Cochlear Implant Recipients With Electrodes in the Acoustic Region: Long-Term Hearing Preservation.

To analyze the relationship of electrode array (EA) type and position on hearing preservation longevity following cochlear implantation. Retrospective chart review. Tertiary referral center. Adult cochlear implant recipients between 2013 and 2019 with hearing preserved postoperatively and postoperative CT scans. CT scan analysis of EA position. Stepwise regression to determine influence of EA position, EA type, and patient demographics on postoperative low frequency hearing. Low frequency pure tone average (LFPTA), LFPTA shift, angular insertion depth, base insertion depth, scalar position, mean perimodiolar distance. Of 792 cochlear implant recipients, 121 had preoperative LFPTA <80 dB HL with 60 of the 121 (49.6%) implanted with straight, 32 (26.4%) with precurved, styletted, and 29 (24.0%) implanted precurved, nonstyletted EA. Mean follow up was 28.6 months (range 1-103). There was no statistically significant difference in activation, 6- and 12-month, and last follow-up LFPTA (125, 250, and 500 Hz) shift based on EA type (straight p = 0.302, precurved, styletted p = 0.52, precurved, nonstyletted p = 0.77). Preoperative LFPTA and age of implantation were significant predictors of LFPTA shift at activation, accounting for 30.8% of variance ( F [2, 113] = 26.603, p < 0.0001). LFPTA shift at activation, scalar position, and base insertion depth were significant predictors of variability and accounted for 39.1% of variance in LFPTA shift at 6 months ( F [3, 87] = 20.269, p < 0.0001). Only LFPTA shift at 12 months was found to be a significant predictor of LFPTA shift at last follow up, accounting for 41.0% of variance ( F [1, 48] = 32.653, p < 0.0001). Patients had excellent long-term residual hearing regardless of EA type. Age, preoperative acoustic hearing, and base insertion depth may predict short term preservation, while 12-month outcomes significantly predicted long-term hearing preservation.

To examine the effects of scala tympani (ST) volume, cochlear duct length (CDL), and angular insertion depth (AID) on low-frequency hearing preservation for cochlear implant (CI) recipients of lateral wall electrode arrays. A retrospective review identified 45 adult CI recipients of 24-, 28-, or 31.5-mm lateral wall electrode arrays with preoperative unaided hearing thresholds ≤45 decibel hearing level (dB HL) at 250 Hz. All patients underwent preoperative and postoperative computed tomography to evaluate cochlear morphology and electrode array position. A linear mixed effects model evaluated effects of ST volume, CDL, AID, preoperative low-frequency pure-tone average (LFPTA; 125, 250, and 500 Hz), age at surgery, and biological sex on the postoperative change in LFPTA at activation and 6 months post-activation. There were significant main effects of ST volume (p = 0.044), age (p = 0.028), and biological sex (p = 0.003), indicating better low-frequency hearing preservation for CI recipients with larger ST volumes, younger age at surgery, and female biological sex. Although CDL positively correlated with ST volume (r = 0.74, p < 0.001), there was no significant main effect of CDL (p = 0.367). A broad range in AID of the most apical electrode contact was observed (301.4°-681.8°); however, there was no significant main effect of AID on low-frequency hearing preservation (p = 0.700). During the initial 6 months following implantation, intrinsic factors such as cochlear morphology may have a greater impact on low-frequency hearing preservation than apical positioning of a flexible lateral wall electrode array when using soft surgical techniques. 3 Laryngoscope, 2024.

Round window approach and cochleostomy approach can have different depth of electrode insertion during cochlear implantation which itself can alter the audiological outcomes in cochlear implant. The current study was conducted to determine the difference in the depth of electrode insertion via cochleostomy and round widow approach when done serially in same temporal bone. This is a cross-sectional study conducted in the Department of Otorhinolaryngology in conjunction with Department of Anatomy and Department of Diagnostic and Interventional Radiology over a period of 1year. 12-electrode array insertion was performed via either approach (cochleostomy or round window) in the cadaveric temporal bone. HRCT temporal bone scan of the implanted temporal bone was done and depth of insertion and various cochlear parameters were calculated. A total of 12 temporal bones were included for imaging analysis. The mean cochlear duct length was 32.892mm; the alpha and beta angles were 58.175° and 8.350°, respectively. The mean angular depth of electrode insertion via round window was found to be 325.2° (SD = 150.5842) and via cochleostomy 327.350 (SD = 112.79) degree and the mean linear depth of electrode insertion via round window was found to be 18.80 (SD = 4.4962) mm via cochleostomy 19.650 (SD = 3.8087) mm, which was calculated using OTOPLAN 1.5.0 software. There was a statically significant difference in linear depth of insertion between round window and cochleostomy. Although the angular depth of insertion was higher in CS group, there was no statistically significant difference with round window type of insertion. The depth of electrode insertion is one of the parameters that influences the hearing outcome. Linear depth of electrode insertion was found to be more in case of cochleostomy compared to round window approach (p = 0.075) and difference in case of angular depth of electrode insertion existed but not significant (p = 0.529).

Describe audiologic outcomes in hearing preservation cochlear implantation (CI) using a precurved electrode array inserted using an external sheath and evaluate association of electrode positioning and preservation of residual hearing. Retrospective review. Tertiary otologic center. Twenty-four adult patients who underwent hearing preservation CI with precurved electrode array. CI, intraoperative computed tomography (CT) OUTCOME MEASURES:: Audiologic measures (consonant-nucleus-consonant [CNC] words, AzBio sentences, low-frequency pure tone averages [LFPTA]) and electrode location (scalar location, electrode-to-modiolus distance ((Equation is included in full-text article.)), angular insertion depth). Twenty-four adults with less than 80 dB LFPTA with a precurved electrode array inserted using an external sheath; 16 underwent intraoperative CT. LFPTA was 58.5 dB HL preoperatively, with a 17.3 dB threshold shift at CI activation (p = 0.005). CNC word scores improved from 6% preoperatively to 64% at 6 months postoperatively (p < 0.0001). There was one scalar translocation and no tip fold-overs. The average angular insertion depth was 388.2 degrees, and the average (Equation is included in full-text article.)across all electrodes was 0.36 mm. Multivariate regression revealed a significant correlation between CNC scores at 6 months and angular insertion depth (p = 0.0122; r = 0.45, adjusted r = 0.35). Change in LFPTA was not significantly associated with angular insertion depth or (Equation is included in full-text article.). A low rate of translocation allows a precurved electrode array inserted using an external sheath to maintain hearing preservation rates comparable to straight electrode arrays. With scala tympani insertion, angular insertion depth is a positive marker of improved speech performance postoperatively but may be a confounder variable based on individual cochlear size.

Despite successful preservation of low-frequency hearing in patients undergoing cochlear implantation (CI) with shorter electrode lengths, there is still controversy regarding which electrodes maximize hearing preservation (HP). The thin straight electrode array (TSEA) has been suggested as a full cochlear coverage option for HP. However, very little is known regarding its HP potential. A retrospective review was performed at two tertiary academic medical centers, reviewing the electronic records for 52 patients (mean, 58.2 yr; range, 11-85 yr) implanted with the Cochlear Nucleus CI422 Slim Straight (Centennial, CO, USA) electrode array, referred to herein as the thin straight electrode array or TSEA. All patients had a preoperative low-frequency pure-tone average (LFPTA) of 85 dB HL or less. Hearing thresholds were measured at initial activation (t1) and 6 months after activation (t2). HP was assessed by evaluating functional HP using a cutoff level of 85 dB HL PTA. At t1, 54% of the subjects had functional hearing; 33% of these subjects had an LFPTA between 71 and 85 dB HL, and 17% had an LFPTA between 56 and 70 dB HL. At t2, 47% of the patients had functional hearing, with 31% having an LFPTA between 71 and 85 dB HL. Preliminary research suggests that the TSEA has the potential to preserve functional hearing in 54% of patients at t1. However, 22% (n = 6) of the patients who had functional hearing at t1 (n = 28) lost their hearing between t1 and t2. Further studies are needed to evaluate factors that influence HP with the TSEA electrode and determine the speech perception benefits using electric and acoustic hearing over electric alone.

It has long been known that cochlear implantation may cause loss of residual hearing and vestibular function. Different insertion depths may cause varying degrees of intracochlear trauma in the apical region of the cochlea. The present study investigated the correlation between the insertion depth and postoperative loss of residual hearing and vestibular function. Thirty-nine adults underwent unilateral cochlear implantation. One group received a Med-El +Flex electrode array (24 mm; n = 4), 1 group received a Med-El +Flex electrode array (28 mm; n = 18), and 1 group received a Med-El +Flex electrode array (31.5 mm; n = 17). Residual hearing, cervical vestibular-evoked myogenic potentials, videonystagmography, and subjective visual vertical/horizontal were explored before and after surgery. The electrode insertion depth and scalar position were examined with high-resolution rotational tomography after implantation in 29 subjects. There was no observed relationship between the angular insertion depth (405° to 708°) and loss of low-frequency pure-tone average. Frequency-specific analysis revealed a weak relationship between the angular insertion depth and loss of hearing at 250 Hz (R= 0.20; p = 0.02). There was no statistically significant difference in the residual hearing and vestibular function between the +Flex and the +Flex electrode array. Eight percent of the cases had vertigo after surgery. The electrode arrays were positioned inside the scala tympani and not scala vestibuli in all subjects. In 18% of the cases, the +Flex electrode array was not fully inserted. The final outcome in residual hearing correlates very weakly with the angular insertion depth for depths above 405°. Postoperative loss of vestibular function did not correlate with the angular insertion depth or age at implantation. The surgical protocol used in this study seems to minimize the risk of postoperative vertigo symptoms.

To investigate the incidence of electrode contacts within the functional acoustic hearing region in cochlear implant (CI) recipients and to assess its influence on speech recognition for electric-acoustic stimulation (EAS) users. Retrospective review. Tertiary referral center. One hundred five CI recipients with functional acoustic hearing preservation (≤80 dB HL at 250 Hz). Cochlear implantation with a 24-, 28-, or 31.5-mm lateral wall electrode array. Angular insertion depth (AID) of individual contacts was determined from imaging. Unaided acoustic thresholds and AID were used to calculate the proximity of contacts to the functional acoustic hearing region. The association between proximity values and speech recognition in quiet and noise for EAS users at 6 months postactivation was reviewed. Sixty percent of cases had one or more contacts within the functional acoustic hearing region. Proximity was not significantly associated with speech recognition in quiet. Better performance in noise was observed for cases with close correspondence between the most apical contact and the upper edge of residual hearing, with poorer results for increasing proximity values in either the basal or apical direction ( r14 = 0.48, p = 0.043; r18 = -0.41, p = 0.045, respectively). There was a high incidence of electrode contacts within the functional acoustic hearing region, which is not accounted for with default mapping procedures. The variability in outcomes across EAS users with default maps may be due in part to electric-on-acoustic interference, electric frequency-to-place mismatch, and/or failure to stimulate regions intermediate between the most apical electrode contact and the functional acoustic hearing region.

The spatial position of a cochlear implant (CI) electrode array affects the spectral cues provided to the recipient. Differences in cochlear size and array length lead to substantial variability in angular insertion depth (AID) across and within array types. For CI-alone users, the variability in AID results in varying degrees of frequency-to-place mismatch between the default electric frequency filters and cochlear place of stimulation. For electric-acoustic stimulation (EAS) users, default electric frequency filters also vary as a function of residual acoustic hearing in the implanted ear. The present study aimed to (1) investigate variability in AID associated with lateral wall arrays, (2) determine the subsequent frequency-to-place mismatch for CI-alone and EAS users mapped with default frequency filters, and (3) examine the relationship between early speech perception for CI-alone users and two aspects of electrode position: frequency-to-place mismatch and angular separation between neighboring contacts, a metric associated with spectral selectivity at the periphery. One hundred one adult CI recipients (111 ears) with MED-EL Flex24 (24 mm), Flex28 (28 mm), and FlexSOFT/Standard (31.5 mm) arrays underwent postoperative computed tomography to determine AID. A subsequent comparison was made between AID, predicted spiral ganglion place frequencies, and the default frequency filters for CI-alone (n = 84) and EAS users (n = 27). For CI-alone users with complete insertions who listened with maps fit with the default frequency filters (n = 48), frequency-to-place mismatch was quantified at 1500 Hz and angular separation between neighboring contacts was determined for electrodes in the 1 to 2 kHz region. Multiple linear regression was used to examine how frequency-to-place mismatch and angular separation of contacts influence consonant-nucleus-consonant (CNC) scores through 6 months postactivation. For CI recipients with complete insertions (n = 106, 95.5%), the AID (mean ± standard deviation) of the most apical contact was 428° ± 34.3° for Flex24 (n = 11), 558° ± 65.4° for Flex28 (n = 48), and 636° ± 42.9° for FlexSOFT/Standard (n = 47) arrays. For CI-alone users, default frequency filters aligned closely with the spiral ganglion map for deeply inserted lateral wall arrays. For EAS users, default frequency filters produced a range of mismatches; absolute deviations of ≤ 6 semitones occurred in only 37% of cases. Participants with shallow insertions and minimal or no residual hearing experienced the greatest mismatch. For CI-alone users, both smaller frequency-to-place mismatch and greater angular separation between contacts were associated with better CNC scores during the initial 6 months of device use. There is significant variability in frequency-to-place mismatch among CI-alone and EAS users with default frequency filters, even between individuals implanted with the same array. When using default frequency filters, mismatch can be minimized with longer lateral wall arrays and insertion depths that meet the edge frequency associated with residual hearing for CI-alone and EAS users, respectively. Smaller degrees of frequency-to-place mismatch and decreased peripheral masking due to more widely spaced contacts may independently support better speech perception with longer lateral wall arrays in CI-alone users.

Hearing Preservation in Patients With a Cochlear Implant

IntroductionCompared to unilateral cochlear implantation, bilateral cochlear implantation demonstrates multiple advantages in speech understanding in noise and sound localization, especially when acoustic hearing is preserved in both ears. However, outcomes and factors influencing acoustic hearing preservation following cochlear implant (CI) remains poorly understood. Patients receiving sequential cochlear implantation are a valuable population to investigate as studying bilateral ears allows for a high degree of control of individual factors that may be affecting trends in hearing.MethodsThis is a retrospective analysis of prospectively collected data. Twenty-three subjects met criteria for CI with residual hearing, defined as low frequency (LF) pure tone average (PTA) of 65 dB or less at 125, 250, and 500 Hz, and received sequential cochlear implantation were included in the study. Audiometric data was collected on all subjects pre/post-operatively. Speech perception was assessed in everyday listening conditions pre/post-implantation using CNC and AzBio materials.ResultsBilateral hearing preservation was achieved in 56.5% (13/23) of patients. Of the 16 patients with hearing preservation following the first implant, 81% (13/16) of them achieved bilateral hearing preservation following the second implant in the contralateral ear. Speech understanding scores improved after sequential cochlear implantation (p = 0.019). There was no significant correlation between length of electrode array and LFPTA in either ear (p = 0.464 and p = 0.699). About half (49%) of subjects retained functional acoustic hearing in the initially implanted ear 11 years post-implantation. There was significantly decreased retention rate of hearing preservation in the second ear (p = 0.014). Age at implantation overall significantly associated with loss of hearing preservation (p = 0.040).DiscussionHearing preservation following sequential cochlear implantation improved everyday listening abilities despite greater loss of acoustic hearing in the sequentially implanted ear. Age at implantation was the only factor observed to correlate with hearing preservation over time. Given known histopathological evidence of inflammation following cochlear implantation, it is likely that an immune mediated process may be responsible for delayed and greater loss of hearing in the sequentially implanted ear. Therefore, individuals receiving sequential cochlear implantation are an excellent population in future studies investigating the inflammatory and immunomodulatory mechanisms that may be responsible for delayed hearing loss following cochlear implantation.

1) Examine angular insertion depths (AID) and scalar location of Med-El (GmbH Innsbruck, Austria) electrodes; and 2) determine the relationship between AID and audiologic outcomes controlling for scalar position. Retrospective review. Postlingually deafened adults undergoing cochlear implantation with Flex 24, Flex 28, and Standard electrode arrays (Med-El) were identified. Patients with preoperative and postoperative computed tomography scans were included so that electrode location and AID could be determined. Outcome measures were 1) speech perception in the cochlear implant (CI)-only condition, and 2) short-term hearing preservation. Forty-eight implants were included; all electrodes (48 of 48) were positioned entirely within the scala tympani. The median AID was 408° (interquartile [IQ] range 373°-449°) for Flex 24, 575° (IQ range 465°-584°) for Flex 28, and 584° (IQ range 368°-643°) for Standard electrodes (Med-El). The mean postoperative CNC score was 43.7% ± 21.9. A positive correlation was observed between greater AID and better CNC performance (r = 0.48, P < 0.001). Excluding patients with postoperative residual hearing, a strong correlation between AID and CNC persisted (r = 0.57, P < 0.001). In patients with preoperative residual hearing, mean low-frequency pure-tone average (PTA) shift was 27 dB ± 14. A correlation between AID and low-frequency PTA shift at activation was noted (r = 0.41, P = 0.04). Favorable rates of scala tympani insertion (100%) were observed. In the CI-only condition, a direct correlation between greater AID and CNC score was noted regardless of postoperative hearing status. Deeper insertions were, however, associated with worse short-term hearing preservation. When patients without postoperative residual hearing were analyzed independently, the relationship between greater insertion depth and better performance was strengthened. 4. Laryngoscope, 127:2352-2357, 2017.

Objective To investigate whether revision surgery with the same device results in a change in three key indicators of electrode positioning: scalar location, mean modiolar distance (), and angular insertion depth (AID). Methods Retrospective analysis of a cochlear implant database at a university-based tertiary medical center. Intra-operative CT scans were obtained after initial and revision implantation. Electrode array (EA) position was calculated using auto-segmentation techniques. Initial and revision scalar location, , and AID were compared. Results Mean change in for all ears was −0.07 mm (SD 0.24 mm; P = 0.16). The mean change in AID for all ears was −5° (SD 67°; P = 0.72). Three initial implantations with pre-curved EAs resulted in a translocation from Scala Tympani (ST) to Scala Vestibuli (SV). Two remained translocated after revision, while one was corrected when revised with a straight EA. An additional five translocations occurred after revision. Conclusions In this study examining revision cochlear implantation from a single manufacturer, we demonstrated no significant change in key indicators of EA positioning, even when revising with a different style of electrode. However, the revision EA is not necessarily confined by the initial trajectory and there may be an increased risk of translocation.

ABSTRACTObjective(s)Robotic‐assisted electrode array (EA) insertion is a promising technique that may enhance hearing preservation in cochlear implant (CI) surgery. The purpose of our study is to understand the extent to which robotic‐assisted EA insertion improves hearing preservation.MethodsTwenty‐four adult patients underwent CI surgery with manual EA insertion and 27 adult patients underwent CI surgery with robotic‐assisted EA insertion using the iotaSOFT system. The EAs used included the Flex 20/24/26. The primary outcome variable was low frequency pure‐tone average (LFPTA), defined as mean audiometric threshold at 125, 250, and 500 Hz. This was measured preoperatively, at initial activation (within 4 weeks of surgery), and subsequently at 2 weeks, 3 months, 6 months, and 1 year. Functional acoustic hearing was defined as LFPTA < 80 dB HL.ResultsSeventeen out of 24 patients (71%) in the manual insertion group and 23 out of 27 patients (85%) in the robotic‐assisted EA insertion group had preserved functional acoustic hearing (< 80 dB HL) up till 1 year (Fisher's exact test (two‐tailed) is not statistically significant, p = 0.31). The number needed to treat with robotic‐assisted EA insertion to prevent one additional negative outcome of loss of functional acoustic hearing would be 7 (1/0.14).ConclusionRobotic‐assisted EA insertion is associated with improved hearing preservation over 1 year compared with manual insertion. Hearing preservation leads to improved outcomes and therefore every effort should be made to preserve the delicate structure and function of the cochlea during EA insertion. Robotic‐assisted EA insertion advances that objective.Level of Evidence: III (cohort study).

To evaluate the relationship between intrascalar electrode location, electrode type (lateral wall, perimodiolar, and midscala), and angular insertion depth on residual hearing in cochlear implant (CI) recipients. Tertiary academic hospital. Adult CI patients with functional preoperative residual hearing with preoperative and postoperative CT scans. Audiological assessment after CI. Electrode location, angular insertion depth, residual hearing post-CI, and word scores with CI (consonant-nucleus-consonant [CNC]). Forty-five implants in 36 patients (9 bilateral) were studied. Thirty-eight electrode arrays (84.4%) were fully inserted in scala tympani (ST), 6 (13.3%) crossed from ST to scala vestibuli (SV), and 1 (2.2%) was completely in SV. Twenty-two of the 38 (57.9%) with full ST insertion maintained residual hearing at 1 month compared with 0 of the 7 (0%) with non-full ST insertion (p = 0.005). Three surgical approaches were used: cochleostomy (C) 6/44, extended round window (ERW) 8/44, and round window (RW) 30/44. C and ERW were small group to compare with RW approaches. However if we combine C + ERW, then RW has higher chance of full ST insertion (p = 0.014). Looking at the full ST group, neither age, sex, nor electrode type demonstrated statistically significant associations with hearing preservation (p = 0.646, p = 0.4, and p = 0.929, respectively). The median angular insertion depth was 429° (range, 373°-512°) with no significant difference between the hearing and nonhearing preserved groups (p = 0.287). Scalar excursion is a strong predictor of losing residual hearing. However, neither age, sex, electrode type, nor angular insertion depth was correlated with hearing preservation in the full ST group. Techniques to decrease the risk of electrode excursion from ST are likely to result in improved residual hearing and CI performance.

To assess the variance in cochlear implant electrode insertion depth in degrees around the modiolus (angular insertion depth) in free-fitting and perimodiolar electrode arrays. Twenty-eight fresh human temporal bones were implanted with free-fitting cochlear implant electrodes, and 18 bones were implanted using perimodiolar electrode arrays. Specimens were embedded, and 2-dimensional radiographs were obtained to assess angular insertion depths. Histologic serial sections of undecalcified bones were then evaluated to analyze intracochlear electrode positions. Finally, linear surgical insertion depths (in millimeters) were correlated with angular insertion depth (degrees around the modiolus). A moderate variance of angular insertion depth was documented for both free-fitting and perimodiolar electrode arrays. Full insertions into the scala tympani ranged from 540 to 630 degrees with free-fitting arrays and from 270 to 375 degrees with perimodiolar electrodes. In free-fitting devices, a linear relationship between linear (in millimeters) and angular (degrees) insertion depths was observed. Insertions into scala vestibuli were observed in 9 of 28 and 5 of 18 of the specimens for free-fitting and perimodiolar electrodes, respectively. Additionally, scala vestibuli insertions showed greater angular insertion depths when compared with scala tympani implantations. Variances in angular insertion depths seem to be moderate and similar in free-fitting and perimodiolar electrode arrays. Scala vestibuli insertions showed greater angular insertion depths than comparable insertions into the scala tympani. In perimodiolar electrodes, angular insertion depths equal or greater than 390 degrees suggested scala vestibuli placement.