A new objective method to estimate the charge integration efficiency in cochlear implant users.

Objective: The present study aimed to objectively assess the charge integration efficiency (CIE) of the auditory nerve using electrically-evoked stapedial reflex threshold (eSRT) measurements in paediatric cochlear implant users.

Design: The eSRT was estimated in two ways: by keeping pulse width constant while increasing pulse amplitude and vice versa. The electrical dynamic range (EDR) obtained for eSRT was measured with increasing pulse amplitude (EDR_PA) and pulse width (EDR_PW) by calculating the difference in charge units between eSRT and behavioural thresholds; further, CIE was estimated.

Study sample: Fifteen paediatric cochlear implant users.

Results: EDR_PW was 1.4 to 1.7 times larger than EDR_PA. The EDR_PW was significantly greater than the EDR_PA. A significant correlation was observed between both EDR measures. However, the CIE measure did not significantly correlate with the behavioural threshold. Further, there was no significant effect of electrode location on the CIE.

Conclusions: The CIE estimated with objective measures such as eSRT is comparable to those estimated using behavioural loudness judgments. eSRT can serve as a quick method to estimate the CIE, which can be easily implemented in the paediatric population. The CIE could be a valuable tool for differentiating electrodes with excellent and poor charge integration efficiency.