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

Abstract

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, threshold_{0.5 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 threshold_{0.5 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 threshold_{0.5 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.

Keywords: Auditory performance; EABR (electrically evoked auditory brainstem responses); I/O slope (amplitude growth function); Speech perception; Threshold.

Fig. 1

Sample EABR waveforms evoked from the apical (electrode 1, A), middle (electrode 11, B), and basal electrodes (electrode 22, C) from subject no. 14 (A–C) with CAP/SIR 6/4 and subject no. 11 (D–F), who had poorer speech perception and production (CAP/SIR: 3/2). eIII wave III, eV wave V

Fig. 2

A visual representation of the sliding window method for calculating the maximum slope of the EABR amplitude growth function. A All data points evoked by the apical, middle, and basal electrodes were plotted in a single figure, and a gradual change of I/O slope is apparent. B–D For each electrode, the maximum slope among all windows is selected

Fig. 3

This figure illustrates a gradual increase in eV latency of the EABR, recorded from the apical to basal electrodes of the CI (a). The lower two graphs display the threshold and I/O slope values of the EABR across various electrode locations, with both threshold and AGF slope showing a gradient from the apex to the base (b, c). *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001

Fig. 4

Scatterplots showing the relationships between (a–c) CAP and EABR I/O slope, and d bisyllabic recognition rates and implantation age