Marek Polak

Outcomes of treatment of partial deafness with cochlear implantation: a DUET study.

Objectives: To compare speech test performance of adults with partial deafness cochlear implantation (PDCI) with that of adults with cochlear implant (CI). Based on the results, our objective is to determine the efficacy of the two applications of cochlear implantation, the first characterized by a shallow electrode insertion and preservation of low‐frequency natural hearing for partial deafness, and the second characterized by a very deep electrode insertion used in subjects with severe to profound deafness. All the PDCI participants in this study were fitted with a recently upgraded DUET Hearing System from Med‐El Corporation, Innsbruck, Austria.

Cochlear Implants in Children--A Review

Over the past two decades, cochlear implantation has become a widely accepted treatment of deafness in children. Over 20,000 children have received cochlear implants worldwide. Hearing, language and social development outcomes have been positive. We review current issues in cochlear implantation, candidacy, evaluation, surgery, habilitation, ethics and outcomes.

Pattern of hearing loss in a rat model of cochlear implantation trauma

Hypothesis: Trauma caused by cochlear implant electrode insertion is attributable to the combination of direct physical trauma and the delayed cell death of oxidative stress-injured auditory sensory cells. Background: Histologic evaluation of cochlear implant electrode trauma has demonstrated that the extent of sensory cell losses is proportional to the degree of injury. However, the impact of delayed oxidative stress within injured cochlear tissues and the progressive loss of injured hair cells by way of apoptosis are at present unknown. Methods: Laboratory rats were evaluated for hearing acuity before and after electrode insertion, before and after round window membrane incision only. Hearing was measured before trauma or incision and over the next 7 days. Objective measurements of hearing function were distortion products of otoacoustic emissions (DPOAEs) in the frequency range of 2 to 32 kHz and tone-burst (i.e., 4-32 kHz) evoked auditory brain stem responses (ABRs). Results: For the experimental cochleae, there were progressive increases in ABR thresholds and decreases in ABR amplitudes. The amplitude of the DPOAEs in the experimental cochleae also showed progressive decreases. For the contralateral control and round window membrane surgical control ears, there were no significant changes in either DPOAE or ABR thresholds. Conclusion: These results document a progressive loss of hearing acuity postimplantation and strongly suggest that electrode insertion trauma generated oxidative stress within injured cochlear tissues.

D-JNKI-1 treatment prevents the progression of hearing loss in a model of cochlear implantation trauma.

Hypotheses: 1) Hearing loss caused by electrode insertion trauma has both acute and delayed components; and 2) the delayed component of trauma-initiated hearing loss can be prevented by a direct delivery of a peptide inhibitor of the c-Jun N-terminal kinase cell death signal cascade, that is, D-JNKI-1, immediately after the electrode insertion within the cochlea. Background: Acute trauma to the macroscopic elements of the cochlea from electrode insertion is well known. The impact of trauma-induced oxidative stress within injured cochlear tissues and the efficacy of drugs (e.g., D-JNKI-1) to prevent apoptosis of damaged hair cells is not well defined. Methods: Hearing function was tested by pure-tone evoked auditory brainstem responses (ABRs) and distortion products of otoacoustic emissions (DPOAEs). D-JNKI-1 in artificial perilymph (AP) or AP alone was delivered into the scala tympani immediately after electrode trauma and for 7 days. Controls were nontreated contralateral and D-JNKI-1-treated ears without electrode insertion trauma. Results: There was no increase in the hearing thresholds of either the contralateral control ears or in the D-JNKI-1 without trauma animals. There was a progressive increase in ABR thresholds and decrease in DPOAE amplitudes after electrode insertion trauma in untreated and in AP-treated cochleae. Treatment with D-JNKI-1 prevented the progressive increase in ABR thresholds and decrease in DPOAE amplitudes that occur after electrode insertion trauma. Conclusion: Hearing loss caused by cochlear implant electrode insertion trauma in guinea pigs has both acute and delayed components. The delayed component can be prevented by treating the cochlea with D-JNKI-1.

Ecap, Esr and Subjective Levels for Two Different Nucleus 24 Electrode Arrays

Objective: We compared behavioral judgment of maximum comfortable loudness levels (C levels) and behavioral thresholds (Ts) for straight and Contour electrode arrays with two objective thresholds, electrically elicited stapedial reflex thresholds (eSRTs) and electrically elicited compound action potential thresholds (eCAP thresholds), on experienced adult cochlear implant users. Next, we evaluated the predictive value of objective measures for the straight and Contour electrode arrays, respectively. Study Design: This is a prospective, two-group comparison study of two objective and subjective levels for two different Nucleus 24 electrode arrays. Patients: Thirty experienced adults with Nucleus 24 cochlear implant were subjects in this study. Half the subjects used the straight electrode array, and the other half used the Contour electrode array. Methods: Subjective C levels, Ts, and eSRTs were successfully identified for each active electrode. eCAP thresholds were measured on 5 representative basal, medial, and apical electrodes. Correlation and regression analyses between subjective levels and objective thresholds were performed. Results: For our study subjects, there were no significant differences between the straight and Contour electrode array in regard to stimulation requirements between C levels, Ts, and thresholds of eCAP thresholds and eSRTs. Conclusion: Both eSRTs and eCAP thresholds may be used equally for estimation of subjective levels for either straight electrode array or Contour electrode array.

Evaluation of hearing and auditory nerve function by combining ABR, DPOAE and eABR tests into a single recording session.

In this article, we describe an efficient method for testing both auditory receptor and auditory nerve function in a single recording session. Auditory receptor function is tested in response to pure tone, tone burst and click acoustic stimuli (i.e. distortion products of otoacoustic emissions, DPOAE; and auditory-evoked brainstem responses, ABR). The function of the auditory neurons and nerve is measured in response to direct electric current stimulation (i.e. electrically evoked auditory brainstem responses, eABR). All measurements were obtained from anesthetized laboratory rats during single recording sessions using hardware and software stimulation and analysis programs developed by Intelligent Hearing Systems, Miami, FL.

Facial Nerve Stimulation after Cochlear Implantation

Objectives: This study was designed to compare the incidence and nature of facial nerve stimulation (FNS) in patients receiving cochlear implants (CI) manufactured by Cochlear Corporation, Advanced Bionics Corporation, and MedEl.

Conservation of hearing and protection of hair cells in cochlear implant patients' with residual hearing

This review covers the molecular mechanisms involved in hair cell and hearing losses which can result from trauma generated during the process of cochlear implantation and the contributions of both the intrinsic and extrinsic cell death signaling pathways in producing these trauma/inflammation induced losses. Application of soft surgical techniques to conserve hearing and protect auditory sensory cells during the process of cochlear implantation surgery and insertion of the electrode array during the process of cochlear implantation are reviewed and discussed. The role of drug therapy and mode of drug delivery for the conservation of a cochlear implant patients residual hearing is presented and discussed. Anat Rec, 2012.

Further prospective findings with compound action potentials from Nucleus 24 cochlear implants

The purpose of this study was to gain greater understanding of compound action potential (CAP) specific characteristics including: slope of the growth function, P1-N1 amplitude, threshold and latencies of P1 and N1 measured in cochlear implant users. Experienced adult subjects underwent behavioral threshold (T) measurement and electrically elicited stapedial reflex (eSR) recording, followed by CAP measurements on six selected electrodes. Based on the electrically elicited stapedial reflex threshold (eSRT), maximum stimulation level for each measured electrode was set. Relationships among the three thresholds of the above measures and maximum CAP P1-N1 amplitude and slope of the growth function were statistically evaluated for each measured electrode. Threshold of the CAP response showed relationships of similar strength with eSRT and T (r=0.69 and 0.61, respectively). For both slope of the growth function and CAP P1-N1 amplitude, a statistically significant relationship with cochlear place was found. Both specific characteristics of CAP measurement for the most apical electrodes were roughly double those for the most basal electrode (alpha=0.05). This may be partially explained by cochlear anatomy and is consistent with prior mammalian and human studies showing increasing density and survival of spiral ganglion cells in the regions corresponding to intracochlear electrode placement from basal to apical electrodes (90-360 degrees ).

Mild hypothermia protects auditory function during cochlear implant surgery

Objective/Hypothesis: Loss of auditory function after cochlear implant (CI) electrode insertion occurs in two stages in the laboratory rat. An immediate loss is followed by a progressive loss over 7 days. Similar stages of acute and progressive neuronal loss occur after trauma in the central nervous system where hypothermia has been shown to have a protective effect. We hypothesize that hypothermia has a similar protective effect against loss of auditory function caused by CI electrode insertion trauma.