Multifrequency immittancemetry in experimentally induced stapes, round window and cochlear lesions.

Area of Science:

• Otoacoustic emissions and audiology
• Middle and inner ear physiology

Background:

• Tympanometry is a standard audiological test.
• Understanding the relationship between tympanometry and inner ear mechanics is crucial for diagnosing auditory pathologies.

Purpose of the Study:

• To determine if admittance (Y), susceptance (B), and conductance (G) tympanograms at 2 kHz can indicate the condition of the annular ligament and cochlear pressure.
• To investigate the effects of experimental modifications on tympanometric parameters.

Main Methods:

• Experiments were conducted on 22 guinea pigs.
• Procedures included bulla ventilation, stapes and round window membrane (RWM) blockage, fistula creation, cochlear fluid removal, scala tympani saline injection, and acoustic trauma.
• Resonance frequency, Y, B, and G at 2 kHz, and tympanogram curve shapes were analyzed before and after interventions.

Main Results:

• A supplementary peak in Y/G tympanograms was observed in RWM fistulas and some acoustic trauma cases.
• Saline injection into the scala tympani caused consistent, immediate, and reproducible tympanometric changes.
• RWM and stapes blockages resulted in predictable peaking at 2 kHz.
• Cochlear fluid removal led to multiple peak curves.

Conclusions:

• Experimental alterations to the annular ligament produce significant, consistent, and reproducible changes in 2 kHz tympanogram curves.
• These tympanometric changes appear to correlate with and reflect inner ear pressure variations.