Using a cochlear implant processor as contralateral routing of signals device in unilateral cochlear implant recipients.

PURPOSE: In unilateral cochlear implant (CI) recipients, a contralateral routing of signals (CROS) device enables to receive auditory information from the unaided side. This study investigates the feasibility as well as subjective and objective benefits of using a CI processor as a CROS device in unilateral CI recipients. METHODS: This is a single-center, prospective cohort study. First, we tested the directionality of the CROS processor in an acoustic chamber. Second, we examined the difference of speech perception in quiet and in noise in ten unilateral CI recipients with and without the CROS processor. Third, subjective ratings with the CROS processor were evaluated according to the Client Oriented Scale of Improvement Questionnaire. RESULTS: There was a time delay between the two devices of 3 ms. Connection of the CROS processor led to a summation effect of 3 dB as well as a more constant amplification along all azimuths. Speech perception in quiet showed an increased word recognition score at 50 dB (mean improvement 7%). In noise, the head shadow effect could be mitigated with significant gain in speech perception (mean improvement 8.4 dB). This advantage was reversed in unfavorable listening situations, where the CROS device considerably amplified the noise (mean: - 4.8 dB). Subjectively, patients who did not normally wear a hearing aid on the non-CI side were satisfied with the CROS device. CONCLUSIONS: The connection and synchronization of a CI processor as a CROS device is technically feasible and the signal processing strategies of the device can be exploited. In contra-laterally unaided patients, a subjective benefit can be achieved when wearing the CROS processor.

Tympanic membrane surface motions in forward and reverse middle ear transmissions.

Characterization of Tympanic Membrane (TM) surface motions with forward and reverse stimulation is important to understanding how the TM transduces acoustical and mechanical energy in both directions. In this paper, stroboscopic opto-electronic holography is used to quantify motions of the entire TM surface induced by forward sound and reverse mechanical stimulation in human cadaveric ears from 0.25 to 18.4 kHz. The forward sound stimulus was coupled to an anatomically realistic artificial ear canal that allowed optical access to the entire TM surface, and the reverse mechanical stimulus was applied to the body of the incus by a piezo-electric stimulator. The results show clear differences in TM surface motions evoked by the two stimuli. In the forward case, TM motion is dominated by standing-wave-like modal motions that are consistent with a relatively uniform sound-pressure load over the entire TM surface. With reverse mechanical stimulation, the TM surface shows more traveling waves, consistent with a localized mechanical drive applied to the manubrium embedded in the TM. With both stimuli, the manubrium moves less than the rest of the TM, consistent with the TM acting like a compliant membrane rather than a stiff diaphragm, and also consistent with catenary behavior due to the TM's curved shape.

Influence of Telecommunication Modality, Internet Transmission Quality, and Accessories on Speech Perception in Cochlear Implant Users.

BACKGROUND: Telecommunication is limited or even impossible for more than one-thirds of all cochlear implant (CI) users. OBJECTIVE: We sought therefore to study the impact of voice quality on speech perception with voice over Internet protocol (VoIP) under real and adverse network conditions. METHODS: Telephone speech perception was assessed in 19 CI users (15-69 years, average 42 years), using the German HSM (Hochmair-Schulz-Moser) sentence test comparing Skype and conventional telephone (public switched telephone networks, PSTN) transmission using a personal computer (PC) and a digital enhanced cordless telecommunications (DECT) telephone dual device. Five different Internet transmission quality modes and four accessories (PC speakers, headphones, 3.5 mm jack audio cable, and induction loop) were compared. As a secondary outcome, the subjective perceived voice quality was assessed using the mean opinion score (MOS). RESULTS: Speech telephone perception was significantly better (median 91.6%, P<.001) with Skype compared with PSTN (median 42.5%) under optimal conditions. Skype calls under adverse network conditions (data packet loss > 15%) were not superior to conventional telephony. In addition, there were no significant differences between the tested accessories (P>.05) using a PC. Coupling a Skype DECT phone device with an audio cable to the CI, however, resulted in higher speech perception (median 65%) and subjective MOS scores (3.2) than using PSTN (median 7.5%, P<.001). CONCLUSIONS: Skype calls significantly improve speech perception for CI users compared with conventional telephony under real network conditions. Listening accessories do not further improve listening experience. Current Skype DECT telephone devices do not fully offer technical advantages in voice quality.

Topographic bone thickness maps for Bonebridge implantations.

Bonebridge™ (BB) implantation relies on optimal anchoring of the bone-conduction implant in the temporal bone. Preoperative position planning has to account for the available bone thickness minimizing unwanted interference with underlying anatomical structures. This study describes the first clinical experience with a planning method based on topographic bone thickness maps (TBTM) for presigmoid BB implantations. The temporal bone was segmented enabling three-dimensional surface generation. Distances between the external and internal surface were color encoded and mapped to a TBTM. Suitable implant positions were planned with reference to the TBTM. Surgery was performed according to the standard procedure (n = 7). Computation of the TBTM and consecutive implant position planning took 70 min on average for a trained technician. Surgical time for implantations under passive TBTM image guidance was 60 min, on average. The sigmoid sinus (n = 5) and dura mater (n = 1) were exposed, as predicted with the TBTM. Feasibility of the TBTM method was shown for standard presigmoid BB implantations. The projection of three-dimensional bone thickness information into a single topographic map provides the surgeon with an intuitive display of the anatomical situation prior to implantation. Nevertheless, TBTM generation time has to be significantly reduced to simplify integration in clinical routine.

[A new bone anchored hemodialysis access]. / Neuartiger knochenverankerter Hämodialysezugang.

When classic arteriovenous fistulas or grafts fail, dialysis patients have a vital requirement for a catheter to ensure vascular access. Permanent central venous catheters penetrate the cervical and thoracic soft tissues and the skin without rigid fixation. The infection rate for such devices is high, often requiring explantation. Bone anchored hearing aids are an established treatment in patients with conductive hearing loss. The implant is firmly fixed on the temporal bone and the abutment permanently penetrates the skin. Severe infections requiring explantation are very rare. We suppose that one of the main reasons for the low complication rate is the firm fixation of the implant to the temporal bone, which minimizes the movement of the skin relative to the underlying bone. Based on the experience with implantable hearing devices we developed a percutaneous bone anchored port fixed to the skull in the region of the temporal bone. Such a bone anchored port could be a beneficial alternative to conventional central venous catheters for patients undergoing hemodialysis. In the course of the development process we investigated the individual anatomy to locate the correct implantation site with sufficient bone thickness; we studied screw stability in bone; we developed the titanium implant that houses the port system as well as the surgical tools and procedure for save implantation; we tested flow rate, leak tightness and purification on mockups; we defined the Seldinger-insertion of the catheter into the internal jugular vein via a small neck incision. Our results show the technical feasibility of a temporal bone anchored port and form the basis of a now-approved clinical pilot study.

Round window and promontory movements during bone conduction with different middle ear conditions in Thiel embalmed specimens.

BACKGROUND: Thiel conservation is mainly based on a watery solution of salts. We have shown that bone conduction (BC) evokes motion in normal middle ears of Thiel embalmed specimens that is comparable to the motion for other cadaveric models. AIMS/OBJECTIVES: We evaluated whether promontory and round window (RW) motion identifies differences in BC transmission for different middle ear conditions. METHODS: We investigated the conditions of mobile ossicle chain, cement-fixed stapes and stapedectomy in seven ears. A retroauricular bone anchored hearing system provided BC stimulation. The motions of the promontory and the RW were measured using single point laser Doppler vibrometer (LDV, HLV1000, Polytec). RESULTS: The averaged differences between the conditions were small for RW motion and for promontory motion. However, for RW motion we found differences of more than one standard deviation at some frequencies. These differences in RW motion were more apparent when we limited the analysis to three selected specimens. CONCLUSIONS AND SIGNIFICANCE: Extracochlear measurement of the RW motion with LDV allowed differentiation between BC for different middle ear conditions. These changes could be detected best in a small frequency range in selected specimens. Promontory motion could not be used to differentiate between different conditions of the middle ear. ABBREVIATIONS: LDV: laser Doppler vibrometry; Prom: cochlear promontory; RW: round window; ST: stapes; TM: tympanic membrane; VProm: velocity of the promontory; VRW: velocity of the round window.

Mobile Internet Telephony Improves Speech Intelligibility and Quality for Cochlear Implant Recipients.

OBJECTIVE: The objective of this study was to investigate the benefit of mobile Voice over Internet protocol (VoIP) over conventional mobile phone calls (Global System for Mobile Communications, GSM) on speech intelligibility and quality for cochlear implant (CI) recipients. STUDY DESIGN: Cross-sectional, prospective. SETTING: Tertiary referral center. PATIENTS: A volunteer sample of experienced, German-speaking, adult CI recipients was considered. Volunteers with less than 50% aided monosyllabic word discrimination were excluded. INTERVENTION: Smartphone communication was changed from GSM to VoIP on two separate devices (A and B). MAIN OUTCOME MEASURES: Speech intelligibility was assessed with the Hochmair-Shulz-Moser (HSM) test in noise, speech quality with the mean opinion score (MOS) survey and the perceptual evaluation of speech quality (PESQ) algorithm. RESULTS: With device A, the mean HSM scores were 64.40% ±â€Š32.41 with GSM and 77.28% ±â€Š21.60 with VoIP (p = 0.0573). 66.7% of patients had a higher score with VoIP. For device B the means were 53.90% ±â€Š21.77 and 69.07% ±â€Š21.09 (p < 0.0001). 94.1% patients scored better with VoIP.With device A the average MOS scores were 3.12 ±â€Š1.52 and 4.08 ±â€Š0.95 (p = 0.0078). 76.9% of patients gave a higher score with VoIP. With device B the means were 2.71 ±â€Š1.08 and 3.528 ±â€Š1.44 (p = 0.0068). 56.3% of patients gave a higher score with VoIP. The effect was smaller when using an accessory cable. PESQ scores were significantly higher with VoIP (p < 0.001) in all configurations. CONCLUSIONS: CI recipients experience speech intelligibility and quality improvements using VoIP on a smartphone compared with conventional mobile phone calls.

Novel Bone-Anchored Vascular Access on the Mastoid for Hemodialysis: Concept and Preclinical Trials.

GOAL: We present the development of a bone-anchored port for the painless long-term hemodialytic treatment of patients with renal failure. This port is implanted behind the ear. METHODS: The port was developed based on knowledge obtained from long-term experience with implantable hearing devices, which are firmly anchored to the bone behind the ear. This concept of bone anchoring was adapted to the requirements for a vascular access during hemodialysis. The investigational device is comprised of a base plate that is firmly fixed with bone screws to the bone behind the ear (temporal bone). A catheter leads from the base plate valve block through the internal jugular vein and into the right atrium. The valves are opened using a special disposable adapter, without any need to puncture the blood vessels. Between hemodialysis sessions, the port is protected with a disposable cover. RESULTS: Flow rate, leak tightness, and purification were tested on mockups. Preoperative planning and the surgical procedure were verified in 15 anatomical human whole head specimens. CONCLUSION: Preclinical evaluations demonstrated the technical feasibility and safety of the investigational device. SIGNIFICANCE: Approximately 1.5 million people are treated with hemodialysis worldwide, and 25% of the overall cost of dialysis therapy results from vascular access problems. New approaches toward enhancing vascular access could potentially reduce the costs and complications of hemodialytic therapy.

Simultaneous full-field 3-D vibrometry of the human eardrum using spatial-bandwidth multiplexed holography.

Holographic interferometric methods typically require the use of three sensitivity vectors in order to obtain three-dimensional (3-D) information. Methods based on multiple directions of illumination have limited applications when studying biological tissues that have temporally varying responses such as the tympanic membrane (TM). Therefore, to measure 3-D displacements in such applications, the measurements along all the sensitivity vectors have to be done simultaneously. We propose a multiple-illumination directions approach to measure 3-D displacements from a single-shot hologram that contains displacement information from three sensitivity vectors. The hologram of an object of interest is simultaneously recorded with three incoherently superimposed pairs of reference and object beams. The incident off-axis angles of the reference beams are adjusted such that the frequency components of the multiplexed hologram are completely separate. Because of the differences in the directions and wavelengths of the reference beams, the positions of each reconstructed image corresponding to each sensitivity vector are different. We implemented a registration algorithm to accurately translate individual components of the hologram into a single global coordinate system to calculate 3-D displacements. The results include magnitudes and phases of 3-D sound-induced motions of a human cadaveric TM at several excitation frequencies showing modal and traveling wave motions on its surface.

The Effect of Ear Canal Orientation on Tympanic Membrane Motion and the Sound Field Near the Tympanic Membrane.

The contribution of human ear canal orientation to tympanic membrane (TM) surface motion and sound pressure distribution near the TM surface is investigated by using an artificial ear canal (aEC) similar in dimensions to the natural human ear canal. The aEC replaced the bony ear canal of cadaveric human temporal bones. The radial orientation of the aEC relative to the manubrium of the TM was varied. Tones of 0.2 to 18.4 kHz delivered through the aEC induced surface motions of the TM that were quantified using stroboscopic holography; the distribution of sound in the plane of the tympanic ring P TR was measured with a probe tube microphone. The results suggest that the ear canal orientation has no substantial effect on TM surface motions, but P TR at frequencies above 10 kHz is influenced by the ear canal orientation. The complex TM surface motion patterns observed at frequencies above a few kilohertz are not correlated with simpler variations in P TR distribution at the same frequencies, suggesting that the complex sound-induced TM motions are more related to the TM mechanical properties, shape, and boundary conditions rather than to spatial variations in the acoustic stimulus.

Hemodynamics and flow characteristics of a new dialysis port.

Renal replacement therapy by hemodialysis requires a permanent vascular access. Implantable ports offer a potential alternative to standard vascular access strategies although their development is limited both in number and extent. We explored the fluid dynamics within two new percutaneous bone-anchored dialysis port prototypes, both by in vitro experiments and computer simulation. The new port is to be fixed to bone and allows the connection of a dialysis machine to a central venous catheter via a built-in valve. We found that the pressure drop induced by the two ports was between 20 and 50 mmHg at 500 ml/min, which is comparable with commercial catheter connectors (15-80 mmHg). We observed the formation of vortices in both geometries, and a shear rate in the physiological range (<10,000s-1), which is lower than maximal shear rates reported in commercial catheters (up to 13,000s-1). A difference in surface shear rate of 15% between the two ports was obtained.

Comparisons of the mechanics of partial and total ossicular replacement prostheses with cartilage in a cadaveric temporal bone preparation.

CONCLUSIONS: Reconstruction of the ossicular chain differentially affects the motion of the tympanic membrane (TM) and the stapes. OBJECTIVES: To determine the effect of different ossicular replacement procedures on the sound-induced motion of the TM and stapes. METHODS: A combination of digital stroboscopic holography and laser Doppler vibrometry was used to determine the sound-induced motion of the TM and stapes in cadaveric temporal bones in which the ossicular chain was reconstructed using 12 varied standard techniques. The variations included the use of total or partial ossicular prosthesis, size of cartilage interposed between the TM and the prosthesis, and the length or fit of the prosthesis between the TM and stapes. The measurements were carried out in repeated measures format, so that each manipulation was performed in each temporal bone. RESULTS: The volume displacement of the TM was in general reduced by reconstruction, with the largest reductions occurring with high-frequency stimulation in the reconstructions with a 'large' cartilage oval interposed between the TM and the prosthesis. Larger stapes motions in response to low-frequency sound were observed with either 'loose' or 'best' fit TORP with a 'small' cartilage plate between the TM and the prosthesis.

A Bone-Thickness Map as a Guide for Bone-Anchored Port Implantation Surgery in the Temporal Bone.

The bone-anchored port (BAP) is an investigational implant, which is intended to be fixed on the temporal bone and provide vascular access. There are a number of implants taking advantage of the stability and available room in the temporal bone. These devices range from implantable hearing aids to percutaneous ports. During temporal bone surgery, injuring critical anatomical structures must be avoided. Several methods for computer-assisted temporal bone surgery are reported, which typically add an additional procedure for the patient. We propose a surgical guide in the form of a bone-thickness map displaying anatomical landmarks that can be used for planning of the surgery, and for the intra-operative decision of the implant's location. The retro-auricular region of the temporal and parietal bone was marked on cone-beam computed tomography scans and tridimensional surfaces displaying the bone thickness were created from this space. We compared this method using a thickness map (n = 10) with conventional surgery without assistance (n = 5) in isolated human anatomical whole head specimens. The use of the thickness map reduced the rate of Dura Mater exposition from 100% to 20% and suppressed sigmoid sinus exposures. The study shows that a bone-thickness map can be used as a low-complexity method to improve patient's safety during BAP surgery in the temporal bone.

Bone conduction in Thiel-embalmed cadaver heads.

INTRODUCTION: Sound can reach the inner ear via at least two different pathways: air conduction and bone conduction (BC). BC hearing is used clinically for diagnostic purposes and for BC hearing aids. Research on the motion of the human middle ear in response to BC stimulation is typically conducted using cadaver models. We evaluated middle ear motion of Thiel-embalmed whole-head specimens in terms of linearity, reproducibility, and consistency with the reported middle ear motion of living subjects, fresh cadaveric temporal bones, and whole-heads embalmed with a Non-Thiel solution of salts. METHODS: We used laser Doppler vibrometry to measure the displacement of the skull, the umbo, the cochlear promontory, the stapes, and the round window in seven ears from four human whole-head specimens embalmed according to Thiel's method. The ears were stimulated with a Baha(®) implanted behind the auricle. RESULTS: The Thiel model shows promontory velocity similar to that reported in the literature for whole-heads embalmed with a Non-Thiel solution of salts (0- to 7-dB difference). The Thiel heads' relative velocity of the stapes with respect to the promontory was similar to that of fresh cadaver temporal bones (0- to 4-dB difference). The velocity of the umbo was comparable in Thiel-embalmed heads and living subjects (0- to 10-dB difference). The skull and all middle ear elements measured responded linearly to different stimulation levels, with an average difference less than 1 dB. The variability of repeated measurements for both short- (2 h; 4 dB) and long-term (4-16 weeks; 6 dB) repetitions in the same ear, and the difference between the two ears of the same donor (approximately 10 dB) were lower than the inter-individual difference (up to 25 dB). CONCLUSION: Thiel-embalmed human whole-head specimens can be used as an alternative model for the study of human middle ear mechanics secondary to BC stimulation. At some frequencies, differences from living subjects must be considered.