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EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2019) 31 (5) 264-270 doi: 10.1111/eve.12788
Original Article
Radiographic identification of the equine dorsal and ventral nasal conchal bullae
A. E. Giavitto†* and S. Z. Barakzai‡ †Langford Equine Centre, Langford, Bristol; and ‡Equine Surgical Referrals, Cheam, Surrey, UK. *Corresponding author email:
andrea.giavitto@
gmail.com
Keywords: horse; dorsal nasal conchal bulla; ventral nasal conchal bulla; radiographic anatomy; radiographic identification; equine skull
Summary The recent understanding that pathology of the nasal dorsal (DCB) and ventral (VCB) conchal bullae can be a common and underdiagnosed cause of unilateral nasal discharge in horses, has generated new interest in these structures. The normal computed tomographic anatomy of the bullae has been described in detail; however, computed tomography facilities are still limited to referral centres, and radiography remains the primary diagnostic imaging modality for most equine practitioners. The purpose of this descriptive imaging study was to describe the radiographic anatomy and limits of both DCB and VCB in equine cadaver skulls. The heads of 10 horses (7 horses, 3 ponies) of unknown age were transected sagittally in the midline, and five radiographic projections (left and right laterolateral, left and right latero30°dorsal– lateroventral oblique and dorsoventral) of the sinuses and nasal cavities were obtained, before and after the placement of stainless steel wire moulded inside the bullae. The radiographic appearance of the VCB and DCB was evaluated on both plain and wire radiographs, assessing their anatomical limits in relation to the cheek teeth and describing the variations related to age and type of horse. The radiographs allowed correct identification of the rostral and caudal limits of the DCB and of the rostral limit of the VCB in the majority of the horse heads. Mild variations in the radiographic appearance of the bullae between horse and pony heads were noted. The laterolateral projections resulted in the best visualisation of the bullae in all the heads used in the study. This study showed that the VCB and DCB are radiographically identifiable on plain radiographs in most mature horses, and that pathology of these structures may be identifiable using radiography.
Introduction
It has recently been reported that pathology of the dorsal (DCB) and ventral conchal bullae (VCB) is a relatively common and very probably underdiagnosed cause of unilateral nasal discharge in horses (Dixon et al. 2015). The paper by Dixon et al. (2015) reported that 23% of horses with paranasal sinus disorders had involvement of either the VCB or DCB detected on computed tomographic (CT) examination, and that, in most cases, lavage of the paranasal sinuses alone would not necessarily resolve empyema of the nasal conchal bullae. Dixon et al.’s paper (2015), and two other papers by the same group describing the gross, histological (Froydenlund et al. 2015) and computed tomographic (Liuti et al. 2015) anatomy of the
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DCB and VCB have therefore created new interest in these structures from equine clinicians. Given the anatomical complexity of the head, CT is
considered to be the gold standard for imaging the equine sinonasal regions (Morrow et al. 2000; Probst et al. 2005; Brinkschulte et al. 2014; Dixon et al. 2015; Liuti et al. 2015), and the CT anatomy of the nasal conchal bullae have now been described in detail (Liuti et al. 2015). CT facilities are, however, limited to equine referral centres, and radiography remains the primary diagnostic imaging modality for most equine practices. A better knowledge of the radiographic appearance and location of these structures would therefore be helpful when dealing with cases of unilateral nasal discharge that might be associated with empyema of the nasal conchal bullae. The purpose of this study was to outline and describe the radiographic anatomy of the DCB and VCB in equine cadaver skulls and their relation to the adjacent maxillary cheek teeth.
Materials and methods
Ten equine cadaver heads were obtained from a local rendering plant. The heads were disarticulated between the occipital bone and the first cervical vertebra and had been transected sagittally in the midline using a band saw. The exact age, sex and breed of the horses were unknown; therefore, the heads were categorised into one of the following two age groups based on clinical and radiographic dental examination: 0–5 years and >5 years. The two halves of each head were reassembled by the
use of four ligatures placed between the Triadan 03s and 04s (mandibular and maxillary), around the two occipital condyles and on either side of the nasoincisive notches. With the heads resting on their mandibles, five plain radiographic projections were obtained of each head, collimating the
primary beam to include the sinuses and nasal cavities. The five projections consisted of left and right laterolateral projection, left and right latero30°dorsal-lateroventral oblique projections and a dorsoventral (DV) projection. The images were acquired using a portable POSKOM PXP-20HF PLUS X-ray unit1, using an exposure of 86 kV and 1.6 mAs for the lateral and lateral-oblique views and 96 kV, 1.6 mAs for the DV view, and a CANON CXDI-801C2 digital radiography plate linked to a Sound-Eklin Mark 1210C digital radiography system3. The ligatures were then removed and the two halves of the heads were separated. Depending on the exact location of the sagittal band saw cut, the nasal septum was present on either the left or the right side of the sagittally sectioned head. The nasal septum was sharply cut and elevated
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