Local dexamethasone therapy conserves hearing in an animal model of electrode insertion trauma-induced hearing loss.
OBJECTIVE
The progressive loss of hearing that develops after electrode insertion trauma (EIT) can be attenuated by local dexamethasone (DXM) therapy.


BACKGROUND
Hearing loss (HL) that develops after cochlear implant EIT occurs in two stages in laboratory animals, that is, an immediate loss followed by a progressive loss. Direct infusion of DXM into the guinea pig cochlea can attenuate both ototoxin- and noise-induced HL.


METHODS
Auditory-evoked brainstem responses (ABRs) of guinea pigs were measured for 4 frequencies (i.e., 0.5, 1, 4, and 16 kHz) before, immediately after, and more than 30 days post-EIT for experimental (EIT,EIT + artificial perilymph, and EIT + DXM) and for the contralateral unoperated cochleae of each group. An electrode analog of 0.14-mm diameter was inserted through a basal turn cochleostomy for a depth of 3 mm and withdrawn. DXM in artificial perilymph was delivered immediately post-EIT into the scala tympani via a miniosmotic pump for 8 days.


RESULTS
The ABR thresholds of EIT animals increased progressively post-EIT. Contralateral unoperated cochleae had no significant changes in ABR thresholds. Immediately post-EIT, that is, Day 0, the DXM-treated animals exhibited a significant HL at 1, 4, and 16 kHz, but this HL was no longer significant by Day 30 compared with contralateral control ears.


CONCLUSIONS
The results from immediate local treatment of the cochlea with DXM in an animal model of EIT-induced HL suggest a novel therapeutic strategy for hearing conservation by attenuating the progressive HL that can result from the process of electrode array insertion during cochlear implantation.
Eshraghi
Adrien A
AA
Cochlear Implant Research Program, University of Miami Ear Institute, Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, FL, USA.
Adil
Eelam
E
He
Jiao
J
Graves
Reid
R
Balkany
Thomas J
TJ
Van De Water
Thomas R
TR
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D001301:Audiometry, Pure-Tone; D003051:Cochlea / Q000293:injuries*; D019929:Cochlear Implantation / Q000009:adverse effects*; D003054:Cochlear Implants / Q000009:adverse effects*; D003907:Dexamethasone / Q000008:administration & dosage / Q000627:therapeutic use*; D004567:Electrodes, Implanted / Q000009:adverse effects*; D006168:Guinea Pigs; D034381:Hearing Loss / Q000209:etiology* / Q000517:prevention & control*; D015918:Infusion Pumps, Implantable; D012533:Scala Tympani
D000893:Anti-Inflammatory Agents; D003907:Dexamethasone