Comparison of two methods of data presentation for the electrical brainstem response in cochlear implant patients

Cochlear implants have become an acceptable method for management of the deaf patient, adult and child alike. Since the advent of implants there has been much research into objective methods for setting electrode values. The most common method is the electrical auditory brainstem response (EABR). The result of EABR threshold measurement is frequently reported as an arbitrary stimulus level set by the manufacturer. However, there has been recent discussion of whether an arbitrary stimulus level is acceptable or if the results should be reported in absolute units, either charge or current, particularly when combined data are used. This report compares two methods of data presentation for the EABR, arbitrary stimulus level and absolute units measured in nanoCoulombs (nC). Data collected from a previous study were used in this comparison. All patients were fitted with the Nucleus multi-channel device and Mini Speech Processor. The correlation between stimulus level and log charge (nC) was 0.990 with a slope of 0.987 which suggests the method of data reporting does not alter EABR results materially when using the Nucleus device.