Electrophysiologic and objective monitoring of the cochlear implant during surgery: implementation, audit and outcomes.

Electrophysiologic and objective measures are reviewed with respect to their implementation as monitoring tools for cochlear implants in the operating room and their value in the management of children. The current intraoperative test protocol in Nottingham consists of back-telemetry (BT) diagnostic testing of implant function, including impedance telemetry (ImpT), integrity testing (IT), electrical stapedius reflex response (ESR), electrical auditory brainstem response (EABR) and Neural Response Telemetry (NRT). Of 427 cases of implantation in the period 1990-2003, 303 (71%) were completely normal for all components of the protocol. In the remaining cases, some results were either simply anomalous, with no direct impact on management during surgery, and some were more significant, resulting in actions such as the use of the back-up device or repositioning of the electrode array. Normal intraoperative findings provided immediate reassurance to the implant team and parents of young children that the implant was fully functioning and that electrical stimulation was activating the auditory pathways These objective measures also identified potentially challenging cases, such as those with low levels of sensitivity to electrical stimulation and susceptibility to facial nerve stimulation. An audit showed that intraoperative measures provided valuable assistance in the initial fitting of the device.