Early Elevation and Normalization of Electrode Impedance in Patients With Enlarged Vestibular Aqueduct Undergoing Cochlear Implantation.

OBJECTIVE: To characterize early changes in impedance in patients undergoing cochlear implantation with and without enlarged vestibular aqueducts (EVA). METHODS: Case-control retrospective study of patients undergoing cochlear implantation with and without EVA. Impedance was measured across all channels intraoperatively and within 24 hours of surgery. All patients received the same electrode array. RESULTS: Ten patients with EVA (and matched controls were identified). The average intraoperative impedance across all electrodes was significantly higher in patients with EVA (13.1 ±â€Š1.4 kΩ) than in controls (9.6 ±â€Š2.5 kΩ, p  < 0.001). At 24-hour activation, the average impedance across all electrodes was roughly equal in both groups (6.8 ±â€Š2.7 kΩ versus 6.5 ±â€Š2.1 kΩ, p  = 0.72). CONCLUSIONS: This study is the first identify differences in intraoperative impedance between patients with and without EVA. In addition, these data demonstrate rapid normalization within 24 hours of surgery. Such findings can give a window of insight into both the intracochlear microenvironment of patients with EVA and the important early electrode-fluid-tissue interface changes that occur within hours of surgery for all patients.

Evolution of impedance values in cochlear implant patients after early switch-on.

Cochlear implantation is currently the most effective treatment modality for severe to profound sensorineural hearing loss. Over the past few years, at the Department of Otolaryngology, Cheng Hsin General Hospital (Taipei, Taiwan), cochlear implant devices have been switched on within 24 hours of their implantation. Differences in impedance evolution after early switch-on for different devices have not been previously discussed. The present study aimed to investigate the impedance evolution of one device and the factors influencing this after early activation. Results are compared to published results of other devices. A total of 16 patients who received Advanced BionicsTM devices and had early activation within 24 hours of implantation, were included in the study. Impedance telemetry was recorded intraoperatively and postoperatively at 1 day, 1 week, 2 weeks, 4 weeks and 8 weeks. A stepwise increase was observed in the impedance evolution. To the best of our knowledge, the present study is the first to investigate the impedance evolution of the different devices after early switch-on within 24 hours of implantation and its influencing factors. Further research with a longitudinal design to compare the differences in electrode impedances between patients activated early versus those activated after a few weeks will be necessary for the disclosure of the underlying mechanisms.