Otitis: anatomy every practitioner should know.

Chronic otitis externa is a difficult, frustrating problem. Four etiologic components must be considered: primary and secondary causes and perpetuating and predisposing factors.1 Usually, these cases are complex and involve more than one component. Perpetuating factors are changes in the anatomy and physiology of the ear that occur in response to inflammation in the ear canal and the perpetuating factors already present. They are self-perpetuating, are not disease specific, and include failure of self-cleaning mechanisms and proliferative changes that create folds and stenosis of the lumen of the ear canal. Elimination of perpetuating factors often requires aggressive cleaning of the ear and long-term therapy. It is important to avoid damaging key structures while aggressively cleaning the ear. Therefore, to adequately diagnose and manage perpetuating factors, veterinarians must recognize normal ear anatomy and physiology.