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PubMed2004

Bone conduction auditory brainstem responses in infants.

The contribution of air conduction auditory brainstem response (AC-ABR) testing in the paediatric population is widely accepted in clinical audiology. However, this does not allow for differentiation between conductive and sensorineural hearing loss. The purpose of this paper is to review the role of bone conduction auditory brainstem responses (BC-ABR). It is argued that despite such technical difficulties as a narrow dynamic range, masking dilemmas, stimulus artifact and low frequency underestimation of hearing loss, considerable evidence exists to suggest that BC-ABR testing provides an important contribution in the accurate assessment of hearing loss in infants. Modification of the BC-ABR protocol is discussed and the technical difficulties that may arise are addressed, permitting BC-ABR to be used as a tool in the differential diagnosis between conductive and sensorineural hearing. Two relevant case studies are presented to highlight the growing importance of appropriate management in early identification of hearing loss. It can be concluded that BC-ABR should be adopted as a routine clinical diagnostic tool.

Bone Conduction↗
PubMed1990

Percutaneous vs. transcutaneous transducers for hearing by direct bone conduction.

There is a substantial need for improvement of the hearing situation for patients, with chronic middle ear or ear canal disorders. To improve hearing for these patients, two different bone conduction hearing systems have been developed. The Nobelpharma Auditory System HC 200-the bone-anchored hearing aid we present here-uses a percutaneous transducer; whereas the Audiant device, developed by Dr. Jack Hough, uses a transcutaneous transducer. In percutaneous transmission, the transducer is directly coupled to the bone by means of a permanent skin penetration, whereas in transcutaneous transmission one part of the transducer is implanted and the other part is kept outside the intact skin and soft tissue. Comprehensive audiologic assessments indicate great differences in performance between the two systems. These differences probably originate in differences in length of gap and in different suspension properties of the two transducer systems. This article will demonstrate that large gaps, such as in the transcutaneous transducer, can be devastating for power consumption, maximum output capability, and second harmonic distortion. Since the properties of the suspension in the transcutaneous transducer are not under adequate control and the complication risk of permanent skin penetration is low, we continue to concentrate our efforts on percutaneous transducer systems.

Bone Conduction↗
PubMed1985

[Changes in bone conduction in the surgery of chronic otitis and its sequelae (evaluation of 800 operations)].

The authors undertook a study of changes in bone conduction (BC) during 800 operations carried out over a 5 years period (1979-1984) for chronic otitis or sequelae of chronic otitis. After elimination of ears with deafness (47) and cases unsuitable for evaluation (39), they finally included 714 records in the study. Only comparison of free and post-operative BC was made and using 4 conversational frequencies, not taking into account a deviation of 5 DB for each of these 4 frequencies. The study involved 317 myringoplasties: In 271 (i.e. 85,5%) there was no change in BC. Amongst them, 37 patients nevertheless showed a transient fall in BC. Of particular importance is the fact that almost 1/3 (11 to be exact) recovered only during the 2nd semester following surgery, a period which was even exceeded in the other 5 cases. 46 (i.e. 14.5%) were classified as "permanent" falls in BC. Amongst these in only 17 (i.e. 5%) were there "only" the three standard aggression factors for the I.O.: aspiration--scraping--manipulation of the tympano-ossicular system, without it being possible to attribute a predominant role to one more than the other. With regard to reaming of the E.A.M., those cases in which this could be considered responsible appeared to be infinitesimal. Furthermore, there was no statistically significant difference (reduced deviation test--"chi"2 test) between the number of falls in BC seen following myringoplasty with or without reaming. 83 tympanoplasties by Piston-Malleus, study of which led to the same conclusions as for myringoplasties. 118 masto-atticotomies, including 23 with posterior tympanotomy. Despite peri-labyrinthine and peri-ossicular scraping, results were essentially identical. 196 evacuation cavities (227-31 deafness) of which somewhat less than half only (46%) were ears undergoing surgery for the first time. Percentage of unchanged BC was here much more unfavourable, with 49 "permanent" falls in BC, i.e. 25%, of which, it must be said, 5 were minimal falls, and with, in 25 cases, a follow-up of less than 3 months.

Bone Conduction↗
PubMed1977

Bone conduction speech discrimination: an indication of cochlear function in the immediate postoperative period.

We illustrate that the apparent sensorineural audiometric changes immediately following stapedectomy are not indicative of a true sensorineural type hearing loss. The cochlear changes evident by postoperative pure-tone and air conduction speech discrimination audiometric tests are not reflective of the true cochlear reserve when the procedure of bone conduction speech discrimination is used. We report 25 consecutive stapedectomy cases in which most of the one-week postoperative audiograms of stapedectomized ears revealed a mid- and high-frequency sensorineural pure-tone loss and a drop in the standard speech discrimination scores. The decrease in speech discrimination, however, was not verified when using the bone-speech discrimination test, using maximum masking in the opposite ear.

Audiometry↗
PubMed1988

An implantable bone conduction hearing device.

A new implantable hearing device that transmits an acoustical signal from an external electromagnetic coil to a small magnet implanted in the temporal bone has been developed and implanted in more than 350 patients. Animal research indicates that the device serves as a high-fidelity sound source throughout the audio range. Especially notable is its high-frequency performance. Human experiments using a body processor indicate that the device compares favorably with conventional bone conduction hearing aids, and patients report excellent sound quality as well as improved ability to understand conversational speech. Further development has resulted in an at-the-ear (ATE) processor. Extensive testing of the ATE unit has revealed that current models provide approximately 10 dB less output than the body processors. Further research and development are continuing to address the need for increased power output from the ATE processor and to eliminate other minor problems.

Adult↗
PubMed1985

Intraosseous transducers for hearing by bone conduction. Peroperative measurements.

Now that it is possible to establish and maintain a reaction free skin penetration, there are new prospects for hearing through bone conduction. Peroperative hearing threshold measurements on patients entering hospital for ear surgery under local anaesthesia have been made. An electromagnetic transducer was temporarily cemented into the cortex of the mastoid process and the transducer current for threshold signals at different frequencies recorded. Considerable variability was found between patients but a distinct common pattern from 0.25 kHz to 8 kHz could be identified in the audiograms. With the transducers used, the power consumption was found to be low (1 mW) at threshold levels but to achieve a comfortable hearing level the electrical power needed was found to be as high as 4W.

Auditory Threshold↗
PubMed2000

Time-dependent sensory nerve ingrowth into a bone conduction chamber.

We studied time-dependent ingrowth of sensory nerve fibers into a bone defect in a rat bone conduction chamber model. In 10 male Sprague Dawley rats, a titanium chamber was implanted bilaterally in the proximal tibiae, representing an experimental bone defect. To mimic a clinical situation, the chambers were filled with a fresh blood clot After 1, 2, 4, 6 and 8 weeks, 2 rats were fixed in vivo at each time before removal of specimens, and histological and immunohistochemical analyses. We used antisera against protein gene product 9.5, neural growth-associated protein 43/B-50, calcitonin gene-related peptide, and substance P, to locate regenerating sensory nerve fibers in the chamber. During bone defect healing, hematoxylin/eosin sections showed that new bone grew in through the ingrowth openings in the chamber, gradually filling it and replacing the blood clot. At 1 and 2 weeks after implantation, no nerve fibers could be detected. At 4, 6 and 8 weeks, however, small numbers of nerve fibers were seen in 8 of 11 specimens. The nerve fibers were located mainly in the dense fibrous tissue in close proximity to the new bone, and in some cases within the new forming bone. In this chamber model, the periosteum is not in contact with the bone ingrowth openings, and all ingrowing nerve fibers thus originated from the cortical bone, endosteum or bone marrow. We speculated that these late ingrowing sensory nerve fibers may actively participate in bone repair.

Animals↗
PubMed1984

Vibrotactile threshold for hairy skin and its transformation into equivalent bone-conduction loss for the mastoid.

Vibrotactile thresholds for the glabrous skin of the hand and for the hairy skin of the arm are investigated as a function of frequency in the range from 40 to 2 000 Hz, using a heavy vibrator. These thresholds are expressed as equivalent bone-conduction loss and compared with vibrotactile thresholds determined with bone vibrators on the arm and mastoid for normally hearing and severely hearing-impaired subjects. The results are used to predict the vibrotactile threshold of the hairy skin of the mastoid under conditions of severe hearing impairment and deafness. The frequency characteristics of a number of vibrators are discussed with respect to their suitability for skin stimulation.

Adolescent↗
PubMed1995

Tentative age-related norms for high frequency electric bone conduction audiometry.

From 172 male and female patients aged 7-71 years old and admitted in one month to a tuberculosis hospital, 150 had their highest audible electric bone conduction (EBC) frequency evaluated, prior to the commencement of any medical treatment. Various problems in establishing high frequency norms are discussed and from the results of this study tentative age-related highest frequency EBC norms are suggested. Possible clinical applications of evaluating the highest audible EBC frequency is suggested.

Adolescent↗
PubMed1981

Velocity of propagation of bone-conducted sound in a human head.

A psychophysical cancellation method after Zwislocki [J. Acoust. Soc. Am. 25, 752-759 (1953)] was used to measure the propagation velocity of bone-conducted sound across the head of an observer. The result, 330 m/s, compares quite well with Zwislocki's earlier value of 260 m/s and Franke's of 300 m/s. Since in all three experiments the velocity was frequency-independent at f greater than 2000. Hz, it is suggested that vibratory energy travels along the flat bones of the cranial vault in the form of plate waves and as distortional waves through its base. [As defined by Cremer and Heckl, Körperschall (Springer, Berlin, 1967), plate waves are but a simpler form of distortional waves.] Quantitatively, the present result appears quite reasonable in the light of the material constants involved and by comparison with other materials.

Bone Conduction↗
PubMed1998

Radio frequency hearing: electrostrictive detection and bone conduction.

A hearing aid patented by C. R. Schafer and supposedly based on detection of an amplitude-modulated carrier wave in the auditory cortex was re-examined. It is shown here that the hearing aid actually works by bone conduction of sound. It is concluded that detection of the modulation signal occurs by electrical nonlinearities and electrostriction in the bones of the face and skull.

Bone Conduction↗
PubMed1994

Sound pressure in the external auditory canal during bone-conduction testing.

Sound pressure levels (SPLs) were measured in the external auditory canals (EACs) of 16 subjects with normal hearing and normal middle ear immittance. SPLs were the result of bone-conduction (BC) stimulation at 500, 1000, 2000, and 4000 Hz, with the oscillator placed either on the forehead or on the mastoid process. At 1000, 2000, and 4000 Hz, significantly higher SPLs were measured when the head was stimulated from the mastoid than from the forehead. When SPLs were compared between right and left EACs, forehead placement of the oscillator produced no interaural differences, while mastoid placement resulted in significantly greater EAC SPLs ipsilateral to the oscillator at 2000 and 4000 Hz. We conclude that forehead placement of a BC vibrator may help to lessen the (unwanted) contribution of the EAC to measurements of hearing sensitivity by BC.

Audiometry, Pure-Tone↗
PubMed1999

[Acute otitis media associated with bone conduction hearing loss].

Eleven patients (12 ears) with acute otitis media associated with raised bone conduction were studied. The patients were from 19 to 70 years old and came to our hospital between November 1996 through May 1997. Pure tone audiometry revealed mixed hearing loss, but there was no bullous myringitis in all cases. They were treated by oral or intravenous antibiotics, steroids, and myringotomy. Bacteriological examination was done in seven cases, and revealed penicillin resistant Streptococcus pnumoniae in three cases. Complete recovery of hearing loss was obtained in 10 of 12 ears, but sensorineural hearing loss remained in 2 patients. Bacteriological examination and pure tone audiometry in acute otitis media are important for detecting the severity of the disease, determining the administration of steroids, and for the selection of antibiotics.

Acute Disease↗
PubMed1997

Hearing sensitivity in newborns estimated from ABRs to bone-conducted sounds.

This study focused on the problem of estimating hearing sensitivity in newborns from auditory brainstem responses (ABRs) evoked by clicks and 500 Hz and 4000 Hz tonebursts presented by a bone-conduction (BC) oscillator. The effects of acoustic energy transmitted to the ear canal, gender, and ear differences were also investigated. ABR thresholds for BC stimuli were 56, 52, and 53 dB (re 1 microN) or -5, -14, and 0 dB nHL (re adult psychophysical threshold) for click and 500 Hz and 4000 Hz tonebursts, respectively. For newborns, ear canal SPLs generated by the BC stimuli were as much as 21 dB greater than those in adults. Gender-related threshold differences were significant, with female infants having lower thresholds than males; however, ear differences were not. The findings of this study can be used to set appropriate BC stimulus levels for screening or assessment of newborns.

Auditory Threshold↗
PubMed1979

Long-term effect of otosclerosis on bone conduction.

There have not been many studies of long-term sensorineural function in otosclerosis. The reports of long-term follow-up of lateral canal fenestration cases show a surprising stability of bone conduction. Because the experience of the senior author in stapes surgery suggests that some patients with clinically proven otosclerosis have a tendency for progression of sensorineural hearing loss, a review of over 500 ears in patients with proven otosclerosis was undertaken. Data from the study indicate that patients with otosclerosis have more sensorineural hearing loss than the general population. Also some otosclerotic ears have a tendency for progression of sensorineural hearing loss.

Audiometry↗
PubMed1985

Diagnostic and prognostic significance of so-called direct bone conduction in otospongiosis.

The modified Pohlman sound probe was used to provide a prognostic evaluation of the results of surgery in otospongiosis by means of transtympanic exploration. Based on the reactions obtained with this probe, it is possible to recognize theoretically the degree of cochlear involvement 'direct bone conduction coefficient' and to indicate which component of the hearing defect - conductive or perceptive - prevails in a given case of otospongiosis.

Adult↗