The impact of tympanic membrane perforations on middle ear transfer function

Area of Science:

• Otolaryngology
• Biomedical Engineering
• Acoustics

Background:

• Middle ear injury or inflammation can cause persistent tympanic membrane (TM) perforations.
• These perforations lead to conductive hearing loss (HL).
• The extent of HL can sometimes exceed what is expected from TM perforation alone.

Purpose of the Study:

• To investigate how the location and size of TM perforations affect middle ear sound transmission.
• To understand the mechanisms behind hearing loss associated with TM perforations.

Main Methods:

• Measured middle ear transfer functions (METF) in six human temporal bones before and after creating TM perforations of varying sizes and locations.
• Used laser-Doppler-vibrometry (LDV) to measure stapes footplate velocity.
• Correlated experimental data with a Finite Element (FE) model simulating TM perforations.

Main Results:

• Both measured and simulated METF showed frequency and perforation size-dependent sound transmission losses.
• Larger perforations resulted in losses extending to higher frequencies.
• Posterior TM perforations caused greater transmission impairment than anterior perforations.
• Simulations indicated small perforations decrease TM rigidity, increasing oscillation amplitude above 1 kHz.

Conclusions:

• TM perforation size and location uniquely influence METF.
• The combination of LDV measurements and FE modeling enhances understanding of middle ear disease pathology.
• Significant HL with small TM perforations warrants consideration of additional middle ear pathologies.