinical Oral Anatomy - A Comprehensive Review for Dental Practitioners and Researchers. 1st edition, Springer Interna-tional, Switzerland (2017)

von Arx T, Lozanoff S, Bornstein M M: Extraoral anatomy in CBCT - a literature review. Part 1: Nasoethmoidal region. Swiss Dent J 129: 804–815 (2019)

von Arx T, Lozanoff S, Bornstein M M: Extraoral anatomy in CBCT - a literature review. Part 2: Zygomatico-orbital region. Swiss Dent J 130: 126–138 (2020)

Vuksanovic-Bozaric A, Vukcevic B, Abramovic M, Vukcevic N, Popovic N, Radunovic M: The ptery-gopalatine fossa: morphometric CT study with clinical implications. Surg Radiol Anat 41: 161–168 (2019)

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