Auditory Brainstem Implant Users Research Articles

Auditory Brainstem Implant Outcomes in Tumor andNontumor Patients: A Systematic Review.

To elucidate the differences in auditory performance between auditory brainstem implant (ABI) patients with tumor or nontumor etiologies. PubMed, Embase, and Web of Science Core Collection from 1990 to 2021. We included published studies with 5or more pediatric or adult ABI users. Auditory outcomes and side effects were analyzed with weighted means for closed-set, open-set speech, and categories of auditory performance (CAP) scores. Overall performance was compared using an Adult Pediatric Ranked Order Speech Perception (APROSPER) scale created for this study. Thirty-six studies were included and underwent full-text review. Data were extracted for 662 tumor and 267 nontumor patients. 83% were postlingually deafened and 17% were prelingually deafened. Studies that included tumor ABI patients had a weighted mean speech recognition of 39.2% (range: 19.6%-83.3%) for closed-set words, 23.4% (range: 17.2%-37.5%) for open-set words, 21.5% (range: 2.7%-48.4%) for open-set sentences, and 3.1 (range: 1.0-3.2) for CAP scores. Studies including nontumor ABI patients had a weighted mean speech recognition of 79.8% (range: 31.7%-84.4%) for closed-set words, 53.0% (range: 14.6%-72.5%) for open-set sentences, and 2.30 (range: 2.0-4.7) for CAP scores. Mean APROSPER results indicate better auditory performance among nontumor versus tumor patients (3.5 vs 3.0, P = .04). Differences in most common side effects were also observed between tumor and nontumor ABI patients. Auditory performance is similar for tumor and nontumor patients for standardized auditory test scores. However, the APROSPER scale demonstrates better ABI performance for nontumor compared to tumor patients.

Hearing Rehabilitation in Patients With Neurofibromatosis Type 2: The Quebec's Experience With Auditory Implants.

To review a single-center experience with hearing rehabilitation in patients with neurofibromatosis type 2 (NF2) and to describe the auditory outcomes of cochlear implants (CIs) and auditory brainstem implants (ABI) in this population. Retrospective case series. Tertiary referral center. Twelve adult patients with NF2 who received a CI (n = 10) and/or an ABI (n = 5) between 2000 and 2021. Insertion of a CI and/or an ABI in NF2 patients with bilateral vestibular schwannomas (VSs). Patients' demographic data, treatment history, hearing evolution, hearing rehabilitation methods, implant details, and auditory outcomes after implantation. Among those who received a CI, five patients had a stable untreated VS, one patient underwent a cochlear nerve preserving surgery, and four patients received radiotherapy treatments. Six patients became regular users of their device. The median open-set sentence recognition scores were as follows: 0.5% preoperatively, 60% at 1 year postoperatively, and 80% on the most recent audiological evaluation. All patients with an ABI were implanted concomitantly with VS surgical excision, and three of them also received radiotherapy treatments. The median open-set sentence recognition scores were as follows: 4% preoperatively, 26% at 1 year postoperatively, and 0% on the most recent evaluation. Three patients became regular ABI users. Despite major technological advances, auditory outcomes with ABIs remain deceiving. Considering the overall improvement in postoperative auditory performances provided by CIs compared with ABIs, cochlear implantation standouts as a primary mean of hearing rehabilitation in NF2 patients.

Evaluation of auditory brainstem implant (ABI) users' auditory behavior in everyday life.

This study aims to evaluate the everyday listening status of pediatric ABI users using the Turkish ABEL questionnaire. The study included 33 parents of children with auditory brainstem implant, and 28 parents of children with cochlear implant were included as a control group. All implant users were between the ages of 4-14. Parents answered the ABEL questionnaire to assess their child's auditory behavior in their daily living environment. In addition, Categories of Auditory Performance (CAP) and Speech Intelligibility Rating (SIR) scales were used to evaluate speech perception and production. Auditory-aural, auditory awareness and ABEL total score of ABI users were statistically significantly lower than the CI group (p < 0.05). There was no statistically significant difference between the groups in the Conversational/Social skills subgroups. It was found that as the duration of ABI use increased, auditory-verbal, social skills and total scores increased significantly. In addition, correlations were obtained between ABEL total and subscale scores and CAP and SIR scores. Parents believe that their children adapt nicely to ABI and are aware of environmental sounds. This study reveals the auditory, aural, and social skills of children using ABI through the regards of their parents. This study showed that the ABEL questionnaire, which was used in previous studies to express parental views of children with hearing aids and cochlear implants, can also be used for parents of children using ABI.

Sensitivity to Pulse Rate and Amplitude Modulation in an Animal Model of the Auditory Brainstem Implant (ABI).

The auditory brainstem implant (ABI) is an auditory neuroprosthesis that provides hearing by electrically stimulating the cochlear nucleus (CN) of the brainstem. Our previous study (McInturff et al., 2022) showed that single-pulse stimulation of the dorsal (D)CN subdivision with low levels of current evokes responses that have early latencies, different than the late response patterns observed from stimulation of the ventral (V)CN. How these differing responses encode more complex stimuli, such as pulse trains and amplitude modulated (AM) pulses, has not been explored. Here, we compare responses to pulse train stimulation of the DCN and VCN, and show that VCN responses, measured in the inferior colliculus (IC), have less adaption, higher synchrony, and higher cross-correlation. However, with high-level DCN stimulation, responses become like those to VCN stimulation, supporting our earlier hypothesis that current spreads from electrodes on the DCN to excite neurons located in the VCN. To AM pulses, stimulation of the VCN elicits responses with larger vector strengths and gain values especially in the high-CF portion of the IC. Additional analysis using neural measures of modulation thresholds indicate that these measures are lowest for VCN. Human ABI users with low modulation thresholds, who score best on comprehension tests, may thus have electrode arrays that stimulate the VCN. Overall, the results show that the VCN has superior response characteristics and suggest that it should be the preferred target for ABI electrode arrays in humans.

Evaluation of the non-auditory responses in individuals with auditory brainstem implant

ObjectivesAfter auditory brainstem implant (ABI) surgery, stimulation of certain cranial nerves may result in a non-auditory response, and the electrodes that stimulate these nerves may be deactivated. The goals of this study are to compare the number of active electrodes in the initial activation and the last fitting, to investigate non-auditory response types and their frequency as a result of non-auditory stimulation, to compare the placements of deactivated electrodes as a result of non-auditory stimulation in the initial activation and the last fitting. MethodsThe computer software system was used to perform a retrospective analysis of the fitting data of 69 ABI users who underwent auditory brainstem implant surgery between January 1997 and January 2019. The non-auditory response types, deactive electrodes, and the positioning of the deactive electrodes horizontally and vertically were recorded in these users during the initial activation and the last fitting. ResultsThere was no statistically significant difference between the number of active electrodes in the initial activation and the last fitting. The proportion of the users with deactive electrodes in the initial activation and the last fitting was not statistically significant different. In the horizontal and vertical placement classification, the placement of the deactive electrodes was not statistically different between initial activation and last fitting. The most common type of non-auditory response was facial nerve stimulation at the initial activation and no auditory perception at the last fitting. According to the difference between the number of active and deactive electrodes in the initial activation and the last fitting, as well as the auditory and non-auditory responses, it was found that the ABI users were statistically different between the initial activation and the last fitting. ConclusionThe results of this study show that not only auditory but also non-auditory responses occur in most ABI users. In addition, to the best of our knowledge, this study is the first to examine the frequencies of non-auditory response types, and the placement of the electrodes that cause these responses according to horizontal and vertical classifications.

Percepção auditiva e desenvolvimento de linguagem oral após cirurgia de implante auditivo de tronco encefálico: uma revisão de escopo

ABSTRACT Purpose This scope review aims to map current evidence in relation to auditory perception of speech and oral language development in users of Auditory Brainstem Implant - ABI, to answer the following guiding question: “what do we know about the ability of auditory perception of speech and oral language in auditory brainstem implants users?” Research strategy The search was performed in the BVSalud, PubMed and SciELO databases and for gray literature the source of information Google Academic, using the descriptors: auditory brainstem implantation , language, hearing and auditory perception. Selection criteria Studies were included in which tests were applied to assess auditory perception or to verify oral language development in children and/or adults using ABI. Articles published in the last five years were included and secondary studies were excluded. Results 1767 articles were found in the databases and source of information, of which 27 studies were included. It was observed that most users of ABI become able to perceive some environmental sounds, some become able to recognize words, but few reach the recognition of sentences. Conclusion Most ABI users do not advance towards the open set auditory recognition skill and there is unanimity in recommending visual communication methods for these individuals.

Revision Surgery for Pediatric Nontumor Auditory Brainstem Implant Users: Audiological, Rehabilitative, and Surgical Outcomes.

To report the audiological, rehabilitative, and surgical outcomes of revision surgery for pediatric auditory brainstem implant (ABI) users. Retrospective cohort. Tertiary referral center. Five pediatric ABI users who had revision surgery for device malfunctions. Revision surgery for ABI malfunctions. The findings of free-field audiometry with the device, the Meaningful Auditory Integration Scale, and the pattern discrimination, word identification, sentence recognition, and expressive and receptive language tests before the device failure and after revision surgery were obtained from the patient records and compared. The revision rate for pediatric ABI was 6.45%. The Meaningful Auditory Integration Scale and expressive-receptive language scores showed improvements following revision surgery, while the aided thresholds, pattern perception, and word identification scores did not change. Individual differences in performance for these measures were observed. Equal or improved performance after the revision surgeries in the current study showed that revision surgery is successful and important for pediatric ABI users. It is essential to consider remedying the loss of auditory input in sensitive periods of pediatric development.

Assessing temporal responsiveness of primary stimulated neurons in auditory brainstem and cochlear implant users

The reasons why clinical outcomes with auditory brainstem implants (ABIs) are generally poorer than with cochlear implants (CIs) are still somewhat elusive. Prior work has focused on differences in processing of spectral information due to possibly poorer tonotopic representation and higher channel interaction with ABIs than with CIs. In contrast, this study examines the hypothesis that a potential contributing reason for poor speech perception in ABI users may be the relative lack of temporal responsiveness of the primary neurons that are stimulated by the ABI. The cochlear nucleus, the site of ABI stimulation, consists of different neuron types, most of which have much more complex responses than the auditory nerve neurons stimulated by a CI. Temporal responsiveness of primary stimulated neurons was assessed in a group of ABI and CI users by measuring recovery of electrically evoked compound action potentials (ECAPs) from single-pulse forward masking. Slower ECAP recovery tended to be associated with poorer hearing outcomes in both groups. ABI subjects with the longest recovery time had no speech understanding or even no hearing sensation with their ABI device; speech perception for the one CI outlier with long ECAP recovery time was well below average. To the extent that ECAP recovery measures reveal temporal properties of the primary neurons that receive direct stimulation form neural prosthesis devices, they may provide a physiological underpinning for clinical outcomes of auditory implants. ECAP recovery measures may be used to determine which portions of the cochlear nucleus to stimulate, and possibly allow us to enhance the stimulation paradigms.

Microstructured thin-film electrode technology enables proof of concept of scalable, soft auditory brainstem implants.

Auditory brainstem implants (ABIs) provide sound awareness to deaf individuals who are not candidates for the cochlear implant. The ABI electrode array rests on the surface of the cochlear nucleus (CN) in the brainstem and delivers multichannel electrical stimulation. The complex anatomy and physiology of the CN, together with poor spatial selectivity of electrical stimulation and inherent stiffness of contemporary multichannel arrays, leads to only modest auditory outcomes among ABI users. Here, we hypothesized that a soft ABI could enhance biomechanical compatibility with the curved CN surface. We developed implantable ABIs that are compatible with surgical handling, conform to the curvature of the CN after placement, and deliver efficient electrical stimulation. The soft ABI array design relies on precise microstructuring of plastic-metal-plastic multilayers to enable mechanical compliance, patterning, and electrical function. We fabricated soft ABIs to the scale of mouse and human CN and validated them in vitro. Experiments in mice demonstrated that these implants reliably evoked auditory neural activity over 1 month in vivo. Evaluation in human cadaveric models confirmed compatibility after insertion using an endoscopic-assisted craniotomy surgery, ease of array positioning, and robustness and reliability of the soft electrodes. This neurotechnology offers an opportunity to treat deafness in patients who are not candidates for the cochlear implant, and the design and manufacturing principles are broadly applicable to implantable soft bioelectronics throughout the central and peripheral nervous system.

Effect of anesthesia on evoked auditory responses in pediatric auditory brainstem implant surgery.

Electrically evoked auditory brainstem responses (EABR) guide placement of the multichannel auditory brainstem implant (ABI) array during surgery. EABRs are also recorded under anesthesia in nontumor pediatric ABI recipients prior to device activation to confirm placement and guide device programming. We examine the influence of anesthesia on evoked response morphology in pediatric ABI users by comparing intraoperative with postoperative EABR recordings. Retrospective review. Seven children underwent ABI surgery by way of retrosigmoid craniotomy. General anesthesia included inhaled sevoflurane induction and propofol maintenance during which EABRs were recorded to confirm accurate positioning of the ABI. A mean of 7.7 ± 2.8 weeks following surgery, the ABI was activated under general anesthesia or sedation (dexmedetomidine) and EABR recordings were made. A qualitative analysis of intraoperative and postoperative waveform morphology was performed. Seven subjects (mean age 20.6 months) underwent nine ABI surgeries (seven primary, two revisions) and nine activations. EABRs were observed in eight of nine postoperative recordings. In three cases, intraoperative EABRs during general anesthesia were similar to postoperative EABRs with sedation. In one case, sevoflurane and propofol were used for intra- and postoperative recordings, and waveforms were also similar. In four cases, amplitude and latency changes were observed for intraoperative versus postoperative EABRs. Similarity of EABR morphology in the anesthetized versus sedated condition suggests that anesthesia does not have a large effect on far-field evoked potentials. Changes in EABR waveform morphology observed postoperatively may be influenced by other factors such as movements of the surface array. 4 Laryngoscope, 130:507-513, 2020.

Auditory brainstem stimulation with a conformable microfabricated array elicits responses with tonotopically organized components

Auditory brainstem implants (ABIs) restore hearing to deaf individuals not eligible for cochlear implants. Speech comprehension in ABI users is generally poor compared to that of cochlear implant users, and side effects are common. The poor performance may result from activating broad areas and multiple neuronal populations of the cochlear nucleus, however detailed studies of the responses to surface stimulation of the cochlear nucleus are lacking. A conformable electrode array was microfabricated to fit on the rat's dorsal cochlear nucleus (DCN). It hosts 20 small electrodes (each 100 μm diam.). The array was tested by recording evoked potentials and neural activity along the tonotopic axis of the inferior colliculus (IC). Almost all bipolar electrode pairs elicited responses, in some cases with an even, or relatively constant, pattern of thresholds and supra-threshold measures along the long axis of the array. This pattern suggests that conformable arrays can provide relatively constant excitation along the surface of the DCN and thus might decrease the ABI side effects caused by spread of high current to adjacent structures. We also examined tonotopic patterns of the IC responses. Compared to sound-evoked responses, electrically-evoked response mappings had less tonotopic organization and were broader in width. They became more tonotopic when the evoked activity common to all electrodes and the late phase of response were subtracted out, perhaps because the remaining activity is from tonotopically organized principal cells of the DCN. Responses became less tonotopic when inter-electrode distance was increased from 400 μm to 800 μm but were relatively unaffected by changing to monopolar stimulation. The results illustrate the challenges of using a surface array to present tonotopic cues and improve speech comprehension in humans who use the ABI.

Auditory Brainstem Implant Array Position Varies Widely Among Adult and Pediatric Patients and Is Associated With Perception.

The auditory brainstem implant (ABI) provides sound awareness to patients who are ineligible for cochlear implantation. Auditory performance varies widely among similar ABI cohorts. We hypothesize that differences in electrode array position contribute to this variance. Herein, we classify ABI array position based on postoperative imaging and investigate the relationship between position and perception. Retrospective review of pediatric and adult ABI users with postoperative computed tomography. To standardize views across subjects, true axial reformatted series of scans were created using the McRae line. Using multiplanar reconstructions, basion and electrode array tip coordinates and array angles from vertical were measured. From a lateral view, array angles (V) were classified into types I to IV, and from posterior view, array angles (T) were classified into types A to D. Array position was further categorized by measuring distance vertical from basion (D1) and lateral from midline (D2). Differences between array classifications were compared with audiometric thresholds, number of active electrodes, and pitch ranking. Pediatric (n = 4, 2 with revisions) and adult (n = 7) ABI subjects were included in this study. Subjects had a wide variety of ABI array angles, but most were aimed superiorly and posteriorly (type II, n = 7) from lateral view and upright or medially tilted from posterior view (type A, n = 6). Mean pediatric distances were 8 to 42% smaller than adults for D1 and D2. In subjects with perceptual data, electrical thresholds and the number of active electrodes differed among classification types. In this first study to classify ABI electrode array orientation, array position varied widely. This variability may explain differences in auditory performance.

Tinnitus Suppression After Auditory Brainstem Implantation in Patients With Neurofibromatosis Type-2.

To evaluate whether an auditory brainstem implant (ABI) can impact levels of tinnitus in neurofibromatosis type-2 (NF2) patients who have undergone translabyrinthine craniotomy for vestibular schwannoma (VS) removal and to evaluate the burden of tinnitus in these patients. A retrospective case series and patient survey. Tertiary neurotologic referral center. NF2 patients who underwent translabyrinthine removal of VS and ABI placement between 1994 and 2015. A survey, retrospective review and two validated tinnitus handicap questionnaires (tinnitus handicap inventory [THI] and tinnitus visual analogue scale [VAS]) were used to characterize the degree of tinnitus in NF2 patients and whether an ABI can alter tinnitus levels. Survey results, THI and VAS scores. One hundred twelve ABI users were contacted and 43 patients (38.3)% responded to our survey. Tinnitus was reported in 83.7% of patients. The THI score for responders was 17.8 ± 20.5 standard deviation (SD). For survey participants, the ABI reduced tinnitus levels (mean VAS: Off = 3.5; On 1-h = 2.1; p = 0.048). For patients who subjectively reported that the ABI reduced tinnitus loudness, tinnitus levels were immediately reduced on ABI activation and after 1 hour of use (mean VAS: Off = 4.8; On = 2.4; On 1-h = 1.8; p < 0.01). Suppression did not continue after the device was turned off. Audiological performance with the ABI did not correlate with tinnitus suppression. NF2 patients who have undergone removal of VS have a significant tinnitus handicap and benefit from tinnitus suppression through utilization of an ABI possibly through masking or electrical stimulation of the auditory brainstem.

Advances in Optogenetic-based Auditory Implants

Advances in Optogenetic-based Auditory Implants

Pediatric Auditory Brainstem Implant Surgery: A New Option for Auditory Habilitation in Congenital Deafness?

The auditory brainstem implant (ABI) is a neuroprosthetic device that provides sound sensations to individuals with profound hearing loss who are not candidates for a cochlear implant (CI) because of anatomic constraints. Herein we describe the ABI for family physicians. PubMed was searched to identify articles relevant to the ABI, as well as articles that contain outcomes data for pediatric patients (age <18 years) who have undergone ABI surgery. The ABI was originally developed for patients with neurofibromatosis type 2 (NF2) who become deaf from bilateral vestibular schwannomas. Over the past decade, indications for an ABI have expanded to adult patients without tumors (without NF2) who cannot receive a CI and children with no cochlea or cochlear nerve. Outcomes among NF2 ABI users are modest compared to cochlear implant patients, but recent studies from Europe suggest that some non-tumor adult and pediatric ABI users achieve speech perception. The ABI is a reasonable surgical option for children with profound hearing loss due to severe cochlear or cochlear nerve deformities. Continued prospective data collection from several clinical trials in the U.S. will provide greater understanding on long term outcomes that focus on speech intelligibility.

Auditory brainstem implant in postlingual postmeningitic patients.

The aim of this study was to evaluate outcomes of postlingual postmeningitic patients who received an auditory brainstem implant (ABI). Retrospective analysis was performed on postlingual postmeningitic patients with bilateral profound sensorineural hearing loss who underwent ABI between the years 2007 and 2014 METHODS: All patients were postlingually deaf due to cochlear ossification as a consequence of bacterial meningitis. The patients received a MED-EL or Neurelec ABI. All patients were operated on at different hospitals by the same primary surgeon. The patients were tested using Ling 5 sound detection, sound field implant thresholds between 250 Hz and 6 kHz, and 6 to 12 choice closed-set word and sentence tests. Nine patients with postmeningitic cochlear ossification received an ABI. Five of nine ABI users (55.5%) wear their audio processors (AP) most of the time. Four (44.5%) with no perceivable benefit have become nonusers. Three of the five consistent ABI users reported good benefit. The other two ABI users who do wear their APs do not respond to sound in daily living but reported benefits such as "feeling sound" in a good way. In this study, five of nine patients (55.5%) with bilateral ossified cochlea had some degree of benefit from their ABI. An ABI may be useful in hearing restoration in postlingual patients with bilateral ossified cochlea due to meningitis. However, poor results may be related to side effects, which may necessitate deactivation of electrodes, long duration of auditory deprivation, or impairments in the auditory neural structures as a result of meningitis. 4. Laryngoscope, 126:1889-1892, 2016.

Recent Rehabilitation Experience with Pediatric ABI Users.

The aim of this study is to describe the rehabilitative outcomes of pediatric auditory brainstem implant (ABI) users in the Department of Otolaryngology in the Hacettepe University. It was a retrospective study, and all patients' files were reviewed. The data was collected from 41 children who were fitted with ABI between 2005 and 2013. Inclusion criteria for children in our study are profound, congenital bilateral sensory-neural hearing loss with anomalies (such as cochlear, labyrinthine, and cochlear nerve aplasia) and more than one year of auditory experience with ABI. Post-meningitis patients and neurofibromatosis type 2 (NF2) patients were excluded. Auditory perception was evaluated using the Meaningful Auditory Integration Scale (MAIS), Functioning after Pediatric Cochlear Implantation (FAPCI) instrument, Categories of Auditory Performance (CAP), and Children's Auditory Perception Skills Test in Turkish (CIAT). Speech intelligibility was categorized with speech intelligibility rating (SIR), and language development was assessed using the Test of Early Language Development-Third Edition (TELD-3) and Manchester Spoken Language Development Scale (MSLD). All patients gained basic audiological functions and were able to recognize and discriminate sounds by the third month of ABI surgery. According to the duration of ABI use and learning skills, patients revealed development from word identification to sentence recognition level in a wide spectrum. Preliminary results indicate that all children have gained basic auditory perception skills. On the other hand, language and speech development data were varying among children. Additional handicaps seemed to slow down progression. Secondary improvement was seen at psychosocial areas with respect to behavioral and social adjustment as well as eagerness to start communication.

Systematic Review of Nontumor Pediatric Auditory Brainstem Implant Outcomes.

The auditory brainstem implant (ABI) was initially developed for patients with deafness as a result of neurofibromatosis type 2. ABI indications have recently extended to children with congenital deafness who are not cochlear implant candidates. Few multi-institutional outcome data exist. Herein, we aim to provide a systematic review of outcomes following implantation of the ABI in pediatric patients with nontumor diagnosis, with a focus on audiometric outcomes. PubMed, Embase, and Cochrane. A systematic review of literature was performed using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) recommendations. Variables assessed included age at implantation, diagnosis, medical history, cochlear implant history, radiographic findings, ABI device implanted, surgical approach, complications, side effects, and auditory outcomes. The initial search identified 304 articles; 21 met inclusion criteria for a total of 162 children. The majority of these patients had cochlear nerve aplasia (63.6%, 103 of 162). Cerebrospinal fluid leak occurred in up to 8.5% of cases. Audiometric outcomes improved over time. After 5 years, almost 50% of patients reached Categories of Auditory Performance scores >4; however, patients with nonauditory disabilities did not demonstrate a similar increase in scores. ABI surgery is a reasonable option for the habilitation of deaf children who are not cochlear implant candidates. Although improvement in Categories of Auditory Performance scores was seen across studies, pediatric ABI users with nonauditory disabilities have inferior audiometric outcomes.

Effect of Pulse Rate and Polarity on the Sensitivity of Auditory Brainstem and Cochlear Implant Users to Electrical Stimulation.

To further understand the response of the human brainstem to electrical stimulation, a series of experiments compared the effect of pulse rate and polarity on detection thresholds between auditory brainstem implant (ABI) and cochlear implant (CI) patients. Experiment 1 showed that for 400-ms pulse trains, ABI users’ thresholds dropped by about 2 dB as pulse rate was increased from 71 to 500 pps, but only by an average of 0.6 dB as rate was increased further to 3500 pps. This latter decrease was much smaller than the 7.7-dB observed for CI users. A similar result was obtained for pulse trains with a 40-ms duration. Furthermore, experiment 2 showed that the threshold difference between 500- and 3500-pps pulse trains remained much smaller for ABI than for CI users, even for durations as short as 2 ms, indicating the effect of a fast-acting mechanism. Experiment 3 showed that ABI users’ thresholds were lower for alternating-polarity than for fixed-polarity pulse trains, and that this difference was greater at 3500 pps than at 500 pps, consistent with the effect of pulse rate on ABI users’ thresholds being influenced by charge interactions between successive biphasic pulses. Experiment 4 compared thresholds and loudness between trains of asymmetric pulses of opposite polarity, in monopolar mode, and showed that in both cases less current was needed when the anodic, rather than the cathodic, current was concentrated into a short time interval. This finding is similar to that previously observed for CI users and is consistent with ABI users being more sensitive to anodic than cathodic current. We argue that our results constrain potential explanations for the differences in the perception of electrical stimulation by CI and ABI users, and have potential implications for future ABI stimulation strategies.

Subjective outcomes of auditory brainstem implantation.

To assess the long-term subjective benefits of auditory brainstem implants (ABIs) and investigate the extent to which ABI users perceive it to be a useful device. Using the Manchester database, all 31 living patients registered as ABI users were identified and sent the ABI performance questionnaire. Data regarding daily duration of use, auditory fatigue, ability to differentiate between speech and environmental sounds, and subjective usefulness of the ABI in different listening conditions were collected. Patients were asked to rate the usefulness of the device in various settings on a scale of 1 (not useful) to 6 (very useful). The mean age at implantation was 33 years (13-73 yr), and the mean follow-up period was 6 years (1.5-15 yr). Between March 1994 and September 2009, 57 patients underwent ABI insertion. A total of 26 patients were not eligible for inclusion in the study (19 nonusers, 5 deceased, and 2 sleepers). Of the 31 eligible patients identified as ABI users, 23 returned the questionnaire, 1 was excluded as the questionnaire had been completed on his or her behalf, giving a net response rate of 71%. Mean duration of usage per day was 12.62 hours (range, 8-16 h). Seventy-one percent of the patients turned the processor off at one or more points during the day. Differentiation between speech and environment was achieved in 95%, and 70% were able to differentiate between gender and adult and pediatric voices. The ABI was perceived as most beneficial when dealing with a familiar voice in a quiet place, with a median usefulness score of 4, rising to 5 when used in conjunction with lip reading. The ABI was least useful when dealing with an unfamiliar voice in a loud place, with a mean score of 1, rising to 2 when used in conjunction with lip reading. In all environments, combining the ABI with lip reading served to increase usefulness ratings by at least 1 point. This study demonstrates that ABI users make use of their device for at least 12 hours per day on average and obtain considerable subjective benefit in speech discrimination when using the device with familiar speakers in a quiet environment. Benefit is less significant in noise and with an unfamiliar speaker. Lip reading enhances subjective benefit by at least 1 point, and lip reading training may have a role to play in maximizing subjective benefit.