Objetives:
Previous studies suggest that stimulation through triphasic pulses in cochlear implant users diminish undesired secondary effects when present.  Triphasic pulses consist of 2 negative phases of the same duration and one positive phase, all of the same amplitude, resulting in an overall charged balanced pulse which restore the neural membrane to its resting potential faster than biphasic pulses do. In the present study, we aim to elicit stapedius reflexes with triphasic pulses, and compared them with  the standard biphasic ones.
Materials and Method:
14 patients with ages between 7 and 58 years participated in the study. These patients met the condition of having reflexes in at least 3 of the 5 electrodes stimulated, in order to be able to create a reflex based map.  All of them were experienced users (>1 year). Stapedius reflex thresholds (ESRT) were elicited through biphasic and triphasic pulses with MAESTRO clinical software in a random order. The stimulus consisted in 300 milliseconds bursts delivered via the audio processor of each patient. The responses were registered with a Sentiero Desktop using a 226 Hz probe tone.  Success rate from both types of pulses considering stimulation site, difference at threshold level, amplitudes and speech perception in quiet and noise were compared. 
Results:
According to on site visual recognition, reflexes were present in 86.67% and in 87,84% for biphasic and triphasic pulses respectively. Average charge level needed to obtain the reflexes across electrodes were of 25.02 qu (biphasic) and 31.16 qu (triphasic), with variations of 13% to 30% depending on the electrode site with a converging trend towards basal electrodes. Open-set speech perception evaluated in a subset of 10 subjects for the two ESRT based maps showed better responses for map created with biphasic pulses for speech in quiet and mixed results for ESRT map created with triphasic for speech in noise.
Conclusion:
Recording ESRT by means of triphasic pulses has shown to be feasible in a clinical setting. This gives the chance to extend the application of this objective measure to those patients that show secondary effects from biphasic stimulation.



COMPARISON BETWEEN ELECTRICALLY EVOKED STAPEDIUS REFLEXES WITH BIPHASIC AND TRIPHASIC PULSES

It is with great pleasure and enthusiasm, that on behalf of the Cochlear Implant centers of the Radboud UMC in Nijmegen and Erasmus MC Sophia Children’s Hospital in Rotterdam to invite you to attend the 16th European Symposium on Pediatric Cochlear Implantation to Rotterdam, the Netherlands in 2023.

Yours sincerely, on behalf of the CI Centers at Radboud UMC and Erasmus MC,