Graham, Madison K.

Background/Objectives: Speech perception is measured in quiet and in the presence of background noise, such as multi-talker babble (MTB), to establish cochlear implant (CI) candidacy and measure post-operative outcomes. Testing protocols often use interrupted noise that begins just before and ends shortly after the target sentence, providing insufficient time for the noise-reduction algorithms to activate in the hearing device and provide an improved signal-to-noise ratio (SNR). Furthermore, interrupted noise does not allow the hearing-impaired user to acclimatize to the abrupt onset of noise or to focus on the target sentence, a challenge related to auditory stream segregation. The present study compares speech perception in bimodal CI users across interrupted and continuous MTB noise conditions to highlight performance differences between these two distinct listening environments. Methods: Speech perception was evaluated for two different bimodal CI groups. Group 1: This group evaluated an automatic hearing aid program across three environments: quiet, continuous MTB, and interrupted MTB. Group 2: This group evaluated two manual hearing aid programs across the same three environments (quiet, continuous, and interrupted MTB). Results: For Group 1, scores in quiet reached 88%, significantly declined in interrupted MTB (38%), but improved in continuous MTB (67%). For Group 2, no significant mean differences were found between interrupted and continuous noise across the two manual programs, though individual variations persisted. Conclusions: Based on the findings of this study, continuous noise rather than interrupted noise should be utilized for establishing CI candidacy and evaluating post-implantation speech perception.

Background/Objectives: Electrode impedance is crucial for optimizing cochlear implant (CI) stimulation and hearing outcomes. While typically stable, some patients experience unexplained impedance fluctuations. This study used electrode impedance subcomponent analysis to identify the subcomponents contributing to these impedance fluctuations. Methods: This study analyzed clinical electrode impedances and transimpedance matrix (TIM) measurements in 10 CI patients with Nucleus devices (CI422, CI522, or CI622 electrode arrays) who exhibited fluctuating or rising electrode impedances. TIM measurements used a cathodic-leading biphasic pulse (110 CLs, 75 µs/phase, 7 µs interphase interval). Electrode impedances were determined at 6, 12, 18, 24, and 75 µs, and subcomponents (access resistance [near-field/far-field] and polarization impedance [Warburg capacitance/Faraday resistance]) were calculated. Results: Both access resistance and polarization impedance changes contributed to impedance fluctuations. Large changes in near-field resistance compared to far-field resistance were associated with increased resistance to current flow closer to the surface of the electrode. The decreased double-layer capacitance and slightly increased Faraday resistance further suggested increased resistance to charge transfer at the electrode–electrolyte interface. Conclusions: Electrode impedance subcomponent analysis reveals changes in the electrochemical reaction at the electrode surface that cause fluctuating or rising CI electrode impedances.

Background/Objectives: Adult hearing-impaired patients qualifying for cochlear implants typically exhibit less than 60% sentence recognition under the best hearing aid conditions, either in quiet or noisy environments, with speech and noise presented through a single speaker. This study examines the influence of deep neural network-based (DNN-based) noise reduction on cochlear implant evaluation. Methods: Speech perception was assessed using AzBio sentences in both quiet and noisy conditions (multi-talker babble) at 5 and 10 dB signal-to-noise ratios (SNRs) through one loudspeaker. Sentence recognition scores were measured for 10 hearing-impaired patients using three hearing aid programs: calm situation, speech in noise, and spheric speech in loud noise (DNN-based noise reduction). Speech perception results were compared to bench analyses comprising the phase inversion technique, employed to predict SNR improvement, and the Hearing-Aid Speech Perception Index (HASPI v2), utilized to predict speech intelligibility. Results: The spheric speech in loud noise program improved speech perception by 20 to 32% points as compared to the calm situation program. Thus, DNN-based noise reduction can improve speech perception in noisy environments, potentially reducing the need for cochlear implants in some cases. The phase inversion method showed a 4–5 dB SNR improvement for the DNN-based noise reduction program compared to the other two programs. HASPI v2 predicted slightly better speech intelligibility than was measured in this study. Conclusions: DNN-based noise reduction might make it difficult for some patients with significant residual hearing to qualify for cochlear implantation, potentially delaying its adoption or eliminating the need for it entirely.

Objectives A small number of cochlear implant (CI) users experience facial nerve stimulation (FNS), which can manifest as facial twitching. In some patients, this can be resolved by adjusting the electrical stimulation parameters. However, for others, facial stimulation can significantly impair CI outcomes or even prevent its use. The exact mechanisms underlying FNS are unclear and may vary among patients. Design Transimpedance measurements were used to assess lateral and longitudinal spread of current within 15 cochlea of nucleus CI recipients with FNS (13 unilateral recipients and 1 bilateral recipient). We compared the transimpedance measurements with programming parameters from clinical visits and pre- and postoperative temporal bone computed tomography (CT) scans to identify factors that may contribute to FNS in each CI ear. Results In nine ears, transimpedance curves showed inflection, which suggests a localized current sink within the cochlea. This indicates a low-impedance pathway through which current exits the cochlea and stimulates the labyrinthine segment of the facial nerve canal. Electrodes near this current sink were disabled or underfit to minimize facial stimulation. In the other seven ears, current flow peaked toward the basal end of the cochlea, suggesting that current exits through the round window or other structures near the basal end of the cochlea, stimulating the tympanic segment of the facial nerve. Conclusions Objective transimpedance measurements can be used to elucidate the mechanisms of FNS and to develop strategies for optimizing electrical stimulation parameters and speech coding to minimize or eliminate FNS in a small subset of CI users.

Intraoperative electrocochleography (ECOG) is performed using a single low-frequency acoustic stimulus (e.g., 500 Hz) to monitor cochlear microphonics (CM) during cochlear implant (CI) electrode insertion. A decrease in CM amplitude is commonly associated with cochlear trauma and is used to guide electrode placement. However, advancement of the recording electrode beyond the sites of CM generation can also lead to a decrease in CM amplitude and is sometimes interpreted as cochlear trauma, resulting in unnecessary electrode manipulation and increased risk of cochlear trauma during CI electrode placement. In the present study, multi-frequency ECOG was used to monitor CM during CI electrode placement. The intraoperative CM tracings were compared with electrode scan measurements, where CM was measured for each of the intracochlear electrodes. Comparison between the peak CM amplitude measured during electrode placement and electrode scan measurements was used to differentiate between different mechanisms for decrease in CM amplitude during CI electrode insertion. Analysis of the data shows that both multi-frequency electrocochleography and electrode scan could potentially be used to differentiate between different mechanisms for decreasing CM amplitude and providing appropriate feedback to the surgeon during CI electrode placement.

Objective: The Dizziness Handicap Inventory (DHI) is a 25-item self-report quantifying dizziness-related physical and emotional symptoms and restrictions in daily activities. DHI scores do not correlate with severity of structural vestibular deficits; thus, high DHI scores may reflect other causes of morbidity. This study investigated the relationship between total DHI scores and the presence of structural, functional, and psychiatric disorders in tertiary neurotology patients. Study Design: Retrospective. Setting: Tertiary center. Patients: Eighty-five patients who underwent multidisciplinary neurotologic evaluations. Intervention: Diagnostic. Main Outcome Measure(s): Active illnesses identified by a multidisciplinary neurotology team were abstracted from medical records, cataloged as structural, functional, or psychiatric disorders, and used to group patients into diagnostic categories: structural (structural disorders only), functional (functional disorders with/without structural disorders), and psychiatric (psychiatric disorders with/without other conditions). DHI scores were compared across diagnostic categories. Sensitivities and specificities of DHI scores for identifying structural versus functional or psychiatric disorders were calculated. Results: Mean DHI scores differed significantly by diagnostic category (structural 35 ± 18, functional 64 ± 15, and psychiatric 65 ± 19), before and after adjusting for age and sex ( p < 0.001, Hedges’ g>1.62 for structural versus functional and psychiatric categories). DHI≤30 (mild handicap) had specificity = 0.98 for structural disorders alone, whereas DHI>60 (severe handicap) had specificity = 0.88 for functional or psychiatric disorders. Conclusions: In this tertiary cohort, categories of illnesses had large effects on total DHI scores. Patients with scores ≤30 were likely to have structural disorders alone, whereas those with scores >60 were likely to have functional or psychiatric disorders, with or without coexisting structural conditions.