Page 14 - Atlas of Small Animal CT and MRI

4 Atlas of Small Animal CT and MRI

case with plant awns or small wood fragments, diagnostic air‐filled nasopharynx are more likely to be identified
features include focal turbinate destruction, hyperplasia (Figure 1.1.10). Nasal polyps occasionally ossify and can
of the remaining overlying nasal mucosa, and regional be mistaken for intranasal neoplasia, such as osteosar-
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accumulation of fluid or mucoid exudates. Foreign coma (Figure 1.1.11).
body rhinitis is usually unilateral except when multiple
foreign bodies are present, which can occur with plant Oronasal fistula
awn inhalation. The severity of the secondary imaging Oronasal fistulas may occur as developmental anomalies,
findings can be related to the chronicity of the disorder secondary to trauma, or subsequent to severe dental
as well as the inertness of the foreign material. In most disease or other inflammatory or neoplastic disorders.
patients, imaging abnormalities are limited to the nasal Large fistulas with discrete stomas are clearly evident on
cavity or nasopharynx and do not usually involve the cross‐sectional images. Smaller fistulas are more difficult
paranasal sinuses (Figures 1.1.5, 1.1.6, 1.1.7). 9 to diagnose when mucosal margins are in close apposi-
tion (Figures 1.1.12, 1.1.13).
Nonspecific rhinitis
Nonspecific rhinitis is a general term that includes Mycotic rhinitis
inflammatory nasal disorders from viral, bacterial, Mycotic rhinitis is a common sinonasal disorder of dogs and
parasitic, or allergic causes. Rhinitis may also occur as occurs periodically in cats. Aspergillosis is by far the most
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an extension of severe periodontal disease. The most common organism responsible for canine mycotic rhinitis,
common biopsy diagnosis in this category of disease is but other less common organisms include Cryptococcus,
lymphocytic–plasmocytic rhinitis, which may also have Rhinosporidium, and Blastomyces. Cryptococcus is the most
a neutrophilic or predominantly eosinophilic component common causative agent in cats with mycotic rhinitis, but
(Figures 1.1.8, 1.1.9). Rhinitis may also occur secondary aspergillosis has also been reported.
to severe dental disease. Conventional radiographic abnormalities associated
Radiographic findings may be normal, and cross‐ with aspergillosis include decreased nasal cavity opacity,
sectional imaging findings may range from minimal to loss of recognizable turbinate architecture and marginal
marked. Exudative fluid is present bilaterally within the remodeling, soft‐tissue opacification within the frontal
interstices of the nasal cavity, and fluid is generally present sinuses, and thickening of the frontal bone forming the
within the frontal and maxillary sinuses and the sphenoid frontal sinus margin.
recesses. The underlying nasal turbinate pattern is often In earlier phases of canine nasal aspergillosis, cross‐
unaffected, but turbinate atrophy, particularly the delicate sectional imaging characteristics often include a unilateral
bone of more peripheral turbinate regions, can occur increase in nasal mucosal volume, presumably due to
with chronic or severe disease. Fluid can be distinguished mucosal inflammation, hyperplasia, and associated
from underlying hyperplastic mucosa on MRI and on exudates. With progressive disease, there is marked tur-
contrast‐enhanced CT. Mucosa is typically prominent binate destruction and atrophy with resulting cavitation
and enhances intensely and uniformly. Dense bone of the in the affected nasal cavity, which may be most evident in
nasal septum and nasal cavity margins is rarely affected, the rostral to mid nasal cavity. The nasal cavity may have
although productive reactivity of the maxillary and a rim of soft‐tissue thickening, peripherally consisting of
frontal bones can be seen with chronic disease. fungal plaque and thickened mucosa. A soft‐tissue mass
Very rarely, canine patients may have much more component may be present in the caudal nasal cavity or
aggressive appearing imaging findings, including mass frontal sinus. These fungal masses have characteristic
lesions and dense bone destruction that appears consist- features that include a nonuniform gas and fluid pattern.
ent with neoplasia but has a biopsy diagnosis of eosino- Frontal sinus epithelial lining thickening is routinely
philic rhinitis. These rare cases could be unusual nasal present, and affected frontal sinuses may contain fluid. In
manifestations of eosinophilic granulomatous disease one study of 46 dogs, approximately 15% had disease
and, though inflammatory in etiology, are not typical of primarily affecting the frontal sinus. Affected maxillary,
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the imaging findings associated with nonspecific rhinitis. frontal, and vomer bones may become thickened with
Up to a third of cats with nasal disorders of any type and irregular margins due to reactivity. In some affected dogs,
many dogs with nasal disease also have secondary bulla bone lysis also occurs. Erosion or overt destruction
effusion associated with auditory tube occlusion. of the ethmoid bone (cribriform plate) resulting in
Nasal polyps are periodically encountered in associa- communication with the cranial vault may also occur.
tion with chronic inflammatory disease. Depending on This latter feature is important to evaluate since ethmoid
location, polyps may or may not be identified on cross‐ destruction may affect therapeutic options and has been
sectional images. Those polyps that extend into the associated with a marked worsening of prognosis for

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