Intracochlear Pressure Transients During Cochlear Implant Electrode Insertion.

Area of Science:

• Otoacoustic emissions and inner ear physiology
• Biomedical engineering and medical device design
• Neurosurgery and audiology

Background:

• Many cochlear implant (CI) patients retain low-frequency hearing, which CI devices aim to preserve.
• Hair cell and auditory nerve fiber function are crucial for residual hearing preservation.
• Some patients experience hearing loss after CI insertion, possibly due to surgical trauma.

Purpose of the Study:

• To investigate the hypothesis that CI electrode insertion causes intracochlear pressure transients.
• To determine if these pressure transients can damage cochlear structures and compromise residual hearing.

Main Methods:

• Human cadaveric temporal bones were used with an extended facial recess approach.
• Fiber-optic pressure sensors measured pressure in the scala vestibuli and tympani.
• Five CI electrode styles from two manufacturers were inserted via the round window.

Main Results:

• CI insertion generated pressure transients exceeding 170 dB SPL.
• Pressure transients were generally larger in the scala tympani than the scala vestibuli.
• The magnitude and occurrence of pressure transients varied with electrode style.

Conclusions:

• Electrode design, insertion method, and surgical technique influence intracochlear pressure transients.
• These pressure transients possess intensities similar to damaging high-level sounds.
• The findings suggest a mechanism for hair cell and basilar membrane damage during CI surgery.