Audiological and Histopathologic Evaluation of the Ototoxic Effect of Castellani's Solution

To clarify the ototoxic effects of Castellani solution by using histopathologic and audiological evaluations together, as contradictory results have been presented in the literature.

Castellani's solution is effective in treating disorders of the external auditory canal, particularly fungal infections. However, in cases of perforation of the eardrum, it can pass into the middle ear and affect the cochlea or vestibular system adversely.

Animals were divided into 4 groups: A: control; B: distilled water; C: Castellani's solution; and D: a solution of 70% isopropyl alcohol and 2% chlorhexidine. After the baseline hearing thresholds were recorded using auditory brainstem responses (ABRs) at 8, 16, 24, and 32 kHz, 0.03 mL of the respective substances were injected intratympanically 3 times at 2-day intervals in groups B, C, and D. Group A underwent tympanic membrane perforation using a syringe. ABRs were repeated on days 7 and 21. All animals were then sacrificed and their temporal bones were prepared for a histologic examination of the cochlea.

ABRs conducted on days 7 and 21 after the intratympanic intervention revealed total hearing loss in groups C and D, whose hearing levels were significantly lower than those of group A. Histopathologic evaluation revealed cytoplasmic vacuolization and severe atrophy of marginal, basal, and intermediate cells in groups C and D, as well as loss and degeneration of outer hair cells and supporting cells.

Due to its potential ototoxic effects and risk of passing into the middle ear, Castellani's solution should be used with extreme caution in cases of tympanic membrane perforation.