Noise Damage Without Hearing Loss

If you have occasional, regular or constant ringing in your ears, you are not alone. Up to 15 percent of American adults have this condition, and it has serious impacts on about 1 percent of the population. Tinnitus can make it hard to carry on a conversation, listen to a professor, watch television or conduct a meeting with your boss or colleagues. In most cases, tinnitus is related to damaged hearing without hearing loss.

Audiograms and the Detection of Hearing Loss
When a person has tinnitus, the first stop is often an audiologist’s office. An audiologist conducts tests known as audiograms. The audiogram is a type of hearing tests that measures the lowest frequency and highest frequency that you can detect from each ear. Having tinnitus can make it difficult for you to participate in an audiogram because the sound of the tinnitus can interfere with the tones played by the audiologist.

The Relationship between Tinnitus and Hearing Loss
In most cases, tinnitus is related to damage to your ears. However, not all noise damage causes hearing loss. This is one reason why an audiogram may not be able to find the cause of your tinnitus. People with normal audiograms may actually have an undetectable type of hearing loss. This type of undetected hearing loss is usually related to noise damage. Ear damage from loud noise has a strong relationship with tinnitus, as most people who have tinnitus also report a history of multiple exposures to loud sounds.

How You can Have Noise Damage Without Hearing Loss
You can have tinnitus and noise damage without hearing loss because your brain has different neurons that detect high volume sounds. These neurons are not tested during a pure tone audiogram. The damage to these neurons directly affects your perception of sounds. People with this undetected hearing damage have symptoms such as tinnitus and hypersensitivity to sounds. Degeneration of these neurons can result from a single exposure to an extremely loud sound or from frequent exposure to moderately loud sounds. This kind of noise damage without hearing loss is progressive and tends to worsen with age.

If a pure tone hearing test does not identify that you have a hearing loss, you could still have noise damage to your auditory system. Taking action to prevent further damage to your ears may also help to lessen the frequency and severity of your tinnitus symptoms.

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Efficient Targeted Next Generation Sequencing-Based Workflow for Differential Diagnosis of Alport-Related Disorders

by Gábor Kovács, Tibor Kalmár, Emőke Endreffy, Zoltán Ondrik, Béla Iványi, Csaba Rikker, Ibolya Haszon, Sándor Túri, Mária Sinkó, Csaba Bereczki, Zoltán Maróti

Alport syndrome (AS) is an inherited type IV collagen nephropathies characterized by microscopic hematuria during early childhood, the development of proteinuria and progression to end-stage renal disease. Since choosing the right therapy, even before the onset of proteinuria, can delay the onset of end-stage renal failure and improve life expectancy, the earliest possible differential diagnosis is desired. Practically, this means the identification of mutation(s) in COL4A3-A4-A5 genes. We used an efficient, next generation sequencing based workflow for simultaneous analysis of all three COL4A genes in three individuals and fourteen families involved by AS or showing different level of Alport-related symptoms. We successfully identified mutations in all investigated cases, including 14 unpublished mutations in our Hungarian cohort. We present an easy to use unified clinical/diagnostic terminology and workflow not only for X-linked but for autosomal AS, but also for Alport-related diseases. In families where a diagnosis has been established by molecular genetic analysis, the renal biopsy may be rendered unnecessary.

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Musician advantage for speech-on-speech perception

Evidence for transfer of musical training to better perception of speech in noise has been mixed. Unlike speech-in-noise, speech-on-speech perception utilizes many of the skills that musical training improves, such as better pitch perception and stream segregation, as well as use of higher-level auditory cognitive functions, such as attention. Indeed, despite the few non-musicians who performed as well as musicians, on a group level, there was a strong musician benefit for speech perception in a speech masker. This benefit does not seem to result from better voice processing and could instead be related to better stream segregation or enhanced cognitive functions.

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Automated estimation of the truncation of room impulse response by applying a nonlinear decay model

Noise represents one of the most significant disturbances in measured room impulse responses (RIRs), and it has a potentially large impact on evaluation of the decay parameters. In order to reduce noise effects, various methods have been applied, including truncation of an RIR. In this paper, a procedure for the response truncation based on a model of RIR (nonlinear decay model) is presented. The model is represented by an exponential decay plus stationary noise. Unknown parameters of the model are calculated by an optimization that minimizes the difference between the curve generated by the model and the target one of the response to be truncated. Different curves can be applied in the optimization—absolute value of the RIR, logarithmic decay curve, and Schroeder curve obtained by the backward integration of the RIR. The proposed procedure is tested on various synthesized and measured impulse responses. It is compared with the procedure taken from the literature, often applied in practice.

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Effects of a consistent target or masker voice on target speech intelligibility in two- and three-talker mixtures

When the spatial location or identity of a sound is held constant, it is not masked as effectively by competing sounds. This suggests that experience with a particular voice over time might facilitate perceptual organization in multitalker environments. The current study examines whether listeners benefit from experience with a voice only when it is the target, or also when it is a masker, using diotic presentation and a closed-set task (coordinate response measure). A reliable interaction was observed such that, in two-talker mixtures, consistency of masker or target voice over 3–7 trials significantly benefited target recognition performance, whereas in three-talker mixtures, target, but not masker, consistency was beneficial. Overall, this work suggests that voice consistency improves intelligibility, although somewhat differently when two talkers, compared to three talkers, are present, suggesting that consistent-voice information facilitates intelligibility in at least two different ways. Listeners can use a template-matching strategy to extract a known voice from a mixture when it is the target. However, consistent-voice information facilitates segregation only when two, but not three, talkers are present.

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Musician advantage for speech-on-speech perception

Evidence for transfer of musical training to better perception of speech in noise has been mixed. Unlike speech-in-noise, speech-on-speech perception utilizes many of the skills that musical training improves, such as better pitch perception and stream segregation, as well as use of higher-level auditory cognitive functions, such as attention. Indeed, despite the few non-musicians who performed as well as musicians, on a group level, there was a strong musician benefit for speech perception in a speech masker. This benefit does not seem to result from better voice processing and could instead be related to better stream segregation or enhanced cognitive functions.

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Reducing the risk of music-induced hearing loss from overuse of portable listening devices: understanding the problems and establishing strategies for improving awareness in adolescents.

Reducing the risk of music-induced hearing loss from overuse of portable listening devices: understanding the problems and establishing strategies for improving awareness in adolescents.

Adolesc Health Med Ther. 2016;7:27-35

Authors: Portnuff CD

Abstract
Hearing loss from the overuse of portable listening devices (PLDs), such as MP3 players or iPods, is of great concern in the popular media. This review aims to discuss the current state of scientific knowledge about music-induced hearing loss from PLD use. This report evaluates the literature on the risk to hearing from PLD use, the individual and psychological factors that influence PLD usage, and strategies for reducing exposure to music through PLDs. Specific interventions are reviewed, and several recommendations for designing interventions and for individual intervention in clinical practice are presented. Clinical recommendations suggested include the "80-90 rule" and the use of isolator-style earphones to reduce background noise.

PMID: 26929674 [PubMed]

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Assessment of voice quality after carbon dioxide laser and microdebrider surgery for Reinke edema.

Related Articles

Assessment of voice quality after carbon dioxide laser and microdebrider surgery for Reinke edema.

J Voice. 2015 Mar;29(2):256-9

Authors: Burduk PK, Wierzchowska M, Orzechowska M, Kaźmierczak W, Pawlak-Osińska K

Abstract
OBJECTIVES: Surgery of Reinke edema requires reduction of the degenerated superficial lamina propria and preservation of the vibratory epithelium.
MATERIAL AND METHODS: Sixteen patients were included for microdebrider and 10 patients for carbon dioxide (CO2) laser surgery. Vocal analysis was performed before and at 1 and 3 months after surgery. Subjective rating of voice quality was completed by the grade, roughness, breathiness, asthenia, and strain scale. The objective assessment was conducted by Multi-Dimensional Voice Program software.
RESULTS: We found consistent improvement in all parameters both in CO2 laser and microdebrider group. The normalization of all parameters were statistically better after microdebrider surgery. The most statistically significant improvements were accounted in reduction in grade of hoarseness, roughness, and asthenia and acoustic analysis.
CONCLUSIONS: Microdebrider is a useful and safe tool for Reinke edema treatment. The oscillatory cutting knife and low suction protect lamina propria resulting in better vibratory function.

PMID: 25261956 [PubMed - indexed for MEDLINE]

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Reducing the risk of music-induced hearing loss from overuse of portable listening devices: understanding the problems and establishing strategies for improving awareness in adolescents.

Reducing the risk of music-induced hearing loss from overuse of portable listening devices: understanding the problems and establishing strategies for improving awareness in adolescents.

Adolesc Health Med Ther. 2016;7:27-35

Authors: Portnuff CD

Abstract
Hearing loss from the overuse of portable listening devices (PLDs), such as MP3 players or iPods, is of great concern in the popular media. This review aims to discuss the current state of scientific knowledge about music-induced hearing loss from PLD use. This report evaluates the literature on the risk to hearing from PLD use, the individual and psychological factors that influence PLD usage, and strategies for reducing exposure to music through PLDs. Specific interventions are reviewed, and several recommendations for designing interventions and for individual intervention in clinical practice are presented. Clinical recommendations suggested include the "80-90 rule" and the use of isolator-style earphones to reduce background noise.

PMID: 26929674 [PubMed]

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Assessment of voice quality after carbon dioxide laser and microdebrider surgery for Reinke edema.

Related Articles

Assessment of voice quality after carbon dioxide laser and microdebrider surgery for Reinke edema.

J Voice. 2015 Mar;29(2):256-9

Authors: Burduk PK, Wierzchowska M, Orzechowska M, Kaźmierczak W, Pawlak-Osińska K

Abstract
OBJECTIVES: Surgery of Reinke edema requires reduction of the degenerated superficial lamina propria and preservation of the vibratory epithelium.
MATERIAL AND METHODS: Sixteen patients were included for microdebrider and 10 patients for carbon dioxide (CO2) laser surgery. Vocal analysis was performed before and at 1 and 3 months after surgery. Subjective rating of voice quality was completed by the grade, roughness, breathiness, asthenia, and strain scale. The objective assessment was conducted by Multi-Dimensional Voice Program software.
RESULTS: We found consistent improvement in all parameters both in CO2 laser and microdebrider group. The normalization of all parameters were statistically better after microdebrider surgery. The most statistically significant improvements were accounted in reduction in grade of hoarseness, roughness, and asthenia and acoustic analysis.
CONCLUSIONS: Microdebrider is a useful and safe tool for Reinke edema treatment. The oscillatory cutting knife and low suction protect lamina propria resulting in better vibratory function.

PMID: 25261956 [PubMed - indexed for MEDLINE]

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TRUNK MUSCLES ACTIVATION DURING POLE WALKING VS. WALKING PERFORMED AT DIFFERENT SPEEDS AND GRADES

Publication date: Available online 2 March 2016
Source:Gait & Posture
Author(s): LUCA Zoffoli, FRANCESCO Lucertini, ARIO Federici, MASSIMILIANO Ditroilo
Given their functional role and importance, the activity of several trunk muscles was assessed (via surface electromyography - EMG) during Walking (W) and Pole Walking (PW) in 21 healthy adults. EMG data was collected from the external oblique (EO), the erector spinae longissimus (ES), the multifidus (MU), and the rectus abdominis (RA) while performing W and PW on a motorized treadmill at different speeds (60, 80, and 100% of the highest speed at which the participants still walked naturally; PTS60, PTS80 and PTS100, respectively) and grades (0 and 7%; GRADE0 and GRADE7, respectively). Stride length, EMG area under the curve (AUC), muscles activity duration (ACT), and percentage of coactivation (CO-ACT) of ES, MU and RA, were calculated from the averaged stride for each of the tested combinations.Compared to W, PW significantly increased the stride length, EOAUC, RAAUC and the activation time of all the investigated muscles, to different extents depending on treadmill speeds and grades. In addition, MUAUC was higher in PW than in W at GRADE0 only (all speeds, p<0.01), while ESAUC during W and PW was similar at all the speeds and grades. These changes resulted in longer CO-ACT in PW than W, at GRADE0-PTS100 (p<0.01) and GRADE7 (all speeds, p<0.01). In conclusion, when compared to W, PW requires a greater engagement of the abdominal muscles and, in turn, a higher control of the trunk muscles. These two factors taken together may suggest an elevated spinal stability while walking with poles.



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Gait modification strategies in trunk over right stance phase in patients with right anterior cruciate ligament deficiency

Publication date: Available online 2 March 2016
Source:Gait & Posture
Author(s): Dongliang Shi, Nannan Li, Yubin Wang, Shuyun Jiang, Jianping Lin, Wenhui Zhu
This study aimed to investigate the gait modification strategies of trunk over right stance phase in patients with right anterior cruciate ligament deficiency (ACL-D). Thirty-six patients with right chronic ACL-D were recruited, as well as 36 controls. A 3D optical video motion capture system was used during gait and stair ambulation. Kinematic variables of the trunk and kinematic and kinetic variables of the knee were calculated. Patients with chronic right ACL-D exhibited many significant abnormalities compared with controls. Trunk rotation with right shoulder trailing over the right stance phase was lower in all five motion patterns (P<0.05). Compared with controls, trunk posterior lean was higher from descending stairs to walking when the knee sagittal plane moment ended (P<0.01). Trunk lateral flexion to the left was higher when ascending stairs at the start of right knee coronal plane moment (P=0.01), when descending stairs at the maximal knee coronal plane moment (P<0.01), and when descending stairs at the end of the knee coronal plane moment (P=0.03). Trunk rotation with right shoulder forward was higher at the minimal knee transverse plane moment (P<0.01) and when the knee transverse plane moment ended (P<0.01); during walking, trunk rotation with right shoulder trailing was lower at other knee moments during other walking patterns (all P<0.01). In conclusion, gait modification strategies of the trunk were apparent in patients with ACL-D. These results provide new insights about diagnosis and rehabilitation of chronic ACL-D (better use of walking and stair tasks as part of a rehabilitation program).



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TRUNK MUSCLES ACTIVATION DURING POLE WALKING VS. WALKING PERFORMED AT DIFFERENT SPEEDS AND GRADES

Publication date: Available online 2 March 2016
Source:Gait & Posture
Author(s): LUCA Zoffoli, FRANCESCO Lucertini, ARIO Federici, MASSIMILIANO Ditroilo
Given their functional role and importance, the activity of several trunk muscles was assessed (via surface electromyography - EMG) during Walking (W) and Pole Walking (PW) in 21 healthy adults. EMG data was collected from the external oblique (EO), the erector spinae longissimus (ES), the multifidus (MU), and the rectus abdominis (RA) while performing W and PW on a motorized treadmill at different speeds (60, 80, and 100% of the highest speed at which the participants still walked naturally; PTS60, PTS80 and PTS100, respectively) and grades (0 and 7%; GRADE0 and GRADE7, respectively). Stride length, EMG area under the curve (AUC), muscles activity duration (ACT), and percentage of coactivation (CO-ACT) of ES, MU and RA, were calculated from the averaged stride for each of the tested combinations.Compared to W, PW significantly increased the stride length, EOAUC, RAAUC and the activation time of all the investigated muscles, to different extents depending on treadmill speeds and grades. In addition, MUAUC was higher in PW than in W at GRADE0 only (all speeds, p<0.01), while ESAUC during W and PW was similar at all the speeds and grades. These changes resulted in longer CO-ACT in PW than W, at GRADE0-PTS100 (p<0.01) and GRADE7 (all speeds, p<0.01). In conclusion, when compared to W, PW requires a greater engagement of the abdominal muscles and, in turn, a higher control of the trunk muscles. These two factors taken together may suggest an elevated spinal stability while walking with poles.



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Gait modification strategies in trunk over right stance phase in patients with right anterior cruciate ligament deficiency

Publication date: Available online 2 March 2016
Source:Gait & Posture
Author(s): Dongliang Shi, Nannan Li, Yubin Wang, Shuyun Jiang, Jianping Lin, Wenhui Zhu
This study aimed to investigate the gait modification strategies of trunk over right stance phase in patients with right anterior cruciate ligament deficiency (ACL-D). Thirty-six patients with right chronic ACL-D were recruited, as well as 36 controls. A 3D optical video motion capture system was used during gait and stair ambulation. Kinematic variables of the trunk and kinematic and kinetic variables of the knee were calculated. Patients with chronic right ACL-D exhibited many significant abnormalities compared with controls. Trunk rotation with right shoulder trailing over the right stance phase was lower in all five motion patterns (P<0.05). Compared with controls, trunk posterior lean was higher from descending stairs to walking when the knee sagittal plane moment ended (P<0.01). Trunk lateral flexion to the left was higher when ascending stairs at the start of right knee coronal plane moment (P=0.01), when descending stairs at the maximal knee coronal plane moment (P<0.01), and when descending stairs at the end of the knee coronal plane moment (P=0.03). Trunk rotation with right shoulder forward was higher at the minimal knee transverse plane moment (P<0.01) and when the knee transverse plane moment ended (P<0.01); during walking, trunk rotation with right shoulder trailing was lower at other knee moments during other walking patterns (all P<0.01). In conclusion, gait modification strategies of the trunk were apparent in patients with ACL-D. These results provide new insights about diagnosis and rehabilitation of chronic ACL-D (better use of walking and stair tasks as part of a rehabilitation program).



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TRUNK MUSCLES ACTIVATION DURING POLE WALKING VS. WALKING PERFORMED AT DIFFERENT SPEEDS AND GRADES

Publication date: Available online 2 March 2016
Source:Gait & Posture
Author(s): LUCA Zoffoli, FRANCESCO Lucertini, ARIO Federici, MASSIMILIANO Ditroilo
Given their functional role and importance, the activity of several trunk muscles was assessed (via surface electromyography - EMG) during Walking (W) and Pole Walking (PW) in 21 healthy adults. EMG data was collected from the external oblique (EO), the erector spinae longissimus (ES), the multifidus (MU), and the rectus abdominis (RA) while performing W and PW on a motorized treadmill at different speeds (60, 80, and 100% of the highest speed at which the participants still walked naturally; PTS60, PTS80 and PTS100, respectively) and grades (0 and 7%; GRADE0 and GRADE7, respectively). Stride length, EMG area under the curve (AUC), muscles activity duration (ACT), and percentage of coactivation (CO-ACT) of ES, MU and RA, were calculated from the averaged stride for each of the tested combinations.Compared to W, PW significantly increased the stride length, EOAUC, RAAUC and the activation time of all the investigated muscles, to different extents depending on treadmill speeds and grades. In addition, MUAUC was higher in PW than in W at GRADE0 only (all speeds, p<0.01), while ESAUC during W and PW was similar at all the speeds and grades. These changes resulted in longer CO-ACT in PW than W, at GRADE0-PTS100 (p<0.01) and GRADE7 (all speeds, p<0.01). In conclusion, when compared to W, PW requires a greater engagement of the abdominal muscles and, in turn, a higher control of the trunk muscles. These two factors taken together may suggest an elevated spinal stability while walking with poles.



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Perinatal Thiamine Deficiency Causes Cochlear Innervation Abnormalities in Mice

Publication date: Available online 2 March 2016
Source:Hearing Research
Author(s): Stéphane F. Maison, Yanbo Yin, Leslie D. Liberman, M.Charles Liberman
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.



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Perinatal Thiamine Deficiency Causes Cochlear Innervation Abnormalities in Mice

Publication date: Available online 2 March 2016
Source:Hearing Research
Author(s): Stéphane F. Maison, Yanbo Yin, Leslie D. Liberman, M.Charles Liberman
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.



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Perinatal Thiamine Deficiency Causes Cochlear Innervation Abnormalities in Mice

Publication date: Available online 2 March 2016
Source:Hearing Research
Author(s): Stéphane F. Maison, Yanbo Yin, Leslie D. Liberman, M.Charles Liberman
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.



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Perinatal Thiamine Deficiency Causes Cochlear Innervation Abnormalities in Mice

Publication date: Available online 2 March 2016
Source:Hearing Research
Author(s): Stéphane F. Maison, Yanbo Yin, Leslie D. Liberman, M.Charles Liberman
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.



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Perinatal Thiamine Deficiency Causes Cochlear Innervation Abnormalities in Mice

Publication date: Available online 2 March 2016
Source:Hearing Research
Author(s): Stéphane F. Maison, Yanbo Yin, Leslie D. Liberman, M.Charles Liberman
Neonatal thiamine deficiency can cause auditory neuropathy in humans. To probe the underlying cochlear pathology, mice were maintained on a thiamine-free or low-thiamine diet during fetal development or early postnatal life. At postnatal ages from 18 days to 22 wks, cochlear function was tested and cochlear histopathology analyzed by plastic sections and cochlear epithelial whole-mounts immunostained for neuronal and synaptic markers. Although none of the thiamine-deprivation protocols resulted in any loss of hair cells or any obvious abnormalities in the non-sensory structures of the cochlear duct, all the experimental groups showed significant anomalies in the afferent or efferent innervation. Afferent synaptic counts in the inner and outer hair cell areas were reduced, as was the efferent innervation density in both the outer and inner hair cell areas. As expected for primary neural degeneration, the thresholds for distortion product otoacoustic emissions were not affected, and as expected for subtotal hair cell de-afferentation, the suprathreshold amplitudes of auditory brainstem responses were more affected than the response thresholds. We conclude that the auditory neuropathy from thiamine deprivation could be produced by loss of inner hair cell synapses.



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