Epithelial migration on the canine tympanic membrane

Epithelial migration (EM) is a process that serves as a self-cleaning and repair mechanism for the ear canal and tympanic membrane (TM). Epithelial migration has been evaluated in humans and several other species, but not in dogs. The objective of this study was to determine the rate and pattern of EM on the TM in clinically normal laboratory dogs. Eighteen dogs were anaesthetized, and three drops of waterproof drawing ink were placed on two sites of the pars tensa (PT) and one on the pars flaccida (PF). Images were recorded with a video otoscope and digital capture system. Each dog was evaluated and images were recorded every 6-8 days for four evaluations. Migration pattern analysis and EM rate calculation were performed with image-processing software. Descriptive statistics for EM rate (mean, SD, 95% confidence interval) were calculated for all ink-drop locations on the TM (PT1, PT2 and PF) at each time point. No significant differences in the mean EM rates were identified between right and left ears of the fox hounds breeds (beagle or fox hound), or locations PT1 and PT2. The mean overall EM rates (± SD) were 96.4 (± 43.1) and 225.4 (± 128.1) μm/day for the PT and PF, respectively. All ink drops moved outwards, the majority in a radial direction, from the original location to the periphery of the TM. The ink-drop placement method used in this study can be used in future studies to determine the EM rate of the canine TM.