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EQUINE VETERINARY EDUCATION / AE / MARCH 2015


TABLE 2: Sensitivity, specificity and positive and negative predictive values for diagnosing clinically confirmed dental disease in 32 horses of Group A, using radiography and computed tomography


Radiography Computed tomography


Sensitivity (%) 72.5 (66.2–78.8)


100 (98.5–100)


Specificity (%) 89.5 (85.1–93.8)


96.7 (94.2–99.2) PPV = positive predictive values, NPV = negative predictive values.


summarised in Table 2. Computed tomography showed the highest sensitivity and specificity for correctly identifying dental disease.


Computed tomography identified all clinically affected


teeth. However, in 5 of the 32 horses (16%), CT showed more abnormal teeth than clinically suspected. Computed tomography and radiographs agreed in the identification of the same teeth in only 16 of the 32 horses (50%). Computed tomography showed tooth fractures in 11 cases, while only 4 of these cases were identified radiographically. Computed tomography allowed identification of a greater


number of dental abnormalities in all horses. In 24 of the 42 horses (57%), the infundibulum showed hypoattenuation in at least one tooth. This hypoattenuation was, however, observed in affected teeth in only 8 cases (18%). There were 6 sinus cysts, 2 of which appeared multilobulated, while the rest had a rounded shape. Two of the 6 cases (33%) were diagnosed radiographically as a well delineated soft tissue mass. The remaining 4 were missed on radiographs as a result of a diffuse increased soft tissue opacity filling the caudal maxillary and conchofrontal sinuses. On CT they appeared as a well defined structure in 5 cases, while in one case the cyst was silhouetting with fluid present within the sinuses (Fig 1). In 2 cases, a faint mineralised capsule was present which was not seen on radiographs. A concurrent mass effect consisted of nasal septum deviation in 3 cases, decrease of the cortical thickness of the maxillary bone in 2 cases and exophthalmos in one horse. Increase of the periodontal space and mild disruption of the lamina dura of the tooth ventral to the cyst were observed in 2 cases. Common location of the cyst was the caudal maxillary sinus, with invasion to the conchofrontal and ventral conchal sinuses observed in 2 cases. Invasion to the conchofrontal, ventral conchal and sphenopalatine sinuses was seen in another case. The average CT attenuation of the cyst content was 22 HU. Secondary sinusitis/fluid accumulation of variable amounts was present in all horses (Fig 1). This fluid was homogeneous and had an average CT attenuation value of 10 HU.


Agreement between CT and radiographs of sinus involvement was seen when respiratory mucosa was thicker than 10mm in combination with fluid levels, or when total obstruction of the sinus occurred. Compared to CT, radiographic abnormalities were observed in 19 of 28 horses (68%) and 18 of 24 horses (75%) for the rostral and caudal maxillary sinuses, respectively. Involvement of the conchofrontal sinus was identified radiographically in 15 of 23 horses (65%), while evidence of ventral conchal and sphenopalatine involvement was seen in only 10 of 23 horses (43%) and 3 of 18 horses (17%), respectively (Fig 2). Sensitivity, specificity, positive and negative predictive values for identifying sinus involvement confirmed by CT using radiography are summarised in Table 3.


© 2015 EVJ Ltd Radiographic changes were infrequently seen when


respiratory mucosa thickening without fluid accumulation was the only finding on CT. Seven of 28 horses (25%) and 6 of 24 horses (25%) had mucosa thickening without radiographic abnormalities in the rostral maxillary sinus and caudal maxillary sinus, respectively. Neither of the 2 horses with a progressive ethmoid haematoma had radiographic or endoscopic changes. Computed tomography findings consisted of a heterogeneous and well defined multiloculated structure located at the ethmoid turbinates and both sphenopalatine sinuses, with an average CT attenuation value of 110 HU (Fig 3). In both cases, the sphenopalatine sinus septum was deviated and no free fluid was observed in the sinuses. Mild distortion of the ethmoid turbinates was seen in one case. A single osteoma was seen as a well-defined mineral-dense mass superimposed over the caudal maxillary sinus on the radiographs. Computed tomography findings consisted of a well-delineated, heterogeneous and hyperattenuating mass in the caudal maxillary sinus, compressing the dorsal conchal sinus and displacing the infraorbital nerve canal medially. No dental changes were seen associated with this mass. Computed tomography features of the choanal stenosis


consisted of bilateral and symmetrical narrowing of the choana in a 22-day-old foal; the remaining aperture for airflow was 1.2 cm2. Radiographs failed to show a narrowing of the caudal nasal cavity.


Osseous and articular disease (Group B) Eleven horses were included in this group: 3 fractures, 2 osteomyelitis, 4 temporohyoid osteoarthropathy, one otitis media and one nasofrontal suture exostosis. Eight horses had a radiographic examination. One horse had also a CT dacryocystogram. The dacryocystogram was evaluated for patency of the lumen only. Fracture cases included one maxillary, one mandibular


and one case of multiple craniofacial fractures. There was agreement between radiographs and CT on the location of the mandibular fractures, although in one horse CT allowed identification of further extension of a bilateral comminuted fracture of the vertical rami of the mandibles. Radiographically, it was possible to identify fractures in the frontal and hyoid bones. Only CT allowed identification of fractures in the maxillary, lacrimal, sphenoidal, temporal and zygomatic bones. Identification of a greater number of bone fragments was also possible with CT in all the horses. In the case of multiple craniofacial fractures, CT allowed visualisation of fluid within the tympanic bulla. Osteomyelitis was observed in 2 cases using CT and radiographs, one in the mandible and the second in the temporal, mandibular, parietal, sphenoidal, frontal and zygomatic bones. In one horse, we identified more extensive


PPV (%)


64.4 (57.7–71.2) 88.9 (84.4–93.3)


NPV (%)


92.5 (88.8–96.2) 100.00 (98.5–100)


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