Four-point Impedance Changes in the Early Post-Operative Period After Cochlear Implantation. Issue 7 (19th August 2022)

• Record Type: Journal Article
• Authors: Razmovski, Tayla; Bester, Christofer; Collins, Aaron; O'Leary, Stephen J.
• Is Part Of: Otology & neurotology. Volume 43:Issue 7(2022)
• Page Start: e730
• Page End: e737
• Publication Date: 2022-08-19
• Subjects: Biosensors -- Cochlear implant -- Fibrosis -- Impedance -- Inflammation -- Post-operative monitoring; Otology -- Periodicals; Ear -- Diseases -- Periodicals; Skull base -- Surgery -- Periodicals; 617.8005
• DOI: 10.1097/MAO.0000000000003592
• Languages: English
• ISSNs: 1531-7129

Abstract

Abstract : Objective: Monitoring four-point impedance changes after cochlear implantation with comparison to conventional impedance measurements. Four-point impedance provides information regarding the bulk biological environment surrounding the electrode array, which is not discernible with conventional impedances. Study Design: Prospective observational. Setting: Hospital. Patients: Adult cochlear implant recipients with no measurable hearing before implantation and implanted with a perimodiolar cochlear implant. Main Outcome Measure(s): Mean values for four-point and common ground impedances were calculated for all electrode contacts at intra-operative, 1 day, 1 week, 4 to 6 weeks, and 3 months post implantation. Linear mixed models were applied to the impedance data to compare between impedances and time points. Furthermore, patients were divided into groups dependent on the normalized change in four-point impedance from intra-operative to 1 day post-operative. The normalized change was then calculated for all other time points and compared across the two groups. Results: Significant increases in four-point impedance occurred 1 day and 3 months after surgery, particularly in the basal half of the array. Four-point impedance at 1 day was highly predictive of four-point impedance at 3 months. Four-point impedance at the other time points showed marginal or no increases from intra-operative. Patients with an average increase higher than 10% in four-point impedance from intra-operative to 1 day, had significantly higher values at 3 months ( p = 0.012). These patterns were not observed in common ground impedance. Conclusion: This is the first study to report increases in four-point impedance within 24 hours of cochlear implantation. The increases at 1 day and 3 months align with the natural timeline of an acute and chronic inflammatory responses.