Wideband energy reflectance measurements of ossicular chain discontinuity and repair in human temporal bone.
OBJECTIVE
Recent studies have suggested the potential of wideband energy reflectance (ER) for the assessment of middle ear disorders. The purpose of this study was to examine the use of wideband ER in the evaluation of an ossicular discontinuity and its repair in human cadaver temporal bones.


METHODS
ER measurements at ambient pressure were made on five human cadaver ears in three conditions: (1) baseline with intact ossicular chain, (2) with the ossicular chain cut using an argon laser, and (3) with the ossicular chain repaired. Laser Doppler vibrometry measurements of stapes footplate velocity were also made in the three conditions to monitor the effect of the experimental manipulations on sound transfer through the middle ear.


RESULTS
Disarticulating the ossicular chain resulted in the appearance of a deep notch in ER in each specimen ranging in center frequency from 561 to 841 Hz. The average reduction in ER was 31% at a frequency of 630 Hz. Laser Doppler vibrometry measurements confirmed the effect of the disarticulation and then repair using ionomeric cement. The low-frequency notch in ER was eliminated following repair of the ossicular chain. There was a small decrease in average high-frequency ER for both the cut and repaired conditions. A simple series impedance model of the middle ear was used to model the change in ER based on changes in middle ear impedance. The primary finding of the modeling was that the low-frequency notch in ER in the disarticulated ear occurs at the resonance frequency at which the reactance goes through zero consistent with the data.


CONCLUSIONS
A disarticulation of the ossicular chain in human cadaver ears produces a low-frequency notch in ER that recovers with repair of the disarticulation. These results suggest that ER has the potential for use in the diagnosis of ossicular discontinuity and to monitor the status of the repaired ossicular chain. More data are needed to compare ER results from patients undergoing surgery for ossicular discontinuity with those of patients with other ossicular disorders such as otosclerosis.
Department of Otolaryngology, Head and Neck Surgery, University of Washington, Virginia Merrill Bloedel Hearing Research Center, Seattle, Washington 98195, USA. pfeeney@u.washington.edu
M Patrick
MP
Feeney
Iain L
IL
Grant
David M
DM
Mills
D000158:Acoustic Impedance Tests / Q000379:methods; D000161:Acoustic Stimulation; D002102:Cadaver; D004429:Ear Ossicles / Q000502:physiology*; D006314:Hearing Loss, Conductive / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D006801:Humans; D008954:Models, Biological; D010040:Otosclerosis / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D013701:Temporal Bone / Q000502:physiology*