Can Psychophysical Perception Really be Predicted Using Electrically-Evoked Compound Action Potentials in Adult Cochlear Implant Users?

Background: In cochlear implant (CI) recipients, the threshold of the electrically-evoked compound action potential (ECAP) has been shown to correlate both with the perceptual detection threshold and the maximum comfortable loudness level (THR and MCL respectively) used for implant programming. However, this has not allowed so far audiologists to get accurate predictions of CI fitting levels from ECAP.

Objectives: We investigated 1) which ECAP characteristics are most related to psychophysical levels (PL), and 2) how the use of different stimulation parameters for ECAP recording compared to those used in everyday life situations affects these relationships.

Methods: ECAP were collected for three electrode locations in 45 adults using CI for more than 11 months.

To assess the effect of stimulation differences on predictions accuracy, we collected THR and MCL measured using the ECAP stimulation, MCL implemented during fitting, ECAP and electrodes’ impedances.

Predictive models were computed using linear mixed models.

Results: The ECAP threshold and the stimulation site were selected as predictors for the three PL. Relative prediction errors were about 10% but were slightly lower for the measured THR and higher for the programmed MCL

Conclusion: Results confirmed that ECAP threshold is related to PL in adult CI users. Considering the stimulation site increases predictions’ accuracy.

However, prediction errors remained too high to propose safe and accurate fitting based on the sole ECAP. This lack of accuracy may partly be explained by the use of different stimulations for ECAP recording compared to those used in everyday life situations.