Round window stimulation with the floating mass transducer at constant pretension

Area of Science:

• Otolaryngology
• Biomedical Engineering
• Auditory Neuroscience

Background:

• Mechanical stimulation of the round window (RW) is crucial for cochlear implants like the Vibrant Soundbridge.
• Clinical outcomes exhibit significant variability, partly due to inconsistent static force applied by the stimulator.
• Investigating other factors influencing RW stimulation variability is essential for improving device efficacy.

Purpose of the Study:

• To investigate sources of variability in round window (RW) stimulation beyond static force.
• To evaluate the effect of a coupler device and soft tissue interposition on RW stimulation.
• To maintain a constant pre-load during testing to isolate the effects of coupling conditions.

Main Methods:

• Experimental study using fresh human temporal bones.
• Measured stapes footplate displacement using Laser Doppler Velocimetry.
• Stimulated the RW with a Floating Mass Transducer (FMT) with and without a coupler and TUTOPATCH soft tissue, maintaining a constant pre-load of ~1.96 mN.

Main Results:

• Using the coupler and TUTOPATCH interposition increased the average sound output by 11.9 dB (500 Hz-2 kHz).
• This increase was statistically significant at 500 Hz (p < 0.01).
• The combination significantly reduced experimental variability (SD from 10.9 dB to 3.4 dB at 500 Hz) and improved repeatability.

Conclusions:

• A coupler and TUTOPATCH combination optimizes round window (RW) stimulation with the Floating Mass Transducer (FMT) at controlled static force.
• Clinical variability in cochlear implant outcomes is influenced by coupling conditions, not solely inter-subject differences.
• Further optimization of coupling conditions can enhance the performance of RW stimulation devices.