Conductive Hearing Loss and Carhart’s Notch Mark Domanski, M.D. Faculty Advisor: Tomoko Makishima, M.D., Ph.D. Discussant: Francis B. Quinn, M.D., FACS The University of Texas Medical Branch Department of Otolaryngology Grand Rounds Presentation June 4, 2008
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Conductive Hearing Loss and
Carhart’s Notch
Mark Domanski, M.D.
Faculty Advisor: Tomoko Makishima, M.D., Ph.D.
Discussant: Francis B. Quinn, M.D., FACS
The University of Texas Medical Branch
Department of Otolaryngology
Grand Rounds Presentation
June 4, 2008
Conductive Hearing Loss and
Carhart’s Notch
• Physics of Sound
• Physics of Conductive Hearing
• Tympanogram and the Acoustic Reflex
• Physiopathology of Carhart’s Notch
• Diagnostic Implications of Carhart’s Notch
Conductive Hearing Loss and
Carhart’s Notch
• Physics of Sound
• Physics of Conductive Hearing
• Tympanogram and the Acoustic Reflex
• Physiopathology of Carhart’s Notch
• Diagnostic Implications of Carhart’s Notch
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
Cycles per second (Hz)
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
distance between repeating units of a propagating wave
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
Implication of a repeating event
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
The amplitude is a nonnegative scalar measure of a wave's magnitude of oscillation
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
• intensity is a measure of the energy flux.
• "intensity" is not synonymous with "strength", "amplitude", or "level“
Sound Intensity is Analogous to
Electrical Flux
•If a point source is radiating energy in three dimensions and there is no energy lost to the medium, then the intensity decreases in proportion to distance from the object squared
http://web.ncf.ca/ch865/graphics/ElectricFlux
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
• distance such a wave travels per unit time
• speed 770 mph, or 1130 ft/s) in dry air at 70 degrees F
• speed of sound – increases with the stiffness of the material
– decreases with the density
• Frequency
• Wavelength
• Period
• Amplitude
• Intensity
• Speed
• Direction
Resonance: The tendency of a system to oscillate at maximum amplitude at certain frequencies
• Small periodic driving forces can produce large amplitude vibrations
• If the monkey pushes the ball at the natural frequency (fundamental frequency) of the swing, the ball will go higher and higher
Cook, Krishnan, Fagan, Quantifying the Carhart Effect in Otosclerosis. Clin.
Otolaryngol. 1995, 20, 258-261.
Quantifying the Carhart Effect in
Otosclerosis
Change in Bone conduction is partially dependent upon air bone gap closure. To model the effect of Carhart’s notch, we can express change in bone conduction as a function of change in air conduction.
dBC = change in bone conduction
dAC = change in air conduction
CC = frequency depended Carhart co-efficient
K = frequency dependent constant
ABGC = air-bone gap closure
Pre Op
BC1 15
air bone gap 25
AC1 40
Post Op
BC2 5
air bone gap 5
AC2 10
dBC
dBC
dBC
ABCG
K cc
dBC
ABCG
K cc
dBC
dAC
Now we can do our
regression
Online Equation Editor
http://www.homeschoolmath.net/worksheets/equat
ion_editor.php
Quantifying the Carhart Effect in
Otosclerosis Median Hearing Threshold changes (dB)
kHz Air
conduction
Bone
conduction
Air-Bone
gap
0.5 30 5 25
1 20 5 15
2 20 10 10
4 10 5 5
Cook, Krishnan, Fagan, Quantifying the Carhart Effect in Otosclerosis. Clin. Otolaryngol. 1995, 20, 258-261.
•A significant relationship
between the change in air-
bone gap closure and
change in bone
conduction was found only
at 2 kHz.
•Interesting from a
mathematical modeling
standpoint.
dBC
dAC
Conclusion
dBC
dAC
References
• Cook, Krishnan, Fagan, Quantifying the Carhart Effect in Otosclerosis. Clin. Otolaryngol. 1995, 20, 258-261.
• Yasan, Predictive role of Carhart’s notch in pre-operative assessment for middle-ear surgery. J. of Laryngology & Otology (2007), 121, 219-221.