The Relationship Between Reaction Time of Electrical Stapedius Reflex and Auditory Performance in Cochlear-implanted Children

Objectives: A common concern in some cochlear-implanted children is the lack of desired progress in auditory and listening skills. Such a concern remains despite proper verbal processor programming, additional disabilities, and continuous participation in hearing rehabilitation programs. A more detailed assessment of pathways and centers of the auditory processing at the lower end of the brain stem by measuring the time of the Electrical Stapedius Reflex (ESR), and investigating its relation to auditory perception skills can provide significant information about choosing the appropriate rehabilitation method. Methods: In total, 20 unilateral cochlear-implanted children (3-7-year-olds) participated in this research. All of them were implanted for ≥2 years and participated for ≥1 year in the auditory-verbal rehabilitation program. The ESR reaction time was measured for 3 electrodes in the apex, middle, and basal areas. The Categories of Auditory Performance (CAP-II) test score was used to assess the progress of auditory skills. Then the correlation between CAP-II test score and ESR reaction time was investigated per each electrode. Results: There was a significant inverse correlation between the ESR reaction time and the CAP II test scores in the apex electrodes (r=-0.5, P<0.05). However, no such correlation was observed in the middle (r=0.34, P>0.05) and basal (r=-0.06, P>0.05) electrodes. Discussion: There was a significant correlation between the shorter reaction time of ESR in the apex electrode and the higher scores in the CAP-II test for auditory skills in children. Therefore, examining the ESR reaction time can be useful for prediction of the benefits of cochlear implantation as well as choosing a better rehabilitation approach for cochlear-implanted children.

Effect of Number of Electrodes Used to Elicit Electrical Stapedius Reflex Thresholds in Cochlear Implants

<b><i>Introduction:</i></b> When mapping cochlear implant (CI) patients with limited reporting abilities, the lowest electrical stimulus level that produces a stapedial reflex (i.e., the electrical stapedius reflex threshold [eSRT]) can be measured to estimate the upper bound of stimulation on individual or a subset of CI electrodes. However, eSRTs measured for individual electrodes or a subset of electrodes cannot be used to predict the global adjustment of electrical stimulation levels needed to achieve comfortable loudness sensations that can be readily used in a speech coding strategy. In the present study, eSRTs were measured for 1-, 4-, and 15-electrode stimulation to (1) determine changes in eSRT levels as a function of the electrode stimulation mode and (2) determine which stimulation mode eSRT levels best approximate comfortable loudness levels from patients’ clinical maps. <b><i>Methods:</i></b> eSRTs were measured with the 3 different electrical stimulation configurations in 9 CI patients and compared with behaviorally measured, comfortable loudness levels or M-levels from patients’ clinical maps. <b><i>Results:</i></b> A linear, mixed-effects, repeated-measures analysis revealed significant differences (<i>p</i> &#x3c; 0.01) between eSRTs measured as a function of the stimulation mode. No significant differences (<i>p</i> = 0.059) were measured between 15-electrode eSRTs and M-levels from patients’ clinical maps. The eSRTs measured for 1- and 4-electrode stimulation differed significantly (<i>p</i> &#x3c; 0.05) from the M-levels on the corresponding electrodes from the patients’ clinical map. <b><i>Conclusion:</i></b> eSRT profiles based on 1- or 4-electrode stimulation can be used to determine comfortable loudness level on either individual or a subset of electrodes, and 15-electrode eSRT profiles can be used to determine the upper bound of electrical stimulation that can be used in a speech coding strategy.