Abstract: The cochlea is normally driven with "forward" stimulation, in which sound is introduced to the ear canal. Alternatively, the cochlea can be stimulated at the round window (RW) using an actuator. During RW "reverse" stimulation, the acoustic flow starting at the RW does not necessarily take the same path as during forward stimulation. To understand the differences between forward and reverse stimulation, we measured ear-canal pressure, stapes velocity, RW velocity, and intracochlear pressures in scala vestibuli (SV) and scala tympani (ST) of fresh human temporal bones. During forward stimulation, the cochlear drive (differential pressure across the partition) results from the large difference in magnitude between the pressures of SV and ST, which occurs due to the high compliance of the RW. During reverse stimulation, the relatively high impedance of the middle ear causes the pressures of SV and ST to have similar magnitudes, and the differential pressure results primarily from the difference in phase of the pressures. Furthermore, the sound path differs between forward and reverse stimulation, such that motion through a third window is more significant during reverse stimulation. Additionally, we determined that although stapes velocity is a good estimate of cochlear drive during forward stimulation, it is not a good measure during reverse stimulation. This article is part of a Special Issue entitled "MEMRO 2012".
Abstract: Bone-anchored hearing implants (BAHI) are routinely used to alleviate the effects of the acoustic head shadow in single-sided sensorineural deafness (SSD). In this study, the influence of the directional microphone setting and the maximum power output of the BAHI sound processor on speech understanding in noise in a laboratory setting were investigated. Eight adult BAHI users with SSD participated in this pilot study. Speech understanding in noise was measured using a new Slovak speech-in-noise test in two different spatial settings, either with noise coming from the front and noise from the side of the BAHI (S90N0) or vice versa (S0N90). In both spatial settings, speech understanding was measured without a BAHI, with a Baha BP100 in omnidirectional mode, with a BP100 in directional mode, with a BP110 power in omnidirectional and with a BP110 power in directional mode. In spatial setting S90N0, speech understanding in noise with either sound processor and in either directional mode was improved by 2.2-2.8 dB (p = 0.004-0.016). In spatial setting S0N90, speech understanding in noise was reduced by either BAHI, but was significantly better by 1.0-1.8 dB, if the directional microphone system was activated (p = 0.046), when compared to the omnidirectional setting. With the limited number of subjects in this study, no statistically significant differences were found between the two sound processors.
Abstract: PURPOSE : For the facilitation of minimally invasive robotically performed direct cochlea access (DCA) procedure, a surgical planning tool which enables the surgeon to define landmarks for patient-to-image registration, identify the necessary anatomical structures and define a safe DCA trajectory using patient image data (typically computed tomography (CT) or cone beam CT) is required. To this end, a dedicated end-to-end software planning system for the planning of DCA procedures that addresses current deficiencies has been developed. METHODS : Â Â Â Efficient and robust anatomical segmentation is achieved through the implementation of semiautomatic algorithms; high-accuracy patient-to-image registration is achieved via an automated model-based fiducial detection algorithm and functionality for the interactive definition of a safe drilling trajectory based on case-specific drill positioning uncertainty calculations was developed. RESULTS : Â Â Â The accuracy and safety of the presented software tool were validated during the conduction of eight DCA procedures performed on cadaver heads. The plan for each ear was completed in less than 20Â min, and no damage to vital structures occurred during the procedures. The integrated fiducial detection functionality enabled final positioning accuracies of [Formula: see text]Â mm. CONCLUSIONS : Â Â Â Results of this study demonstrated that the proposed software system could aid in the safe planning of a DCA tunnel within an acceptable time.
Abstract: OBJECTIVE:
To compare speech understanding of the BAHA BP110 and BAHA Intenso sound processors.
STUDY DESIGN:
Prospective experimental study.
SETTING:
Tertiary referral center.
PATIENTS:
Twenty experienced user of osseointegrated auditory implants with conductive or mixed hearing loss.
INTERVENTIONS:
In a first session, half of the participants were fitted with an Intenso, the other half with a BP110. After 1 month of use, aided speech understanding in quiet and in noise was measured, and the other test processor was fitted. One month later, speech understanding with the second sound processor was assessed.
MAIN OUTCOME MEASURES:
Speech understanding in quiet and in noise, with noise arriving either from the front, the rear, or the side of the user with the osseointegrated bone conductor.
RESULTS:
Significant improvements were found for both processors for speech understanding in quiet (+9.6 to +34.8 percent points; p = 0.02 to 0.001) and in noise (+6.2 to +13.8 dB, p < 0.001). No significant differences were found between the 2 devices for speech in quiet. For noise from the rear, subjects were able to understand speech at signal-to-noise ratios which were lower (less favorable) by -5.1 dB (p < 0.001) when compared with the Intenso.
CONCLUSION:
Speech understanding is substantially improved by both devices, with no significant differences between the sound processors in quiet. In noise, speech understanding is significantly better with the BP110 when compared to the Intenso for noise from the rear.
Abstract: OBJECTIVE: To investigate the effect of low-frequency attenuation of Bone-Anchored Hearing Aids (Bahas) in users with single-sided sensorineural deafness (SSD). The underlying notion is that low-frequency sounds up to approximately 1500 Hz reach the contralateral ear without significant attenuation and that Bahas tend to show more distortion at lower frequencies. Furthermore, to transmit low frequencies, higher moving masses are needed when compared with high frequencies.
DESIGN: A prospective study with 10 adults, experienced Baha Divino users with SSD. Speech understanding in noise was measured without Baha and with Baha, with three different settings of low-frequency attenuation, namely up to 270, 630, and 1500 Hz. Tests were performed in two different spatial arrangements. In one placement, speech was emitted from a loudspeaker on the side of the Baha ear and noise from a loudspeaker in front of the listener (S90N0). In the other placement, the sound sources were switched (S0N90). Participants rated the subjective sound quality of the two most extreme Baha settings using analog visual scales after a short acclimatization time of 15 mins.
RESULTS: In setting S90N0, the use of a Baha improved speech understanding in noise significantly (average improvement 2.8 to 3.1 dB, p = 0.006). These improvements did not vary significantly with the chosen low-frequency attenuation. In setting S0N90, a smaller but detrimental effect of the Baha was found (-0.9 to -1.7 dB, p = 0.006 to 0.03). This detrimental effect was significantly smaller at the highest cutoff frequency of 1500 Hz than at 270 Hz (p = 0.013). At the cutoff frequency of 270 Hz, loudness and reverberation were judged higher than at 1500 Hz. There was no significant difference in brightness, softness, clarity, or fullness.
CONCLUSION: High cutoff levels of up to 1500 Hz for low-frequency signals do not compromise the benefit of Baha in SSD for noise arriving from the front and speech presented on the side of the Baha. If noise is presented from the side of the Baha, the detrimental effect on speech understanding can be reduced by higher cutoff frequencies. If frequencies <1500 Hz do not need to be transmitted, lower moving masses of the Baha are required and smaller devices for patients with SSD may be possible.
Abstract: A new hearing therapy based on direct acoustic cochlear stimulation was developed for the treatment of severe to profound mixed hearing loss. The device efficacy was validated in an initial clinical trial with four patients. This semi-implantable investigational device consists of an externally worn audio processor, a percutaneous connector, and an implantable microactuator. The actuator is placed in the mastoid bone, right behind the external auditory canal. It generates vibrations that are directly coupled to the inner ear fluids and that, therefore, bypass the external and the middle ear. The system is able to provide an equivalent sound pressure level of 125 dB over the frequency range between 125 and 8000Â Hz. The hermetically sealed actuator is designed to provide maximal output power by keeping its dimensions small enough to enable implantation. A network model is used to simulate the dynamic characteristics of the actuator to adjust its transfer function to the characteristics of the middle ear. The geometry of the different actuator components is optimized using finite-element modeling.
Abstract: Objective:To present the auditory implant manipulator, a navigation-controlled mechanical and electronic system which enables minimally invasive ('keyhole') transmastoid access to the tympanic cavity.Materials and methods:The auditory implant manipulator is a miniaturised robotic system with five axes of movement and an integrated drill. It can be mounted on the operating table. We evaluated the surgical work field provided by the system, and the work sequence involved, using an anatomical whole head specimen.Results:The work field provided by the auditory implant manipulator is considerably greater than required for conventional mastoidectomy. The work sequence for a keyhole procedure included pre-operative planning, arrangement of equipment, the procedure itself and post-operative analysis.Conclusion:Although system improvements are necessary, our preliminary results indicate that the auditory implant manipulator has the potential to perform keyhole insertion of implantable hearing devices.
Abstract: OBJECTIVES: With the placement of a floating mass transducer (FMT) at the round window, a new approach of coupling an implantable hearing system to the cochlea has been introduced. The aim of the present experimental study is to examine the influence of different ways of FMT placement at the round window on the vibration energy transfer to the cochlea.
MATERIAL AND METHODS: Experiments were performed on 8 ears of human whole head specimens. A mastoidectomy and facial recess approach were performed to access the middle ear structures. Seven different conditions were compared, that is, a perpendicular or 90-degree rotated position of the FMT in the round window niche, overlaid or underlaid with connective tissue or with tight fixation and disrupted ossicular chain. The FMT was stimulated electrically and the movements at the FMT, the stapes head, and the promontory were measured using laser Doppler vibrometry.
RESULTS: Vibration transmission to the cochlear fluids was best with the FMT placed perpendicular to the round window membrane and underlaid with connective tissue. The energy transfer to the inner ear was up to 45 dB higher compared with tight fixation condition, where the poorest energy transfer was found. Underlaying the FMT with connective tissue improved energy transfer even for a suboptimal orientation of the FMT.
CONCLUSION: The way of coupling of the FMT to the round window has a substantial influence on the vibration transmission. Energy transfer to the inner ear is highest with the FMT placed in the round window and underlaid with tissue.
Abstract: The round window placement of a floating mass transducer (FMT) is a new approach for coupling an implantable hearing system to the cochlea. We evaluated the vibration transfer to the cochlear fluids of an FMT placed at the round window (rwFMT) with special attention to the role of bone conduction. A posterior tympanotomy was performed on eleven ears of seven human whole head specimens. Several rwFMT setups were examined using laser Doppler vibrometry measurements at the stapes and the promontory. In three ears, the vibrations of a bone anchored hearing aid (BAHA) and an FMT fixed to the promontory (pFMT) were compared to explore the role of bone conduction. Vibration transmission to the measuring point at the stapes was best when the rwFMT was perpendicularly placed in the round window and underlayed with connective tissue. Fixation of the rwFMT to the round window exhibited significantly lower vibration transmission. Although measurable, bone conduction from the pFMT was much lower than that of the BAHA. Our results suggest that the rwFMT does not act as a small bone anchored hearing aid, but instead, acts as a direct vibratory stimulator of the round window membrane.
Abstract: Computer-aided microscopic surgery of the lateral skull base is a rare intervention in daily practice. It is often a delicate and difficult minimally invasive intervention, since orientation between the petrous bone and the petrous bone apex is often challenging. In the case of aural atresia or tumors the normal anatomical landmarks are often absent, making orientation more difficult. Navigation support, together with imaging techniques such as CT, MR and angiography, enable the surgeon in such cases to perform the operation more accurately and, in some cases, also in a shorter time. However, there are no internationally standardised indications for navigated surgery on the lateral skull base. Miniaturised robotic systems are still in the initial validation phase.
Abstract: OBJECTIVE: To investigate correlations between preoperative hearing thresholds and postoperative aided thresholds and speech understanding of users of Bone-anchored Hearing Aids (BAHA). Such correlations may be useful to estimate the postoperative outcome with BAHA from preoperative data.
STUDY DESIGN: Retrospective case review.
SETTING: Tertiary referral center.
PATIENTS : Ninety-two adult unilaterally implanted BAHA users in 3 groups: (A) 24 subjects with a unilateral conductive hearing loss, (B) 38 subjects with a bilateral conductive hearing loss, and (C) 30 subjects with single-sided deafness.
INTERVENTIONS: Preoperative air-conduction and bone-conduction thresholds and 3-month postoperative aided and unaided sound-field thresholds as well as speech understanding using German 2-digit numbers and monosyllabic words were measured and analyzed.
MAIN OUTCOME MEASURES: Correlation between preoperative air-conduction and bone-conduction thresholds of the better and of the poorer ear and postoperative aided thresholds as well as correlations between gain in sound-field threshold and gain in speech understanding.
RESULTS: Aided postoperative sound-field thresholds correlate best with BC threshold of the better ear (correlation coefficients, r2 = 0.237 to 0.419, p = 0.0006 to 0.0064, depending on the group of subjects). Improvements in sound-field threshold correspond to improvements in speech understanding.
CONCLUSION: When estimating expected postoperative aided sound-field thresholds of BAHA users from preoperative hearing thresholds, the BC threshold of the better ear should be used. For the patient groups considered, speech understanding in quiet can be estimated from the improvement in sound-field thresholds.
Abstract: A new implantable hearing system, the direct acoustic cochlear stimulator (DACS) is presented. This system is based on the principle of a power-driven stapes prosthesis and intended for the treatment of severe mixed hearing loss due to advanced otosclerosis. It consists of an implantable electromagnetic transducer, which transfers acoustic energy directly to the inner ear, and an audio processor worn externally behind the implanted ear. The device is implanted using a specially developed retromeatal microsurgical approach. After removal of the stapes, a conventional stapes prosthesis is attached to the transducer and placed in the oval window to allow direct acoustical coupling to the perilymph of the inner ear. In order to restore the natural sound transmission of the ossicular chain, a second stapes prosthesis is placed in parallel to the first one into the oval window and attached to the patient's own incus, as in a conventional stapedectomy. Four patients were implanted with an investigational DACS device. The hearing threshold of the implanted ears before implantation ranged from 78 to 101 dB (air conduction, pure tone average, 0.5-4 kHz) with air-bone gaps of 33-44 dB in the same frequency range. Postoperatively, substantial improvements in sound field thresholds, speech intelligibility as well as in the subjective assessment of everyday situations were found in all patients. Two years after the implantations, monosyllabic word recognition scores in quiet at 75 dB improved by 45-100 percent points when using the DACS. Furthermore, hearing thresholds were already improved by the second stapes prosthesis alone by 14-28 dB (pure tone average 0.5-4 kHz, DACS switched off). No device-related serious medical complications occurred and all patients have continued to use their device on a daily basis for over 2 years.
Abstract: A life-size mechanical middle ear model and human temporal bones were used to evaluate three different middle ear transducers for implantable hearing aids: the driving rod transducer (DRT), the floating mass transducer (FMT) or vibrant sound bridge, and the contactless transducer (CLT). Results of the experiments with the mechanical model were within the range of the results for human temporal bones. However, results with the mechanical model showed better reproducibility. The handling of the mechanical model was considerably simpler and less time-consuming. Systematic variations of mounting parameters showed that the angle of the rod has virtually no effect on the output of the DRT, the mass loading on the cable of the FMT has a larger impact on the output than does the tightness of crimping, and the output level of the CLT can be increased by 10 dB by optimizing the mounting parameters.
Abstract: OBJECTIVE: To generate anatomical data on the human middle ear and adjacent structures to serve as a base for the development and optimization of new implantable hearing aid transducers. Implantable middle ear hearing aid transducers, i.e. the equivalent to the loudspeaker in conventional hearing aids, should ideally fit into the majority of adult middle ears and should utilize the limited space optimally to achieve sufficiently high maximal output levels. For several designs, more anatomical data are needed.
METHODS: Twenty temporal bones of 10 formalin-fixed adult human heads were scanned by a computed tomography system (CT) using a slide thickness of 0.63 mm. Twelve landmarks were defined and 24 different distances were calculated for each temporal bone.
RESULTS: A statistical description of 24 distances in the adult human middle ear which may limit or influence the design of middle ear transducers is presented. Significant inter-individual differences but no significant differences for gender, side, age or degree of pneumatization of the mastoid were found. Distances, which were not analyzed for the first time in this study, were found to be in good agreement with the results of earlier studies.
CONCLUSION: A data set describing the adult human middle ear anatomy quantitatively from the point of view of designers of new implantable hearing aid transducers has been generated. In principle, the method employed in this study using standard CT scans could also be used preoperatively to rule out exclusion criteria.
Abstract: A simple, contactless electromagnetic transducer design for implantable hearing aids is investigated. It consists of a coil and a permanent magnet, both of which are intended for implantation in the middle ear. The transducer is modeled and optimized using computer simulations, followed by experimental verification. It is shown that the proposed transducer design can, because of its size and geometry, allow implantation through the external auditory canal, and provide a sufficiently high acoustic output corresponding to approximately 120 dB sound pressure level. It can be optimized to be tolerant of radial displacements between coil and magnet of up to 1 mm.
Abstract: This paper presents an automated solution for precise detection of fiducial screws from three-dimensional (3D) Computerized Tomography (CT)/Digital Volume Tomography (DVT) data for image-guided ENT surgery. Unlike previously published solutions, we regard the detection of the fiducial screws from the CT/DVT volume data as a pose estimation problem. We thus developed a model-based solution. Starting from a user-supplied initialization, our solution detects the fiducial screws by iteratively matching a computer aided design (CAD) model of the fiducial screw to features extracted from the CT/DVT data. We validated our solution on one conventional CT dataset and on five DVT volume datasets, resulting in a total detection of 24 fiducial screws. Our experimental results indicate that the proposed solution achieves much higher reproducibility and precision than the manual detection. Further comparison shows that the proposed solution produces better results on the DVT dataset than on the conventional CT dataset.
Abstract: The delicate anatomy of the ear require surgeons to use great care when operating on its internal structures. One example for such an intervention is the stapedectomy, where a small crook shaped piston is placed in the oval window of the cochlea and connected to the incus through crimping thus bypassing the diseased stapes. Performing the crimp process with the correct force is necessary since loose crimps poorly transmit sound whereas tight crimps will eventually result in necrosis of the incus. Clinically, demand is high to reproducibly conduct the crimp process through a precise force measurement. For this reason, we have developed a fiber Bragg grating (FBG) integrated microforceps for use in such interventions. This device was calibrated, and tested in cadaver preparations. With this instrument we were able to measure for the first time forces involved in crimping a stapes prosthesis to the incus. We also discuss a method of attaching and actuating such forceps in conjunction with a robot currently under development in our group. Each component of this system can be used separately or combined to improve surgical accuracy, confidence and outcome.
Abstract: In this paper, we present a novel robotic assistant dedicated to otologic surgery for an implantable hearing aid system, which is a procedure involving drilling into the lateral skull of the patient. This compact and flexible miniature robot is designed so as to fulfill the requirements of precise bone drillings for hearing aid implantation. It is built from an original five degree-of-freedom (DOF) parallel structure with a motorized end-effector, particularly well suited to otological surgical procedure. The specification, the design and the analysis of the workspace are detailed. A preliminary accuracy evaluation is presented. A rotational accuracy of 0.6 ± 0.6° and a translational accuracy of 1.4 ± 0.5 mm were found.
Abstract: The adequate treatment of the patients with moderate to severe mixed hearing loss (MHL) is not sufficiently possible with conventional hearing aids. These patients have enough cochlear reserve, but the additional middle ear disorder limits the usage of conventional hearing aids (gain limitation and distortion). The second possibility for such patients would be the bone conduction hearing aids, which indicate an insufficient gain for moderate to severe MHL. On the other hand because of good cochlear reserve there isnât an indication for cochlear implantation. Therefore there is no optimal way to give an adequate gain to patients with moderate to severe MHL.
The new improved DACS-system (Direct Acoustic Cochlear Stimulation) realizes a direct transfer to the inner ear. In this way the conductive disorders of middle ear does not have any influence on the sound transfer. After an introduction of the functional principle of the system the pre- and postoperative audiological results of 4 implanted patients will be presented in this paper. The one year post operative results indicate a functional gain of about 50 dB HL and an SRT (Speech Reception Threshold) improvement of about 40 dB SPL.
Abstract: A new hearing therapy called direct acoustical cochlear stimulation (DACS) was developed and validated in a first clinical trial with four patients. The key component of this therapy based on an implantable hearing device is a micro-actuator that is implanted in the mastoid right behind the external auditory canal of a patient. It generates vibrations that are directly coupled to the inner ear fluids and bypass therefore the outer and the middle ear. This allows treating severe to profound mixed hearing loss. The hermetically sealed actuator was designed to provide maximal output power by keeping the overall size small enough to be placed in the mastoid. An analytical model was used to simulate the dynamic characteristics of the actuator in order to adjust them to the transfer function of a human middle ear. The geometric parameters of the actuator were optimized using finite element modeling.
Abstract: A new hearing therapy called direct acoustical cochlear stimulation (DACS) was developed and validated in a first clinical trial with four patients. The key component of this therapy based on an implantable hearing device is a micro-actuator that is implanted in the mastoid right behind the external auditory canal of a patient. It generates vibrations that are directly coupled to the inner ear fluids and bypass therefore the outer and the middle ear. This allows treating severe to profound mixed hearing loss. The actuator transfer function has to be similar to the transfer function of a normal human middle ear to guarantee high system efficiency. A balanced armature actuator was the ideal transducer type in order to meet this requirement considering the given restrictions in size and shape.
