Rene G. Van Wijhe

Optimum Tension for Partial Ossicular Replacement Prosthesis Reconstruction in the Human Middle Ear

Objective: Hearing results from ossiculoplasty are unpredictable. There are many potentially modifiable parameters. One parameter that has not been adequately investigated in the past is the effect of tension on the mechanical functioning of the prosthesis. Our goal was to investigate this parameter further, with the hypothesis that the mechanical functioning of partial ossicular replacement prostheses (PORP) from the stapes head to the eardrum will be affected by the tension that they are placed under.

Is duration tuning a transient process in the inferior colliculus of guinea pigs

Duration selectivity appears to be a fundamental neural encoding mechanism found throughout the animal kingdom. Previous studies reported that band-pass duration-tuned neurons typically show offset responses and occupy a small portion of auditory neurons in non-echolocation mammals relative to echolocation bats. Therefore, duration tuning is generally weaker in non-echolocation mammals. In the present study, duration tuning was analyzed for 207 neurons recorded in the inferior colliculus (IC) of guinea pigs. Duration tuning was found to be stronger in the onset component of the responses from sustained, on-off and pause neurons than had been reported previously, when a short analysis window was applied. The need for an appropriate time window for duration tuning analysis was also supported by the fact that the on and off responses from an on-off neuron may show different duration tuning features. Therefore, duration tuning appears to be a transient neural coding process in the IC of guinea pigs. Duration tuning for these types of neurons may have been blurred by the use of a relatively unselective, long window.

How do cartilage and other material overlay over a prosthesis affect its vibration transmission properties in ossiculoplasty

OBJECTIVE: The prosthesis/eardrum interface is often deliberately modified by cartilage overlay, or by soft tissue in-growth. We examined the effects of vibration transmission to the footplate of inserting cartilage of varying sizes, and materials of varying rigidities. STUDY DESIGN AND SETTING: Using fresh human cadaveric temporal bones, stapes vibrations were measured. A partial ossicular reconstruction prosthesis was covered with differing materials and cartilage sizes. Materials used included glass (rigid), cartilage (intermediate), and Merocel® (soft). Cartilage sizes varied in size relative to the prosthesis head. RESULTS: Rigidity of material had little impact. Cartilage size had an impact, with smaller cartilage covers performing best. CONCLUSION: Larger cartilage sizes performed worse. This could be a result of increased tension on the eardrum from larger cartilage size. There is little impact stiffness of interposed material stiffness. SIGNIFICANCE: Cartilage of the size used clinically has little impact on vibration transmission to the footplate. A wide range of materials could clinically be interposed over the prosthesis.

High-Frequency Ex vivo Ultrasound Imaging of the Auditory System

A 50MHz array-based imaging system was used to obtain high-resolution images of the ear and auditory system. This previously described custom built imaging system (Brown et al. 2004a, 2004b; Brown and Lockwood 2005) is capable of 50 microm axial resolution, and lateral resolution varying from 80 microm to 130 microm over a 5.12 mm scan depth. The imaging system is based on a 2mm diameter, seven-element equal-area annular array, and a digital beamformer that uses high-speed field programmable gate arrays (FPGAs). The images produced by this system have shown far superior depth of field compared with commercially available single-element systems. Ex vivo, three-dimensional (3-D) images were obtained of human cadaveric tissues including the ossicles (stapes, incus, malleus) and the tympanic membrane. In addition, two-dimensional (2-D) images were obtained of an intact cochlea by imaging through the round window membrane. The basilar membrane inside the cochlea could clearly be visualized. These images demonstrate that high-frequency ultrasound imaging of the middle and inner ear can provide valuable diagnostic information using minimally invasive techniques that could potentially be implemented in vivo.

How does Prosthesis Head Size Affect Vibration Transmission in Ossiculoplasty

OBJECTIVES: The transmission of vibrations from the tympanic membrane to the stapes footplate by an ossicular reconstruction prosthesis is affected by the size of the prosthesis head. We sought to determine if augmenting or reducing the head size of prosthesis had a systematic effect on transmission of vibrations to the stapes. STUDY DESIGN: We conducted a fresh cadaveric temporal bone middle ear study. METHODS: The incus was replaced with a prosthesis using a tympanic membrane to stapes head (TASH)-type hydroxyapatite prosthesis in nine fresh cadaveric temporal bones. Three prosthesis head sizes were created: unaltered, reduced, and augmented. Stapes vibrations were measured with a laser Doppler vibrometer in response to acoustic frequency chirps at 90 dB SPL. RESULTS: All three head size prostheses resulted in smaller stapes vibrations than the intact ear. There was no difference in the vibration transmission between the three different head sizes. All prostheses showed a vibration loss of 10 to 15 dB compared to the intact ear. CONCLUSIONS AND SIGNIFICANCE: Within the range of sizes tested, prosthesis head size had little impact on vibration transmission to the stapes footplate.

Effects of tensor tympani muscle contraction on the middle ear and markers of a contracted muscle

Many otologic disorders have been attributed to dysfunction of the tensor tympani muscle, including tinnitus, otalgia, Menieres disease and sensorineural hearing loss. The objective of this study was to determine adequate stimuli for tensor tympani contraction in humans and determine markers of the hypercontracted state that could be used to detect this process in otologic disease.

Cochlear Implantation in Cockayne Syndrome: Our Experience of Two Cases With Different Outcomes

Cockayne syndrome is a rare autosomal recessive defect in DNA repair resulting in a classic facies with potential visual and auditory impairment. The hearing loss begins peripherally and may become central as the condition progresses. Coexisting sensory deprivation from visual impairment and the possibility of progressive deterioration in mental function conspire with a lack of published experience to produce many challenges for the cochlear implant team. To the best of our knowledge, we present the first case reports with documented follow‐up of cochlear implantation in two patients with different manifestations of Cockayne syndrome.

Effects of ossicular prosthesis mass and section of the stapes tendon on middle ear transmission.

BACKGROUND The effects of changing prosthesis mass on middle ear transmission have not been previously systematically studied. Neither has the effect of stapes tendon sectioning. These are important parameters that can be surgically varied. HYPOTHESIS Because the middle ear is compliance dominated at low frequencies, prosthesis mass will affect transmission of higher frequencies in the middle ear. METHODS Eight fresh cadaveric temporal bones, with the incus removed, were loaded with a replacement prosthesis from the tympanic membrane to the stapes head. Laser Doppler vibrometry was used to measure stapes footplate vibrations. Vibrations were measured in response to chirps from 250 to 8 kHz at 90 dB SPL in the ear canal. The unloaded prosthesis mass was approximately 16 mg. Loadings with masses of approximately 2, 12, and 30 mg were placed on the stem. Recordings were repeated after cutting the stapes tendon. RESULTS Mass loading affected the higher frequencies only, with significant effects only above 4 kHz. There was little low-frequency effect. Stapes tendon section showed an improvement in the lower frequencies but did not reach statistical significance. CONCLUSIONS Mass of prostheses affects mainly higher frequencies. There is no drop in lower frequencies from using lower masses, so lighter-mass prostheses may be preferred. Stapes tendon section does not have a detrimental effect on middle ear transmission after ossiculoplasty.

Output vibration measurements of bone-anchored hearing AIDS.

Hypothesis: Different bone-anchored hearing aids (BAHAs) processors have different output vibration characteristics, which depend on the mechanical load and the volume setting. Responses will differ between live heads and dry or plastic skulls. Background: The BAHA is an implantable bone-conduction device. Three different BAHA models are available. Their output vibrations have not been reported using a noncontact method with differing impedance loads, including the BAHA-fitted patient head. Methods: Using a laser-Doppler vibrometer, vibration responses with sound input of 70- to 80-dB sound pressure level were measured on unloaded BAHAs, a dry skull, a plastic skull, and on the abutments of three live BAHA-fitted patients. Responses at different volume settings and distances from the vibrator were also tested. Frequency responses were calculated for displacement, velocity, and acceleration. Results: Unloaded BAHA accelerations were approximately 30 to 50 dB higher than live-head accelerations. Live-head accelerations were similar to dry skulls in frequencies of more than 500 Hz, but much higher than the plastic skull responses. Live-head responses were more damped. The Cordelle II outperformed the other two processors by approximately 20 dB. The Classic 300 had better low-frequency responses than the Compact. The volume settings had little effect on vibration output overall. Acceleration peak was at approximately 2.5 kHz for all conditions. Conclusion: The BAHA processors differ in the output acceleration they can achieve with differing loads. The volume control setting has little impact on accelerations produced for most processors. The live-head responses are similar to the dry skull in frequencies of more than 500 Hz.

Linearity and Lever Ratio of the Normal and Reconstructed Cadaveric Human Middle Ear

Hypothesis The linearity and the level ratio are different in reconstructed ears. Background The linearity of the reconstructed human middle ear (ME) has not been previously explored. It is important to analyze if high sound pressure levels (SPLs) result in distortion due to nonlinearities particularly because hearing aids have high-output SPLs. The diseased ME is reconstructed with prostheses. These diseased ears frequently need additional amplification with hearing aids, and it is unclear if reconstruction itself leads to nonlinear ME responses. Methods Eight fresh human cadaveric temporal bones were used. Pure tones of 70, 90, and 110 dB SPL at 500, 1,000, and 3,000 Hz were presented to the ear canal. Umbo and stapes displacements were measured by means of a laser Doppler vibrometer. After removing the incus, the tympanic membrane assembly to the stapes head prosthesis was placed, and measurements were repeated. Results Stapes footplate vibrations in the reconstructed ears are 10 to 15 dB lower than those of the normal ears. In both normal and reconstructed ears, the footplate vibrations are linearly related to SPL at the tympanic membrane between 70 and 110 dB SPL at the frequencies tested. For the lever ratio, intact ears are more efficient at transmission of umbo vibrations to the stapes compared with reconstructed ears. Conclusion To within acceptable limits, the ME seems to be linear between 70 and 110 dB SPL input levels, across the speech frequencies, and this does not change with reconstruction. The reconstructed human ME seems to have a less efficient lever ratio than the intact ME.