Effectiveness of Phantom Stimulation in Shifting the Pitch Percept in Cochlear Implant Users.

OBJECTIVES: Phantom electrode stimulation was developed for cochlear implant (CI) systems to provide a lower pitch percept by stimulating more apical regions of the cochlea, without inserting the electrode array deeper into the cochlea. Phantom stimulation involves simultaneously stimulating a primary and a compensating electrode with opposite polarity, thereby shifting the electrical field toward the apex and eliciting a lower pitch percept. The current study compared the effect sizes (in shifts of place of excitation) of multiple phantom configurations by matching the perceived pitch with phantom stimulation to that perceived with monopolar stimulation. Additionally, the effects of electrode location, type of electrode array, and stimulus level on the perceived pitch were investigated. DESIGN: Fifteen adult advanced bionics CI users participated in this study, which included four experiments to eventually measure the shifts in place of excitation with five different phantom configurations. The proportions of current delivered to the compensating electrode, expressed as σ, were 0.5, 0.6, 0.7, and 0.8 for the symmetrical biphasic pulses (SBC0.5, SBC0.6, SBC0.7, and SBC0.8) and 0.75 for the pseudomonophasic pulse shape (PSA0.75). A pitch discrimination experiment was first completed to determine which basal and apical electrode contacts should be used for the subsequent experiments. An extensive loudness balancing experiment followed where both the threshold level (T-level) and most comfortable level (M-level) were determined to enable testing at multiple levels of the dynamic range. A pitch matching experiment was then performed to estimate the shift in place of excitation at the chosen electrode contacts. These rough shifts were then used in the subsequent experiment, where the shifts in place of excitation were determined more accurately. RESULTS: Reliable data were obtained from 20 electrode contacts. The average shifts were 0.39, 0.53, 0.64, 0.76, and 0.53 electrode contacts toward the apex for SBC0.5, SBC0.6, SBC0.7, SBC0.8, and PSA0.75, respectively. When only the best configurations per electrode contact were included, the average shift in place of excitation was 0.92 electrode contacts (range: 0.25 to 2.0). While PSA0.75 leads to equal results as the SBC configurations in the apex, it did not result in a significant shift at the base. The shift in place of excitation was significantly larger at the apex and with lateral wall electrode contacts. The stimulus level did not affect the shift. CONCLUSIONS: Phantom stimulation results in significant shifts in place of excitation, especially at the apical part of the electrode array. The phantom configuration that leads to the largest shift in place of excitation differs between subjects. Therefore, the settings of the phantom electrode should be individualized so that the phantom stimulation is optimized for each CI user. The real added value to the sound quality needs to be established in a take-home trial.

Dynamic Current Focusing: A Novel Approach to Loudness Coding in Cochlear Implants.

OBJECTIVES: In an attempt to improve spectral resolution and speech intelligibility, several current focusing methods have been proposed to increase spatial selectivity by decreasing intracochlear current spread. For example, tripolar stimulation administers current to a central electrode and uses the two flanking electrodes as the return pathway, creating a narrower intracochlear electrical field and hence increases spectral resolution when compared with monopolar (MP) stimulation. However, more current is required, and in some patients, specifically the ones with high electrode impedances, full loudness growth cannot be supported because of compliance limits. The present study describes and analyses a new loudness encoding approach that uses tripolar stimulation near threshold and gradually broadens the excitation (by decreasing compensation coefficient σ) to increase loudness without the need to increase overall current. It is hypothesized that this dynamic current focusing (DCF) strategy increases spatial selectivity, especially at lower loudness levels, while maintaining maximum selectivity at higher loudness levels, without reaching compliance limits. DESIGN: Eleven adult cochlear implant recipients with postlingual hearing loss, with at least 9 months of experience with their HiRes90K implant, were selected to participate in this study. Baseline performance regarding speech intelligibility in noise (Dutch matrix sentence test), spectral ripple discrimination at 45 and 65 dB, and temporal modulation detection thresholds were assessed using their own clinical program, fitted on a Harmony processor. Subsequently, the DCF strategy was fitted on a research Harmony processor. Threshold levels were determined with σ = 0.8, which means 80% of current is returned to the flanking electrodes and the remaining 20% to the extracochlear ground electrode. Instead of increasing overall pulse magnitude, σ was decreased to determine most comfortable loudness. After 2 to 3 hr of adaptation to the research strategy, the same psychophysical measures were taken. RESULTS: At 45 dB, average spectral ripple scores improved significantly from 2.4 ripples per octave with their clinical program to 3.74 ripples per octave with the DCF strategy (p = 0.016). Eight out of 11 participants had an improved spectral resolution at 65 dB. Nevertheless, no significant difference between DCF and MP was observed at higher presentation levels. Both speech-in-noise and temporal modulation detection thresholds were equal for MP and DCF strategies. Subjectively, 2 participants preferred the DCF strategy over their own clinical program, 2 preferred their own strategy, while the majority of the participants had no preference. Battery life was decreased and ranged from 1.5 to 4 hr. CONCLUSIONS: The DCF strategy gives better spectral resolution, at lower loudness levels, but equal performance on speech tests. These outcomes warrant for a longer adaptation period to study long-term outcomes and evaluate if the outcomes in the ripple tests transfer to the speech scores. Further research, for example, with respect to fitting rules and reduction of power consumption, is necessary to make the DCF strategy suitable for routine clinical application.

Channel discrimination along all contacts of the cochlear implant electrode array and its relation to speech perception.

OBJECTIVE: To test the channel discrimination of cochlear implant (CI) users along all contacts of the electrode array and assess whether this is related to speech perception. DESIGN: CI recipients were tested with a custom-made channel discrimination test. They were asked to distinguish a target stimulus from two reference stimuli in a three-alternative forced choice (3AFC) task. The target stimulus was evoked using current steering, with current steering coefficients (α) of 1, 0.5 and 0.25. The test provided a discrimination score (Dα) for each electrode contact along the array. STUDY SAMPLE: Thirty adults implanted with a CI from Advanced Bionics. RESULTS: Large variations in Dα scores were observed, both across the electrode array and between subjects. Statistical analysis revealed a significant channel-to-channel variability in Dα score (p < 0.01). Further, there was a significant relationship between subjects' Dα scores and their speech perception in quiet (p < 0.001). CONCLUSIONS: The large variations in Dα score emphasise the importance of testing pitch discrimination across the complete electrode array. The relationship between Dα score and speech perception indicates that pitch discrimination might be a contributing factor to the performance of individual implant users.

Dynamic current focusing for loudness encoding in cochlear implants: a take-home trial.

Objective: This study aimed to evaluate a more energy-efficient dynamic current focussing (DCF) speech-processing strategy after long-term listening experience. In DCF, tripolar stimulation is used near the threshold and loudness is controlled by the compensation coefficient σ. A recent acute pilot study showed improved spectral-temporally modulated ripple test (SMRT) scores at low loudness levels, but battery life was reduced to 1.5-4 hours. Design: Within-subject comparisons were made for the clinical versus. DCF strategy after 5 weeks of at-home usage. Speech intelligibility in noise, spectral ripple discrimination, temporal modulation detection, loudness growth, and subjective ratings were assessed. Study sample: Twenty HiRes90K (Advanced Bionics, Valencia, USA) cochlear implant (CI) users. Results: Average battery life was 9 hours with the newly implemented DCF compared to 13.4 hours with the clinical strategy. Compared with measurements made at the beginning of the study, SMRT-scores and speech intelligibility in noise were significantly improved with DCF. However, both measures suffered from unexpected learning effects over time. The improvement disappeared and speech intelligibility in noise declined significantly relative to the final control measurement with the clinical strategy. Conclusion: Most CI users can adapt to the DCF strategy in a take-home setting. Although DCF has the potential to improve performance on the SMRT test, learning effects complicate the interpretation of the current results.

Learning Effects in Psychophysical Tests of Spectral and Temporal Resolution.

OBJECTIVES: Psychophysical tests of spectral and temporal resolution, such as the spectral-ripple discrimination task and the temporal modulation detection test, are valuable tools for the evaluation of cochlear implant performance. Both tests correlate with speech intelligibility and are reported to show no instantaneous learning effect. However, some of our previous trials have suggested that there is a learning effect over time. The aim of this study was to investigate the test-retest reliability of the two tests when measured over time. DESIGN: Ten adult cochlear implant recipients, experienced with the HiResolution speech coding strategy, participated in this study. Spectral ripple discrimination and temporal modulation detection ability with the HiResolution strategy were assessed both before and after participation in a previous trial that evaluated two research speech coding strategies after 2 weeks of home-usage. Each test was repeated six times on each test day. RESULTS: No improvement was observed for same-day testing. However, comparison of the mean spectral ripple discrimination scores before and after participation in the take-home trial showed improvement from 3.4 to 4.8 ripples per octave (p < 0.001). The mean temporal modulation detection thresholds improved from -15.2 to -17.4 dB (p = 0.035). CONCLUSIONS: There was a clear learning effect over time in the spectral and temporal resolution tasks, but not during same-day testing. Learning effects may stem from perceptual learning, task learning, or a combination of those two factors. These results highlight the importance of a proper research design for evaluation of novel speech coding strategies, where the baseline measurement is repeated at the end of the trial to avoid false-positive results as a consequence of learning effects.

SDHAF2-Linked Metastatic Paraganglioma: A Case Report with Implications for Counseling and Follow-Up of Pathogenic SDHAF2 Variant Carriers.

Head and neck paragangliomas are slow growing and highly vascular neuroendocrine tumors. It is currently assumed that SDHAF2 variants exclusively cause benign and often multicentric head and neck paragangliomas. Here, we present a patient diagnosed with multiple SDHAF2-linked head and neck paragangliomas who in addition developed paraganglioma metastases to the lung and spine and a primary or metastatic paraganglioma in the head of the pancreas. During the course of the disease, a range of management strategies were deployed for the different head and neck tumors, including total resections, partial resections, and active surveillance. After identification of the paraganglioma metastases, the patient was treated with lanreotide after which the disease remained stable during the 27 months of follow-up.

Take-Home Trial Comparing Fast Fourier Transformation-Based and Filter Bank-Based Cochlear Implant Speech Coding Strategies.

Previous studies have demonstrated no improved or deteriorated speech intelligibility with the HiResolution Fidelity 120™ speech coding strategy (HiResF120) over the original HiRes strategy. Improved spectral and deteriorated temporal sensitivities have been shown, making it plausible that the beneficial effect in the spectral domain was offset by the worsened temporal sensitivity. We hypothesize that the implementation of fast Fourier transform (FFT) processing, instead of the traditionally used bandpass filters, explains the reduction of temporal sensitivity. In this study, spectral ripple discrimination, temporal modulation detection, and speech intelligibility in noise were assessed in a two-week take-home trial with 3 speech coding strategies: one with conventional bandpass filters (HiRes), one with FFT-based filters (HiRes FFT), and one with FFT-based filters and current steering (HiRes Optima). One participant dropped out due to discomfort with both research programs. The 10 remaining participants performed equally well on all tasks with all three speech coding strategies, implying that FFT processing does not change the ability of CI recipients to discriminate spectral or temporal information or speech understanding.

[Eosinophilic otitis media]. / Eosinofiele otitis media.

BACKGROUND: Eosinophilic otitis media (EOM) is a rare middle ear disease that may closely resemble therapy-resistant otitis media with effusion (OME). The diagnosis is made if eosinophil-rich fluid is present with two or more of the following minor criteria: (a) history of nasal polyps or, (b) bronchial asthma, with (c) viscous fluid in the middle-ear, or (d) conventional otitis media treatment has no effect. CASE DESCRIPTION: A 70-year-old male with a history of the ASA triad (bronchial asthma, nasal/ethmoidal polyposis and aspirin intolerance) presented with progressive mixed hearing loss. Otoscopy showed bilateral otitis media with effusion (OME). Conventional treatment of this had no effect. Myringotomy resulted in the evacuation of highly viscous middle-ear effusion containing abundant eosinophils. After treatment with oral corticosteroids his symptoms improved considerably. Following later optimisation of his asthma treatment, corticosteroid treatment was stopped and his hearing remained stable. CONCLUSION: The adequate recognition and treatment of EOM will result in the prevention of permanent hearing loss.