Establishing the presence of cochlear implant related artifact during sound-field recording of the auditory steady state response: A comparison between normal hearing adults, cochlear implant recipients, and a cochlear implanted human cadaver

The Auditory Steady State Response (ASSR) is an objective technique permitting dichotic, frequency-specific hearing threshold estimation. Electrical ASSR (eASSR) has the potential for auditory assessment in cochlear implant (CI) users through direct CI electrode stimulation. However, sound-field ASSR (sASSR) provides a more natural listening environment for CI users. Electrophysiological recordings could be affected by CI related artifact. The present study investigated the possibility of CI-artifact during sASSR recording in 10 CI subjects at 0.5, 1, 2 and 4 kHz. Results were compared with 15 NH controls. We investigated the mean threshold differences between the sASSR thresholds and the behavioral thresholds for each group at the four frequencies. Correlation between the sASSR thresholds and behavioral thresholds were computed. There were significant differences between the NH and CI groups across the four frequencies indicating the possibility of a CI-related artifact. In order to confirm the presence of the artifact, we recorded the sASSR in a cochlear-implanted human cadaver, six hours post-mortem. This pilot investigation which, is possibly the first sASSR in an implanted human cadaver, confirms the presence of a continuous artifact that “mimics” a true physiological response. Implications and methods to minimize artifacts to potentially increase sASSR utility will be discussed.