Morphological and histological changes of rabbit vocal fold after steroid injection.

Objectives/hypothesis: The purpose of this study was to investigate the morphological and histological change of vocal folds (VFs) after steroid injection in a rabbit model.

Study Design: Prospective animal study.

Setting: Tertiary academic medical center.

Subjects And Methods: Twenty-four New Zealand white rabbits were used in this study. We randomly classified rabbits into the 3 groups and triamcinolone acetonide suspension was injected to the right VF with different concentrations. Left VF was injected with the same volume of phosphate-buffered saline as control. Endoscopic evaluation was performed to measure morphological changes. The larynges were collected for histological analysis, and the VFs were stained with hematoxylin-eosin for assessing inflammatory response, glandular atrophy, and muscular atrophy and with Masson's trichrome for assessing collagen deposition.

Results: In morphological assessment, there were no differences in VF mass reduction, mucosal atrophy, and granulation formation between both VFs. Histological assessments showed no significant difference in inflammatory response, glandular atrophy, and collagen deposition between both VFs. However, there was a difference in muscular atrophy and epithelial layer thinning in steroid injected right VFs. Muscular atrophy had been completely recovered over time, but mild epithelial thinning was continued until 12 weeks. The longer exposure time and larger dose did not increase the intensity of muscular atrophy or epithelial thinning.

Conclusion: We demonstrated that the VF steroid injection resulted in no significant changes in morphology and histology of rabbit VF. However, steroid injection may induce several VF histological changes and these results are needed to be considered when treating humans.