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Neoplasia of the nasal cavity and paranasal sinuses is an
uncommon condition which represented 8% of the cases from a study of 277 horses with sinonasal disorders (Tremaine and Dixon 2001a). Our study only included one case of an osteoma. Computed tomography appearance of a paranasal osteoma has not been previously described in horses. The high value of CT as a preoperative planning tool was demonstrated in all cases that underwent surgery. This was particularly evident in cases of sinonasal diseases, including dental disorders, sinus masses and fistulas. New generation multislice scanners obtain thinner slices, but mainly allow multiplanar isovolumetric reconstructions of the acquired volumetric data, increasing diagnostic confidence and determining the exact location of lesions. Impact of any lesions on adjacent structures such as the infraorbital canal and involvement of obscure compartments such as the ventral conchal sinus were also evident. The use of gantry lasers makes it possible to preoperatively localise the lesion with high precision. Dental and sinus anatomy vary with age, breed and as a normal anatomical variation between individuals (Dixon and du Toit 2010). For this reason, empirical estimates of landmarks are often incorrect (Gerard 2012). All the information provided by CT assisted the optimisation of the surgical approach and presumably allowed decreased surgical morbidity. Skull fractures are difficult to assess radiographically
because of the complex morphology of the bones and superimposition of numerous structures (Bar-Am et al. 2008). In a comparative study between radiography and CT in dogs and cats with maxillofacial trauma, it was demonstrated that CT was superior to radiography for identification of anatomic structures and traumatic injuries (Bar-Am et al. 2008). In our study, CT allowed us to identify a greater number of bone fragments and showed fractures at the maxillary, lacrimal, sphenoidal, temporal and zygomatic bones not visible radiographically. Although there was high agreement between both imaging techniques for visualising mandibular body fractures, CT may be necessary to assess the full extent of the fracture. Computed tomography provided a comprehensive
evaluation of the temporal bone, hyoid apparatus and temporohyoid articulation. Observed CT changes were similar to previous reports (Hilton et al. 2009; Pownder et al. 2010). Luxation of the temporohyoid articulation was observed in 2 of our cases. This condition was associated with focal soft tissue swelling in both cases and fluid within the tympanic bulla in one of the cases. This finding has not been previously reported in horses and a traumatic origin was suspected. Several studies have described the diagnostic utility of CT
for assessing intracranial structures (Arencibia et al. 2000; Cunilleras 2007; Sogaro-Robinson et al. 2009; Lacombe et al. 2010; Pease et al. 2011). However, apart from case reports, utility of CT for evaluation of ophthalmological conditions has not widely been described in horses (Tietje et al. 1996; Ramirez and Tucker 2004; van den Top et al. 2007; Elce et al. 2011). In our cases, CT identified retrobulbar masses, such as abscesses and tumours, intracranial invasion of a tumour and obstruction of the nasolacrimal duct. In conclusion, the equine head is a clinically important
area with complex anatomy susceptible to a large number of different conditions. A consistent description of all cases that underwent CT scan of the head in a period of 8 years was
© 2015 EVJ Ltd
performed and some conditions were described for the first time using this modality, including osteoma, choanal stenosis, stylohyoid subluxation, temporal botryomycosis, subdural haematoma, parotid mucocele and nuchal ligament bursitis. Precise diagnosis was reached using CT in all horses, particularly in cases of dental and sinonasal disorders, and CT should therefore be preferred over radiography in these conditions. Moreover, dental changes of questionable clinical significance were detected with CT. Long-term follow-up of these lesions could be the subject of further studies.
Authors’ declaration of interests No conflicts of interest have been declared.
Acknowledgements
The authors would like to thank Linda Kinney for CT image acquisitions and reconstructions as well as for her assistance with data collection. Gabriel Manso-Díaz was supported by MECD FPU fellowship (Re. AP2010-0498).
Manufacturers’ addresses
1Carestream Health, Rochester, New York, USA. 2Eklin Medical Systems Inc, Santa Clara, California, USA. 3Picker International, Highland Heights, Ohio, USA. 4Toshiba American Medical Systems Inc., Tustin, California, USA. 5Nycomed Inc., Princeton, New Jersey, USA. 6Osirix Image processing Software, Geneva, Switzerland.
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