[COCHLEAR IMPLANTATION FOR PATIENTS WITH CONSERVATIVELY TREATED VESTIBULAR SCHWANNOMA].

INTRODUCTION: Vestibular Schwannoma, a benign slow growing tumor on the eight cranial nerve, will eventually cause in most patients, a severe sensory neural hearing loss in the ipsilateral ear. Patients with asymmetric hearing loss experience difficulties in hearing in the presence of noise, in sound localization and an increase in listening effort, especially if contralateral hearing loss exists. Cochlear implant is the treatment of choice for hearing rehabilitation in severe to profound sensorineural hearing loss. This treatment was shown to be effective in patients with vestibular schwannoma whether they were treated by surgery, radiation or conservative surveillance only. In this case report we present 2 patients with stable growth of over 10 years, who presented with a severe decrease in hearing loss on the ipsilateral side and a known contralateral moderate loss. Both underwent cochlear implant with no other intervention and demonstrated great speech perception results and continue to use the implant regularly for several years. The cochlear implant is an effective tool for hearing rehabilitation for patients with a stable vestibular schwannoma under conservative surveillance. It is of grave importance to properly educate these patients on hearing rehabilitation and recommend cochlear implant for appropriate patients.

Hearing loss in vitiligo: current concepts and review.

The objective of this study was to describe the occurrence, clinical manifestations, audiometric findings, pathogenesis and approach to sensorineural hearing loss (SNHL) among patients diagnosed with vitiligo with a review of the literature. We present a systematic review of the literature on cases of SNHL in patients diagnosed with vitiligo and studies conducted to investigate audiometric changes in such patients. Data on presentation, diagnosis and medical approach were reviewed. A total of 21 studies and case reports revealed at least 102 cases of SNHL in patients diagnosed with vitiligo. Arguments for a common causative etiology related to melanocyte function were mentioned in most of the literature. Evaluation of hearing function among all patients diagnosed with vitiligo seems to be an accepted approach; it should include audiometry, otoacoustic emissions (OAE) and ABR measurements. Extra precaution to prevent ototoxic or noise-induced hearing loss is strongly recommended. Further research is needed to better understand its pathogenesis.

Soft tissue conduction as a possible contributor to the limited attenuation provided by hearing protection devices.

CONTEXT: Damage to the auditory system by loud sounds can be avoided by hearing protection devices (HPDs) such as earmuffs, earplugs, or both for maximum attenuation. However, the attenuation can be limited by air conduction (AC) leakage around the earplugs and earmuffs by the occlusion effect (OE) and by skull vibrations initiating bone conduction (BC). AIMS: To assess maximum attenuation by HPDs and possible flanking pathways to the inner ear. SUBJECTS AND METHODS: AC attenuation and resulting thresholds were assessed using the real ear attenuation at threshold (REAT) procedure on 15 normal-hearing participants in four free-field conditions: (a) unprotected ears, (b) ears covered with earmuffs, (c) ears blocked with deeply inserted customized earplugs, and (d) ears blocked with both earplugs and earmuffs. BC thresholds were assessed with and without earplugs to assess the OE. RESULTS: Addition of earmuffs to earplugs did not cause significantly greater attenuation than earplugs alone, confirming minimal AC leakage through the external meatus and the absence of the OE. Maximum REATs ranged between 40 and 46 dB, leading to thresholds of 46-54 dB HL. Furthermore, calculation of the acoustic impedance mismatch between air and bone predicted at least 60 dB attenuation of BC. CONCLUSION: Results do not support the notion that skull vibrations (BC) contributed to the limited attenuation provided by traditional HPDs. An alternative explanation, supported by experimental evidence, suggests transmission of sound to inner ear via non-osseous pathways such as skin, soft tissues, and fluid. Because the acoustic impedance mismatch between air and soft tissues is smaller than that between air and bone, air-borne sounds would be transmitted to soft tissues more effectively than to bone, and therefore less attenuation is expected through soft tissue sound conduction. This can contribute to the limited attenuation provided by traditional HPDs. The present study has practical implications for hearing conservation protocols.

Air, bone and soft tissue excitation of the cochlea in the presence of severe impediments to ossicle and window mobility.

Clinical conditions have been described in which one of the two cochlear windows is immobile (otosclerosis) or absent (round window atresia), but nevertheless bone conduction (BC) thresholds are relatively unaffected. To clarify this apparent paradox, experimental manipulations which would severely impede several of the classical osseous mechanisms of BC were induced in fat sand rats, including discontinuity or immobilization of the ossicular chain, coupled with window fixation. Effects of these manipulations were assessed by recording auditory nerve brainstem evoked response (ABR) thresholds to stimulation by air conduction (AC), by osseous BC and by non-osseous BC (also called soft tissue conduction-STC) in which the BC bone vibrator is applied to skin sites. Following the immobilization, discontinuity and window fixation, auditory stimulation was also delivered to cerebro-spinal fluid (CSF) and to saline applied to the middle ear cavity. While the manipulations (immobilization, discontinuity, window fixation) led to an elevation of AC thresholds, nevertheless, there was no change in osseous and non-osseous BC thresholds. On the other hand, ABR could be elicited in response to fluid pressure stimulation to CSF and middle ear saline, even in the presence of the severe restriction of ossicular chain and window mobility. The results of these experiments in which osseous and non-osseous BC thresholds remained unchanged in the presence of severe restriction of the classical middle ear mechanisms and in the absence of an efficient release window, while ABR could be recorded in response to fluid pressure auditory stimulation to fluid sites, indicate that it is possible that the inner ear may be activated at low sound intensities by fast fluid pressure stimulation. At higher sound intensities, a slower passive basilar membrane traveling wave may serve to excite the inner ear.

Issues Concerning the Mechanisms of Bone Conduction.

Air and bone conduction thresholds are used to differentiate between conductive and sensori-neural hearing losses because bone conduction is thought to bypass the conductive apparatus, directly activating the inner ear. However, the suggested bone conduction mechanisms involve the outer and middle ears. Also, normal bone conduction thresholds have been reported in cases of lesions to the conduction pathway. Therefore, further investigation of bone conduction mechanisms is required.

Thresholds to soft tissue conduction stimulation compared to bone conduction stimulation.

This study was designed to compare the thresholds to a standard clinical bone vibrator applied to sites on the head over skull bone (bone conduction, BC) and to soft tissue sites on the head and neck (soft tissue conduction, STC) with static application forces of 100 and 500 g in order to assess the possibility that STC is actually a form of BC, since both are elicited by stimulation with the same bone vibrator. Thresholds to 2.0-kHz tones were assessed in dB hearing level settings of the audiometer in the BC stimulation mode. There was no difference in threshold between forces of 100 and 500 g when applied to the skull bone sites (e.g. mastoid, forehead). However, at soft tissue sites (e.g. below the ear lobe, under the chin, on the sterno-cleido-mastoid muscle), thresholds to 100 g were significantly higher (poorer) than those to 500 g. With the 500 g static force (and also with the 100 g force), the thresholds at the STC sites were higher (poorer) than those at the skull bone sites. These findings have implications for understanding BC and STC modes of auditory activation.

Effect on auditory threshold of air and water pockets bordering the pathway between soft tissue stimulation sites and the cochlea.

OBJECTIVES: Auditory sensation can be elicited by applying a bone conduction vibrator to skin sites on the head, neck, and thorax over soft tissues. This is called soft tissue conduction (STC). We hypothesized that introducing substances with acoustic impedances that sharply deviate from those of soft tissues, such as air pockets, into the soft tissues beneath soft tissue stimulation sites would have an effect on the auditory threshold to stimulation at skin sites over soft tissue. METHODS: In human subjects, we assessed the auditory threshold with a bone vibrator applied to several STC sites, especially the cheek, and to several bone conduction sites on the skull. The subjects were equipped with bilateral earplugs. The subject then filled his or her cheek with either air or water, and the auditory threshold was again determined. We also recorded the auditory brain stem response to STC stimulation under the chin in fat sand rats in the absence and presence of subcutaneous air or saline solution pockets (0.4 mL) under the chin. RESULTS: In humans, the threshold to stimulation on the cheek was elevated (13 to 18 dB) in the presence of an air-inflated cheek, but not with a water-filled cheek. In animals, in the presence of an air pocket, the auditory brain stem response threshold was elevated by 10 to 20 dB; no threshold change occurred with a saline solution pocket. CONCLUSIONS: The introduction of air (but not water) into the soft tissues beneath the soft tissue stimulation sites led to a threshold elevation in both humans and animals. This was not the case when an identical volume of water was introduced, which would also have interrupted a possible parallel bone conduction pathway. These results provide evidence that soft tissue stimulation at low intensities induces tissue vibrations that are transmitted to the cochlea along a series of soft tissues with similar acoustic impedances.

Unique Patterns of Bilingual Speech: Factors Affecting Disfluency Rates in Russian-Hebrew Bilingual Children.

PURPOSE: Bilingual children often demonstrate a high rate of disfluencies, which might impact the diagnostic evaluation of fluency disorders; however, research on the rates and types of disfluencies in bilinguals' two languages is limited. The purpose of this research is to profile disfluencies of two types, stuttering-like disfluencies (SLDs) and other disfluencies (ODs), in the speech of Russian-Hebrew bilingual typically developing children, focusing on cross-linguistic differences and the effect of language proficiency in both languages. METHOD: Spontaneous narratives based on the Frog, Where Are You? (Mayer, 1969) picture book were collected in both languages from 40 bilingual Russian-Hebrew children aged 5;6-6;6 (years;months). The transcribed narratives were coded for SLD (sound, syllable, and monosyllabic word repetitions) and OD (multisyllabic word/phrase repetitions, interjections, and revisions), and their frequencies per 100 syllables were calculated. RESULTS: Overall, most children had a percentage of SLD and OD below the cutoff point and within the existing criteria for stuttering diagnosis established based on monolingual data, but several children exceeded this stuttering criterion. Monosyllabic word repetitions (part of SLD) and interjections (part of OD) were more frequent in Hebrew than in Russian. Lower proficiency was associated with a higher percentage of monosyllabic word repetitions and of interjections in both languages. CONCLUSIONS: Bilingual disfluency criteria are needed, since based on the existing monolingual criteria, some children might be erroneously assessed as children who stutter, thus leading to overdiagnosis. The results support the claim that proficiency is an important factor in the production of disfluencies.

Experimental exploration of the soft tissue conduction pathway from skin stimulation site to inner ear.

OBJECTIVES: Auditory sensation can be elicited by air conduction (AC) and by bone conduction (BC). It is also possible to elicit such responses by applying the standard clinical bone vibrator to the skin over soft tissue sites on the head, neck, or thorax of humans and animals. This mode of auditory stimulation has been called soft tissue conduction (STC). This study was designed to investigate the pathway between soft tissue sites and the ear. METHODS: The air in the middle ear was replaced with saline solution in an animal with unique anatomy--the fat sand rat, in which about 70% of a thin-walled inner ear bulges into the middle ear bulla cavity--while we recorded the auditory brain stem responses (ABRs) to AC, BC, and STC stimulation. RESULTS: This replacement of air with saline solution led to a significant improvement in STC threshold. With AC stimulation, the ABR threshold was elevated and the latency of the first ABR wave was prolonged. Consistent changes were not seen with BC stimulation. CONCLUSIONS: When the air (which has a very low acoustic impedance) that normally surrounds most of the inner ear is replaced with saline solution (which has an acoustic impedance similar to that of soft tissues), the STC threshold is improved. This improvement may be due to improved transmission of acoustic energy from the soft tissues to the inner ear.

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.

No changes in cochlear implant mapping and audiometric parameters in adolescence.

BACKGROUND: Audiologists mapping in the clinic report that many cochlear-implanted teenagers and their parents complain of deterioration in hearing capabilities. The aim of this study was to compare the mapping parameters measured over the years and determine whether more changes occurred throughout adolescence than during childhood. METHODS: The files of 23 cochlear-implanted teenagers were studied retrospectively. Data were collected for each individual at several time points between the ages of 6.5 and 18.25 years. Typical data collected from the mapping sessions included behaviorally measured T values, impedance results, audiogram thresholds in the free field with the implant, speech reception threshold, and speech perception of vowel-consonant-vowel syllables. RESULTS: No changes were found in either the behavioral or the objective parameters over the years. CONCLUSIONS: The stability in mapping and audiometric measurements found in adolescence do not support an explanation based on hormonal and growth effects on implant function. Perhaps a more likely cause of the subjective sense of hearing deterioration is related to changes in social and educational requirements.

Perceptions of Preceptors and Audiology Students on Practicum During the COVID-19 Pandemic.

PURPOSE: The aim of this study was to assess the perceptions of audiology students and preceptors regarding changes in the practicum as a result of COVID-19. METHOD: This study was conducted during two different periods, with Internet questionnaires posted on social media forums. Preceptors and newly graduated clinicians were recruited in 2019 for a study prior to COVID-19, and students and preceptors were recruited for comparison during COVID-19. Four groups participated in this study: (a) 101 students who were enrolled in the second, third, or fourth year of an Israeli communication disorders Bachelor of Arts (BA) program during the pandemic; (b) 94 newly graduated audiologists with a BA degree from an Israeli communication disorders program granted in the last 3 years (before COVID-19); (c) 18 audiologist preceptors who supervised audiology practicum in an Israeli communication disorders BA programs (before COVID-19); and (d) 20 audiologist preceptors who, during COVID-19, were supervising an audiology practicum in Israel. Perceptions of the various groups were compared. RESULTS: Although perceptions of preceptors and students regarding the practicum were revealed to be similar, perceptions of the practicum before COVID-19 underwent changes in the course of the pandemic. In evaluating the COVID-19 experience, both preceptors and students agreed that more hours of practicum were needed, as well as more variety in types of cases and exposure to varied placements. CONCLUSION: Academic programs and employers should consider implications of changes implemented in the practicum due to COVID-19, which can be addressed either in continuing education and/or by additional supervision in the future workplace. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.19855639.

Several mechanical manipulations of the wall of the inner ear do not affect air and bone conduction auditory thresholds.

OBJECTIVES: According to classic theories, auditory stimulation, whether air- or bone-conducted, has been thought to begin with sound-induced relative motion between the cochlear shell and the stapes footplate, producing a passive mechanical traveling wave along the basilar membrane. This study was designed to assess the effect of experimental mechanical manipulations of the cochlea on the auditory thresholds to air-conducted and bone-conducted stimulation. METHODS: The left ear of Psammomys obesus (highest auditory sensitivity between 0.5 and 5.0 kHz) was initially ablated in all animals studied. After baseline recording of auditory nerve-brain stem evoked response (ABR) thresholds to air- and bone-conducted broadband click stimulation from the right ear, a hole was drilled in the vestibule of that ear in 3 animals. In 2 other animals, the round window of the animals was immobilized. In 3 additional animals, the round window was widely perforated. Repeat ABR thresholds were then determined. RESULTS: There was no change in ABR thresholds to both air- and bone-conducted stimulation following these manipulations. The ABR wave latency also did not change. CONCLUSIONS: It is likely that an alternative mode of cochlear excitation is possible.

Experimental confirmation that vibrations at soft tissue conduction sites induce hearing by way of a new mode of auditory stimulation.

BACKGROUND: A new mode of auditory stimulation has been demonstrated which is through soft tissue conduction (STC). It involves evoking auditory sensations by applying the clinical bone vibrator to the skin over soft tissue (not over bone) sites on the head and neck. METHODS: This study was designed to show that stimulation by STC excites the cochlea in a way similar to that of air conduction (AC) and bone conduction (BC). RESULTS: It is shown here that auditory nerve brainstem evoked response (ABR) thresholds in mice and in the fat sand rat to AC, to BC and to STC stimulation are all elevated following administration of drugs (salicylic acid and furosemide) which depress the cochlear amplifier. In addition, the present study brings evidence that STC stimulation is not a variant of BC since the sound pressures recorded in the occluded external auditory canal (the occlusion effect) in response to STC are significantly smaller than that to BC stimulation, though both are of equal loudness. CONCLUSIONS: This new mode, STC, therefore appears to bypass the middle ear mechanisms and consequently may contribute to auditory diagnosis.

The Effect of Soft Tissue Stimulation on Skull Vibrations and Hearing Thresholds in Humans.

HYPOTHESIS: Hearing via soft tissue stimulation involves an osseous pathway. BACKGROUND: A recent study that measured both hearing thresholds and skull vibrations found that vibratory stimulation of soft tissue led to hearing sensation that correlated with skull vibrations, supporting the hypothesis of an osseous pathway. It is possible, however, that a lower application force of the vibrator on the stimulated soft tissue would not be sufficient to elicit skull vibration suggesting hearing via a nonosseous pathway. The purpose of the present study was to confirm the osseous pathway by measuring skull vibrations and behavioral thresholds using a low application force on a layer of ultrasound gel. Gel was used to mimic soft tissue because of its similar acoustic impedance and to control for variability between participants. METHODS: Hearing thresholds and the skull vibrations of five patients who were implanted with bone-anchored implants were assessed in two conditions when the bone vibrator was applied on the forehead: 1) direct application with 5N force; 2) through a layer of ultrasound gel with minimal application force. Skull vibrations were measured in both conditions by a laser Doppler vibrometer focused on the bone-anchored implant. RESULTS: Skull vibrations were present even when minimal application force was applied on soft tissue. The difference in skull vibrations when the vibrator was directly on the forehead compared with the gel condition was consistent with the variability in hearing thresholds between the two conditions. CONCLUSION: These results reinforce the hypothesis that skull vibrations are involved in hearing when sound is transmitted via either soft tissue or bone.

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.

Reduced salicylic acid binding following noise: possible evidence for prestin disruption.

To gain insight into the mechanism of noise induced permanent threshold shift (PTS), the magnitude of the auditory threshold elevation induced by injection of salicylic acid (which competitively binds with the motor protein prestin) to animals with a pre-existing PTS was compared to that in control animals (not exposed to noise). Normal mice were exposed to a noise intensity and duration which causes a small PTS. After determining the degree of the resulting PTS two weeks following the noise, salicylic acid was injected. The salicylic acid induced an additional threshold elevation and its magnitude was compared to that in control mice which had not been noise exposed. The mean noise induced PTS in the experimental (noise exposed) group was 25.5 dB. Following the administration of salicylic acid to these animals, there was an additional (salicylic acid induced) mean threshold elevation of 17.5 dB, and this was significantly smaller than that in control (not noise exposed) mice (36.8 dB). This may be evidence for a reduced number of salicylic acid binding sites on prestin and therefore the PTS may be due to disruption of prestin by the free radicals produced during the noise exposure.

How are the inner hair cells and auditory nerve fibers activated without the mediation of the outer hair cells and the cochlear amplifier?

The present study was designed to assess whether, in the presence of a depression of the cochlear amplifier i.e. a sensorineural hearing loss (SNHL), the inner hair cells (IHCs) require the presence of a normal endocochlear potential for transduction. An SNHL was induced by injecting salicylic acid (which binds to the motor protein prestin in the outer hair cells), and then furosemide (which depresses the endocochlear potential) was injected. Furosemide did not cause an additional elevation of the threshold of the auditory nerve brainstem evoked response (ABR) over that induced by the salicylic acid injection. Exposure to noise was also used to induce a SNHL in other mice, and then furosemide was injected. Here too furosemide did not cause an additional ABR threshold elevation over that induced by the noise. These results show that the IHCs (and the auditory nerve) can be excited in the presence of a SNHL (i.e. without the cochlear amplifier) and in the absence of an endocochlear potential. Possible mechanisms of excitation in such a state are discussed.

Occlusion Effect in Response to Stimulation by Soft Tissue Conduction-Implications.

To gain insight into the broader implications of the occlusion effect (OE-difference between unoccluded and occluded external canal thresholds), the OE in response to pure tones at 0.5, 1.0, 2.0 and 4.0 kHz to two bone conduction sites (mastoid and forehead) and two soft tissue conduction (STC) sites (under the chin and at the neck) were assessed. The OE was present at the soft tissue sites and at the bone conduction sites, with no statistical difference between them. The OE was significantly greater at lower frequencies, and negligible at higher frequencies. It seems that the vibrations induced in the soft tissues (STC) during stimulation at the soft tissue sites are conducted not only to the inner ear and elicit hearing, but also reach the walls of the external canal and initiate air pressures in the occluded canal which drive the tympanic membrane and excite the inner ear, leading to hearing. Use of a stethoscope by the internist to hear intrinsic body sounds (heartbeat, blood flow) serves as a clear demonstration of STC and its relation to hearing.

Audiogram in Response to Stimulation Delivered to Fluid Applied to the External Meatus.

BACKGROUND AND OBJECTIVES: Hearing can be elicited in response to vibratory stimuli delivered to fluid in the external auditory meatus. To obtain a complete audiogram in subjects with normal hearing in response to pure tone vibratory stimuli delivered to fluid applied to the external meatus. Subjects and. METHODS: Pure tone vibratory stimuli in the audiometric range from 0.25 to 6.0 kHz were delivered to fluid applied to the external meatus of eight participants with normal hearing (15 dB or better) using a rod attached to a standard clinical bone vibrator. The fluid thresholds obtained were compared to the air conduction (AC), bone conduction (BC; mastoid), and soft tissue conduction (STC; neck) thresholds in the same subjects. RESULTS: Fluid stimulation thresholds were obtained at every frequency in each subject. The fluid and STC (neck) audiograms sloped down at higher frequencies, while the AC and BC audiograms were flat. It is likely that the fluid stimulation audiograms did not involve AC mechanisms or even, possibly, osseous BC mechanisms. CONCLUSIONS: The thresholds elicited in response to the fluid in the meatus likely reflect a form of STC and may result from excitation of the inner ear by the vibrations induced in the fluid. The sloping fluid audiograms may reflect transmission pathways that are less effective at higher frequencies.