Psychophysical and Electrophysiological Parameters of the Auditory Analyzer as Indicators of the Effectiveness of Cochlear Implantation in Children with Bilateral Deafness

Abstract

Background. The results of rehabilitation of patients with deafness after cochlear implantation (CI) depends on many factors related on both the individual characteristics of the patient and the technical parameters of auditory nerve stimulation — fitting of the CI system processor. Article presents the results of a study of the relationship between psychophysical (subjective) auditory sensations and electrophysiological (objective) responses of the structures of the auditory analyzer to electrical stimulation. Aims — to evaluate the relationship between the electrophysiological responses of the auditory analyzer and the psychophysical parameters of the thresholds of sound perception and speech intelligibility in patients with deafness after CI. Methods. The study involved 88 patients with IV bilateral sensorineural hearing loss, borderline with deafness, aged 6 to 17 years 11 months, among whom 54.5% (n = 48) of girls and 45.5% (n = 40) of boys. Of the patients included in the follow-up, 40% (n = 35) underwent unilateral CI; 60% (n = 53) of children underwent bilateral sequential CI. In our study, slightly more than half of the patients (51.1%) had experience using the CI system for more than 5 years. At the first stage of the study, we studied the relationship between sound perception thresholds (tonal audiometry in a free field) and registered ASSR (auditory steady state response) thresholds in patients with deafness receiving rehabilitation after CI surgery. The relationship between behavioral and electrophysiological (objective) thresholds was assessed by comparing the results of tonal threshold audiometry and the responses received during ASSR registration to acoustic stimulation in a free field. At the second stage, patients with indications for processor fitting (decreased speech intelligibility, uncomfortable sensations) underwent speech audiometry, evoked compound action potentials (ECAP) registration, according to the results of which the parameters of the CI processor were changed. Results. Research data showed the effectiveness of the approach of including the ECAP registration test, followed by the creation of a fitting card and correction of the level of auditory nerve stimulation under the control of speech audiometry in the protocol of fitting the CI processor. Conclusions. The results of the conducted studies allow us to recommend the use of the developed method of objective recording of sound perception thresholds in patients with CI as one of the indicators of the effectiveness of CI in the early period of auditory-speech rehabilitation in patients with undeveloped speech skills and when it is impossible to conduct objective tests accompanied by supra-threshold stimulation of the auditory nerve.