Radiology of the head

Andrew Holloway; Avi Avner

doi:10.22233/9781910443187.8

British Small Animal Veterinary Association , 302 (2013); https://doi.org/10.22233/9781910443187.8

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Radiology of the head

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Authors: Andrew Holloway and Avi Avner
From: BSAVA Manual of Canine and Feline Radiography and Radiology
Item: Chapter 8, pp 302 - 354
DOI: 10.22233/9781910443187.8
Copyright: © 2013 British Small Animal Veterinary Association
Publication Date: January 2013

Abstract

There is little doubt that the cross-sectional imaging modalities of computed tomography (CT), magnetic resonance imaging (MRI) and diagnostic endoscopy are superior to radiography for the assessment of diseases involving the head. The limitations of radiography for imaging the head are that, whilst it is sensitive for detecting some diseases, it is insensitive for detecting others, and when disease is detected the extent of the changes may be underestimated. Despite this, radiography remains a primary diagnostic technique as it is widely available and inexpensive. The skull is a complex bony structure enclosing the brain and the communicating air-containing structures of the nose, nasopharynx, oropharynx and auditory bulae. Surrounding soft tissue structures are limited to the masticatory muscles, salivary glands and supporting muscles of the neck. Therefore, although the skull has high inherent radiographic contrast and can be imaged using an X-ray tube with limited output, the principle challenge is posed by the superimposition and geometric complexity of the bones of the skull. The chapter examines the radiological interpretation of Nasal cavity and frontal sinuses; Cranium and calvarium; Mandible, maxilla and dentition; Temporomandibular joint; Ears and bullae; Larynx and pharynx; Salivary glands; and Hyoid bones.

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Figures

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8.1

(a) Patient positioning for a lateral view. The nose is elevated to keep the sagittal plane parallel to the cassette. Centring depends on the region of interest, but is usually between the orbit and external ear canal. (b) The dorsal margins of the nasal and frontal bones (arrowheads) and the air-filled nasopharynx (*) and frontal sinus (F) are well visualized. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.1 (a) Patient positioning for a lateral view. The nose is elevated to keep the sagittal plane parallel to the cassette. Centring depends on the region of interest, but is usually between the orbit and external ear canal. (b) The dorsal margins of the nasal and frontal bones (arrowheads) and the air-filled nasopharynx (*) and frontal sinus (F) are well visualized. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.2

(a) Patient positioning for a DV view. For deep-chested dogs, the cassette can be elevated and supported on a block. Centring depends on the region of interest, but for survey radiographs it is usually between the eyes. For the bullae, the beam is centred on the horizontal ear canal. (b) On a well positioned radiograph, the maxillary canines, coronoid processes of the mandible and the zygomatic arches should all be symmetrical (arrowed). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.2 (a) Patient positioning for a DV view. For deep-chested dogs, the cassette can be elevated and supported on a block. Centring depends on the region of interest, but for survey radiographs it is usually between the eyes. For the bullae, the beam is centred on the horizontal ear canal. (b) On a well positioned radiograph, the maxillary canines, coronoid processes of the mandible and the zygomatic arches should all be symmetrical (arrowed). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.3

Patient positioning for a VD view. The hard palate must be parallel to the cassette. Supporting the neck and taping the muzzle help stabilize the skull. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.3 Patient positioning for a VD view. The hard palate must be parallel to the cassette. Supporting the neck and taping the muzzle help stabilize the skull. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.4

(a) Patient positioning for a lateral oblique view of the skull. Lateral oblique views are used to assess the frontal sinuses, the bullae and the maxillary and mandibular dental arcades. The skull is rotated axially toward the DV or VD position (approximately 30 degrees) in order to place the region of interest closest to the film. Rotation toward the DV position (shown) is used to evaluate the frontal sinuses and mandibular dentition, whilst rotation toward the VD position is used to assess the tympanic bullae and maxillary dentition. To examine the dental arcades, the jaw is opened. (b) The lateral region of the frontal sinus is projected dorsally (arrowed) and skylined using a lateral oblique view. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.4 (a) Patient positioning for a lateral oblique view of the skull. Lateral oblique views are used to assess the frontal sinuses, the bullae and the maxillary and mandibular dental arcades. The skull is rotated axially toward the DV or VD position (approximately 30 degrees) in order to place the region of interest closest to the film. Rotation toward the DV position (shown) is used to evaluate the frontal sinuses and mandibular dentition, whilst rotation toward the VD position is used to assess the tympanic bullae and maxillary dentition. To examine the dental arcades, the jaw is opened. (b) The lateral region of the frontal sinus is projected dorsally (arrowed) and skylined using a lateral oblique view. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.5

(a) Patient positioning for a rostrocaudal view of the frontal sinuses and calvarium. On this view, the frontal sinuses are projected above the nose and remainder of the calvarium. (b) The zygomatic arches (arrowheads), frontal sinuses (white arrows) and coronoid processes (C) of the mandible can be assessed. The orbital ligament is occasionally recognized as a dense opaque structure, extending between the zygomatic arch and frontal bone (black arrows). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.5 (a) Patient positioning for a rostrocaudal view of the frontal sinuses and calvarium. On this view, the frontal sinuses are projected above the nose and remainder of the calvarium. (b) The zygomatic arches (arrowheads), frontal sinuses (white arrows) and coronoid processes (C) of the mandible can be assessed. The orbital ligament is occasionally recognized as a dense opaque structure, extending between the zygomatic arch and frontal bone (black arrows). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.6

(a) Patient positioning for a DV intraoral view of the nasal chambers. The flexible cassette must be placed in the mouth as far caudally as possible. (b) Dental and nasal structures should be symmetrical and the cribriform plate (arrowheads) included on the film. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.6 (a) Patient positioning for a DV intraoral view of the nasal chambers. The flexible cassette must be placed in the mouth as far caudally as possible. (b) Dental and nasal structures should be symmetrical and the cribriform plate (arrowheads) included on the film. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.7

(a) Patient positioning for a VD intraoral view of the mandible. The plate is advanced as far caudally as possible whilst avoiding rotation. (b) The mandibular rami and arcades should be symmetrical. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.7 (a) Patient positioning for a VD intraoral view of the mandible. The plate is advanced as far caudally as possible whilst avoiding rotation. (b) The mandibular rami and arcades should be symmetrical. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.8

Normal skull anatomy of the dog. (a) Lateral view. 1 = incisive bone; 2 = hard palate (maxilla); 3 = nasal bone; 4 = frontal bone and sinuses; 5 = external occipital protuberance (calvarium); 6 = cranial vault; 7 = tympanic bullae; 8 = cribriform plate; 9 = ethmoturbinates; 10 = nasal (or maxillary) turbinates; 11 = body of the mandible; 12 = temporomandibular joint; 13 = soft palate; 14 = oropharynx; 15 = pharynx and hyoid bone. (b) VD view. 1 = maxillary teeth; 2 = zygomatic arch; 3 = coronoid process of the mandible; 4 = condyloid process of the mandible; 5 = tympanic bulla; 6 = frontal sinus; 7 = vomer; 8 = external occipital protuberance; 9 = body of the mandible; 10 = ramus of the mandible; 11 = nasal cavity (obscured rostrally by mandible). © 2013 British Small Animal Veterinary Association

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8.8 Normal skull anatomy of the dog. (a) Lateral view. 1 = incisive bone; 2 = hard palate (maxilla); 3 = nasal bone; 4 = frontal bone and sinuses; 5 = external occipital protuberance (calvarium); 6 = cranial vault; 7 = tympanic bullae; 8 = cribriform plate; 9 = ethmoturbinates; 10 = nasal (or maxillary) turbinates; 11 = body of the mandible; 12 = temporomandibular joint; 13 = soft palate; 14 = oropharynx; 15 = pharynx and hyoid bone. (b) VD view. 1 = maxillary teeth; 2 = zygomatic arch; 3 = coronoid process of the mandible; 4 = condyloid process of the mandible; 5 = tympanic bulla; 6 = frontal sinus; 7 = vomer; 8 = external occipital protuberance; 9 = body of the mandible; 10 = ramus of the mandible; 11 = nasal cavity (obscured rostrally by mandible).

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8.9

Lateral radiographs showing (a) dolichocephalic, (b) mesaticephalic and (c) brachycephalic skull conformation in the dog. Note that the facial length (red arrows) is markedly reduced in brachycephalic breeds compared with the length of the calvarium (yellow arrows). © 2013 British Small Animal Veterinary Association

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8.9 Lateral radiographs showing (a) dolichocephalic, (b) mesaticephalic and (c) brachycephalic skull conformation in the dog. Note that the facial length (red arrows) is markedly reduced in brachycephalic breeds compared with the length of the calvarium (yellow arrows).

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8.10

DV view showing the anatomy of the nose. The arrowheads denote the cribriform plate. 1 = nares; 2 = palatine fissure; 3 = maxilloturbinates; 4 = ethmoturbinates; 5 = vomer; 6 = maxillary recess; 7 = frontal sinus (medial recess). © 2013 British Small Animal Veterinary Association

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8.10 DV view showing the anatomy of the nose. The arrowheads denote the cribriform plate. 1 = nares; 2 = palatine fissure; 3 = maxilloturbinates; 4 = ethmoturbinates; 5 = vomer; 6 = maxillary recess; 7 = frontal sinus (medial recess).

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8.11

Bones of the skull. 1 = incisive; 2 = nasal; 3 = maxilla; 4 = frontal; 5 = parietal; 6 = occipital; 7 = temporal; 8 = sphenoid; 9 = palatine; 10 = lacrimal; 11 = pterygoid. © 2013 British Small Animal Veterinary Association

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8.11 Bones of the skull. 1 = incisive; 2 = nasal; 3 = maxilla; 4 = frontal; 5 = parietal; 6 = occipital; 7 = temporal; 8 = sphenoid; 9 = palatine; 10 = lacrimal; 11 = pterygoid.

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8.12

Normal anatomy of the calvarium. (a) Lateral view. 1 = parietal bone; 2 = external occipital protuberance; 3 = occipital bone (basal); 4 = occipital condyle; 5 = atlas; 6 = zygomatic arch; 7 = cribriform plate; 8 = cranial vault. (b) DV view. 1 = mandibular fossa; 2 = zygomatic arch; 3 = maxilla; 4 = vomer; 5 = frontal sinus; 6 = body of the mandible; 7 = coronoid process of the mandible; 8 = condyloid process of the mandible; 9 = tympanic bulla; 10 = occipital condyle; 11 = mastoid process; 12 = paracondylar process. © 2013 British Small Animal Veterinary Association

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8.12 Normal anatomy of the calvarium. (a) Lateral view. 1 = parietal bone; 2 = external occipital protuberance; 3 = occipital bone (basal); 4 = occipital condyle; 5 = atlas; 6 = zygomatic arch; 7 = cribriform plate; 8 = cranial vault. (b) DV view. 1 = mandibular fossa; 2 = zygomatic arch; 3 = maxilla; 4 = vomer; 5 = frontal sinus; 6 = body of the mandible; 7 = coronoid process of the mandible; 8 = condyloid process of the mandible; 9 = tympanic bulla; 10 = occipital condyle; 11 = mastoid process; 12 = paracondylar process.

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8.13

Lateral view of the skull of a dentally immature dog. Both deciduous (arrowheads) and (unerupted) permanent (arrowed) teeth are visible. The permanent teeth lie beneath the deciduous teeth. In the permanent teeth, the pulp cavity is wide (*) and the dentine walls are thin. Once the tooth apices of the erupted permanent teeth have formed, the animal is considered dentally mature. © 2013 British Small Animal Veterinary Association

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8.13 Lateral view of the skull of a dentally immature dog. Both deciduous (arrowheads) and (unerupted) permanent (arrowed) teeth are visible. The permanent teeth lie beneath the deciduous teeth. In the permanent teeth, the pulp cavity is wide (*) and the dentine walls are thin. Once the tooth apices of the erupted permanent teeth have formed, the animal is considered dentally mature.

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8.14

Lateral oblique view of the normal second and third maxillary premolar teeth using an extraoral parallel technique. Each tooth has two roots surrounded by the thin, dense cortical bone of the lamina dura (white arrows). The lamina dura is separated from the tooth root by the radiolucent periodontal ligament. The apex of the tooth root is closed (black arrow). The pulp cavity (*) is narrowed in the mature dog. F = furcation; I = interdental space. © 2013 British Small Animal Veterinary Association

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8.14 Lateral oblique view of the normal second and third maxillary premolar teeth using an extraoral parallel technique. Each tooth has two roots surrounded by the thin, dense cortical bone of the lamina dura (white arrows). The lamina dura is separated from the tooth root by the radiolucent periodontal ligament. The apex of the tooth root is closed (black arrow). The pulp cavity (*) is narrowed in the mature dog. F = furcation; I = interdental space.

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8.15

Lateral view of the mandible (bone specimen). 1 = mental foramen; 2 = mandibular body; 3 = mandibular ramus; 4 = coronoid process; 5 = condyloid process; 6 = angular process. © 2013 British Small Animal Veterinary Association

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8.15 Lateral view of the mandible (bone specimen). 1 = mental foramen; 2 = mandibular body; 3 = mandibular ramus; 4 = coronoid process; 5 = condyloid process; 6 = angular process.

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8.16

DV view of the premaxilla. The trabeculation of the premaxilla has a coarse and foamy appearance. The lateral margins of the rostral vomer bone (arrowed) and paired palatine fissures can be seen. The modified Triadan numbering system is shown for the right premaxilla and maxilla, and conventional numbering is shown for the left premaxilla and maxilla. N = nares. © 2013 British Small Animal Veterinary Association

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8.16 DV view of the premaxilla. The trabeculation of the premaxilla has a coarse and foamy appearance. The lateral margins of the rostral vomer bone (arrowed) and paired palatine fissures can be seen. The modified Triadan numbering system is shown for the right premaxilla and maxilla, and conventional numbering is shown for the left premaxilla and maxilla. N = nares.

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8.17

Temporomandibular joint of a cat. The C-shaped mandibular fossa (CF) and the condyloid process (CP) form the temporomandibular joint. The retroarticular process (R) prevents caudal displacement of the condyloid process. The opposite temporomandibular joint is projected dorsally (*). © 2013 British Small Animal Veterinary Association

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8.17 Temporomandibular joint of a cat. The C-shaped mandibular fossa (CF) and the condyloid process (CP) form the temporomandibular joint. The retroarticular process (R) prevents caudal displacement of the condyloid process. The opposite temporomandibular joint is projected dorsally (*).

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8.18

DV view of the skull showing the normal anatomy of the tympanic bulla. The external ear canals are filled with air (white arrows). The bony bullae (black arrows) are superimposed on the dense petrous temporal bone. © 2013 British Small Animal Veterinary Association

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8.18 DV view of the skull showing the normal anatomy of the tympanic bulla. The external ear canals are filled with air (white arrows). The bony bullae (black arrows) are superimposed on the dense petrous temporal bone.

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8.19

Lateral view of the pharynx and larynx. The dorsal margin of the nasopharynx is denoted by arrowheads. B = basihyoid; C = cricoid cartilage; Ce = ceratohyoid; Ch = choane; E = epihyoid; Eg = epiglottis; S = stylohyoid; SP = soft palate; T = thyroid cartilage; Th = thyrohyoid. © 2013 British Small Animal Veterinary Association

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8.19 Lateral view of the pharynx and larynx. The dorsal margin of the nasopharynx is denoted by arrowheads. B = basihyoid; C = cricoid cartilage; Ce = ceratohyoid; Ch = choane; E = epihyoid; Eg = epiglottis; S = stylohyoid; SP = soft palate; T = thyroid cartilage; Th = thyrohyoid.

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8.20

Brachycephalic skull. (a) Lateral view. 1 = nasal planum; 2 = facial folds; 3 = frontal sinuses markedly attenuated or absent; 4 = nasal chambers – attenuated; 5 = dome-shaped calvarium; 6 = hypoplastic tympanic bullae; 7 = short maxilla (and hard palate); 8 = thickened soft palate; 9 = narrowed nasopharynx; 10 = thickened retropharyngeal soft tissues; 11 = crowded mandibular dentition. (b) DV view. The wide mandible is denoted by the arrow. 12 = crowded maxillary dentition; 13 = bullae. © 2013 British Small Animal Veterinary Association

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8.20 Brachycephalic skull. (a) Lateral view. 1 = nasal planum; 2 = facial folds; 3 = frontal sinuses markedly attenuated or absent; 4 = nasal chambers – attenuated; 5 = dome-shaped calvarium; 6 = hypoplastic tympanic bullae; 7 = short maxilla (and hard palate); 8 = thickened soft palate; 9 = narrowed nasopharynx; 10 = thickened retropharyngeal soft tissues; 11 = crowded mandibular dentition. (b) DV view. The wide mandible is denoted by the arrow. 12 = crowded maxillary dentition; 13 = bullae.

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8.21

Normal skull anatomy of the cat. (a) Lateral view. The nasal bone is curved and the tympanic bullae are large and project ventrally. 1 = ethmoturbinates; 2 = frontal sinuses; 3 = tentorium cerebelli ossium; 4 = tympanic bullae; 5 = calvarium; 6 = mandible with widened interdental space; 7 = sagittal crest less prominent. (b) DV view. F = frontal sinus; P = postorbital process; S = sphenoidal sinus. (c) Brachycephalic skull. Note the reduced facial length and extreme mandibular prognathism. © 2013 British Small Animal Veterinary Association

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8.21 Normal skull anatomy of the cat. (a) Lateral view. The nasal bone is curved and the tympanic bullae are large and project ventrally. 1 = ethmoturbinates; 2 = frontal sinuses; 3 = tentorium cerebelli ossium; 4 = tympanic bullae; 5 = calvarium; 6 = mandible with widened interdental space; 7 = sagittal crest less prominent. (b) DV view. F = frontal sinus; P = postorbital process; S = sphenoidal sinus. (c) Brachycephalic skull. Note the reduced facial length and extreme mandibular prognathism.

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8.22

Röntgen sign: size. (a) Lateral oblique and (b) rostrocaudal views of the skull of a cat with facial swelling. (a) There is dome-shaped enlargement of the frontal bones (arrowed). The sinus still appears air-filled but the frontal sinuses are better skylined on the rostrocaudal view. (b) The swelling is a focal expansion of the lateral recess of the left frontal sinus (arrowed). The cortices of the frontal sinus are intact and the sinus is air-filled. These changes are typical of a benign process. POP = postorbital process. (Courtesy of A Dupuy, Mandeville Veterinary Hospital) © 2013 British Small Animal Veterinary Association

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8.22 Röntgen sign: size. (a) Lateral oblique and (b) rostrocaudal views of the skull of a cat with facial swelling. (a) There is dome-shaped enlargement of the frontal bones (arrowed). The sinus still appears air-filled but the frontal sinuses are better skylined on the rostrocaudal view. (b) The swelling is a focal expansion of the lateral recess of the left frontal sinus (arrowed). The cortices of the frontal sinus are intact and the sinus is air-filled. These changes are typical of a benign process. POP = postorbital process. (Courtesy of A Dupuy, Mandeville Veterinary Hospital)

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8.23

Röntgen sign: size. Rostrocaudal view of the skull of a dog with swelling around the left orbit. The frontal sinuses are skylined and the zygomatic process of the left frontal bone (arrowed) is thickened and sclerotic. Further thick crescentic organized new bone extends ventrally along the dorsal orbit and parietal bones (arrowhead). The changes are non-destructive, chronic and relatively organized, consistent with a low-grade (bacterial) osteitis. © 2013 British Small Animal Veterinary Association

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8.23 Röntgen sign: size. Rostrocaudal view of the skull of a dog with swelling around the left orbit. The frontal sinuses are skylined and the zygomatic process of the left frontal bone (arrowed) is thickened and sclerotic. Further thick crescentic organized new bone extends ventrally along the dorsal orbit and parietal bones (arrowhead). The changes are non-destructive, chronic and relatively organized, consistent with a low-grade (bacterial) osteitis.

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8.24

Röntgen sign: shape. DV view showing fracture of the left zygomatic arch (arrowed). Displacement and altered contour are easily overlooked if the lateral view is relied upon alone. © 2013 British Small Animal Veterinary Association

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8.24 Röntgen sign: shape. DV view showing fracture of the left zygomatic arch (arrowed). Displacement and altered contour are easily overlooked if the lateral view is relied upon alone.

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8.25

Röntgen sign: number. All skull bones and teeth should be paired and symmetrical. Occasionally, additional structures, usually (supernumerary) teeth, as in this dog with an extra pair of incisors, (arrowed) are recognized. However, the absence of one of a paired structure is usually a more important finding, indicating destruction or displacement of the structure. © 2013 British Small Animal Veterinary Association

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8.25 Röntgen sign: number. All skull bones and teeth should be paired and symmetrical. Occasionally, additional structures, usually (supernumerary) teeth, as in this dog with an extra pair of incisors, (arrowed) are recognized. However, the absence of one of a paired structure is usually a more important finding, indicating destruction or displacement of the structure.

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8.26

Röntgen sign: opacity. (a) The gas opacity of the caudal part of the frontal sinus has been replaced by a subtle, rounded soft tissue opacity bulging into the sinus. (b) Centring the beam on the lesion demonstrates an extensive destructive calvarial mass (arrowheads) breaking into the frontal sinus (arrowed). © 2013 British Small Animal Veterinary Association

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8.26 Röntgen sign: opacity. (a) The gas opacity of the caudal part of the frontal sinus has been replaced by a subtle, rounded soft tissue opacity bulging into the sinus. (b) Centring the beam on the lesion demonstrates an extensive destructive calvarial mass (arrowheads) breaking into the frontal sinus (arrowed).

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8.27

Röntgen sign: margination. DV intraoral nasal radiographs of two dogs presented with sneezing and epistaxis. (a) The rostral nasal turbinates on the right (arrowhead) are blurred and indistinct due to inflammation and the accumulation of fluid as a result of a nasal foreign body (grass seed). (b) The thin line of cortical bone demarcating the right maxillary recess is indistinct (arrowhead). Compared with the normal air-filled left maxillary recess (white arrow), the right maxillary recess is of increased soft tissue opacity. The ethmoturbinates medial to the right maxillary recess are blurred. In addition, a poorly circumscribed area of lysis surrounds the mesial root of the fourth maxillary premolar (black arrow). The changes are subtle, but by assessing the margins the presence of bone destruction can be confirmed, although the extent cannot be determined from the radiograph. On MRI, a maxillary mass that had eroded into the right nasal chamber was visible. © 2013 British Small Animal Veterinary Association

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8.27 Röntgen sign: margination. DV intraoral nasal radiographs of two dogs presented with sneezing and epistaxis. (a) The rostral nasal turbinates on the right (arrowhead) are blurred and indistinct due to inflammation and the accumulation of fluid as a result of a nasal foreign body (grass seed). (b) The thin line of cortical bone demarcating the right maxillary recess is indistinct (arrowhead). Compared with the normal air-filled left maxillary recess (white arrow), the right maxillary recess is of increased soft tissue opacity. The ethmoturbinates medial to the right maxillary recess are blurred. In addition, a poorly circumscribed area of lysis surrounds the mesial root of the fourth maxillary premolar (black arrow). The changes are subtle, but by assessing the margins the presence of bone destruction can be confirmed, although the extent cannot be determined from the radiograph. On MRI, a maxillary mass that had eroded into the right nasal chamber was visible.

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8.28

Röntgen sign: location. VD intraoral radiograph of a dog with an aggressive soft tissue mass (squamous cell carcinoma) invading the rostral mandible (arrowheads). Multiple mandibular premolars (*) on both the left and right have been displaced by the mass. Note the extensive lysis of both hemimandibles and the irregular, somewhat spiculated periosteal reaction on the medial aspect of the right hemimandible. Involvement of both hemimandibles is more typical of a soft tissue tumour invading bone; it is unusual for a mass arising from one hemimandible to involve the contralateral hemimandible. © 2013 British Small Animal Veterinary Association

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8.28 Röntgen sign: location. VD intraoral radiograph of a dog with an aggressive soft tissue mass (squamous cell carcinoma) invading the rostral mandible (arrowheads). Multiple mandibular premolars (*) on both the left and right have been displaced by the mass. Note the extensive lysis of both hemimandibles and the irregular, somewhat spiculated periosteal reaction on the medial aspect of the right hemimandible. Involvement of both hemimandibles is more typical of a soft tissue tumour invading bone; it is unusual for a mass arising from one hemimandible to involve the contralateral hemimandible.

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8.29

Open-mouth V20°R-DCdO view. (a) Patient positioning. The X-ray beam should be parallel to the long axis of the mandible. The most common error is that the jaw is not opened sufficiently. (b) This view is used to assess the caudal aspect of the nasal chambers, maxilla and the cribriform plate (arrowheads). The tongue (T) and endotracheal tube must be secured so that they are not superimposed on the nasal chambers. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.29 Open-mouth V20°R-DCdO view. (a) Patient positioning. The X-ray beam should be parallel to the long axis of the mandible. The most common error is that the jaw is not opened sufficiently. (b) This view is used to assess the caudal aspect of the nasal chambers, maxilla and the cribriform plate (arrowheads). The tongue (T) and endotracheal tube must be secured so that they are not superimposed on the nasal chambers. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.30

V30°Cd-DRO view. The wide angle of the caudal mandible allows the caudal aspect of the nasal chambers (*), the cribriform plate (arrowed) and lateral recesses of the frontal sinuses (F) to be assessed. The temporomandibular joints are also well demonstrated. © 2013 British Small Animal Veterinary Association

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8.30 V30°Cd-DRO view. The wide angle of the caudal mandible allows the caudal aspect of the nasal chambers (*), the cribriform plate (arrowed) and lateral recesses of the frontal sinuses (F) to be assessed. The temporomandibular joints are also well demonstrated.

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8.31

(a) Patient positioning for a caudorostral view of the frontal sinuses. The head must be elevated. As a horizontal beam is used, fluid levels may be recognized. (b) Depression fracture (arrowed) of the lateral recess of the frontal sinus. Note the region in which the orbital ligament may be recognized (arrowheads). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.31 (a) Patient positioning for a caudorostral view of the frontal sinuses. The head must be elevated. As a horizontal beam is used, fluid levels may be recognized. (b) Depression fracture (arrowed) of the lateral recess of the frontal sinus. Note the region in which the orbital ligament may be recognized (arrowheads). Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.32

(a) DV intraoral view of the nose of a dog with epistaxis due to a nasal carcinoma. A poorly defined soft tissue mass (white arrows) fills the mid and caudal left nasal chamber. Turbinates are not recognized within this area. Bone destruction of the maxilla is not present. The vomer is thinned caudally (black arrow). The maxillary recess is filled with a soft tissue opacity, but the thin bony medial wall is still intact (arrowhead). Note that the rostral turbinates (*) are blurred, probably due to the accumulation of secretions, but still intact. (b) In this dog, the mass (arrowed) fills most of the right nasal chamber, including the maxillary recess (*), but also extends across the midline to fill the middle region of the left nasal chamber. (c) In this dog, there is extension into the calvarium. There is lysis of the bony margin of the rostral calvarium and cribriform plate (arrowed). The frontal sinus (*) is filled with a mass or fluid. (d) Nasal lymphoma in a cat. The right nasal chamber is completely filled with a homogeneous soft tissue mass (*). The turbinates are not recognized. The bony margins are intact. © 2013 British Small Animal Veterinary Association

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8.32 (a) DV intraoral view of the nose of a dog with epistaxis due to a nasal carcinoma. A poorly defined soft tissue mass (white arrows) fills the mid and caudal left nasal chamber. Turbinates are not recognized within this area. Bone destruction of the maxilla is not present. The vomer is thinned caudally (black arrow). The maxillary recess is filled with a soft tissue opacity, but the thin bony medial wall is still intact (arrowhead). Note that the rostral turbinates (*) are blurred, probably due to the accumulation of secretions, but still intact. (b) In this dog, the mass (arrowed) fills most of the right nasal chamber, including the maxillary recess (*), but also extends across the midline to fill the middle region of the left nasal chamber. (c) In this dog, there is extension into the calvarium. There is lysis of the bony margin of the rostral calvarium and cribriform plate (arrowed). The frontal sinus (*) is filled with a mass or fluid. (d) Nasal lymphoma in a cat. The right nasal chamber is completely filled with a homogeneous soft tissue mass (*). The turbinates are not recognized. The bony margins are intact.

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8.33

Frontal sinus tumour in a dog. The soft tissue mass filling the frontal sinus has expanded and thinned the frontal bone (arrowheads). The mass extends rostrally within the soft tissues (*) dorsal to the frontal sinus and into the caudal nasal chambers. © 2013 British Small Animal Veterinary Association

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8.33 Frontal sinus tumour in a dog. The soft tissue mass filling the frontal sinus has expanded and thinned the frontal bone (arrowheads). The mass extends rostrally within the soft tissues (*) dorsal to the frontal sinus and into the caudal nasal chambers.

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8.34

(a) DV intraoral, (b) lateral and (c) rostrocaudal (skyline) views of the nasal chambers of a dog with destructive rhinitis due to nasal aspergillosis. (a) There is unilateral destruction of turbinates in the rostral (black arrowheads) and caudal (arrowed) left nasal chamber. The left nasal chamber is reduced in opacity (more air; fewer turbinates) compared with the right side. The amorphous soft tissue opacity in the caudal nasal chamber and superimposed on the maxillary recess represents accumulated discharge and debris. The degree of involvement of the right nasal chamber cannot be established based on radiographs alone. (b) At least one of the frontal sinuses is filled with material of soft tissue opacity (black arrowheads). The dorsal aspect of at least one of the frontal bones is thickened with a prominent lamellar periosteal reaction recognized in profile (arrowed). (c) On the skyline view, both frontal sinuses are recognized to be affected. The left sinus is almost completely opacified (*) and the right sinus is partially affected but with a marked reaction and thickening of the frontal bone (arrowed) due to fungal osteomyelitis. © 2013 British Small Animal Veterinary Association

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8.34 (a) DV intraoral, (b) lateral and (c) rostrocaudal (skyline) views of the nasal chambers of a dog with destructive rhinitis due to nasal aspergillosis. (a) There is unilateral destruction of turbinates in the rostral (black arrowheads) and caudal (arrowed) left nasal chamber. The left nasal chamber is reduced in opacity (more air; fewer turbinates) compared with the right side. The amorphous soft tissue opacity in the caudal nasal chamber and superimposed on the maxillary recess represents accumulated discharge and debris. The degree of involvement of the right nasal chamber cannot be established based on radiographs alone. (b) At least one of the frontal sinuses is filled with material of soft tissue opacity (black arrowheads). The dorsal aspect of at least one of the frontal bones is thickened with a prominent lamellar periosteal reaction recognized in profile (arrowed). (c) On the skyline view, both frontal sinuses are recognized to be affected. The left sinus is almost completely opacified (*) and the right sinus is partially affected but with a marked reaction and thickening of the frontal bone (arrowed) due to fungal osteomyelitis.

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8.35

DV intraoral view of the nasal chambers of a dog presented with sneezing and discharge from the right naris. There is a focal area of soft tissue opacity (arrowed) in the right rostral nasal chamber, medial to the right maxillary canine, obscuring the turbinates. Gross destruction cannot be recognized. The rostral location, focal changes, young age and unilateral location are suggestive of an inhaled foreign body. A grass seed was retrieved at rhinoscopy. © 2013 British Small Animal Veterinary Association

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8.35 DV intraoral view of the nasal chambers of a dog presented with sneezing and discharge from the right naris. There is a focal area of soft tissue opacity (arrowed) in the right rostral nasal chamber, medial to the right maxillary canine, obscuring the turbinates. Gross destruction cannot be recognized. The rostral location, focal changes, young age and unilateral location are suggestive of an inhaled foreign body. A grass seed was retrieved at rhinoscopy.

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8.36

DV intraoral view of the nose of a cat with chronic rhinitis. The right nasal turbinates are indistinct due to irregular foci of soft tissue opacity (arrowed). The areas are not confluent. The deviation and variable thickness of the vomer is not uncommon in the cat. © 2013 British Small Animal Veterinary Association

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8.36 DV intraoral view of the nose of a cat with chronic rhinitis. The right nasal turbinates are indistinct due to irregular foci of soft tissue opacity (arrowed). The areas are not confluent. The deviation and variable thickness of the vomer is not uncommon in the cat.

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8.37

Lateral view of the skull of a young dog with hydrocephalus. The cranium is enlarged, rounded and dome-shaped with thinning of the calvarial bones (arrowed). Note that the calvarium has a smooth internal appearance (*) and lacks the normal groove-like markings. © 2013 British Small Animal Veterinary Association

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8.37 Lateral view of the skull of a young dog with hydrocephalus. The cranium is enlarged, rounded and dome-shaped with thinning of the calvarial bones (arrowed). Note that the calvarium has a smooth internal appearance (*) and lacks the normal groove-like markings.

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8.38

(a) Lateral and (b) DV views of the skull of a dog following vehicular trauma. Fracture of the frontal sinus is present. (a) A cortical defect is present in one of the frontal bones adjacent to the calvarium (white arrow). Multiple depressed fracture fragments (black arrows) are superimposed on the sinus. (b) On the DV view, the lateral aspect of the frontal sinus is partially obscured by the coronoid process of the mandible. Although the defect in the lateral wall can be recognized (white arrows) the full extent is not appreciated. A displaced bone fragment is seen end-on (arrowhead). Subcutaneous emphysema is present (black arrow). Skyline radiographs of the frontal sinus would be useful in this animal. © 2013 British Small Animal Veterinary Association

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8.38 (a) Lateral and (b) DV views of the skull of a dog following vehicular trauma. Fracture of the frontal sinus is present. (a) A cortical defect is present in one of the frontal bones adjacent to the calvarium (white arrow). Multiple depressed fracture fragments (black arrows) are superimposed on the sinus. (b) On the DV view, the lateral aspect of the frontal sinus is partially obscured by the coronoid process of the mandible. Although the defect in the lateral wall can be recognized (white arrows) the full extent is not appreciated. A displaced bone fragment is seen end-on (arrowhead). Subcutaneous emphysema is present (black arrow). Skyline radiographs of the frontal sinus would be useful in this animal.

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8.39

DV view of the skull of a 4-month-old dog following trauma. A comminuted fracture of the left zygomatic arch is present. The fragments (arrowheads) are displaced. The temporal process of the arch is also displaced at the suture with the maxilla (arrowed). Failure to recognize displaced zygomatic bone fractures can lead to difficulties in mastication, which are delayed in onset. This is due to callus interfering with movement of the coronoid process, development of false anklyosis or degenerative joint disease of the temporomandibular joint. © 2013 British Small Animal Veterinary Association

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8.39 DV view of the skull of a 4-month-old dog following trauma. A comminuted fracture of the left zygomatic arch is present. The fragments (arrowheads) are displaced. The temporal process of the arch is also displaced at the suture with the maxilla (arrowed). Failure to recognize displaced zygomatic bone fractures can lead to difficulties in mastication, which are delayed in onset. This is due to callus interfering with movement of the coronoid process, development of false anklyosis or degenerative joint disease of the temporomandibular joint.

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8.40

Lateral view of the skull of a dog that had been kicked by a horse. Several lucent lines (arrowed) radiate from dorsal to ventral from an area of the calvarium just caudal to the frontal sinuses. Note that the fracture lines widen ventrally. The frontal sinus (*) is partly filled with a soft tissue opacity (haemorrhage). © 2013 British Small Animal Veterinary Association

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8.40 Lateral view of the skull of a dog that had been kicked by a horse. Several lucent lines (arrowed) radiate from dorsal to ventral from an area of the calvarium just caudal to the frontal sinuses. Note that the fracture lines widen ventrally. The frontal sinus (*) is partly filled with a soft tissue opacity (haemorrhage).

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8.41

Lateral view of the skull of a dog with a swelling on the head. An expansile, thin-walled swelling (arrowed) arising from the dorsocaudal aspect of the frontal bone is visible. The transition to normal bone at the periphery is short and smooth new bone, consistent with a Codman’s triangle, is present at the margin, indicating elevated periosteum (*). Internally there is ill defined mineralization. Considering the history of known trauma, the appearance is consistent with a subperiosteal haematoma. © 2013 British Small Animal Veterinary Association

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8.41 Lateral view of the skull of a dog with a swelling on the head. An expansile, thin-walled swelling (arrowed) arising from the dorsocaudal aspect of the frontal bone is visible. The transition to normal bone at the periphery is short and smooth new bone, consistent with a Codman’s triangle, is present at the margin, indicating elevated periosteum (*). Internally there is ill defined mineralization. Considering the history of known trauma, the appearance is consistent with a subperiosteal haematoma.

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8.42

Open-mouth lateral oblique view of the mandible of a 6-month-old dog presented with difficulties opening its mouth. A fracture of the body of the right mandible had been repaired with an external fixator at 3 months of age. The fracture has healed but there is abnormal angulation of the bodies of both hemimandibles (arrowheads). Note the dental abnormalities: absent teeth, crown fractures, retained root (double-headed arrow) and malalignment of the fourth mandibular premolar as a result of the trauma. © 2013 British Small Animal Veterinary Association

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8.42 Open-mouth lateral oblique view of the mandible of a 6-month-old dog presented with difficulties opening its mouth. A fracture of the body of the right mandible had been repaired with an external fixator at 3 months of age. The fracture has healed but there is abnormal angulation of the bodies of both hemimandibles (arrowheads). Note the dental abnormalities: absent teeth, crown fractures, retained root (double-headed arrow) and malalignment of the fourth mandibular premolar as a result of the trauma.

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8.43

(a) Lateral and (b) DV views of the skull of a dog with a chronic non-healing fracture of the right zygomatic arch. Gas is present in the soft tissues (sinus tract). An attempt has been made to stabilize the fracture using cerclage wire; however, the central fragment of the comminuted zygomatic fracture has not healed. (a) Assessment on the lateral view is limited to recognizing the fracture line (arrowed) and the irregular margin of the rostral aspect of the zygomatic bone. (b) On the DV view, the fragment (arrowed) is seen to be displaced medially. The fragment is probably non-viable (sequestrum). The discomfort and inability to open the mouth was due to the fibrous callus along the medial zygomatic arch (*), which restricted movement of the coronoid process. The fibrous callus cannot be recognized on radiography but was visible on MRI. © 2013 British Small Animal Veterinary Association

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8.43 (a) Lateral and (b) DV views of the skull of a dog with a chronic non-healing fracture of the right zygomatic arch. Gas is present in the soft tissues (sinus tract). An attempt has been made to stabilize the fracture using cerclage wire; however, the central fragment of the comminuted zygomatic fracture has not healed. (a) Assessment on the lateral view is limited to recognizing the fracture line (arrowed) and the irregular margin of the rostral aspect of the zygomatic bone. (b) On the DV view, the fragment (arrowed) is seen to be displaced medially. The fragment is probably non-viable (sequestrum). The discomfort and inability to open the mouth was due to the fibrous callus along the medial zygomatic arch (*), which restricted movement of the coronoid process. The fibrous callus cannot be recognized on radiography but was visible on MRI.

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8.44

Lateral views of the skulls of two dogs with osteochondrosarcoma. (a) The large mass is egg-shaped and contains fine mineralization (arrowed). It has expanded, creating a large cortical defect extending rostrally into the caudal frontal sinuses, ventrally into the calvarium, dorsally into the soft tissues and caudally into the parietal and occipital bones. There is no periosteal reaction: the bone at the margins is rarefied (arrowhead), consistent with the slow growth of the mass. The dog presented with neurological signs and the mass was not palpable. (b) The mass is rounded with a typical granular, densely mineralized appearance (white arrows). The destruction of the calvarium is indistinct (black arrows) and the mass extends into the calvarium (*). © 2013 British Small Animal Veterinary Association

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8.44 Lateral views of the skulls of two dogs with osteochondrosarcoma. (a) The large mass is egg-shaped and contains fine mineralization (arrowed). It has expanded, creating a large cortical defect extending rostrally into the caudal frontal sinuses, ventrally into the calvarium, dorsally into the soft tissues and caudally into the parietal and occipital bones. There is no periosteal reaction: the bone at the margins is rarefied (arrowhead), consistent with the slow growth of the mass. The dog presented with neurological signs and the mass was not palpable. (b) The mass is rounded with a typical granular, densely mineralized appearance (white arrows). The destruction of the calvarium is indistinct (black arrows) and the mass extends into the calvarium (*).

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8.45

(a) Lateral and (b) VD views of the skull of a young dog with an osteoma. Note the smoothly marginated oval mass (arrowed) arising from the caudal aspect of the temporal process of the right zygoma. The mineralized mass is dense and homogeneous in appearance. © 2013 British Small Animal Veterinary Association

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8.45 (a) Lateral and (b) VD views of the skull of a young dog with an osteoma. Note the smoothly marginated oval mass (arrowed) arising from the caudal aspect of the temporal process of the right zygoma. The mineralized mass is dense and homogeneous in appearance.

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8.46

Renal secondary hyperparathyroidism. (a) Lateral, (b) DV intraoral and (c) open-mouth lateral oblique radiographs of the skull. There is severe demineralization of the skull, resulting in loss of the alveolar bone surrounding the teeth and poor contrast between the bone and soft tissue. The teeth appear to ‘float’ within the soft tissues (white arrows). The changes are consistent with fibrous osteodystrophy. The demineralized bone is replaced by thickened fibrous tissue (black arrow) and within the nasal chambers this restricts the turbinates and airflow. The changes are more dramatic in young animals as a result of the more rapid turnover of bone. © 2013 British Small Animal Veterinary Association

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8.46 Renal secondary hyperparathyroidism. (a) Lateral, (b) DV intraoral and (c) open-mouth lateral oblique radiographs of the skull. There is severe demineralization of the skull, resulting in loss of the alveolar bone surrounding the teeth and poor contrast between the bone and soft tissue. The teeth appear to ‘float’ within the soft tissues (white arrows). The changes are consistent with fibrous osteodystrophy. The demineralized bone is replaced by thickened fibrous tissue (black arrow) and within the nasal chambers this restricts the turbinates and airflow. The changes are more dramatic in young animals as a result of the more rapid turnover of bone.

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8.47

Orbital disease. (a) DV view of the skull of a cat with exophthalmos of the left eye and facial swelling. Clinical assessment often underestimates the extent of facial swelling as in this cat, which has a mass that has replaced most of the rostral left zygoma and maxilla. The mass is of mixed opacity with a large rounded densely mineralized area (arrowheads) arising from the lateral zygomatic arch. An extensive soft tissue component (arrowed) extends into and replaces the left maxilla and frontal sinus. Multiple teeth are absent and the first molar (*) is surrounded by the mass. (b) Lacrimal cyst in a dog with facial swelling and epiphora. A large contrast-filled cavity (arrowed) is superimposed on the dorsocaudal nasal chamber and lacrimal bone region. Dacryocystography (arrowhead) has been performed to demonstrate the communication between the lacrimal duct and the cyst. © 2013 British Small Animal Veterinary Association

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8.47 Orbital disease. (a) DV view of the skull of a cat with exophthalmos of the left eye and facial swelling. Clinical assessment often underestimates the extent of facial swelling as in this cat, which has a mass that has replaced most of the rostral left zygoma and maxilla. The mass is of mixed opacity with a large rounded densely mineralized area (arrowheads) arising from the lateral zygomatic arch. An extensive soft tissue component (arrowed) extends into and replaces the left maxilla and frontal sinus. Multiple teeth are absent and the first molar (*) is surrounded by the mass. (b) Lacrimal cyst in a dog with facial swelling and epiphora. A large contrast-filled cavity (arrowed) is superimposed on the dorsocaudal nasal chamber and lacrimal bone region. Dacryocystography (arrowhead) has been performed to demonstrate the communication between the lacrimal duct and the cyst.

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8.48

Patient positioning for lateral oblique views of the maxillary and mandibular dental arcades. (a) The mouth is opened and the head rotated in a VD direction. (b) The roots of the maxillary premolars are almost parallel to the cassette using this extraoral technique. Caudally the roots of the molars are not parallel to the film and are geometrically distorted and superimposed. (c–d) For the mandibular teeth, the head is rotated in a DV direction and supported. The arrow denotes the X-ray beam. (e) The angle formed rostrally by the converging bodies of the mandible is narrow and it is more difficult to avoid superimposition of the opposite mandible. The roots of the first three premolars are near parallel and there is greater geometric distortion of the fourth premolar and first molar. © 2013 British Small Animal Veterinary Association

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8.48 Patient positioning for lateral oblique views of the maxillary and mandibular dental arcades. (a) The mouth is opened and the head rotated in a VD direction. (b) The roots of the maxillary premolars are almost parallel to the cassette using this extraoral technique. Caudally the roots of the molars are not parallel to the film and are geometrically distorted and superimposed. (c–d) For the mandibular teeth, the head is rotated in a DV direction and supported. The arrow denotes the X-ray beam. (e) The angle formed rostrally by the converging bodies of the mandible is narrow and it is more difficult to avoid superimposition of the opposite mandible. The roots of the first three premolars are near parallel and there is greater geometric distortion of the fourth premolar and first molar.

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8.49

Bisecting angle technique to image the incisors and canines. (a) The X-ray beam is centred on an imaginary line bisecting the angle between the cassette and the long axis of the tooth. (b) Using this technique, the incisor and canine roots are not geometrically distorted and the entire length of the root (arrowheads) can be assessed. © 2013 British Small Animal Veterinary Association

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8.49 Bisecting angle technique to image the incisors and canines. (a) The X-ray beam is centred on an imaginary line bisecting the angle between the cassette and the long axis of the tooth. (b) Using this technique, the incisor and canine roots are not geometrically distorted and the entire length of the root (arrowheads) can be assessed.

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8.50

(a) Lateral and (b) DV views of the skull of a skeletally immature dog with swelling of the mandibles due to craniomandibular osteopathy. (a) Florid new bone extends along the ventral aspect of the bodies of the mandible (arrowheads). There is no cortical destruction. (b) On the DV view, although the condition is bilateral, the changes are thicker and more proliferative on the left side (arrowheads). © 2013 British Small Animal Veterinary Association

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8.50 (a) Lateral and (b) DV views of the skull of a skeletally immature dog with swelling of the mandibles due to craniomandibular osteopathy. (a) Florid new bone extends along the ventral aspect of the bodies of the mandible (arrowheads). There is no cortical destruction. (b) On the DV view, although the condition is bilateral, the changes are thicker and more proliferative on the left side (arrowheads).

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8.51

Lateral radiographs of the skulls of two dogs with calvarial hyperostosis. There is marked thickening and sclerosis of the calvarium. (a) The frontal, parietal and occipital bones are involved (arrowed). The changes are severe with probable encroachment upon the dorsal cranial fossa. Note that the mandibles and bullae are not affected. (b) The changes are more localized to the frontal bone (arrowed). © 2013 British Small Animal Veterinary Association

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8.51 Lateral radiographs of the skulls of two dogs with calvarial hyperostosis. There is marked thickening and sclerosis of the calvarium. (a) The frontal, parietal and occipital bones are involved (arrowed). The changes are severe with probable encroachment upon the dorsal cranial fossa. Note that the mandibles and bullae are not affected. (b) The changes are more localized to the frontal bone (arrowed).

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8.52

Fracture of the maxilla. There is a sagittal split (arrowheads) with mild displacement in the hard palate, which extends to the level of the third premolar. © 2013 British Small Animal Veterinary Association

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8.52 Fracture of the maxilla. There is a sagittal split (arrowheads) with mild displacement in the hard palate, which extends to the level of the third premolar.

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8.53

Comminuted fracture of the left mandible. (a) On the lateral view, a complete fracture at the junction between the body and ramus of the mandible (white arrows) is visible. An undulating fracture line between the ramus and coronoid process is also present (black arrows). (b) On the VD view, a concurrent comminuted fracture of the zygomatic arch (white arrow) is also seen. The mandibular fracture (black arrow) is extra-articular as the temporomandibular joint is not involved. (Courtesy of Cambridge Veterinary School) © 2013 British Small Animal Veterinary Association

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8.53 Comminuted fracture of the left mandible. (a) On the lateral view, a complete fracture at the junction between the body and ramus of the mandible (white arrows) is visible. An undulating fracture line between the ramus and coronoid process is also present (black arrows). (b) On the VD view, a concurrent comminuted fracture of the zygomatic arch (white arrow) is also seen. The mandibular fracture (black arrow) is extra-articular as the temporomandibular joint is not involved. (Courtesy of Cambridge Veterinary School)

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8.54

Symphysis separation in a cat. The symphysis is widened (double-headed arrow) and the right hemimandible is displaced caudally relative to the left. Note the fracture of the right mandible (arrowed) between the canine and third premolar. © 2013 British Small Animal Veterinary Association

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8.54 Symphysis separation in a cat. The symphysis is widened (double-headed arrow) and the right hemimandible is displaced caudally relative to the left. Note the fracture of the right mandible (arrowed) between the canine and third premolar.

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8.55

VD intraoral view of a dog with a squamous cell carcinoma of the rostral mandible. There is a soft tissue swelling (arrowed). The invasive mass is primarily destructive with loss of bone around the right incisors (*). Despite the extent of destruction there is limited displacement of the incisors (arrowhead). © 2013 British Small Animal Veterinary Association

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8.55 VD intraoral view of a dog with a squamous cell carcinoma of the rostral mandible. There is a soft tissue swelling (arrowed). The invasive mass is primarily destructive with loss of bone around the right incisors (*). Despite the extent of destruction there is limited displacement of the incisors (arrowhead).

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8.56

VD intraoral view of the mandible of a dog with an ossifying epulis. Note the soft tissue swelling (arrowed) lying along the gingival margin adjacent to the right first molar. Faint linear mineralization is superimposed on the swelling. The appearance is consistent with that of a tumour of periodontal ligament origin (epulis). There is no evidence of bone destruction. The mass is small and easily overlooked and would be obscured on VD views where the mandible is superimposed on the maxilla. © 2013 British Small Animal Veterinary Association

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8.56 VD intraoral view of the mandible of a dog with an ossifying epulis. Note the soft tissue swelling (arrowed) lying along the gingival margin adjacent to the right first molar. Faint linear mineralization is superimposed on the swelling. The appearance is consistent with that of a tumour of periodontal ligament origin (epulis). There is no evidence of bone destruction. The mass is small and easily overlooked and would be obscured on VD views where the mandible is superimposed on the maxilla.

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8.57

Lateral view of the skull of a cat with a fibroma of the rostral mandible. There is a dense, well defined but irregular bony mass (arrowheads) arising from the rostral mandibular cortex. The pattern is predominantly productive rather than destructive. © 2013 British Small Animal Veterinary Association

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8.57 Lateral view of the skull of a cat with a fibroma of the rostral mandible. There is a dense, well defined but irregular bony mass (arrowheads) arising from the rostral mandibular cortex. The pattern is predominantly productive rather than destructive.

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8.58

VD intraoral view of a cat with a soft tissue swelling along the rostral right hemimandible due to a plasmacytoma. An extensive irregular osteolytic pattern surrounds the root of the right mandibular canine. There is slight expansion of the bone. The cortex is thinned and ragged (arrowheads) but the symphysis is intact. Differential diagnoses for the destructive pattern include neoplasia (especially squamous cell carcinoma) and severe focal osteomyelitis. However, the appearance suggests a process arising from within, rather than a soft tissue mass invading into, the mandible. Lack of specificity of the radiographic changes emphasizes the importance of obtaining a histopathological diagnosis by biopsy. © 2013 British Small Animal Veterinary Association

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8.58 VD intraoral view of a cat with a soft tissue swelling along the rostral right hemimandible due to a plasmacytoma. An extensive irregular osteolytic pattern surrounds the root of the right mandibular canine. There is slight expansion of the bone. The cortex is thinned and ragged (arrowheads) but the symphysis is intact. Differential diagnoses for the destructive pattern include neoplasia (especially squamous cell carcinoma) and severe focal osteomyelitis. However, the appearance suggests a process arising from within, rather than a soft tissue mass invading into, the mandible. Lack of specificity of the radiographic changes emphasizes the importance of obtaining a histopathological diagnosis by biopsy.

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8.59

VD intraoral view of a dog with an osteosarcoma of the mandible. An extensive mass of mixed appearance is visible. The cortices of the mandible have been destroyed and there is florid disorganized amorphous new bone. The expansion of the hemimandible (arrowheads), destruction and amorphous new bone are consistent with a primary tumour arising from bone. © 2013 British Small Animal Veterinary Association

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8.59 VD intraoral view of a dog with an osteosarcoma of the mandible. An extensive mass of mixed appearance is visible. The cortices of the mandible have been destroyed and there is florid disorganized amorphous new bone. The expansion of the hemimandible (arrowheads), destruction and amorphous new bone are consistent with a primary tumour arising from bone.

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8.60

(a) Lateral and (b) DV intraoral views of the maxilla of a dog with a soft tissue sarcoma. (a) Extensive soft tissue swelling (arrowheads) is visible on the lateral view. (b) The extent of the bone destruction involving the left premaxilla and maxilla (arrowheads) is only appreciated on the DV intraoral view. As with many maxillary masses, there is little or no periosteal reaction. © 2013 British Small Animal Veterinary Association

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8.60 (a) Lateral and (b) DV intraoral views of the maxilla of a dog with a soft tissue sarcoma. (a) Extensive soft tissue swelling (arrowheads) is visible on the lateral view. (b) The extent of the bone destruction involving the left premaxilla and maxilla (arrowheads) is only appreciated on the DV intraoral view. As with many maxillary masses, there is little or no periosteal reaction.

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8.61

Radiograph of the rostral mandible of a cat obtained using the bisecting angle technique. Both canines have extensive enamel and dentine defects (arrowed) of the crown and crown–root junction. These changes are advanced (early resorptive lesions are difficult to recognize on radiographs). The irregularity of the mandibular symphysis is normal for an aged cat. (Courtesy of L Milella, The Veterinary Dental Practice) © 2013 British Small Animal Veterinary Association

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8.61 Radiograph of the rostral mandible of a cat obtained using the bisecting angle technique. Both canines have extensive enamel and dentine defects (arrowed) of the crown and crown–root junction. These changes are advanced (early resorptive lesions are difficult to recognize on radiographs). The irregularity of the mandibular symphysis is normal for an aged cat. (Courtesy of L Milella, The Veterinary Dental Practice)

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8.62

VD intraoral view of the rostral mandible of a dog with periapical abscessation of both maxillary canines. Focal lysis surrounding the apices of both incisors is visible (double-headed arrow). Note that crown fractures (arrowheads) exposing the pulp canal are present on both the left and the right and that the pulp canal is widened. These changes are consistent with bilateral periapical abscessation and pulpitis. © 2013 British Small Animal Veterinary Association

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8.62 VD intraoral view of the rostral mandible of a dog with periapical abscessation of both maxillary canines. Focal lysis surrounding the apices of both incisors is visible (double-headed arrow). Note that crown fractures (arrowheads) exposing the pulp canal are present on both the left and the right and that the pulp canal is widened. These changes are consistent with bilateral periapical abscessation and pulpitis.

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8.63

Lateral oblique view of the maxilla of a dog with a facial swelling due to a periapical abscess. The lamina dura surrounding the caudal root of the fourth premolar is indistinct (arrowheads). The trabecular bone is reduced in density and has a coarse appearance. These changes are consistent with an early periapical abscess. © 2013 British Small Animal Veterinary Association

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8.63 Lateral oblique view of the maxilla of a dog with a facial swelling due to a periapical abscess. The lamina dura surrounding the caudal root of the fourth premolar is indistinct (arrowheads). The trabecular bone is reduced in density and has a coarse appearance. These changes are consistent with an early periapical abscess.

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8.64

Lateral oblique view of the maxilla of a dog with periapical abscesses of both fourth premolars. Note the extensive bone loss due to periapical abscessation surrounding the rostral roots of the right (large black arrow) and rostral and caudal roots of the left (small black arrows) maxillary fourth premolars. Other radiological changes include horizontal bone loss between the first and third premolars and retention of the rostral root of the second premolar (white arrow). © 2013 British Small Animal Veterinary Association

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8.64 Lateral oblique view of the maxilla of a dog with periapical abscesses of both fourth premolars. Note the extensive bone loss due to periapical abscessation surrounding the rostral roots of the right (large black arrow) and rostral and caudal roots of the left (small black arrows) maxillary fourth premolars. Other radiological changes include horizontal bone loss between the first and third premolars and retention of the rostral root of the second premolar (white arrow).

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8.65

VD view of the skull of a dog presented with nasal discharge and reverse sneezing due to an oronasal fistula. A focal area of lysis (arrowed) is superimposed on the right nasal chamber and hard palate (maxilla) medial to the maxillary recess. The adjacent turbinates are blurred due to the accumulated secretions or inflammation and there is also focal turbinate destruction. All teeth apart from the right maxillary canine are absent. The diagnosis can be confirmed by visual inspection and probing the defect. © 2013 British Small Animal Veterinary Association

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8.65 VD view of the skull of a dog presented with nasal discharge and reverse sneezing due to an oronasal fistula. A focal area of lysis (arrowed) is superimposed on the right nasal chamber and hard palate (maxilla) medial to the maxillary recess. The adjacent turbinates are blurred due to the accumulated secretions or inflammation and there is also focal turbinate destruction. All teeth apart from the right maxillary canine are absent. The diagnosis can be confirmed by visual inspection and probing the defect.

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8.66

(a) Lateral rostral oblique and (b) VD views of the mandibles of two dogs with dentigerous cysts. (a) A well defined lucent cystic area (arrowheads), consistent with a dentigerous cyst, is present in the rostral mandible at the level where a tooth was absent on visual inspection. The unerupted first premolar is oriented horizontally (arrowed) and the cyst also surrounds the roots of the second premolar. (b) In this dog, the cysts are bilateral (arrowed) and surround multiple roots. (Courtesy of L Milella, The Veterinary Dental Practice) © 2013 British Small Animal Veterinary Association

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8.66 (a) Lateral rostral oblique and (b) VD views of the mandibles of two dogs with dentigerous cysts. (a) A well defined lucent cystic area (arrowheads), consistent with a dentigerous cyst, is present in the rostral mandible at the level where a tooth was absent on visual inspection. The unerupted first premolar is oriented horizontally (arrowed) and the cyst also surrounds the roots of the second premolar. (b) In this dog, the cysts are bilateral (arrowed) and surround multiple roots. (Courtesy of L Milella, The Veterinary Dental Practice)

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8.67

Intraoral radiograph of the mandibular molars. The pulp cavity of the first molar contains several small mineral opacities. These concretions represent pulpal stones and are an incidental finding. They are only relevant if endodontics is to be performed. (Courtesy of L Milella, The Veterinary Dental Practice) © 2013 British Small Animal Veterinary Association

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8.67 Intraoral radiograph of the mandibular molars. The pulp cavity of the first molar contains several small mineral opacities. These concretions represent pulpal stones and are an incidental finding. They are only relevant if endodontics is to be performed. (Courtesy of L Milella, The Veterinary Dental Practice)

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8.68

DV intraoral view of the maxilla of a dog with an ossifying epulis. A cauliflower-like ossified mass is visible adjacent to the rostral aspect of the third premolar (white arrowhead). There is no evidence of bone destruction. Other findings include the absence of the second left maxillary premolar (*) and the left and right fourth maxillary premolars, with the palatal root of the right fourth premolar being retained (black arrowhead). © 2013 British Small Animal Veterinary Association

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8.68 DV intraoral view of the maxilla of a dog with an ossifying epulis. A cauliflower-like ossified mass is visible adjacent to the rostral aspect of the third premolar (white arrowhead). There is no evidence of bone destruction. Other findings include the absence of the second left maxillary premolar (*) and the left and right fourth maxillary premolars, with the palatal root of the right fourth premolar being retained (black arrowhead).

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8.69

Canine acanthomatous ameloblastoma (acanthomatous epulis) demonstrating infiltration of the bone. DV intraoral view of the premaxilla. The second right maxillary incisor is missing. A poorly defined soft tissue swelling is present between the third and first incisors. The poorly marginated lysis (arrowhead) of the alveolar bone is consistent with infiltrative growth of the tumour. © 2013 British Small Animal Veterinary Association

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8.69 Canine acanthomatous ameloblastoma (acanthomatous epulis) demonstrating infiltration of the bone. DV intraoral view of the premaxilla. The second right maxillary incisor is missing. A poorly defined soft tissue swelling is present between the third and first incisors. The poorly marginated lysis (arrowhead) of the alveolar bone is consistent with infiltrative growth of the tumour.

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8.70

VD intraoral view of the mandible of a young dog with compound odontomas of the rostral left and right hemimandibles. The expansile masses contain multiple advanced dental components (enamel, dentine and cementum), indicating that it is of odontogenic origin. The changes are more dramatic on the right side (arrowheads). There is marked displacement of the deciduous and permanent dentition (arrowed). The swelling may only become apparent later in life. (Courtesy of L Milella, The Veterinary Dental Practice) © 2013 British Small Animal Veterinary Association

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8.70 VD intraoral view of the mandible of a young dog with compound odontomas of the rostral left and right hemimandibles. The expansile masses contain multiple advanced dental components (enamel, dentine and cementum), indicating that it is of odontogenic origin. The changes are more dramatic on the right side (arrowheads). There is marked displacement of the deciduous and permanent dentition (arrowed). The swelling may only become apparent later in life. (Courtesy of L Milella, The Veterinary Dental Practice)

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8.71

(a) Patient positioning for a sagittal oblique view of the temporomandibular joint. The joint being assessed is positioned closest to the plate, the nose is elevated in the sagittal plane using a foam wedge, and the X-ray beam is centred on the base of the skull at the level of the dependent temporomandibular joint. For evaluation of the left temporomandibular joint, this results in a right 20 degrees rostral–left caudal oblique (Rt20°R-LeCdO) view. (b) Elevation of the nose separates the temporomandibular joints and the lower joint is rotated cranially. The joint space (black arrows) is parallel to the beam. The white arrow denotes the retroarticular process. CF = mandibular fossa; CP = condyloid process. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.71 (a) Patient positioning for a sagittal oblique view of the temporomandibular joint. The joint being assessed is positioned closest to the plate, the nose is elevated in the sagittal plane using a foam wedge, and the X-ray beam is centred on the base of the skull at the level of the dependent temporomandibular joint. For evaluation of the left temporomandibular joint, this results in a right 20 degrees rostral–left caudal oblique (Rt20°R-LeCdO) view. (b) Elevation of the nose separates the temporomandibular joints and the lower joint is rotated cranially. The joint space (black arrows) is parallel to the beam. The white arrow denotes the retroarticular process. CF = mandibular fossa; CP = condyloid process. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.72

(a) DV and (b) magnified DV views of an immature dog with a malformation of the zygomatic arch. Note that the asymmetry of the mandibles is a consequence of the restriction caused by the malformation of the zygomatic arch (white arrows) and not the slight axial rotation as a result of positioning. The left temporomandibular joint is widened (black arrows). © 2013 British Small Animal Veterinary Association

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8.72 (a) DV and (b) magnified DV views of an immature dog with a malformation of the zygomatic arch. Note that the asymmetry of the mandibles is a consequence of the restriction caused by the malformation of the zygomatic arch (white arrows) and not the slight axial rotation as a result of positioning. The left temporomandibular joint is widened (black arrows).

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8.73

DV view of the skull of a cat following an unknown trauma. Multiple fractures are present. There is a minimally displaced midline fracture of the hard palate (white arrowheads), separation of the mandibular symphysis (black arrowheads) and a fracture of the lateral aspect of the temporomandibular joint with rostral displacement of the mandibular condyle (arrowed). Consequently, the coronoid process (*) has rotated outwards. © 2013 British Small Animal Veterinary Association

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8.73 DV view of the skull of a cat following an unknown trauma. Multiple fractures are present. There is a minimally displaced midline fracture of the hard palate (white arrowheads), separation of the mandibular symphysis (black arrowheads) and a fracture of the lateral aspect of the temporomandibular joint with rostral displacement of the mandibular condyle (arrowed). Consequently, the coronoid process (*) has rotated outwards.

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8.74

Lateral oblique view of the tympanic bullae. The dependent bulla is projected ventral to the skull base and is filled with air (arrowed). The upper bulla (*) is superimposed on the skull base. © 2013 British Small Animal Veterinary Association

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8.74 Lateral oblique view of the tympanic bullae. The dependent bulla is projected ventral to the skull base and is filled with air (arrowed). The upper bulla (*) is superimposed on the skull base.

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8.75

(a–b) Patient positioning for an open-mouth rostrocaudal view of the bullae (arrowed). The lower jaw is pulled out of the primary beam to avoid superimposition of the tongue, and the hard palate is tilted dorsally by 20–30 degrees. (c) The air-filled bullae (arrowed) are projected between the rami of the mandible. © 2013 British Small Animal Veterinary Association

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8.75 (a–b) Patient positioning for an open-mouth rostrocaudal view of the bullae (arrowed). The lower jaw is pulled out of the primary beam to avoid superimposition of the tongue, and the hard palate is tilted dorsally by 20–30 degrees. (c) The air-filled bullae (arrowed) are projected between the rami of the mandible.

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8.76

(a) Patient positioning for a rostral 10 degrees ventral–caudodorsal oblique (R10°V-CdDO) view of the bullae in a cat. The mouth is closed and the hard palate tilted 10 degrees towards the vertical. (b) The large bullae (arrowheads) are projected ventral to the skull base. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission. © 2013 British Small Animal Veterinary Association

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8.76 (a) Patient positioning for a rostral 10 degrees ventral–caudodorsal oblique (R10°V-CdDO) view of the bullae in a cat. The mouth is closed and the hard palate tilted 10 degrees towards the vertical. (b) The large bullae (arrowheads) are projected ventral to the skull base. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.

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8.77

(a) Lateral oblique view of the right bulla and (b) DV view of the skull of a dog with otitis media. Air in the bulla has been replaced by a soft tissue/bone opacity consistent with otitis media (arrowed). The distal ear canal is mineralized (arrowheads). © 2013 British Small Animal Veterinary Association

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8.77 (a) Lateral oblique view of the right bulla and (b) DV view of the skull of a dog with otitis media. Air in the bulla has been replaced by a soft tissue/bone opacity consistent with otitis media (arrowed). The distal ear canal is mineralized (arrowheads).

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8.78

(a) DV and (b) left and (c) right lateral oblique views of the bullae of a cat with otitis media due to a polyp. (a) The left bulla is slightly enlarged and sclerotic (arrowed). A normal air-filled external ear canal cannot be recognized on the left side (arrowhead). (b) The left bulla is filled with a soft tissue opacity and is markedly sclerotic (arrowed). The dense petrous temporal bone lies dorsal to the bulla (*). (c) Normal right bulla (arrowed). © 2013 British Small Animal Veterinary Association

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8.78 (a) DV and (b) left and (c) right lateral oblique views of the bullae of a cat with otitis media due to a polyp. (a) The left bulla is slightly enlarged and sclerotic (arrowed). A normal air-filled external ear canal cannot be recognized on the left side (arrowhead). (b) The left bulla is filled with a soft tissue opacity and is markedly sclerotic (arrowed). The dense petrous temporal bone lies dorsal to the bulla (*). (c) Normal right bulla (arrowed).

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8.79

(a) Rostral 10 degrees ventral–caudodorsal oblique (R10°V-CdDO) and (b) DV views of the bullae of a cat with an aural tumour involving the left bulla. (a) The left tympanic bulla is of soft tissue opacity (arrowed). Note the extensive soft tissue swelling lateral to the bulla and displaced bone fragments (arrowhead). The air-filled external ear canal cannot be recognized. (b) On the DV view, the lateral aspect of the bulla appears disrupted (arrowheads) with displacement of the bone fragments laterally. Extensive lysis of the basicranium was also recognized on CT; however, these changes can only be suspected on radiography by the roughening and thinning of the lateral aspect of the cranial bones (arrowed). © 2013 British Small Animal Veterinary Association

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8.79 (a) Rostral 10 degrees ventral–caudodorsal oblique (R10°V-CdDO) and (b) DV views of the bullae of a cat with an aural tumour involving the left bulla. (a) The left tympanic bulla is of soft tissue opacity (arrowed). Note the extensive soft tissue swelling lateral to the bulla and displaced bone fragments (arrowhead). The air-filled external ear canal cannot be recognized. (b) On the DV view, the lateral aspect of the bulla appears disrupted (arrowheads) with displacement of the bone fragments laterally. Extensive lysis of the basicranium was also recognized on CT; however, these changes can only be suspected on radiography by the roughening and thinning of the lateral aspect of the cranial bones (arrowed).

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8.80

Lateral view of the pharynx of a cat with a nasopharyngeal polyp. An oval soft tissue mass (arrowed) lies dorsal to the soft palate and displaces it ventrally. Both the cranial and caudal borders are visible. © 2013 British Small Animal Veterinary Association

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8.80 Lateral view of the pharynx of a cat with a nasopharyngeal polyp. An oval soft tissue mass (arrowed) lies dorsal to the soft palate and displaces it ventrally. Both the cranial and caudal borders are visible.

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8.81

Lateral radiograph of the skull and pharynx of a brachycephalic dog. The soft palate is thickened and elongated (white arrow), the nasopharynx is narrowed (black arrows) and the thickened retropharyngeal tissues have displaced the pharynx ventrally. The caudal aspect of the soft palate extends beyond the tip of the epiglottis. © 2013 British Small Animal Veterinary Association

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8.81 Lateral radiograph of the skull and pharynx of a brachycephalic dog. The soft palate is thickened and elongated (white arrow), the nasopharynx is narrowed (black arrows) and the thickened retropharyngeal tissues have displaced the pharynx ventrally. The caudal aspect of the soft palate extends beyond the tip of the epiglottis.

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Lateral view of the pharynx of a dog with a retropharyngeal stick injury. A large retropharyngeal abscess extends from the pharynx to the level of the fifth cervical vertebra (white arrows). The abscess contains fluid and gas. The larynx and cervical trachea are displaced ventrally by the swelling and the nasopharynx is markedly narrowed (black arrow). Two large stick fragments were retrieved during surgery; however, they cannot be recognized on the radiograph. © 2013 British Small Animal Veterinary Association

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8.82 Lateral view of the pharynx of a dog with a retropharyngeal stick injury. A large retropharyngeal abscess extends from the pharynx to the level of the fifth cervical vertebra (white arrows). The abscess contains fluid and gas. The larynx and cervical trachea are displaced ventrally by the swelling and the nasopharynx is markedly narrowed (black arrow). Two large stick fragments were retrieved during surgery; however, they cannot be recognized on the radiograph.

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Nasopharyngeal stenosis. The junction between the posterior nares and the nasopharynx is kinked and narrowed (arrowed). Although contrast procedures can be used to demonstrate this abnormality, cross-sectional imaging is the technique of choice. © 2013 British Small Animal Veterinary Association

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8.83 Nasopharyngeal stenosis. The junction between the posterior nares and the nasopharynx is kinked and narrowed (arrowed). Although contrast procedures can be used to demonstrate this abnormality, cross-sectional imaging is the technique of choice.

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Lateral views of the pharynx of two cats with nasopharyngeal swellings. (a) A broad soft tissue mass fills the nasopharynx dorsal to the soft palate (arrowed). The mass does not displace the soft palate. The mass was confirmed as lymphoma but cannot be distinguished from a nasopharyngeal polyp based on radiographic appearance alone. (b) The broad-based soft tissue mass (arrowed) bulges into the caudal aspect of the pharynx, reducing the size of the normally air-filled space. The mass was confirmed as an extensive squamous cell carcinoma of the fauces, extending into the pharynx. © 2013 British Small Animal Veterinary Association

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8.84 Lateral views of the pharynx of two cats with nasopharyngeal swellings. (a) A broad soft tissue mass fills the nasopharynx dorsal to the soft palate (arrowed). The mass does not displace the soft palate. The mass was confirmed as lymphoma but cannot be distinguished from a nasopharyngeal polyp based on radiographic appearance alone. (b) The broad-based soft tissue mass (arrowed) bulges into the caudal aspect of the pharynx, reducing the size of the normally air-filled space. The mass was confirmed as an extensive squamous cell carcinoma of the fauces, extending into the pharynx.

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Lateral view of the pharynx of a cat with inspiratory dyspnoea due to a laryngeal mass (lymphoma). The larynx is markedly thickened by the concentric soft tissue mass (arrowheads). The pharynx is distended with air as a result of the obstruction caused by the laryngeal mass and respiratory effort. The cranial cervical trachea is also distended with air. © 2013 British Small Animal Veterinary Association

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8.85 Lateral view of the pharynx of a cat with inspiratory dyspnoea due to a laryngeal mass (lymphoma). The larynx is markedly thickened by the concentric soft tissue mass (arrowheads). The pharynx is distended with air as a result of the obstruction caused by the laryngeal mass and respiratory effort. The cranial cervical trachea is also distended with air.

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Lateral view of the skull of a dog with bilateral sialoadenitis. The radiographic changes are limited to soft tissue swelling caudoventral to the angle of the jaw (arrowed). © 2013 British Small Animal Veterinary Association

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8.86 Lateral view of the skull of a dog with bilateral sialoadenitis. The radiographic changes are limited to soft tissue swelling caudoventral to the angle of the jaw (arrowed).

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(a) VD survey radiograph and (b) sialogram of the skull of a dog with extensive cellulitis surrounding the left ear. (a) There is extensive swelling (arrowed) around the left external ear canal (*). (b) The parotid duct has been cannulated (arrowed) and the duct (arrowheads) has a normal thin, even appearance. The gland (P) is not disrupted and the contrast medium results in a normal ‘cobble stone’ appearance. The sialogram confirms that the cellulitis is not associated with the parotid gland. © 2013 British Small Animal Veterinary Association

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8.87 (a) VD survey radiograph and (b) sialogram of the skull of a dog with extensive cellulitis surrounding the left ear. (a) There is extensive swelling (arrowed) around the left external ear canal (*). (b) The parotid duct has been cannulated (arrowed) and the duct (arrowheads) has a normal thin, even appearance. The gland (P) is not disrupted and the contrast medium results in a normal ‘cobble stone’ appearance. The sialogram confirms that the cellulitis is not associated with the parotid gland.

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(a) VD radiograph of a dog with sialoliths. The sialoliths appear as small discrete mineralized bodies (arrowed) either singularly or in clusters. In this dog, they are bilateral. On the right, they are located close to the termination of the parotid duct of the buccal mucosa, opposite the fourth maxillary premolar, and on the left, they are located within the gland and proximal parotid duct. (b) Lateral radiograph of a dog with sialoliths. The sialoliths appear as small discrete mineralized bodies (arrowed) either singularly or in clusters. © 2013 British Small Animal Veterinary Association

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8.88 (a) VD radiograph of a dog with sialoliths. The sialoliths appear as small discrete mineralized bodies (arrowed) either singularly or in clusters. In this dog, they are bilateral. On the right, they are located close to the termination of the parotid duct of the buccal mucosa, opposite the fourth maxillary premolar, and on the left, they are located within the gland and proximal parotid duct. (b) Lateral radiograph of a dog with sialoliths. The sialoliths appear as small discrete mineralized bodies (arrowed) either singularly or in clusters.

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Lateral radiograph of the skull of a dog with hyoid bone trauma. There is a luxation between the right epihyoid and ceratohyoid bones. The distal epihyoid bone (arrowed) is displaced caudally relative to the ceratohyoid bone (arrowhead). © 2013 British Small Animal Veterinary Association

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8.89 Lateral radiograph of the skull of a dog with hyoid bone trauma. There is a luxation between the right epihyoid and ceratohyoid bones. The distal epihyoid bone (arrowed) is displaced caudally relative to the ceratohyoid bone (arrowhead).

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Lateral radiograph of the skull of a dog with chronic para-aural abscessation (left side) and hyoid bone changes. One of the stylohoid bones (left) is markedly thickened (arrowed), mottled and sclerotic, representing chronic osteitis/periostitis. (Courtesy of Cambridge Veterinary School) © 2013 British Small Animal Veterinary Association

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8.90 Lateral radiograph of the skull of a dog with chronic para-aural abscessation (left side) and hyoid bone changes. One of the stylohoid bones (left) is markedly thickened (arrowed), mottled and sclerotic, representing chronic osteitis/periostitis. (Courtesy of Cambridge Veterinary School)