Standardized surgical approaches to ear surgery in rats

Objective: To describe several approaches of ear surgeries for experimental studies in rats. Methods: Anesthetized rats were prepared for demonstration of various ear surgery approaches designed to optimize experimental outcomes in studies with specific goals and exposure requirements. The surgical approaches included the posterior tympanum, superior tympanum, inferior tympanum and occipital approaches. Results: The middle ear cavity and inner ear were successfully exposed from different angles via the mentioned surgical approaches. For example, electrode placement for recording of cochlear bioelectric responses was easily achieved through the posterior tympanum or inferior tympanum approach. Alternatively, drug delivery or gene transfection via round window membrane was most easily accomplished using the posterior tympanum approach. Cochlear perfusion of protective or ototoxic drugs was best performed using the inferior tympanum approach. Ossicular chain interruption to induce a prolonged conductive hearing loss was readily achieved using a superior tympanum approach. Lastly, surgical destruction of the endolymphatic sac to induce experimental endolymphatic hydrops was readily performed via an occipital surgical approach. Conclusion: These standardized surgical approaches can be applied in scientific studies of the ear with different purposes covering electrophysiology, conductive hearing loss, intra-cochlear drug perfusion and experimental studies relevant to Meniere's disease.