• Leon Chen, Clare Dean, Michele Gandolfi, Edmund Nahm, Linda Mattiace, and Ana H Kim.
• Department of Otolaryngology-Head and Neck Surgery, New York Eye and Ear Infirmary, New York, New York, USA.
• Otolaryngol Head Neck Surg. 2014 Oct 1; 151 (4): 667-74.

ObjectiveExamine prophylactic effects of dexamethasone (Dex) in retrocochlear auditory centers in a noise-induced hearing loss (NIHL) mouse model.Study DesignProspective animal study.SettingAcademic research center.Subjects And MethodsThirty-two mice were divided into control, untreated, saline (2 and 10 µL), and Dex (2 and 10 µL) groups. Dex was applied intratympanically (IT) prior to 110 to 120 dB noise over 6 hours. Auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) were performed at 1 day, 1 week, 1 month, and 2 months. Retrocochlear neuronal cells were labeled with FluoroGold and counted. Hair cells of the organ of Corti were labeled with fluorescein isothiocyanate-conjugated phalloidin and counted.ResultsAuditory brainstem response thresholds of untreated NIHL, 2 and 10 µL IT saline, and 2 and 10 µL IT Dex were 21.7 ± 2.9 dB, 20 ± 0 dB, 20 ± 5 dB, 18.3 ± 2.9 dB, and 18.3 ± 2.9 dB, respectively. At 1-day post NIHL, all groups demonstrated profound hearing loss. At 2 weeks, 2 and 10 µL Dex thresholds improved to 47.5 ± 3.5 dB and 48.8 ± 18.9 dB, respectively, whereas the untreated and saline groups remained unchanged. Mean cell counts in the cochlear nucleus (CN), superior olivary complex (SOC), and lateral lemniscus (LL) of control mice were 1483 ± 190, 2807 ± 67, and 112 ± 20, respectively. After acoustic trauma, the untreated, saline, and 2 µL Dex groups yielded decreased neuronal counts in the SOC. In contrast, the 10 µL Dex group had 1883 ± 186 (CN), 2774 ± 182 (SOC), and 166 ± 18 (LL). There was sporadic hair cell loss for all traumatized groups.ConclusionOur NIHL mouse model demonstrated dose-dependent Dex pretreatment otoprotection against NIHL with preservation of retrocochlear auditory neurons.© American Academy of Otolaryngology—Head and Neck Surgery Foundation 2014.

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