Conservation of low-frequency hearing in cochlear implantation

Preservation of Residual Hearing: Long-Term Results With a Mid-Scala Electrode

OBJECTIVE

The long-term preservation of residual hearing after cochlear implantation has become a major goal over the past few years. The aim of the present study was to evaluate residual hearing in the long-term follow-up using mid-scala electrodes.

METHODS

In this retrospective, single-center study, we collected data from 27 patients who were implanted between 2014 and 2015 with residual hearing in the low-frequency range using a mid-scala electrode. Measurements of the hearing thresholds were carried out directly postoperatively (day 1 after surgery) and in the long-term follow-up 43.7 ± 6.9 months. The calculation of the extent of audiological hearing preservation was determined using the HEARRING group formula by Skarsynski.

RESULTS

Postoperative preservation of residual hearing was achieved in 69.2% of the cases in the low-frequency range between 250 Hz and 1 kHz, of which 89.5% of the patients had frequencies that suggested using electroacoustic stimulation (EAS). In the long-term follow-up, 30.8% of the patients showed residual hearing; however, 57.1% had apparently benefited from EAS.

CONCLUSION

Preservation of residual hearing is feasible in the long term using mid-scala electrodes. Postoperatively, there is over the half of patients who benefit from an EAS strategy. The long-term follow-up shows a certain decrease in residual hearing. However, these results are comparable to studies relating to other types of electrodes. Further research should be conducted in future to better evaluate hearing loss in long-term follow-up, compared to direct postoperative audiological results.

Intraoperative Measured Electrocochleography and Fluoroscopy Video to Detect Cochlea Trauma

HYPOTHESIS

Gross electrode movements detected with intraoperative, real-time X-ray fluoroscopy will correlate with fluctuations in cochlear output, as measured with intraoperative electrocochleography (ECochG).

BACKGROUND

Indications for cochlear implantation (CI) are expanding to include patients with residual hearing; however, implant recipients often lose residual hearing after CI. The objective of this study was to identify probable traumatic events during implantation by combining electrophysiological monitoring of cochlear function with simultaneous X-ray monitoring. The surgical timing of these apparently traumatic events was then investigated.

METHODS

For 19 adult patients (21 surgeries, 2 bilateral), the ECochG responses were measured during implantation of a cochlear nucleus slim modiolar electrode (CI532/CI632, Cochlear Ltd Australia Nucleus slim modiolar). Simultaneous fluoroscopy was performed, as well as a postoperative cone-beam computed tomography (CT) scan. For all patients, pre- and postoperative audiograms were recorded up to 1 year after surgery to record the loss of residual hearing.

RESULTS

Electrode insertions for 21 surgeries were successfully monitored. A drop in ECochG response was significantly correlated with reduced hearing preservation compared with patients with preserved responses throughout. Drops in the ECochG response were measured to occur during insertion, because of movement of the array after insertion was complete, including while sealing of the electrode array at the round window or coiling of the array lead within the mastoid cavity. In some patients, a reduction in cochlear output, resulting in poor ECochG response, was inferred to occur before the beginning of implantation.

CONCLUSION

The combination of perioperative ECochG measurements, microscope video, fluoroscopy, and postoperative CT scan may inform on what causes the loss of residual hearing after implantation. These findings will be used to improve the surgical procedure in future.

Towards the optimization of drug delivery to the cochlear apex: Influence of polymer and drug selection in biodegradable intracochlear implants

There is growing need for new drug delivery systems for intracochlear application of drugs to effectively treat inner ear disorders. In this study, we describe the development and characterization of biodegradable, triamcinolone-loaded implants based on poly(lactic-co-glycolic acid) (PLGA) and polyethylene glycol-poly(lactic-co-glycolic acid) (PEG-PLGA) respectively, prepared by hot-melt extrusion. PEG 1500 was used as a plasticizer to improve flexibility and accelerate drug release. The sterilization process was performed by electron beam irradiation, resulting in minimal but acceptable polymer degradation for PEG-PLGA implants. The implants have been characterized by texture analysis, differential scanning calorimetry and X-ray powder diffraction. Compared to PLGA implants, PEG-PLGA implants offer similar flexibility but with improved mechanical stability, which will ease the handling and intracochlear application. A controlled release over three months was observed for dexamethasone and triamcinolone extrudates (drug load of 10%) with similar release profiles for both drugs. PEG-PLGA implants showed an initial slow release rate over several days regardless of the amount of PEG added. Mathematical simulations of the pharmacokinetics of the inner ear based on the in vitro release kinetics indicate a complete distribution of triamcinolone in the whole human scala tympani, which underlines the high potential of the developed formulation.

Facilitating or disturbing? An investigation about the effects of auditory frequencies on prefrontal cortex activation and postural sway

Auditory stimulation activates brain areas associated with higher cognitive processes, like the prefrontal cortex (PFC), and plays a role in postural control regulation. However, the effects of specific frequency stimuli on upright posture maintenance and PFC activation patterns remain unknown. Therefore, the study aims at filling this gap. Twenty healthy adults performed static double- and single-leg stance tasks of 60s each under four auditory conditions: 500, 1000, 1500, and 2000 Hz, binaurally delivered through headphones, and in quiet condition. Functional near-infrared spectroscopy was used to measure PFC activation through changes in oxygenated hemoglobin concentration, while an inertial sensor (sealed at the L5 vertebra level) quantified postural sway parameters. Perceived discomfort and pleasantness were rated through a 0-100 visual analogue scale (VAS). Results showed that in both motor tasks, different PFC activation patterns were displayed at the different auditory frequencies and the postural performance worsened with auditory stimuli, compared to quiet conditions. VAS results showed that higher frequencies were considered more discomfortable than lower ones. Present data prove that specific sound frequencies play a significant role in cognitive resources recruitment and in the regulation of postural control. Furthermore, it supports the importance of exploring the relationship among tones, cortical activity, and posture, also considering possible applications with neurological populations and people with hearing dysfunctions.

Mild therapeutic hypothermia protects against inflammatory and proapoptotic processes in the rat model of cochlear implant trauma

OBJECTIVE

Mild therapeutic hypothermia (MTH) has been demonstrated to prevent residual hearing loss from surgical trauma associated with cochlear implant (CI) insertion. Here, we aimed to characterize the mechanisms of MTH-induced hearing preservation in CI in a well-established preclinical rodent model.

APPROACH

Rats were divided into four experimental conditions: MTH-treated and implanted cochleae, cochleae implanted under normothermic conditions, MTH only cochleae and un-operated cochleae (controls). Auditory brainstem responses (ABRs) were recorded at different time points (up to 84 days) to confirm long-term protection and safety of MTH locally applied to the cochlea for 20 min before and after implantation. Transcriptome sequencing profiling was performed on cochleae harvested 24 h post CI and MTH treatment to investigate the potential beneficial effects and underlying active gene expression pathways targeted by the temperature management.

RESULTS

MTH treatment preserved residual hearing up to 3 months following CI when compared to the normothermic CI group. In addition, MTH applied locally to the cochleae using our surgical approach was safe and did not affect hearing in the long-term. Results of RNA sequencing analysis highlight positive modulation of signaling pathways and gene expression associated with an activation of cellular inflammatory and immune responses against the mechanical damage caused by electrode insertion.

SIGNIFICANCE

These data suggest that multiple and possibly independent molecular pathways play a role in the protection of residual hearing provided by MTH against the trauma of cochlear implantation.

Anatomical Variations of the Human Cochlea Using an Image Analysis Tool

Understanding cochlear anatomy is crucial for developing less traumatic electrode arrays and insertion guidance for cochlear implantation. The human cochlea shows considerable variability in size and morphology. This study analyses 1000+ clinical temporal bone CT images using a web-based image analysis tool. Cochlear size and shape parameters were obtained to determine population statistics and perform regression and correlation analysis. The analysis revealed that cochlear morphology follows Gaussian distribution, while cochlear dimensions A and B are not well-correlated to each other. Additionally, dimension B is more correlated to duct lengths, the wrapping factor and volume than dimension A. The scala tympani size varies considerably among the population, with the size generally decreasing along insertion depth with dimensional jumps through the trajectory. The mean scala tympani radius was 0.32 mm near the 720° insertion angle. Inter-individual variability was four times that of intra-individual variation. On average, the dimensions of both ears are similar. However, statistically significant differences in clinical dimensions were observed between ears of the same patient, suggesting that size and shape are not the same. Harnessing deep learning-based, automated image analysis tools, our results yielded important insights into cochlear morphology and implant development, helping to reduce insertion trauma and preserving residual hearing.

A chemo-mechanical cochleostomy preserves hearing for the in vivo functional imaging of cochlear cells

In vivo and real-time multicellular imaging enables the decoding of sensory circuits and the tracking of systemic drug uptake. However, in vivo imaging of the auditory periphery remains technically challenging owing to the deep location, mechanosensitivity and fluid-filled, bone-encased nature of the cochlear structure. Existing methods that expose the cochlea invariably cause irreversible damage to auditory function, severely limiting the experimental measurements possible in living animals. Here we present an in vivo surgical protocol that permits the imaging of cochlear cells in hearing mice. Our protocol describes a ventro-lateral approach for preserving external and middle ear structures while performing surgery, the correct mouse positioning for imaging cochlear cells with effective sound transmission into the ear, the chemo-mechanical cochleostomy for creating the imaging window in the otic capsule bone that prevents intracochlear fluid leakage by maintaining an intact endosteum, and the release of intracochlear pressure that separates the endosteum from the otic capsule bone while creating an imaging window. The procedure thus preserves hearing thresholds. Individual inner and outer hair cells, supporting cells and nerve fibers can be visualized in vivo while hearing function is preserved. This approach may enable future original investigations, such as the real-time tracking of ototoxic drug transport into the cochleae. The technique may be applied to the monitoring of sound-evoked functional activity in multiple cochlear cells, in combination with optogenetic tools, and may help to improve cochlear implantation in humans. The cochleostomy takes ~1 h and requires experience in surgery.

The 100 Most-Cited Manuscripts in Hearing Implants: A Bibliometrics Analysis

The aim of the study was to characterise the most frequently cited articles on the topic of hearing implants. A systematic search was carried out using the Thomson Reuters Web of Science Core Collection database. Eligibility criteria restricted the results to primary studies and reviews published from 1970 to 2022 in English dealing primarily with hearing implants. Data including the authors, year of publication, journal, country of origin, number of citations and average number of citations per year were extracted, as well as the impact factors and five-year impact factor of journals publishing the articles. The top 100 papers were published across 23 journals and were cited 23,139 times. The most-cited and influential article describes the first use of the continuous interleaved sampling (CIS) strategy utilised in all modern cochlear implants. More than half of the studies on the list were produced by authors from the United States, and the Ear and Hearing journal had both the greatest number of articles and the greatest number of total citations. To conclude, this research serves as a guide to the most influential articles on the topic of hearing implants, although bibliometric analyses mainly focus on citations. The most-cited article was an influential description of CIS.

Timing of Acoustic Hearing Changes After Cochlear Implantation

OBJECTIVES/HYPOTHESIS

To determine the timing of acoustic hearing changes among hearing preservation Cochlear implant (CI) recipients. To determine differences in hearing outcomes based on device type and demographic factors. To determine if there is a relationship between the extent of early hearing loss after CI and the subsequent rate of continued hearing loss.

STUDY DESIGN

Prospective, single subject study.

METHODS

Two hundred and eleven subjects who received a hearing preservation CI were included in the study-80 Nucleus Hybrid L24 (Cochlear), 47 422/522 (Cochlear), 24 S8 (Cochlear), 14 S12 (Cochlear), 6 SRW (Cochlear), 21 SLIM J (Advanced Bionics), and 19 Flex (Med-EL). Of these, 127 were included in the subsequent analyses. Audiometric thresholds (low frequency pure-tone-averages) were collected and compared pre and postoperatively.

RESULTS

Long-term hearing preservation rates were 65% (52/80) for L24, 83% (20/24) for S8, 79% (11/14) for S12, 83% (5/6) for SRW, 54% (25/47) for 422/522, 91% (21/23) for SLIM J, and 84% (16/19) for Flex. Hearing loss was not related to device type (P = .9105) or gender (P = .2169). Older subjects (age ≥65) had worse hearing outcomes than younger subjects after initial device activation (age <65, P = .0262). There was no significant difference in rate of hearing loss over time between older and younger patients (P = .0938). Initial postoperative hearing loss was not associated with the rate of long-term hearing loss.

CONCLUSIONS

Long-term low frequency hearing preservation is possible for CI recipients and is not associated with gender or device type. Rate of hearing loss over time is not dependent on patient age. Early hearing loss after CI does not predict the rate of long-term hearing loss.

LEVEL OF EVIDENCE

3 Laryngoscope, 132:2036-2043, 2022.

Relationship Between Intraoperative Electrocochleography and Hearing Preservation

OBJECTIVES

To compare intraoperative intracochlear electrocochleography (ECochG) with hearing preservation outcomes in cochlear implant (CI) subjects.

DESIGN

Intraoperative electrocochleography was performed in adult CI subjects who were recipients of Advanced Bionics' Bionics LLC precurved HiFocus MidScala or straight HiFocus SlimJ electrode arrays. ECochG responses were recorded from the most apical electrode contact during insertion. No changes to the insertions were made due to ECochG monitoring. No information about insertion resistance was collected. ECochG drops were estimated as the change in amplitude from peak (defined as maximum amplitude response) to drop (largest drop) point after the peak during insertion was measured following the peak response. Audiometric thresholds from each subject were obtained before and approximately 1 month after CI surgery. The change in pure tone average for frequencies between 125 Hz and 500 Hz was measured after surgery. No postoperative CT scans were collected as part of this study.

RESULTS

A total of 68 subjects from five surgical centers participated in the study. The study sample included 30 MidScala and 38 SlimJ electrodes implanted by approximately 20 surgeons who contributed to the study. Although a wide range of results were observed, there was a moderate positive correlation (Pearson Correlation coefficient, r = 0.56, p < 0.01) between the size of the ECochG drop and the magnitude of pure tone average change. This trend was present for both the MidScala and SlimJ arrays. The SlimJ and MidScala arrays produced significantly different hearing loss after surgery.

CONCLUSION

Large ECochG amplitude drops observed during electrode insertion indicated poorer hearing preservation. Although the outcomes were variable, this information may be helpful to guide surgical decision-making when contemplating full electrode insertion and the likelihood of hearing preservation.

Preparation, characterization, and in vitro/vivo evaluation of dexamethasone/poly(ε-caprolactone)-based electrode coatings for cochlear implants

With dexamethasone as the model drug and polycaprolactone (PCL) as the carrier material, a drug delivery coating for cochlear electrodes was prepared, to control cochlear fibrosis caused by cochlear implantation. A dexamethasone/poly (ε-caprolactone)-based electrode coating was prepared using the impregnation coating method. Preparation parameters were optimized, yielding 1 impregnation instance, impregnation time of 10 s, and PCL concentration of 10%. The coating was characterized in vitro using scanning electron microscopy, a universal machine, high-performance liquid chromatography, and CCK-8. The surface was porous and uniformly thick (average thickness, 48.67 µm)—with good flexibility, long-term slow drug release, and optimal drug concentration—and was biologically safe. The experimental results show that PCL is an ideal controlled-release material for dexamethasone as a drug carrier coating for cochlear implants.

Interaction Between Electric and Acoustic Stimulation Influences Speech Perception in Ipsilateral EAS Users

OBJECTIVES

The aim of this study was to determine electric-acoustic masking in cochlear implant users with ipsilateral residual hearing and different electrode insertion depths and to investigate the influence on speech reception. The effects of different fitting strategies-meet, overlap, and a newly developed masking adjusted fitting (UNMASKfit)-on speech reception are compared. If electric-acoustic masking has a detrimental effect on speech reception, the individualized UNMASKfit map might be able to reduce masking and thereby enhance speech reception.

DESIGN

Fifteen experienced MED-EL Flex electrode recipients with ipsilateral residual hearing participated in a crosssover design study using three fitting strategies for 4 weeks each. The following strategies were compared: (1) a meet fitting, dividing the frequency range between electric and acoustic stimulation, (2) an overlap fitting, delivering part of the frequency range both acoustically and electrically, and (3) the UNMASKfit, reducing the electric stimulation according to the individual electric-on-acoustic masking strength. A psychoacoustic masking procedure was used to measure the changes in acoustic thresholds due to the presence of electric maskers. Speech reception was measured in noise with the Oldenburg Matrix Sentence test.

RESULTS

Behavioral thresholds of acoustic probe tones were significantly elevated in the presence of electric maskers. A maximum of masking was observed when the difference in location between the electric and acoustic stimulation was around one octave in place frequency. Speech reception scores and strength of masking showed a dependency on residual hearing, and speech reception was significantly reduced in the overlap fitting strategy. Electric- acoustic stimulation significantly improved speech reception over electric stimulation alone, with a tendency toward a larger benefit with the UNMASKfit map. In addition, masking was significantly inversely correlated to the speech reception performance difference between the overlap and the meet fitting.

CONCLUSIONS

(1) This study confirmed the interaction between ipsilateral electric and acoustic stimulation in a psychoacoustic masking experiment. (2) The overlap fitting yielded poorer speech reception performance in stationary noise especially in subjects with strong masking. (3) The newly developed UNMASKfit strategy yielded similar speech reception thresholds with an enhanced acoustic benefit, while at the same time reducing the electric stimulation. This could be beneficial in the long-term if applied as a standard fitting, as hair cells are exposed to less possibly adverse electric stimulation. In this study, the UNMASKfit allowed the participants a better use of their natural hearing even after 1 month of adaptation. It might be feasible to transfer these results to the clinic, by fitting patients with the UNMASKfit upon their first fitting appointment, so that longer adaptation times can further improve speech reception.

Electrophysiological and histomorphological changes of cochlea in miniature pigs after abrasion of round window niches

Background: In operations of cochlea implantation (CI), many surgeons choose to drill a window on the bone wall of cochlea basic rotation, when more and more patients receive CI with residual hearing, what damage this step would result in is unclear.Objective: To study the effect to inner ear hair cells which is caused by drilling during CI.Methods: 6 miniature pigs are equally divided into two groups, Round window niche of each pig in the experimental group was milled, while the pigs in control group wasn't. After implanting depth of 6.5, 11.5 and 20 mm, round window electrocochleography was recorded to analyze the change of cochlea microphonic (CM) potentials respectively, histomorphological changes was observed.Results: Thresholds of CM in experimental group were higher than that of control group at different depth, amplitudes were smaller. In further group, cilia of inner hair cells (IHC) at bottom rotation were significantly damaged. After operation, ABR hearing threshold of experimental group was higher, differences at low frequency region were more obvious.Conclusions: Damage caused by mulling round window niche may seriously affect the function of the hair cells. Damage of the IHC is greater than OHC. CI through round window may protect residual hearing.

Comparison of Hearing Preservation Outcomes Using Extended Versus Single-Dose Steroid Therapy in Cochlear Implantation

OBJECTIVES

The purpose of this study was to compare the hearing preservation outcomes of patients who received extended versus single-dose steroid therapy in cochlear implant surgery.

DESIGN

Case-control.

SETTING

Tertiary referral centers in Taiwan from April 2017 to 2019.

PARTICIPANTS

A total of 70 patients aged 1 to 78 years old (mean = 18.04, standard deviation [SD] = 21.51) who received cochlear implantation via the round window approach were included in the study. Prospectively, 35 cases were enrolled for cochlear implantation with single-dose therapy. Thirty-five controls who underwent cochlear implantation with extended therapy were retrospectively enrolled after frequency matching.

OUTCOME MEASURES

The main outcome measure was the rate of hearing preservation. This was calculated based on the HEARRING Network formula and results were categorized as complete, partial, and minimal. Impedances served as secondary outcomes.

RESULTS

There was no significant difference in the complete hearing preservation rates between the extended and single-dose groups at 6 months postoperatively. Impedances were significantly lower in the extended group after 1 month and 6 months of follow up. When the complete and partial hearing preservation groups were compared, the size of round window opening and speed of insertion were found to be statistically significant.

CONCLUSIONS

Both extended and single-dose therapies result in good hearing preservation in patients who undergo cochlear implantation. However, better impedances can be expected from patients who received extended therapy. A slower speed of insertion and a widely opened round window play a role in hearing preservation.

The Effects of Round Window Membrane Injury and the Use of a Model Electrode Application on Hearing in Rats

OBJECTIVE

To investigate the effects of the mechanical trauma to the round window, a model electrode inserted into the scala tympani on the cochlear reserve, and the efficacy of topical steroids in preventing hearing loss.

MATERIALS AND METHODS

21 male Wistar Albino rats were equally categorized into three groups. In all groups an initial mechanical injury to round window was created. Only subsequent dexamethasone injection was administrated into the cochlea in the subjects of group 2 while a multichannel cochlear implant guide inserted into the cochlea prior to dexamethasone administration for group 3. Distortion product otoacoustic emissions (DPOAEs) were obtained prior to and immediately after the surgical injury, eventually on postoperative seventh day (d 7). Mean signal/noise ratios (S/Ns) obtained at 2000, 3000, and 4000 Hz were calculated. Data sets were compared with non-parametric statistical tests.

RESULTS

The early intraoperative mean S/Ns were significantly less than preoperative measurements for group 1 and 2; however, preoperative and postoperative d 7 average S/Ns did not differ. There was statistically significant difference between preoperative, intraoperative and postoperative d 7 average S/Ns for group 3.

CONCLUSION

We observed that hearing was restored approximately to the preoperative levels following early postoperative repair. However, an electrode insertion into the cochlea via round window subsequent to mechanical trauma seems to cause a progressive hearing loss. Therefore, a special care must be taken to avoid the injury to the round window membrane in the course of the placement of a cochlear implant electrode and surgery for the chronic otitis media.

Minimizing Intracochlear Pressure: Influence of the Insertion Sheath

OBJECTIVE

Atraumatic cochlear implantation (CI) and insertion of the electrode in particular are major goals of recent CI surgery. Perimodiolar electrode arrays need a stylet or exosheath for insertion. The sheath can influence the intracochlear pressure changes during insertion of the electrode. The aim of this study was to modify the insertion sheath to optimize intracochlear pressure changes.

METHODS

In an artifical cochlear model, 7 different modified insertion sheaths were used. The intracochlear pressure was measured with a micro-optical sensor in the apical part of the model cochlea.

RESULTS

Significant lower intracochlear pressure changes were observed when the apical part of the insertion sheath was either shortened or tapered. Modification of the stopper does influence the intracochlear pressure significantly.

CONCLUSION

Modification of the insertion sheath leads to lower intracochlear pressure gain. The differences and impact on intracochlear pressure changes found in this study underline the importance of even subtle modifications of the electrode insertion technique.

EAS-Combined electric and acoustic stimulation

Electric-acoustic stimulation (EAS) is a special treatment modality for those patients who are profoundly deaf in the high-frequency (HF) region and retain usable hearing in the low-frequency (LF) region. Combining the electric stimulation with cochlear implant (CI) in the HF and acoustic amplification of residual hearing using a conventional hearing aid (HA) in the LF region defines EAS. The EAS concept was first proposed by C. von Ilberg from Frankfurt, Germany in the year 1997. In association with MED-EL, all the necessary safety studies were performed in non-human subjects before the first patient received it in 1997. In association with MED-EL, all the necessary safety studies were performed in non-human subjects before the first patient received it in 1999. For the patient to successfully use the EAS concept, the residual hearing needs to be preserved to a high extent and for several years. This requires a highly flexible electrode array in safeguarding the intra-cochlear structures during and after the CI electrode array insertion. Combining the HA unit with the audio processor unit of the CI was necessary for the convenient wearing of the unified audio processor. Fitting of the unified audio processor is another important factor that contributes to the overall success of the EAS treatment. The key translational research efforts at MED-EL were on the development of flexible electrodes, a unified audio processor, innovations in the fitting process, intra-operative monitoring of cochlear health during electrode insertion, pre-operative soft-ware tool to evaluate the cochlear size and electrode selection and some new innovations tried within EAS topic. This article covers the milestones of translational research from the first concept to the widespread clinical use of EAS.

Comparison of hearing outcomes in stapedotomy with fat and Hyaluronic acid gel as a sealing material: a prospective double-blind randomized clinical trial

PURPOSE

In the literature on stapes surgery, various materials have been used to seal the vestibulotomy. To date, there are only a few published randomized clinical trials with focus on hearing outcomes, using different sealing materials. Hence, the aim of this study was to compare hearing outcomes when using fat or Hyaluronic acid gel (HAG) to seal the stapedotomy.

METHODS

The present double-blind, prospective, randomized clinical trial was conducted on ears undergoing stapedotomy in Dasthgheib Hospital, a referral otology center in Southern Iran, and Dena private hospital, Shiraz Iran. A total of 150 primary stapedotomies were evaluated, and sealing material was fat in 77 ears and HAG in 73.

RESULTS

60 (77.9%) of the fat group ears and 63 (86.3%) of the HAG group ears obtained postoperative air-bone gap (ABG) within 20 dB, but the difference was not significant (p = 0.182).

CONCLUSION

As a sealing material in stapedotomy, HAG is comparable with fat in terms of hearing outcomes. Therefore, HAG is recommended as a safe sealing material in stapedotomy.

Radiological evaluation of a new straight electrode array compared to its precursors

Objective

The aim of this study is to examine electrode array coverage, scalar position and dislocation rate in straight electrode arrays with special focus on a new electrode array with 26 mm in lengths.

Study design

Retrospective study.

Setting

Tertiary academic center.

Patients

201 ears implanted between 2013 and 2019.

Main outcome measures

We conducted a comparative analysis of patients implanted with lateral wall electrode arrays of different lengths (F24 = MED-EL Flex²⁴, F26 = MED-EL Flex²⁶, F28 = MED-EL Flex²⁸ and F31.5 = MED-EL Flex^Soft). Cone beam computed tomography was used to determine electrode array position (scala tympani (ST) versus scala vestibuli (SV), intracochlear dislocation, position of dislocation and insertion angle).

Results

Study groups show no significant differences regarding cochlear size which excludes influences by cochlear morphology. As expected, the F24 showed significant shorter insertion angles compared to the longer electrode arrays. The F26 electrode array showed no signs of dislocation or SV insertion. The electrode array with the highest rate of ST dislocations was the F31.5 (26.3%). The electrode array with the highest rates of SV insertions was the F28 (5.75%). Most of the included electrode arrays dislocate between 320° and 360° (mean: 346.4°; range from 166° to 502°).

Conclusion

The shorter F24 and the new straight electrode array F26 show less or no signs of scalar dislocation, neither for round window nor for cochleostomy insertion than the longer F28 and the F31.5 array. As expected, the cochlear coverage is increasing with length of the electrode array itself but with growing risk for scalar dislocation and with the highest rates of dislocation for the longest electrode array F31.5. Position of intracochlear dislocation is in the apical cochlear part in the included lateral wall electrode arrays.

The influence of Slim Modiolar electrode on residual hearing in pediatric patients

PURPOSE

Hearing preservation cochlear implantation is an established procedure in patients with low-frequency residual hearing, especially in pediatric cochlear implantation. More delicate, thin electrode arrays can minimize damage in the inner ear and enhance the possibility for residual hearing preservation. The Cochlear^® CI532 electrode has been reported as an electrode with the potential for residual hearing preservation. No similar studies pertaining to hearing preservation in pediatric patients have appeared to date. The aim of this study was to investigate whether the Cochlear^® CI532 Slim Modiolar electrode allows the preservation of low-frequency residual hearing in children undergoing cochlear implantation.

METHODS

In this multicenter, nonrandomized, prospective clinical cohort study, medical data of 14 pediatric patients implanted with the CI532 were collected. All patients had residual low-frequency hearing (preoperative audiogram or ABR with at least one threshold better than 90 dB HL at 125, 250, 500, or 1000 Hz). Postoperative thresholds were obtained 1, 3, 6, and 12 months after cochlear implantation.

RESULTS

Based on the HEARRING classification, 78.6% of children (11/14) had complete hearing preservation at the last follow-up visit (12 months after CI, or if not available, 6 months). A total of 21.4% (3/14) had partial hearing preservation. At the last follow-up visit, neither minimal hearing preservation nor loss of hearing was observed. Functional low-frequency hearing was preserved in 13 out of 14 patients (93%).

CONCLUSIONS

The residual hearing preservation results in children were superior to the results previously reported in adults.

Cochlear implantation and residual hearing preservation long-term follow-up of the first consecutively operated patients using the round window approach in Uppsala, Sweden

Objective: We conducted a long-term follow-up study to investigate the time course of residual hearing in our first 21 consecutively operated cochlear implant (CI) patients using the round window (RW) approach . The study may provide additional information about the influence of a flexible lateral wall electrode array on cochlear function. Methods: Data were available for long-term follow-up (>5 years) in 15 patients. Pure tone audiometry (PTA) was assessed at 0.125-8 kHz preoperatively, and at one, three and >5 years postoperatively. Insertion angle, number of electrodes inside the cochlea, user-time of the processor and stimulation strategy were documented. Results: Twelve out of 15 patients had residual hearing after a follow-up period of five years (mean 86 months, range: 61-103 months). Four out of 15 patients had >75% complete hearing preservation (HP), 8 out of 15 had 25-75% partial HP and 3 out of 15 patients had complete loss of hearing. There was a high correlation between insertion angle and HP. Conclusion: Long-term HP was possible in 12 out of 15 cases. Even patients with complete hearing loss at long-term follow-up showed high performance in speech understanding and were full-time users.

Preservation of Vestibular Function and Residual Hearing After Round Window Cochlear Implantation

OBJECTIVE

To examine the possible correlation between the loss of short-term residual hearing and vestibular function after cochlear implantation (CI).

STUDY DESIGN

Retrospective patient review.

SETTING

Academic tertiary referral center.

PATIENTS

One hundred twenty patients with normal vestibular function (VF) in the caloric testing and residual hearing (RH) at the frequencies 250, 500, and 1000 Hz on the surgery side between 2008 and 2016 were included in the study.

INTERVENTION

Primary CI on the first side via round window with a conventional full-length electrode.

MAIN OUTCOME MEASURES

Changes of RH and VF 7 weeks after surgery were analyzed. Preservation of RH was defined as measurable postoperative thresholds at the frequencies 250, 500, and 1000 Hz in the pure-tone audiogram. Preservation of the VF after CI was assessed both by an absolute and relative threshold in the caloric testing.

RESULTS

Seven weeks after implantation, the preservation of RH was achieved in 52 (43.3 %) patients and the preservation of VF in 95 (79.2 %) patients on the operated side. There was no significant statistical correlation between these two parameters.

CONCLUSION

The loss of RH was more than twice as frequent as the loss of VF. However, no statistical correlation between the failure of the two inner ear functions was found. The exact causes are still unknown, but our data could give an indication that there may be different underlying pathomechanisms.

Speech Perception Outcomes for Adult Cochlear Implant Recipients Using a Lateral Wall or Perimodiolar Array

AIM

To assess the speech perception outcomes of adult CI recipients with significant preimplant low frequency hearing, examining differences between perimodiolar and lateral wall electrode placement in order to provide clinical guidance for clinicians and surgeons.

METHODS

A prospective cohort study was undertaken identifying all adults who received a thin straight electrode array (TSEA) at the Royal Victorian Eye & Ear Hospital (RVEEH) from 2010 to 2015 and who had a preimplant low frequency pure tone median ≤70 dB HL (n = 63). A retrospective review was completed of the RVEEH database to identify a comparison group who had been implanted with a perimodiolar electrode array, comprising adults implanted between 2004 and 2011 (PM Group) with preimplant hearing equivalent to the TSEA group (n = 70). The TSEA Group were further divided into subgroups in which n = 19 used EAS (TSEA-EAS) and n = 44 who used electric-only hearing (TSEA-Standard).

RESULTS

There was no significant difference in median speech perception outcomes between the TSEA and PM Groups (TSEA 61.7%, PM 67.3%, p = 0.954). A significant difference was found between the TSEA-EAS and TSEA-Standard subgroups for median speech perception outcome (TSEA-EAS median 73.5%, TSEA-Standard median 58.3%, p = 0.043).

CONCLUSIONS

Significant speech perception benefit following cochlear implantation was achieved with both the perimodiolar and lateral wall electrode arrays and no significant difference was found between outcomes with those array types in this population of adults with functional low frequency hearing pre-implant. Those that received a TSEA, had preserved hearing, and utilised an EAS sound processor performed better than their peers with a TSEA and electric-only hearing.

Effect of Round Window Opening Size on Residual Hearing Preservation in Cochlear Implantation

OBJECTIVES

This study aims to compare the hearing preservation outcomes in cochlear implant surgery following slit versus full opening of the round window membrane.

SETTING

Tertiary referral center.

STUDY DESIGN

Comparative study.

SUBJECTS AND METHODS

Seventy patients (mean, 26.3 years; range, 2-69 years) who underwent cochlear implantation via the round window approach were included in the study. Thirty-five subjects were prospectively enrolled for cochlear implantation via the open round window technique between August 2018 and January 2019. Thirty-five patients who underwent cochlear implantation from January 2017 to July 2018 via the slit round window opening, frequency matched by sex and age, were retrospectively enrolled. Pre- and postoperative thresholds were obtained. The percentage of hearing preservation was computed with the HEARRING Network formula and classified into complete, partial, and minimal hearing preservation. The results between the groups were compared and analyzed at 6 months postoperatively.

RESULTS

The rate of complete hearing preservation in the open group was statistically significant (P = .030) at 71.4% (n = 25) as compared with 45.7% (n = 16) in the slit group.

CONCLUSIONS

The widely opened round window may be an optional technique that surgeons can utilize to improve hearing preservation outcomes.

Morphometric linear and angular measurements of the human cochlea in implant patients using 3-dimensional reconstruction

The present study is the first to evaluate the spiral ganglion neurons (SGNs) and the linear and angular measurements of the cochlea in temporal bones of cochlear implant (CI) recipients. There are no studies evaluating the morphometric measures in subjects after long-term CI use, and this study fills in this gap in current knowledge, greatly important for the design of CI electrodes. Amira based 3-D reconstructions of the cochlea were generated from stained histopathological slides of 15 celloidin-embedded human temporal bones. The SGN angular distance from the round window exhibited a narrow range from 684°-704°, corresponding to linear distances of 17.87 and 34.48 mm along the inner and outer wall of the scala tympani. The first turn measured an average of 14.21 mm along the inner wall and 23.92 mm along the outer wall. The outer wall average for the second turn was 11.11 mm and for the partial third apical turn was only 4.49 mm. The range for cochlear duct angular distance was 876° to 1051°, with a mean of 2.63 turns, corresponding to an average linear distance of 39.53 mm, ranging from 35.44 mm to 43.57 mm 6 out of 15 temporal bones demonstrated better preservation of SGN in the middle and apical segments of Rosenthal's canal. The present study demonstrates that the anatomy of the cochlea of CI patients does not differ significantly from that of normative subjects and establishes measurements using the round window as the 0° reference point, an important surgical landmark. The relevance of the measurements to cochlear implant design are discussed.

[Topical drug administration to the inner ear. Modern state of the problem and development perspectives]

The work assessed modern methods of drug delivery through biological barriers to the lesion, in particular, through the most studied - skin. The main advantages and disadvantages of the existing methods for the topical administration of drugs into the inner ear - intra-imperial and intra-labyrinth delivery are analyzed. A brief review of medicinal substances for topical administration to the inner ear, both widely used (for example, aminoglycosides, steroid drugs) and undergoing clinical trials, is given. An assessment is made of the prospects for the use of transmembrane drug delivery to the inner ear using an electric field, which has a combined electro-creative and iontophoretic effect.

Cochlear Implantation With a Novel Long Straight Electrode: the Insertion Results Evaluated by Imaging and Histology in Human Temporal Bones

HYPOTHESIS

To evaluate the insertion results of a novel straight array (EVO) by detailed imaging and subsequent histology in human temporal bones (TB).

BACKGROUND

The main focuses of modern cochlear implant surgery are to prevent damage to the intracochlear structures and to preserve residual hearing. This is often achievable with new atraumatic electrode arrays in combination with meticulous surgical techniques.

METHODS

Twenty fresh-frozen TBs were implanted with the EVO. Pre- and postoperative cone beam computed tomography scans were reconstructed and fused for an artifact-free representation of the electrode. The array's vertical position was quantified in relation to the basilar membrane on basis of which trauma was classified (Grades 0-4). The basilar membrane location was modeled from previous histologic data. The TBs underwent subsequent histologic examination.

RESULTS

The EVOs were successfully inserted in all TBs. Atraumatic insertion (Grades 0-1) were accomplished in 14 of 20 TBs (70%). There were three apical translocations, and two basal translocations due to electrode bulging. One TB had multiple translocations. The sensitivity and specificity of imaging for detecting insertion trauma (Grades 2-4) was 87.5% and 97.3.0%, respectively.

CONCLUSION

Comparable insertion results as reported for other arrays were also found for the EVO. Insertion trauma can be mostly avoided with meticulous insertion techniques to prevent bulging and by limiting the insertion depth angle to 360 degrees. The image fusion technique is a reliable tool for evaluating electrode placement and is feasible for trauma grading.

Sustained-Release Triamcinolone Acetonide Hydrogels Reduce Hearing Threshold Shifts in a Model for Cochlear Implantation with Hearing Preservation

INTRODUCTION

In recent years, the preservation of residual hearing has become a major factor in patients undergoing cochlear implantation (CI). In studies attempting to pharmaceutically improve hearing preservation rates, glucocorticoids (GCs) applied perioperatively in many institutions have emerged as a promising treatment regimen. Although dexamethasone is most commonly used and has been applied successfully by various research groups, recently pharmacological properties have been reported to be relatively unsuitable for topical delivery to the inner ear. Consequently other glucocorticoids merit further evaluation. The aim of this study was therefore to evaluate the otoprotective effects of the topical application of a sustained-release triamcinolone acetonide (TAAC) hydrogel in CI with hearing preservation.

METHODS

Normal-hearing pigmented guinea pigs were randomized into a group receiving a single dose of a 6% TAAC poloxamer 407 hydrogel, a group receiving a 30% TAAC hydrogel and a control group. All hydrogel applications were performed 1 day prior to CI. After a cochleostomy was drilled, a specifically designed silicone electrode was inserted into the scala tympani for 5 mm. Frequency-specific compound action potentials of the auditory nerve (0.5-32 kHz) were measured pre- and directly postoperatively as well as on days 3, 7, 14, 21, and 28. Finally, temporal bones were harvested for histological evaluation.

RESULTS

Application of the TAAC hydrogels resulted in significantly reduced hearing threshold shifts in low, middle and high frequencies and improved spiral ganglion cell survival in the second turn of the cochlea. Outer hair cell numbers in the basal and second turn of the cochlea were slightly reduced after TAAC application.

CONCLUSION

In summary, we were able to demonstrate functional benefits of a single preoperative application of a TAAC hydrogel in a guinea pig model for CI, which persisted until the end of the observational period, that is, 28 days after surgery.

Electrophysiological detection of electrode fold-over in perimodiolar cochlear implant electrode arrays: a multi-center study case series

PURPOSE

It is important for the surgeon to determine the position of the CI electrode array during and after its placement within the cochlea. Most preferably, this should be within the scala tympani to obtain the best audiological outcome. Thus, misplacement into the scala vestibuli or tip fold-over should be prevented. Since there are different ways to ensure proper positioning of the electrode array within the scala tympani (e.g., intraoperative radiography, electrophysiological recordings), our study was aimed at detecting intraoperative electrophysiologic characteristics to better understand the mechanisms of those electrode tip fold-overs.

MATERIAL AND METHODS

In a multi-centric, retrospective case-control series, patients with a postoperatively by radiography detected tip fold-over in perimodiolar electrodes were included. The point of fold-over (i.e., the electrode position) was determined and the intraoperative Auto-NRT recordings were analysed and evaluated.

RESULTS

Four patients were found to have an electrode tip fold-over (out of 85 implantees). Significant changes of the Auto-NRT recordings were not detected. All tip fold-overs occurred in the most apical part of the electrodes.

DISCUSSION

Cochlear implantation for hearing impaired patients plays a decisive role in modern auditory rehabilitation. Perimodiolar electrode arrays may fold over during the insertion and, hence, could have a negative impact on audiological outcome. Characteristic electrophysiologic changes to possibly predict this were not found in our series.

Multicenter US Clinical Trial With an Electric-Acoustic Stimulation (EAS) System in Adults: Final Outcomes

To demonstrate the safety and effectiveness of the MED-EL Electric-Acoustic Stimulation (EAS) System, for adults with residual low-frequency hearing and severe-to-profound hearing loss in the mid to high frequencies.

Intracochlear Pressure Changes After Cochlea Implant Electrode Pullback-Reduction of Intracochlear Trauma

Objective

Different aspects should be considered to achieve an atraumatic insertion of cochlear implant electrode arrays as an important surgical goal. Intracochlear pressure changes are known to influence the preservation of residual hearing. By using the intraoperative “pullback technique,” an electrode position closer to the modiolus can be achieved than without the pullback. The aim of the present study was therefore to investigate to what extent the pullback technique can influence intracochlear pressure changes.

Methods

Insertions of cochlear implant electrodes were performed in an artificial cochlear model with two different perimodiolar arrays. Intracochlear pressure changes were recorded with a micro‐optical pressure sensor positioned in the apical part of the cochlear. After complete insertion of the electrode array, a so‐called pullback of the electrode was performed.

Results

Statistically significant pressure differences were measured if the electrode array was wet (ie, moisturized) during the pullback. Relative pressure changes in electrodes with smaller total volume are lower than pressure changes in larger electrodes.

Conclusion

The preservation of residual hearing and, thus, the resulting postoperative audiological outcome has a major impact on the quality of life of the patients and has become of utmost importance. Intracochlear pressure changes during the pullback manoeuver are small in absolute terms, but can even be still reduced statistically significantly by a moistening the electrode before insertion. Using the pullback technique in cases with residual hearing does not affect the probability of preservation of residual hearing but could lead to a better audiological outcome.

Level of Evidence

NA

Electric and Acoustic Stimulation in Cochlear Implant Recipients with Hearing Preservation

Hearing loss affects 30 million people in the United States, and a subset of these patients have normal low-frequency hearing and ski-sloped high-frequency hearing loss. For these patients, hearing aids alone may not provide adequate benefit. Cochlear implantation alone has been utilized to improve speech perception. The addition of high-frequency electric hearing to low-frequency acoustic hearing in these patients is beneficial. Technical improvements have allowed preservation of low-frequency hearing in cochlear implant recipients, allowing for electric and acoustic stimulation in the same ear with significant improvements in speech perception, sound localization, music appreciation, and quality of life.

Protecting against electrode insertion trauma using dexamethasone

OBJECTIVE

To compare the benefits of a dexamethasone-eluting array for hearing preservation and cochlear histopathology in low trauma (soft-surgery) and high trauma models of cochlear implant surgery.

METHODS

Adult guinea pigs were implanted with an intra-cochlear array using two different surgical procedures: either a soft-surgery approach or following generation of electrode insertion trauma (high trauma). Two methods of dexamethasone delivery were evaluated: elution from an electrode array alone, and elution from a cochlear implant electrode array in combination with a pre-operative systemic injection. All electrode arrays were implanted for a period of 4 weeks. Outcome measures at 4 weeks post-implantation included auditory brainstem response (ABR) thresholds, histological analysis of spiral ganglion neuron density, fibrotic tissue, new bone growth, and cochlear damage.

RESULTS

Animals exposed to high surgical trauma showed greater hearing loss than those in the low trauma model, irrespective of the presence of dexamethasone. Whilst the area of intra-cochlear fibrotic tissue growth post-implantation was also independent of dexamethasone administration, new bone growth was significantly reduced in its presence. Our high trauma model effectively obliterated the organ of Corti and significantly reduced spiral ganglion neuron densities in the lower basal turn. This trauma-induced reduction in spiral ganglion neuron survival decreased with the inclusion of a dexamethasone-eluting array. A pre-operative systemic injection of dexamethasone did not significantly improve any outcome measures beyond those provided with a dexamethasone-eluting array alone.

CONCLUSION

Dexamethasone-eluting intra-cochlear arrays may inhibit osteoneogenesis, and reduce spiral ganglion neuron loss following traumatic cochlear implantation.

Evaluating inter-aural hearing preservation in bilateral paediatric cochlear implantation

OBJECTIVE

To examine inter-aural hearing preservation results in children undergoing simultaneous bilateral cochlear implantation (CI).

METHODS

Retrospective case review in tertiary referral centre. All children undergoing simultaneous bilateral CI between January 2013 and June 2014 (18 months). Patients eligible for inclusion in the study had pre-operative hearing thresholds of <90 dB at 250 Hz and ≥100 dB at 500 Hz. Patients with anatomical cochlear anomalies or missing data were excluded. Seven patients were included, 1 male, 6 female, mean age of 12 years 11 months at the time of surgery. All patients had simultaneous bilateral cochlear implant surgery, using the same implant and technique. All patients had pre- and post-operative unaided pure tone audiometry. Inter-aural hearing preservation results were compared in each patient.

RESULTS

The achieved hearing preservation for 14 ears was complete in 5, partial in 7, and minimal in 2. Measurable hearing preservation was achieved in 86% overall. Inter-aural analysis revealed that only 2 (subjects 1 and 4) of the 7 patients had preservation results within the same preservation group (complete/partial/minimal). The mean inter-aural preservation difference was 30.7% with a range from 12.4% to 65.2%.

CONCLUSIONS

Several factors and techniques have already been identified in the wider literature to explain differences in hearing preservation results in CI. However, despite controlling for known factors, we demonstrate variable inter-aural results. This suggests that there may be more factors beyond the surgeon's control influencing our ability to provide consistent results.

Physiological Mechanisms in Combined Electric-Acoustic Stimulation

OBJECTIVE

Electrical stimulation is normally performed on ears that have no hearing function, i.e., lack functional hair cells. The properties of electrically-evoked responses in these cochleae were investigated in several previous studies. Recent clinical developments have introduced cochlear implantation (CI) in residually-hearing ears to improve speech understanding in noise. The present study documents the known physiological differences between electrical stimulation of hair cells and of spiral ganglion cells, respectively, and reviews the mechanisms of combined electric and acoustic stimulation in the hearing ears.

DATA SOURCES

Literature review from 1971 to 2016.

CONCLUSIONS

Compared with pure electrical stimulation the combined electroacoustic stimulation provides additional low-frequency information and expands the dynamic range of the input. Physiological studies document a weaker synchronization of the evoked activity in electrically stimulated hearing ears compared with deaf ears that reduces the hypersynchronization of electrically-evoked activity. The findings suggest the possibility of balancing the information provided by acoustic and electric input using stimulus intensity. Absence of distorting acoustic-electric interactions allows exploiting these clinical benefits of electroacoustic stimulation.

Preliminary Outcomes Report for CO2 Laser Assisted Electric-Acoustic Cochlear Implantation

OBJECTIVE

Report on the safety/efficacy of a novel, carbon dioxide (CO2) laser-assisted protocol for hearing-preservation cochlear implantation (HPCI) and electric-acoustic stimulation (EAS).

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Adult patients meeting established criteria for HPCI and EAS.

INTERVENTION

Therapeutic/rehabilitative. A standardized protocol used CO2 laser to achieve meticulous hemostasis and perform cochleostomy was evaluated.

MAIN OUTCOME MEASURES

Audiometric assessments included low-tone pure tone average (LtPTA), consonant-nucleus-consonant (CNC), and AzBio scores. Primary outcomes were low-tone hearing-preservation (LtHP) and EAS usage rates. Secondary outcomes included change in LtPTA, outcomes durability, and the rate/onset/presentation of delayed hearing loss (DHL). Subset analyses stratified data by presenting LtPTA and surgeon experience.

RESULTS

Forty-seven patients and 52 ears were included. Mean follow-up was 20.7 ± 12.6 months. When adjusted for preoperative LtPTA less than 60 dB, the LtHP rate was 77%. This was significantly better than for patients with LtPTA more than 60 dB (24%; p < 0.0001). Outcomes were highly durable. EAS usage was excellent in those with LtPTA less than 60 dB (100%). Nine patients developed DHL. Three additional patients (25%) were successfully salvaged via steroids. Both CNC and AzBio scores improved significantly (p < 0.0001) at definitive testing. Speech-hearing scores did not differ significantly between patients using/not using EAS. The complication rate was 3.8%; none were caused by the laser. Surgeon experience was associated with significantly better outcomes.

CONCLUSION

Use of a CO2 laser-assisted HPCI protocol was safe and effective. Outcomes were consistent with contemporary literature reporting. Patient selection and surgeon experience both significantly impacted outcomes.

Preservation of residual hearing after cochlear implant surgery: an exploration of residual hearing function in a group of recipients at cochlear implant units

Introduction

The preservation of residual hearing is becoming increasingly important in cochlear implant surgery. Conserving residual hearing is a positive prognostic indicator for improved hearing abilities.

Objective

The primary aim of the study was to explore the preservation of residual hearing following cochlear implantation in a group of recipients at two major cochlear implant centers.

Methods

A quantitative paradigm was adopted and exploratory research conducted within a retrospective data review design. The sample consisted of 50 surgical records and 53 audiological records from 60 observations (53 patients, seven of whom were implanted bilaterally). The records were selected using purposive sampling and consisted of records from participants ranging from six to 59 years of age. The average time of when the postoperative audiograms were performed in the current study was 24.7 months (s.d. = ±9.0). Data were analyzed through both qualitative and inferential statistics and a comparative analysis of unaided pre- and postoperative audiological test results was conducted.

Results

Results indicated a high success rate of 92% preservation of residual hearing with half of the sample exhibiting complete preservation in cochlear implant recipients across all frequencies postoperatively. A total postoperative hearing loss was found in only 8% of cochlear implantees across all frequencies. There was no relationship between preoperative hearing thresholds and preservation of hearing postoperatively. The two main surgical techniques used in the current study were the contour on stylet and the advance off-stylet techniques, with the majority of surgeons utilizing a cochleostomy approach. From the findings, it became apparent that the majority of cases did not have any reported intraoperative complications. This is a positive prognostic indicator for the preservation of residual hearing.

Conclusion

Findings suggest improved cochlear implant surgical outcomes when compared to previous studies implying progress in surgical techniques. The surgical skill and experience of the surgeon are evidenced by the minimal intraoperative complications and the high success rate of hearing preservation. This is a positive prognostic indicator for individuals with preoperative residual hearing as the preserved residual hearing allows for the potential of electro-acoustic stimulation, which in turn has its own hearing benefits.

Cochlear implantation using the underwater technique: long-term results

INTRODUCTION

The opening of the round window and the insertion of the electrode array into the scala tympani during cochlear implant surgery can lead to a pressure shock of the delicate inner ear structures. By filling the tympanic cavity with Ringer Solution during these surgical steps (underwater technique), the hydrostatic pressure of the fluid acts as a smooth pressure stabilizer, avoiding a pressure shock of the inner ear structures. The aim of this retrospective study was to present long-term results of this new method of cochlear implantation in underwater technique.

METHODS

Altogether, 47 implantations in 43 patients with residual hearing at the frequencies 250, 500 and 1000 Hz in the unaided preoperative pure tone audiometry were included. A cochlear implantation via round window with a conventional full-length electrode was performed in underwater technique. Changes of residual hearing 7 weeks and 24 months after surgery were analyzed.

RESULTS

Overall postimplant hearing preservation 7 weeks after implantation was achieved in 22 ears (47%). Subsequent follow-up was performed on average 24 months after surgery (range 12 months-4.2 years) in all patients. At this late postoperative evaluation, preservation of hearing was recorded in 18 ears (38%). Neither the follow-up time nor the type of electrode had a significant impact on the postoperative hearing loss.

CONCLUSION

The underwater technique is an atraumatic cochlear implantation technique with hearing preservation rates comparable to results in literature and a very small hearing preservation decline rate over time even when using full-length CI electrodes.

Hearing Preservation Outcomes for 139 Cochlear Implant Recipients Using a Thin Straight Electrode Array

OBJECTIVE

To assess the hearing preservation outcomes in a large group of adult cochlear implant recipients implanted with a thin straight electrode array using atraumatic surgical techniques. Factors affecting hearing preservation will be investigated.

STUDY DESIGN

Prospective cohort study undertaken at the Royal Victorian Eye and Ear Hospital in Melbourne, Australia from December 2010 to May 2015.

SETTING

Tertiary academic hospital.

PATIENTS

One hundred thirty-nine adults undergoing cochlear implantation (CI).

MAIN OUTCOME MEASURE

Primary outcome measure of interest was pre and postoperative pure-tone audiometry.

RESULTS

Median low-frequency hearing change for the whole group of 139 recipients was -22.5 dB at the 3 months postop point. Eighty-six participants had functional preoperative low-frequency hearing (≤70 dB average at 250 and 500 Hz). Of these, 90.7% retained measureable hearing at 3 months postimplant. 39.5% of this original 86 participants retained functional hearing at 3 months postimplant. At 12 months postimplant, those who retained functional hearing at 3 months had no significant change in hearing. The group who lost functional hearing continued to have a significant deterioration in low-frequency hearing. Degree of hearing loss preimplant was identified as a predictor for the preservation of hearing postoperatively.

CONCLUSION

Preservation of hearing is possible following atraumatic cochlear implant surgery with a thin straight electrode array. The amount of hearing preserved seems to be variable, and factors related to this variability are not yet known. The results of the present study suggest preoperative low-frequency hearing at or better than 45 dB may be related to preservation of functional hearing.

Factors affecting residual hearing preservation in cochlear implantation

The likelihood of residual hearing preservation in cochlear implantation (CI) is related to surgical factors such as type of cochleostomy (trans-fenestral vs. promontorial), use of lubricants and protective drugs, and device-related factors such as shape, length and flexibility of the array. We investigated the impact of these factors on the hearing preservation rate in adults and children with conventional audiological indications to CI. Eighty-two children aged 1-9 years and 73 adults (16-79 years) received a CI in the right (59%) or left ear (41%). An anterior-inferior promontorial cochleostomy was performed in 143 ears (92%); a trans-fenestral approach was used in 12 (8%). A perimodiolar electrode was implanted in 144 ears (93%), and a straight electrode in the remaining 11 (7%). Overall, some post-operative hearing was retained in 39% of ears. The rate of preservation was higher at the low than at the high frequencies. When correlated with age, side of implant, implant model and type of cochleostomy, the mean threshold variations did not reach statistical significance for any of these variables. A slight trend in favour of better residual hearing preservation in children vs. adults was seen, especially at lower frequencies.

Hearing Preservation: Does Electrode Choice Matter?

Objective Evaluate if electrode design affects hearing preservation (HP) following cochlear implantation (CI) with full-length electrodes. Study Design Case series with chart review. Setting Tertiary referral academic center. Subjects and Methods Forty-five adults with low-frequency hearing (≤85 dB at 250 and 500 Hz) who underwent unilateral CI with full-length electrode arrays made by 1 manufacturer were included. HP was calculated with (1) mean low-frequency pure-tone average (LFPTA) at 250 and 500 Hz (MEAN method), (2) a percentile method across the audiometric frequency spectrum generating an S-value (HEARRING method), and (3) functional if hearing remained ≤85 dB at 250 and 500 Hz. Audiometric testing was performed approximately 1 month and 1 year postoperatively, yielding short-term and long-term results, respectively. Results Of 45 patients who underwent CI, 46.7% received lateral wall (LW) and 53.3% received perimodiolar (PM) electrodes. At short-term follow-up, LW electrodes were associated with significantly better HP than PM (LFPTA method: 27.7 vs 39.3 dB, P < .05; S-value method: 48.2 vs 21.8%, P < .05). In multivariate regression of short-term outcomes, LW electrode use was a significant predictor of better HP ( P < .05). At long-term follow-up, electrode type was not associated with HP. Younger patient age was the only significant predictor of long-term HP on multivariate analysis ( P < .05). Conclusion The LW electrode is associated with short-term HP, suggesting its design is favorable for limiting trauma to the cochlea during and directly following CI. Other factors, including age, are relevant for maintaining HP over the long term. The data support further investigation into what modifiable factors may promote long-term HP.