Electrically evoked auditory cortical responses elicited from individually fitted stimulation parameters in cochlear implant users.

OBJECTIVE: To investigate electrically evoked auditory cortical responses (eACR) elicited from the stimulation of intracochlear electrodes based on individually fitted stimulation parameters in cochlear implant (CI) users. DESIGN: An eACR setup based on individual fitting parameters is proposed. A 50-ms alternating biphasic pulse train was used to stimulate apical, medial, and basal electrodes and to evoke auditory cortical potentials (N1-P2 complex). STUDY SAMPLE: The eACR setup proposed was validated with 14 adult CI users. RESULTS: Individual and grand-average eACR waveforms were obtained. The eACR amplitudes were lower in the basal than in the apical and medial regions. Earlier N1 latencies were found in CI users with lower maximum comfortable loudness levels and shorter phase duration in response to apical stimulation, while medial and basal stimulation resulted in earlier N1 latencies and larger N1-P2 amplitudes in users with longer CI experience. CONCLUSIONS: eACR could be elicited by direct intracochlear stimulation using individual fitting parameters with a success rate of 71%. The highest cortical peak-to-peak amplitudes were obtained in response to apical stimulation. Unlike the P2, the N1 component appeared to be a consistent cortical potential to determine eACR and gain knowledge of the auditory processing beyond the cochlea in CI users. HighlightseACR can be elicited through direct stimulation of intracochlear electrodes.Stimulation of apical and medial regions yielded the highest N1-P2 amplitudes.CI users with lower maximum comfortable loudness levels had shorter N1 latencies during apical stimulation.The present dataset of mainly well-performing CI users suggests better cortical processing, that is, higher amplitudes and shorter latencies of N1.The N1 potential appears a more consistent and reliable potential than the P2 to determine eACR responses in CI users.

Maximum acceptable level for the determination of ECAP and ESRT in a paediatric population.

OBJECTIVES: Two of the most used objective measures are electrically evoked action potentials (ECAPs) and electrically evoked stapedius reflex thresholds (ESRTs). Although stimuli used for these measures differ considerably, both measures are influenced by subjective loudness percept. We focus on the subjective maximum acceptable loudness (MAL) to investigate if loudness sensitivity varied along the electrode array during ECAP recordings. In addition, we explored how the MAL reached during an ECAP recording related to the postoperative ESRT. METHODS: Uni- and bilaterally implanted young CI users (n = 15, average age = 9 y, age range 3-18 y) underwent ECAP and ESR recordings using the clinical software MAESTRO (MED-EL, Innsbruck, Austria) and a commercially available immittance instrument (PATH MEDICAL GmbH, Germering, Germany). RESULTS: Loudness tolerance during ECAP recordings was lowest at the two apical-most electrode contacts (number 1 and 2). There was a moderate correlation between the MAL achieved during ECAP recordings and ESR maximum stimulation amplitudes. (r: 0.44344). CONCLUSIONS: ECAP recordings should commence at basal or medial contacts to increase the users' comfort and loudness tolerance, especially in young CI users. A higher maximum stimulation appears to increase the chance of the automatic determination of ECAP thresholds for all electrode contacts.

Comparison of automated and traditional ECAP recording approaches in clinical practice.

OBJECTIVE: The traditional method of recording electrically evoked compound action potentials (ECAPs), as implemented in the MAESTRO clinical software (standard ART), requires manual adjustments during threshold determination through a specialist. The "FineGrain" research tool (FineGrain RT) uses a continuous stimulation paradigm combined with automatic ECAP threshold determination. The aim of this study was to compare the FineGrain RT with standard ART. DESIGN: ECAPs were recorded with standard ART and the FineGrain RT in paediatric cochlear implant recipients. Different stimulation rates were used for FineGrain ECAP recordings (40, 60, and 76 Hz). STUDY SAMPLE: Thirteen children (6 - 19 years) participated in this study - nine were bilaterally and four unilaterally implanted, resulting in a total of twenty-two implanted ears. RESULTS: ECAP threshold determination success rates were similar between the two approaches (92% and 89%) and ECAP thresholds correlated well (r: 0.94, p < 2.2e-16) with average ART thresholds being lower than FineGrain RT thresholds. FineGrain stimulation with different stimulation rates did not have a significant effect on ECAP thresholds but ECAP thresholds at medial and apical contacts were lower compared to basal contacts. CONCLUSIONS: TheFineGrain research approach is a reliable replacement for standard ART in clinical practice.

Comparison of a Traditional and Novel Evoked Compound Action Potentials Recording Approach and Evoked Auditory Brainstem Responses in Pediatric Cochlear Implants Users.

OBJECTIVES: Electrically evoked compound action potentials (eCAP) recordings are widely used in functional evaluation and fitting of cochlear implants (CI) in clinics. We compared the results from two eCAP recording approaches (StandardART and FineGrain, MED-EL, Austria). The FineGrain method is more advanced than the Auditory Nerve Response Telemetry (StandardART) method in terms of the stimulation and algorithm for the eCAP threshold detection. To understand the benefits of these alterations, we compared the two methods on a larger scale in pediatric CI users alongside evoked auditory brainstem responses (eABR). MATERIALS AND METHODS: We collected the eCAP recordings obtained with both methods from a population of pediatric subjects with CI, either intra- or post-operatively. The eABR recordings were only collected post-operatively. For comparability reasons, we used the same stimulation rate and similar amplitude levels for all three approaches. RESULTS: Our results demonstrate that, although the success rates are similar, the FineGrain method outperforms traditional StandardART in terms of robustness and measurement duration. The eCAP recordings in general outperform the eABR in terms of speed. CONCLUSION: We conclude that the eCAP recordings are the method of choice for measuring the auditory neural activity, and FineGrain outperforms StandardART. From the three investigated approaches, we conclude that FineGrain performed best and should be the first-choice method in pediatric patients.