Telemetry changes over time in cochlear implant patients

Objectives: This is a cross-sectional study conducted on cochlear implant recipients, to monitor changes in recorded impedance telemetry and evoked compound action potentials (ECAP) measured during surgery versus the same measures at post implant follow-up visits. An additional aim was to correlate the recorded ECAP measures with the patient's post-operative performance and to evaluate the incidence of abnormal intra-operative cochlear implant telemetry measurements and their changes at device activation. Study design: The present study comprised 44 subjects – 12 adults and 32 children of both genders – implanted at the Cochlear Implant Unit, Cairo University. ECAP thresholds and electrode impedance measures were collected intra-operatively, at initial stimulation, and at 9–12 months post initial stimulation. Measurements were compared at the three intervals and ECAP measures were correlated to the patient's post-operative performance in the form of aided sound field thresholds, speech detection and discrimination for adults and language assessment for children. Results: In the absence of electrical stimulation, there was an increase of impedance on all electrodes at the initial stimulation visit, which decreased at the 9–12 months follow-up. Open circuit findings were more prevalent than short circuits. Children had higher impedance values at post implant activation compared to adult patients. No correlation existed between ECAP thresholds and post-operative patient performance at the one-year evaluation. Conclusion: At the time of surgery, telemetry provides valuable information regarding the electrical output of the implant and the response of the auditory system to electrical stimulation; however, it is not a valuable predictor of post-operative performance.