Rhythm increases perceptual tolerance when measuring electrically evoked compound action potentials in cochlear implant recipients

In cochlear implant (CI) recipients, measurement of the electrically evoked compound action potential (ECAP) is used in clinical routine to prove the electrode-nerve interface and to support fitting, especially in very young children. To record an ECAP amplitude growth function (AGF), electrical stimuli are presented at increasing intensities up to the maximum acceptable loudness (MAL). However, a continuously monotonically rising sound can quickly be perceived as unpleasant and thus impair the success rate of ECAP threshold determination. The present study investigates whether perceptual and objective parameters, which are involved in ECAP measurements, depend on the type of stimulus presentation. In 27 subjects with a CI (28 implants), stimuli of five different AGF patterns were presented ten times in random order at a medial electrode contact, resulting in a total of 50 AGFs per implant. One pattern (P _<i>clin</i> ) in which the stimuli increase strictly monotonically is already implemented in the clinical software (MAESTRO). The present study also employed rhythmic patterns and patterns with pauses. The behavioral threshold (THR), the maximum comfortable level (MCL), the MAL, and objective ECAP threshold were analyzed. ECAP threshold values did not change significantly when different stimulus paradigms were applied. Rhythmic AGF patterns were perceived as less unpleasant and enabled a higher MAL compared to P _<i>clin</i> . This in turn led to improved ECAP threshold determination, with the success rate rising to 86.7%, compared to 79.1% for P _<i>clin</i> .