Ear base swellings in rabbits

Chronic ear disease is a very common pathological process encountered in all small animals. A variety of different ear conditions are seen in the rabbit, and some are exacerbated by anatomical traits found in certain breeds. Chronic ear disease can cause pain and reduced quality of life in canine and feline patients. However, ear disease and its impact can go unnoticed by owners and veterinary staff because of the rabbit's ability to hide pain. Therefore, veterinary professionals should familiarise themselves with the different anatomy in rabbits, along with up-to-date medical and surgical management techniques to provide the best care for rabbits.

Unlike canine and feline patients, rabbits do not have a distinct vertical or horizontal ear canal. The external ear possesses cartilaginous plates and a blind-ending diverticulum which is separated by the tragus. The canal itself attaches to the acoustic meatus of the tympanic bulla. In dogs and cats, the meatus is positioned horizontally, whereas this is vertically orientated in the rabbit (Meredith, 2014). In all species, the acoustic meatus leads to the tympanic membrane, which separates the external canal and middle ear. In rabbits, unlike dogs and cats, the rounded tympanic bulla does not project beyond the occipital bone, and the wall of the bulla is much thicker, particularly on the lateral aspect. The bulla is closely associated with the facial nerve that emerges from the stylomastoid foramen, as this nerve travels across the ventral aspect of the lateral wall. The bulla cavity is divided into two compartments called the epitympanic recess and the tympanic sinus (Mancinelli and Lennox, 2017). The tympanic recess is in close association with the jugular foramen and cranial nerves IX, X and XI, which are the glossopharyngeal, vagus and accessory nerves respectively (Mancinelli and Lennox, 2017).