EQUINE VETERINARY EDUCATION / AE / MAY 2019


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a)


b)


to superimposition of the mandible and cheek teeth on the majority of the DCB and the whole of the VCB. Furthermore, the area of projection of the DCB on the DV view is partially superimposed on the area of the ventral conchal sinus (Tremaine and Freeman 2007), thus the presence of fluid radiopacity visible on the DV radiographic projection is difficult to interpret. This however should not undermine the value of a DV projection in cases of suspected dental diseases and sinusitis in general, as this view can still provide useful clinical information as well as giving the opportunity to evaluate potential asymmetries in shape and radiopacity within the nasal cavity and sinuses. The extent of the radiographic overlap between ventral conchal sinus, DCS, VCB and DCB on plain DV radiographs has not been reported, and further studies would be interesting. Unfortunately, due to availability of the band-saw, the


Fig 6: Latero-lateral radiographic projections of two different cadaver equine heads with presence of fluid lines into the nasal conchal bullae. In image a) the white arrow indicates a fluid line


in the DCB. In image b) the white arrows indicate the presence of fluid lines in the DCBs and VCBs. The blue arrowheads indicate the margins of a radiopaque mass present in one of the DCBs. Excision of the medial walls of the bullae revealed the presence of blood in both equine heads and a blood clot in the left DCB of the horse head in image b). These findings were deemed to be due to post-mortem bleeding and not related to ante mortem bulla pathology.


radiographs and had to be confirmed by the presence of the wires in 60% of the cases. Generally, the caudal border extended further caudally than predicted on plain radiographs and was partially superimposed on the rostral limit of the rostral maxillary sinus in 60% of the skulls. The radiopacity of the mucosal fold rostral to the VCB was easily identified in all the heads in this study, therefore this structure may be used as a landmark in the radiographic identification of the VCB. Identification of the bullae on latero30°dorsal-lateroventral


oblique projection was more difficult than on straight radiographs due to multiple lines of superimposition and the complex architecture of the head. Most horses with


empyema of the nasal conchal bullae  paranasal sinuses present with unilateral disease (Dixon et al. 2015), thus identification of fluid lines or soft tissue opacity in the region of the bulla(e) on a straight lateral projection should be sufficient to alert the clinician to their involvement in the disease process. Although this study did not include horses with empyema of the bullae, we believe that the oblique view may be helpful to confirm which side is affected if this is not clinically apparent. The DV view was not particularly useful in the identification of the DCB and VCB as it allowed evaluation of only the caudomedial aspect of the DCB, due


cadaver heads we used in this study had been sagittally transected prior to the acquisition of plain radiographs, and this created a radiolucent gap between the two halves of the head that might have somewhat disturbed the appraisal of the DV views. Acquisition of the five plain radiographic projections before transecting the heads would have prevented this artefact. The wires were positioned in a sagittal plane in a way to highlight the dorsoventral perimeter of the bullae; thus, on DV views, the wires did not demarcate the mediolateral width of the bullae. Repositioning of the wires in the dorsal plane before the acquisition of the DV views probably would have resulted in better visualisation of at least the DCB; however, the complete excision of the medial walls of the bullae did not provide enough support for the wires to maintain their position in the dorsal plane. The rostral and caudal limits of both the DCB and the


VCB were analysed in relation to the adjacent rostral and caudal roots of the cheek teeth. As the linear dimensions (Froydenlund et al. 2015; Liuti et al. 2015) and the volume (Liuti et al. 2015) of the bullae have already been described in detail using more accurate measures than radiography, no further measurements were evaluated in the current study. The radiographic rostral and caudal limits of the bullae in relation to the cheek teeth were similar to those previously described by Liuti et al. (2015). Broadly speaking, the larger DCBs are usually located dorsal to the maxillary 07s–09s/10s, and the relatively shorter VCBs are most commonly located dorsal to the maxillary 07s–08s/09s. Some variations in contrast and radiographic definition of


the borders of both bullae were observed. The superimposition of the maxillary cheek teeth in the two heads that were age <5 years made the caudal and ventral borders of the VCB difficult to define and in one of the two cases the caudal border of the bulla was not visible at all on plain radiographs. Following dissection and wire placement, the size of the VCB in these horses was deemed to be subjectively smaller than observed in older horses. However, the sample size of this study was very small, and the cadaver heads of young horses were limited to 2/10 cases due to limited availability of young cadavers from our source. A larger number of heads aged <5 years may have provided more consistent data on size and appearance of the VCB in young horses, nevertheless similar age related variations in dimensions of the VCB have previously been described (Froydenlund et al. 2015; Liuti et al. 2015). These appear to be the result of lateral and ventral compression of the VCB by the maxillary cheek teeth apices. The generalised increased


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