Optimizing stimulation parameters to record electrically evoked cortical auditory potentials in cochlear implant users.

Objectives

To measure the effect of burst duration, stimulated electrode position, and stimulation level on the P1-N1-P2 electrically evoked cortical auditory potentials (eCAEPs) elicited via the direct stimulation of selected electrode contacts on a cochlear implant (CI) electrode array.

Methods

Prospective observational study of 20 adult cochlear implant users with a MED-EL CI system. eCAEPs were recorded simultaneously with the Eclipse (Interacoustics) and the Neuropack S1 MEB-9400 (Nihon Kohden) recording systems. Tone bursts with durations of 50, 100, and 150 ms were used for stimulation at the maximum comfortable loudness level (MCL) and MCL minus 50% dynamic range (DR) at selected apical, medial, and basal intracochlear electrodes.

Results

Individual P1-N1 and N1-P2 amplitudes were significantly higher at the MCL level of stimulation than at the MCL minus 50% DR. Burst length and stimulated electrode position did not affect the eCAEP responses. Residual noise was lower in the Neuropack S1 MEB-9400 system.

Conclusions

This study shows the feasibility of eCAEP recording using the MAESTRO software. The eCAEP morphology was independent of the burst duration and the stimulated electrode position. This allows a large flexibility in using direct cochlear stimulation to elicit eCAEPs.