gms | German Medical Science

The Advanced Bionics HiRes mode was introduced together with a new fitting strategy intended to be more representative of everyday listening, this approach uses a speech burst on a group of three or four neighbouring channels instead of a burst on one channel. In addition it is no longer necessary to fit the T-levels and only M-levels are required.  If objective measures are used for prediction of HiRes levels their stimulation signal should be adapted to the new needs as well.  It was found in the past that the stapedius reflex threshold (ESRT) correlates well with the postoperative M-level. Therefore this prospective clinical study was initiated to determine the predictive value of the intra-operatively ESRT evoked by a speech burst for prediction of post-operative M-levels. ESRT was determined intra-operatively in more than 20 adults using a sequential 16 channel program in Soundwave with default settings stimulating with speech bursts. This results in an ESRT value for 7 groups each with four channels for the individual subjects. Post-operative fitting was performed for 16 channel sequential programs without knowing the results of the intra-operative measures. In a sub-group the ESRT was measured with the conventional signal, a single channel burst. ESRT was correlated to the M-level used in the subjects' 16 channel sequential program three months after first fitting. In all subjects the ESRT could be evoked and the M-level was found to be at about 80% of the ESRT. In the majority of subjects the profile of the ESRT fits well to the profile of M-levels. In the medial part of the electrode array a correlation of 0.7 was found, whereas the correlation in the apical and basal part was poorer. As known from early studies ESRT is a valuable tool for the estimation of postoperative M-level. With the new fitting strategy of HiRes the ESRT introduces even more flexibility to the fitting process than in conventional strategies.