J. Eric Lupo

Electrocochleographic and mechanical assessment of round window stimulation with an active middle ear prosthesis.

Mechanical stimulation of the round window (RW) with an active middle ear prosthesis (AMEP) has shown functional benefit in clinical reports in patients with mixed hearing loss (MHL). Further objective physiological data on the efficacy of RW stimulation is needed, however, to demonstrate that RW stimulation with an AMEP can generate input to the inner ear comparable to acoustic input. Cochlear microphonic (CM) and mechanical (stapes velocity) responses to sinusoidal stimuli were measured by electrode and laser Doppler vibrometry in eight chinchillas in response to normal acoustic stimulation via sealed calibrated insert earphones and to AMEP stimulation (Otologics MET, Boulder, CO, USA) of the RW with and without lateral ossicular chain disarticulation. CM thresholds for acoustic stimulation were frequency dependent and ranged from 16 to 50 dB SPL. CM thresholds measured with RW stimulation ranged from -14 to 35 dBmV with an intact middle ear chain and from -7 to 36 dBmV after lateral ossicular chain disarticulation. Acoustically, stapes velocity maxima was observed at approximately 700 Hz and minima at approximately 2.65 kHz. With application of the AMEP to the RW, peak stapes velocity was observed at 2-3 kHz. The equivalent ear canal sound pressure level (L(E)(max)dB SPL) evoked by RW stimulation with the AMEP was 60-105 dB SPL for the intact middle ear and 70-100 dB SPL after ossicular chain disarticulation. Stimulating the inner ear through the RW with an AMEP produces evoked responses (CM) comparable to normal acoustic input. When adjusted for threshold (due to unit differences, dB SPL or dB mV), the sensitivity of the CM (slope) for acoustic was comparable to sensitivities obtained by AMEP stimulation of the RW. Mechanical stimulation of the RW with an AMEP produces cochlear responses (CMs) and stapes velocities that are functionally equivalent to acoustic stimulation.

Physiological Assessment of Active Middle Ear Implant Coupling to the Round Window in Chinchilla lanigera

Objective. To study the effects of various active middle ear implant loading parameters on round window stimulation in an animal model. Study Design. Physiological measurements of the cochlear microphonic and stapes velocity were made from active middle ear implant–generated sinusoidal stimuli with controlled changes in loading parameters. Setting. Prospective study at an academic research institution. Subjects and Methods. Cochlear microphonic and stapes velocities (H EV ) were measured in 6 study subjects (Chinchilla lanigera) in response to active middle ear implant (Otologics MET, Boulder, Colorado) round window stimulation with assessment of effects of varying parameters of loading pressure, interposed connective tissue, and angle of stimulation with respect to the round window membrane. Results. The measured performance variabilities in repeated applications of the active middle ear implant to the round window were 2.5 dB and 5.0 dB for H EV and cochlear microphonic thresholds, respectively. Loading pressure applied to the round window (51-574 dynes) and angle of approach (±30° with respect to coronal plane) did not have a significant effect on cochlear microphonic thresholds or H EV . Significant improvements in cochlear microphonic thresholds and H EV were observed for interposed connective tissue regardless of tissue type. Conclusion. Variability in performance due to repeated couplings of the active middle ear implant to the round window is small and reproducible. Interposition of connective tissue significantly improves vibration energy transfer to the cochlea. Neither changes in loading pressure nor angle of stimulation of the round window affected active middle ear implant performance.

Prospective electrophysiologic findings of round window stimulation in a model of experimentally induced stapes fixation.

Hypothesis: Mechanical stimulation of the round window (RW) with an active middle ear implant (AMEI) with and without experimentally induced stapes fixation (SF) results in equivalent electrophysiologic measures of cochlear microphonic (CM), compound action potential (CAP), and auditory brainstem response (ABR). Background: Where normal oval window functionality is mitigated, the RW provides a pathway to mechanically stimulate the inner ear. Methods: Measurements of the CM, CAP, and ABR were made in 5 ears of 4 chinchillas with acoustic stimulation and with application of the AMEI to the RW with and without experimentally induced SF using pure-tone stimuli (0.25-20 kHz) presented at differing intensities (−20 to 80 dB SPL vs. 0.01 mV to 3.16 V). Results: Morphologies of the CM, CAP, and ABR were similar between acoustic and RW stimulation with and without SF. Stapes fixation increased CM thresholds relative to RW stimulation without fixation by a frequency-dependent 4- to 13-dB mV (mean, 7.9 ± 3.2 dB mV). Although the thresholds changed with SF, CM sensitivities and amplitude dynamic range were identical to normal. The CAP in all conditions demonstrated equivalent decreasing amplitudes and increasing latency with decreasing intensity (decibel sound pressure level versus decibel millivolt). Stapes fixation increased the CAP thresholds at all frequencies, ranging from 9 to 24 dB mV (mean, 17.7 ± 4.9 dB mV). Auditory brainstem response waveforms were preserved across experimental conditions. Conclusion: Mechanical stimulation of the RW in an animal model of SF generates functionally similar inputs to the cochlea as normal acoustic and RW mechanical inputs but with increased thresholds. With further study, AMEIs may provide a surgical option for correction of otosclerosis and ossicular chain disruption.

Vibromechanical Assessment of Active Middle Ear Implant Stimulation in Simulated Middle Ear Effusion: A Temporal Bone Study

Hypothesis Active middle ear implant (AMEI) generated vibromechanical stimulation of the ossicular chain (ossicular chain vibroplasty [OCV]) or the round window (round window vibroplasty [RWV]) is not significantly affected by simulated middle ear effusion in a human temporal bone model. Background OCV and RWV may be employed for sensorineural, mixed, and conductive hearing losses. Although middle ear effusions may be encountered across patient populations, little is known about how effusions may affect AMEI vibromechanical efficiency. Methods Laser Doppler vibrometry of stapes velocities (SVs) were performed in a human temporal bone model of simulated effusion (N = 5). Baseline measurements to acoustic sinusoidal stimuli, OCV, and RWV (0.25–8 kHz) were made without effusion. The measurements were repeated with simulated middle ear effusion and compared with baseline measurements. Data were analyzed across 3 frequency bands: low (0.25–1 kHz), medium (1–3 kHz), and high (3–8 kHz). Results Acoustic stimulation with simulated middle ear effusion resulted in a significant (p < 0.001) frequency-dependent attenuation of SVs of 4, 10, and 7 dB (low, medium, and high ranges, respectively). OCV in simulated effusion resulted in attenuated SVs of 1, 5, and 14 dB (low, medium, and high) compared to without effusion; however, this attenuation was not significant (p = 0.07). Interestingly, in the setting of RWV, simulated effusion resulted in significantly (p = 0.001) increased SVs of 16, 11, and 8 dB (low, medium, and high). A 3-dB variance in AMEI efficiency was observed in repeated measurements in a single temporal bone. Conclusion The efficiency of OCV was not significantly affected by the presence of a middle ear effusion. Improved efficiency, however, was observed with RWV.

Hearing Outcomes after Revision Stapedectomy Managed with Total Ossicular Reconstruction Prostheses

Objectives: (1) Describe the use of total ossicular reconstruction prostheses (TORP) during revision stapedectomy in the setting of advanced incus erosion. (2) Analyze the short- and medium-term audiometric results of TORP for revision stapedectomy. Methods: A retrospective case review at a tertiary neurotological referral center was conducted of nineteen cases of revision stapedectomy where TORP reconstruction was performed due to advanced incus erosion. Pre- and postoperative bone conduction (BC-PTA) and air conduction (AC-PTA) pure tone averages (0.5, 1, 2, 3 kHz) including high tone bone conduction (1, 2, 3 kHz), air-bone gap (ABG), and speech discrimination scores (SDS) were measured. Short-term (3 weeks) and medium-term (median, 12 months) hearing outcomes were measured. Results: Among 19 ears undergoing revision stapedectomy managed with TORP reconstruction, the average number of previous revision attempts was 1.2 (SD, 2; range, 1-6). The preoperative BC-PTA was 32.1 dB preoperatively while the preoperative AC-PTA was 65.3 dB. The mean postoperative ABG significantly decreased to 16.6 dB (SD, 13.68; range, −2.5 to 46.3 dB, P < .003) with mean follow-up of 15 months (SD, 18.8; range, 0.75-54 months). A nonsignificant mean high tone BC-PTA decrement of 3.8 dB (SD = 5.9, range −8.33 to 18.33 dB, P = .427) was observed including one ear with no responses postoperatively. No further revisions were noted in follow-up. Conclusions: Total ossicular reconstruction in the setting of previous revision stapedectomy with limited incudovestibular reconstructive options may lead to favorable hearing outcomes but carries an increased risk of sensorineural hearing loss.