Skull – nasal chambers and frontal sinuses

image of Skull – nasal chambers and frontal sinuses
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Indications for radiography of the nasal cavity and frontal sinuses include: nasal discharge, epistaxis, sneezing; head trauma; swelling, distortion, pain affecting maxillary or frontal regions; proptosis; and epiphora. This chapter examines standard and special views of radiography; normal anatomy; contrast studies; alternative imaging techniques and abnormal imaging findings.

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Image of 18.1
18.1 DV (intra-oral) view. The patient is in sternal recumbency with the film in the mouth. The X-ray beam is vertical.
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18.2 (a) Flexible film carrier held open to show the film (F) and screen (S). (b) The DV (intra-oral) is the single most useful view for nasal disease because it provides a view of the nasal cavity without superimposed structures.
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18.3 V20°R-DCdO (open-mouth VD) view of a skull. (a) The patient is placed in dorsal recumbency and the mouth opened. The X-ray beam is directed 20 degrees from the vertical to show more of the caudal aspect of the nasal cavity. (b) V20°R-DCdO (open-mouth VD) radiograph of a canine skull with anatomical landmarks indicated. The dotted line indicates the region of the cribriform plate.
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18.4 RCd (skyline) view. (a) The patient is placed in dorsal recumbency with the neck ventroflexed so that the hard palate is vertical. A vertical X-ray beam is centred on the external nares so that the diverging beam strikes the frontal sinuses. (b) Corresponding radiograph. This view is important for examination of the frontal sinuses, which may be the site of primary or secondary lesions in animals with nasal signs.
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18.5 An alternative (CdR) radiograph of the frontal sinuses may be made with a horizontal X-ray beam, the patient in sternal recumbency, and the beam directed towards a cassette propped up against the patient’s external nares.
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18.6 Anatomy of the nasal cavity as depicted by a DV (intra-oral) radiograph. The nasal cavity may be divided into three zones: rostral ®, where there are numerous fine, slightly wavy, parallel lines representing the nasal conchae; the mid-zone (M), where the turbinates are rounded and more widely spaced, producing a bubbly appearance, and the maxillary recess (MR) is visible as a distinct oval lucency immediately medial to the fourth premolar; caudal (Cd), where a series of linear paired lines represent the ethmoturbinates, which originate from the cribriform plate (arrowed).
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18.7 Cadaver experiments to mimic the effect of nasal diseases. (a) With the turbinates on the right (left side of image) removed, the nasal cavity in that region is more lucent and lacks the numerous fine lines that are visible in the contralateral side where the turbinates are intact. (b) With the entire nasal cavity largely filled with water, there is a diffuse increase in opacity and the turbinates are less clearly visible.
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18.8 DV (intra-oral) radiograph of a brachycephalic dog (English Bulldog). The internal anatomy of the nasal cavity is less well defined than in dolichocephalic dogs because structures are foreshortened and because of superimposition by the soft tissues of the head.
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18.9 Dacryorhinocystography. Injection of contrast medium into the upper punctum with the lower punctum occluded by Allis forceps. The nasolacrimal duct is patent and contrast is leaking into the nasal cavity close to the external nares. There is an irregular filling defect (arrowhead) caused by a grass seed lodged in the nasolacrimal duct.
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18.10 Normal canine transverse nasal CT images in a lung window. (a–d) These transverse CT images of the rostral, middle and caudal parts of the nasal cavity and the frontal sinuses illustrate the fine anatomical detail that is possible to achieve with this modality.
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18.11 Transverse (a) CT image in a lung window and (b) post-gadolinium T1W MR image at the same level in a dog without nasal disease. The CT image has higher resolution and higher contrast than the MR image, which increases visibility of fine nasal structures. Bone is also more clearly delineated in the CT image.
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18.12 Frontal sinus mucocoele. (a and c) Survey radiographs of a dog that had sustained fractures affecting the frontal bones several months previously. There is increased opacity and enlargement of the left frontal sinus (arrowed). (b and d) Contrast radiographs. A needle was inserted directly through the thin outer table of the frontal bone and organic iodide contrast medium injected. Lack of flow of contrast medium into the nasal cavity indicates obstruction of the nasofrontal meatus and supports a diagnosis of frontal sinus mucocoele.
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18.13 Sagittal nasal CT image (lung window) of a young Pug with clinical signs of brachycephalic obstructive airway syndrome. The nasal cavity is relatively small and there is protrusion of turbinates (arrowed) into the internal nares.
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18.14 DV (intra-oral) radiograph of a young dog showing an unusual bilateral cleft affecting the incisive bones with resulting malposition of the incisors.
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18.15 Nasal aspergillosis in a dog. (a) In the DV (intra-oral) radiograph there is increased opacity affecting the peripheral parts of the right nasal cavity and loss of turbinate detail, particularly medial to the third premolar where there is an oblong lucent zone (*). The contralateral structures appear normal. (b) In the RCd (skyline) radiograph there is thickening of the outer table of the right frontal bone (arrowheads), which has encroached on the lumen of the sinus. The zygomatic process now appears solid, whereas it normally contains the lateral aspect of the sinus (as on the contralateral side). This combination of signs is typical of destructive rhinitis and chronic sinusitis.
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18.16 The variable appearance of rhinitis in cats. (a) DV (intra-oral) radiograph of a cat with rhinitis associated with a mixed bacterial infection, in which the intranasal structures were interpreted as within normal limits. (b) DV (intra-oral) radiograph of a cat with chronic necrotizing rhinitis, in which there is a generalized increase in opacity with loss of turbinate detail affecting the left nasal cavity. (Reproduced from , with permission of the )
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18.17 Examples of CT images from animals with grass seed foreign bodies lodged in the nasal cavity. (a) Transverse CT image (lung window) of the right nasal chamber of a dog from which a grass seed was flushed. There is local loss of conchae (arrowed) and accumulation of material (*) compatible with exudate. (b) Transverse CT image (lung window) of the nasopharynx of a cat from which a grass seed fragment was removed endoscopically. The foreign body is visible as a small linear structure (arrowhead).
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18.18 Primary nasal neoplasia in a dog. (a) In the DV (intra-oral) radiograph there is increased opacity affecting the right nasal cavity and generalized loss of turbinate detail, resulting in a relatively homogeneous appearance. The contralateral structures appear normal. (b) In the RCd (skyline) radiograph there is soft tissue/fluid opacity filling the ipsilateral frontal sinus.
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18.19 Advanced nasal neoplasms. (a) Partial loss of the vomer and a soft tissue mass bulging to the left in a dog with nasal carcinoma. (b) Bilateral increased opacity, generalized loss of turbinate detail, complete loss of the central portion of the vomer and multiple small lucent foci medial to the right fourth premolar compatible with lysis of the hard palate in a dog with advanced nasal carcinoma.
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18.20 Obstruction of the external nares by a nasal neoplasm. (a) DV (intra-oral) radiograph of a dog with a nasal neoplasm in which there is obliteration of the right nostril. The left nostril remains visible because of the air it contains (*). (b) Photograph of this patient showing the ulcerated mass occluding the right nostril.
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18.21 Nasal neoplasia in the cat. (a) DV (intra-oral) radiograph of a cat with a granular cell tumour originating in the right nasal cavity. There is a relatively uniform increased opacity with loss of turbinate detail affecting the right nasal cavity and a focal lucent area (*) as a result of bone destruction. (b) DV (intra-oral) radiograph of a cat with nasal lymphoma. There is a generalized increased opacity and obscured turbinates, most marked in the left nasal cavity. (Reproduced from , with permission of the
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18.22 (a) Lateral radiograph of a normal feline skull in which the cribriform plate is visible (arrowheads). (b) Loss of the cribriform plate (arrowed) as a result of destruction by an invasive neoplasm.
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18.24 CT images of dogs with nasal conditions. (a) Aspergillosis. (b) Malignant nasal neoplasia. The structural features of these conditions are more clearly visible than in conventional radiographs. Note the displacement of the nasal septum and the bone destruction affecting the turbinates and maxilla in (b). (c) Three-dimensional reconstruction of the skull of a dog with an aggressive nasal neoplasm destroying the palate, cribriform plate and medial aspect of both orbits.
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18.25 MRI in a dog with a left-sided nasal carcinoma. (a) T2W sagittal image of the left nasal chambers shows a large mass that has filled the chamber. The cribriform plate and olfactory bulb (OB) appear unaffected. The left frontal sinus is filled with material (*) that has a different (higher) signal intensity than the tumour, probably representing accumulated mucus. (b) Similar contralateral image, which appears normal.
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18.26 MRI in a dog with a nasal carcinoma that has invaded the brain. T1W dorsal images (a) before and (b) after administration of contrast medium show a left nasal mass (*) that has extended through the cribriform plate and invaded the left olfactory lobe of the brain (arrowhead).
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18.27 Nasopharyngeal foreign body (pebble) in (a) lateral and (b) DV (intra-oral) radiographs of a stone-carrying dog. This object was removed orally using forceps. The enlarged pulp cavity affecting the right upper canine (arrowed) is the result of a tooth fracture that also occurred because of stone carrying.
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18.28 Lateral radiograph of a cat showing a rounded intraluminal soft tissue mass in the nasopharynx (arrowed). This appearance is typical of nasopharyngeal polyp in the cat. Larger lesions may also cause ventral displacement of the soft palate.
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18.29 Transverse CT images of a cat with a nasopharyngeal polyp. (a) Bone window image showing obliteration of the nasopharynx (*) and material filling both tympanic cavities. (b) Post-contrast image with soft tissue window showing a mass (*) with predominantly peripheral contrast accumulation occupying the nasopharynx. (c) Similar image just caudal to (b) shows the stalk of the polyp (arrowheads) originating from the left auditory tube.
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18.30 Nasopharyngeal neoplasm in a dog. Lateral radiograph of a dog with nasal signs showing a sessile soft tissue mass (*) on the dorsal aspect of the nasopharynx (NP). SP = soft palate.
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18.31 Nasopharyngeal stenosis in a cat. (a) Lateral radiograph of the head showing a narrow strand-like soft tissue opacity across the nasopharynx (arrowed). At this site there is also a slight dorsal deviation of the soft palate. (b) Positive-contrast rhinography showing a partial obstruction to the flow of contrast medium and a distinct septum in the nasopharynx (arrowed) at the same site as the strand-like soft tissue opacity in (a). (c) Retrograde endoscopic image of the nasopharyngeal area (ventral at top) showing a pale, smooth membrane that spans the entire nasopharynx (arrowed) with only a single small orifice at its centre. Note that the variation in colour hue during reproduction of this image makes it erroneously appear that the cat was cyanotic. (d) Lateral fluoroscopic image of the head during balloon dilation to treat the stenosis. A waist in the balloon at the site of the septum (arrowed) was observed transiently before disappearing on full inflation of the balloon. (Reproduced from , with permission from )
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