TY - JOUR
T1 - Factors associated with hearing loss in a normal-hearing guinea pig model of hybrid cochlear implants
AU - Tanaka, Chiemi
AU - Nguyen-Huynh, Anh
AU - Loera, Katherine
AU - Stark, Gemaine
AU - Reiss, Lina
N1 - Funding Information:
This study was funded by a NIH-NIDCD grant P30DC010755 , a NCRR grant KL2RR024141 , and a NIH-NIDCD grant P30DC005983 to the Oregon Hearing Research Center (OHRC). The authors thank Yehoash Raphael and his lab members at Kresge Hearing Research Institute for cochlear histology training; Dennis Trune for cochlear histology consultation and for helpful comments on the manuscript, Xiao-Rui Shi and their lab members at OHRC and Dalian Ding at State University of New York at Buffalo for cochlear histology consultation; Paul Abbas and Carolyn Brown at the University of Iowa, and Manuel Don and Mickey Waring for electrophysiology consultation; and John Brigande and his lab members at the OHRC in assistance in cochlear imaging. The authors also thank Michael Reiss for help with custom cochlear implant assembly design; Richard Salvi at State University of New York at Buffalo for providing information for the custom-made animal restraint; David Wozny for building the restraint; Frank Risi at Cochlear for assistance with obtaining external cochlear implant components; Guang-Di Chen at State University of New York at Buffalo for providing ABR loudspeakers; Edward Porsov and Fangyi Chen at OHRC for troubleshooting equipment problems; Judy Jin for assistance in statistical analysis.
PY - 2014/10
Y1 - 2014/10
N2 - The Hybrid cochlear implant (CI), also known as Electro-Acoustic Stimulation (EAS), is a new type of CI that preserves residual acoustic hearing and enables combined cochlear implant and hearing aid use in the same ear. However, 30-55% of patients experience acoustic hearing loss within days to months after activation, suggesting that both surgical trauma and electrical stimulation may cause hearing loss. The goals of this study were to: 1) determine the contributions of both implantation surgery and EAS to hearing loss in a normal-hearing guinea pig model; 2) determine which cochlear structural changes are associated with hearing loss after surgery and EAS. Two groups of animals were implanted (n=6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no direct acoustic or electric stimulation during this time frame. A third group (n=6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem response thresholds were followed over time at 1, 2, 6, and 16kHz. At the end of the study, the following cochlear measures were quantified: hair cells, spiral ganglion neuron density, fibrous tissue density, and stria vascularis blood vessel density; the presence or absence of ossification around the electrode entry was also noted. After surgery, implanted animals experienced a range of 0-55dB of threshold shifts in the vicinity of the electrode at 6 and 16kHz. The degree of hearing loss was significantly correlated with reduced stria vascularis vessel density and with the presence of ossification, but not with hair cell counts, spiral ganglion neuron density, or fibrosis area. After 10 weeks of stimulation, 67% of implanted, stimulated animals had more than 10dB of additional threshold shift at 1kHz, compared to 17% of implanted, non-stimulated animals and 0% of non-implanted animals. This 1-kHz hearing loss was not associated with changes in any of the cochlear measures quantified in this study. The variation in hearing loss after surgery and electrical stimulation in this animal model is consistent with the variation in human patients. Further, these findings illustrate an advantage of a normal-hearing animal model for quantification of hearing loss and damage to cochlear structures without the confounding effects of chemical- or noise-induced hearing loss. Finally, this study is the first to suggest a role of the stria vascularis and damage to the lateral wall in implantation-induced hearing loss. Further work is needed to determine the mechanisms of implantation- and electrical-stimulation-induced hearing loss.
AB - The Hybrid cochlear implant (CI), also known as Electro-Acoustic Stimulation (EAS), is a new type of CI that preserves residual acoustic hearing and enables combined cochlear implant and hearing aid use in the same ear. However, 30-55% of patients experience acoustic hearing loss within days to months after activation, suggesting that both surgical trauma and electrical stimulation may cause hearing loss. The goals of this study were to: 1) determine the contributions of both implantation surgery and EAS to hearing loss in a normal-hearing guinea pig model; 2) determine which cochlear structural changes are associated with hearing loss after surgery and EAS. Two groups of animals were implanted (n=6 per group), with one group receiving chronic acoustic and electric stimulation for 10 weeks, and the other group receiving no direct acoustic or electric stimulation during this time frame. A third group (n=6) was not implanted, but received chronic acoustic stimulation. Auditory brainstem response thresholds were followed over time at 1, 2, 6, and 16kHz. At the end of the study, the following cochlear measures were quantified: hair cells, spiral ganglion neuron density, fibrous tissue density, and stria vascularis blood vessel density; the presence or absence of ossification around the electrode entry was also noted. After surgery, implanted animals experienced a range of 0-55dB of threshold shifts in the vicinity of the electrode at 6 and 16kHz. The degree of hearing loss was significantly correlated with reduced stria vascularis vessel density and with the presence of ossification, but not with hair cell counts, spiral ganglion neuron density, or fibrosis area. After 10 weeks of stimulation, 67% of implanted, stimulated animals had more than 10dB of additional threshold shift at 1kHz, compared to 17% of implanted, non-stimulated animals and 0% of non-implanted animals. This 1-kHz hearing loss was not associated with changes in any of the cochlear measures quantified in this study. The variation in hearing loss after surgery and electrical stimulation in this animal model is consistent with the variation in human patients. Further, these findings illustrate an advantage of a normal-hearing animal model for quantification of hearing loss and damage to cochlear structures without the confounding effects of chemical- or noise-induced hearing loss. Finally, this study is the first to suggest a role of the stria vascularis and damage to the lateral wall in implantation-induced hearing loss. Further work is needed to determine the mechanisms of implantation- and electrical-stimulation-induced hearing loss.
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U2 - 10.1016/j.heares.2014.07.011
DO - 10.1016/j.heares.2014.07.011
M3 - Article
C2 - 25128626
AN - SCOPUS:84906505038
SN - 0378-5955
VL - 316
SP - 82
EP - 93
JO - Hearing Research
JF - Hearing Research
ER -