Audiometric Profiles Across a Clinical Population of Children With Hyperacusis.

PURPOSE: Hyperacusis (sound sensitivity) is well documented among adults, but little is known about hyperacusis in children. Here, we assess relationships among the presence of hyperacusis, audiometric profiles, and nonauditory factors in a pediatric clinical population. METHOD: A retrospective review of clinical records from 329 children, ages 2-17 years, was performed to assess the prevalence of hyperacusis and correlations among hearing status, behavioral or communication concerns, and the presence of hyperacusis. RESULTS: In 329 study participants, 18% reported hyperacusis (58% male and 42% female). No significant sex or age differences were found. Hyperacusis was more likely to occur alongside normal hearing or with unilateral hearing loss relative to bilateral hearing loss. Among children with hyperacusis, there was a high prevalence of audiovestibular problems, mental health concerns, speech and language delays, difficulty in school, and behavioral problems. Tinnitus was also found to be comorbid with hyperacusis, but the comorbidity was less than that reported in adults. CONCLUSIONS: This study identified common hearing profiles and critical comorbidities in a large clinical cohort of children with hyperacusis. These results demonstrate the urgent need for standardized multidisciplinary assessment and treatment protocols for pediatric hyperacusis.

Cochlear-implant simulated spectral degradation attenuates emotional responses to environmental sounds.

OBJECTIVE: Cochlear implants (CI) provide users with a spectrally degraded acoustic signal that could impact their auditory emotional experiences. This study evaluated the effects of CI-simulated spectral degradation on emotional valence and arousal elicited by environmental sounds. DESIGN: Thirty emotionally evocative sounds were filtered through a noise-band vocoder. Participants rated the perceived valence and arousal elicited by each of the full-spectrum and vocoded stimuli. These ratings were compared across acoustic conditions (full-spectrum, vocoded) and as a function of stimulus type (unpleasant, neutral, pleasant). STUDY SAMPLE: Twenty-five young adults (age 19 to 34 years) with normal hearing. RESULTS: Emotional responses were less extreme for spectrally degraded (i.e., vocoded) sounds than for full-spectrum sounds. Specifically, spectrally degraded stimuli were perceived as more negative and less arousing than full-spectrum stimuli. CONCLUSION: By meticulously replicating CI spectral degradation while controlling for variables that are confounded within CI users, these findings indicate that CI spectral degradation can compress the range of sound-induced emotion independent of hearing loss and other idiosyncratic device- or person-level variables. Future work will characterize emotional reactions to sound in CI users via objective, psychoacoustic, and subjective measures.

Clinical phenotype and management of sound-induced pain: Insights from adults with pain hyperacusis.

Pain hyperacusis, also known as noxacusis, causes physical pain in response to everyday sounds that do not bother most people. How sound causes excruciating pain that can last for weeks or months in otherwise healthy individuals is not well understood, resulting in a lack of effective treatments. To address this gap, we identified the most salient physical and psychosocial consequences of debilitating sound-induced pain and reviewed the interventions that sufferers have sought for pain relief to gain insights into the underlying mechanisms of the condition. Adults (n = 32) with pain hyperacusis attended a virtual focus group to describe their sound-induced pain. They completed three surveys to identify common symptoms and themes that defined their condition and to describe their use of pharmaceutical and non-pharmaceutical therapies for pain relief. All participants endorsed negative effects of pain hyperacusis on psychosocial and physical function. Most reported sound-induced burning (80.77%), stabbing (76.92%), throbbing (73.08%), and pinching (53.85%) that occurs either in the ear or elsewhere in the body (i.e., referred pain). Participants reported using numerous pharmaceutical and non-pharmaceutical interventions to alleviate their pain with varying degrees of pain relief. Benzodiazepines and nerve blockers emerged as the most effective analgesic options while non-pharmaceutical therapies were largely ineffective. Symptoms of pain hyperacusis and therapeutic approaches are largely consistent with peripheral mechanistic theories of pain hyperacusis (e.g., trigeminal nerve involvement). An interdisciplinary approach to clinical studies and the development of animal models is needed to identify, validate, and treat the pathological mechanisms of pain hyperacusis.

The human pupil and face encode sound affect and provide objective signatures of tinnitus and auditory hypersensitivity disorders.

Sound is jointly processed along acoustic and emotional dimensions. These dimensions can become distorted and entangled in persons with sensory disorders, producing a spectrum of loudness hypersensitivity, phantom percepts, and - in some cases - debilitating sound aversion. Here, we looked for objective signatures of disordered hearing (DH) in the human face. Pupil dilations and micro facial movement amplitudes scaled with sound valence in neurotypical listeners but not DH participants with chronic tinnitus (phantom ringing) and sound sensitivity. In DH participants, emotionally evocative sounds elicited abnormally large pupil dilations but blunted and invariant facial reactions that jointly provided an accurate prediction of individual tinnitus and hyperacusis questionnaire handicap scores. By contrast, EEG measures of central auditory gain identified steeper neural response growth functions but no association with symptom severity. These findings highlight dysregulated affective sound processing in persons with bothersome tinnitus and sound sensitivity disorders and introduce approaches for their objective measurement.

Hyperacusis Diagnosis and Management in the United States: Clinical Audiology Practice Patterns.

PURPOSE: Hyperacusis often leads to debilitating psychosocial consequences, but there is no standard protocol for its diagnosis and management in the United States. In this study, we surveyed U.S. clinical audiologists to understand their education and clinical practices surrounding the evaluation and treatment of hyperacusis. METHOD: An online survey was distributed to clinical audiologists across the United States. Survey responses were quantified using descriptive statistics and inductive content analysis. RESULTS: Hyperacusis definitions and clinical practice patterns varied widely across the 102 respondents. Respondents cited a lack of education and training as the primary barrier to effective audiological diagnosis and management of hyperacusis, with most respondents reporting ≤ 5 hr of hyperacusis education. Other primary barriers to effective audiological management of hyperacusis included time constraints, reimbursement, poor sensitivity and specificity of available diagnostic tools, and poor efficacy of available treatments and management strategies. Most respondents (82.5%) agreed that audiologists are the primary professionals who are responsible for implementing hyperacusis interventions. However, 63.3% of respondents reported that their clinic does not have a hyperacusis management protocol, and 80.0% routinely recommend treatment that is outside their scope of practice to implement (cognitive behavioral therapy). CONCLUSIONS: Clinical audiologists in the United States do not receive uniform education on hyperacusis, and they report multiple barriers to its evidence-based diagnosis and management. Effective hyperacusis management necessitates a multidisciplinary approach. The information obtained via this survey will pave the way toward the refinement of interprofessional education programs and the development of systematic, evidence-based clinical protocols for hyperacusis. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.24431188.

Asymmetric hearing thresholds are associated with hyperacusis in a large clinical population.

Hyperacusis is a debilitating auditory condition whose characterization is largely qualitative and is typically based on small participant cohorts. Here, we characterize the hearing and demographic profiles of adults who reported hyperacusis upon audiological evaluation at a large medical center. Audiometric data from 626 adults (age 18-80 years) with documented hyperacusis were retrospectively extracted from medical records and compared to an age- and sex-matched reference group of patients from the same clinic who did not report hyperacusis. Patients with hyperacusis had lower (i.e., better) high-frequency hearing thresholds (2000-8000 Hz), but significantly larger interaural threshold asymmetries (250-8000 Hz) relative to the reference group. The probability of reporting hyperacusis was highest for normal, asymmetric, and notched audiometric configurations. Many patients reported unilateral hyperacusis symptoms, a history of noise exposure, and co-morbid tinnitus. The high prevalence of both overt and subclinical hearing asymmetries in the hyperacusis population suggests a central compensatory mechanism that is dominated by input from an intact or minimally damaged ear, and which may lead to perceptual hypersensitivity by overshooting baseline neural activity levels.

Programming Levels and Speech Perception in Pediatric Cochlear Implant Recipients With Enlarged Vestibular Aqueduct or GJB2 Mutation.

OBJECTIVE: To determine the relationship between hearing loss etiology, cochlear implant (CI) programming levels, and speech perception performance in a large clinical cohort of pediatric CI recipients. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary care hospitals. PATIENTS: A total of 136 pediatric CI recipients (218 ears) were included in this study. All patients had diagnoses of either enlarged vestibular aqueduct (EVA) or GJB2 (Connexin-26) mutation confirmed via radiographic data and/or genetic reports. All patients received audiologic care at either Boston Children's Hospital or Massachusetts Eye and Ear in Boston, MA, between the years 1999 and 2020. MAIN OUTCOME MEASURES: Electrode impedances and programming levels for each active electrode and speech perception scores were evaluated as a function of etiology (EVA or GJB2 mutation). RESULTS: Children with EVA had significantly higher impedances and programming levels (thresholds and upper stimulation levels) than the children with GJB2 mutation. Speech perception scores did not differ as a function of etiology in this sample; rather, they were positively correlated with duration of CI experience (time since implantation). CONCLUSIONS: Differences in electrode impedances and CI programming levels suggest that the electrode-neuron interface varies systematically as a function of hearing loss etiology in pediatric CI recipients with EVA and those with GJB2 mutation. Time with the CI was a better predictor of speech perception scores than etiology, suggesting that children can adapt to CI stimulation with experience.

Automatic identification of tinnitus malingering based on overt and covert behavioral responses during psychoacoustic testing.

Tinnitus, or ringing in the ears, is a prevalent condition that imposes a substantial health and financial burden on the patient and to society. The diagnosis of tinnitus, like pain, relies on patient self-report, which can complicate the distinction between actual and fraudulent claims. Here, we combined tablet-based self-directed hearing assessments with neural network classifiers to automatically differentiate participants with tinnitus (N = 24) from a malingering cohort, who were instructed to feign an imagined tinnitus percept (N = 28). We identified clear differences between the groups, both in their overt reporting of tinnitus features, but also covert differences in their fingertip movement trajectories on the tablet surface as they performed the reporting assay. Using only 10 min of data, we achieved 81% accuracy classifying patients and malingerers (ROC AUC = 0.88) with leave-one-out cross validation. Quantitative, automated measurements of tinnitus salience could improve clinical outcome assays and more accurately determine tinnitus incidence.

Clinical and investigational tools for monitoring noise-induced hyperacusis.

Hyperacusis is a recognized perceptual consequence of acoustic overexposure that can lead to debilitating psychosocial effects. Despite the profound impact of hyperacusis on quality of life, clinicians and researchers lack objective biomarkers and standardized protocols for its assessment. Outcomes of conventional audiologic tests are highly variable in the hyperacusis population and do not adequately capture the multifaceted nature of the condition on an individual level. This presents challenges for the differential diagnosis of hyperacusis, its clinical surveillance, and evaluation of new treatment options. Multiple behavioral and objective assays are emerging as contenders for inclusion in hyperacusis assessment protocols but most still await rigorous validation. There remains a pressing need to develop tools to quantify common nonauditory symptoms, including annoyance, fear, and pain. This review describes the current literature on clinical and investigational tools that have been used to diagnose and monitor hyperacusis, as well as those that hold promise for inclusion in future trials.

Estimated cochlear neural degeneration is associated with loudness hypersensitivity in individuals with normal audiograms.

In animal models, cochlear neural degeneration (CND) is associated with excess central gain and hyperacusis, but a compelling link between reduced cochlear neural inputs and heightened loudness perception in humans remains elusive. The present study examined whether greater estimated cochlear neural degeneration (eCND) in human participants with normal hearing thresholds is associated with heightened loudness perception and sound aversion. Results demonstrated that loudness perception was heightened in ears with greater eCND and in subjects who self-report loudness aversion via a hyperacusis questionnaire. These findings suggest that CND may be a potential trigger for loudness hypersensitivity.

Single-Channel Focused Thresholds Relate to Vowel Identification in Pediatric and Adult Cochlear Implant Listeners.

Speech recognition outcomes are highly variable among pediatric and adult cochlear implant (CI) listeners. Although there is some evidence that the quality of the electrode-neuron interface (ENI) contributes to this large variability in auditory perception, its relationship with speech outcomes is not well understood. Single-channel auditory detection thresholds measured in response to focused electrical fields (i.e., focused thresholds) are sensitive to properties of ENI quality, including electrode-neuron distance, intracochlear resistance, and neural health. In the present study, focused thresholds and speech perception abilities were assessed in 15 children and 21 adult CI listeners. Focused thresholds were measured for all active electrodes using a fast sweep procedure. Speech perception performance was evaluated by assessing listeners' ability to identify vowels presented in /h-vowel-d/ context. Consistent with prior literature, focused thresholds were lower for children than for adults, but vowel identification did not differ significantly across age groups. Higher across-array average focused thresholds, which may indicate a relatively poor ENI quality, were associated with poorer vowel identification scores in both children and adults. Adult CI listeners with longer durations of deafness had higher focused thresholds. Findings from this study demonstrate that poor-quality ENIs may contribute to reduced speech outcomes for pediatric and adult CI listeners. Estimates of ENI quality (e.g., focused thresholds) may assist in developing customized programming interventions that serve to improve the transmission of spectral cues that are important in vowel identification.

Spectral Resolution Development in Children With Normal Hearing and With Cochlear Implants: A Review of Behavioral Studies.

PURPOSE: This review article provides a theoretical overview of the development of spectral resolution in children with normal hearing (cNH) and in those who use cochlear implants (CIs), with an emphasis on methodological considerations. The aim was to identify key directions for future research on spectral resolution development in children with CIs. METHOD: A comprehensive literature review was conducted to summarize and synthesize previously published behavioral research on spectral resolution development in normal and impaired auditory systems. CONCLUSIONS: In cNH, performance on spectral resolution tasks continues to improve through the teenage years and is likely driven by gradual maturation of across-channel intensity resolution. A small but growing body of evidence from children with CIs suggests a more complex relationship between spectral resolution development, patient demographics, and the quality of the CI electrode-neuron interface. Future research should aim to distinguish between the effects of patient-specific variables and the underlying physiology on spectral resolution abilities in children of all ages who are hard of hearing and use auditory prostheses.

The Relationship Between Impedance, Programming and Word Recognition in a Large Clinical Dataset of Cochlear Implant Recipients.

Cochlear implant programming typically involves measuring electrode impedance, selecting a speech processing strategy and fitting the dynamic range of electrical stimulation. This study retrospectively analyzed a clinical dataset of adult cochlear implant recipients to understand how these variables relate to speech recognition. Data from 425 implanted post-lingually deafened ears with Advanced Bionics devices were analyzed. A linear mixed-effects model was used to infer how impedance, programming and patient factors were associated with monosyllabic word recognition scores measured in quiet. Additional analyses were conducted on subsets of data to examine the role of speech processing strategy on scores, and the time taken for the scores of unilaterally implanted patients to plateau. Variation in basal impedance was negatively associated with word score, suggesting importance in evaluating the profile of impedance. While there were small, negative bivariate correlations between programming level metrics and word scores, these relationships were not clearly supported by the model that accounted for other factors. Age at implantation was negatively associated with word score, and duration of implant experience was positively associated with word score, which could help to inform candidature and guide expectations. Electrode array type was also associated with word score. Word scores measured with traditional continuous interleaved sampling and current steering speech processing strategies were similar. The word scores of unilaterally implanted patients largely plateaued within 6-months of activation. However, there was individual variation which was not related to initially measured impedance and programming levels.

Recovery from forward masking in cochlear implant listeners: Effects of age and the electrode-neuron interface.

Older adults exhibit deficits in auditory temporal processing relative to younger listeners. These age-related temporal processing difficulties may be further exacerbated in older adults with cochlear implant (CIs) when CI electrodes poorly interface with their target auditory neurons. The aim of this study was to evaluate the potential interaction between chronological age and the estimated quality of the electrode-neuron interface (ENI) on psychophysical forward masking recovery, a measure that reflects single-channel temporal processing abilities. Fourteen CI listeners (age 15 to 88 years) with Advanced Bionics devices participated. Forward masking recovery was assessed on two channels in each ear (i.e., the channels with the lowest and highest signal detection thresholds). Results indicated that the rate of forward masking recovery declined with advancing age, and that the effect of age was more pronounced on channels estimated to interface poorly with the auditory nerve. These findings indicate that the quality of the ENI can influence the time course of forward masking recovery for older CI listeners. Channel-to-channel variability in the ENI likely interacts with central temporal processing deficits secondary to auditory aging, warranting further study of programming and rehabilitative approaches tailored to older listeners.

Audiometric Predictors of Bothersome Tinnitus in a Large Clinical Cohort of Adults With Sensorineural Hearing Loss.

OBJECTIVE: To identify demographic and audiometric predictors of bothersome tinnitus within a large clinical cohort. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary care hospital. PATIENTS: 51,989 English-speaking patients between 18 and 80 years of age that received initial audiometric evaluations at the Massachusetts Eye and Ear Infirmary between the years 2000 and 2016. MAIN OUTCOME MEASURES: Patients were categorized according to whether or not tinnitus was the primary reason for their visit. The likelihood of tinnitus as a primary complaint (TPC) was evaluated as a function of age, sex, and audiometric configuration. Patient-reported tinnitus percepts were qualitatively assessed in relation to audiometric configuration. RESULTS: Approximately 20% of adults who presented for an initial hearing evaluation reported TPC. The prevalence of TPC increased with advancing age until approximately 50 to 54 years, and then declined thereafter. In general, men were significantly more likely to report TPC than women. TPC was statistically associated with specific audiogram configurations. In particular, TPC was most prevalent for notched and steeply sloping hearing losses, but was relatively uncommon in adults with flat losses. Patients with frequency-restricted threshold shifts often reported tonal tinnitus percepts, while patients with asymmetric configurations tended to report broadband percepts. CONCLUSIONS: The probability of seeking audiological evaluation for bothersome tinnitus is highest for males, middle-aged patients, and those with notched or high-frequency hearing losses. These findings support the theory that tinnitus arises from sharp discontinuities in peripheral afferent innervation and cochlear amplification, which may induce topographically restricted changes in the central auditory pathway.

Electrophysiological Estimates of the Electrode-Neuron Interface Differ Between Younger and Older Listeners With Cochlear Implants.

OBJECTIVES: The primary objective of this study was to quantify differences in evoked potential correlates of spiral ganglion neuron (SGN) density between younger and older individuals with cochlear implants (CIs) using the electrically evoked compound action potential (ECAP). In human temporal bone studies and in animal models, SGN density is the lowest in older subjects and in those who experienced long durations of deafness during life. SGN density also varies as a function of age at implantation and hearing loss etiology. Taken together, it is likely that younger listeners who were deafened and implanted during childhood have denser populations of SGNs than older individuals who were deafened and implanted later in life. In animals, ECAP amplitudes, amplitude growth function (AGF) slopes, and their sensitivity to stimulus interphase gap (IPG) are predictive of SGN density. The authors hypothesized that younger listeners who were deafened and implanted as children would demonstrate larger ECAP amplitudes, steeper AGF slopes, and greater IPG sensitivity than older, adult-deafened and implanted listeners. DESIGN: Data were obtained from 22 implanted ears (18 individuals). Thirteen ears (9 individuals) were deafened and implanted as children (child-implanted group), and nine ears (9 individuals) were deafened and implanted as adults (adult-implanted group). The groups differed significantly on a number of demographic variables that are implicitly related to SGN density: (1) chronological age; (2) age at implantation; and (3) duration of preimplantation hearing loss. ECAP amplitudes, AGF linear slopes, and thresholds were assessed on a subset of electrodes in each ear in response to two IPGs (7 and 30 µsec). Speech recognition was assessed using a medial vowel identification task. RESULTS: Compared with the adult-implanted listeners, individuals in the child-implanted group demonstrated larger changes in ECAP amplitude when the IPG of the stimulus was increased from 7 to 30 µsec (i.e., greater IPG sensitivity). On average, child-implanted participants also had larger ECAP amplitudes and steeper AGF linear slopes than the adult-implanted participants, irrespective of IPG. IPG sensitivity for AGF linear slope and ECAP threshold did not differ between age groups. Vowel recognition performance was not correlated with any of the ECAP measures assessed in this study. CONCLUSIONS: The results of this study support the theory that young CI listeners who were deafened and implanted during childhood may have denser neural populations than older listeners who were deafened and implanted as adults. Potential between-group differences in SGN integrity emphasize a need to investigate optimized CI programming parameters for younger and older listeners.

Auditory Detection Thresholds and Cochlear Resistivity Differ Between Pediatric Cochlear Implant Listeners With Enlarged Vestibular Aqueduct and Those With Connexin-26 Mutations.

Purpose The goal of this study was to evaluate differences in the electrode-neuron interface as a function of hearing loss etiology in pediatric cochlear implant (CI) listeners with enlarged vestibular aqueduct (EVA) syndrome and in those with autosomal recessive connexin-26 mutations (DFNB1). Method Fifteen implanted ears (9 participants, 5 ears with EVA, 10 ears with DFNB1) were assessed. Single-channel auditory detection thresholds were measured using broad and spatially focused electrode configurations (steered quadrupolar; focusing coefficients = 0 and 0.9). Cochlear resistivity estimates were obtained via electrode impedances and electrical field imaging. Between-group differences were evaluated using linear mixed-effects models. Results Children with EVA had significantly higher auditory detection thresholds than children with DFNB1, irrespective of electrode configuration. Between-group differences in thresholds were more pronounced on apical electrodes than on basal electrodes. In the apex, electrode impedances and electrical field imaging values were higher for children with EVA than for those with DFNB1. Conclusions The electrode-neuron interface differs between pediatric CI listeners with DFNB1 and those with EVA. It is possible that optimal clinical interventions may depend, in part, on hearing loss etiology. Future investigations with large samples should investigate individualized CI programming strategies for listeners with EVA and DFNB1.

Identifying Cochlear Implant Channels With Relatively Poor Electrode-Neuron Interfaces Using the Electrically Evoked Compound Action Potential.

OBJECTIVES: The primary objective of this study was to quantify local (within ear) and global (between ear) variation in the cochlear implant (CI) electrode-neuron interface (ENI) using the electrically evoked compound action potential (ECAP). We tested the hypothesis that, within an ear, ECAP measures can be used to identify channels with presumed good and poor ENIs, which may be influenced by a combination of spiral ganglion neuron (SGN) density, electrode position, and cochlear resistivity. We also hypothesized that ECAP responses would reflect age-related differences in the global quality of the ENI between younger and older listeners who theoretically differ in SGN density. DESIGN: Data were obtained from 18 implanted ears (13 individuals) with Advanced Bionics HiRes 90K devices. Six participants (8 ears) were adolescents or young adults (age range: 14-32 years), and 7 participants (10 ears) were older adults (age range: 54-88 years). In each ear, single-channel auditory detection thresholds were measured on channels 2 through 15 in response to a spatially focused electrode configuration (steered quadrupolar; focusing coefficient = 0.9). ECAP amplitudes, amplitude growth function (AGF) slopes, and thresholds were assessed on a subset of channels in each ear in response to three interphase gaps (0, 7, and 30 µs). ECAP peak amplitudes were assessed on all channels between 2 and 15. AGFs and ECAP thresholds were measured on the two nonadjacent channels with the lowest and highest focused behavioral thresholds in each ear. ECAP responses were compared across low- and high-threshold channels and between younger and older CI listeners. RESULTS: Channels that were estimated to interface poorly with the auditory nerve (i.e., high-focused-threshold channels) had steeper ECAP AGF slopes, smaller dynamic ranges, and higher ECAP thresholds than channels with low focused thresholds. Younger listeners had steeper ECAP AGF slopes and larger ECAP peak amplitudes than older listeners. Moreover, younger listeners showed greater interphase gap sensitivity for ECAP amplitude than older listeners. CONCLUSIONS: ECAP responses may be used to quantify both local (within ear) and global (between ear) variation in the quality of the ENI. Results of this study support future investigation into the use of ECAP responses in site-selection CI programming strategies. The present results also support a growing body of evidence suggesting that adolescents and young adults with CIs may have denser populations of functional SGNs relative to older adults. Potential differences in global SGN integrity between younger and older listeners warrant investigation of optimal CI programming interventions based on their divergent hearing histories.

Polarity Sensitivity in Pediatric and Adult Cochlear Implant Listeners.

Modeling data suggest that sensitivity to the polarity of an electrical stimulus may reflect the integrity of the peripheral processes of the spiral ganglion neurons. Specifically, better sensitivity to anodic (positive) current than to cathodic (negative) current could indicate peripheral process degeneration or demyelination. The goal of this study was to characterize polarity sensitivity in pediatric and adult cochlear implant listeners (41 ears). Relationships between polarity sensitivity at threshold and (a) polarity sensitivity at suprathreshold levels, (b) age-group, (c) preimplantation duration of deafness, and (d) phoneme perception were determined. Polarity sensitivity at threshold was defined as the difference in single-channel behavioral thresholds measured in response to each of two triphasic pulses, where the central high-amplitude phase was either cathodic or anodic. Lower thresholds in response to anodic than to cathodic pulses may suggest peripheral process degeneration. On the majority of electrodes tested, threshold and suprathreshold sensitivity was lower for anodic than for cathodic stimulation; however, dynamic range was often larger for cathodic than for anodic stimulation. Polarity sensitivity did not differ between child- and adult-implanted listeners. Adults with long preimplantation durations of deafness tended to have better sensitivity to anodic pulses on channels that were estimated to interface poorly with the auditory nerve; this was not observed in the child-implanted group. Across subjects, duration of deafness predicted phoneme perception performance. The results of this study suggest that subject- and electrode-dependent differences in polarity sensitivity may assist in developing customized cochlear implant programming interventions for child- and adult-implanted listeners.

Evaluating Psychophysical Polarity Sensitivity as an Indirect Estimate of Neural Status in Cochlear Implant Listeners.

The physiological integrity of spiral ganglion neurons is presumed to influence cochlear implant (CI) outcomes, but it is difficult to measure neural health in CI listeners. Modeling data suggest that, when peripheral processes have degenerated, anodic stimulation may be a more effective neural stimulus than cathodic stimulation. The primary goal of the present study was to evaluate the emerging theory that polarity sensitivity reflects neural health in CI listeners. An ideal in vivo estimate of neural integrity should vary independently of other factors known to influence the CI electrode-neuron interface, such as electrode position and tissue impedances. Thus, the present analyses quantified the relationships between polarity sensitivity and (1) electrode position estimated via computed tomography imaging, (2) intracochlear resistance estimated via electrical field imaging, and (3) focused (steered quadrupolar) behavioral thresholds, which are believed to reflect a combination of local neural health, electrode position, and intracochlear resistance. Eleven adults with Advanced Bionics devices participated. To estimate polarity sensitivity, electrode-specific behavioral thresholds in response to monopolar, triphasic pulses where the central high-amplitude phase was either anodic (CAC) or cathodic (ACA) were measured. The polarity effect was defined as the difference in threshold response to the ACA compared to the CAC stimulus. Results indicated that the polarity effect was not related to electrode-to-modiolus distance, electrode scalar location, or intracochlear resistance. Large, positive polarity effects, which may indicate SGN degeneration, were associated with relatively high focused behavioral thresholds. The polarity effect explained a significant portion of the variation in focused thresholds, even after controlling for electrode position and intracochlear resistance. Overall, these results provide support for the theory that the polarity effect may reflect neural integrity in CI listeners. Evidence from this study supports further investigation into the use of polarity sensitivity for optimizing individual CI programming parameters.