Single-sided deafness (SSD) is an extreme case of partial hearing deprivation and results in a significant decline in higher-order hearing abilities, including sound localization and speech-in-noise recognition. Clinical studies have reported that patients with SSD recover from these higher-order hearing abilities to some extent over time. Neuroimaging studies have observed extensive brain functional plasticity in patients with SSD. However, studies investigating the role of plasticity in functional compensation, particularly those investigating the relationship between intrinsic brain activity alterations and higher-order hearing abilities, are still limited. In this study, we used resting-state functional MRI to investigate intrinsic brain activity, measured by the amplitude of low-frequency fluctuation (ALFF), in 19 patients with left SSD, 17 patients with right SSD, and 21 normal hearing controls (NHs). All patients with SSD had durations of deafness longer than 2 years. Decreased ALFF values in the bilateral precuneus (PCUN), lingual gyrus, and left middle frontal gyrus were observed in patients with SSD compared with the values of NHs. Longer durations of deafness were correlated with better hearing abilities, as well as higher ALFF values in the left inferior parietal lobule, the angular gyrus, the middle occipital gyrus, the bilateral PCUN, and the posterior cingulate gyrus. Moreover, we observed a generally consistent trend of correlation between ALFF values and higher-order hearing abilities in specific brain areas in patients with SSD. That is, better abilities were correlated with lower ALFF values in the frontal regions and higher ALFF values in the PCUN and surrounding parietal-occipital areas. Furthermore, mediation analysis revealed that the ALFF values in the PCUN were a significant mediator of the relationship between the duration of deafness and higher-order hearing abilities. Our study reveals significant plasticity of intrinsic brain activity in patients with SSD and suggests that reorganization of intrinsic brain activity may be one of the compensatory mechanisms that facilitate improvement in higher-order hearing abilities in these patients over time. Single-sided deafness (SSD) is an extreme case of partial hearing deprivation and refers to severe to profound hearing loss in one ear and normal hearing in the other ear. Due to hearing deprivation in one ear, patients with SSD can only obtain monaural clues from the environment. This causes these patients to have sharply decreased higher-order hearing abilities, particularly sound localization and speech-in-noise (SIN) recognition  have observed extensive morphological alterations in gray and white matter, as well as structural connectivity involving auditory areas, other sensory areas, and higher-order cognitive-related brain areas  of resting-state fMRI reflects the intensity of regional brain activity at baseline , 19 patients with left SSD , and 17 patients with right SSD . All subjects were native speakers of Mandarin and had no history of neurological or mental illness or contraindications to MRI scans. The demographic information for these subjects is presented in t = −0.22, p = 0.828) between them.In our study, normal hearing was defined as air-conduction pure-tone audiometry (PTA) threshold of 25 dB HL or less from 0.5 to 2 kHz. The average PTA threshold was defined as the average air conduction threshold at 0.5, 1, 2, and 4 kHz. In the NH group, all subjects had normal hearing in their bilateral ears . All patThe SIN recognition test was implemented using the Hearing-in-Noise Test , which was administered in a soundproof booth. The speech material was the Mandarin HINT  were horizontally placed in a 180° arc in front of the subjects, with the subject as the center, with a radius of 1 m. The height of the sound field speakers was consistent with the height of the subject's ears. During the test, the subjects were instructed to remain still and face forward. Low-frequency (0.5 kHz) and high-frequency (3 kHz) pure tones at 50 dB HL were randomly presented two times from each of the 13 speakers as sound stimuli. After each sound stimulus, subjects were instructed to determine from which speaker the sound came and report the speaker number. When the deviation between the speaker location reported by the subject and the actual position of the stimulus was ≤ 15°, the answer was defined as correct. The correct rate was recorded as the accuracy of sound localization (ASL). The root-mean-square (RMS) error between the azimuth of the speaker location and the listener's response was also used to quantify localization accuracy. A higher ASL value indicated better sound localization ability, while a higher RMS error indicated greater deviation in identifying the sound source position, suggesting poorer sound localization capability.2; and sampling matrix = 80 × 80. The resting-state scan lasted 368 s (184 volumes). Three-dimensional T1-weighted magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) coronal images were collected by using the following settings: slice thickness = 1.0 mm without gap; TR = 7.6 ms; TE = 3.7 ms; FA = 8°; FOV = 256 × 256 mm2; and sampling matrix = 256 × 256 × 180.All MRI data were acquired on a 3 T Philips Achieva MRI scanner  with a 32-channel head coil. Subjects were instructed to remain still in a supine position. Headphones and foam padding were used to reduce scanner noise and limit head motion. Subjects kept their eyes closed but remained awake during scanning. Resting-state functional images were collected axially using an echo-planar imaging (EPI) sequence with the following settings: 37 slices; slice thickness = 3.5 mm; gap = 0.5 mm; repetition time (TR) = 2,000 ms; echo time (TE) = 30 ms; flip angle (FA) = 90°; field of view (FOV) = 230 × 230 mmhttp://www.fil.ion.ucl.ac.uk/spm). The first 10 volumes of the acquired fMRI images for each subject were discarded for magnetization equilibrium and the subject's adaptation to scanning noise. Then, slice timing and motion correction were performed. All participants were retained under the head motion criteria of translation <2 mm or rotation <2° in any direction. The remaining fMRI time series was coregistered to the T1 images. Then, the T1 images were normalized to the Montreal Neurological Institute (MNI) space, and the resulting deformation fields were used to project the functional images to the MNI space with a voxel size of 3*3*3 mm. Nuisance covariate regression including Friston 24 parameters  Brain Imaging (DPABI V5.1)  . The age differences among individuals in the three groups were tested by analysis of variance (ANOVA). Sex and handedness differences among individuals in the groups were analyzed by the chi-square test and Fisher's exact test, respectively. The differences in education time among individuals in the groups were analyzed by the Kruskal–Wallis test. The differences in age and auditory parameters among individuals in the three groups were tested by analysis of variance (ANOVA), and then t-test to compare the difference in higher-order hearing abilities of SSD patients with durations of deafness <3 years (including 3 years) and those with durations of more than 3 years. Considering that the duration of deafness in SSD did not conform to a normal distribution, Spearman's rank correlation analysis was used to explore the correlation between the duration of deafness and higher-order hearing abilities.To explore the effect of deafness time on higher-order hearing abilities, we took the median duration of deafness (3 years) as the time point and used a two-sample http://rest.restfmri.net). To explore the within-group ALFF pattern, one-sample t-tests were performed on the individual ALFF maps in a voxelwise way for each group. The within-group statistical threshold was set at Z > 3.09  . GRF correction was used for correcting multiple comparisons, and this correction was also confined within the group gray matter mask. To further observe the different trends of the ALFF values between groups, region-of-interest (ROI)-wise two-sample t-tests were performed. The ROI was defined as a sphere with a radius of 10 mm (containing 171 voxels) and centered at the peak point of clusters in each contrast.An ALFF analysis was performed with the Resting-State fMRI Data Analysis Toolkit  with GRF correction  of the PROCESS (v3.3) macro in SPSS , age , handedness , or education time . The duration of deafness  and the age of deafness onset  were not significantly different between patients with LSSD and RSSD.As presented in F = 1.54, p = 0.223). For the SIN recognition evaluation, the SIN threshold of NHs was significantly lower than that of patients with LSSD and RSSD , suggesting better performance in NHs. In the sound localization evaluation, NHs showed significantly higher ASL than did patients with LSSD or RSSD  and significantly lower RMS error than patients with LSSD or RSSD . Both results suggest better sound localization abilities in NHs than in patients with SSD, whether left or right. There was no difference between patients with LSSD and RSSD in the average PTA of the normal ear, SIN threshold, ASL, or RMS error.The results of auditory ability are presented in t = 0.14, p = 0.257). Although the SSD patients with deafness durations <3 years had lower average PTA both for deaf ears  and for normal ears  than SSD patients with longer deafness durations, SSD patients with longer deafness durations showed a significant reduction in RMS error , a marginally significant reduction in the SIN threshold , and a marginally significant increase in ASL  than SSD patients with deafness durations of <3 years  and RMS error , indicating that duration was positively correlated with hearing abilities. However, there was no significant correlation between ASL and duration of deafness .The results of higher-order hearing abilities in SSD patients with different durations of deafness are shown in ears see . The resThe within-group ALFF patterns of NHs, patients with LSSD, and patients with RSSD are shown in Z = −4.13; cluster size = 81 voxels)  and the left middle frontal gyrus  , and patients with RSSD exhibited lower ALFF values than NHs by a statistically nonsignificant margin   and MFG , and patients with LSSD showed lower ALFF values in the ROIs of the LING  and MFG  but without statistical significance  see . The patels) see . To furt328) see . Patientance see .pr = 0.77, p < 0.001) between ALFF values and duration of deafness  and positive correlations  between SIN thresholds and ALFF values  and positive correlation  between ASL and ALFF values is displayed  between RMS error and ALFF values is displayed in the bottom panel.Correlations between ALFF values and higher-order hearing abilities in all SSD subjects are also shown in lues see . A signilues see . The scaayed see . A signiayed see . The scap = 0.044). Furthermore, the indirect effect of duration of deafness on RMS error was significant [95% CI = ], while duration of deafness had no significant direct predictive effect on RMS error in the mediation model . Therefore, ALFF values in the PCUN are a significant mediator of the relationship between the duration of deafness and RMS error. However, ALFF values in the PCUN showed no significant mediating effect in the relationship between duration of deafness and SIN threshold [95% CI = ] or in the relationship between duration of deafness and ASL [95% CI = ]  could be detected by the peripheral auditory system in patients with SSD. Since these cues are crucial for sound localization and SIN recognition, these hearing abilities are most affected in patients with SSD  showed higher ALFF values in brain regions of the default-mode network (DMN), including the PCUN, IPL, PCG, and MPFC, as well as occipital areas, which were consistent with previous studies of ALFF  and the National Natural Science Foundation of China (Grant No. 82171156).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


GBD 2019 Colorectal Cancer Collaborators. Global, regional, and national burden of colorectal cancer and its risk factors, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019. Lancet Gastroenterol Hepatol 7: 627–472022; —The affiliation details for Mihajlo Jakovljevic have been corrected online as of July 6, 2022.


Zebrafish possess the innate ability to fully regenerate any neurons lost following a retinal injury. This response is mediated by Müller glia that reprogram and divide asymmetrically to produce neuronal precursor cells that differentiate into the lost neurons. However, little is understood about the early signals that induce this response. Ciliary neurotrophic factor (CNTF) was previously shown to be both neuroprotective and pro-proliferative within the zebrafish retina, however CNTF is not expressed following injury. Here we demonstrate that alternative ligands of the Ciliary neurotrophic factor receptor (CNTFR), such as Cardiotrophin-like cytokine factor 1 (Clcf1) and Cytokine receptor-like factor 1a (Crlf1a), are expressed within Müller glia of the light-damaged retina. We found that CNTFR, Clcf1, and Crlf1a are required for Müller glia proliferation in the light-damaged retina. Furthermore, intravitreal injection of CLCF1/CRLF1 protected against rod photoreceptor cell death in the light-damaged retina and induced proliferation of rod precursor cells in the undamaged retina, but not Müller glia. While rod precursor cell proliferation was previously shown to be Insulin-like growth factor 1 receptor (IGF-1R)-dependent, co-injection of IGF-1 with CLCF1/CRLF1 failed to induce further proliferation of either Müller glia or rod precursor cells. Together, these findings demonstrate that CNTFR ligands have a neuroprotective effect and are required for induction of Müller glia proliferation in the light-damaged zebrafish retina. The zebrafish retina possesses the ability to regenerate all retinal cell types following injury . Regenervia the Stat3, MAPK, and PI3K pathways (gp130 in the damaged zebrafish retina decreased Müller glia proliferation (One pathway of particular interest is the ciliary neurotrophic factor receptor (CNTFR) mediated signalling pathway. CNTFR is a tripartite receptor that binds a ligand, which recruits both Il6st (Gp130) and M17 (LIFR), resulting in CNTFR phosphorylation . This alpathways , all of pathways . CNTFR wpathways . Severalferation , suggestferation . CNTF trferation  and humaferation . Additioferation , with CNferation . Interesferation . Finallyferation .in vivo, cntf was not shown to be expressed within the regenerating zebrafish retina, however, the alternative CNTFR ligands Cardiotrophin-like cytokine factor 1 (Clcf1) and Cytokine receptor-like factor 1a (Crlf1a), which form a ligand complex, were expressed within the retina following injury  until unresponsive to tail pinch and intravitreally injected every 12 h with 0.5 µl of either PBS (vehicle), 1 mg/ml recombinant mouse CLCF1/CRLF1 , 1 mg/ml recombinant human IGF-1 , or a combination of both, using a 2.5 µl syringe with 33-gauge rounded needle  and then maintained at 32°C. Eyes were collected 72 h after the initial injection (hpi). For light treatments, dark-adapted albino zebrafish received intravitreal injections every 12 h for 48 h, at which point the fish were exposed to constant light and received an additional injection at 12 h of light treatment. These eyes were collected at 24 h of light treatment. For EdU treatment, fish received intraperitoneal injections of 1 mg/ml EdU using a 30-gauge needle while simultaneously receiving intravitreal injections of CLCF1/CRLF1 every 12 h and eyes were collected at 72 h hpi.Adult albino; Tg[gfap:EGFP]nt11 zebrafish were intraperitoneally injected with 50 µl of either 5% DMSO (vehicle) or 500 µM NVP  every 12 h throughout the course of either constant light treatment or intravitreal injection of CLCF1/CRLF1, using a 30-gauge needle. For light treatment experiments, the initial intraperitoneal injection of NVP corresponded with the commencement of light treatment and the final injection occurred at 24 h of light treatment, with the eyes collected at 36 h of light treatment. During CLCF1/CRLF1 treatment, intraperitoneal injections of NVP were performed simultaneously with intravitreal CLCF1/CRLF1 injections every 12 h and the eyes were collected at 72 hpi.albino; Tg[gfap:EGFP]nt11 zebrafish were intravitreally injected with 0.5 µl of either standard control, cntfr, a mixture of clcf1/crlf1a, or a combination of all 3 translation-blocking morpholinos . Eyes were then electroporated as previously described  in PBS for 10 min, then permeabilized by washing in 0.5% Triton X-100  in PBS for 20 min. Slides were then labelled using the Click-iT EdU labeling kit , per the manufacturer’s instructions, and washed in 3% BSA for 5 min before blocking and continuing with immunohistochemistry as described above.in situ hybridization was performed using the RNAscope Multiplex Fluorescent v2 Assay  according to the protocol for fixed-frozen tissue sample preparation with some modifications (RNA ications . Tissue Slides were washed and rehydrated in PBS and fixed in 4% PFA for 5 min at room temperature. Slides were washed 3 times for 5 min in PBS and permeabilized for 15 min in PBS-T (5% Tween-20) at room temperature. Slides were washed 3 times for 5 min in PBS and incubated for 30 min with 1:150 proteinase K  in PBS at room temperature. Slides were then washed 3 times for 5 min in PBS, before the TUNEL protocol was performed as described previously .t-test or a one-way ANOVA with a Tukey or Dunnett post hoc test. A p-value of less than 0.05 was considered significant. The mean ± SEM for each experiment is stated in the text of the appropriate Results section and the sample size (n) is stated in the appropriate figure legend.A Nikon A1 confocal microscope, equipped with a ×40 plan-fluor oil immersion objective, was used to acquire 6.5 μm z-stacks in 0.8 μm steps, of 1024 × 1024 images of the central-dorsal region of the retina. Counts were performed manually using Fiji software throughout the 6.5 μm z-stack and normalized to a 300 μm length of the retina as previously described . StatistWe used scRNA-seq data from whole light-damaged retinas that was previously published . scRNA-scntf in any of the retinal cell types (clcf1 and crlf1a primarily within activated Müller glia (hbegfa and lepb (m17 gene) was expressed predominantly in microglia and not in Müller glia  was primarily limited to activated Müller glia, vascular endothelial, retinal pigmented epithelium, and pericytes, suggesting these cells are particularly sensitive to Gp130-mediated signalling. Together, these data suggest that Clcf1 and Crlf1a are released from activated Müller glia following injury and potentially interact with a variety of different cell types within the retina.To investigate the spatial expression of CNTFR ligands in the light-damaged retina, we analyzed previously published scRNA-seq datasets . We did ll types . In contler glia , suggestand lepb . In contler glia . To begiebrafish , lifra wler glia . Finallyclcf1 and crlf1a, and several associated genes, in both resting and activated Müller glia, as well as across the damage time course within the activated Müller glia population. Both clcf1 (p < 1.00 × 10−200) and crlf1a (p < 1.00 × 10−200) exhibited a significant increase in expression within the activated population of Müller glia (clcf1 and crlf1a expression were upregulated by 10 h and 4 h of light damage (cntf was observed in either resting or activated Müller glia (clcf1 expression was significantly increased (p = 7.40 × 10−183) in activated Müller glia in the light-treated mouse retina (crlf1 expression was significantly decreased (p = 0.03) in activated Müller glia relative to resting Müller glia  and increased from 10 through 36 h of light treatment. Similarly, il6st significantly increased in expression in activated Müller glia (p = 2.80 × 10−71) from 4 through at least 36 h of light treatment . No change was observed in Lifr expression (Il6st expression was significantly increased within activated Müller glia (p = 3.80 × 10−11).In the zebrafish retina, expression of the receptor components cntfr  and lifrr , 10, 20, or 36 h before eyes were collected and retinal sections were labeled for either clcf1 or crlf1a, GFP, and PCNA. A broad and low level of clcf1 expression was detected at 0 h ) from 10 through 20 h  or 1 mg/ml CLCF1/CRLF1 every 12 h until 48 h after the initial injection, at which point fish were placed in constant intense light. They received a further injection at 12 h of constant light and eyes were collected 12 h later (24 h light treatment). To quantify cell death, we performed the TUNEL assay on retinal sections (p = 0.0005). This demonstrates that clcf1/crlf1a co-expression by zebrafish Müller glia may be neuroprotective in the light-damaged retina.Previous studies determined that CNTF is neuroprotective within both the zebrafish and mammalian retinas . We examsections . We obsealbino; Tg[gfap:EGFP]nt11 fish were electroporated with either standard control morpholino (S.C. MO) , the clcf1/crlf1 MO group , and the Triple MO groups (p = 0.0072). There was no significant difference between the cntfr MO, clcf1/crlf1 MO, and the Triple MO groups. This suggests that both the receptor and the Clcf1/Crlf1a ligands are required for Müller glia proliferation following light-induced damage. Additionally, this result suggested that while Clcf1/Crlf1a co-expression may be neuroprotective in the light-damaged retina  , which dS.C. MO) , cntfr mrpholino , a combilf1a MOs , or a milf1a MOs  before bd retina , it is nalbino zebrafish with either S.C. , suggesting that the reduced number of proliferating Müller glia in either the cntfr, clcf1/crlf1a or the Triple morphants was not due to decreased cell death, but rather their requirement for stimulating Müller glia proliferation, with Clf1/Crlf1a likely acting as ligands for CNTFR in the light-treated retina.We next examined whether the reduction in Müller glia proliferation was a result of reduced cell death in the morphants by electroporating her S.C. , cntfr  or EdU-positive Müller glia (p = 0.09) between vehicle and CLCF1/CRFL1-treated groups. This suggests that CLCF1/CRFL1-mediated signalling was insufficient to induce Müller glia proliferation. However, we observed a significant increase in the number of PCNA-positive ONL cells (p = 0.0008) and EdU-positive ONL cells (p = 0.0014) in the CLCF1/CRFL1-injected retinas relative to vehicle control. These proliferating ONL cells may represent rod precursor cells that produce rod photoreceptors during persistent retinal neurogenesis . However, there was a significant decrease in the number of proliferating rod precursor cells in the NVP-treated group relative to vehicle control (p < 0.0001). This suggests that CLCF1/CRFL1-induced rod precursor cell proliferation was IGF-1R dependent. To confirm that increased rod precursor cell proliferation was not a product of increased Müller glia proliferation, dark-adapted albino; Tg[gfap:EGFP]nt11 zebrafish were placed in constant intense light treatment, while also receiving intraperitoneal injections of either DMSO (p = 0.54), suggesting that inhibiting IGF-1R does not affect Müller glia proliferation. This is consistent with scRNA-seq data that revealed little expression of either igf1 or the associated receptor components (igf1ra and igf1rb) in Müller glia in the light-damaged retina (Previous studies showed that rod precursor cell proliferation requires Insulin-like growth factor 1 receptor 1 (IGF-1R) . To detevehicle;  or the Ivehicle; . Fish reher DMSO  or NVP , indicating that IGF-1 was not sufficient to induce rod precursor cell proliferation. However, there was a significant difference in the number of proliferating rod precursor cells between the PBS and Clcf1/Crlf1a-treated groups , and PBS and IGF-1/Clcf1/Crlf1a-treated groups . Additionally, a significant increase in the number of proliferating rod precursor cells was observed between Clcf1/Crlf1a and IGF-1-treated groups (p = 0.036), and the IGF-1/Clcf1/Crlf1a and IGF-1 groups (p = 0.013), but there was no significant difference between the Clcf1/Crlf1a and IGF-1/Clcf1/Crlf1a-treated groups (p = 0.99). This suggests that although Clcf1/Crlf1a-induced rod precursor cell proliferation is IGF-1R-dependent, addition of IGF-1 does not induce further proliferation of rod precursor cells.Since Clcf1/Crlf1a-dependent rod precursor cell proliferation is IGF-1R-dependent, we examined if co-injection of IGF-1 and Clcf1/Crlf1a was sufficient to induce further proliferation. Previous studies demonstrated that IGF-1 synergizes with FGF2 to induce significant Müller glia proliferation within the zebrafish retina , therefoferation . We obseThis is the first demonstration that the Ciliary neurotrophic factor receptor (CNTFR) ligands Cardiotrophin-like cytokine factor 1 (Clcf1) and Cytokine receptor-like factor 1a (Crlf1a) are required for retinal regeneration. We investigated expression of these ligands and their corresponding receptor components within the damaged retina and showed that Clcf1 and Crlf1a are neuroprotective, are required for Müller glia proliferation, and can induce rod precursor proliferation in an IGF-1R-dependent manner.clcf1 and crlf1a are expressed in Müller glia-derived precursor cells at 96 h post injury (clcf1 and crlf1a are expressed rapidly following retinal damage with Müller glia expressing these ligands as early as 4 h post injury and maintaining expression until at least 36 h post injury. This expression pattern was further confirmed by in situ hybridization, which demonstrates co-expression of clcf1 and crfl1a in proliferating MG, indicating that these ligands are expressed specifically in activated MG. In contrast, we observed little expression of cntf, which was previously shown to be neuroprotective in both mammalian (Previously, it was demonstrated that both t injury , howeverammalian  and zebrammalian  and can ammalian . This suclcf1 and crlf1a significantly reduced Müller glia proliferation following light treatment, however intravitreal injection of CLCF1/CRLF1 was insufficient to induce Müller glia proliferation in the undamaged retina. Therefore, Clcf1 and Crlf1a are necessary, but not sufficient, for the induction of Müller glia proliferation. Clcf1 and Crlf1a have also been shown to be required for optic nerve regeneration (Similar to the effects of CNTF , intravineration , suggestneration , althougneration .igfra is required for Müller glia proliferation following injury (Despite the inability to increase Müller glia proliferation, intravitreal injection of CLCF1/CRLF1 did induce a significant increase in rod precursor cell proliferation. A similar increase in rod precursor cell proliferation was observed following intravitreal CNTF injection . It has g injury , howevercntfr at 96 h post injury (cntfr, however in situ hybridization demonstrated that cntfr is expressed throughout the retina at all timepoints studied. Knockdown of cntfr also demonstrated that CNTFR is required for Müller glia proliferation. We observed a significant increase in expression of lifrb and il6st within activated Müller glia, and in situ hybridization confirmed that il6st is expressed throughout the retina at all timepoints. These findings suggest that Müller glia, and likely most cell types of the retina, are sensitive to CNTFR ligands. This is further supported by transcriptional changes in multiple cell types following CNTF exposure in the mouse retina (To better understand how these ligands operate within the zebrafish retina, we also investigated expression of the receptor complex components. NPCs have previously been shown to express t injury . Within e retina .Together this data suggests a model in which Müller glia respond to injury by producing the CNTFR ligands Clcf1 and Crlf1a, which play a dual role within the regenerating retina showing both neuroprotective and pro-proliferative properties. Based upon expression of receptor components, Clcf1 and Crlf1a can signal to most cell types. It has previously been shown within the mouse retina that the neuroprotective effects of CNTF require GP130 within Müller glia , therefo


Noise-induced hearing loss (NIHL), caused by direct damage to the cochlea, reduces the flow of auditory information to the central nervous system, depriving higher order structures, such as the hippocampus with vital sensory information needed to carry out complex, higher order functions. Although the hippocampus lies outside the classical auditory pathway, it nevertheless receives acoustic information that influence its activity. Here we review recent results that illustrate how NIHL and other types of cochlear hearing loss disrupt hippocampal function. The hippocampus, which continues to generate new neurons (neurogenesis) in adulthood, plays an important role in spatial navigation, memory, and emotion. The hippocampus, which contains place cells that respond when a subject enters a specific location in the environment, integrates information from multiple sensory systems, including the auditory system, to develop cognitive spatial maps to aid in navigation. Acute exposure to intense noise disrupts the place-specific firing patterns of hippocampal neurons, “spatially disorienting” the cells for days. More traumatic sound exposures that result in permanent NIHL chronically suppresses cell proliferation and neurogenesis in the hippocampus; these structural changes are associated with long-term spatial memory deficits. Hippocampal neurons, which contain numerous glucocorticoid hormone receptors, are part of a complex feedback network connected to the hypothalamic-pituitary (HPA) axis. Chronic exposure to intense intermittent noise results in prolonged stress which can cause a persistent increase in corticosterone, a rodent stress hormone known to suppress neurogenesis. In contrast, a single intense noise exposure sufficient to cause permanent hearing loss produces only a transient increase in corticosterone hormone. Although basal corticosterone levels return to normal after the noise exposure, glucocorticoid receptors (GRs) in the hippocampus remain chronically elevated. Thus, NIHL disrupts negative feedback from the hippocampus to the HPA axis which regulates the release of corticosterone. Preclinical studies suggest that the noise-induced changes in hippocampal place cells, neurogenesis, spatial memory, and glucocorticoid receptors may be ameliorated by therapeutic interventions that reduce oxidative stress and inflammation. These experimental results may provide new insights on why hearing loss is a risk factor for cognitive decline and suggest methods for preventing this decline. Intense noise primarily damages the sensory hair cells and spiral ganglion neurons; their destruction reduces the flow of acoustic information to numerous structures within the central auditory pathway as well as other parts of the brain that utilize auditory information to carry out complex processes such as formulating an emotional response to a baby’s cry, reacting viscerally when called to supper or exiting a train when your station is announced over the intercom. In order to respond effectively in these situations, the neural activity relayed through the ascending auditory pathway must be quickly and continuously integrated with information being processed in other parts of the brain such as those involved with motor control, cognition, emotion, and memory.The hippocampus is generally considered as a structure involved in the formation of new memories, cognitive maps, and spatial navigation. Although the hippocampus lies outside the classical auditory pathway, it nevertheless responds to sound , generating recurrent negative feedback inhibition that dampens the activity of the pyramidal cells. Neurological conditions that reduce recurrent inhibition from the basket cells can lead to hyperactivity in pyramidal cells resulting in epileptic seizures and hippocampal sclerosis  if the current tone was the same as the previous tone Sakurai, . AlternaHippocampal place cells preferentially fire action potentials when an animal enters a specific location in its environment. The specificity and reliability of place cell firing is affected by information gleaned from external and internal sensory cues acquired by navigating through the environment on multiple occasions. Place cell performance is often evaluated in rodents using an eight-arm radial maze with food bait placed in one or more arms of the maze. While traversing through the maze, olfactory and somatosensory systems provide useful proximal cues while vision provides distal information  revealed significant cognitive impairments on the Morris Water Maze test several months post-exposure , a prolonged increase in synaptic strength that occurs following repeated stimulation of a synapse such as the Schaffer-CA1 or perforant-dentate synapses. LTP has been considered a form of synaptic learning and memory. Repetitive auditory stimulation can influence hippocampal function  is likely to cause significant hearing loss and hair cell damage  is repeatedly turned on (4-h) and off (20 h) for 30 days, CORT levels are chronically elevated. CORT levels are the highest 30 min after the noise is turned off on day1 . CORT meThe consequences of persistent exposure to intermittent noise are illustrated by a study in which rats were exposed for 15 days to 100 dB SPL noise for 2 h/day. The rats were then evaluated 15-days post-exposure when they exhibited a relatively mild NIHL  is expected to surge creating tremendous social and economic burdens  increases in Aβ and amyloid precursor protein in the rat hippocampus after chronic noise stress (100 dB SPL, 4 h/day, 28-days; Cui et al., While this review has focused on NIHL as a disruptor of neurogenesis and memory, other types of peripheral hearing losses that deprive the hippocampus of auditory information might be expected to have similar effects. Indeed, clinical studies indicate that prolonged conductive hearing impairment in early life contributes to chronic auditory processing deficits, poorer social skills, language, reading, and cognitive deficits (Zinkus and Gottlieb, Clinical reports suggest that temporary conductive hearing loss in early life, when the nervous system is rapidly developing, could contribute to permanent cognitive and memory deficits (Reichman and Healey, in vivo to rodents robustly suppressed cell division and neural progenitors in the dentate gyrus. Cisplatin also damaged synapses, increased pro-apoptotic gene expression and enhanced cell death for at least 6 weeks following treatment (Dietrich et al., Many drugs used clinical to treat cancer such as platinum-based antitumor drugs or life threatening bacterial diseases such as aminoglycoside antibiotics are ototoxic Rybak, . These dOther ototoxic drugs such as the aminoglycoside antibiotics induce serious side effects such as nephrotoxicity, neurotoxicity, anemia, and thrombocytopenia (Snavely and Hodges, If NIHL and other forms of peripheral hearing loss impair memory and increases the risk of dementia, then hearing restoration could conceivably slow or reverse these losses. Among elderly patients with profound postlingual deafness, only 25% had normal cognitive scores prior to cochlear implantation (Mosnier et al., Hearing aids assist individuals with moderate hearing loss to understand speech in quiet and noise by reducing the cognitive load (Glick and Sharma, Although there is considerable interest in identifying pharmacological interventions to prevent dementia and AD, life style changes in the form of increased physical activity may offer significant benefit. Exercise greatly enhance neurogenesis, learning and memory in animal models (van Praag et al., The animal studies discussed in this review indicate that chronic or acute noise exposure can suppress hippocampal neurogenesis and impair spatial learning and memory, but further work is needed to address a number of important questions. In cases of significant permanent NIHL, the literature indicates that these deficits persist up to 3–4 months post-exposure, but longer duration studies are needed to determine if these deficits continue or improve with longer recovery times. If the deficits get worse over time, then it would be important to evaluate potential mechanisms that contribute to this decline and to identify therapeutic interventions to prevent this.The noise-induced disturbances in place cell function  represenBecause many urban environments are characterized by moderate intensity intermittent and unpredictable noise exposures that cause little threshold shift, it would be important to determine if prolonged exposure to such noise permanently disrupts neurogenesis, learning and memory. Indeed, there is growing interest in noise-exposure that cause little threshold shift due to synaptopathy that reduce the flow of auditory information to the central nervous system (Kujawa and Liberman, An important clinical question is whether the noise-induced disruptions to neurogenesis, learning and memory can be reversed by increased physical activity, an enriched environment or pharmacologic interventions and if so, what is the optimal time to do so. These and other related questions provide a framework that could be addressed in future preclinical studies.SM, DD, and G-DC: conceptualization, visualization, and writing. LL, JW, Y-CC, and LC: conceptualization and writing. RS: conceptualization, visualization, writing, and funding acquisition. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


To evaluate the clinical efficacy and safety of hydrogen inhalation in improving hearing loss in patients with long-term survival of nasopharyngeal carcinoma after radiotherapy.The eustachian tube dysfunction score, pure tone air conduction threshold, bone conduction threshold, the score of tympanogram and otoscope were prospectively observed in patients with deafness after radiotherapy only or combined radiotherapy and chemotherapy for nasopharyngeal carcinoma. Paired t test and one-way analysis of variance were used to analyze the data before and after treatment.P values were 0.0293, 0.0027, 0.0404, respectively. The mean air-bone gap, the score of otoendoscopy and tympanogram were also decreased, but the differences were not significant . Patients with radiotherapy alone and concurrent chemo-radiotherapy had significantly lower air conduction hearing threshold after hydrogen absorption . The results of air and bone hearing thresholds before, 4 and 12 weeks after hydrogen inhalation showed a descending trend. The air and bone hearing thresholds before hydrogen inhalation were 74.69 ± 27.03 dB and 45.70 ± 21.58 dB, respectively. At the 12th week, the mean values of air and bone hearing thresholds were the lowest, which were 66.88 ± 20.88 dB and 40.94 ± 18.93 dB, respectively, but there was no significant difference in air and bone hearing thresholds among all groups . After hydrogen inhalation treatment, no adverse reactions such as nosebleed, chest pain, dyspnea, nausea, vomiting, dizziness, earache and allergic reaction were observed.A total of 17 patients were observed. The median time from radiotherapy to now was 228 months, and the median time from the diagnose of deafness to now was 92 months. After 4 weeks of hydrogen inhalation, the score of eustachian tube dysfunction, air conduction and bone conduction hearing thresholds were significantly reduced, This is the first prospective study on the effect of hydrogen inhalation on hearing improvement in patients with deafness after radiotherapy/chemotherapy for nasopharyngeal carcinoma, suggesting that continuous hydrogen inhalation may be an alternative rehabilitation therapy for these patients. As one of the most common malignant tumors in the head and neck, nasopharyngeal carcinoma (NPC) is primarily treated with radiotherapy alone or radiotherapy combined with chemotherapy. Patients' 5-year survival rate can be 77.9–87.4% –4. Due t2) is the lightest and smallest gas in nature. Dole et al. , all the enrolled patients met the following conditions: (1) Diagnosed with Stage I to IVb nasopharyngeal carcinoma after pathological examinations; (2) Received conventional radiotherapy (radiotherapy) or radiotherapy combined with chemotherapy (chemoradiotherapy) 5 years ago; (3) Hearing and hearing test results before anti-tumor treatment were normal; (4) Experienced hearing loss at the age of 60 or lower, which excluded the probability of presbycusis; (5) Having inhaled hydrogen for at least 4 weeks. Patients with the following conditions were excluded from this study: (1) Severe hypertension, diabetic autoimmune disease, history of head trauma, and experience of long-time working in noisy environment; (2) Recurrence or metastasis of existing tumor(s); (3) Middle ear disease or hearing impairment developed before anti-tumor treatment; (4) Head and neck radiotherapy due to other reasons; (5) Middle ear effusion as evidenced by otoscopy.From May 2019 to October 2020, a total of 34 nasopharyngeal carcinoma patients with post-radiotherapy hearing loss from the Nasopharyngeal Carcinoma Group of the Light of Life Cancer Rehabilitation Association of Guangdong Province were enrolled in this study after signing informed consent. According to the registered clinical trial  completed the study eventually.The 17 patients, including seven males and 10 females, aged from 47 to 67 years old, with a median of 58 years old. According to AJCC (American Joint Committee on Cancer) tumor staging (7th edition), 10 cases were in Stage I, 4 cases in Stage II, 1 case in Stage III, and 2 cases in Stage IV. Eleven of the cases had received radical radiotherapy alone; and 6 cases radiotherapy combined with chemotherapy. During radiotherapy, the radiation dose of 68–72 Gy was applied to nasopharyngeal carcinoma and draining lymph node areas; 70.0 Gy to positive cervical lymph nodes; and 50.0–60.0 Gy to negative cervical lymph nodes. The patients were exposed to radiation 34 to 38 times in total once a day for five times a week, with dose fractionation set at 1.8–2.0 Gy each time. Concurrent chemotherapy was performed with the regimen 40 mg/m2 cisplatin (DDP) given through intravenous drips once a week. It has been 100 to 355 months (a median of 259 months) since the aforementioned treatment was completed. Hearing loss occurred 24 to 289 months after the completion of radiotherapy or chemoradiotherapy, with a median of 117 months. It persisted for 30–186 months, with a median of 90 months . The patThe subjects inhaled hydrogen-oxygen mixture, which contained 2.0 L/min hydrogen and 1.0 L/min oxygen , through nasal tubes in quite conditions. Daily inhalation lasted 3–6 h for 4–12 weeks, with eight cases for 12 weeks, six cases for 8 weeks and three cases for 4 weeks. The test period was divided into three periods for assessment: before hydrogen treatment, after 4 weeks of hydrogen treatment, and after 12 weeks of hydrogen treatment.Eustachian tube dysfunction questionnaire-7 (ETDQ-7) survey , 21 was Scoring was performed according to otoscope-based examination: 1 score: tympanic membrane turbidity and thickening; 2 scores: tympanic membrane congestion and indentation as well as disappearance of light cone; 3 scores: tympanic membrane effusion; and 4 scores: tympanic membrane perforation.Acoustic impedance tester was used to assess the changes in calm breathing tympanogram , 18. TymPure-tone hearing threshold testing  was carried out in a standard sound-proof chamber. With acoustic standard set at GB/T16296 and reverberation time at 0.3 ± 0.15 s, pure-tone hearing thresholds in conditions of 0.5, 1, 2, 4, and 8 kHz were tested in sequence. The average air-conduction threshold, bone-conduction threshold, and air-bone gap under 0.5–4 kHz were calculated. The average pure tone hearing threshold (PTA) of four frequencies divides hearing loss into the following levels: normal hearing is defined as the mean of pure tone hearing threshold ≤ 25 dB; 26–40 dB HL was mild hearing loss, 41–55 dB HL was moderate hearing loss, 56–70 dB HL was moderately severe hearing loss, 71–90 dB HL was severe hearing loss, and ≥91 dB HL was very severe hearing loss. Pure tone hearing threshold test by hearing detection professional testing.According to Common Terminology Criteria for Adverse Events (CTCAE-4.0 version) defined by the National Cancer Institute of U.S. Department of Health and Human Services , symptomt test. Different hydrogen uptake durations were compared using one-way analysis of variance. P ≤ 0.05 indicated that the difference is statistically significant. All analyses and figures were produced using GraphPad Prism 5.0 .Measurement data were expressed as x ± s. The data before and after hydrogen inhalation were compared by paired P < 0.05)  .P > 0.05). Tympanogram scores before and after hydrogen inhalation showed no statistically significant difference (P > 0.05)  .P = 0.0027) and 44.56 ± 19.50dB (P = 0.0404), respectively (P = 0.2079)  were 77.46 ± 28.12, 46.76 ± 20.73, and 30.70 ± 11.12 dB, respectively. After 4 weeks of hydrogen inhalation treatment, both air conduction threshold and bone conduction threshold were significantly lower than those before hydrogen inhalation, being 73.35 ± 28.20 dB (ectively . Among tectively . The mea 0.2079) .P = 0.0142, P = 0.6137 and P = 0.1699, respectively. P values were 0.0495 and 0.0134, respectively  were separated to radiotherapy group (22 ears) and concurrent chemoradiotherapy group (12 ears). The average air-conduction threshold, bone-conduction threshold and air-bone gap of the radiotherapy group before hydrogen inhalation were 76.70 ± 28.25, 47.05 ± 22.30, and 29.66 ± 9.86 dB, respectively. After 4 weeks of hydrogen inhalation, the air-conduction threshold showed decline with significant difference  were treated with hydrogen inhalation for 12 weeks. The results of air conduction threshold and bone conduction threshold were compared before, 4 weeks and 12 weeks after hydrogen inhalation treatment, showing a downward trend. Before hydrogen inhalation, air and bone hearing thresholds were 74.69 ± 27.03 dB and 45.70 ± 21.58 dB, respectively. At 12 weeks of treatment, the mean values of air conduction threshold and bone conduction threshold were the lowest, which were 66.88 ± 20.88 dB and 40.94 ± 18.93 dB, respectively. However, there was no significant difference in air and bone hearing threshold among all groups  were given hearing checkups 6–9 months after they stopped hydrogen-oxygen gas inhalation. According to the checkup results, the bone- and air-conduction hearing thresholds of three ears were stable or showed continuous improvement; and the hearing thresholds of seven ears increased in decibels. Average decibels of both air- and bone-conduction hearing thresholds for the affected ears were higher than before, but no significant difference was observed with vely see .No such common adverse reaction as nose bleeding, chest pain, dyspnea, nausea, vomiting, dizziness, earache or skin allergy was observed after hydrogen-oxygen inhalation. Ten patients (58.8%) complained of mild cough before hydrogen inhalation, and 11 patients (64.7%) complained of cough 4 weeks after hydrogen inhalation. Earache occurred before hydrogen inhalation in one of the cases and no change of earache after the treatment. As time passed, the aforementioned symptoms did not worsen .Nasopharyngeal carcinoma (NPC) is the most common malignant tumor of the head and neck, with more than half of the world's cases found in China. And such cases are mostly seen in southern and southeastern coastal areas of China. Currently, radiotherapy is the most effective treatment for NPC. As radiotherapy technology advances, the efficacy has improved gradually. Early-stage NPC patients'5-year survival rate may reach as high as 95% . As the Hearing loss is a major late complication for long-term surviving patients after radiotherapy or radiotherapy combined with chemotherapy. As a patient survives longer, the incidence of hearing loss increases, and hearing loss becomes more serious . The heaIn 2020, we  reportedIt is worth noting that the hydrogen inhalation is very safe. Few patients in the study experienced hydrogen-specific adverse reactions.Hydrogen inhalation by the 17 patients in this study group was carried out under strict medical supervision and was not given any other medical intervention during the entire period. Therefore, it can be concluded that the hearing improvement found in these patients is undoubtedly attributable to hydrogen inhalation.The mechanism by which hydrogen improves hearing loss in patients with nasopharyngeal carcinoma after radiotherapy or chemoradiotherapy remains unclear. However, if we connect the biological effect of radiation (or chemotherapy drugs) with the mechanism of action of hydrogen, it is not difficult to note that hydrogen represents a “tit-to-tat” “pathogenesis treatment” for post-radiation hearing loss.First of all, hydrogen has anti-oxidant and anti-inflammatory effects that resist oxidative stress and inflammation caused by radiotherapy. In the process of radiotherapy, reactive oxygen species (ROS), especially hydroxyl radicals (OH-) and peroxy-nitrosamine, are generated in large volume. Excessive levels of ROS destroy the composition of mitochondrial electron transport chains; trigger imbalance of intracellular redox systems ; and cauThe dose of radical radiotherapy for nasopharyngeal carcinoma is far higher than the normal tissue tolerance dose. Therefore, oxidative stress, inflammation and fibrosis that accompany radiotherapy inevitably damage the auditory system in the radiation field –39, leadHydrogen molecule is a weak reducing agent with very low molecular weight. It can quickly diffuse and pass through cell membranes and lipid bilayers; reach cell nuclei and mitochondria where abundant invasive ROS gather; and selectively neutralize highly reactive toxic ROS (such as ∙OH) directly . FurtherAccording to the findings of existing studies, hydrogen treatment helps significantly mitigate hearing loss caused by cisplatin; reduce Organ of Corti hair cell damage from cisplatin; improve levels of malondialdehyde (MDA) and isoprostanes F2α (8-iso-PGF2α) in serum and cochlea tissues ; signifiSecond, hydrogen has cytoprotective activity that improves cell apoptosis induced by radiotherapy. Apoptosis plays an important role in progression of radiation injury. Hydrogen significantly inhibits ectopic expression of death promoter Bcl-2 related X protein (bax) and expression of caspase-3, and meanwhile, promotes expression of the anti-apoptotic protein Bcl-2, thereby achieving cytoprotective activity , 51.Third, hydrogen improves blood perfusion and alleviates vascular damage as a result of radiotherapy. Vascular injury and endothelial dysfunction play key roles in development of radiation injury . Within Evidence suggests that hydrogen protects damaged blood vessels and improves blood perfusion, including inhibiting degradation of cyclic guanosine monophosphate (cGMP) through phosphodiesterase, increasing cGMP levels and promoting protein kinase activation. It can also increase intracellular calcium levels and stimulate vascular endothelial growth factors, thereby increasing production of nitric oxide. Moreover, hydrogen functions to open the potassium channel sensitive to adenosine triphosphate and activate downstream mitogen-activated protein kinase pathways, thus promoting angiogenesis . Further2 inhalation may further improve the therapeutic effect (There are multiple ways to introduce hydrogen into the body, including oral and intravenous injection of hydrogen water. However, since hydrogen has short half-life in the body and cannot be retained in the body's tissues for a long time, non-inhalation methods may not deliver satisfactory results. The therapeutic effects of this study group appeared at least 2 weeks after hydrogen inhalation in all the cases. From patients with long-term hydrogen inhalation, it has been observed that as hydrogen inhalation was continued for longer time, the patients' air- and bone-conduction hearing thresholds decreased more significantly. Fransson AE and his team also found repeated administration of Hc effect . After hThe concentration level and flow rate of inhaled hydrogen are also important. The hydrogen inhaled by this study group has a flow rate of 3L/min and concentration level at 67%. These are the maximum levels that can be provided by the only hydrogen inhalation equipment approved by the Chinese authority.So far, there has been no evidence as to whether inhalation of pure hydrogen is better or inhalation of hydrogen-oxygen mixture is. If high-concentration pure hydrogen is to be inhaled, oxygen intake is inevitably affected. Inhaling a mixture of hydrogen and oxygen helps at least prevent hypoxia. Studies have revealed that during inhalation of hydrogen-oxygen mixture, hydrogen molecules, which are extremely small and permeable, can “carry” larger molecules of oxygen to the deep areas of tissues and improve oxygen supply . The mixHearing loss is a common and persisting adverse reaction for nasopharyngeal carcinoma patients with radiotherapy. The hearing loss of such patients is usually long-lasting, chronical and gradual, thus affecting the quality of life in a serious manner. Unfortunately, there has been no special treatment available so far. Hydrogen inhalation can improve the hearing of long-term surviving patients with nasopharyngeal carcinoma after radiotherapy, and achieves more significant efficacy as the duration of treatment is extended. Its mechanism of action might be associated with hydrogen's functions in controlling oxidative stress and inflammation; protecting cells; and improving blood perfusion. This study represents the first effort to adopt hydrogen inhalation as an independent measure for improving hearing loss in the patients with long-term survival of nasopharyngeal cancer. If this study would be supported by more experiments and verification in the future, hydrogen inhalation would be proven a safe and effective means of rehabilitation for the challenge in the medical world.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by the Ethics Committee of Fuda Cancer Hospital, Jinan University, China. The patients/participants provided their written informed consent to participate in this study.KX developed the idea for and was involved in the design of this study. XK and TL reviewed available data sources and drafted the manuscript. Y-YL, ZY, and KX critically revised the manuscript. All authors read and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The main issue regarding pediatric audiology diagnosis is determining procedures to configure reliable results which can be used to predict frequency-specific hearing thresholds.To investigate the correlation between auditory steady-state response (ASSR) with other tests in children with sensorineural hearing loss.Prospective cross-sectional contemporary cohort study. Twenty-three children  were submitted to ASSR, behavioral audiometry, click audiometry brain stem response (ABR), tone burst ABR, and predicting hearing level from the acoustic reflex.the correlation between behavioral thresholds and ASSR was (0.70- 0.93), for the ABR tone burst it was (0.73 -0.93), for the ABR click it was (0.83-0.89) only at 2k and 4 kHz. The match between the ASSR and the hearing threshold prediction rule was considered moderate.there was a significant correlation between the ASSR and audiometry, as well as between ABR click (2k and 4 kHz) and for the ABR tone burst. The acoustic reflex can be used to add information to diagnosis in children. The attempt to early detect and identify hearing impairment is associated with the need for proper intervention, providing the child with conditions to develop speech, language, hearing and also the social, psyche and educational aspects.With the Neonatal Auditory Screening programs (NAS), together with the Auditory Health programs, we saw the possibility of early diagnosis and treatment. However, the diagnostic process can only be considered complete when one specifically identifies the type, degree and configuration of this population's hearing lossThe Brainstem Auditory Evoked Potential (BAEP) with the click and tone burst stimuli, otoacoustic emissions, Immittance values and Visual Reinforcement Audiometry (VRA) and, today, the most promising method for hearing assessment: auditory steady state brainstem audiometry (ASSBA), are all part of the set of tests  to which the child is submitted for audiological investigation.The electrophysiological measurement is the most employed tool to identify and characterize the hearing loss in the population of infants and children without cognitive and motor conditions to undergo VRA, or those who do not provide reliable responses during the test.The main issue surrounding the pediatric audiological diagnosis is to establish the procedures which provide reliable and objective results, which can be used in the prediction of hearing thresholds by specific frequency. Thus, these thresholds are applicable in the prescription of the technological characteristics of amplification, fostering the auditory and language development of children.This study aimed at correlating the ASSBA with the click and tone burst BAEP results, tonal audiometry (VRA), as well as correlating the degree of hearing loss indicated in the ASSBA as the one suggested by the hearing threshold prediction rule based on the acoustic reflex in children with different degrees of sensorineural hearing loss.The present study (research protocol # 0492/07) was submitted to and approved by the Ethics in Research Committee of Project analysis.The sample was made up of 23 children with bilateral sensorineural hearing loss, aged between 1 and 7 years, of both genders.Inclusion criteria included bilateral sensorineural hearing loss, of consistent and reliable responses upon audiometry (VRA or ludic), as well as lack of neurological dysfunction and proper middle ear function.Interacoustics, Interacoustic (AC33) audiometer with in-the-ear phone, supra-aural and bone vibrator. The audiometry was carried out in a broad acoustic room. In order to do the BAEP with click, tone burst and ASSBA we used the SmartEP - Intelligent Hearing Systems :The equipment used was the AZ7 Middle Ear Analyzer from - The procedures done were: otoscopy and tympanometry as acoustic admittance (Ya), with a 226 Hz probe frequency. In order to investigate the contralateral acoustic reflexes we employed 0.5k; 1k; 2k; 4kHz stimuli and broad band noise (white noise), recorded with the conventional probe at 226 Hz dBHL.In order to study the behavioral auditory threshold prediction based on the acoustic reflex we used the auditory threshold prediction ruleIn the Visual Reinforcement Audiometry we used in-the-ear phonesLudic tonal audiometry was carried out after two years of age with in-the-ear phones; it was necessary to condition the child in order to perform the ludic tasks (fitting), each time he/she perceived the sound stimulus.The BAEP (Click) was initially carried out in the intensity of 80 dBnHL with 20 dB increments to study the response threshold. The ground and positive electrodes were positioned on the forehead and the negative on the mastoid or on the zygomatic arc (near the ears), and the impedance was < 5kohm. The window used to study the latencies was 20ms, the stimulus presentation rate was 49.1/s; and 2000 responses were collected. The stimulus was supplied by the EAR 3A insertion phone. The polarity used was alternated. We used 30Hz high pass and 1500Hz low pass filters. The amplifier's rejection level was of 10± 25uVTone Burst) the initial intensity was 80 dBnHL, with 20dB increments or decrements used to study the threshold. The electrodes were positioned as were the click ASSBA. The window for latency study was 25ms, and the stimulus presentation rate was 37/s; and 2000 responses were collected. The stimulus was supplied by the EAR 3A insertion phones. The polarity used was rarefaction. We used filters for 1k, 2k and 4kHz  and for Tone burst of 500Hz (30-3000H)zFor the BAEP  aged between 1 and 3 years, 9 (39%) were between 4 and 5 years and 2 children (9%) were between 6 and 7 years. Of these, 15 (65%) were females and 8 (35%) were males. Values for the descriptive statistical values for age are in years and are depicted on We notice that most of the children have the same level of hearing loss in both ears. Only 1 child (4.4%) had profound hearing loss in the right ear and severe in the left; and 2 (8.7%) had severe hearing loss in the right ear and profound in the left, as depicted on The results depicted on There was a moderate agreement between the hearing loss degree classifications and the ASSBA and the rule of predicting the degree of hearing loss based on the acoustic reflex - because there was an error in the degree of hearing loss  and 5.TaIn the analysis of the correlation between ASSBA and audiometry, seen on The results obtained showed that there was a significant correlation between the ASSBA and the click BAEP; however, only for the 2k and 4kHz frequencies.We also observed a strong correlation in the literature between the ASSBA threshold in 2kHz and the click BAEP (0.96) and between the 2k and 4kHz mean with the click (0.97)Click BAEP had already been correlated with behavioral assessment and results have shown correlations with the 2k and 4kHz frequencies. The click BAEP is usually the first measure applied in the audiological evaluation of children when the behavioral auditory responses are not successfully obtained. The click is not capable enough of estimating the threshold by specific frequency within the 500 to 4kHz spectrumThe click BAEP enables one to estimate the hearing loss degree, for a proposal of initial intervention, not providing details - as information per specific frequency. One of the main limitations of the click BAEP is the lack of a specific frequency. BAEP is highly dependent on neural synchrony. ASSBA overcomes some of the BAEP limitations, since it is a response evoked by a pure tone modulated in frequency and amplitude. It is common for the examiner to decide on the presence or absence of BAEP based on wave morphology under strong intensityThe discrepancy between click BAEP and ASSBA found in the present study was clear in the cases of hearing loss with descending configuration, since the click BAEP was absent and the ASSBA showed a preservation of the auditory threshold for the frequencies of 500 and 1kHz; then, we can consider that the click BAEP underestimated the hearing in childrenThe values of the correlation coefficients between Tone Burst BAEP and ASSBA varied between 0.73 and 0.93 for the frequencies of 0.5k and 4kHz. The results are in agreement with the ones already presented in the literature, since studies have shown a 0.86 correlation between the two tests for the frequency of 0.5kHzAlthough the literature challenges the difficulty in reproducing the 500Hz frequency of the Tone Burst BAEP, in the present paper, the correlation with the AASSBA was 0.90 on the right side and 0.93 on the left side. Some authors described the morphology of the waves found as poor and which in many cases only wave V could be detected. Each change to the wave shape makes it difficult to identify and interpret the responseMoreover, they reported that the wave shape for the low frequency stimulus tends to be less differentiated and more difficult to identify its click. The output limitation for low frequencies can then limit its use in the clinical practice as a protocol. They suggested that the ASSBA is an alternative because it used the continuous stimulusThere was a moderate agreement between the ASSBA classification and the hearing threshold estimate done based on the acoustic reflex.On Although we have errors with the rule, it is worth mentioning that in no case the rule suggested normal hearing, since all the children assessed had sensorineural hearing loss. The most severe error may happen when the rule estimates the hearing to be normal in cases of severe hearing loss. A moderate error happens when the rule suggests normal hearing and there is moderate hearing loss; or when there is a severe hearing loss and the rule suggests moderate hearing loss. The errors in the hearing loss degree estimates have already been discussed in other studiesAs we compare the values of pure tones in the study of acoustic reflexes with broad band noise, it was possible to notice that in 100% of cases the broad band noise threshold was either high or absent, suggesting hearing loss. When hearing is normal, according to summation, the broad band noise threshold is less intense when compared to pure toneThe analysis of the relation between the thresholds for pure tone and for broad band noise (white noise) indicated the difference in the auditory pathway behavior after the stimulus and this analysis could add information to the children audiological diagnoses; however, the auditory threshold estimation rule based on the reflex could not have been used alonetone burst in all the frequencies, bilaterally.ASSBA was significantly correlated with the audiometry (VRA and ludic), with the click BAEP for 2k and 4kHz and with the The rule used to estimate the hearing loss can help and add information used to confirm the hearing loss, but it must not be used alone.


There are barriers to effective hearing protection among musicians.To investigate the acceptance of hearing protection aids in members of an instrumental and voice music band.A prospective study of 34 members of the Municipal Indaial Band. Sound pressure levels were measured during a rehearsal, indicating mean levels ranging from 96.4 dB(A) to 106.9 dB(A). Subjects answered questionnaires and underwent audiometry. They attended a lecture in which folders and hearing protection aids were provided; subjects were asked to try using the protectors for 3 months.At the end of the study period, 56.2% reported not liking hearing protection, while 43.7 % accepted such protection. The most common complaints were discomfort with sounds (58.8 %) and tinnitus (47%). 77.1% said that music might cause hearing impairment. A statistically significant difference was observed in the right ear at 4 and 6 kHz and at the left ear in 3, 4 and 6 kHz when median thresholds were compared with those from unexposed controls.Although most subjects seemed aware of the risk, few took preventive measures against hearing loss. This suggests the need for periodic educational campaigns and specific legislation tailored to music professionals. We usually do not think of music as being a noise, but rather as a pleasant sound. However, when played loud, it may become a potential threat to the human earThere are some differences between music and noise. In music, the temporal pattern is floating, the main frequencies are low, damped even further by the stapes, and it is usually pleasant. Noise, however, has a continuous temporal pattern, the main frequencies are high and it is unpleasant to the human ear.The association between noise exposure and occupational hearing loss has been described for more than one century, however, it was only after the 60's that some researchers showed some concern with the effects of music to hearingStudies have shown hearing loss in rock band members, sound cars, orchestras, ballroom bands, or even in individual music instruments trainingHearing loss preventive measures have been suggested to musicians based on numerous scientific researches, such as: acoustic treatment of rehearsing environments, audiologic follow up and individual hearing protection, among othersToday, musicians from Brazil and abroad have been offered specific in-the-ear protection devices. They allow for damping balance in all the frequencies, with an uniform sound reduction, avoiding the effect of occlusion and, consequently, sound distortion. Options range from simple models of standard size that offer different music damping, to customized ear protection devices.The current investigation aims at studying the acceptance of individual hearing protection devices by band members and singers during their research and performances.This investigation was carried out in the city of Indaial, involving the members of the City Band. This band is made up of 36 members, 6 women and 30 men, with ages varying between 19 and 76 years, mean age of 40 years. This study was a historical cohort with cross-sections.The band has the following members: vocal (8) persons, keyboards (1), saxophone (5), drums and percussion (3), clarinet (2), tube (1), electrical guitar (1), bass (1), trombone (5), trumpet (6), transversal flute (1), conductor (1), sound mixer (1). The band is paid by the Town Hall of Indaial, and they have an engagement with the Town Hall of 4 times per month between rehearsals and performances. We had 34 individuals participating in this investigation after having been duly informed about it and signing the informed consent form. The present study was approved by the Ethics Committee of the Tuiuti University of Paraná, under protocol # 001/2005.The participants were submitted to a questionnaire with open questions and multiple-choice questions with: identification, type of musical instrument the person plays, for how long the person had been playing the instrument , how often they rehearse and perform, individual practice, previous or concomitant exposure to industrial noise, auditory complaints, family history of hearing loss, diseases, medication use and hearing care.The questionnaire was applied by the researcher prior to the auditory assessment.a)Visual inspection of the external acoustic meatus: for that we used a Welch Allyn otoscope aiming at checking for some obstruction that would prevent the test from being carried out. If there was any alteration the subjects were referred to otolaryngological evaluation and then they returned for their audiologic evaluation.b)Audiometry: Tonal threshold audiometry was carried out in a sound proof booth, with a clinical audiometer - MAICO, model MA-41, TDH39 headphone, checked according to ISO 8253-1 standard and Resolution 296/03 of the Federal Board of Speech and Hearing Therapy. The goal of tonal audiometry was to determine the air conduction hearing thresholds in the frequencies of 250, 500, 1000, 2000, 3000, 4000, 6000 e 8000 Hz, and bone conduction in the frequencies of 500, 1000, 2000, 3000 e 4000 Hz.Audiologic assessment of the band members was carried out after an acoustic rest of fourteen hours, under the following routine:–Audiograms suggesting normal hearing: individuals who had all bilateral thresholds within the range of 25dBHL.–Audiograms suggesting noise induced hearing loss (NIHL): individuals who had hearing loss configuration (thresholds above 25dBHL) in the frequencies of 6 and/or 4 and/or 3 kHz).–Audiograms with other types of classification: individuals who had hearing loss thresholds above 25dBHL, and whose audiometric configuration did not match previous classifications.In order o classify the hearing thresholds of band members we used the criteria of audiometric alterations proposed by Fiorini (1994)In order to analyze the audiograms we excluded 11 individuals (32.3%) exposed to other noisy professional activities that are not related to music , as well as individuals with conductive hearing loss , mixed hearing loss (1 drums and percussion), and one individual with profound unilateral sensorineural hearing loss (1 drums and percussion).Of the population analyzed in this study we had 23 individuals in the study group (67.6%), exposed to music alone, who had their hearing thresholds compared to those in the control group, paired according to gender and age.For the control group we selectedWe calculated the median value of the auditory threshold in the right and left ears of the experimental and the control groups. In order to compare auditory thresholds from the control and experimental groups in both the right and the left ears, we used the Wilcoxon statistical test, and 5% (= 0.05) was the level of significance. There was no statistically significant difference between the two groups as to the age of the individuals.Sound pressure level was assessed by an engineer during a band rehearsal. The measurements were taken by means of a sound pressure level measuring device - QUEST-2700, using the fast response mode (F), and the dB scale (A), filtering method, which come close to the reception characteristics of the human ear. The rehearsal room with reverberating characteristics was divided in 18 points of measurement located in: P1(conductor), P2 (feedback+clarinets), P3 (feedback+trumpets), P4 (trombones), P5 (trombones), P6 (trombones+trumpets), P7 (trumpets), P8 (trumpets), P9 (saxophones), P10 (clarinets+flute), P11 , P12 , P13 , P14 (drums), P15 (percussion+keyboar ds+feedback), P16 (guitar+feedback), P17 (bass+feedback), P18 (sound mixer). Figure 1BWe stress that the assessment of the sound pressure levels to which the musicians are exposed to is complex and variable because it depends on environmental conditions in which the orchestra performance happens. Therefore, the measurements carried out have a merely illustrative characteristic of the potential risk associated with the exposure for these musicians. We instructed the musicians about the measurements that we were going to carry out, risks of hearing impairment with periodic exposure to intense music, basic hearing anatomy and physiology, as well as instructions and training to help them use personal protection equipment (PPE) during rehearsals and performances. During this talk we handed out to the band members the PPE, brochures with all the information necessary to properly use the PPE, information about its importance and hearing anatomy and physiology. The musicians were required to use PPE for a period of three months. The author prepared all the content of the talk and the brochures based on educational material created by the NHCA The hearing protection device selected was of the model ER-20 from E.A.R. Ultratech Earplugs . Table 1After the three months proposed for PPE use in rehearsals and performances, the participants answered another questionnaire intended to check for hearing protection device use and acceptance.As we measured sound pressure level in the rehearsal room, we observed mean values of 96.4 and 106.9 dB (A), and the highest levels of sound pressure were associated with the trumpet. Results from the measurements attained from the measurement points listed above, and also the mean values obtained are all on Of the 34 individuals in this research paper, 28 (80%) were males and 6 (17.1%) were females, with ages varying between 19 and 76 years.In Graph 1 (a), we can find the time these people spend practicing and playing music, while in Graph 1 (b) we find the time they have spent playing in this specific band, the Municipal Band of Indaial.In The hearing complaints of these musicians, singers and sound mixer operators were sound discomfort (58.8%), tinnitus (47%), hearing loss (25.7%) and a feeling of blocked ear (4%).When questioned about the possibility of music causing hearing damage, 27 individuals (77.1%) agreed with it and 7 (20%) answered negatively to it. Moreover, 9 subjects (25.7%) complained of hearing loss. Only 9 individuals (25.7%) stated they took some care of their hearing and 25 (71.4%) were not careful with their hearing. Among the care most often mentioned are: the use of PPE at work in factories, as in the practice of shooting with guns, use of cotton ball during exposure to loud music, play softly, avoid loud noises.We calculated the median values of auditory thresholds in the right and left ears of the experimental and control groups, detailed on Graph 2 (a) and (b). We performed the Wilcoxon test considering 5% (= 0.05) as a level of significance between the thresholds of both groups if p <. We notice that the difference is significant in the frequencies of 4 and 6 kHz in the right ear, and inAccording to the criterion used for audiometric alteration13 we found results suggesting hearing loss among the singers (2), trumpet (3), trombone (1), saxophone (2) and guitar (1).In order to analyze the acceptance related to wearing a hearing protection device or PPE, 32 individuals participated, of the 34 members of the band who participated in the study, 2 individuals were not present to answer the survey questionnaire, and were, therefore, taken off the study.When asked whether or not they liked wearing the hearing protection device, 18 of them (56.2%) answered no, while 14 (43.7%) said yes. The reasons for them liking or not the hearing protection are expressed on There was no statistically significant difference related to the use or not of the hearing protection device for the following factors: age range, hearing loss, type.Of the 34 individuals who underwent part of this study, many of them perform or have performed in other musical scenarios, and also in other professional noisy activities or leisure noisy activities, adding to the hearing loss. The most commonly found hearing complaints in our study were: discomfort to sound 20 individuals (58.8%), tinnitus 16 (47.06%) and hearing loss 9 (25.71%), in agreement with the literatureWhen they were asked about the possibility of music causing hearing impairment, 27 individuals (77.14%) answered yes, although only 9 individuals (25.71%) stated they took some care regarding their hearings in performances with sound amplification, sound exposure in leisure activities and/or at work in factories. We observed that the individuals in the study did not know exactly how to protect their hearing, although they knew of the possibility of having a hearing impairment because of being exposed to loud music.By analyzing the median values between the right and left ears we noticed a significant difference between the control and the experimental groups, suggesting the presence of hearing loss in the individuals who participated in the study who were exposed to music only. Such findings are in agreement with prior studiesOf the 23 individuals exposed to music only, 12 (52.1%) had hearing loss - more people than what was found in the previous work by this author involving the Municipal Band of Blumenal, with 13% of hearing lossIn other studies involving musicians, high rates of hearing loss were also observed. Among the members of the symphonic orchestra of Chicago, 42 people were found to have hearing impairment(71%)20. Of 21 musicians from varied rock bands, 11  had some hearing impairmentIn the present investigation we measured the sound pressure levels during the collective rehearsal of the band, with mean values of 96.4 to 106.9 dB(A) SPL, with peaks of up to 110.9 dB(A) SPL, according to the aforementioned measurement arrangement.In our literature review we noticed that a very complex procedure is necessary in order to measure sound pressure in music, because of its frequency and intensity variability and the level of sound the musicians are exposed to, which depends on exposure time, presentation site, collective and rehearsals, life style and other factors.When factory workers are exposed to a sound pressure level above 85 dBH, it is known that they can develop hearing loss, depending on the length of exposure§ in music, the predominant frequencies are low, less harmful because the stapes dampens the lower frequencies more effectively; in factories the noises are of higher frequencies;§ in factories the noise is continuous throughout almost the entire day, while in music, the temporal pattern is floating, music is played for shorter periods, with certain periods of peak and pause between them, when the ear can rest and recover;§ it is suggested that pleasurable sounds are less harmful than the undesired ones.However, one has to take into account that the musician will be exposed to music during his or her entire professional career, and it is paramount that he or she has normal hearing. Any type of hearing loss is undesirable, because depending on its severity it may impair the individual's perception of some sounds and tones, affecting the sound balance between the instruments20,24,25.In Brazil, we still do not have laws that protect musicians from the damage caused by loud music. The variability of opinions regarding the dangers of music to hearing makes it difficult to implement preventive actions related to music induced hearing loss (MIHL) to this type of professional.Currently in Sweden, there are two recommendations for occupational safety limits associated with work and musical activities, both for musicians and listenersIn the Brazilian A.B.N.T  standards there is nothing related to noise control in leisure activitiesThe lack of legal standards for specific sound exposure for musicians may create this false impression that this type of work environment is free from auditory risks, because all musicians would benefit from a specific pattern for hearing protectionOf the 23 individuals exposed only to music in the group studied, 12 subjects (52.1%) had hearing loss, and also other auditory symptoms.Numerous studies have shown the presence of music-induced hearing loss (MIHL), and also other hearing disorders among musicians with tinnitus, hypocusis or discomfort to loud sounds among othersIn the literature we can find some strategies for preventing hearing loss induced by noise in this type of situation19:§ Health appeal: Handouts about the harm caused by loud music to the human hearing, having the following as targets: schools and colleges, music and equipment stores, shopping malls, concert producers and promoters and medical centers.§ Engineering controls: Keeping sound pressure level around 103dB(A) in concerts, by means of lining the walls with acoustic material, and avoiding powerful high frequency amplifiers.§ Education: Educational programs for sound technicians about the risks associated with noise and measures to prevent hearing loss. Also, to encourage people to go to these places to have a 16 hour hearing rest after exposure to high levels of sound exposure.§ Individual protection: concert organizers should provide disposable ear plugs in rock concerts. Rock concert fans should consider the use of customized hearing protection devices.Hearing loss prevention among musicians still is a difficult goal to achieve, because musicians still see sound pressure levels recording in a very contradictory way, therefore they refuse to wear hearing protectionLaitinen (2005)In plants and factories, campaigns are becoming increasingly more creative, using the language of the workers to talk about their day-to-day difficulties, using strategies such as calls, posters and playsIn the present investigation, the researcher was concerned with educating and training the band members regarding the use of hearing protection, as well as in bringing to them awareness about the risks of hearing impairment caused by periodic exposure to loud music, even then she encountered resistance regarding its use, as it has been recently reported by other authorsMany complaints presented in this study are similar to those reported by users of conventional hearing protection devices: it is difficult to understand others, difficult to hear the sound of their own instrument, it prevents communication, a feeling of isolation, effect of occlusion, among others. These were complaints reported by the band members who wore the hearing protection device with uniform sound damping used in the present investigation.In the present study we may have had an effect of over-damping, that is, the protection may have provided damping above the levels needed by musicians, thus distorting the sound, bringing about this feeling of autophonia, caused by non-uniform damping to all the frequencies of the sound spectrum.We did not observe levels of statistical significance for the following factors: hearing loss, age range of the subjects and type regarding the use or not of a hearing protection device.In the present investigation we noticed that the members of the municipal band of Indaial were aware of the risks associated with the exposure to loud music, however, they did not know how to protect themselves.They seemed interested in trying the hearing protection device with uniform damping, however it was not effective because it was little used, both among those individuals with proven hearing loss detected during audiologic evaluation, as among those with hearing symptoms. We also noticed that many of the complaints reported by the subjects in this study were similar to those reported by users of conventional hearing protection devices, suggesting the possibility that the damping brought about by the protection used in the study have been higher that what was necessary, or even an effect of occlusion caused by the non-uniform damping among all frequencies of the sound spectrum. The individuals were split in regards to their continuing to wear the protection device in their professional careers. We believe that, by means of a systematic follow up of the group, periodic audiologic evaluation, new treatment and the use of other individually moldable hearing protection devices, the level of acceptability in the group could be altered. However, it is also necessary to have a law that encompasses all professionals associated with music, thus generating financial resources for the continuation of this study.