Cahtia Adelman

Bone conduction activation through soft tissues following complete immobilization of the ossicular chain, stapes footplate and round window

Classically it has been thought that bone conduction activation at the mastoid leads to relative motion between the stapes footplate and the oval window due to inertial and to compression (distortion) mechanisms. However, several recent clinical findings and experimental manipulations may point to additional mechanisms. These manipulations were extended in the present study. In ten fat sand rats, following obliteration of one ear, auditory nerve brainstem evoked response (ABR) thresholds were recorded in response to broad band click stimuli, either air conducted (AC) through insert earphones or bone conducted (BC) delivered directly to the exposed skull bone. Following this, the entire ossicular chain, stapes footplate and round window were completely immobilized with super glue, leading to a mean AC threshold elevation of 44 dB, but to a mean BC threshold change (elevation) of only 3.5 dB. In this state of complete immobilization, the bone vibrator was applied to a pool of saline in the surgical area and ABR was elicited with a mean threshold which was not significantly different from that of the BC threshold. When the bone vibrator was then applied to the eye without touching the bone at the orbit, the resulting ABR threshold was about 20 dB greater than the BC threshold. In conclusion, BC stimulation can activate the cochlea without two mobile windows. Furthermore, the cochlea can be activated by a fluid pathway and by application of a bone vibrator to non-osseous sites (soft tissue conduction).

Combined effects of salicylic acid and furosemide and noise on hearing

BackgroundA major cause of the hearing loss following exposure to intense noise involves release of free radicals resulting from the elevated metabolism. The free radicals induce damage to several of the components of the cochlear amplifier including the outer hair cells and indirectly to the transduction currents. Salicylic acid induces a reversible hearing loss since it binds to the motor protein prestin in the outer hair cells, reducing electromotility. Furosemide also induces a reversible hearing loss since it reduces the endocochlear potential which is a major component of the cochlear transduction currents. On the other hand, each of these drugs also provides protection from a noise induced hearing loss if they are injected just before a noise exposure, probably as a result of the decreased metabolism induced in their presence, with release of lower levels of free radicals. In this study, both drugs were administered in order to assess whether their protective effects would be additive.MethodsThe study was conducted on normal hearing albino mice of the Sabra strain. They were injected with either salicylic acid alone (N = 11), or furosemide alone (N = 14), or both together (N = 14), or with saline control (N = 11) and exposed to broad band noise for 3.5 hours. An additional group of 9 mice was injected with both salicylic acid and furosemide, but not exposed to noise. The degree of the resulting hearing loss was assessed by recording thresholds of the auditory nerve brainstem evoked responses to broad band clicks before the injections and noise, and 7, 14 and 21 days after.ResultsThe noise induced hearing loss in the mice injected with salicylic acid alone or furosemide alone was smaller than in those injected with saline, i.e. these drugs provided protection, as in previous studies in this laboratory. There was no threshold elevation after two weeks in the mice injected with both drugs without noise exposure, i.e. the effects of the two drugs given together was reversible. On the other hand, there was a significant hearing loss (i.e. threshold elevation) in the group which received both drugs and was also exposed to noise, with mean threshold elevations of 38.8 ± 19.0 dB and 28.3 ± 11.7 dB 7 days after noise exposure.ConclusionsThis result is very surprising, if not paradoxical. Drugs which provide protection from a noise induced hearing loss when administered alone, not only do not provide protection when given together, but also induce a greater hearing loss when accompanied by noise. This observation may be related to the finding that the depression of the endocochlear potential normally caused by furosemide is reduced in the presence of salicylic acid, so that the protection usually provided by furosemide is not present when it is administered together with salicylic acid. Thus it seems that each drug may interfere with the protective action of the other when coupled with noise.

Salicylic Acid Injection before Noise Exposure Reduces Permanent Threshold Shift

The permanent threshold shift (PTS) following exposure to intense noise may be due to the noise-induced excessive vibrations in the cochlea or to the generation of elevated levels of reactive oxygen species. Thus, it is possible that the resulting PTS may be reduced if the cochlear amplifier could be temporarily depressed beginningjust before the onset of the noise and continuing during the noise exposure or if antioxidant drugs were administered. These possibilities were assessed in mice by administering a single injection of salicylic acid (an antioxidant drug which also reversibly depresses the motor protein prestin of the cochlear amplifier) just before, and in other mice, just after, 3.5 h of 113-dB SPL broadband noise exposure. The PTS in the mice injected with salicylic acid just before the noise exposure was significantly smaller than that in mice exposed to the same noise without salicylic acid. The PTS in the latter was not significantly different from that in mice who received the drug just after the noise. Thus a single injection of salicylic acid, just before a noise exposure, can protect the ear from a noise-induced hearing loss.

Being an adolescent with a cochlear implant in the world of hearing people: Coping in school, in society and with self identity

OBJECTIVE The cochlear implant has revolutionized functioning with severe-to-profound sensori-neural loss. A deaf child implanted at an early age with good habilitation may have good language abilities and function well in daily life. As the implanted child grows up, managing in the world of hearing people may become more complex. During adolescence, the teenager copes with many issues, including identity, socialization with the peer group, and managing in the school setting. These issues may be even more challenging for the adolescents using a cochlear implant. This study was designed to shed light on how adolescents with cochlear implants experience coping with the issues mentioned. METHOD Twelve teenagers (14-18 years old), fairly similar to the entire adolescent implanted population at the center at which the study was conducted, participated in the study. They had been unilaterally or bilaterally implanted at differing ages. The participants filled out a questionnaire dealing with their functioning in the educational setting, their social preferences and functioning, and their identity as hearing or deaf. The results were analyzed using the principles of thematic analysis. RESULTS At school, some reported better achievements than others but they all expressed some difficulty functioning in class mainly in situations involving several speakers. From a social point of view, some reported a preference for association with normal hearing peers, whereas others favored hard-of-hearing friends, and one had no preference. Of those who touched on the topic of self-identity, one referred to herself as deaf, eight defined themselves as hard-of-hearing, and two consider themselves hearing. CONCLUSIONS From the responses of these teenagers, it is clear that adolescents with cochlear implants are a heterogeneous group. Parents and teachers should be aware that adolescents with implants, even when successful academically, may experience difficulties in the classroom setting. Most of the participants in this study learning in a mainstream setting, preferred social relationships with hearing peers (to hard of hearing/deaf). The responses of these adolescents with cochlear implants support the conjecture that they have both a hearing identity and a deaf identity, which may be expressed at varying intensities depending on the situation at the time.

Interactions in the cochlea between air conduction and osseous and non-osseous bone conduction stimulation.

Since air-conducted (AC) and clinical (mastoid) bone-conducted (BC) sounds interact in the cochlea (e.g. pitch, cancellation, masking, beats), it has been thought that both AC and BC stimulations lead to a mechanical wave in the cochlea. However, there are also “non-osseous” forms of BC, i.e. auditory sensation produced when the clinical bone vibrator is applied to “non-osseous” soft tissue sites. In the present study, such “non-osseous” sites were identified (e.g. eye, cheek, neck) and they interacted with AC and osseous BC (pitch matching, beats, masking), indicating that all of these forms of auditory stimulation converge in the cochlea, producing the same pattern of mechanical activity, leading to their interactions.

Transient Evoked Otoacoustic Emissions in Newborns in the First 48 Hours After Birth

Newborns are often discharged from hospital at the age of about 48 hours. At this age, transient evoked otoacoustic emissions (TEOAEs) are not necessarily recordable in all healthy newborns. In order to determine the factors which would enable the successful recording of TEOAEs before discharge to facilitate screening for hearing, 65 fullterm newborns under 48 hours of age were tested, the youngest being 10 hours old. The ears of those neonates in whom TEOAEs could not be obtained (N = 7 neonates bilaterally, 6 unilaterally) were examined otoscopically, cleaned of vernix and retested for TEOAEs. We were thus able to record in at least one ear in all neonates tested, if the ears were clean, if they were asleep and if the testing room was quiet.

Auditory Nerve and Brain Stem Evoked Response Thresholds in Infants Treated with Gentamicin as Neonates

Thirty-two infants (18 full-term and 14 premature) who had been treated with gentamicin as neonates were examined to ascertain whether this drug induced hearing loss, even of low severity. Objective thresholds to clicks were obtained using auditory nerve and brain stem evoked responses. In addition, behavioral audiometry was performed. Serum concentrations before and after gentamicin treatment were at therapeutic levels. All infants were examined at least 1 1/4 months after cessation of therapy. Normal thresholds were obtained in all ears, with the exception of two with demonstrable middle ear effusion. It appears that gentamicin in therapeutic doses and serum concentrations, in the absence of renal insufficiency, does not cause hearing loss in neonates.

Uniform comparison of several drugs which provide protection from noise induced hearing loss

BackgroundThe ability of drugs to reduce noise induced hearing loss (NIHL) has been evaluated in diverse experimental conditions (animal species, noise intensities, durations, assessment techniques, etc), making it difficult to assess their relative efficacy. The present study was designed to provide more uniform comparisons and to allow to a better understanding of the mechanism of the NIHL. Methods: The drugs studied included furosemide (loop diuretic) and the antioxidants N Acetyl-L-Cysteine, vitamins A, C, E with the vasodilator magnesium. Mice were exposed to a continuous broadband noise (113 dB SPL for 3.5 hours) and the NIHL was assessed in all animals before noise exposure and 1 week after with auditory nerve brainstem evoked responses (ABR) to broadband clicks and to 8 kHz tone bursts.ResultsEach of the drugs alone and in combination led to similar reductions in NIHL.ConclusionsThe loop diuretic furosemide, by reducing the magnitude of the endocochlear potential in scala media, probably depressed active vibrations of the outer hair cells and basilar membrane, resulting in reduction of free radical formation during the noise exposure. The antioxidants N Acetyl-L-Cysteine and vitamins A, C, E with the vasodilator magnesium presumably counteract the free radicals. Thus, the administration of the antioxidants to animals in which free radical formation had already been reduced by previous injection of furosemide did not have an additional protective effect on the NIHL.

Comparison of two hearing screening programs in the same population: Oto-acoustic emissions (OAE) screening in newborns and behavioral screening when infants

OBJECTIVE Hearing screening programs in infancy should identify hearing impairment as early as possible. The two common programs utilize either objective neonatal tests (oto-acoustic emissions (OAE) or automatic auditory brainstem responses (aABR)) or behavioral screening at 7-9 months of age. Most countries employ only one of these options. The uniqueness of this study is the comparison of both hearing screening programs on the same group of children. METHODS The study was conducted on 1545 children born between the years 1999 and 2003 who were followed up in public well baby clinics in the Jerusalem district. The children were tested with transient oto-acoustic emissions (TEOAE) before discharge from the neonatal ward, and later, at the age of 7-9 months, underwent a behavioral hearing screening test in a public well baby clinic. The results of both hearing screening programs were compared. RESULTS The compliance rates were 99.7% for the neonatal testing and 83% for the 7-9 months behavioral testing (p=0.0001). The failure rate was 4-6% in both screening programs; failure of OAE testing was unilateral in 65% of newborns; at 7-9 months bilateral failure was more common (56%). There was an 11.2% disagreement (kappa coefficient 0.03) between the outcomes of both tests. In another group of 49 known hearing-impaired children, 27 who had undergone newborn screening were diagnosed before the age of behavioral testing. Twelve children had failed either both tests or the only test they underwent. In nine cases, the children had passed one of the hearing screening tests and had failed the other, and one child had passed both tests. CONCLUSIONS Newborn hearing screening has the advantages of objectivity, early identification, and higher compliance. The major advantage of the later behavioral test is identification of later onset or progressive hearing impairment as well as auditory neuropathy spectrum disorder. Each screening test is testing different entities; hence they are complementary and not interchangeable or superfluous. We recommend a comprehensive two-step hearing screening plan (newborn and later behavioral) with close cooperation between the health care providers involved.

Furosemide administered before noise exposure can protect the ear.

Objectives We assessed the effect of furosemide administration on noise-induced hearing loss. This drug reversibly elevates the auditory threshold by inducing a temporary reduction of the endocochlear potential and thereby suppresses the cochlear amplifier and active cochlear mechanics. Methods Mice were given a single injection of furosemide 30 minutes before exposure to 113 dB sound pressure level broadband noise. Control animals received saline solution. Furosemide was administered in other mice after the noise exposure. Auditory threshold shifts were assessed by recording auditory nerve brain stem evoked response (ABR) thresholds to broadband clicks. Results The mean ABR threshold in the group injected with furosemide and exposed to temporary threshold shift (TTS)-producing noise was elevated by 20.4 ± 12.3 dB, and that in the saline control group was elevated by 35.4 ± 18.3 dB (p < 0.02). The mean threshold elevations in the group injected with furosemide and exposed to permanent threshold shift (PTS)-producing noise and in the PTS saline control group were 15.0 ± 10.3 dB and 27.0 ± 12.7 dB, respectively (p < 0.01). Similar results were obtained when the PTS was assessed with an 8-kHz tone burst ABR. There was no significant difference in the PTS between mice given a single injection of furosemide and those given saline solution after the noise; this finding shows that furosemide is not acting as an antioxidant. Conclusions It appears that reversible hearing threshold elevation as a result of furosemide administration before noise exposure can reduce the TTS and PTS. This finding provides insight into the mechanism of noise-induced hearing loss.