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PubMed1997

Bone conduction implants for amplification: comparison of results.

We compared the results from the North American patient database on the Xomed Audiant Bone Conductor to those reported on the NobleBiocare (previously Noblepharma) HC200 bone-anchored hearing aid (BAHA) implant, using the literature and specific results provided by one of the authors. It has been proposed that the percutaneous coupling of the NobleBiocare implant transduces energy more powerfully than the Audiant transcutaneous coupling. If true, percutaneous coupling could provide greater amplification, helping patients experiencing both conductive and sensorineural hearing loss. Aided sound-field thresholds corresponding to bone-conduction thresholds were compared retrospectively through the speech frequencies. Both the BAHA and the Audiant devices amplified in the sound field to approximate preoperative bone-conduction thresholds. No statistically significant differences existed between the amplification of warble tones through the speech frequencies for either device. We conclude that amplification with the Audiant device offers as much gain as the HC200 device through the speech frequencies. While both devices can supply effective amplification for select patients suffering from conductive hearing loss, neither provides gain superior to preoperative bone-conduction thresholds to address the needs of select patients with a substantial sensorineural component.

Adult↗
PubMed1998

Bone-conduction amplification with completely-in-the-canal hearing aids.

Recent advances in miniaturization have provided clinicians with hearing aids that can be comfortably inserted as far as the bony portion of the ear canal. It is possible to take advantage of these deeply inserted hearing aids in new ways. For example, the physical vibrations of microphone and receiver components may be used to improve hearing aid gain through bone conduction. Three cases are presented that will introduce this phenomenon for two transcranial CROS fittings and for one unilateral otosclerosis fitting. In each case, functional gain measurements under headphones were obtained with the hearing aid receivers acoustically plugged. Considerable gain was still present. Potential benefits, ramifications, and side effects are discussed.

Adult↗
PubMed1991

High-frequency audiometry. Accelerometric findings with electric bone-conduction audiometry.

The skull vibrations induced by an electrical high-frequency audiometer (Audimax 500) were measured with a sensitive accelerometer in 5 subjects. The measurements included the maximum output levels, the equivalent threshold force level (ETFL) decreases, the distortions over the whole frequency range (0.5-20 kHz) of the audiometer and the effect of different electrode positions. The results showed that there is a real bone-conduction effect with this audiometer throughout the high-frequency range with the different electrode positions. The mean maximum output level ranged between 60 and 70 dB ETFL in the high-frequency range. The ETFL decrease was of the same order, irrespective of the frequency, but the differences in the maximum output levels at different frequencies necessitate a frequency-dependent additive correction so that the equal hearing level at each frequency can be achieved. When the electrodes were placed on both mastoids, the second harmonic distortions were found only at signal frequencies of 2 and 4 kHz. At the other electrode positions the distortions were increased, however, not being audible.

Adult↗
PubMed1995

Lipid extracted bank bone. Bone conductive and mechanical properties.

Lipid extraction by chloroform methanol previously has been found to increase the incorporation of frozen bone allografts. This effect may be because of a decreased immunologic response. In the present study, the ingrowth capacity into a grafted bone defect was investigated by using the bone harvest chamber model in rabbits. In a series of experiments, defatted and frozen allografts were compared at 1, 2, and 3 weeks; defatted allografts and defatted autografts were compared at 3 weeks; and frozen or defatted allografts and nongrafted defects were compared at 3 weeks. Evaluation was performed through histology, histomorphometry, and 99mTc-MDP scintimetry. The incorporation was better with defatted grafts: by histology at 1 week, mesenchymal tissue filled the intertrabecular space in defatted specimens and new bone formation started to occur. In contrast, frozen specimens showed a central soft tissue necrosis surrounded by inflammatory cells. Histomorphometry showed more new bone and more graft resorption in defatted allografts. At 2 and 3 weeks, there was no significant difference in new bone area, but at 3 weeks the scintimetric activity was higher in defatted allografts, probably caused by an increased remodeling rate. Since defatting did not cause increased scintimetric activity in previous autograft studies, these findings could indicate that there is a detrimental immunologic influence on frozen allografts. There were no differences between defatted autografts and allografts. In a second experiment, the biomechanical properties of defatted bone were investigated with a compression test on defatted and frozen bone cylinders taken from the calf femoral neck. No difference in biomechanical properties was found. It was concluded that lipid extraction produced a graft that was better incorporated than a nondefatted graft, with no loss of mechanical function.

Animals↗
PubMed1989

Are seismic communication signals transmitted by bone conduction in the blind mole rat?

The anatomy of the middle ear of the blind mole rat, a subterranean rodent that uses seismic signals for long distance communication, is described qualitatively and quantitatively. The ossicular chain is of the parallel type with a lever arms ratio of 0.55 and an effective areal ratio of stapedial footplate to eardrum of 0.09. Assuming an ideal mechanical transform, the calculated fraction of acoustical energy theoretically transmitted to the cochlea, indicate low efficiency for airborne sounds. This is in accordance with the relatively high electrophysiological and behavioral threshold, shown previously. We suggest that a unique morphology of the middle ear and of the articulation between the lower jaw and the skull, as well as a peculiar 'jaw listening behavior' enable seismic vibrations to be transmitted to the inner ear mainly by bone conduction, thereby compensating for the limitation in receiving airborne signals.

Animals↗
PubMed1982

Bone-conduction force values for the sensorineural acuity level (SAL) test.

The sensorineural acuity level (SAL) test has the advantages of eliminating the questions of when to mask and how much masking to use in audiometry, greater efficiency in assessing cochlear sensitivity than conventional bone-conduction (bc) testing, and fewer and less serious errors in measuring cochlear sensitivity. However, a major limitation of the SAL test is that norms are generally determined using the time-consuming real-ear calibration method. A more satisfactory procedure is to establish normative force levels using an artificial mastoid. Normal-hearing young adults (N:18) were tested with pure tones and with spondees, in the presence of bc white noise delivered to a Radioear B-70-AA vibrator and calibrated with a Bruel & Kjaer 4930 artificial mastoid. Force levels in db re 1 mu Newton found to produce a 30-db HTL in bc white noise were: 104, 94, 94, 94, and 100 for tones of .5, 1, 2, and 4 kc/s, and for spondees, in that order. Force levels for narrow bands of noise centered at .5, 1, 2, and 4 kc/s were 104, 84, 76, and 86 db in that order. Clinicians are cautioned to use these force values with reservation unless their bone vibrator, artificial mastoid, and noise spectra are similar to those used in the present study. If clinics choose to obtain their own baseline data, artificial mastoid measures can still serve as a convenient reference to monitor equipment stability. The use of the SAL is urged as part of a test battery for assessing the presence and degree of conductive pathology.

Adult↗
PubMed2003

Hearing protection: surpassing the limits to attenuation imposed by the bone-conduction pathways.

With louder and louder weapon systems being developed and military personnel being exposed to steady noise levels approaching and sometimes exceeding 150 dB, a growing interest in greater amounts of hearing protection is evident. When the need for communications is included in the equation, the situation is even more extreme. New initiatives are underway to design improved hearing protection, including active noise reduction (ANR) earplugs and perhaps even active cancellation of head-borne vibration. With that in mind it may be useful to explore the limits to attenuation, and whether they can be approached with existing technology. Data on the noise reduction achievable with high-attenuation foam earplugs, as a function of insertion depth, will be reported. Previous studies will be reviewed that provide indications of the bone-conduction (BC) limits to attenuation that, in terms of mean values, range from 40 to 60 dB across the frequencies from 125 Hz to 8 kHz. Additionally, new research on the effects of a flight helmet on the BC limits, as well as the potential attenuation from deeply inserted passive foam earplugs, worn with passive earmuffs, or with active-noise reduction (ANR) earmuffs, will be examined. The data demonstrate that gains in attenuation exceeding 10 dB above the head-not-covered limits can be achieved if the head is effectively shielded from acoustical stimulation.

Auditory Threshold↗
PubMed1988

Delayed oto-acoustic emissions evoked by bone-conduction stimulation: experimental data on their origin, characteristics and transfer to the external ear in man.

1) BCEOE have been obtained in subjects with normal hearing by 1 kHz tone-bursts; 2) the morphology of BCEOE varies from one subject to another, and is stable over the course of time. BCEOE do not display a linear relation between their amplitude and the intensity of the stimulus, whose spectral composition is the same as theirs; 3) by contrast with ACEOE, whose mean threshold is the same as that of the subjective tonal threshold for the same stimulus presented by the same stimulation modality, BCEOE threshold, on overage, is about 10 dB HTL higher; 4) this difference in threshold is not due to interference on the part of the controlateral ear, via the efferent fibres, since it is also observed in persons with unilateral anacusis. It is probably the outcome of unilateral competitive inhibition between two stimuli presented to the same ear at the same time. By bone-conduction stimulation in fact, when the meatus is occluded by the probe, as in our experimental situations, Corti's organ is reached by a supplementary contingent of mechanical energy generated by the vibration of the bony part of the meatus and transmitted by air conduction; 5) ACEOE cannot be obtained in otosclerotic subjects whereas they appear after surgery. BCEOE are obtained before surgery and increase in amplitude post-operatively; 6) the findings mentioned in point 5) clearly demonstrate that the ossicular chain plays an important, but not an essential role in the transfer of EOE from the inner to the external ear.

Acoustic Stimulation↗
PubMed1995

Paired comparisons between the Classic 300 bone-anchored and conventional bone-conduction hearing aids in terms of sound quality and speech intelligibility.

Fourteen experienced users of bone-anchored hearing aids conducted paired comparisons of sound quality and speech intelligibility for 6 and 4 different stimuli respectively in the Classic 300 and a bone-conduction hearing aid with a steel clip. Ten paired comparisons were made for each stimulus. The patient selected the best hearing aid and rated the chosen hearing aid on a scale of 'somewhat better', 'better' and 'much better'. The Classic 300 obtained a positive assessment in terms of sound quality and speech intelligibility far more frequently. All the patients chose the Classic 300 as the best hearing aid when they assessed the sound quality of the classical music stimulus.

Adult↗
PubMedDate not supplied

Densitometry of the cochlear capsule and correlation between bone density loss and bone conduction hearing loss in otosclerosis.

Radiodensity of the bony cochlear capsule was investigated by CT-scanning in 134 ears with otosclerosis and 35 normal control ears. A technique of densitometry of the cochlea was developed comprising the measurement of maximum and minimum density together with mapping of the cochlea and measurement of the density at six predefined points in the cochlear capsule. Bone density in the normal cochlea showed very little interindividual variation. In the otosclerosis patients, minimum density was decreased in 58% of the ears, indicating the presence of a focus. At visual examination, foci were only detectable when density loss exceeded 200 Hounsfield. A positive correlation was found between bone density loss and bone conduction hearing loss with a maximum at 2,000 Hz and the medioventral point of the cochlear wall. The method appears to be useful for the follow-up during fluoride treatment, as is demonstrated by a case report.

Cochlea↗
PubMed2005

Vestibular-evoked extraocular potentials produced by stimulation with bone-conducted sound.

OBJECTIVE: To investigate the origin, whether ocular or extraocular, of the short latency frontal potential (N15) reported by following vestibular stimulation. METHODS: Fourteen subjects with low VEMP thresholds (V(T)) and 9 patients with vestibular or ocular disorders were stimulated at the mastoid with bone-conducted tone bursts (500 Hz, 8 ms) above vestibular threshold, using a B71 bone vibrator. Surface potentials were recorded from Fpz and around the eyes and referred to linked earlobes. RESULTS: The N15 was present at Fpz, but was largest around the eyes (mean amplitude 2.6 microV, peak latency 13.4 ms, with stimulation at +18 dB above threshold) and was generally in phase above and below the eyes. The response was vestibular-dependent and modulated by alteration of gaze direction. The potentials were delayed in a patient with Miller Fisher syndrome and were larger in patients with superior canal dehiscence than in controls. CONCLUSIONS: We report a new vestibular-evoked extraocular potential. Its properties are not consistent with an eye movement. It is likely to be produced, mainly or exclusively, by synchronous activity in extraocular muscles (i.e. a myogenic potential). SIGNIFICANCE: Vestibular-evoked extraocular potentials extend the range of vestibular pathways that can be assessed electrophysiologically, and may be a useful additional test of vestibular function.

Adult↗