EQUINE VETERINARY EDUCATION Equine vet. Educ. (2018) 30 (9) 475-476 doi: 10.1111/eve.12720
Critically Appraised Topic Best way to assess the sphenopalatine sinus
V. J. Tannahill* School of Veterinary Sciences, University of Bristol, Langford, Bristol, UK. *Corresponding author email:
victoria.tannahill@bristol.ac.uk
Summary
Background The sphenopalatine (SP) sinuses communicate with the caudal maxillary sinuses and are in close apposition to the ethmoturbinates and cranium. Multiple pathologies of the SP sinus are reported, but pathology in this location can be challenging to diagnose. Radiographs of the region are difficult to interpret due to the superimposition of multiple structures. Recently, computed tomography (CT) has become preferable for detailed diagnosis of sinus disorders. Surgical access to the SP sinuses is limited and therefore accurate diagnosis can influence treatment options and improve outcomes.
Search strategy A PICO (population-intervention-comparison-outcome) question was constructed: in horses with sphenopalatine sinus disease (P), is computed tomography (I) more useful than radiography (C) in attaining a diagnosis (O)? The CAB Abstracts database was searched using the following terms: • (horse* OR equine) AND sphenopalatine • (horse* OR equine) AND sinus AND radiograph* • (horse* OR equine) AND sinus AND (computed tomography OR CT)
Quantity of evidence Screening of the search results identified ten relevant papers. One was a combined observational and retrospective study, five were retrospective studies and four were case reports.
Quality of evidence Only Manso-Dıaz et al. (2015) compared radiography with CT for all types of SP sinus disease. One further article by Tucker et al. (2016) included all cases of SP sinus disease, but only CT was performed on clinical cases. The remaining papers only addressed radiography, or compared radiography with CT for one particular SP sinus pathology. Manso-Dıaz et al. (2015) discussed the role of equine
head CT. A total of three of 18 horses (17%) diagnosed with SP sinus disease on CT also had a positive radiographic diagnosis. In their cadaveric study, Tucker et al. (2016) compared CT
images, plain radiographs and contrast radiographs of 10 heads. The SP sinus was readily identifiable on CT images, but not on plain radiographs. Following instillation of contrast material, the borders of the SP sinus were appreciated radiographically, but retrospective analysis of the plain radiographs still failed to identify the SP sinus. Notably, in 14 clinical cases of SP disease, CT was unable to differentiate between SP sinus pathologies on the basis of attenuation.
A study of 277 horses with sinonasal disease (Tremaine
and Dixon 2001) identified a soft tissue opacity in the area of the ethmoturbinates or SP sinus in 12 of 21 cases (57%) with progressive ethmoidal haematoma (PEH) of the SP sinus. Similarly, Gibbs and Lane (1987) documented one case of PEH involving the SP sinus, but it was not identified radiographically. A significant limitation of these two studies is the quality of film radiographs compared with modern digital systems; if the studies were repeated nowadays, the sensitivity of this modality may be greater. In the study by Textor et al. (2012) of 16 horses with PEH,
the SP sinus was involved in six cases. A mass was identified radiographically in 15 cases, but in five of these the anatomic location determined by radiography was incorrect. Also, bilateral disease was only diagnosed in two of eight horses in which it occurred; half of the undetected cases involved the SP sinus. Cissell et al. (2012) identified a mass on radiographs of all
15 cases of sinonasal neoplasia, but the accuracy of mass location varied by sinus compartment, with radiographs being least sensitive for the SP sinus (0/5 cases). The authors also commented that contrast-enhanced CT in two horses helped to differentiate the tumour margins from sinus fluid and normal adjacent soft tissue. In three of the case reports (Smith and Perkins 2009;
Kafarnik et al. 2014; Federici et al. 2015), radiographic findings underestimated the extent of the lesion and failed to identify involvement of the SP sinus, which was subsequently diagnosed by CT. Behrens et al. (1991) documented two cases of SP sinus disease, one of which was diagnosed radiographically.
Can this evidence be applied to my clinical scenario? In summary, the sensitivity of radiography in diagnosing SP sinus disease ranges from 0–57%, whereas the sensitivity of CT is 100%, although it cannot distinguish the exact pathology present. No false diagnoses were made in any of the papers appraised, therefore the specificity for both radiography and CT may be assumed to be high.
Clinical message Based upon the evidence available, it is concluded that CT is superior to radiography in the diagnosis of SP sinus disease. It should be considered in all cases of sinus disease as the SP sinus is often involved secondarily and its involvement may reduce the prognosis (Textor et al. 2012). Radiographs are a useful screening tool for the presence of sinus disease (Cissell et al. 2012), but they often underestimate the extent of lesions, their true location and the presence of bilateral disease (Smith and Perkins 2009; Textor et al. 2012; Kafarnik et al. 2014; Federici et al. 2015). Contrast-enhanced CT may offer an advantage for outlining sinus masses (Cissell et al.
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