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Introduction: The aim of our study is to determine the characteristics of sound localization observed in patients with bilateral cochlear implantation. Methods: This study involved 38 participants with bilateral sensorineural deafness of different etiologies. Each of the participants underwent cochlear implantation of Concerto implants (Med-El, Austria). 16 of these participants underwent bilateral implantation and 22 underwent unilateral implantation. The participants' age's ranged from 7 to 21 years, with participants having previous experience of CI use from the ages of 2 to 13 years. 20 patients with intact hearing were included into the control group. In order to determine localization, an acoustic station was utilized consisting of 21 speakers arranged along a horizontal plane in a semicircular orientation. The system was connected to a sound source that generated modulated tones with a frequency of 1,000 Hz, and a sound intensity of 70 dB. Each participant received 105 modulated signals from different speakers randomly, and they had to identify the direction of the sound source. Results: During this study, it was observed that the average number of errors measured in participants with intact hearing ability was 31%, in subjects with two CIs was 84%, and in participants with one CI was 87%. It was concluded that the number of errors recorded in participants with one and with two CIs were almost the same; however, when examining the structure of the errors, a slightly different pattern was observed, whereby the average degree of error in participants with an intact hearing ability was 3,5&#176, in participants with two implants was 32.1&#176, and it was 61.2° for participants with one implant. Conclusion: The results obtained within this study show a significant improvement of the spatial sound localization in participants with two CIs when compared to those with only one CI, which demonstrates the importance of having a second ear cochlear implantation performed. [ABSTRACT FROM AUTHOR]

Objectives. It has been suggested that the density of spiral ganglion neurons will affect on speech intelligibility. The results of previous studies shows that the supra-threshold characteristics of the Evoked Compound Action Potentials (ECAP) characterize the condition of spiral ganglion neurons. Aim of this paper is to evaluate the dependence of maximum comfort levels on ECAP parameters (threshold and amplitude). Materials and methods. The study included fitting data of 20 patients with sensorineural hearing loss with unilateral cochlear implantation. All patients were implanted with the Med-El (Sonata or Concerto) CI system with a standard electrode array. The results of electrodes impedance did not exceed 10 kΩ. Auditory development was assessed depending on the age of the patient and the condition of the hearing skills. Recognition results exceeded 90%. Results. A correlation between comfort levels and ECAP thresholds was found. The values of the comfort levels were reduced when ECAP amplitude was increased. Conclusions. ECAP thresholds can not be considered as an absolute reference point for determining the CI comfort levels. The amplitude of the ECAP response is one of the indicators of the preservation of the neurons of the auditory nerve. The correlation of the ECAP thresholds and comfort levels higher when ECAP amplitude values increase. [ABSTRACT FROM AUTHOR]