EQUINE VETERINARY EDUCATION / AE / MAY 2019
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a)
b)
Fig 1: The medial aspect of the right side of an equine head following excision of the nasal septum, the medial wall of the dorsal and ventral nasal conchae, and the medial wall of both dorsal and ventral conchal bullae before a) and after b) the placement of stainless steel wires.
laterally and caudally without being entirely excised. The medial walls of the dorsal and ventral conchae were sharply excised and removed to expose the DCB and VCB. Stainless steel wire was then cut and moulded to fit inside the DV perimeter of the DCB and VCB, thus highlighting their internal walls (Fig 1). Different thickness wire was used to allow differentiation between the left and the right bullae on subsequent radiographs: 14 gauge stainless steel wire was used for the DCB and VCB on the right side and 20 gauge stainless steel wire was used for both bullae on the left side. The nasal septum was replaced in its original position, the left and right halves of the heads were then joined together as previously described and the same five radiographic projections were repeated. The radiographic appearance of the bullae was
subjectively evaluated taking into consideration the shape, symmetry and characteristics of the DCB and the VCB separately, using a DICOM image processing application (OsiriX)4. The rostral and caudal anatomical limits of the bullae were assessed in relation to the cheek teeth on the appropriate straight lateral projection by extending a line perpendicular to the horizontal plane of the palatine bone, dorsally, to touch both the rostral and the caudal edge of each bulla, and then recording which maxillary cheek tooth was transected by each of these lines (Fig 2). To provide more specific landmarks for the position of the bullae, the maxillary cheek teeth were subdivided into rostral and caudal halves that included the corresponding rostral and caudal tooth roots. The lines were drawn on both plain radiographs and radiographs with wire in place and the measurements were repeated twice for accuracy. The acquisition of the radiographs, the sharp dissection of
the heads and the analysis of the data were performed by the same operator; therefore this was not a blinded study.
Results
Equine heads of seven horses and three ponies, all of unknown sex and breed were obtained. Age categories included: 0–5 years (n = 2), and >5 years (n = 8).
Descriptive morphology and anatomical limits of the bullae The nasal conchal bullae were visible as roughly oval radiolucent structures, enclosed within a thin radiopaque wall and with a lumen divided into small cells by a variable number of thin, radiopaque, roughly vertically orientated bony septae.
Laterolateral radiographic projections Plain radiographs The rostral limits of the bullae were identifiable on plain radiographs in all the mature horses’ heads included in the study. The DCB was irregularly oval shaped in all the equine heads, with the rostral extremity subjectively thinner (dorsoventrally) than the caudal extremity. The dorsal border was identifiable as a thin radiopaque line running parallel with the dorsal nasal meatus and the nasal bone. Caudally, the bulla was adjacent to the wall of the dorsal conchal sinus (DCS), whilst rostrally the DCB elongated into a well-defined
band with soft tissue opacity that extended between the air- filled rostral limit of the DCB and the caudal aspect of the nasoincisive notch, which was consistent with the mucosal fold observed on dissection (Fig 3). The VCB was always subjectively smaller in size than the
DCB but also approximately oval in shape with its dorsal border running parallel with the radiolucent line correlating to the middle nasal meatus. The bulla was continued rostrally and dorsally by a well-defined soft-tissue opacity band that was consistent with the thick mucosal fold observed on dissection (Fig 3).
Radiographs with wire in place Repeat radiographs after the placement of stainless steel wires confirmed the rostral limits of the DCB in seven horses and two ponies and the caudal limits of the DCB in all the equine heads. The VCB is positioned medial to the maxillary sinuses. On
lateral radiographs, the VCB was positioned rostral to the rostral limit of the rostral maxillary sinus (RMS) in 40% of the cases, but it was partially superimposed on the rostral aspect of the RMS in the remaining 60% of the heads. On plain lateral radiographs, the rostral limits of the VCB could be correctly recognised in 16/ 20 bullae (as confirmed using radiographs with the wire in place), while the caudal limits were more difficult to delineate precisely on plain radiographs and could only be correctly identified in 8/20 VCB.
Latero30°dorsal-lateroventral oblique projections The dorsal border of the DCB was identifiable in six of the horses’ heads and in none of the ponies and its visualisation was made more challenging due to the presence of multiple lines of superimposition emanating from the contralateral bullae and nasal meatuses. The rostroventral border of the VCB was identifiable in only four heads, all of which were of horses aged >5 years (Fig 4).
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