The atretic plate--a conduit for drill vibration to the inner ear?

CONCLUSION

In the presence of simulated congenital aural atresia with fixation of the ossicular chain to the surrounding bone, access to the chain for placement of a middle ear prosthesis using the rotating burr is not associated with significant stapes movement that would cause vibrational trauma to the cochlea.

OBJECTIVES

To determine the energy transmitted to the cochlea while drilling the mastoid in an ear with simulated congenital aural atresia and fixation of the ossicular chain to the surrounding bone.

METHODS

Eight human cadaveric temporal bones were used. Cement was placed in the external auditory canal and on the incudomalleolar joint and surrounding epitympanum, to simulate congenital aural atresia and ossicular fixation, respectively. Stapes vibration was measured with the Laser Doppler Vibrometer using acoustic then drill stimulation by touching the wall of the epitympanum with a running burr.

RESULTS

Using acoustic stimulation, all bones showed frequency-specific reduction of stapes motion of up to 17 dB with fixation of the ossicular chain to the surrounding bone. There was no measurable stapes motion when the external auditory canal was filled with cement. On drill stimulation, there was no difference in stapes velocity between the normal bone and the bone with simulated congenital aural atresia.