Pattern Of Hearing Loss In A Rat Model Of Cochlear Implantation Trauma

Eshraghi, Adrien A.; Polák, Marek; He, Jianbin; Telischi, Fred F.; Bałkany, Thomas J.; Water, Thomas R. Van De

doi:10.1097/01.mao.0000169791.53201.e1

Cited by 81 publications

(71 citation statements)

References 21 publications

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“…In the rat, Eshraghi et al [2005] found an immediate frequency-independent hearing loss of approximately 30 dB, increasing to 50 dB over the subsequent month following the insertion and immediate removal of a rigid implant electrode. These researchers have reported limited data from guinea pigs receiving the same cochlear trauma, which reveals a somewhat lower hearing loss of on average 15.6 dB, increasing by another 13.6 dB through a progressive hearing loss.…”

Section: Discussionmentioning

confidence: 99%

“…Surgery may cause unique types of inner ear trauma, including drilling and hydraulic pressure trauma, loss of perilymph and direct and sudden injury to inner ear structures. A rat model of cochlear implant trauma, created by the insertion and immediate withdrawal of a 'model' cochlear implant electrode, is characterized by an immediate followed by a progressive hearing loss [Eshraghi et al, 2005]. With this model, both the immediate and the delayed hearing loss were diminished by hypothermia, and in a guinea pig model the delayed hearing loss was reduced by a week-long perfusion of the scala tympani with the antiapoptotic agent D-JNKI-1 [Eshraghi et al, , 2007 .…”

Section: Introductionmentioning

confidence: 99%

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Effects of Round Window Dexamethasone on Residual Hearing in a Guinea Pig Model of Cochlear Implantation

James

Eastwood²,

Richardson³

et al. 2007

Audiol Neurotol

132

152

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To study electric acoustic stimulation, we have developed a model of guinea pig cochlear implantation via a cochleostomy. Thirty minutes prior to implantation, a hyaluronic acid/carboxymethylcellulose bead, loaded with either dexamethasone or normal saline, was placed upon the round window membrane. Animals that did not receive beads acted as controls. Pure-tone auditory brainstem response thresholds were estimated before and after electrode insertion, and 1 and 4 weeks later. Selected cochlear histology was performed. Results: Dexamethasone could be detected in the cochlea for 24 h after cochlear implantation. Thresholds were elevated across frequencies in all animals immediately after surgery. These thresholds recovered completely at and below 2 kHz, and partially at higher frequencies by 1 week after implantation. At 32 kHz, but not the lower frequencies, the presence of dexamethasone had a significant protective effect upon hearing, which increased in magnitude over time. The protection was greatest in difficult implantations where an intractable resistance to electrode insertion was met. There was a persistent foreign body reaction at the site of implantation of saline-treated implanted ears but not in the dexamethasone-treated implanted ears. Conclusion: Short-term preoperative delivery of dexamethasone through the round window can protect residual hearing during cochlear implantation, especially during technically difficult surgery.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Round Window Dexamethasone on Residual Hearing in a Guinea Pig Model of Cochlear Implantation

James

Eastwood²,

Richardson³

et al. 2007

Audiol Neurotol

132

152

View full text Add to dashboard Cite

show abstract

“…It remains unclear if the onset of post-operative hearing loss is immediate or occurs over hours to days, although Adunka et al [49] documented preserved cochlear microphonics immediately after cochlear implant insertion in a patient who subsequently developed a profound hearing loss in the operated ear, suggesting that ‘factors other than immediate changes induced by implant insertion were likely responsible’. There are several mechanisms by which hearing loss may progress rapidly, including oxidative stress to the hair cells [34,39,50,51,52,53,54,55] (which has been observed at regions distant to the site of physical trauma), inflammation [34,36,56,57,58,59,60,61], loss of the endocochlear potential though disruption of the lateral cochlear wall [55,62,63,64] and potassium toxicity through admixing of the perilymph and endolymph due to disruption of the basilar or Reissner’s membrane [65]. The endocochlear potential can recover following some types of trauma, such as ototoxicity [62,63], as can the putative membranous tears tentatively implicated with endolymphatic hydrops, leading to an improvement in hearing.…”

Section: Discussionmentioning

confidence: 99%

Targeted Therapy of the Inner Ear

et al. 2009

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Background: There is experimental evidence that targeted delivery of steroids to the inner ear can protect hearing during cochlear implant surgery. The best protection appears to be achieved through pre-treatment of the cochlea, but the time period required for treatment is long compared with the duration of surgery, and needs further optimization. The stability of hearing thresholds is determined over a 3-month period after hearing preservation cochlear implantation. Methods: Adult guinea pigs were implanted with a miniature cochlear implant electrode, and pure tone auditory brainstem response (ABR) thresholds were estimated in response to pure tones of 2–32 kHz immediately after surgery and at 1 week, 1 month and 3 months. Spiral ganglion cell (SGC) densities were estimated from mid-modular histological sections of the cochlea. Thirty minutes prior to implantation, a polymeric sponge (Seprapack^TM, Genzyme) was loaded with either a 2% solution of dexamethasone phosphate or normal saline (control) and placed onto the round window. Results: Implantation was associated with an immediate elevation in thresholds across frequencies, with a full recovery below 2 kHz over the next week and a partial recovery of thresholds at higher frequencies. These thresholds remained unchanged for the next 3 months. There was an immediate and sustained reduction in the elevation of thresholds at 32 kHz in dexamethasone-treated animals. SGC densities were greater in steroid-treated animals than controls in the basal turn of the cochlea (at the region of implantation) 3 months after implantation. Conclusion: It is concluded that ABR thresholds remain stable for 3 months after cochlear implantation in the guinea pig, and that local application of steroids to the inner ear prior to implantation is an effective method of preserving SGC populations when there is residual hearing at the time of implantation.

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“…When a delayed elevation of hearing thresholds does occur, it is thought to be due to intracochlear infection, acute inflammatory changes within the inner ear or healing by fibrous tissue formation and/or new bone growth. Recently, there has been experimental evidence to suggest that one mechanism associated with delayed hearing loss may be oxidative stress [Eshraghi et al, 2005]. RW perforation does not permanently affect hearing and the spontaneous healing of the membrane may make it a good alternative to cochleostomy for direct intracochlear perfusion [Lamm et al, 1986].…”

Section: Accessing Cochlear Fluidsmentioning

confidence: 99%

Inner Ear Therapy for Neural Preservation

2006

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A gradual loss of auditory neurons often occurs following sensorineural hearing loss. Since the cochlear implant must stimulate the remaining auditory neuron population, it would be beneficial to preserve as many auditory neurons as possible. Neurotrophic factors protect auditory neurons from degradation after sensorineural hearing loss in experimental animals, but have not yet been translated into the clinical setting. Current experimental and clinical techniques for drug delivery to the inner ear are examined in this review, covering the routes for drug delivery to the cochlea and the delivery systems used to introduce them. Duration of treatment, drug diffusion, effectiveness and safety are discussed with references to how they may be translated to the implementation of neurotrophic factor treatment for neural preservation.

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Pattern Of Hearing Loss In A Rat Model Of Cochlear Implantation Trauma

Abstract: These results document a progressive loss of hearing acuity postimplantation and strongly suggest that electrode insertion trauma generated oxidative stress within injured cochlear tissues.

Cited by 81 publications

References 21 publications

Effects of Round Window Dexamethasone on Residual Hearing in a Guinea Pig Model of Cochlear Implantation

Effects of Round Window Dexamethasone on Residual Hearing in a Guinea Pig Model of Cochlear Implantation

Targeted Therapy of the Inner Ear

Inner Ear Therapy for Neural Preservation

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