An anatomical study of the dorsal and ventral nasal conchal bullae in normal horses: Computed tomographic anatomical and morphometric findings.

Abstract: Infection of the dorsal nasal conchal bulla and ventral nasal conchal bulla has recently been shown to cause clinical disease in horses, but the anatomy of these 2 structures is poorly documented. Objective: To describe the anatomical features, dimensions and relationships to adjacent structures of the dorsal conchal bulla and ventra conchal bulla in normal horses using computed tomography (CT). Methods: Descriptive imaging study using cadavers. Methods: Computed tomographic images acquired from 60 equine cadaver heads that were shown to be free of sinonasal disease were categorised into 3 age groups (0-5; 6-15; >16 years old). Linear and volumetric measurements and descriptive anatomical assessments of the dorsal conchal bulla and ventral conchal bulla were produced from these CT images and the anatomical relationships between the dorsal conchal bulla and ventral conchal bulla and the adjacent structures, particularly the maxillary cheek teeth, were examined. The associations between bullae dimensions with horse ages and skull dimensions were assessed using linear regression. Results: Mean (range) dorsal conchal bulla measurements were: length 7.5 cm (4.6-14), width 1.9 cm (1.3-2.5), height 2.8 cm (1.8-4), volume 24 cm (5.9-50.5). Mean ventral conchal bulla measurements were: length 5.7 cm (2.5-8.5), width 1.6 cm (0.7-2.9), height 2.4 cm (0.8-3.7), volume 15 cm (0.4-30). In both dorsal conchal bulla and ventral conchal bulla, there were significant differences in sizes between the different age groups (smaller in younger animals). In the ventral conchal bulla, this was probably related to protrusion of the large dental alveoli of younger horses into the lateral nasal cavity. Measures of bullae size and volume were significantly associated with head size. The anatomical positions (rostro-caudal boundaries) of the dorsal conchal bulla and ventral conchal bulla were closely associated with specific maxillary cheek teeth. Conclusions: Computed tomography was a useful technique to establish the linear and volumetric dimensions of the nasal conchal bullae in normal horses. Both dorsal conchal bulla and ventral conchal bulla sizes increased with animal age. Relatively consistent anatomical relationships were shown between the rostral and caudal limits of the bullae and certain maxillary cheek teeth, which would be of diagnostic value with conventional radiography and act as landmarks in the surgical treatment of nasal bulla disease.