Cochlear implant: correlation of nerve function recovery, auditory deprivation and etiology

Neural recovery function of the auditory nerve in cochlear implant surgery: Comparison between different regions of the cochlea

INTRODUCTION

Cochlear implants allow measures of neural function, through Neural response telemetry (NRT) and Auditory nerve recovery function (REC). These help in programming the speech processor and understanding the auditory system. However, not many studies have evaluated and compared these in different regions of the cochlea.

OBJECTIVE

Comparing NRT and REC in different regions of the cochlea.

METHODS

Cross-sectional, descriptive and prospective. NRT and REC (through the function of T0 - absolute refractory period, A - amplitude and TAU - time constant of the relative refractory period parameters) were evaluated, in three groups according to the stimulated electrode of the cochlea: apical, medial and basal.

RESULTS

26 adult patients were evaluated, 2 bilateral, totalling 28 ears. Data analysis showed no statistically significant difference between NRT between medial and basal but showed between apical and medial and apical and basal. For T0, there was a significant difference between medial and basal; for A, there was a significant difference between apical and basal and also medial and basal; and for TAU, there was no significant difference.

CONCLUSION

There was a statistically significant difference in NRT and REC when compared between different regions of the cochlea.

Neural Recovery Function of the Auditory Nerve in Cochlear Implant Surgery: Comparison between Prelingual and Postlingual Patients

Introduction  Cochlear implants (CIs) enable objective measures of the neural function in implanted patients through the measurements of the neural response telemetry (NRT) and of the Auditory nerve Recovery Function (REC). These measurements help in programming the speech processor and understanding the auditory system. Objective  To compare the NRT and the REC in prelingual and postlingual implanted patients. Methods  An observational, descriptive and prospective study was carried out. The NRT and the REC (through the T0, A, and tau parameters) were evaluated in individuals submitted to CI surgery, who were divided into two groups: prelingual and postlingual patients. Results  In total, 46 patients were evaluated. Data analysis showed no statistically significant difference between the NRT measurements and the T0, A, and Tau of the REC in the comparison between the two groups, except for the NRT in the basal cochlear region. Conclusion  There was no statistically significant difference in the REC in pre- and postlingual patients.

Intraoperative Neural Response Telemetry and Neural Recovery Function: a Comparative Study between Adults and Children

Introduction Neural response telemetry (NRT) is a method of capturing the action potential of the distal portion of the auditory nerve in cochlear implant (CI) users, using the CI itself to elicit and record the answers. In addition, it can also measure the recovery function of the auditory nerve (REC), that is, the refractory properties of the nerve. It is not clear in the literature whether the responses from adults are the same as those from children.

Objective To compare the results of NRT and REC between adults and children undergoing CI surgery.

Methods Cross-sectional, descriptive, and retrospective study of the results of NRT and REC for patients undergoing IC at our service. The NRT is assessed by the level of amplitude (microvolts) and REC as a function of three parameters: A (saturation level, in microvolts), t0 (absolute refractory period, in seconds), and tau (curve of the model function), measured in three electrodes (apical, medial, and basal).

Results Fifty-two patients were evaluated with intraoperative NRT (26 adults and 26 children), and 24 with REC (12 adults and 12 children). No statistically significant difference was found between intraoperative responses of adults and children for NRT or for REC's three parameters, except for parameter A of the basal electrode.

Conclusion The results of intraoperative NRT and REC were not different between adults and children, except for parameter A of the basal electrode.