Common ground impedance as a biomarker for post operative hearing loss and dizziness in cochlear implant recipients

Hearing loss after cochlear implantation can occur immediately after surgery, or up to 5 years after implantation. Spikes in common ground impedance, i.e., increases in electrode resistivity of greater than 4 kOs, have been associated with a loss of residual hearing and the development of post-operative dizziness in cochlear implant recipients. In this study, we will observe impedances across the electrode array, and associated any spikes observed with medical events. Impedance measurements are routinely recorded by cochlear implant audiologists during patient visits to a clinic, therefore these observations are made immediately after implantation, then at 1, 2, 4, and 8 weeks post-implantation, and every 3-6 months thereafter for a total duration of up to 5 years. Medical events will be recorded by the cochlear implant clinic medical staff.