Reimplantation with a conventional length electrode following residual hearing loss in four hybrid implant recipients

Hybrid Cochlear Implant Outcomes and Improving Outcomes With Electric-Acoustic Stimulation

INTRODUCTION

Electric-acoustic stimulation (EAS) provides cochlear implant (CI) recipients with preserved low-frequency acoustic hearing in the implanted ear affording auditory cues not reliably transmitted by the CI including fundamental frequency, temporal fine structure, and interaural time differences (ITDs). A prospective US multicenter clinical trial was conducted examining the safety and effectiveness of a hybrid CI for delivering EAS.

MATERIALS AND METHODS

Fifty-two adults (mean age 59.9 yr) were enrolled in the study and followed up to 5 years postactivation. Testing included unaided and aided audiometric thresholds, speech perception (Consonant-Nucleus-Consonant [CNC] words in quiet and AzBio sentences +5 dB SNR), and patient-reported outcomes (Speech, Spatial, and Qualities of Hearing Scale).

RESULTS

Functionally aidable hearing, defined as low-frequency pure-tone average (125-500 Hz) <80 dB HL, was maintained for 77% of patients through 1 year, with 66.7% maintaining through 5 years. Speech perception was significantly improved at all postoperative timepoints compared with preoperative performance with hearing aid(s), and patient-reported outcomes indicated significantly improved subjective speech understanding, spatial hearing, and sound quality. Participants with preserved acoustic hearing using EAS reported significantly higher subjective spatial hearing and sound quality than participants with electric-only hearing in the implanted ear.

DISCUSSION

Patients with high-frequency hearing loss demonstrate significant long-term benefit with a hybrid CI including high rates of functional hearing preservation, significantly improved speech perception, and subjective patient-reported outcomes. EAS with binaural acoustic hearing affords benefit for subjective spatial hearing and sound quality beyond CI listening configurations using monaural acoustic hearing.

Electrode array positioning after cochlear reimplantation from single manufacturer

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 (M ¯ ), 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, M ¯ , and AID were compared.

RESULTS

Mean change in M ¯ 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.

Slim Modiolar Electrode Placement in Candidates for Electroacoustic Stimulation

OBJECTIVES

To determine rates of hearing preservation and performance in patients who met candidacy for electroacoustic stimulation (EAS) and were implanted with a slim modiolar electrode (CI532 or CI632).

DESIGN

Adult patients meeting Food and Drug Administration criteria for electroacoustic stimulation (preoperative low-frequency pure-tone average [LFPTA] less than 60 dB at 125, 250, and 500 Hz and monosyllabic word scores between 10% and 60% in the ear to be implanted), who received a slim modiolar electrode were included. Main outcome measures included rates of hearing preservation, defined as a LFPTA ≤80 dB at 125, 250, and 500 Hz, as well as postoperative low-frequency pure-tone threshold shifts, consonant-Nucleus-Consonant (CNC) word scores and AzBio sentences in noise scores.

RESULTS

Forty-six patients met inclusion criteria during a 4-year period. Mean (standard deviation) preoperative LFPTA was 34.5 (13.0) dB, and 71.7% had preserved hearing at initial activation. The mean LFPTA shift in patients who preserved hearing at initial activation was 19.7 (14.6) dB, compared with 62.6 (17.7) dB in patients who did not preserve hearing as per our definition. Perioperative steroid use was not different in patients with and without preserved hearing (X 2 (1, N = 46) = 0.19, p = .67, V = 0.06). One year after surgery, 57% of patients had a decline in LFPTA >80 dB and were no longer considered candidates for EAS, with 34.7% still retaining low-frequency thresholds ≤80 dB. CNC word scores at 1 year were 69.9% and 61.4% among individuals with and without preserved low-frequency hearing respectively, measured in their CI ear alone, in their regular listening condition of EAS or electric only ( t (32) = 1.13, p = 0.27, d = 0.39, 95% CI = -6.51, 22.86). Device use time did not differ between groups. Among adults with preserved residual hearing at 1 year (n = 16), 44% used EAS, although there was no significant difference in performance between EAS users and nonusers with preserved hearing. Loss of residual hearing over time did not result in a decline in speech perception performance.

CONCLUSION

The present study demonstrated favorable early rates of hearing preservation with a slim modiolar array. Performance was not significantly different in individuals with and without preserved low-frequency acoustic hearing, independent of EAS use. Compared with reports of short electrode use, the loss of residual hearing in patients implanted with this array did not impact speech perception performance.

Literature Review on the Distribution of Spiral Ganglion Cell Bodies inside the Human Cochlear Central Modiolar Trunk

This study aims to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCBs) in the central modiolar trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A detailed PubMed search was performed using the key words "human spiral ganglion cell population," "analysis of spiral ganglion cell population," "survival of human spiral ganglion cells," "human Rosenthal's canal," "human ganglion cell counts," and "distribution of human spiral ganglion cells" to identify articles published between 1931 and 2019. The articles were included if the number of SGCBs in the four segments of the human cochlea and angular depth distribution of the SGCBs were mentioned. Out of the 237 articles that were initially identified, 20 articles met the inclusion criteria. The presence of SGCBs inside the Rosenthal's canal (RC) in the modiolar trunk extended to an angular depth of 630°-680°, which is close to the end of the second turn of the cochlea. SGCBs in Segment-IV of the cochlea account for approximately 25-30% of the entire SGCB population, regardless of the cochlear condition (normal vs. pathologic). In normal-hearing subjects, the total number of SGCB cases ranged between 23,910 and 33,702; in patients with hearing loss, the same was between 5,733 and 28,220. This literature review elaborates on the current state of knowledge regarding the number and distribution of SGCBs in the human cochlea.

Presence of the spiral ganglion cell bodies beyond the basal turn of the human cochlea

The purpose of this study was to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCB) in the central modiolus trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A literature review was performed using the key words 'human spiral ganglion cell population', 'analysis of spiral ganglion cell population', 'survival of human spiral ganglion cells', 'human Rosenthal's canal', 'human ganglion cell counts', and 'distribution of human spiral ganglion cells' to identify articles published between 1968 and 2018. Articles were included if the number of SGCB in the four segments of the human cochlea and angular depth distribution of the SGCB were stated. Of 236 articles initially identified, 19 articles met the inclusion criteria. SGCB inside the Rosenthal's canal (RC) in the modiolus trunk extended to an angular depth of 630-680° which is near the end of the second turn of the cochlea. SGCBs in Segment IV of the cochlea account for approximately 25-30% of the entire SGCB population irrespective of the cochlear condition (normal vs. pathologic). In normal hearing subjects, the total number of SGCB ranged between 23,910 and 33,702 and in patients with hearing loss between 5733 and 28,220. This literature review elaborates on the current state of knowledge about the number and distribution of SGCB in the human cochlea.

Surgical approach for complete cochlear coverage in EAS-patients after residual hearing loss

Introduction

In cases with residual-hearing (RH) loss after cochlear implantation, a safe method is needed to provide full spectral resolution and as much auditory information as possible without implant replacement. Aim of this study was to prove the feasibility of accessing a partially inserted cochlear-implant-electrode for complete insertion to its maximum length through the external ear canal using a transcanal approach.

Methods

Two CI electrodes were customized with 18 stimulating channels. The electrode design enables the use of 12 active channels available for electrical stimulation inside the cochlea both after partial and full insertion. 10 CI electrodes were implanted in 10 fresh human cadaveric temporal bones. After initial partial insertion by posterior tympanotomy, the electrode was inserted to its maximum length via a transcanal approach. Radiographs and CT scans were performed to confirm the electrode position. The electrodes were investigated via x-ray after removal.

Results

X-ray and CT-scans confirmed the electrode prototypes covering an angular insertion depth between 236° to 307° after initial insertion. Accessing the electrode in the middle ear space was feasible and insertion to its full length was successful. Post-insertion CT confirmed insertion of the 28mm and 31.5mm electrode arrays covering an angular insertion depth between 360° and 540° respectively. No tip foldovers were detected.

Conclusion

This study confirms the feasibility of extending the electrode insertion to its maximum insertion length using a transcanal approach in temporal bone specimens. This constitutes a second stage procedure on demand in EAS-surgery. This may be beneficial for EAS-patients providing electrical stimulation beyond the basal turn of the cochlea once the functional residual hearing is lost, without replacing the entire CI.

Speech Recognition Outcomes After Cochlear Reimplantation Surgery

This study compares speech recognition outcomes before and after cochlear reimplantation surgery, in relation to clinical factors known before and at time of surgery. Between 2006 and 2015, 2,055 adult cochlear implant surgeries were conducted at this center, of which 87 were reimplantation surgeries (4.2%). Speech recognition scores (SRS) assessed before and after reimplantation were available for 54 adults. Overall, SRS measured after reimplantation were similar to the best SRS obtained by the patient and greater than the last SRS measured before surgery. Additional complications were noted in the clinical files of all patients for which reimplantation was considered unsuccessful (16%).

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.

The ototronix MAXUM middle ear implant for severe high-frequency sensorineural hearing loss: Preliminary results

OBJECTIVES/HYPOTHESIS

To report the preliminary results of the Ototronix MAXUM middle ear implant for treatment of severe high-frequency sensorineural hearing loss.

STUDY DESIGN

Case series with chart review.

METHODS

Six consecutive ears with severe high-frequency sensorineural hearing loss (≥75 dB HL at 2, 3, and 4 kHz) and poor aided word recognition performance (≤60% single words) underwent implantation of the MAXUM system at a single, private otologic referral center. Primary outcome measures included frequency-specific functional gain and word recognition score improvement compared to optimally fitted hearing aids.

RESULTS

Six ears, in four adult patients (two female; median age 67.5 years) were included. The median unaided preoperative high-frequency pure-tone average (HFPTA) (2, 3, and 4 kHz) was 80.0 dB (range, 75.0-85.0 dB), and the median best-aided word recognition score was 48.0% (range, 24%-60%). The median HFPTA functional gain with the MAXUM system was 47.2 dB, a 25.0 dB improvement (range, 16.7-33.3 dB) (P = .03) over optimally fit hearing aids, and the median word recognition score with MAXUM was 81.5%, a 42.0% improvement (range, 20%-48%) (P = .03) with the MAXUM middle ear implant over optimally fitted hearing aids.

CONCLUSIONS

These preliminary data demonstrate that the MAXUM middle ear implant provides superior functional gain and word recognition scores in quiet for patients with severe high-frequency sensorineural hearing loss compared to optimally fitted hearing aids. Future studies with greater patient numbers and patient reported outcome measures are needed to confirm these promising but preliminary results.

LEVEL OF EVIDENCE

4 Laryngoscope, 126:2124-2127, 2016.

Treating hearing disorders with cell and gene therapy

Hearing loss is an increasing problem for a substantial number of people and, with an aging population, the incidence and severity of hearing loss will become more significant over time. There are very few therapies currently available to treat hearing loss, and so the development of new therapeutic strategies for hearing impaired individuals is of paramount importance to address this unmet clinical need. Most forms of hearing loss are progressive in nature and therefore an opportunity exists to develop novel therapeutic approaches to slow or halt hearing loss progression, or even repair or replace lost hearing function. Numerous emerging technologies have potential as therapeutic options. This paper details the potential of cell- and gene-based therapies to provide therapeutic agents to protect sensory and neural cells from various insults known to cause hearing loss; explores the potential of replacing lost sensory and nerve cells using gene and stem cell therapy; and describes the considerations for clinical translation and the challenges that need to be overcome.

Effects of loss of residual hearing on speech performance with the CI422 and the Hybrid-L electrode

OBJECTIVE

Preservation of residual low-frequency hearing has become a priority in cochlear implantation. The purpose of this study was to compare rates of hearing preservation and effects on performance of loss of low-frequency acoustic hearing with two different length electrodes.

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary Care Hospital.

PATIENTS

Twelve patients were implanted with the CI422 a slim-straight electrode; the second group consisted of 10 patients implanted with the Hybrid-L, a shorter hearing preservation electrode.

MAIN OUTCOME MEASURE

Audiometric thresholds and speech perception measures.

RESULTS

At 1 year, 3/10 (30%) patients with the Hybrid-L and 7/12 (58%) patients with the CI422 lost residual acoustic hearing resulting in a profound hearing loss in the implanted ear. In comparing these patients in particular, mean CNC words in the implanted ear were 72% in the CI422 electrode group and 15% in the Hybrid-L electrode group at 1 year (P = 0.03). While hearing preservation rates with the Hybrid-L tended to be better, among recipients who lost residual hearing, speech perception was better in those with the longer CI422 electrode.

CONCLUSIONS

With emphasis on preservation of residual hearing, patients need to be counseled regarding possible outcomes and options should loss of residual hearing occur following implantation. While shorter electrodes may have better rates of hearing preservation, the patients with the longer straight electrode in our study had significantly better speech understanding following the loss of residual hearing.

Cochlear implantation: a biomechanical prosthesis for hearing loss

Cochlear implants are a medical prosthesis used to treat sensorineural deafness, and one of the greatest advances in modern medicine. The following article is an overview of cochlear implant technology. The history of cochlear implantation and the development of modern implant technology will be discussed, as well as current surgical techniques. Research regarding expansion of candidacy, hearing preservation cochlear implantation, and implantation for unilateral deafness are described. Lastly, innovative technology is discussed, including the hybrid cochlear implant and the totally implantable cochlear implant.

Revision cochlear implantation with different electrodes can cause incomplete electrode insertion and poor performance

OBJECTIVES/HYPOTHESIS

To review our experiences with revision cochlear implantation (CI), to assess revision CI efficacy, and to find factors that cause incomplete electrode insertion.

STUDY DESIGN

Retrospective chart review of revision CI from 2004 to 2011.

SETTING

Academic tertiary referral center.

PATIENTS

Twenty-two patients who underwent revision CI.

INTERVENTIONS(S)

Revision cochlear implant surgery, explanted device analysis, electrode analysis for a newly implanted device, measurement of electrode insertion depth on postoperative radiographic evaluation, and postoperative speech perception test by open-set testing.

MAIN OUTCOME MEASURE(S)

Surgical outcomes, postoperative performance, and analysis of used electrodes.

RESULTS

Approximately 2.7% (22/816) of CI recipients underwent revision surgery. The reasons for revision surgery were device failure (n = 14) and medical reason (n = 8). Cochlear implantation was performed at an average of 4.7 years after initial operation. Seventeen patients underwent revision CI with an electrode that was the same as or similar to the initial one, and all electrodes were fully inserted. Different electrode types were used in the remaining 5 patients. Interestingly, 4 of the 5 had incomplete electrode insertion. Among the 4 patients, 2 had poorer open set sentence scores after revision than after initial surgery.

CONCLUSION

In this study, full electrode insertion was achieved in all cases where the same type of electrode was used during initial and revision CI. In contrast, we noticed incomplete insertion in 4 of 5 patients who had revision electrodes that differed from initial electrodes. While incomplete electrode insertion does not necessitate poor speech performance, some patients with incomplete electrode insertion certainly experience it. Therefore, electrode selection requires circumspection in revision CI. Choosing a thinner electrode for revision CI may reduce the possibility of incomplete electrode insertion.