Tympanic membrane retraction and middle-ear pressure

Area of Science:

• Otoacoustic Emissions
• Audiology
• Middle Ear Physiology

Background:

• Clinical assessments like malleus head (MHA) assessment and light reflex (LR) observation are commonly used.
• These methods are often employed to estimate middle ear pressure (MEP).
• However, their accuracy in reflecting actual MEP requires further investigation.

Purpose of the Study:

• To evaluate the reliability of MHA assessment and LR observation as indicators of middle ear pressure (MEP).
• To compare clinical assessments with MEP measurements obtained via impedance tympanometry.
• To investigate the relationship between tympanometric changes and the physical movement of the tympanic membrane (TM).

Main Methods:

• Clinical assessment of MHA and LR in normal ears.
• MEP measurement using impedance tympanometry across a pressure range of -300 to +160 mm H2O.
• MEP variation analysis in fresh temporal bones under varying pressure conditions (-50 to -400 mm H2O and +50 to +400 mm H2O).

Main Results:

• MHA assessment and LR observation showed poor correlation with MEP measured by impedance tympanometry.
• In fresh temporal bones, MHA, LR, and postero-superior segment retraction remained stable across wide pressure ranges (+/- 50 to +/- 400 mm H2O).
• The most significant compliance changes, indicated by the tympanometric notch width, corresponded to TM position shifts within +/- 50 mm H2O.

Conclusions:

• Clinical MHA and LR assessments are inadequate indicators of MEP.
• Impedance tympanometry, particularly the tympanometric notch width, provides a more accurate measure of middle ear pressure and TM compliance.
• Understanding TM displacement relative to pressure is crucial for accurate middle ear assessment.