The Value Electrical Stapedial Reflex Thresholds (eSRTs) Cochlear Implant Mapping

One of the most significant challenges in cochlear implant programming, particularly for very young children and those with an associated pathologies, is the measurement of subjective comfort levels (= C-Subjective). Currently, to define this C-Subjective level, patients are presented with a loudness scale and must indicate whether the sound stimulus, sent via the implant, is soft, comfortable, or loud. The lower and upper stimulation levels must be determined for each electrode in order to program the implant. For many patients this can be difficult due to a lack of auditory experience and confusion between the sensation of sound intensity (weak or loud) and frequency (low or high). For these patients, the adjustment is often based on the dynamic range recommended by the manufacturer in relation to the threshold (lower stimulation level) and/or on the discomfort level (upper stimulation level). Objective measures such as ECAPs (Electric compound action potentials) are commonly used to estimate upper stimulation levels. These measurements are useful for confirming electrode function and neuronal response, and some research has shown that these measures are correlated with the upper stimulation level. However, other studies suggest that ECAPs are poor predictors of high (and low) stimulation levels and can show variability between electrodes and between subjects. A less commonly used but more objective approach to programming upper stimulation levels involves the use of the electrical stapedial reflex threshold (eSRTs) value. eSRTs are a promising measure, given the demonstrated correlation between the threshold that generates a stapedial reflex and the C-subjective level. Furthermore, eSRTs can be recorded in the majority of patients, and can typically be evoked at a comfortable stimulation level i.e. inferior to the uncomfortable level. The patient settings are known as the MAP, where the upper and lower levels of stimulation are defined. MAPs using eSRTs to set upper stimulation levels (C-eSRT) have been shown equal or better speech recognition results compared to behavior-based MAPs (intensity scale). Additionally, eSRT-based MAPs have been shown to result in equal sound intensity across all electrodes, and patients tend to prefer eSRT-based MAPs over behavioral MAPs. The main objective of this study is investigate there is a link between subjective comfort levels (C-subjective levels) and the eSRT.