Effect of freezing and embalming of human cadaveric whole head specimens on bone conduction.

BACKGROUND AND AIMS: Conserved specimens do not decay and therefore permit long-term experiments thereby overcoming limited access to fresh (frozen) temporal bones for studies on middle ear mechanics. We used a Thiel conservation method which is mainly based on a watery solution of salts. In contrast to pure Formalin, Thiel conservation aims to preserve the mechanical proprieties of human tissue. The aim of this study is to examine the effect of Thiel conservation on bone conduction in the same specimen before and after conservation. METHODS: Nine ears of five defrosted whole heads were stimulated with a direct, electrically driven, bone anchored hearing system (Baha, Baha SuperPower). The motion produced by bone conduction stimulation was measured with a single point laser Doppler vibrometer (LDV) at the promontory, the ossicular chain, and the round window through a posterior tympanotomy. After the initial experiments, the entire whole heads were placed in Thiel solution. In order to enable direct comparison between fresh frozen and Thiel specimens, our Thiel conservation did not include intravascular and intrathecal perfusion. The measurements were repeated 3 and 12 months later. To determine the effect of freezing, defrosting, and embalming on the whole heads, CT scans were performed at different stages of the experimental procedure. Additionally, three extracted temporal bones were stimulated a Baha, motion of the promontory measured by LDV and embalmed in Thiel solution to investigate the direct impact of Thiel solution on the bone. RESULTS: The averaged magnitude of motion on the promontory increased in whole head specimens by a mean of 10.3 dB after 3 months of Thiel embalming and stayed stable after 12 months. A similar effect was observed for motion at the tympanic membrane (+7.2 dB), the stapes (+9.5 dB), and the round window (+4.0 dB). In contrast to the whole head specimens, the motion of the extracted temporal bones did not change after 3 months of Thiel embalming (-0.04 dB in average). CT scans of the whole heads after conservation showed a notable brain volume loss mostly >50% as well as a remarkable change in the consistency and structure of the brain. Partial changes could already be observed before the Thiel embalming but after 1-2 days of defrosting. In an additional experiment, a substitution of brain mass and weight by Thiel fluid did not lead to new deterioration in sound transmission. In contrast, a frozen (non-defrosted) whole head showed a distinctively reduced magnitude of promontory motion before defrosting. DISCUSSION: For our setup, the vibration of the ear due to bone conduction in the same whole head specimens significantly increased after Thiel conservation. Such an increase was not observed in extracted temporal bone specimens. Due to brain changes in the CT scans, we investigated the consequences of the brain volume changes and structure loss on the frozen brain before defrosting. The loss of brain volume alone could not explain the increase of ear vibrations, as we did not observe a difference when the volume was replaced with Thiel fluid. However, freezing and defrosting of the entire brain seems to have a major influence. Beside the destructive effect of freezing on the brain, the modified conservation method without perfusion changed the brain structure. In conclusion, bone conduction in whole heads depends on the physical condition of the brain, rather than on the conservation.

Comparison between incus short process and long process coupling of the vibrant soundbridge in human temporal bones.

OBJECTIVE: The Vibrant Soundbridge (VSB) is one of the most widely used implantable hearing devices. It consists of a vibrating floating mass transducer (FMT) that is connected to a middle ear structure. The standard coupling devices for sensorineural hearing loss are short process (SP) or long process (LP) couplers. DESIGN AND STUDY SAMPLE: This study directly compared the electro-mechanical performance of the SP- and LP-coupled FMT of the VSB in the same temporal bone specimen (n = 10). We measured velocity magnitudes and total harmonic distortions (THD) of the stapes (ST) and the round window (RW) using laser Doppler Vibrometry (LDV). RESULTS: Comparison shows a maximally 10 dB higher magnitude for the LP coupler at ST and RW for frequencies below 600 Hz, whereas the SP coupler shows a maximally 20 dB higher magnitude at the ST and RW for frequencies above 600 Hz. THD show similar behaviour with less distortion at 500 Hz for the LP coupler and less distortions for the SP coupler in higher frequencies. CONCLUSIONS: Our experiments showed that the SP coupling may be mechanically favourable, in terms of magnitude and distortion, for the transmission of FMT vibrations at higher frequencies.

[Treatment of single-sided deafness by cochlear implantation]. / Traitement de la surdité unilatérale par l'implant cochléaire.

Single sided deafness diminishes speech understanding in noise and sound localization and thereby globally auditory performance. Most patients also suffer from tinnitus and indicate reduced quality of life. Patients have the choice to adapt to the new situation without treatment, to restore pseudostereophonic hearing by contralateral routing of signal (CROS) hearing aids or to restore binaural hearing using a cochlear implant in the deaf ear. This article summarizes the physiological base of binaural hearing and treatment options for single sided deafness with a special emphasis on the cochlear implant.

La surdité unilatérale diminue la compréhension dans le bruit et la capacité de localiser les sources sonores affectant ainsi globalement la performance auditive. De plus, la qualité de vie est souvent impactée par la présence d'un acouphène dérangeant. Les patients ont le choix de s'adapter à la situation sans traitement ou de reconstituer une pseudo-stéréophonie à l'aide d'un appareillage qui transmet l'information auditive arrivant sur l'oreille sourde à l'oreille saine (Contralateral Routing of Signals (CROS)). L'implant cochléaire est une alternative récente qui permet de « réactiver ¼ l'oreille atteinte et de redonner ainsi une audition binaurale. Les différentes options de réhabilitation auditive en cas de surdité unilatérale en mettant l'accent sur l'implant cochléaire sont discutées à l'aide d'un cas clinique.

Effect of conservation method on ear mechanics for the same specimen.

BACKGROUND AND AIMS: As an alternative to fresh temporal bones, Thiel conserved specimens can be used in the study of ear mechanics. Conserved temporal bones do not decay, permit long-term experiments and overcome problems with limited access to fresh (frozen) temporal bones. Air conduction motion of the tympanic membrane (TM), stapes (ST) and round window (RW) in Thiel specimens is similar to that of fresh specimens according to reports in the literature. Our study compares this motion directly before and after conservation for the same specimens. METHODS: The magnitude of motion of TM, ST and RW elicited by acoustic stimulation via the external auditory canal was measured using single point laser Doppler vibrometry (LDV) accessed through a posterior tympanotomy. For the initial measurements (10 ears), fresh frozen whole heads were thawed for at least 24 h. Afterwards, the entire whole heads were embalmed according to the Thiel embalming method and measurements were repeated 3 and 12 months later. RESULTS: The magnitudes of TM, ST and RW motion before and after Thiel conservation differed maximally 10 dB on average. A significant increase in TM motion was observed at low frequencies only after long term conservation (12 months). ST motions decreased significantly between 161 and 5300 Hz after 3 months of Thiel conservation. Over the same time period RW motions decreased significantly between 100 and 161 Hz and 489-788 Hz. The ST and RW motions across all measured frequencies were lower after 3 months by 5.7 dB and 7.1 dB, respectively, without further changes after 12 months of conservation. The mean phase shift between ST and RW motion was only 2.1° for frequencies below 450 Hz. DISCUSSION AND CONCLUSION: Thiel embalming changes motion of TM after long term conservation. ST and RW motion changed mainly after short term conservation. The phase shifts close to 180° between ST and RW motion indicates that the cochlea was still filled with liquid without air bubbles. The results show that Thiel conserved specimens can be used as an alternative model to fresh frozen preparations with some limitations when studying mechanics of the normal human ear, for example, in implant design.

Multicenter Study Investigating Foreign Language Acquisition at School in Children, Adolescents, and Young Adults With Uni- or Bilateral Cochlear Implants in the Swiss German Population.

OBJECTIVES: Evaluation of foreign language acquisition at school in cochlear implant patients. STUDY DESIGN: Multicenter cohort study. SETTING: CI centers. PATIENTS: One hundred twenty-five CI users (10-18 yr) in the German-speaking part of Switzerland were enrolled. Demographic data were obtained by means of written questionnaires. German-speaking children with mainstream foreign language tuition (English and/or French) were enrolled for further testing. The control group of normal-hearing individuals was matched on age, class, and number of foreign language lessons attended. RESULTS: Overall, 100 questionnaires were returned. The 12 CI users without foreign language learning attended special schools. CI users who attended foreign language classes had better German speech comprehension compared with those without foreign language tuition (89 versus 51%; p < 0.05). Thirty-one CI users of different grades were further tested. All (10/10) CI 6th graders attained the school objectives for both English reading and listening skills. French performance at 6th grade for reading was 3/7 and for listening only 1/7. There were 13 matched normal-hearing pairs for English and 10 for French. The total scores were on average 7% higher, with a statistical significance for English reading (p < 0.05). CONCLUSIONS: Almost 90% of CI children in Switzerland learn foreign language(s) at school. All the tested patients reached the current school objectives for English reading. The success rate for French was lower, especially regarding listening tasks. The 13 matched pairs with normal-hearing did not score substantially better.

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.

Influence of external ear occlusion on food perception.

PURPOSE: The present study aimed to explore if food perception can be influenced by sound mastication level when the external ear canal was occluded. METHODS: Fifty-nine adults (38 women) with normal hearing, smell, and taste participated in the study. They tasted five crispy and five soft food items over two sessions: one with and one without an earplug inserted in the external ear canal. Participants were asked to rate freshness and taste of the food as well as their willingness to eat more of it and how much they usually like this kind of food. The sound pressure level related to the food mastication was recorded with a probe microphone placed in the external ear canal. RESULTS: Compared to the open ear canal condition, levels of the mastication sounds were higher when the participants had their ears occluded, as well as for crispy than for soft food. Regarding food freshness, food appreciation, and willingness to eat more of the same food, there was no significant difference concerning food type, ear condition, and sex. For soft foods, men rated their usual liking of this food higher when they were wearing ear plugs compared to the opened condition. CONCLUSION: Plugging the ear canals led to increased mastication sound levels. Participants did not seem to consider these additional acoustic cues when they rated food freshness, food appreciation, and willingness of eating the specific food. Only men seemed to take these cues into account when they rated their habit consumption of soft food.

Spinal Surgery With Electrically Evoked Potential Monitoring and Monopolar Electrocautery: Is Prior Removal of a Cochlear Implant Necessary?

: Transcranial electric stimulation to generate motor evoked potentials in lower limb muscles is the standard technique used to monitor spinal cord efferent pathways during surgical correction for spinal deformities. Monopolar electrical cauterization is also used by default in the thoracic and lumbar area of the spine during this kind of surgery to prevent major blood loss. Owing to the high levels of current used, both techniques are considered contraindicative if the patient has a cochlear implant (CI). Here, we present a CI patient who underwent corrective spinal fusion surgery for a severe kyphoscoliotic spinal deformity on whom both techniques were used without any negative effects on the CI function. A major improvement in sagittal body balance was achieved with no loss in implant-aided hearing levels. These results add to reports that CI manufactures should review their evidence underlying recommendations that transcranial electric stimulation and upper thoracic monopolar electrical cauterization are high risk for CI users, possibly initiating verification studies.

Measurements of Trunk Sway for Stance and Gait Tasks 2 Years after Vestibular Neurectomy.

The aim of this study was to investigate changes in balance control for stance and gait tasks in patients 2 years before and after vestibular neurectomy (VN) performed to alleviate intractable Meniere's disease. Amplitudes of trunk sway in roll and pitch directions were measured for stance and gait tasks in 19 patients using gyroscopes mounted at the lower-back. Measurements before VN and 2 years later were compared to those of healthy age-matched controls (HC). We also examined if changes in trunk sway amplitudes were correlated with patients' subjective assessment of disability using the AAO-HNS scale. For patients with low AAO-HNS scores 0-2 (n = 14), trunk roll and pitch sway velocities, standing eyes closed on foam, increased 2 years post VN compared to HC values (p < 0.01). Trunk sway amplitudes remained at levels of HC for simple gait tasks, but task durations were longer and therefore gait slower. For complex gait tasks (stairs), balance control remained impaired at 2 years. In patients with AAO-HNS high scores level 6 (n = 5), balance control remained abnormal, compared to HC, 2 years postoperatively for all stance, several simple and all complex gait tasks. Trunk sway in the pitch and roll directions for stance tasks was correlated with clinical (AAO-HNS) scores (p ≤ 0.05). These results indicate that VN leads to chronic balance problems for stance and complex gait tasks. The problems are greater for patients with high compared to low AAO-HNS scores, thereby explaining the different symptoms reported by these patients. The lack of balance recovery in VN patients to levels of HCs after 2 years contrasts with the 3 months average recovery period for acute vestibular neuritis patients and is indicative of the effects of neurectomy on central compensation processes.

Balance Control during Stance and Gait after Cochlear Implant Surgery.

BACKGROUND: After cochlear implant (CI) surgery, some patients experience vertigo, dizziness and/or deficits in vestibulo-ocular reflexes. However, little is known about the effect of CI surgery on balance control. Therefore, we examined differences in stance and gait balance control before versus after CI surgery. METHODS: Balance control of 30 CI patients (mean age 59, SD 15.4 years), receiving a first unilateral CI surgery, was measured preoperatively and postoperatively 1 month after the initial implant stimulation (2 months after surgery). Trunk sway was measured during 14 stance and gait tests using an angular-velocity system mounted at lumbar vertebrae 1-3. RESULTS: For pre- versus postoperative comparisons across all 30 patients, a nonsignificant worsening in balance control was observed. Significant changes were, however, found within subgroups. Patients younger than 60 years of age had a significant worsening of an overall balance control index (BCI) after CI surgery (p = 0.008), as did patients with a normal BCI preoperatively (p = 0.005). Gait task measures comprising the BCI followed a similar pattern, but stance control was unchanged. In contrast, patients over 60 years or with a pathological BCI preoperatively showed improved tandem walking postoperatively (p = 0.0235). CONCLUSION: Across all CI patients, CI surgery has a minor effect on balance control 2 months postoperatively. However, for patients younger than 60 years and those with normal balance control preoperatively, balance control worsened for gait indicating the need for preoperative counseling.

Intracochlear Sound Pressure Measurements in Normal Human Temporal Bones During Bone Conduction Stimulation.

Bone conduction (BC) is heavily relied upon in the diagnosis and treatment of hearing loss, but is poorly understood. For example, the relative importance and frequency dependence of various identified BC sound transmission mechanisms that contribute to activate the cochlear partition remain unknown. Recently, we have developed techniques in fresh human cadaveric specimens to directly measure scalae pressures with micro-fiberoptic sensors, enabling us to monitor the input pressure drive across the cochlear partition that triggers the cochlear traveling wave during air conduction (AC) and round-window stimulation. However, BC stimulation poses challenges that can result in inaccurate intracochlear pressure measurements. Therefore, we have developed a new technique described here that allows for precise measurements during BC. Using this new technique, we found that BC stimulation resulted in pressure in scala vestibuli that was significantly higher in magnitude than in scala tympani for most frequencies, such that the differential pressure across the partition-the input pressure drive-was similar to scala vestibuli pressure. BC (stimulated by a Bone Anchored Hearing Aid [Baha]) showed that the mechanisms of sound transmission in BC differ from AC, and also showed the limitations of the Baha bandwidth. Certain kinematic measurements were generally proportional to the cochlear pressure input drive: for AC, velocity of the stapes, and for BC, low-frequency acceleration and high-frequency velocity of the cochlear promontory. Therefore, our data show that to estimate cochlear input drive in normal ears during AC, stapes velocity is a good measure. During BC, cochlear input drive can be estimated for low frequencies by promontory acceleration (though variable across ears), and for high frequencies by promontory velocity.

Impedances of the inner and middle ear estimated from intracochlear sound pressures in normal human temporal bones.

For almost a decade, we have measured intracochlear sound pressures evoked by air conducted (AC) sound presented to the ear canal in many fresh human cadaveric specimens. Similar measurements were also obtained during round window (RW) mechanical stimulation in multiple specimens. In the present study, we use our accumulated data of intracochlear pressures and simultaneous velocity measurements of the stapes or RW to determine acoustic impedances of the cochlear partition, RW, and the leakage paths from scala vestibuli and scala tympani, as well as the reverse middle ear impedance. With these impedances, we develop a computational lumped-element model of the normal ear that illuminates fundamental mechanisms of sound transmission. To calculate the impedances for our model, we use data that passes strict inclusion criteria of: (a) normal middle-ear transfer function defined as the ratio of stapes velocity to ear-canal sound pressure, (b) no evidence of air within the inner ear, and (c) tight control of the pressure sensor sensitivity. After this strict screening, updated normal means, as well as individual representative data, of ossicular velocities and intracochlear pressures for AC and RW stimulation are used to calculate impedances. This work demonstrates the existence and the value of physiological acoustic leak impedances that can sometimes contribute significantly to sound transmission for some stimulation modalities. This model allows understanding of human sound transmission mechanisms for various sound stimulation methods such as AC, RW, and bone conduction, as well as sound transmission related to otoacoustic emissions.

Audiological monitoring in Swiss childhood cancer patients.

BACKGROUND: Full audiological monitoring is the best strategy to detect hearing loss early and to provide timely intervention in the absence of a clinical method of otoprotection. Full monitoring requires audiological evaluation before, and then during and after ototoxic cancer treatment. In a worldwide context of monitoring protocols that vary substantially, we analyzed the audiological monitoring of childhood cancer patients over the last decade across treatment centers in Switzerland. PROCEDURE: We retrospectively searched for audiological evaluations in all nine Swiss Pediatric Oncology Centers. We analyzed proportions of patients who had audiological monitoring and described type and timing of monitoring. We determined predictors of audiological monitoring using multivariable logistic regression and described time trends. RESULTS: We included 185 patients from the Swiss Childhood Cancer Registry diagnosed from 2005 to 2013 who had platinum chemotherapy and/or cranial radiation ≥30 Gray and who were alive at time of study. Less than half of children, 43%, had full audiological monitoring (before, during, and after treatment), while 72% were tested after cancer treatment. Nonstudy patients were less likely to have had monitoring in all phases of cancer treatment. Patients who received treatment with cisplatin or both platinum chemotherapy and cranial radiation were more likely to have had monitoring after treatment. Monitoring during and after treatment increased over the study period, but monitoring before treatment was insufficient in all time periods. CONCLUSIONS: Our population-based study indicates that audiological monitoring is insufficient in Switzerland, particularly for nonstudy patients. Clinicians must become more aware of the importance of full audiological monitoring.

In situ Probe Microphone Measurement for Testing the Direct Acoustical Cochlear Stimulator.

Hypothesis: Acoustical measurements can be used for functional control of a direct acoustic cochlear stimulator (DACS). Background: The DACS is a recently released active hearing implant that works on the principle of a conventional piston prosthesis driven by the rod of an electromagnetic actuator. An inherent part of the DACS actuator is a thin titanium diaphragm that allows for movement of the stimulation rod while hermetically sealing the housing. In addition to mechanical stimulation, the actuator emits sound into the mastoid cavity because of the motion of the diaphragm. Methods: We investigated the use of the sound emission of a DACS for intra-operative testing. We measured sound emission in the external auditory canal (PEAC) and velocity of the actuators stimulation rod (Vact) in five implanted ears of whole-head specimens. We tested the influence various positions of the loudspeaker and a probe microphone on PEAC and simulated implant malfunction in one example. Results: Sound emission of the DACS with a signal-to-noise ratio >10 dB was observed between 0.5 and 5 kHz. Simulated implant misplacement or malfunction could be detected by the absence or shift in the characteristic resonance frequency of the actuator. PEAC changed by <6 dB for variations of the microphone and loudspeaker position. Conclusion: Our data support the feasibility of acoustical measurements for in situ testing of the DACS implant in the mastoid cavity as well as for post-operative monitoring of actuator function.

Directional Microphone Contralateral Routing of Signals in Cochlear Implant Users: A Within-Subjects Comparison.

OBJECTIVES: For medical or financial reasons, bilateral cochlear implantation is not always possible in bilaterally deafened patients. In such cases, a contralateral routing of signals (CROS) device could complement the monaural implant. The goal of our study was to compare the benefit of three different conditions: (1) unilateral cochlear implant (CI) alone, (2) unilateral CI complemented with a directional CROS microphone, and (3) bilateral CIs. DESIGN: Twelve bilateral experienced CI users were tested. Speech reception in noise and sound localization were measured in the three above-mentioned conditions. Patients evaluated which condition they presumed to be activated and the subjective benefit on a hearing scale. RESULTS: Compared with the unilateral CI condition, the additional CROS device provided significantly better speech intelligibility in noise when speech signals came from the front or side of the CROS microphone. Only small subjective improvement was observed. Bilateral-activated CIs further improved the hearing performance. This was the only condition where sound localization was possible. Subjective evaluation showed a clear preference for the bilateral CI treatment. CONCLUSIONS: In bilateral deafened patients, bilateral implantation is the most preferable form of treatment. However, patients with one implant only could benefit from an additional directional microphone CROS device.

Predisposing factors for adverse skin reactions with percutaneous bone anchored hearing devices implanted with skin reduction techniques.

We present an analysis of adverse events after implantation of bone anchored hearing device in our patient population with focus on individual risk factors for peri-implant skin reactions. The investigation involved a chart review of adult Baha patients (n = 179) with 203 Bahas implanted with skin reduction techniques between 1993 and 2009, a questionnaire (n = 97) and a free clinical examination (n = 47). Skin reactions were graded by severity from 0 (no skin reaction) to 4 (implant loss resulting from infection) according to Holgers. We analyzed the skin reaction rate (SRR) defined as the number of skin reactions per year and the worst Holgers grade (WHG), which indicates the grade of the worst skin reaction per implant. We defined 20 parameters including the demographic characteristics, surgery details, subjective benefits, handling and individual factors. The most frequent adverse events (85 %) were skin reactions. The average SRR was 0.426 per Baha year. Six parameters showed an association with the SRR or the WHG. The clinically most relevant factors are an elevated Body Mass Index (BMI, p = 0.02) and darker skin type (p = 0.03). The SRR increased with the distance between the tragus and the implant (p = 0.02). Regarding the identified risk factors, the SRR might be reduced by selecting a location for the implant near the pinna and by specific counseling regarding post-operative care for patients with darker skin type or an elevated Body Mass Index (BMI). Few of the factors analyzed were found to influence the SRR and WHG. Since most adverse skin reactions could be treated easily with local therapy, our results suggest that in adult patients, individual risk factors for skin reactions are not a contraindication for Baha implantation. Thus, patients can be selected purely on audiological criteria.

[Conservative and surgical rehabilitation of hearing loss]. / Apparative und operative Rehabilitation des Hörvermögens.

According to WHO 360 million people are hard of hearing. Hearing disorders are not only seen in elderly but also in children. Clinically we differentiate between hearing disorders concerning the transmission of sound from the outer ear to the cochlea (conductive hearing loss) and disorders with reduced sound perception concerning the inner ear an related structures (sensorineural hearing loss). This article summarizes common surgical and technical possibilities for rehabilitation. For each pathology we graphically illustrate the generic working principle of the rehabilitation including the indication range in an exemplary audiogram.

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.

[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.

Assessment of the effects of superior canal dehiscence location and size on intracochlear sound pressures.

Superior canal dehiscence (SCD) is a defect in the bony covering of the superior semicircular canal. Patients with SCD present with a wide range of symptoms, including hearing loss, yet it is unknown whether hearing is affected by parameters such as the location of the SCD. Our previous human cadaveric temporal bone study, utilizing intracochlear pressure measurements, generally showed that an increase in dehiscence size caused a low-frequency monotonic decrease in the cochlear drive across the partition, consistent with increased hearing loss. This previous study was limited to SCD sizes including and smaller than 2 mm long and 0.7 mm wide. However, the effects of larger SCDs (>2 mm long) were not studied, although larger SCDs are seen in many patients. Therefore, to answer the effect of parameters that have not been studied, this present study assessed the effect of SCD location and the effect of large-sized SCDs (>2 mm long) on intracochlear pressures. We used simultaneous measurements of sound pressures in the scala vestibuli and scala tympani at the base of the cochlea to determine the sound pressure difference across the cochlear partition - a measure of the cochlear drive in a temporal bone preparation - allowing for assessment of hearing loss. We measured the cochlear drive before and after SCDs were made at different locations (e.g. closer to the ampulla of the superior semicircular canal or closer to the common crus) and for different dehiscence sizes (including larger than 2 mm long and 0.7 mm wide). Our measurements suggest the following: (1) different SCD locations result in similar cochlear drive and (2) larger SCDs produce larger decreases in cochlear drive at low frequencies. However, the effect of SCD size seems to saturate as the size increases above 2-3 mm long and 0.7 mm wide. Although the monotonic effect was generally consistent across ears, the quantitative amount of change in cochlear drive due to dehiscence size varied across ears. Additionally, the size of the dehiscence above which the effect on hearing saturated varied across ears. These findings show that the location of the SCD does not generally influence the amount of hearing loss and that SCD size can help explain some of the variability of hearing loss in patients.