**1. Introduction**

The paranasal sinuses develop via evagination into the spongy bone between the external and internal plates of the cranial and facial bones [1]. Therefore, the lining of each sinus comprises of respiratory epithelium. With the exception of the lacrimal and palatine sinuses which are diverticula of the maxillary sinus, each sinus has a direct opening into the nasal cavity. One of the largest problems with sinuses is inflammation, which can be caused by numerous problems including infection and structural abnormalities, and in itself can cause pain and increased infections. Unfortunately, when inflammation occurs, the mucous membrane swells and closes the aperture, this blocks normal sinus drainage [1]. This condition may require surgical drainage. The extensive sinus system possesses considerable clinical interest, especially as it is susceptible to infection that may spread from the nose or from an alveolar abscess [2, 3]. The paranasal sinuses of sheep include the frontal, maxillary, ethmoidal, lacrimal and palatine sinuses. Ovine sinuses differ slightly to cattle, including buffalo, which have frontal, maxillary, sphenoidal, ethmoidal, lacrimal and palatine sinuses [3–5]. Camels are somewhat similar to cattle with frontal, maxillary, sphenoidal, ethmoidal, and lacrimal sinuses [6] with an additional

palatine sinus [7–9]. However, in equids, three paranasal sinuses have been recorded: the frontal, maxillary and sphenopalatine [10–12]. Computed tomography of equine, ruminant and camel heads has enabled production of detailed cross-sectional images of structures and cavities such as the brain case, paranasal sinuses and nasal cavity whilst ensuring that other anatomical structures are not superimposed [4, 6, 11, 12].
