Effect of middle ear components on eardrum quasi-static deformation

Area of Science:

• Otoacoustic emissions
• Biomechanics of the ear
• Middle ear mechanics

Background:

• Understanding eardrum mechanics is crucial for diagnosing and treating middle ear pathologies.
• Previous studies have focused on intact middle ear systems, limiting insights into the specific roles of individual components.

Purpose of the Study:

• To quantify eardrum deformation under varying middle ear pressures during progressive dissection of gerbil temporal bones.
• To determine the influence of specific middle ear structures on static eardrum displacement.

Main Methods:

• Utilized a high-resolution moiré interferometer to measure eardrum shape and deformation.
• Performed serial dissections of gerbil temporal bones, including removal of the cochlea and stapes, and cutting of the tensor tympani and malleus connections.
• Recorded eardrum displacement along a line perpendicular to the manubrium and through the umbo at different middle ear pressures.

Main Results:

• Removal of the cochlea and stapes, and cutting the tensor tympani, did not alter static eardrum deformation.
• Exposing the incudo-mallear joint led to increased eardrum movement.
• Severing the anterior bony connection of the malleus to the tympanic bone significantly changed the eardrum's resting position and further increased its displacement.

Conclusions:

• The malleus-tympanic bone connection plays a critical role in stabilizing the eardrum's resting position and influencing its static deformation.
• The cochlea, stapes, and tensor tympani have minimal impact on static eardrum mechanics in the studied gerbil model.
• These findings provide valuable biomechanical insights into middle ear function and potential surgical interventions.