Maps created using a new objective procedure (C-NRT) correlate with behavioral, loudness-balanced maps: a study in adult cochlear implant users

Abstract

In uncooperative patients, electrical compound action potential (ECAP) thresholds are reliable in predicting T-levels, but are not in determining the C-level profile. The present study aims to assess if the C-level profile can be predicted by a new objective procedure (C-NRT) which uses the amplitude growth function (AGF) and is based on the assumption that equal ECAP amplitudes elicit equal loudness percepts. This is a correlational study conducted in five tertiary care referral hospitals with 21 post-lingually deaf adult cochlear implant users. Two maps were created: a behavioral, bitonal balanced (BB) map and an objective map, in which T-levels were the same as in the BB map, and C-levels were obtained with C-NRT. C-NRT consisted of performing the AGF of nine electrodes, and of setting the current level eliciting a 100 μV ECAP amplitude as C-level in the map. AutoNRT was also measured. Main outcome measures were correlation between behavioral C-profile level, objective C-profile level, behavioral T-profile level and objective T-profile (AutoNRT) level; disyllabic word recognition scores in quiet and in noise conditions (SNR = + 10 and 0) with both maps. A strong correlation was found between behavioral and C-NRT-derived C-levels (mean per electrode correlation: R = 0.862, p < 0.001). C-NRT could predict behavioral C-levels with a greater accuracy than AutoNRT. Word recognition was significantly better with BB maps only in the quiet condition (p = 0.002). C-NRT is more accurate than AutoNRT in predicting the C-level profile in adult cochlear implant users. This finding encourages future application in uncooperative patients, especially in very young children.

Efficacy of using NRT thresholds in cochlear implants fitting, in prelingual pediatric patients

“… Scorpecci et al. (2016) found a significant correlation between NRT and behavioural levels in adult patients, and they practically specified C-NRT as more accurate than Auto-NRT in predicting C-levels.…”

Speech-in-noise performance in objectively determined cochlear implant maps, including the effect of cognitive state

“…Initial investigations used the electrically-evoked compound actional potential (eCAP) or electrically-evoked auditory brainstem response (eABR), however prior work has shown weak correlations with behaviourally-determined MAPs, and a tendency to overestimate comfort levels, resulting in over-stimulation in 28% of cases [ 12 , 13 ]. More recently, the electrically-evoked stapedial reflex (eSRT) has been investigated as a more sensitive alternative [ 14 – 16 ].…”

Accessing the stapedius muscle via novel surgical retrofacial approach during cochlear implantation surgery: Intraoperative results on feasibility and safety

“…The main drawback of such behavioral-based fitting procedures is the intrinsic subjectivity of the CI users' answers or their limited and variable ability to actively participate in the behavioral fitting process (e.g., small implanted children or cognitively impaired patients). This affects the reliability and reproducibility of the final outcome [4][5][6][7][8][9]. The stapedius reflex (SR) is an involuntary contraction of the stapedius muscle (SM) elicited in response to loud sound stimuli.…”