gms | German Medical Science

Introduction: The goal is the comparison of intra and post surgical electrical elicited ipsilateral stapedius reflex thresholds with the most convenient levels (MCL) of loudness as a fitting parameter of a cochlea implant speech processor.

Methods: A GSI-Tympanometer in the modi tympanogram and reflex decay was used to show tympanum’s normal compliance and stapedius reflexes respectively. The activation of the acoustic nerve was induced by electrical stimulation of several cochlea implant electrodes.

Results: Visual and tympanometric intra surgical measured reflex thresholds differ in mean by (0.06 ± 0.26) cu (charge units). The mean difference of intra and post surgical tympanaometric measured reflex thresholds results in (1.17 ± 2.35) cu. For four patients the mean quotient of MCL’s and post surgical stapedius reflex thresholds was (0.81 ± 0.22). These reflexes couldn’t electrically elicited in three other patients because of reaching the unconvenient levels of loudness before. The mean quotient of MCL’s and intra surgical stapedius reflex thresholds results in (0.68 ± 0,14) for all patients. The quotient of higher intra and lower post surgical stapedius reflex thresholds is in mean 1.2 . Up to 97% of MCL’s are under the values of the intra and up to 82% are under the values of post surgical stapedius reflex thresholds.

Conclusions: To avoid an over-stimulation, the initial MCL’s in fitting of a speech processor should not higher than 0.5 to 0.7 times of the ipsilateral intra or post surgical stapedius reflex thresholds. This is important in fitting of little children and patients with problems to describe a convenient loudness sensation.