Systematic review of animal models of middle ear surgery

Table 1 Advantages and disadvantages of each animal model of middle ear surgery

Species	Advantages	Disadvantages
Mouse	Inexpensive to acquire and house. Genetic models of hearing loss	Small size makes access and exposure challenging
Rat	Relatively inexpensive to acquire and house. Anatomy bigger than mouse	Stapedial artery. Less docile than guinea pig
Mongolian Gerbil	Small and easy to care for. Comparatively large bulla. Naturally relatively free of otitis media. Able to form retraction pockets	Few published middle ear surgical models
Chinchilla	Inexpensive to look after. Large, thin bulla. Similar hearing frequency range to humans. Naturally relatively free of otitis media. Long lifespan	Venous sinuses within skull bones. Difficulty identifying the tympanic membrane via the transcanal route
Guinea Pig	Well established middle ear surgery and noise literature. Large tympanic cavity. Docile and easy to handle. Bigger than rodents	Middle ear infection common with age. Challenging anaesthesia. Fused incudomalleal complex. Osteoneogenesis after trauma
Rabbit	Larger anatomy than rodents. Close model of human middle ear anatomy and response to trauma	Challenging anaesthesia. Facial nerve frequently dehiscent
Cat	Well established middle ear surgery and noise literature. Anaesthesia tolerance. Behavioural outcomes easy to assess	Compared to rodents, drilling required to access structures. Many bacteria, fungi and parasites in ear canal. Patent cochlea aqueduct
Dog	Larger anatomy than cats and rodents. Behavioural outcomes easy to assess	Few published middle ear surgical models. More energetic animals require specialised care
Sheep	Docile animals. Easy to care for. Tolerate surgical procedures well. Long lifespan. Ossicles easily accessed via the transcanal route	More expensive than rodents. Mastoid adipose. Frequently dehiscent facial nerve thicker than humans
Pig	The middle ear is very similar, both in terms of structure dimensions and position to humans	Difficult middle ear access due to very different temporal bone with significant soft tissue coverage and mastoid adipose
Primate	Phylogenetically closest group of animals to humans. Mastoid air cell system and antrum present	Difficult to acquire and house. Ethical objections to research. Shallow mastoid cavity