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Fig 6: Left lateral static nuclear medicine image acquired during bone phase (a) (rostral to the left), right dorsal to left ventral oblique radiograph (b) (rostral to the left), transverse (c) (right to the left) and dorsal reconstruction (d) (right to the left) CT images centred at M2 (10’s in the Triadan system) from aWarmblood that presented with marked radiopharmaceutical uptake associated with the left maxillary molar region (arrows). Radiographs are normal but CT images show that the bone, lamina dura and mucosa surrounding the roots of left M2 and M3 (210 and 211) roots are thickened and irregular (asterisks).
infection (Bühler et al. 2014). In our study, 24 horses showed infundibular hypoattenuation in at least one tooth, but only in 8 were these changes identified in the clinically affected tooth. Although its clinical significance is unclear, the possibility of dental caries cannot be ruled out. Complementary examinations such as oral endoscopy may yield helpful information for the differentiation between pathological and nonpathological teeth in these cases (Ramzan 2009). Sinonasal cysts are expansile, mucus-filled cavities within
the paranasal sinuses that possess a wall with a mucus-secreting epithelial lining (Tremaine et al. 1999). This condition has previously been reported and represents approximately 13% of all paranasal sinus diseases in a study of 277 cases (Tremaine and Dixon 2001a). In the present study, 14% of horses in Group A were diagnosed with a sinus cyst. Computed tomography features of this condition consisted of a well-defined, rounded or multiloculated structured that occasionally presented wall mineralisation. Nonmineralised cysts may be difficult to detect when surrounded by large amounts of fluid on CT and impossible to recognise radiographically. In such cases it can be helpful to compare CT attenuation values of the sinus and cyst content. A rim-like contrast enhancement has been observed in post contrast MRI images in horses with sinus cysts (Tessier et al. 2013); therefore, a similar change could be expected with CT. In instances of large cysts, mass effect, bone deformation, exophthalmos and nasal septum deviation can be present (Tremaine and Dixon 2001a; Annear et al. 2008). Due to the space-occupying nature of the cysts, dental distortion can also be observed (Tucker and Farrell 2001). The typical location of this condition is the caudal maxillary sinus, but other locations include the frontal sinus and ethmoid labyrinth (Tremaine and Dixon 2001a). Although endoscopy was described as the ancillary diagnostic technique of choice for progressive ethmoid
haematomas (Tremaine and Dixon 2001a), CT provided important information, such as the exact location or the extent, when radiographic and endoscopic findings were not conclusive. Other indications for performing CT in progressive ethmoid haematoma cases include sinus involvement or multifocal disease (Textor et al. 2012). The sphenopalatine sinus was affected bilaterally in both cases included in this study. Both presented deviation of the sinus septum secondary to a mass effect. In both cases, high CT attenuation values were recorded (100–110 HU) in accordance with a previous study (Textor et al. 2012). Paranasal sinus disease is usually the consequence of
obstruction of the drainage ostia as a consequence of inflammatory processes initiated by primary bacterial infections, bacterial or fungal infection secondary to other disease processes such as dental disease and space- occupying expansile lesions and trauma (Tremaine and Dixon 2001b). Changes within individual sinus compartments can be identified with high detail using CT, especially in cases of ventral conchal and sphenopalatine sinus involvement where radiography was shown to be less accurate. Tomographic nature of CT images allows evaluation of each sinus separately, avoiding superimposition of surrounding structures. Moreover, thanks to the higher contrast resolution, it is possible to discriminate between tissues, making it possible to assess the respiratory mucosa. Thickening of the respiratory epithelium without concurrent changes would not be detected on radiographic images. All CT examinations were obtained in dorsal recumbency.
By consequence, when the frontomaxillary aperture is open, fluid from the caudal maxillary sinus can enter the conchofrontal sinus. Presence of fluid in the conchofrontal sinus without concurrent mucosal thickening may therefore not represent primary pathology of that sinus when the head is in this position.
© 2015 EVJ Ltd
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