Changes of impedance, threshold and comfortable levels upon years in cochlear implants

In various implant models and/or after new implant design, levels of electrical stimulation, change and stability of impedance, have been researched by many researchers. Researches are generally done for a short period of time because backup of data are not taken properly and time after stability is not too much considered. Moreover types of implant used at the clinic are limited. In this study electrical stimulant levels (T and C values) and impedance are retrospectively researched according to two various implant models, electrodes and records repeated in years.This study is carried out in Republic of Turkey Health Ministry Ankara Numune Hospital and Republic of Turkey Health Ministry Yıldırım BEYAZIT Dışkapı Hospital between years 2003 -2007 among 69 cochlear implant patients (49 Fredom implant model; CI24RE and 24 Contour Implant Model; CI24R (CA)) that are examined by our study team during three years by retrospective T&C levels and Common Ground Impedance values. Average age of patients is 3,23 (Min. Age :1, max. Age 8, standart deviation: 2, 02). %58 of cochlear users are men (40) whereas %42 of cochlear user are women (29). Records are taken twice in the first year, once in the second and once third year (totaly 4 records in 3 years).There is not any significant difference in the values of impedance considering electrodes and implant models. Impedance, electrical stimulations levels (T,C) has maintained its stability in both implant models in also second and third years. T and C levels in ?Freedom? Implant Model are significantly lower than the values obtained in ?Nucleus 24 Contour? Implant Model. However, dynamic intervals are similar in both models. In both models, there are significant differences between Apical and Basal electrodes in T and C values. There is not any significant difference in T levels according to years in both models.The results obtained through this study shows that, in both implant models Impedance, T and C levels preserved their stability in the second and third years. Because of this, changes on C level (which is one of the basic parameters) among children must be considered in minimal level in the second and third years. The main difference between implants models can be explained by the improvement of electrode design (closer to the modiolous) in Fredom Implant to be better than ?Nucleus 24 Contour?. Values obtained according to years lead point of view for programming of various implant models.