Impedance Change as an Indicator of Cochlear Implant Failure.

OBJECTIVE: In February 2020, Advanced Bionics initiated a field action notice to remove the MS Ultra (V1) implant from circulation. In this study, we quantify a single site's incidence with device failure and examine the relationship between impedance change and declining speech perception. STUDY DESIGN: Retrospective/cohort study. SETTING: Tertiary healthcare center. PATIENTS: Forty-nine adult patients (52 devices) were implanted between October 2017 and December 2019, with the following exclusion criteria: <18 years of age, medical/surgical failures, and lack of English-language proficiency. INTERVENTIONS: Diagnostic. MAIN OUTCOME MEASURES: Postoperative speech perception (AzBio sentence test) scores at 12 months postactivation were compared with repeat testing at 6- to 12-month intervals. Degree of change in impedances from 1 month postactivation was analyzed at similar intervals. Device failures were suspected when impedance levels on three or more electrodes dropped to <3.5 kΩ and AzBio scores declined >15%. Device failures were confirmed through analyses completed by the manufacturer. RESULTS: To date, 21% (11/52) of devices have met all three criteria for a confirmed failure with an average decline in speech perception of 27.7 ± 22%. The average length of time for detection of device failure was 21.9 ± 5 months postimplantation. An additional 7 devices (13%) are currently being monitored for failure but have not yet met full criteria. There was no predictive relationship between degree of impedance change and speech perception scores. Electrodes along the entire array (channels 1-16) can be affected. CONCLUSIONS: Impedance values can be used as a reliable indicator of device malfunction, thus facilitating patient counseling and early intervention. No correlation was identified between impedance changes and speech perception scores.

Relative power of harmonics in human frequency-following responses associated with voice pitch in American and Chinese adults.

When the fundamental frequency (f0) is removed from a complex stimulus, the pitch of the f0 is still perceived by the listener. Through the use of the scalp-recorded frequency-following response, this study examined the relative contributions of thef0 and its harmonics in pitch processing by systematically manipulating the speech stimulus to remove component frequencies. 12 American and 12 Chinese adults were recruited. There were statistically significant effects of pitch strength and frequency error for the experimental-condition factor. There were significantly larger responses to the harmonics-only conditions than those obtained in the f0-only and control conditions. No statistically significant difference was observed between the two groups of participants. These findings indicate that neural responses associated with individual harmonics dominate the pitch processing in the human brainstem, irrespective of whether the listener's native language is nontonal or tonal.