Introduction: The aims of this study included: (a) to develop a method of direct acoustic bone conduction (BC) stimulation applied directly to the otic capsule, (b) to investigate the effect of different stimulation sites on the promontory displacement amplitude, and (c) to find the best stimulation site (among 2 located directly on the otic capsule and 1 standard site approved for clinical use) that provides the greatest transmission of vibratory energy. Methods: Measurements were performed on 9 cadaveric whole human heads. A commercial scanning laser Doppler vibrometer was used. The promontory displacement was recorded in response to BC stimulation delivered by an implant at 3 sites: BC1 on the squamous part of the temporal bone, BC2 on the ampulla of the lateral semicircular canal, and BC3 between the semicircular canals. The displacement of the promontory was analyzed in detail. Results: The results show that BC1 caused an overall smaller promontory displacement than both sites BC2 and 3. BC3 stimulation is more efficient than that at BC2. Conclusions: BC is an effective method of acoustic stimulus delivery into the inner ear, with the effectiveness increasing when approaching closer to the cochlea. Placing the implant directly on the labyrinth and thus applying vibrations directly to the otic capsule is possible and very effective as proved in this study. The results are encouraging and represent the potential of new stimulation sites that could be introduced in the field of BC hearing rehabilitation as the possible future locations for implantable BC hearing devices.

Objectives: The aim of this study was to investigate the following: (1) the vibration pattern of the round window (RW) membrane in human cadavers during air (AC) and bone conduction (BC) stimulation at different excitation sites; (2) the effect of the stimulation on the fluid volume displacement (VD) at the RW and compare the VD between BC and AC stimulation procedures; (3) the effectiveness of cochlear stimulation by the bone implant at different excitation sites. Design: The RW membrane vibrations were measured by using a commercial scanning laser Doppler vibrometer. The RW vibration amplitude was recorded at 69 measurement points evenly distributed in the measurement field covering the entire surface of the RW membrane and a part of the surrounding bony surface. RW vibration was induced first with AC and then with BC stimulation through an implant positioned at two sites. The first site was on the skull surface at the squamous part of the temporal bone (implant no. 1), a place typical for bone-anchored hearing aids. The second site was close to the cochlea at the bone forming the ampulla of the lateral semicircular canal (implant no. 2). The displacement amplitude (dP) of the point P on the promontory was determined and used to calculate the relative displacement (drRW) of points on the RW membrane, drRW = dRW − dP. VD parameter was used to analyze the effectiveness of cochlear stimulation by the bone implant screwed at different excitation sites. Results: RW membrane displacement amplitude of the central part of the RW was similar for AC and BC implant no. 1 stimulation, and for BC implant no. 2 much larger for frequency range >1 kHz. BC implant no. 2 causes a larger displacement amplitude of peripheral parts of the RW and the promontory than AC and BC implant no. 1, and BC implant no. 1 causes larger than AC stimulation. The effect of BC stimulation exceeds that of AC with identical intensity, and that the closer BC stimulation to the otic capsule, the more effective this stimulation is. A significant decrease in the value of VD at the RW is observed for frequencies >2 kHz for both AC and BC stimulation with BC at both locations of the titanium implant placement. For frequencies >1 kHz, BC implant no. 2 leads to a significantly larger VD at the RW compared to BC implant no. 1. Thus, the closer to the otic capsule the BC stimulation is located, the more effective it is. Conclusions: Experimental conditions allow for an effective acoustic stimulation of the inner ear by an implant screwed to the osseous otic capsule. The mechanical effect of BC stimulation with a titanium implant placed in the bone of the ampulla of the lateral semicircular canal significantly exceeds the effect of an identical stimulation with an implant placed in the temporal squama at a conventional site for an implant anchored in the bone. The developed research method requires the implementation on a larger number of temporal bones in order to obtain data concerning interindividual variability of the observed mechanical phenomena.

We present a surgical technique of closed tympanoplasty for chronic otitis, together with an intraoperative functional evaluation system with the OssiMon LAIOM software. The technique can be used in one or two steps for an intraoperative evaluation of the functional effect during ear operation. Using OssiMon LAIOM, we were able to simultaneously measure the auditory steady-state response (ASSR), as well as to perform laser dopler vibrometry (LDV). For electrophysiologic measurements, OssiMon LAIOM uses the Intelligent Hearing System platform, and the Polytec single-point laser to evaluate the ossicular mobility. The measurements can be conducted using both methods at the same time or separately, applying each method independently. The OssiMon LAIOM software records the ASSR response intraoperatively and marks it automatically on the audiogram with the preoperative hearing level. The ossicular vibration level is determined based on the measured LDV response. To the best of our knowledge, OssiMon LAIOM is the first solution allowing to objectively measure the effectiveness of tympanoplasty using two methods simultaneously, i.e. ASSR and LDV. The system could be widely applied in the functional evaluation of the middle ear and in clinical practice.

Objectives: Aim was to investigate the innovative method of direct acoustic bone conduction (BC) stimulation applied directly to the otic capsule and measured intraoperatively by promontory displacement in living humans. The objective was to find the best stimulation site that provides the greatest transmission of vibratory energy in a living human and compare it with the results previously obtained in cadavers. Design: The measurements were performed in 4 adult patients referred to our department for vestibular schwannoma removal via translabyrinthine approach. The measurements were performed in the operated site. The cadaver data were obtained in our previous study and here they are reanalyzed for comparison. Promontory displacement was measured using a commercial scanning laser Doppler vibrometer. The laser Doppler vibrometer points located on the promontory were used to analyze the promontory displacement amplitude. Cochlear stimulation was induced with BC stimulation through an implant positioned at three sites. The first site was on the skull surface at the squamous part of the temporal bone (BC No. 1), the second at the bone forming the ampulla of the lateral semicircular canal (BC No. 2), and the third between the superior and lateral semicircular canals (BC No. 3). BC No. 2 and BC No. 3 were located directly on the otic capsule. Four frequencies in total were tested (500, 1000, 2000, and 4000 Hz), one at a time. Results: In patients, the detailed analysis of promontory displacement amplitudes revealed the BC No. 1 magnitude to be the smallest and significantly different from BC No. 2 and No. 3 at all measured frequencies. Transmission of vibratory energy at BC No. 2 and BC No. 3 was the most effective and similar with a small and insignificant difference at 500, 1000, and 4000 Hz, and a significant difference at 2000 Hz. The results observed in cadavers were similar to those in living humans. However, a few differences were observed when comparing patients and cadavers. Small and insignificant differences were found for BC No. 1. Almost the same results were obtained for BC No. 2 and BC No. 3 in cadavers as in living humans, with only BC No. 3 measurements results at 500 Hz at the limit of statistical significance, with no other significant differences observed. Conclusions: The results of this study indicate that the promontory vibration amplitude increases when the BC stimulation location approaches the cochlea. BC No. 1 stimulation located on the squama caused overall smaller displacement than both BC No. 2 and No. 3 screwed to the ampulla of the lateral semicircular canal and to the midpoint between the semicircular canals, respectively. In our opinion, the results of BC stimulation applied directly to the otic capsule present a potential new stimulation site that could be introduced in the field of BC hearing rehabilitation.