Boyd (2010) queried whether a simple cochlear implant (CI) map based on common default parameters would perform adequately for children recently implanted, when there is only very limited objective data on which to base the standard custom CI fitting. Thus, "flat maps," in which the upper stimulation levels were set equally across the electrode array, were evaluated in established adult CI users.
Boyd notes that, indeed, there are many settings beyond loudness that can be programmed into the CI map (such as output compression function, electrode stimulation order, bandpass filter boundaries, etc.). However, in general, these are not adjusted unless anatomic anomalies are present that potentially alter the neural target.
Fitting data from 90 adults (over age 16 years) associated with five CI centers in the United Kingdom was gathered. Ranges and means of MCL levels and which electrodes were "de-activated" were evaluated (deactivation of a particular electrode is usually done to prevent non-auditory stimulation of the facial nerve, and is sometimes done to reduce unclear or annoying auditory percepts).
Of note, the most basal electrode (E11) was deactivated in approximately half of all cases. The second most deactivated electrodes were the most apical (E1) and E11. The remaining electrodes (E2 through E10) were active approximately 94 percent of the time. In general, adult CI performance was best with their customized map.
The tolerance to map imbalance in young children remains unknown. However, the data suggests that if one were to provide a simplified MAP with respect to electrode activation, electrodes between E2 and E10 should be used in the majority of the cases with normal anatomy. With regard to tolerance levels, Boyd notes that children often use "less than perfectly balanced" maps, as children generally do not have the cognitive ability to fully participate in setting their ideal customized map. Therefore, if necessary, simplified CI mapping protocols makes sense if and when needed. However, Boyd concludes that it is important to acquire and use accurate electrode-specific measures with children as soon as possible.
For More Information, References, and Recommendations
Boyd PJ. (2010) Evaluation of Simplified Programs Using the MED-EL C40+ Cochlear Implant. International Journal of Audiology 49(7):527–534.