Conservation of low-frequency hearing in cochlear implantation

OBJECTIVES: As results with cochlear implants have continued to improve, patients with some remaining cochlear function have become eligible for cochlear implantation. Thus, preservation of acoustic hearing after implantation has gained importance. Hearing preservation can be considered a benchmark for atraumatic implantation preventing neural degeneration from loss of residual hair cells or subsequent to local trauma. In this prospective study, the possibility of preserving low-frequency hearing in cochlear implantation using a modified surgical technique has been explored. MATERIAL AND METHODS: In a prospective study design, 14 subjects with considerable low-frequency hearing of 20-60 dB in the frequency range 125-500 Hz but with unsatisfactory speech understanding with hearing aids of < 35% monosyllabic word understanding were implanted with a MED-EL COMBI-40+ cochlear implant. The insertion depth was intentionally limited to 19-24 mm to prevent damage to low-frequency regions of the cochlea. Pre- and postoperative pure-tone thresholds were measured. RESULTS: Hearing was conserved within 0-10 dB in 9/14 subjects and within 11-20 dB in 3/14; in 2/14 subjects hearing was completely lost in the implanted ear. Thus hearing could at least partially be conserved in 12/14 subjects (86%). Median threshold values decreased by 10, 15, 17.5 and 5 dB at 125, 250, 500 and 1000 Hz, respectively. Even high levels of hearing, e.g. 30 dB at 500 Hz, could be maintained after implantation in some subjects. CONCLUSIONS: This study reports successful conservation of hearing after cochlear implantation using a modified surgical technique. Even high levels of hearing could be maintained, showing that implantation of an intracochlear electrode can be performed atraumatically with preservation of functional structures.     

Effects of electrical stimulation on the acoustically evoked auditory-nerve response in guinea pigs with a high-frequency hearing loss

Criteria for cochlear implantation keep expanding and people with substantial residual low-frequency hearing are considered candidates for implantation nowadays. Therefore, electro-acoustical stimulation in the same ear (EAS) is receiving increasing interest. We have investigated the effects of intracochlear electrical stimulation on acoustically evoked auditory-nerve activity, using a forward masking paradigm. The stimulation electrode was placed in the basal turn of the cochlea. Compound action potential (CAP) recordings were performed in guinea pigs with severe high-frequency hearing loss and in normal-hearing control animals. In normal-hearing animals, electrical stimulation generally suppressed CAPs, especially at high acoustic frequencies (8 and 16?kHz) and low sound levels. At low frequencies (0.5 and 1?kHz), suppression was observed only at high sound levels. In animals with a high-frequency hearing loss, suppression of CAPs at low frequencies was substantially less compared to control animals, even at high current levels and temporal overlap of acoustic and electric stimuli. Hence, effects of electrical stimulation substantially differed between normal-hearing animals and animals with a high-frequency hearing loss. These findings stress the need for a proper animal model when investigating EAS. We conclude that in case of high-frequency loss, the basal part of the cochlea can be stimulated electrically with little effect on responses to low-frequency acoustic stimuli.     

Conservation of low-frequency hearing in cochlear implantation

Objective As results with cochlear implants have continued to improve, patients with some remaining cochlear function have become eligible for cochlear implantation. Thus, preservation of acoustic hearing after implantation has gained importance. Hearing preservation can be considered a benchmark for atraumatic implantation preventing neural degeneration from loss of residual hair cells or subsequent to local trauma. In this prospective study, the possibility of preserving low-frequency hearing in cochlear implantation using a modified surgical technique has been explored.

Materials and Methods In a prospective study design, 14 subjects with considerable low-frequency hearing of 2–60 dB in the frequency range 125–500 Hz but with unsatisfactory speech understanding with hearing aids of < 35% monosyllabic word understanding were implanted with a MED-EL COMBI-40+ cochlear implant. The insertion depth was intentionally limited to 19–24 mm to prevent damage to low-frequency regions of the cochlea. Pre- and postoperative pure-tone thresholds were measured.

Results Hearing was conserved within 0-10 dB in 9/14 subjects and within 11–20 dB in 3/14; in 2/14 subjects hearing was completely lost in the implanted ear. Thus hearing could at least partially be conserved in 12/14 subjects (86%). Median threshold values decreased by 10, 15, 17.5 and 5 dB at 125, 250, 500 and 1000 Hz, respectively. Even high levels of hearing, e.g. 30 dB at 500 Hz, could be maintained after implantation in some subjects.

Conclusions This study reports successful conservation of hearing after cochlear implantation using a modified surgical technique. Even high levels of hearing could be maintained, showing that implantation of an intracochlear electrode can be performed atraumatically with preservation of functional structures.     

Characterization of a potassium-based leak conductance in the medial nucleus of the trapezoid body

In cochlear implants, the signal is filtered into different frequency bands and transmitted to electrodes along the cochlea. In this study the frequency-place function for electric hearing was investigated as a means to possibly improve speech coding by delivering information to the appropriate cochlear place. Fourteen subjects with functional hearing in the contralateral ear have been provided with a MED-EL cochlear implant in the deaf ear in order to reduce intractable tinnitus. Pitch scaling experiments were performed using single-electrode, constant-amplitude, constant-rate stimuli in the implanted ear, and acoustic sinusoids in the contralateral ear. The frequency-place function was calculated using the electrode position in the cochlea as obtained from postoperative skull radiographs. Individual frequency-place functions were compared to Greenwood's function in normal hearing. Electric stimulation elicited a low pitch in the apical region of the cochlea, and shifting the stimulating electrode towards the basal region elicited increasingly higher pitch. The frequency-place function did not show a significant shift relative to Greenwood's function. In cochlear implant patients with functional hearing in the non-implanted ear, electrical stimulation produced a frequency-place function that on average resembles Greenwood's function. These results differ from previously derived data.     

Development and evaluation of an improved cochlear implant electrode design for electric acoustic stimulation

OBJECTIVE: The objective of this study was to assess the intracochlear position and the extent of trauma to cochlear structures using a new prototype electrode carrier (Flex EAS). Special emphasis was placed on the practicality for combined electric and acoustic stimulation of the auditory system. STUDY DESIGN: Human temporal bones were evaluated histologically after insertion of the electrodes, and insertion forces were measured in an acrylic model of the scala tympani. METHODS: 1) Insertion forces with the regular C40+ array and the new electrode prototype were measured in an acrylic model of the scala tympani. 2) Ten human temporal bones were implanted using the same surgical procedure as in vivo. All bones underwent fixation methylmethacrylate embedding to allow cutting of the undecalcified bone with the electrode in situ. In addition, radiography of the implanted devices was performed and correlated to histologic results. Electrode positions and trauma to cochlear structures were then evaluated histologically. RESULTS: All insertions of the new electrode array were performed in the scala tympani of the cochlea. All insertions were atraumatic and covered one cochlear turn. The only effect on cochlear structures that could be observed was a slight lifting of the basilar membrane in the middle turn limited to the tip of the electrode. In three bones, basal trauma, which resulted from the cochleostomy itself, could be observed as well. All neural structures remained intact. CONCLUSIONS: The new electrode prototype provides very good mechanical properties for safe and atraumatic implantation. All criteria for the use in hearing-preservation cochlear implantation for electric and acoustic stimulation were fulfilled. Surgical measures to prevent basal trauma appear to be very important.     

Combined electric and acoustic stimulation of the auditory system: results of a clinical study

Combined electric and acoustic stimulation (EAS) of the auditory system is a new therapy for patients with severe to profound high- and mid-frequency hearing loss but remaining low-frequency hearing. In a prospective study, 13 patients with low-frequency hearing of better than 60 dB below 1 kHz were implanted with a MED-EL COMBI 40+ cochlear implant. Pure tone thresholds as well as monosyllabic word scores and Hochmair-Schulz-Moser sentences in quiet and in noise were measured with hearing aids, cochlear implant alone and in the combined stimulation mode (EAS) in the same ear. Hearing could be partially preserved in 11 out of the 13 patients. All patients scored significantly higher with cochlear implant alone than with hearing aids. Seven patients scored higher in the EAS mode than with cochlear implant alone for sentences in noise, 4 remained unchanged, and 2 could not use EAS. Synergistic effects of EAS were most prominent for hearing in noise with increases of up to 72% as compared to cochlear implant alone.     

有低频残余听力感音神经聋的人工耳蜗植入术

目的介绍一种有低频残余听力感音神经聋的人工耳蜗植入技术,探讨人工耳蜗植入手术对有残余听力患者的治疗效果和价值。方法15例有残余听力的患者接受了保护残余听力的人工耳蜗植入手术。术中电极植入深度在19mm～24mm左右。术后分别检测单纯使用助听器、单纯使用人工耳蜗、人工耳蜗结合助听器三种不同状态下的听力。结果15例患者中,有13例术后残余听力保存良好,仅分别丢失5～20dB听力,但另2例术后残余听力全部丧失。术后在安静、信噪比15dB和10dB三种不同状态下的言语测试结果显示,人工耳蜗结合助听器使用者测试得分始终保持在很高水平;单纯使用人工耳蜗者也有较好的成绩,但在信噪比达10dB的条件下,测试成绩下降;而单纯使用助听器者,不仅在安静状态下听力成绩不甚理想,一旦加入竞争性噪声,听力测试成绩急剧下降。结论保护和利用残余听力的人工耳蜗植入技术,使人工耳蜗植入手术对象从重度或极重度聋扩大到高频为重度或极重度聋,低频（≤500Hz）为中、轻度聋的患者。接受这项技术患者的听力和言语识别能力均明显优于其单纯配戴助听器和单纯使用人工耳蜗时的听力和言语识别能力。     

The influence of different speech processor and hearing aid settings on speech perception outcomes in electric acoustic stimulation patients

OBJECTIVE: Electric acoustic stimulation (EAS) is an increasingly popular means of treating individuals with a steeply sloping mid-to-high frequency hearing loss, who traditionally do not benefit from hearing instruments. These persons often have too much residual hearing to be considered for a cochlear implant. Several studies have demonstrated the ability both to preserve the remaining low-frequency hearing in these individuals, and to provide significant benefit through combining a cochlear implant with a hearing aid to amplify the same ear. These improvements in performance have been especially noted in noise. Often overlooked is that these outcomes may be influenced by the fitting parameters of both the cochlear implant and the hearing aid. DESIGN: This study assessed four EAS subjects, with a minimum of 1 month's EAS use, on eight different fitting parameters. Sentence testing in different noise levels (+15, +10, and +5 dB SPL) was conducted. Subjects also evaluated each condition using a visual analogue scale. RESULTS: Results demonstrated that a reduced overlap of cochlear implant and hearing aid amplification produced best results across listening conditions. CONCLUSIONS: The hearing aid should be fit to a patient-specific modified audiogram at least up to the point where low-frequency hearing is not measurable. The cochlear implant should be fit from a higher frequency point than is standard in patients without residual hearing in the implanted ear, to provide reduced overlap with the amplification provided by the hearing aid. Therefore, a small amount of overlap between the frequency ranges used by the hearing aid and the cochlear implant seems beneficial.     

人工中耳在体纯音传输特性的实验研究

目的探讨人工中耳（middle ear implant，MEI）的纯音保真性。方法10只(20耳)听力正常的纯种新西兰大白兔作为实验动物，分别记录人工中耳部分植入前和植入后圆窗龛处的耳微音器电位（cochlea     

Predicting the effect of post-implant cochlear fibrosis on residual hearing

Intracochlear scarring is a well-described sequela of cochlear implantation. We developed a mathematical model of passive cochlear mechanics to predict the impact that this might have upon residual acoustical hearing after implantation. The cochlea was modeled using lumped impedance terms for scala vestibuli (SV), scala tympani (ST), and the cochlear partition (CP). The damping of ST and CP was increased in the basal one half of the cochlea to simulate the effect of scar tissue. We found that increasing the damping of the ST predominantly reduced basilar membrane vibrations in the apex of the cochlea while increasing the damping of the CP predominantly reduced basilar membrane vibrations in the base of the cochlea. As long as intracochlear scarring continues to occur with cochlear implantation, there will be limitations on hearing preservation. Newer surgical techniques and electrode technologies that do not result in as much scar tissue formation will permit improved hearing preservation.     

Auditory responses in cochlear implant users with and without GJB2 deafness

OBJECTIVE/HYPOTHESIS: It is reasonable to suppose that the pattern of sensorineural damage along the length of the cochlea depends on the etiology of a hearing loss (HL). In GJB2-related deafness, we hypothesize that gap junction deficits are uniformly distributed and will result in similar damage along the length of the cochlea as compared with non-GJB2 subjects. We assessed this by measuring patterns of neural activity and hearing from apical versus basal cochlear implant electrode regions. STUDY DESIGN: This was a prospective, blind, controlled study. METHODS: Blood from 301 pediatric cochlear implant users was analyzed for mutations in GJB2 by direct sequencing. After exclusion of patients with monoallelic GJB2 mutations, associated syndromes, or risk factors for HL that were not congenital, 39 children with biallelic GJB2 mutations and 58 without GJB2 mutations were evaluated. Hearing was measured before implantation at frequencies ranging from 250 Hz to 8 kHz. After implantation, neural activity at the apical and basal ends of the implanted array was measured using electrically evoked compound action potentials of the auditory nerve (ECAPs) and evoked stapedius reflexes (ESRs). RESULTS: GJB2 and non-GJB2 groups were not significantly different with respect to sex, age at implantation, duration of auditory deprivation, hearing aid use, duration of aided hearing, ear implanted, implant model, or depth of insertion (P>.05). Children with GJB2-related HL had greater similarities between low- and high-frequency residual hearing and between neural activity electrically evoked at apical and basal regions of the cochlea as compared with children with non-GJB2-related HL who demonstrated larger deficits in basal regions. CONCLUSION: Results suggest more consistent spiral ganglion survival along the length of the cochlea in GJB2-related HL as compared with non-GJB2-related HL, which appears to involve a decreasing gradient of spiral ganglion survival from the apex to the base of the cochlea. Our findings support our premise that in GJB2-related HL, dysfunction of gap junctions likely occurs to a similar degree in the apical and basal regions of the cochlea. This knowledge might be used to customize implantable devices for patients with HL in the future.     

Effects of round window dexamethasone on residual hearing in a Guinea pig model of cochlear implantation

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.     

人工中耳在体纯音传输特性的实验研究

目的 探讨人工中耳（middle ear implant,MEI)的纯音保真性。方法 10只（20耳）听力正常的纯种新西兰大白兔作为实验动物,分别记录人工中耳部分植入前和植入后窗龛处的耳微音器电位（cochlea microphonics,CM)变化。声刺激信号为短纯音。结果 在0．5－6kHz频率范围内,植入MEI后兔耳的频率响应函数与值入MEI前听力正常家兔相似,在频率大于1kHz时,增益因子约10－15dB。结论 实验结果表明,该系统具有适合于言语传输的频响范围,具有较高的保真度。     

Combined electro‐acoustic stimulation: a beneficial union?

Background: The most pressing problem facing cochlear implant research is no longer making artificial hearing a reality. Instead, it is to develop devices that can more clearly reflect the capabilities of the human auditory system. Current cochlear implants rarely provide adequate pitch perception. As hearing loss commonly affects higher, more than lower frequencies, a possible solution is to preserve acoustic hearing at low frequencies by inserting a short electrode array and thus deliver combined electro‐acoustic stimulation (EAS). Objective of review: To determine whether individuals with severe‐to‐profound high‐frequency hearing loss have realised this predicted benefit of combined EAS, over conventional cochlear implants, with respect to pitch. Type of review: A systematic review of publications pertaining to the benefits of combined EAS over conventional cochlear implantation, with specific reference to pitch perception. Search strategy: A systematic literature search was conducted across multiple databases and supplemented by searching the reference lists of relevant trials and identified reviews. Results: The included studies suggest an overall benefit of combined EAS, over conventional cochlear implants, with respect to pitch. In addition, (i) 13% sustained a total loss of low‐frequency hearing post‐implantation of the short electrode array and, (ii) 24% had >20 dB hearing loss across all frequencies and/or total hearing loss. Conclusions: For patients with severe‐to‐profound high‐frequency hearing loss combined EAS appears to offer a significant, everyday, long‐term benefit. However, further clinical trials with larger numbers of candidates are necessary to confirm this finding. The risks involved cannot be ignored, but there is potential for a variety of strategies to improve the safety margin.     

Measurement of Basilar Membrane Motion During Round Window Stimulation in Guinea Pigs

Driving the cochlea in reverse via the round window membrane (RWM) is an alternative treatment option for the hearing rehabilitation of a nonfunctional or malformed middle ear. However, cochlear stimulation from the RWM side is not a normal sound transmission pathway. The basilar membrane (BM) motion elicited by mechanical stimulation of the RWM is unknown. In this study, the BM movement at the basal turn was investigated in both reverse via RWM drive and acoustic stimulation in the ear canal or forward drive in postmortem isolated temporal bone preparations of guinea pigs. During reverse drive, a magnet-coil was coupled on RWM, and the BM vibration at the basal turn and the movement of the incus tip were measured with laser Doppler vibrometry. During forward drive, the vibration of the incus tip induced by sound pressure in the ear canal resulted in BM vibration and the BM movement at the same location as that in the reverse stimulation was measured. The displacement ratio of the BM to RWM in reverse drive and the ratio of the BM to incus in forward drive were compared. The results demonstrated that the BM response measured in both situations was similar in nature between forward and reverse drives. This study provides new knowledge for an understanding of BM movement induced by reverse drive via the RWM stimulation.     

Evaluation of an electrode design for the combined electric-acoustic stimulation

BACKGROUND: The objective of this study was to assess the intracochlear position and the extent of trauma to cochlear structures using the C40(+) M electrode (MED-EL, Innsbruck, Austria), which was especially designed for the combined electric acoustic stimulation. METHODS: Five human temporal bones were implanted using a standard cochlear implant procedure featuring mastoidectomy, posterior tympanotomy, and promontory cochleostomy. For the cochleostomy, an inferior approach with preservation of the endosteum of the cochlea was used to contribute to hearing preservation in the in vivo condition. RESULTS: All insertions of the new electrode array were performed into the scala tympani of the cochlea. The average insertion depth was 288 degrees. Apically, 4 of the 5 implantations were completely atraumatic. One bone showed a rupture of the basilar membrane only at the tip of the electrode. However, 4 of the 5 arrays produced severe trauma to basal cochlear structures. Two pathomechanisms, the direct traumatization through drilling of the cochleostomy or the indirect traumatization via buckling of the array could be distinguished. CONCLUSIONS: Due to the reduced contact spacing and its flexible body, the C40(+) M electrode is suitable for cochlear implantations with hearing preservation and combined electric and acoustic stimulation of the auditory system. Modifications of the surgical pathway to the cochlea should help to minimize the risk of basal cochlear trauma.     

Effects of frequency and intensity of sound on cochlear blood flow.

Laser Doppler flowmetry demonstrates that loud sound induces a decrease of blood flow in the cochlea of the guinea pig. In this experiment, we observed the effects of frequency and intensity of sound on cochlear blood flow using 15 guinea pigs. In the first 5 guinea pigs, a Doppler probe was attached to the basal turn of the cochlea and sounds of 6, 7, 8, 9 and 10 kHz were delivered to the ear serially from lower to higher frequency, i.e. from 6 kHz to 10 kHz. In the next 5 guinea pigs, the sound was delivered from higher to lower frequency, i.e. from 10 kHz to 6 kHz. The sound intensity delivered to the ear was changed from lower to higher intensity (80 to 120 dB SPL by 10 dB width) at each frequency. In the last 5 guinea pigs, the blood flow in the basal, second, third, and fourth turns of the cochlea was measured at 120 dB SPL of 10 kHz. No change of blood flow was seen in the cochlear basal turn at 6 and 7 kHz up to 120 dB SPL, but a decrease of blood flow was found at 110 and 120 dB SPL at 8, 9, and 10 kHz. On the other hand, the sound of 120 dB SPL at 10 kHz induced a decrease of blood flow only in the basal turn of the cochlea. Our results suggest that there is a corresponding blood flow area which is sensitive to specific frequency in the cochlea.     

Contralateral masking in cochlear implant users with residual hearing in the non-implanted ear

Contralateral masking was investigated in cochlear implant users with residual hearing in the non-implanted ear. Threshold elevations for acoustic probes were observed when electrical maskers were presented in the opposite ear. Also, threshold elevations for electrical probes were observed when acoustic contralateral maskers were presented. The amount of threshold shift expressed in decibels charge or decibels sound pressure level produced by either contralateral acoustic or electric maskers was within the range found in normal listeners for similar stimuli (i.e. 4-8 dB). There was a correlation between the sensation level of acoustic maskers and the maximum amount of masking observed which is consistent with data for normally hearing subjects. The width of the masking patterns was similar to that expected from forward masking patterns in severely sensorineurally impaired ears and implanted ears. The maximum amount of acoustic masking tended to occur for electrode positions that were more basal than expected from characteristic frequency positions. However, where a relatively high-frequency 4-kHz masker could be used, there was a good match between the characteristic frequency position of the maximum threshold elevation and that of the masker.     

Preservation of low frequency hearing in partial deafness cochlear implantation (PDCI) using the round window surgical approach

CONCLUSION: Successful hearing preservation is possible in individuals with excellent low frequency hearing. This is possible due to the partial insertion of an atraumatic electrode using an atraumatic round window surgical technique. OBJECTIVES: This paper describes the round window surgical technique used to preserve excellent low frequency hearing in patients receiving partially inserted MED-EL cochlear implant electrodes. Results of preserved low frequency hearing in partial deafness cochlear implantation (PDCI) are reported. PATIENTS AND METHODS: The surgical approach is described in detail. Ten subjects received a partial insertion of a standard electrode, using the round window approach. Pure tone audiometry was conducted in the implanted and non-implanted ear preoperatively, at implant fitting and then at 1, 3, 6 and 12 months after initial device fitting. RESULTS: Results show hearing preservation in 9 of the 10 subjects. One subject lost all hearing 2 weeks after cochlear implantation. Hearing has remained essentially stable up to the 1 year postoperative period. Eight of the nine subjects use the cochlear implant together with their natural low frequency hearing; one subject uses a hearing aid in the implanted ear to amplify the low frequencies.     

Standard cochlear implantation of adults with residual low-frequency hearing: implications for combined electro-acoustic stimulation.

OBJECTIVE: This study compared preoperative and postoperative cochlear implant benefit in subjects with steeply sloping high-frequency hearing losses (HLs) who were implanted with standard long cochlear implant electrodes to: 1) determine the effect of etiology, 2) compare outcomes in studies exploring the use of combined electrical and acoustic stimulation, and 3) compare outcomes in patients implanted using standard criteria. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Nine adults with steeply sloping high-frequency congenital (n=2) or acquired (n=7) bilateral sensorineural HL. All pure-tone audiograms fit the criteria for trials of a short electrode aimed at preserving low-frequency acoustic hearing. INTERVENTION: Subjects received full insertion of a standard cochlear implant long electrode in the poorer ear. MAIN OUTCOME MEASURES: Preoperative versus postoperative audiograms, word and sentence recognition in quiet and noise. RESULTS: Patients with progressive acquired HLs experienced significantly improved speech understanding in quiet and in noise with the cochlear implant, especially when combined with hearing aid use in the contralateral ear. Patients with congenital HLs experienced little or no improvement in the implanted ear when tested with the implant alone, but achieved some benefit when the implant was combined with a hearing aid in the nonimplanted ear. CONCLUSION: Based on this small sample, patients with acquired steeply sloping high-frequency HLs obtain significant benefit from cochlear implantation with standard long electrodes. In progressive losses, full insertion of a long electrode would be preferable to a short electrode because acoustic hearing may diminish over time. In contrast, patients with congenital losses may not benefit from long electrodes, and might be better served by implanting a short electrode, thereby allowing use of low-frequency acoustic stimulation.