Journal
LARYNGOSCOPE
Volume 118, Issue 3, Pages 483-490Publisher
WILEY
DOI: 10.1097/MLG.0b013e31815b0d9f
Keywords
Tympanic membrane; middle ear; collagen fibers; myringoplasty
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Objective: To investigate the significance of tympanic membrane collagen fiber layers in high frequency sound transmission. Study Design: Human cadaver temporal bone study. Methods: Laser Doppler vibrometry was used to measure stapes footplate movement in response to acoustic stimulation. The tympanic membrane was altered by creating a series of slits and applying paper patches to isolate the effects of specifically oriented collagen fibers. Three groups of membrane alterations were evaluated: 1) circumferentially oriented slits involving each quadrant to primarily disrupt radial fibers, made sequentially within superior-anterior, inferior-anterior, inferior-posterior, and superior-posterior quadrants; 2) the same slits made in the reverse order; and 3) radially oriented slits from the umbo to the annulus to primarily disrupt circumferential fibers. For each group, measurements of the middle-ear cavity pressure, ear canal pressure, and stapes velocity were made each time the tympanic membrane was altered. Results: Regardless of the order in which the circumferentially oriented slits were made, there was a consistent decrease in stapes velocity above 4 kHz for the third and fourth cuts compared to the control. The mean decrease in the range of 4 to 12.5 kHz was 11 dB for the third patched slit and 14 dB for the fourth patched slit (P <.01). Radially oriented slits appear to produce smaller effects. Conclusions: Radial collagen fibers in the tympanic membrane play an important role in the conduction of sound above 4 kHz.
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