The Role of Electrophysiological Testing in Pediatric Cochlear Implantation

When cochlear implants (CIs) were first made available to children, clinicians often cautioned families and caregivers that the implant may or may not provide access to sound. This counseling was based upon uncertainty about each child’s potential to hear with the device. It often took several months of watching and waiting and adjustments to CI stimulation levels before a behavioral test confirmed sound detection. Today, a surgeon and implant team can leave the operating room knowing that the new CI functions and stimulates a response from the auditory nerve, as it is designed to do, by including an electrophysiological measure of auditory activity into the surgical procedure. Knowledge of stimulation levels obtained in the operating room may then be used at device activation to guide programming of stimulation levels needed to obtain a behavioral response. Electrophysiological measures have provided an important addition to the battery of tests used to manage children with CIs. As will be discussed here, it is best to use these tests in a battery including behavioral measures in much the same way as similar electrophysiological measures are used with behavioral tests to diagnose and characterize hearing loss. The initial electrophysiological test of auditory activity evoked by the newly implanted device in the operating room provides answers to many urgent questions: (1) Does the implant work? (2) Does the auditory system respond to the electrical pulses? and (3) What stimulation levels are required for hearing? As the child uses his/her device over time, these questions may repeatedly arise. Additional questions may also arise including: (1) Does the CI evoke unwanted effects such as non-auditory or other abnormal responses? (2) Is the auditory system developing as expected with the CI? and (3) Are bilateral CIs providing accurate binaural cues? Electrophysiological measures can help answer these questions.