Review of Whole Head Experimental Cochlear Promontory Vibration with Bone Conduction Stimulation and Investigation of Experimental Setup Effects.
Srdjan Prodanovic, Stefan Stenfelt
PMID 34709076WHAT IT FOUND
Bone conduction vibration at the cochlea was broadly similar across implant-stimulation studies when force was known.
Skin placement and setup details changed measured levels, so device comparisons need force, position, and calibration.
Key findings
01Nine studies were included because the bone-conduction stimulation force was measured or could be estimated.
02With implant stimulation, cochlear promontory vibration levels were typically within 10 dB across studies.
03Replacing the brain with air did not change cochlear vibration, but replacing it with liquid reduced vibration by up to 5 dB.
STILL TO COME
How it was doneWhat they found
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What it does not show
Not all bone-conduction vibration studies could be compared because some did not report the stimulation force or the transfer function needed to estimate it. The review included only nine studies, and some experimental conditions were represented by just one or two studies. The measurements were of cochlear vibration in cadaver heads, whole cadavers, and live subjects, not of hearing, communication, or patient outcomes. The finite element model used simplified assumptions about tissue properties, neck fixation, and skin thickness, so it did not match all experimental high-frequency results. Skin attenuation estimates were affected by differences in stimulation position and by calibration of the transducer force.
The easy way to misread this
Do not read the similar vibration levels as evidence that bone-conduction devices improve hearing. This paper reports mechanical vibration measurements in heads and simulations, not patient hearing outcomes.