Related Experiment Video
Updated: Oct 5, 2025
Electrically Evoked Stapedius Reflex Measurements in Cochlear Implantation and Its Application in the Postoperative Fitting Process
Published on: June 21, 2024
Toward a method of achieving balanced stimulation of bilateral auditory nerves: Evidence from children receiving
P Tsai1, N Wisener1, B C Papsin2
1Archie's Cochlear Implant Laboratory, Rm 6D08, The Hospital for Sick Children, 555 University Ave, Toronto, ON M5G 1X8, Canada.
Insights
Mismatched cochlear implants in children require higher current levels for balanced hearing and can lead to asymmetric auditory nerve stimulation and impaired speech perception. Careful programming is essential to mitigate these risks.
Area of Science:
- Audiology
- Neurosurgery
- Biomedical Engineering
Background:
- Bilateral cochlear implants (CIs) aim to provide balanced auditory input.
- Mismatched electrode arrays may lead to asymmetric stimulation and hearing outcomes.
Purpose of the Study:
- To investigate if mismatched bilateral cochlear implants compromise balanced auditory nerve stimulation.
- To determine if mismatched CIs establish asymmetric hearing in children.
Main Methods:
- Compared electrophysiological measures (ECAPs) and behavioral outcomes in children with matched vs. mismatched CI arrays.
- Assessed current levels for balanced ECAP amplitudes and speech perception scores.
Main Results:
- Mismatched arrays required higher current levels for balanced stimulation.
- Speech perception was significantly more asymmetric in children with mismatched CIs.
- Device programming parameters poorly predicted balanced ECAP amplitudes in mismatched cases.
Conclusions:
- Higher current needs for anti-modiolar arrays in mismatched CIs are not fully addressed by current programming.
- Using mismatched electrode arrays in pediatric bilateral cochlear implants increases the risk of asymmetric hearing.
Objectives:
To identify whether mismatched bilateral cochlear implants compromise balanced stimulation of the two auditory nerves and establish asymmetric hearing in children.
Methods:
Behavioural and electrophysiological measures were completed in 47 children receiving bilateral CIs in the same surgery (simultaneously): 27 children received a peri‑modiolar N24RE array in one ear and a 422 anti-modiolar array in the other (experimental group) and 20 children received 2 peri‑modiolar arrays (control group). Differences in current levels between the two devices were measured by electrically evoked compound action potentials (ECAPs) at the time of surgery. These data were compared with minimum and maximum comfortably loud levels programmed in each speech processor (T-levels, C-levels, respectively) after 12 months of bilateral CI use. Asymmetries in functional hearing between arrays were measured in open set speech perception testing between 3 to 5 years of CI use.
Results:
Higher current levels were required from the anti-modiolar than peri‑modiolar array to evoke balanced interaural ECAP amplitudes (mismatched group: mean ± SD difference: -9.9 ± 22.6; matched group: -0.8 ± 26.5). This difference was larger in the experimental group than control group (t = -2.51; p = 0.016) and remained constant with increases in current level from ECAP threshold to maximum amplitudes (dynamic range) in many but not all children in both groups. T and C-levels were poorly predictive of levels needed to evoke balanced ECAP amplitudes in children with mismatched devices (F(1, 312) = 1.3, p = 0.263). Speech perception scores were more asymmetric between ears in children using bilateral mismatched arrays (mean ± SD: 73.8 ± 16.4 at the peri‑modiolar array; 57.7 ± 26.4 at the anti-modiolar array), compared to children with bilateral matched arrays (right ear: 78.0 ± 10.4; left ear: 74.9 ± 13.5).
Conclusion:
Higher current level requirements at the anti-modiolar array compared to the peri‑modiolar array in children with bilateral mismatched CIs are not fully accounted for in device programming. Mismatched electrodes in children receiving bilateral cochlear implants increases the risk of asymmetric hearing.
