Intracochlear pressure in cadaver heads under bone conduction and intracranial fluid stimulation

Background The frequency dependent contributions of the various bone conduction pathways are poorly understood, especially the fluid pathway. The aim of this work is to measure and investigate sound pressure propagation from the intracranial space to the cochlear fluid. Methods Stimulation was provided sequentially to the bone (BC) or directly to the intracranial contents (hydrodynamic conduction, or HC) in four cadaver heads, where each ear was tested individually, for a total of 8 samples. Intracranial pressure was generated and monitored via commercial hydrophones, while the intracochlear sound pressure (ICSP) levels were monitored via custom-made intracochlear acoustic receivers (ICAR). In parallel, measurements of the 3D motion of the cochlear promontory and stapes were made via 3D Laser Doppler Vibrometer (3D LDV). Results Reliability of the intracochlear sound pressure measurements depends on the immobilization of the ICAR relative to the otic capsule. Regardless of the significant differences in absolute stapes and promontory motion, the ratios between the otic capsule velocity, the stapes volume velocity (relative to the cochlea), and the intracochlear pressure were very similar under BC and HC stimulus. Under HC, the cochlear fluid appears be activated by an osseous pathway, rather than a direct non-osseous pathway from the cerebrospinal fluid (CSF), however, the osseous pathway itself is activated by the CSF pressure. Conclusions Data suggests that the skull bone surrounding the brain and CSF could play a role in the interaction between the two CSF and the cochlea, under both stimulation conditions, at high frequencies, while inertia is dominant factor at low frequencies. Further work should be focused on the investigation of the solid-fluid interaction between the skull bone walls and the intracranial content

Performance evaluation of a novel piezoelectric subcutaneous bone conduction device

Objectives Evaluation of the transfer function efficiency of a newly-developed piezo-electric actuator for active subcutaneous bone conduction hearing aid. Methods The experiments were conducted on four Thiel embalmed whole head cadaver specimens. A novel actuator based on piezo-electric transduction (PZTA), part of a subcutaneous bone conduction hearing aid device, was sequentially implanted on three locations: 1) Immediately posterior to pinna; 2) 50–60 mm posterior to pinna, approximately the same distance as between the BAHA (bone anchored hearing aid) location and the ear canal, but the same horizontal level as location 1; 3) the traditional BAHA location. Using a single point 3-dimensional laser Doppler vibrometer (LDV) system, three types of motion measurements were performed at the cochlear promontory for each stimulation location: 1) ipsilateral side, 2) contralateral side, 3) measurements 1 and 2 were repeated after mastoidectomy on the ipsilateral side. Results On average, stimulation at locations 1 and 2 show a trend for higher promontory motion relative to location 3 (BAHA location) above 1 kHz. Stimulation at location 1 had an average improvement of 1–6 dB at 2–4 kHz, and 1–18 dB at 6–8 kHz. The spatial composition of the motion showed significant contributions from both in-plane and out-of-plane (along ear canal) motion components, with in-plane components being dominant at mid and high frequencies for locations 2 and 3. Stimulation at locations 1 and 3 produced similar transcranial attenuation at mid frequencies (0.6–4 kHz), with a potential trend of higher attenuation (seen in 3 or the 4 samples) for location 1 at higher frequencies (>4 kHz). The mastoidectomy affected negatively mostly the high frequencies (6–8 kHz) for stimulation at location 1, with no significant change for location 3. Conclusion The sound transfer function efficacy of a novel subcutaneous bone conduction device has been quantified, and the influence of stimulation location and mastoidectomy have been analyzed based on promontory motion in Thiel-preserved cadaver heads

Subjective Sound Quality Detection (HISQUI) over Time after Vibrant Soundbridge Implantation

Background: To evaluate the long-term audiological outcomes combined with the Hearing Implant Sound Quality Index (HISQUI) after Vibrant Soundbridge (VSB) implantation. Methods: Prospective recall cohort study of patients who received a VSB in a tertiary academic medical center between 1996 and 2017. Air conduction (AC) and bone conduction (BC), sound field thresholds in aided and unaided conditions, and speech discrimination in noise (Oldenburger sentence test) were measured. Postoperative results were compared with preoperative audiograms. Furthermore, the HISQUI was evaluated. Results: Ten patients (eleven implants) were included, the mean follow up period was nine years. The mean AC threshold preoperatively was between 63 and 70 dB, and the BC was between 38 and 49 dB from 500 to 4000 Hz. In the free-field audiogram, the mean threshold was between 61 and 77 dB unaided vs. between 28 and 52 dB in the aided condition. The average signal to noise ratio (SNR) in the Oldenburger sentence test in the unaided condition was 10 dB ± 6.7 dB vs. 2 dB ± 5.4 dB in the aided condition. Three patients reported a good to very good hearing result, four patients a moderate, and three patients a poor hearing result. There was a significant association between the years of implantation and the HISQUI (p = 0.013), as well as a significant decrease by 14 HISQUI points per 10 dB SPL decline (SE 5.2, p = 0.023). There was a significant difference between the change of BC over the years and the HISQUI, as well as the number of years after implantation and the HISQUI. On average, per dB decrease in BC, the HISQUI decreases by 1.4 points, and every year after implantation the HISQUI decreases by 2.7 points. Conclusions: The aided threshold in free field and speech understanding in noise improved significantly with VSB. An increase over time of BC thresholds was observed as well as a decrease in HISQUI score. This decrease in BC thresholds over time may be due to presbycusis. Therefore, monitoring of these patients over time should be considered to discuss alternative hearing rehabilitation measures in a timely manner

Experimental investigation of promontory motion and intracranial pressure following bone conduction: Stimulation site and coupling type dependence

Objective Investigation of bone conduction sound propagation by osseous and non-osseous pathways and their interactions based upon the stimulation site and coupling method of the actuator from a bone conduction hearing aid (BCHA). Methods Experiments were conducted on five Thiel embalmed whole head cadaver specimens. The electromagnetic actuator from a commercial bone conduction hearing aid (BCHA) (Baha® Cordelle II) was used to provide a stepped sine stimulus in the range of 0.1–10 kHz. Osseous pathways (direct bone stimulation or transcutaneous stimulation) were sequentially activated by stimulation at the mastoid or the BAHA side using several methods including a percutaneously implanted screw, Baha® Attract transcutaneous magnet and a 5-N (5-N) steel headband. Non-osseous pathways (only soft tissue or intra-cranial contents) were activated by actuator stimulation on the eye or neck via attachment to a 5-N steel headband, and were compared with stimulation via equivalent attachment on the mastoid and forehead. The response of the skull was measured as motions of the ipsi- and contralateral promontory and intracranial pressure (ICP) in the central, anterior, posterior, ipsilateral and contralateral temporal regions of the cranial space. Promontory motion was monitored using a 3-dimensional Laser Doppler vibrometer (3D LDV) system. Results The promontory undergoes spatially complex motion with similar contributions from all motion components, regardless of stimulation mode. Combined 3D promontory motion provided lower inter-sample variability than did any individual component. Transcranial transmission showed gain for the low frequencies and attenuation above 1 kHz, independent of stimulation mode This effect was not only for the magnitude but also its spatial composition such that contralateral promontory motion did not follow the direction of ipsilateral stimulation above 0.5 kHz. Non-osseous stimulation on the neck and eye induced comparable ICP relative to percutaneous (via screw) mastoid stimulation. Corresponding phase data indicated lower phase delays for ICP when stimulation was via non-osseous means (i.e., to the eye) versus osseous means (i.e., to the mastoid or forehead). Sound propagation due to skull stimulation passes through the thicker bony sections first before activating the CSF. Conclusion Utilization of 3D promontory motion measurements provides more precise (lower inter-sample variability) information about bone vibrations than does any individual component. It also provides a more detailed description of transcranial attenuation. A comprehensive combination of motion and pressures measurements across the head, combined with a variation of the stimulation condition, could reveal details about sound transmission within the skull

Changes of Electrocochleographic Responses During Cochlear Implantation Presented at the Annual Meeting of ADANO 2016 in Berlin

OBJECTIVE: To assess by electrocochleography (ECoG) at which times during cochlear implantation changes of cochlear function occur. METHODS: Tone bursts with a frequency of 500 or 750 Hz were used as acoustic stimuli. The recording electrode was placed on the promontory and left in an unchanged position for all ECoG recordings. RESULTS: Eight subjects were included. After opening the cochlea, an increase of the amplitude of the ECoG signal was detectable in four subjects (mean change 3.9 dB, range from 0.2 to 10.8 dB). No decreases were detectable after opening the cochlea or during the first half of the insertion of the CI electrode array (mean change 0.5 dB, range from -2.2 to 1.6 dB). During the second half of the insertion, the amplitude of the ECoG signal decreased in four subjects (mean change -2.5 dB, range from -0.04 to -4.8 dB). If a decrease occurred during the second half of the insertion, then the decrease continued in the earliest phase after insertion of the CI electrode array (mean change -2.1 dB, range from -0.5 to -5.8 dB). CONCLUSION: Pressure changes inside the cochlea can lead to an increase of ECoG signals after opening the cochlea. If detectable, then a decrease of ECoG signals occurs during the second half of the insertion of the CI electrode array and continues in the earliest phase after completed insertion. These findings suggest that cochlear trauma occurs toward the end of the insertion and that trauma-dependent postoperative mechanisms contribute to postoperative hearing loss

Influence of directionality and maximal power output on speech understanding with bone anchored hearing implants in single sided deafness

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 2.2-2.8dB (p=0.004-0.016). In spatial setting S0N90, speech understanding in noise was reduced by either BAHI, but was significantly better by 1.0-1.8dB, 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

Influence of directionality and maximal power output on speech understanding with bone anchored hearing implants in single sided deafness

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 2.2-2.8dB (p=0.004-0.016). In spatial setting S0N90, speech understanding in noise was reduced by either BAHI, but was significantly better by 1.0-1.8dB, 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

Hearing Loss in Cancer Patients with Skull Base Tumors Undergoing Pencil Beam Scanning Proton Therapy: A Retrospective Cohort Study.

To assess the incidence and severity of changes in hearing threshold in patients undergoing high-dose pencil-beam-scanning proton therapy (PBS-PT). This retrospective cohort study included fifty-one patients (median 50 years (range, 13-68)) treated with PBS-PT for skull base tumors. No chemotherapy was delivered. Pure tone averages (PTAs)were determined before (baseline) and after PBS-PT as the average hearing thresholds at frequencies of 0.5, 1, 2, and 4 kHz. Hearing changes were calculated as PTA differences between pre-and post-PBS-PT. A linear mixed-effects model was used to assess the relationship between the PTA at the follow-up and the baseline, the cochlea radiation dose intensity, the increased age, and the years after PBS-PT. Included patients were treated for chordoma (n = 24), chondrosarcoma (n = 9), head and neck tumors (n = 9), or meningioma (n = 3), with a mean tumor dose of 71.1 Gy (RBE) (range, 52.0-77.8), and a mean dose of 37 Gy (RBE) (range, 0.0-72.7) was delivered to the cochleas. The median time to the first follow-up was 11 months (IQR, 5.5-33.7). The PTA increased from a median of 15 dB (IQR 10.0-25) at the baseline to 23.8 (IQR 11.3-46.3) at the first follow-up. In the linear mixed-effect model, the baseline PTA (estimate 0.80, 95%CI 0.64 to 0.96, p ≤ 0.001), patient's age (0.30, 0.03 to 0.57, p = 0.029), follow-up time (2.07, 0.92 to 3.23, p ≤ 0.001), and mean cochlear dose in Gy (RBE) (0.34, 0.21 to 0.46, p ≤ 0.001) were all significantly associated with an increase in PTA at follow-up. The applied cochlear dose and baseline PTA, age, and time after treatment were significantly associated with hearing loss after proton therapy

Hearing Loss in Cancer Patients with Skull Base Tumors Undergoing Pencil Beam Scanning Proton Therapy: A Retrospective Cohort Study

To assess the incidence and severity of changes in hearing threshold in patients undergoing high-dose pencil-beam-scanning proton therapy (PBS-PT). This retrospective cohort study included fifty-one patients (median 50 years (range, 13–68)) treated with PBS-PT for skull base tumors. No chemotherapy was delivered. Pure tone averages (PTAs)were determined before (baseline) and after PBS-PT as the average hearing thresholds at frequencies of 0.5, 1, 2, and 4 kHz. Hearing changes were calculated as PTA differences between pre-and post-PBS-PT. A linear mixed-effects model was used to assess the relationship between the PTA at the follow-up and the baseline, the cochlea radiation dose intensity, the increased age, and the years after PBS-PT. Included patients were treated for chordoma (n = 24), chondrosarcoma (n = 9), head and neck tumors (n = 9), or meningioma (n = 3), with a mean tumor dose of 71.1 Gy (RBE) (range, 52.0–77.8), and a mean dose of 37 Gy (RBE) (range, 0.0–72.7) was delivered to the cochleas. The median time to the first follow-up was 11 months (IQR, 5.5–33.7). The PTA increased from a median of 15 dB (IQR 10.0–25) at the baseline to 23.8 (IQR 11.3–46.3) at the first follow-up. In the linear mixed-effect model, the baseline PTA (estimate 0.80, 95%CI 0.64 to 0.96, p ≤ 0.001), patient’s age (0.30, 0.03 to 0.57, p = 0.029), follow-up time (2.07, 0.92 to 3.23, p ≤ 0.001), and mean cochlear dose in Gy (RBE) (0.34, 0.21 to 0.46, p ≤ 0.001) were all significantly associated with an increase in PTA at follow-up. The applied cochlear dose and baseline PTA, age, and time after treatment were significantly associated with hearing loss after proton therap