Computer Microvision Measurements of Stapedial Motion in Human Temporal Bone

Scientists have marveled at the middle ear for centuries. The importance of the middle ear to hearing and the ease which with it may be damaged make an understanding of this system relevant to clinicians. The middle ear functions as a transformer, in which the motion of the stapes is the output and the sound pressure at the tympanic membrane is the input. Though much studied, the relationship between the motion of those two structures has not been well established. Factors such as access to the human middle ear and the ability to resolve three-dimensional modes of motion have impeded progress. While there remains no current method of viewing stapes motion in live humans, a new measurement system promises to quantify more accurately small-scale, three-dimensional motions. Computer microvision is a measurement system which uses computer vision algorithms to estimate motions from stroboscopically illuminated digital images taken through a light microscope. The purpose of this thesis is to apply this system to the sound-induced motions of the stapes in a cadaveric human temporal bone preparation. Results of this application contribute more evidence toward a full characterization of the nature of human stapes motion. Making computer microvision measurements in a range of frequencies from 250 Hz to 6 kHz, I found that stapes motion relative to sound pressure at the tympanic membrane was compliance dominated for frequencies below 800 Hz and achieved resonance at 1.1 kHz. Measurements on the same temporal bone were performed on two separate occasions , and the measurements were repeatable to a factor of two, which is within the range of variation that could be attributed to the condition of the bone. The results show that the stapes translated along some axis, but it was difficult to place that axis in a physiologic frame of reference.