HYPOTHESIS: Mechanical stimulation through a cochlear third window into the scala tympani in a chinchilla model with normal and fixed stapes can generate cochlear responses equivalent to acoustic stimuli. BACKGROUND: Cochlear stimulation via the round window (RW) using active middle ear implants (AMEIs) can produce physiologic responses similar to acoustic stimulation including in a model of stapes fixation. However, pathologic conditions, such as advanced otosclerosis, can preclude delivery of sound energy to the cochlea through the oval window and/or the RW. METHODS: Cochlear microphonic (CM) and laser Doppler vibrometer measurements of stapes and RW velocities were performed in 6 ears of 4 chinchillas. Baseline measurements to acoustic sinusoidal stimuli (0.25-8 kHz) were made. Measurements were repeated with an AMEI driving the RW or a third window to the scala tympani before and after stapes fixation. RESULTS: AMEI stimulation of the third window produced CM waveforms with morphologies similar to acoustic stimuli. CM thresholds with RW and third-window stimulation were frequency dependent but ranged from 0.25 to 10 and 0.5 to 40 mV, respectively. Stapes fixation, confirmed by laser Doppler vibrometer measurements, resulted in a significant frequency dependent impairment in CM thresholds up to 13 dB (at <3 kHz) for RW stimulation and a nonsignificant frequency-dependent improvement of up to 10 dB (at >3 kHz) via third-window stimulation. CONCLUSION: AMEI mechanical stimulation through a third window into the scala tympani produces physiologic responses nearly identical to acoustic stimulation including in a model of stapes fixation with decreased efficiency.
HYPOTHESIS: Mechanical stimulation through a cochlear third window into the scala tympani in a chinchilla model with normal and fixed stapes can generate cochlear responses equivalent to acoustic stimuli. BACKGROUND: Cochlear stimulation via the round window (RW) using active middle ear implants (AMEIs) can produce physiologic responses similar to acoustic stimulation including in a model of stapes fixation. However, pathologic conditions, such as advanced otosclerosis, can preclude delivery of sound energy to the cochlea through the oval window and/or the RW. METHODS: Cochlear microphonic (CM) and laser Doppler vibrometer measurements of stapes and RW velocities were performed in 6 ears of 4 chinchillas. Baseline measurements to acoustic sinusoidal stimuli (0.25-8 kHz) were made. Measurements were repeated with an AMEI driving the RW or a third window to the scala tympani before and after stapes fixation. RESULTS: AMEI stimulation of the third window produced CM waveforms with morphologies similar to acoustic stimuli. CM thresholds with RW and third-window stimulation were frequency dependent but ranged from 0.25 to 10 and 0.5 to 40 mV, respectively. Stapes fixation, confirmed by laser Doppler vibrometer measurements, resulted in a significant frequency dependent impairment in CM thresholds up to 13 dB (at <3 kHz) for RW stimulation and a nonsignificant frequency-dependent improvement of up to 10 dB (at >3 kHz) via third-window stimulation. CONCLUSION: AMEI mechanical stimulation through a third window into the scala tympani produces physiologic responses nearly identical to acoustic stimulation including in a model of stapes fixation with decreased efficiency.
Authors: Thomas D Weddell; Yury M Yarin; Markus Drexl; Ian J Russell; Stephen J Elliott; Andrei N Lukashkin Journal: J R Soc Interface Date: 2014-02-05 Impact factor: 4.118
Authors: Nicolas Verhaert; Joris Walraevens; Christian Desloovere; Jan Wouters; Jean-Marc Gérard Journal: PLoS One Date: 2016-08-08 Impact factor: 3.240