The Rat Eustachian Tube: Anatomical, Histological and Radiological Findings

Abstract

Background and purpose: Fluoroscopic Eustachian tube balloon dilation has been considered as an effective treatment for Eustachian tube dysfunction. However, many questions regarding the mechanism, recurrence and safety issues, and histological changes remains unclear. We hypothesized that a rat E-tube model could help to solve those questions. The purpose of our study was to investigate the anatomy, histology and radiology of the rat E-tube. Materials and methods: A total of 15 male Wistars rats were used in this study: 5 for anatomical study, 5 for histological analysis, and 5 for tubography. Both ears of each rat were used in our study, so a total of 10 E-tubes were available for each study. Five rats were sacrificed, decapitated and micro-dissected to describe the anatomy of the E-tube. The full length, length of the bony portion, diameter of the tympanic orifice and other parameters of the E-tube were measured. Another five rats were sacrificed, and the coronary and longitudinal sections of E-tube were obtained to study the histology of E-tube. For the remaining five rats, the Eustachian tubography was carried out using a new trans-tympanic membrane (trans-TM) approach. The procedure time was measured from the insertion of the guidewire introducer to the removal of the micro-catheter after injection of contrast medium. Results: The rat E-tube consisted of bony portion and membranous portion. The bony portion was covered by both cartilage and bone, while the membranous portion had no coverage of the cartilage or bone. The diameter and the full length of the rat E-tube were 3.28 mm ± 0.26 mm and 4.96 mm ± 0.41mm, respectively. The diameter of the tympanic orifice was 1.18 mm ± 0.10mm. The E-tube was lined by pseudostratified ciliated epithelium with goblet cells. The tubography was successfully performed in all rats using a trans-TM approach. No procedure-related complications occurred. The mean procedure time was 4.7 minutes. From Eustachian tubograms, the E-tube, tympanic cavity and nasopharynx were clearly identified. Conclusion: In the present study, we described the anatomical, histological and radiological findings of the rat E-tube. The tubography was performed successfully using a trans-TM approach. These findings may be valuable for the studies of the Eustachian tube dysfunction in the future. Keywords: Eustachian Tube; Rat; Anatomy; Histology; Radiology; Eustachian tubography