Cochlear Implants Considerations in Programming for the Pediatric Population

Introduction:

Cochlear implants are surgically implanted devices that provide electrical stimulation to the auditory system, which is perceived within the brain as sound.

Cochlear implants (CIs) are typically programmed for each individual patient based on their auditory perceptions in response to electrical stimuli. Generally, approximately 4 weeks post-implantation, a program or "map," is created for the CI patient by setting threshold levels (T-levels; the minimal amount of electrical stimulation required for the auditory system to perceive sound) and comfort levels (M or C-levels; the upper limit of electrical stimulation judged to be most comfortable, or loud but comfortable). For maximum benefit, CI recipients are seen for regularly scheduled intervals to reprogram their cochlear implant throughout their lifetime.

On rare occasion, the implanted CI patient is unable to participate in the mapping protocol. When patient participation is not possible, objective measurements, rather than subjective preferences, are used to determine map settings. Evoked potentials and related measures can be measured and obtained using the manufacturer's provided software. The three most common objective measures of CIs include; NRI, NRT and ESRT.

NRT/NRIs measure electrically evoked compound action potentials (ECAP). Neural Response Telemetry (NRT) is available with Cochlear America's devices (see www.cochlearamericas.com/Professional/141.asp). Devices manufactured by Advanced Bionics use Neural Response Imaging (NRI) (see www.bionicear.com/professionals/library.asp). NRT/NRI studies suggest that ECAP thresholds obtained fall within the range between T and C/M levels for a majority of CI recipients tested. However individual variability does exist between patients so use of patient participation in programming is preferred [1, 2, 3]. Some studies show variability in speech perception scores when using an NRT-derived map, as compared to using a patient participation-derived map [4, 5]. However, the differences were not statistically significant which suggest that although NRT settings may not be optimal; they provide a reasonable access to speech information.

Electrical Stapedial Reflex Thresholds (ESRT) can also be very useful with all cochlear implant designs (see www.bionicear.com/printables/ESRT_hires.pdf). Post-operative ESRTs have a close correlation to mapped C/M-levels, however, this measure can be difficult to obtain on children, as the patient must remain still [6, 7, 8].

Unfortunately, objective measures cannot be obtained for all individuals. In these cases, programming parameters are sometimes set at the clinician's discretion, based on the clinician's experience, test results and knowledge.