Introduction:
The direct drive simulation (DDS) offers patients a preoperative sound simulation
of the active middle ear implant "Vibrant Soundbridge®. The floating mass transducer
(FMT) is placed on the eardrum or on the tympanic membrane graft, where the signals
are applied. The aim of this study was to develop and to evaluate a specific Direct
Drive-Pure-Tone-Audiometry (DD-PTA) as well as a Direct-Drive-Speech-Audiometry (DD-SA).
Material and Methods:
20 normal hearing subjects were tested. Pure-tone-audiometry and speech-audiometry
were performed via the DDS-FMT connected to the output of a standard audiometer. The
results were compared to measurements via insert headphones.
Results:
The median DD-PTA threshold per frequency was: 125 Hz/55dB, 250 Hz/40dB, 500 Hz/25dB,
1 kHz/10dB, 2 kHz/10dB, 3 kHz/20dB, 4 kHz/20dB, 6 kHz/15dB, 8 kHz/15dB. The maximal
interindividual frequency variation was 30dB. In the DD-SA the median intelligibility
for monosyllabic words was measured to be 100% at 65dB, and the median for 50% speech
discrimination of numbers was 30dB.
Discussion:
The DD-PTA threshold curve was congruent with the non-linear frequency characteristics
of the FMT. The DD-SA yielded equivalent results with the corresponding DD-PTA threshold.
Conclusions:
DD-PTA and DD-SA are possible examinations that could be used in the daily clinical
routine. DDS-PTA seems to be a useful indicator of coupling quality and therefore
of interest for the development of DD-BERA as an objective preoperative test procedure.
DD-SA may have prognostic value preoperatively as well. Further test results pre and
post treatment with a VSB will be evaluated.
