Auditory threshold shift following meatal pressure change in ossicular disorders

Area of Science:

• Otolaryngology
• Auditory Physiology
• Biomedical Engineering

Background:

• Auditory threshold shifts are influenced by external factors like meatal pressure.
• Ossicular abnormalities can alter middle ear mechanics and acoustic responses.
• Understanding these effects is crucial for diagnosing and managing hearing loss.

Purpose of the Study:

• To investigate auditory threshold shifts in response to meatal pressure changes.
• To compare these effects in normal ears versus ears with specific ossicular abnormalities.
• To explore the underlying mechanisms of observed threshold shifts.

Main Methods:

• Auditory thresholds were measured using air conduction.
• Meatal pressure was manipulated with both negative and positive changes (+/- 200 mm H2O).
• Subjects included individuals with normal hearing and those with ossicular abnormalities (fixations, incudostapedial disconnection).

Main Results:

• Normal ears showed elevated thresholds at low frequencies (<1,000 Hz) with both positive and negative meatal pressure.
• Ears with ossicular fixations were less affected by pressure changes compared to normal ears.
• In incudostapedial disconnection, positive pressure elevated thresholds, while negative pressure paradoxically improved low-frequency thresholds by 26-40 dB.

Conclusions:

• Meatal pressure significantly impacts auditory thresholds, with varying effects based on the type of ossicular abnormality.
• The paradoxical threshold gains observed with negative pressure in incudostapedial disconnection suggest mechanisms beyond tympanic membrane compliance.
• Further research is needed to elucidate the complex biomechanical interactions in the middle ear.