title: Third-window vibroplasty with an active middle ear implant: assessment of physiologic responses in a model of stapes fixation in Chinchilla lanigera.
abstract: OBJECTIVE
  Mechanical stimulation through a cochlear third window into the scala tympani in a chinchilla model with normal and fixed stapes can generate cochlear responses equivalent to acoustic stimuli.
  
  
  BACKGROUND
  Cochlear stimulation via the round window (RW) using active middle ear implants (AMEIs) can produce physiologic responses similar to acoustic stimulation including in a model of stapes fixation. However, pathologic conditions, such as advanced otosclerosis, can preclude delivery of sound energy to the cochlea through the oval window and/or the RW.
  
  
  METHODS
  Cochlear microphonic (CM) and laser Doppler vibrometer measurements of stapes and RW velocities were performed in 6 ears of 4 chinchillas. Baseline measurements to acoustic sinusoidal stimuli (0.25-8 kHz) were made. Measurements were repeated with an AMEI driving the RW or a third window to the scala tympani before and after stapes fixation.
  
  
  RESULTS
  AMEI stimulation of the third window produced CM waveforms with morphologies similar to acoustic stimuli. CM thresholds with RW and third-window stimulation were frequency dependent but ranged from 0.25 to 10 and 0.5 to 40 mV, respectively. Stapes fixation, confirmed by laser Doppler vibrometer measurements, resulted in a significant frequency dependent impairment in CM thresholds up to 13 dB (at <3 kHz) for RW stimulation and a nonsignificant frequency-dependent improvement of up to 10 dB (at >3 kHz) via third-window stimulation.
  
  
  CONCLUSIONS
  AMEI mechanical stimulation through a third window into the scala tympani produces physiologic responses nearly identical to acoustic stimulation including in a model of stapes fixation with decreased efficiency.
authors.affiliation: Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado 80045, USA. james.lupo@ucdenver.edu
authors.forename: J Eric
authors.initials: JE
authors.lastname: Lupo
authors.forename: Kanthaiah
authors.initials: K
authors.lastname: Koka
authors.forename: Herman A
authors.initials: HA
authors.lastname: Jenkins
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Tollin
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001309:Auditory Threshold; D002138:Calibration; D002682:Chinchilla / Q000502:physiology*; D003051:Cochlea / Q000502:physiology / Q000601:surgery; D003054:Cochlear Implants; D003055:Cochlear Microphonic Potentials; D004432:Ear, Middle / Q000601:surgery*; D017078:Laser-Doppler Flowmetry; D010040:Otosclerosis / Q000601:surgery; D012405:Round Window, Ear / Q000502:physiology; D012533:Scala Tympani / Q000502:physiology; D013199:Stapes / Q000502:physiology*; D014732:Vibration