Systematic review of animal models of middle ear surgery

Abstract

Animal models of middle ear surgery help us to explore disease processes and intervention outcomes in a manner not possible in patients. This review begins with an overview of animal models of middle ear surgery which outlines the advantages and limitations of such models. Procedures of interest include myringoplasty/tympanoplasty, mastoidectomy, ossiculoplasty, stapedectomy, and active middle ear implants. The most important issue is how well the model reflects the human response to surgery. Primates are most similar to humans with respect to anatomy; however, such studies are uncommon now due to expense and ethical issues. Conversely, small animals are easily obtained and housed, but experimental findings may not accurately represent what happens in humans. We then present a systematic review of animal models of middle ear surgery. Particular attention is paid to any distinctive anatomical features of the middle ear, the method of accessing the middle ear and the chosen outcomes. These outcomes are classified as either physiological in live animals, (e.g., behavioural or electrophysiological responses), or anatomical in cadaveric animals, (e.g., light or electron microscopy). Evoked physiological measures are limited by the disruption of the evoking air-conducted sound across the manipulated middle ear. The eleven identified species suitable as animal models are mouse, rat, gerbil, chinchilla, guinea pig, rabbit, cat, dog, sheep, pig and primate. Advantages and disadvantages of each species as a middle ear surgical model are outlined, and a suggested framework to aid in choosing a particular model is presented.

Keywords: Otologic surgical procedures, Middle ear, Animal models, Electrophysiology, Microscopy

Core tip: Animal models provide an invaluable insight into physiological and anatomical responses to middle ear surgical interventions. The choice of which animal model to use depends on the question which needs to be answered and on the available resources. Acute terminal experiments permit greater access and exposure of the middle ear structures, but the behavioural and long-term outcomes are not available. Chronic experiments conversely have more limited options for exposure, but allow long-term observation of tissue recovery and tolerance of the surgery. Both options are considered in this review.