New chamber stapes prosthesis - A preliminary assessment of the functioning of the prototype.

Piston-stapedotomy is the most common method for hearing restoration in patients with otosclerosis. In this study, we have experimentally examined a prototype of a new chamber stapes prosthesis. The prototype was implanted in a human cadaver temporal bone. The round window vibrations before and after implantation were measured for the acoustic signal (90 dB SPL, 0.8-8 kHz) in the external auditory canal. In comparison with a 0.4-mm piston prosthesis, the chamber prosthesis induced significantly higher vibration of the round window, especially for frequencies above 1.5 kHz. Based on the results, it can be surmised that stapedotomy with a chamber stapes prosthesis could provide better hearing results in comparison with the piston-stapedotomy.

Strategy towards independent electrical stimulation from cochlear implants: Guided auditory neuron growth on topographically modified nanocrystalline diamond.

Cochlear implants (CI) have been used for several decades to treat patients with profound hearing loss. Nevertheless, results vary between individuals, and fine hearing is generally poor due to the lack of discrete neural stimulation from the individual receptor hair cells. A major problem is the deliverance of independent stimulation signals to individual auditory neurons. Fine hearing requires significantly more stimulation contacts with intimate neuron/electrode interphases from ordered axonal re-growth, something current CI technology cannot provide. Here, we demonstrate the potential application of micro-textured nanocrystalline diamond (NCD) surfaces on CI electrode arrays. Such textured NCD surfaces consist of micrometer-sized nail-head-shaped pillars (size 5×5µm(2)) made with sequences of micro/nano-fabrication processes, including sputtering, photolithography and plasma etching. The results show that human and murine inner-ear ganglion neurites and, potentially, neural progenitor cells can attach to patterned NCD surfaces without an extracellular matrix coating. Microscopic methods revealed adhesion and neural growth, specifically along the nail-head-shaped NCD pillars in an ordered manner, rather than in non-textured areas. This pattern was established when the inter-NCD pillar distance varied between 4 and 9µm. The findings demonstrate that regenerating auditory neurons show a strong affinity to the NCD pillars, and the technique could be used for neural guidance and the creation of new neural networks. Together with the NCD's unique anti-bacterial and electrical properties, patterned NCD surfaces could provide designed neural/electrode interfaces to create independent electrical stimulation signals in CI electrode arrays for the neural population. STATEMENT OF SIGNIFICANCE: Cochlear implant is currently a successful way to treat sensorineural hearing loss and deafness especially in children. Although clinically successful, patients' fine hearing cannot be completely restored. One problem is the amount of the electrodes; 12-20 electrodes are used to replace the function of 3400 inner hair cells. Intense research is ongoing aiming to increase the number of electrodes. This study demonstrates the use of nanocrystalline diamond as a potential nerve-electrode interface. Micrometer-sized nanocrystalline diamond pillars showed high affinity to regenerated human neurons, which grew into a pre-defined network based on the pillar design. Our findings are of particular interest since they can be applied on any silicon-based implant to increase electrode count and to achieve individual neuron stimulation patterns.

Vibromechanical assessment of active middle ear implant stimulation in simulated middle ear effusion: a temporal bone study.

HYPOTHESIS: Active middle ear implant (AMEI) generated vibromechanical stimulation of the ossicular chain (ossicular chain vibroplasty [OCV]) or the round window (round window vibroplasty [RWV]) is not significantly affected by simulated middle ear effusion in a human temporal bone model. BACKGROUND: OCV and RWV may be employed for sensorineural, mixed, and conductive hearing losses. Although middle ear effusions may be encountered across patient populations, little is known about how effusions may affect AMEI vibromechanical efficiency. METHODS: Laser Doppler vibrometry of stapes velocities (SVs) were performed in a human temporal bone model of simulated effusion (N = 5). Baseline measurements to acoustic sinusoidal stimuli, OCV, and RWV (0.25-8 kHz) were made without effusion. The measurements were repeated with simulated middle ear effusion and compared with baseline measurements. Data were analyzed across 3 frequency bands: low (0.25-1 kHz), medium (1-3 kHz), and high (3-8 kHz). RESULTS: Acoustic stimulation with simulated middle ear effusion resulted in a significant (p < 0.001) frequency-dependent attenuation of SVs of 4, 10, and 7 dB (low, medium, and high ranges, respectively). OCV in simulated effusion resulted in attenuated SVs of 1, 5, and 14 dB (low, medium, and high) compared to without effusion; however, this attenuation was not significant (p = 0.07). Interestingly, in the setting of RWV, simulated effusion resulted in significantly (p = 0.001) increased SVs of 16, 11, and 8 dB (low, medium, and high). A 3-dB variance in AMEI efficiency was observed in repeated measurements in a single temporal bone. CONCLUSION: The efficiency of OCV was not significantly affected by the presence of a middle ear effusion. Improved efficiency, however, was observed with RWV.

Prescriptive proprioceptive insoles and dental orthotics change the frontal plane position of the atlas (C1), mastoid, malar, temporal, and sphenoid bones: a preliminary study.

The purpose of this series of case studies was to determine if the frontal plane position of the cranial bones and atlas could be altered using dental orthotics, prescriptive insoles, or both concurrently. The cranial radiographs of four patients were reviewed for the study. Three of the patients were diagnosed as having a temporomandibular joint (TMJ) dysfunction and a preclinical clubfoot deformity. The fourth patient was diagnosed as having a TMJ dysfunction, a preclinical clubfoot deformity and a Catetgory II sacral occipital subluxation, as designated in the chiropractic's Sacro Occipital Technique (SOT). Each patient had a series of four cranial radiographs taken using a modified orthogonal protocol. In two patients, improvement towards orthogonal was achieved when using both prescriptive dental orthotics and prescriptive insoles concurrently. Improvement towards orthogonal was less apparent when using only the prescriptive dental orthotic. No improvement or a negative frontal plane shift was noted when using only the prescriptive proprioceptive insoles. In the third patient, the frontal plane position of the cranial bones and atlas increased (away from orthogonal) when using the generic proprioceptive insoles alone or in combination with a prescriptive dental orthotic. In the fourth patient, the frontal plane position of the cranial bones improved using the dental orthotic. However, the proprioceptive insoles, when used alone or in combination with the dental orthotic, increased the frontal plane position of the cranial bones and atlas. This study demonstrates that changes in the frontal plane position of the cranial and atlas bones can occur when using proprioceptive insoles and/or dental orthotics.

Clinical use of vestibular evoked myogenic potentials in the evaluation of patients with air-bone gaps.

OBJECTIVE: To determine the value of vestibular evoked myogenic potential (VEMP) test in clinical evaluation of air-bone gaps. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: A total of 120 patients underwent VEMP testing during clinical investigation of significant air-bone gaps in their audiograms. INTERVENTION(S): Otologic examination and surgeries, high-resolution computerized tomography (CT), air and bone audiometry, tympanometry, acoustic reflex, and VEMP test. MAIN OUTCOME MEASURE(S): Imaging studies demonstrating structural anomalies in the temporal bone. Audiologic outcomes of air-bone gaps and VEMP thresholds. Surgical findings confirming imaging results. RESULTS: Middle ear pathologies, such as otosclerosis and chronic otitis media, were identified in 50 patients, and all of them had absent VEMP responses elicited by air-conduction stimuli. Moreover, 13 of them had successful middle ear surgeries with closures of the air-bone gaps. Abnormally low VEMP thresholds were found in 71 of 73 ears with inner ear anomalies, such as semicircular canal dehiscence and enlarged vestibular aqueduct. Seven patients with superior semicircular canal dehiscence underwent plugging procedure via middle fossa approach, and VEMP thresholds became normalized after the surgery in 3 of them. VEMP test failed to provide accurate diagnosis in only 3 cases. CONCLUSION: Air-bone gaps may be a result of various otologic pathologies, and the VEMP test is useful during clinical evaluation, better than tympanometry and acoustic reflexes. To avoid unnecessary middle ear surgery for air-bone gaps with unknown or unsure cause, VEMP test should be used in the differential diagnosis before an expensive imaging study.

Eagle syndrome revisited: cerebrovascular complications.

Cervical pain caused by the elongation of the styloid process (Eagle syndrome) is well known to otolaryngologists but is rarely considered by vascular surgeons. We report two patients with cerebrovascular symptoms of Eagle syndrome treated in our medical center in the past year. Case 1: an 80-year-old man with acromegaly presented with dizziness and syncope with neck rotation. The patient was noted to have bilateral elongated styloid processes impinging on the internal carotid arteries. After staged resections of the styloid processes through cervical approaches, the symptoms resolved completely. Case 2: a 57-year-old man presented with acute-onset left-sided neck pain radiating to his head immediately after a vigorous neck massage. Hospital course was complicated by a 15-minute transient ischemic attack resulting in aphasia. Angiography revealed bilateral dissections of his internal carotid arteries, with a dissecting aneurysm on the right. Both injuries were immediately adjacent to the bilateral elongated styloid processes. Despite immediate anticoagulation therapy, he experienced aphasia and right hemiparesis associated with an occlusion of his left carotid artery. He underwent emergent catheter thrombectomy and carotid stent placement, with near-complete resolution of his symptoms. Elongated styloid processes characteristic of Eagle syndrome can result in both temporary impingement and permanent injury to the extracranial carotid arteries. Although rare, Eagle syndrome should be considered in the differential diagnosis in patients with cerebrovascular symptoms, especially those induced by positional change.

Prosthetic reconstruction from the tympanic membrane to the stapes head or to the stapes footplate? A laser Doppler study.

BACKGROUND: In the absence of the incus, many surgeons believe that reconstruction from the tympanic membrane to the stapes head is more effective than reconstruction to the stapes footplate. This has rarely been tested empirically. Published better clinical results with reconstruction to the stapes head might simply reflect less underlying disease in ears with an intact stapes superstructure. OBJECTIVE: To compare vibration transmission of these two forms of prosthetic reconstruction. METHODS: A fresh human cadaveric temporal bone model was used. Round window vibrations in response to sound in the ear canal were measured with a laser Doppler vibrometer. After incus removal, the discontinuity was repaired using a titanium prosthesis. Reconstruction from the tympanic membrane to the stapes head was compared to reconstruction to the stapes footplate. RESULTS: Reconstruction of both types decreased round window vibrations by 10 to 15 dB between 500 and 3000 Hz compared to the intact middle ear. Reconstruction to the stapes head performed 5 to 10 dB better at lower frequencies (500-2000 Hz), but this was only statistically significant at 1 and 2 kHz. CONCLUSIONS: There is only a 5 to 10 dB mechanical advantage gained by reconstruction from the tympanic membrane to the stapes head compared to reconstruction to the footplate for frequencies between 1 and 2 kHz.

Moderate cochlear hearing loss leads to a reduced ability to use temporal fine structure information.

The ability of normally hearing and hearing-impaired subjects to use temporal fine structure information in complex tones was measured. Subjects were required to discriminate a harmonic complex tone from a tone in which all components were shifted upwards by the same amount in Hz, in a three-alternative, forced-choice task. The tones either contained five equal-amplitude components (non-shaped stimuli) or contained many components, but were passed through a fixed bandpass filter to reduce excitation pattern changes (shaped stimuli). Components were centered at nominal harmonic numbers (N) 7, 11, and 18. For the shaped stimuli, hearing-impaired subjects performed much more poorly than normally hearing subjects, with most of the former scoring no better than chance when N=11 or 18, suggesting that they could not access the temporal fine structure information. Performance for the hearing-impaired subjects was significantly improved for the non-shaped stimuli, presumably because they could benefit from spectral cues. It is proposed that normal-hearing subjects can use temporal fine structure information provided the spacing between fine structure peaks is not too small relative to the envelope period, but subjects with moderate cochlear hearing loss make little use of temporal fine structure information for unresolved components.

Multifield coupled finite element analysis for sound transmission in otitis media with effusion.

In this paper, a newly constructed three-dimensional finite element (FE) model of the human ear based on histological sections of a left ear temporal bone is reported. The otitis media with effusion was simulated in the model with variable fluid levels in the middle ear. The interfaces among the air, structure, and fluid in the ear canal and middle ear cavity were identified and the acoustic-structure-fluid coupled FE analysis was conducted when the middle ear fluid level was varied from zero to full fill of the cavity. The results show how the displacements of the tympanic membrane and stapes footplate or the middle ear transfer function is affected by fluid in the cavity across the auditory frequencies. Comparison of model results with measured data in temporal bones indicates that this model has the capability to extend FE analysis into pathological ears such as otitis media with visualized fluid-air interfaces inside the middle ear structures.

Osteoprotegrin knockout mice demonstrate abnormal remodeling of the otic capsule and progressive hearing loss.

OBJECTIVES: The otic capsule, when compared with other bones in the body, is unique in that it undergoes no significant remodeling of bone after development. We previously demonstrated that osteoprotegerin (OPG), which inhibits formation and function of osteoclasts, is produced at high levels in the inner ear of normal mice and secreted into the perilymph from where it diffuses into the surrounding otic capsule bone through a lacunocanalicular system. To test our hypothesis that the high level of OPG may be important in the inhibition of otic capsule remodeling, we studied the light microscopic histology of the otic capsule in OPG knockout mice for evidence of abnormal remodeling of bone. We also tested the hearing in OPG knockout mice to determine whether OPG and its influence on surrounding bone is important for auditory function. METHODS: Temporal bone histopathology and pathophysiology were compared in homozygous OPG knockout mice and C57BL/6 (B6) mice, the background strain for the knockouts. Auditory function in age-matched animals from each group was evaluated at approximately 4-week intervals from 8 to 21 weeks using frequency-specific auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE). After each of the last three evaluations, the cochleae from one mouse of each group were harvested, processed, and examined by light microscopy. RESULTS: Osteoprotegerin knockout mice demonstrated abnormal remodeling of bone within the otic capsule with multiple foci showing osteoclastic bone resorption and formation of new bone. Such changes were not seen in the age-matched B6 controls. The active bone remodeling process in the knockout animals showed many similarities to otosclerosis seen in human temporal bones. Over the time period that we monitored, auditory function was significantly and progressively compromised in the knockout animals relative to B6 controls. At the earliest age of test (8 wk), the loss was apparent as a mild, high-frequency reduction in sensitivity by ABR. In contrast, DPOAE losses in the knockouts were substantial even at 8 weeks, and by 21 weeks, these losses exceeded our equipment limits. Results of ABR testing showed hearing sensitivity changes in the animals of the background strain were confined largely to the high frequencies, whereas OPG knockouts demonstrated substantial low-frequency shifts in addition to those at high frequencies. CONCLUSIONS: The histopathological and pathophysiological findings in OPG knockout mice support the hypothesis that OPG is important in the inhibition of bone remodeling within the otic capsule and the maintenance of normal auditory function. This mouse may provide a valuable animal model of human otosclerosis.

Dynamics of middle ear prostheses - simulations and measurements.

The efficient and systematic development of a middle ear prosthesis necessitates the use of computer models for the prosthesis itself and the reconstructed middle ear. The structure and parameters of the computer model have to be verified by specific measurements of the implant and the reconstructed ear. To obtain a realistic model of a reconstructed ear, three steps of modeling and measurements have been carried out. To get a first approach of the coupling elements a mechanical test rig representing a simplified reconstructed middle ear was built. The velocity of the stapedial footplate was measured with a laser Doppler vibrometer. The corresponding computer model was formulated, and the respective parameters were determined using the measured dynamical transfer functions. In the second step, a prosthesis was implanted into a human temporal bone without inner ear. Exciting this system with noise, the velocity of the stapes footplate was measured with the laser Doppler vibrometer. Based on the multibody system approach, a mechanical computer model was generated to describe the spatial motions of the reconstructed ossicular chain. Varying some significant parameters, simulations have been carried out. To describe the dynamical behavior of the system consisting of middle and inner ear, the computer model used in the second step has been enlarged by adding a simplified structure of the inner ear. The results were compared with in situ measurements taken from living humans.

Acoustic effect of malleus head removal and tensor tympani muscle section on middle ear reconstruction.

In the reconstruction of ears with a missing incus, an incus replacement prosthesis (IRP) is commonly used to connect malleus and stapes. In some cases, it is necessary to resect the malleus head and/or section the tensor tympani muscle (TTM) tendon. The acoustic effects of these maneuvers have not been well studied. We performed experiments in a temporal bone model to measure the effect of these maneuvers on middle ear sound transmission. Measurements of umbo and stapes displacement were made before and after malleus head removal and TTM section plus incus replacement with an IRP. After malleus head removal, there was a peak gain in stapes displacement of 6 dB below 0.5 kHz and 8 dB above 2.5 kHz. TTM section had a similar but lesser effect. A clinical example is described.

A simultaneous comparison of acupuncture needle and insulated needle sphenoidal electrodes for detection of anterior temporal spikes.

Uninsulated acupuncture needles have been used as sphenoidal electrodes, but the issue of insulation has not been adequately addressed. In this report, acupuncture needles and insulated needle sphenoidal electrodes were simultaneously used to compare the rate of spike detection, spike amplitude and distribution of maximal spikes from eight spike foci in seven patients with temporal lobe epilepsy. When compared to the insulated needle electrode, the acupuncture needle electrode was equally effective in spike detection, but spike amplitudes tended to be smaller and maximal spikes were less frequently encountered. Thus, insulation has an influence on the spikes recorded by the acupuncture needle sphenoidal electrode. However, the overall effect appears to be not sufficiently different from the insulated needle electrode for the purpose of detecting anterior temporal spikes in outpatient EEG recordings for the diagnosis of temporal lobe epilepsy.