Confirmation of speech audibility of adult cochlear implantees by aided cortical auditory evoked potentials

Abstract

The Cortical Auditory Evoked Potential (CAEP) procedure is a useful way of estimating behavioral thresholds without participants’ active cooperation. It is becoming more commonly used in hearing aid fitting evaluation, especially for infants as they are too young to give reliable responses during evaluation. Speech stimuli can be used in CAEP assessment to better reflect listener performance when hearing speech. A commercially available system, HEARLab (Frye Electronics, Tigard OR), recently has been developed to detect aided CAEPs elicited by speech stimuli and the system analyzes CAEPs automatically. Aided CAEPs analyzed by HEARLab are also helpful in cochlear implant (CI) evaluation. However, there are very few studies on this aspect, probably due to electrical artifacts elicited by CI devices. This study aimed at determining the average P1 latency of CI subjects. Also, it compared the aided cortical assessment (ACA) results from the HEARLab system with behavioral speech detection test results in CI patients. Special CAEP recording electrodes were used to reduce the CI artifacts and test results were compared with those obtained with the original electrodes. Test outcomes for two brands of CI device (Cochlear and Advanced Bionics) were also compared. Twenty adult cochlear implantees were assessed by ACA with the two types of electrodes and by speech detection test. Test results showed that the average P1 latencies of the CI users were within the normative range of the general, non-CI population. On the other hand, the percentage of matches for positive results between ACA and behavioural speech detection test results was low and the number of CAEPs recorded without artifacts was also small with both types of electrodes. It was found that more CAEPs could be recorded without artifacts with Cochlear CI devices regardless of the type of electrodes used. However, the artifact amplitudes recorded with Cochlear CI devices were larger than those produced by Advanced Bionics devices.