Risks of Intracochlear Pressures From Laser Stapedotomy

Abstract

Hypothesis: Surgical manipulations during laser stapedotomy can produce intracochlear pressure changes comparable to pressures created by high-intensity acoustic stimuli. Background: New-onset sensorineural hearing loss is a known risk of stapes surgery and may result from pressure changes from laser use or other surgical manipulations. Here, we test the hypothesis that high sound pressure levels are generated in the cochlea during laser stapedotomy. Methods: Human cadaveric heads underwent mastoidectomy. Fiber-optic sensors were placed in scala tympani and vestibuli to measure intracochlear pressures during key steps in stapedotomy surgery, including cutting stapedius tendon, lasering of stapedial crurae, crural downfracture, and lasering of the footplate. Results: Key steps in laser stapedotomy produced high-intensity pressures in the cochlea. Pressure transients were comparable to intracochlear pressures measured in response to high intensity impulsive acoustic stimuli. Conclusion: Our results demonstrate that surgical manipulations during laser stapedotomy can create significant pressure changes within the cochlea, suggesting laser application should be minimized and alternatives to mechanical downfracture should be investigated. Results from this investigation suggest that intracochlear pressure transients from stapedotomy may be of sufficient magnitude to cause damage to the sensory epithelium and affirm the importance of limiting surgical traumatic exposures.

Effects of Varying Laser Parameters During Laser Stapedotomy on Intracochlear Pressures

“…To begin to fill this gap, we examined the effects of varying laser parameters on intracochlear pressure (P IC ) on human cadaveric specimens. This represents the continuation of a study investigating the risks during laser stapedotomy recently conducted and published by our laboratory 9 . This work demonstrated that surgical manipulations during laser stapedotomy create significant pressure changes within the cochlea.…”

“…Similar measurements in living patients are difficult and ethically concerning. We have utilized comparable methods to provide quantitative estimates of resulting noise exposure from blast exposure, cochlear implant insertion, drill use, and laser use 9,10,14,28 . Our results reveal that P IC is significantly elevated during laser application and that pressures increase with increasing laser power.…”

“…A thorough examination of the specimen occurred prior to any surgical intervention. Temporal bone preparation was similar to methods described previously 9‐11 . Heads were thawed, inspected for damage, and prepared with a canal wall up mastoidectomy and extended facial recess approach to visualize the stapes and round window.…”

“…Temporal bone preparation was similar to methods described previously. [9][10][11] Heads were thawed, inspected for damage, and prepared with a canal wall up mastoidectomy and extended facial recess approach to visualize the stapes and round window. The cochlear promontory near the oval and round windows was blue lined with a 0.5-mm diamond burr in preparation for sensor insertion into the scala vestibuli and scala tympani.…”

Methods and reference data for middle ear transfer functions

“…Only freshly frozen TBs were used. The collected data from this group 17 , 18 will be denoted as “Colorado”. Because the point of measurement is different, we label this data as method “D”.…”