A Portrait of Youth in “My Son the Fanatic”, Lecture notes of Art

Download A Portrait of Youth in “My Son the Fanatic” and more Lecture notes Art in PDF only on Docsity! 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. KEYWORDS Anatomy 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 CORRESPONDENCE Prof. Dr. Thomas von Arx Klinik 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: thomas.vonarx@zmk.unibe.ch 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 216-228_T1-1_vonarx_EDF.indd 216 27.02.20 07:22 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 217RESEARCH AND SCIENCE Introduction This 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 bone The 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 body The 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 sella lies 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 clivus represents 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 sinus The 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. 216-228_T1-1_vonarx_EDF.indd 217 27.02.20 07:22 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 220 RESEARCH AND SCIENCE 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 spinosum The 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 216-228_T1-1_vonarx_EDF.indd 220 27.02.20 07:23 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 221RESEARCH AND SCIENCE 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 process The 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 fossa The 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 fissure This 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 216-228_T1-1_vonarx_EDF.indd 221 27.02.20 07:23 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 222 RESEARCH AND SCIENCE A B C ED 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 216-228_T1-1_vonarx_EDF.indd 222 27.02.20 07:23 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 225RESEARCH AND SCIENCE 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 canal The 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 canal The 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. A B C 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 216-228_T1-1_vonarx_EDF.indd 225 27.02.20 07:23 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 226 RESEARCH AND SCIENCE Discussion This 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. Acknowledgement The 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 interest The authors declare that there are no conflicts of interest related to this review. Abbreviations CBCT cone beam computed tomography CN cranial nerve CT computer tomography FOv foramen ovale FSp foramen spinosum ICA internal carotid artery OPC optic canal PC pterygoid canal PPF pterygopalatine fossa PSAA posterior superior alveolar artery PTP pterygoid process PVC palatovaginal canal SPF sphenopalatine foramen SPS sphenoid sinus VVC vomerovaginal canal Zusammenfassung In 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 216-228_T1-1_vonarx_EDF.indd 226 27.02.20 07:23 SWISS DENTAL JOURNAL SSO VOL 130 3 P 2020 227RESEARCH AND SCIENCE 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. Résumé Ce 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. 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