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Updated: Oct 25, 2026
Performing Intracochlear Electrocochleography During Cochlear Implantation
Published on: March 8, 2022
Age-dependent variation in eCAP measures across cochlear electrode locations: effects of interphase gap in cochlear
Roya Karimi Pour1, Mohammad Maarefvand1, Hesamaldin Emamdjomeh2
1Audiology Department, Rehabilitation School, Iran University of Medical Sciences, Tehran, Iran.
Purpose:
Electrophysiological measures obtained from cochlear implants provide objective information about the electrode-neuron interface (ENI). Although conventional electrically evoked compound action potential (eCAP) measures are widely used to characterize neural responsiveness, their sensitivity to age- and electrode-dependent differences remains unclear. This study investigated the effects of electrode location and interphase gap (IPG) on eCAP measures in pediatric and adult cochlear implant users.
Methods:
Twelve children (mean age: 6.1 years) and 11 adults (mean age: 32.8 years) using Cochlear™ devices with perimodiolar electrode arrays participated. Impedance, spread of excitation (SOE) width at 75% of peak amplitude, and eCAP threshold, amplitude, and amplitude growth function (AGF) slope were measured at basal, middle, and apical electrodes. eCAPs were recorded using IPGs of 7 and 30 µs. IPG effects were evaluated using complementary unified and normalized analytical approaches.
Results:
Impedance was highest at basal electrodes, whereas SOE width did not differ significantly by age group or electrode location. Conventional eCAP thresholds, amplitudes, and AGF slopes varied across the cochlear array, with regional differences in eCAP amplitude and AGF slope but few age-related differences. Increasing IPG significantly affected eCAP threshold, amplitude, and AGF slope across both analytical approaches. However, for the IPG-related effect on AGF slope, the unified analysis showed no significant interaction among IPG, group, and electrode, whereas the normalized analysis showed a larger slope effect in children than adults, without a significant higher-order interaction. Impedance was additionally associated with the IPG-related change in AGF slope.
Conclusions:
Conventional eCAP measures revealed distinct regional patterns across the cochlear array, whereas IPG manipulation consistently affected threshold, amplitude, and AGF slope, with group and electrode differences observed for selected measures. These findings suggest that IPG-sensitive eCAP measures may provide complementary information about the ENI beyond conventional eCAP measures alone, while the observed age- and region-dependent patterns and their dependence on analytical approach warrant further investigation.
