Epsilon Archive for Student Projects

Abstract

This study aimed to evaluate whether there are size differences in the external ear canal and tympanic sinus between groups of healthy domestic rabbits with lop versus erect ear conformation. The hypothesis was that lop-eared rabbits have a narrower external ear canal (I), and a smaller tympanic sinus (II). A retrospective study was conducted using medical records from the University Animal Hospital (2021–2024) of rabbits with at least one healthy ear, that underwent CT imaging of the skull. Measurements of the tympanic bulla (length, width, height) and external ear canal (cross-sectional circumference at four different points) were obtained from multiplanar CT reconstructions. Statistical analysis was performed using independent samples t-tests (p < 0.05), with outliers identified by the interquartile range method. Twenty rabbits with lop-ear conformation (Group L) and eighteen with erect-ear conformation (Group E-a) were compared, from a total of 38 rabbits. Ears with lop conformation showed a statistically significant smaller minimal crosssectional circumference (p= <0.001) and a narrower lumen at the midpoint (p= <0.001) of the cartilaginous external ear canal compared to erect ears. Thus, the first hypothesis was confirmed, lop-eared rabbits indeed had a narrower external ear canal than erect-eared rabbits in this study. This study found no significant difference in the comparison of tympanic bulla size and crosssectional circumference of the bony external ear canal between the groups. Overall, these findings contribute to the understanding of breed-related anatomical variations that could be a central factor in predisposing some rabbits to otitis media and externa.