Examination and Comparison of Electrically Evoked Compound Action Potentials and Electrically Evoked Auditory Brainstem Response Results of Children with Cochlear Implantation without Inner Ear Anomaly

Exploring the relationship between electrophysiological measures of the electrically evoked auditory brainstem response and speech perception outcomes post-cochlear implantation

OBJECTIVES

This study examined the relationships between electrophysiological measures of the electrically evoked auditory brainstem response (EABR) with speech perception measured in quiet after cochlear implantation (CI) to identify the ability of EABR to predict postoperative CI outcomes.

METHODS

Thirty-four patients with congenital prelingual hearing loss, implanted with the same manufacturer's CI, were recruited. In each participant, the EABR was evoked at apical, middle, and basal electrode locations. The following EABR measures were analyzed: wave III and V input/output (I/O) function, latency, threshold, threshold0.5 μV and Gibson scoring. Patients' speech perception abilities were assessed using the Mandarin Speech Perception (MSP) materials presented in quiet. The Categories of Auditory Performance (CAP) and Speech Intelligibility Rating (SIR) were also used to assess CI outcomes. A regression model was developed to explore the relationship between EABR and each speech measure, to identify parameters with significant predictive ability.

RESULTS

A significantly shorter eV latency, lower eV threshold, lower eV threshold0.5 μV and steeper I/O slopes for both eV and eIII were observed when these responses were evoked at the apical electrode, compared to the middle and basal positions. Implantation age was significantly negatively correlated with bisyllables recognition rate (R2 = 0.20, p = 0.0194). The eIII slope at the apical site and the eV slope at the basal site demonstrated the highest R2 values in positive correlation with CAP, both with R2 = 0.09. Among the EABR parameters, the regression models based on MSP bisyllables recognition rate, basal eV latency, eV thresholds and threshold0.5 μV recorded at the apical and middle positions were statistically significant.

CONCLUSIONS

Our study identified an apex-to-base gradient in EABR responsiveness following prolonged CI use. The threshold and I/O slopes of EABR appear to be informative predictors of speech perception performance in CI users, especially in the low-to-middle frequency range. However, further validation is needed.

How differ eCAP types in cochlear implants users with and without inner ear malformations: amplitude growth function, spread of excitation, refractory recovery function

OBJECTIVES

Inner ear malformations (IEMs) may result in differences in outcomes of cochlear implant user. These differences could be observed in both behavioral and objective tests. eCAP is the most common used objective test in cochlear implants and have different presence rate in cochlear implant users with and without IEMs. This study aims to evaluate eCAP results from CI user with and without IEMs through different recoding methods; amplitude growth function, spreads of excitation and refractory recovery.

METHODS

There were 42 CI users (20 IEM&22 normal) above five-years old and with at least one year experience. Three different eCAP measurement was conducted at several intracochlear electrodes. Presence rate, threshold levels and amplitude were compared between groups.

RESULTS

For Amplitude growth function measurement, when the percentage of detected eCAP thresholds was analyzed between groups, there was a significant difference only for basal electrode and no significant difference for apical and middle electrodes. Similarly, the presence rate of RecF-eCAP for both groups were in a downward trend from apical to basal. However, there was no significant difference in AGF-eCAP and RecF-eCAP amplitudes between groups for the cochlea's apical, middle and basal region. Although the presence rate of SOE-eCAP was lower for IEM group, there was no significant difference in ECAP amplitudes for all maskers.

CONCLUSIONS

It could be inferred that even though the observable eCAP rate differed between these two groups when the observable eCAP was recorded, the IEM group produced eCAP with similar amplitudes to normal cochlea group.

Electric Auditory Brainstem Response Audiometry in Cochlear Implants: New Recording Paradigm

(1) Background: Cochlear implants (CIs) are widely applied to recover audition for patients with severe degrees of or total hearing loss. Electrical stimulation using the electrically evoked ABR (E-ABR) can be recorded in CI recipients through the device. This work was designed to study E-ABR recorded individually from different channels located at the apical, middle, and basal cochlear regions in comparison to their simultaneous separated or adjacent combined recordings. (2) Methods: This study included 17 children fitted with unilateral cochlear implants. All children were subjected to impedance measurement, electrical compound action potentials (ECAP), and E-ABR recording of three channels located at the apical, middle, and basal cochlear regions. This was followed by simultaneous E-ABR recording of the three "separated" channels in comparison to E-ABR recording from three adjacent channels located at the middle cochlear region. (3) Results: Similar E-ABR latencies and amplitudes were found using either individual or simultaneously separated or adjacent combined recording. However, the mean amplitude measures of E-ABR for combined adjacent channels showed a positive correlation with the applied current level. (4) Conclusions: Combined E-ABR recording from adjacent channels is a faster and more reliable technique that can be used effectively without compromising the results of the recorded E-ABR.

The effect of cochlear implant insertion technique on post-operative neural response telemetry and impedance in paediatric patients

OBJECTIVE

This study aimed to compare neural response telemetry and impedance between the round window and cochleostomy approaches for cochlear implantation.

METHODS

In this case-control study, 64 patients aged less than 3.5 years underwent cochlear implantation via the round window or cochleostomy approach. Post-operative neural response telemetry and impedance were measured.

RESULTS

The impedance measurements at electrodes 1, 11 and 22 showed no significant differences between the two groups three months after implantation (p = 0.90, p = 0.08 and p = 0.37, respectively). Similar results were observed six months after implantation (p = 0.71, p = 0.65 and p = 0.70, respectively). There was no significant difference in neural response telemetry between the two groups after three months. The neural response telemetry of electrode 1 in the cochleostomy group (171.26 ± 19.81 μV) was significantly higher in comparison with that of electrode 1 in the round window group (161.97 ± 12.71 μV) after six months (p = 0.03). The neural response telemetry values for electrodes 11 and 22 did not show any significant difference after six months (p = 0.14 and p = 0.48, respectively).

CONCLUSION

Both approaches provide equal stimulation of the cochlear nerve and impedance.

Neural recovery function of the auditory nerve in cochlear implant surgery: Comparison between different regions of the cochlea

INTRODUCTION

Cochlear implants allow measures of neural function, through Neural response telemetry (NRT) and Auditory nerve recovery function (REC). These help in programming the speech processor and understanding the auditory system. However, not many studies have evaluated and compared these in different regions of the cochlea.

OBJECTIVE

Comparing NRT and REC in different regions of the cochlea.

METHODS

Cross-sectional, descriptive and prospective. NRT and REC (through the function of T0 - absolute refractory period, A - amplitude and TAU - time constant of the relative refractory period parameters) were evaluated, in three groups according to the stimulated electrode of the cochlea: apical, medial and basal.

RESULTS

26 adult patients were evaluated, 2 bilateral, totalling 28 ears. Data analysis showed no statistically significant difference between NRT between medial and basal but showed between apical and medial and apical and basal. For T0, there was a significant difference between medial and basal; for A, there was a significant difference between apical and basal and also medial and basal; and for TAU, there was no significant difference.

CONCLUSION

There was a statistically significant difference in NRT and REC when compared between different regions of the cochlea.