OPA8 locus, who complained of difficulties in understanding speech in the presence of noise. The patients were pooled into two groups, one consisting of 4 young adults (19–50 years) with normal hearing thresholds, and the other made up of 6 patients of an older age (55–72 years) showing mild hearing loss. Speech perception scores were normal in the first group and decreased in the second. Otoacoustic emissions (OAEs) and cochlear microphonics (CMs) recordings were consistent with preservation of outer hair cell (OHC) function in all patients, whereas auditory brainstem responses (ABRs) showed attenuated amplitudes in the first group and severe abnormalities in the second. Middle ear acoustic reflexes had delayed peak latencies in all patients in comparison with normally hearing individuals. Transtympanic electrocochleography (ECochG) recordings in response to 0.1 ms clicks at intensities from 120 to 60 dB peak equivalent SPL showed a reduction in amplitude of both summating potential (SP) and compound action potential (CAP) together with delayed CAP peak latencies and prolonged CAP duration in all patients in comparison with a control group of 20 normally hearing individuals. These findings indicate that underlying the hearing impairment in OPA8 patients is hidden AN resulting from diffuse loss of IHCs synapses. At an early stage the functional alterations only consist of abnormalities of ABR and ECochG potentials with increased latencies of acoustic reflexes, whereas reduction in speech perception scores become apparent with progression of the disease. Central mechanisms increasing the cortical gain are likely to compensate for the reduction of cochlear input.Hidden auditory neuropathy is characterized by reduced performances in challenging auditory tasks with the preservation of hearing thresholds, resulting from diffuse loss of cochlear inner hair cell (IHC) synapses following primary degeneration of unmyelinated terminals of auditory fibers. We report the audiological and electrophysiological findings collected from 10 members  of a large Italian family affected by dominant optic atrophy, associated with the  OPA1 gene (OPA1 missense mutations (Dominant optic atrophy (DOA) is amongst the most common inherited optic neuropathies, with a prevalence of about 1 in 25,000–30,000 , and is PA1 gene . MissensPA1 gene . Besidesutations .OPA1 mutations is increasingly being elucidated, and a growing list of other genes involved in the recurrent association of syndromic DOA and sensorineural deafness is being reported. This includes OPA3 with the peculiar association with cataracts  . Genome-OPA8 locus. Clinical details from all patients are summarized in We evaluated hearing function in 10 subjects  from the original family mapping at the In all subjects the onset of vision problems occurred in childhood or the late teens. The auditory symptoms appeared years later as subtle difficulties in understanding speech in noisy environments, except for subject #4, who presented auditory problems as the first symptom. At the time of evaluation, all subjects complained of difficulty in understanding speech in the presence of background noise; four patients also complained of impaired speech perception in quiet environments. Four patients reported tinnitus, whereas one complained of vertigo.Subjects underwent audiological assessment including pure tone and speech audiometry, speech perception measures and OAEs and ABRs recordings, all performed during the same session. They were submitted to ECochG recording except for subjects #8 and #9.This study was carried out in accordance with the recommendations of the local institutional ethical committee. All subjects gave written informed consent in accordance with the Declaration of Helsinki.We tested hearing thresholds at frequencies from 250 to 8000 Hz (Grason-Stadler GSI 61 audiometer) in a sound-attenuating room. The degree of hearing impairment was defined by the pure tone average (PTA) threshold levels at 0.5, 1, 2, and 4 kHz, and was classified as mild (PTA 21–40 dB HL), moderate (PTA 41–70 dB HL), severe (PTA 71–95 dB HL), and profound (PTA > 95 dB HL)  .Articulation gain curves were obtained using disyllabic, phonetically balanced words from an Italian wordlist for adults . Ten worS/N) of 0 dB.Speech perception tests were performed in a sound-attenuated room. Speech stimuli were presented in the free field through one loudspeaker placed one meter away from the front of the subject’s head. Competing background noise was presented from two additional loudspeakers placed laterally at an angle of 90° on each side of the subject’s head at one meter. Competing noise used was continuous speech noise (Interacoustics AD 229E) calibrated in the free field by means of a Brüel and Kjaer 4165 microphone (mounted on the 800 B Larson-Davis sound level meter) placed in a position corresponding to the subject’s head. Speech material comprised digital anechoic recordings of a native Italian female speaker. The speech stimulus intensity was kept at 70 dB (A). Both stimuli and noise files were stored on computer for transfer directly to the loudspeakers. Speech and noise files were normalized for output intensity levels at the signal-to-noise ratio (S/N) ratios . In the word recognition test, subjects were presented with one of four randomly chosen lists of disyllabic words, each list consisting of 25 items. The speech material was obtained from the protocol of patient candidacy for cochlear implantation for the Italian language (Tests were administered at 70 dB(A) in quiet, and in the presence of competing noise presented at three signal-to-noise . Subjects were asked to respond by repeating the speech signal perceived.We used the procedures reported in Data collected from patients were compared to the corresponding values obtained from 16 normally hearing subjects (age range 18–51 years).Acoustic reflex thresholds were measured ipsilaterally and contralaterally to the stimulated ear (Grason-Stadler GSI TympStar impedance audiometer). They were considered absent when no response was found at intensities higher than 110 dB HL.Peak latencies were measured on the averaged waveforms obtained in response to tone stimuli of 300 ms duration and 18 ms rise/fall- time which were presented at an intensity of 10 dB above threshold at frequencies of 0.5, 1, 2, and 4 kHz. Five stimuli were averaged for each waveform. Peak latency was measured at the maximum negative deflection from baseline relative to the response onset defined at the time when the immittance signal deviated from the pre-stimulus baseline .Data collected from patients were compared to the corresponding values obtained from 16 normally hearing subjects (age range 18–51 years).Distortion product otoacoustic emissions (DPOAEs) were obtained using the ILO-92 OAE system. Primary tones were presented at 70 dB SPL and the f2/f1 ratio was kept at 1.21. The frequency was increased in 1/4 octave steps from 708 to 6299 Hz. Four spectral averages were summed for each stimulus condition.Potentials were recorded from scalp electrodes  in response to 2,000 trials of alternating polarity clicks presented monaurally (TDH-50 transducer earphone) at a maximum intensity of 125 dB peak equivalent (p.e.) SPL . The filter settings of the amplifier were set between 5 and 4,000 Hz.Electrocochleography recording was carried out in 8 out of 10 patients who had signed an informed consent form. ECochG protocol was assessed by the regional body for quality control of clinical and therapeutic procedures .Under local anesthesia (lidocaine) a sterile stainless steel needle electrode (0.7 mm), insulated except for the tip, was passed through the tympanic membrane and placed on the promontory wall with the aid of an operating microscope. Stimuli consisted of 0.1 ms rarefaction and condensation clicks, delivered separately in the free field by means of two high frequency drivers (Electro-Voice DH1A/2MT 16 Ω) mounted on a single polyurethane horn (Electro-Voice HP420) at a maximum intensity of 120 dB peak equivalent (p.e.) SPL . The stimulus was calibrated in the free field by means of a Brüel and Kjaer 4165 microphone (mounted on an 800 B Larson-Davis sound level meter) placed at 1 m from the base of the polyurethane horn, which corresponded to the distance of the patient’s ear from the horn. The procedure of comparing the peak-to-peak amplitude of the click to the peak-to-peak amplitude of a 2 kHz tone was utilized to calibrate the click level (p.e. SPL) .Condensation and rarefaction clicks were delivered separately for seven intensity levels from 120 to 60 p.e. SPL. The stimulus paradigm consisted of an initial click, followed 15 ms later by ten clicks with an inter-stimulus interval of 2.9 ms, and the sequence was repeated every 191 ms .The potentials were differentially amplified , filtered  and digitized (25 μs) for averaging . The procedure of averaging the responses evoked separately by condensation and rarefaction clicks was applied to cancel the CM and extract the CAP with the superimposed SP. The resulting curve was subtracted from the potential evoked by condensation clicks to obtain the CM . Since CAfter canceling the CM, the ECochG waveform begins with the receptor SP, which appears as an initial negative deflection arising from baseline and preceding the neural CAP , 2015. LCochlear potentials recorded from patients were compared to the ECochG data previously collected from 20 children (age range 3.5–6.5 years) tested for presumed cochlear deafness, but who proved to have normal cochlear function , 2015. AAnalysis of variance (ANOVA) for repeated measures was carried out to analyze ECochG and acoustic reflex measures. Separate two-factor ANOVAs with factors of group and stimulus intensity were used to evaluate latency, amplitude and duration measures of ECochG potentials. Factors of group and tone frequency  were used to evaluate acoustic reflex thresholds and peak latencies.P < 0.05.The level of significance was Values contained in figures indicate mean ± standard error.Hearing thresholds were within normal limits in 4 subjects and appeared only mildly elevated in five . One subn = 4), whereas subjects with mild hearing loss in one ear at least  formed the second group.Subjects were pooled into two groups based on their PTA values. The first group comprised patients with normal hearing thresholds bilaterally  .In F = 0.09, P = 0.761544), whereas peak latencies were significantly delayed in OPA8 subjects compared to controls .Individual thresholds and peak latencies are compared for OPA8 patients and one control group of normally hearing individuals in Distortion product otoacoustic emissions were recorded from all but one patient (#5) . The resOPA1 gene. Peak latency values of individual ABR waves are reported in In Overall, ABR amplitudes were attenuated in all OPA8 subjects in comparison with the normally hearing control except for subject #4, who showed normal ABRs. Nevertheless, brainstem potentials showed remarkable differences between OPA8 subjects with normal hearing thresholds and those with mild hearing loss. Compared with the healthy control, the ABR waveforms from the OPA8 group with normal thresholds (PTA 10–15 dB) were markedly attenuated, but the response morphology was preserved. Indeed, Wave I was detected in all ears with normal latency; Waves III and V were identified in all subjects, although with prolonged latency in some ears . Indeed, ABR recordings showed no response in two patients, a remarkably delayed Wave V in two other subjects, while in the remaining two patients Waves III and V were recorded with prolonged latency. Wave I was detected only in one subject in this group (#6). Overall, ABR recordings resembled the brainstem potentials obtained in OPA1 patients, who displayed severe ABR abnormalities despite the relative preservation of hearing thresholds .t-test; t = 3.09612, P < 0.01).Since reduction of suprathreshold Wave I amplitude has been proposed as a measure of cochlear input decrease in auditory synaptopathy for both mice and humans , we compOPA1 gene are displayed in the right panel. In the healthy control  in OPA8 patients compared to controls, whereas SP was significantly reduced in amplitude  and delayed in peak latency . Compared to normally hearing controls, the CAP recorded in OPA8 subjects was significantly decreased in amplitude  and increased in both peak latency  and duration   . OverallThe effects of adaptation on the cochlear potentials were studied by using a stimulation paradigm at high rates . Figure Our study demonstrates that the hearing dysfunction in OPA8 patients is underlain by hidden auditory neuropathy due to degeneration of synaptic contacts between hair cells and auditory nerve fibers. This results in abnormalities of the evoked auditory nerve  and ABRs potentials, which constitutes the first sign of the disease, whereas hearing thresholds and speech perception appear to be largely unaffected at an early stage. As the disease progresses with age, hearing thresholds deteriorate, speech perception difficulties arise and both CAP and ABRs become further impaired.OPA1 gene (We have previously characterized the hearing dysfunction affecting patients with DOA due to missense mutations in the PA1 gene , who disPA1 gene , the heaAlthough complaining of subtle difficulties in understanding speech such as great effort involved in listening in the presence of noise, the youngest members of the OPA8 family showed normal hearing thresholds and speech perception scores. Interestingly, the only OPA8 patient with normal hearing thresholds who showed a remarkably reduced performance on speech perception tests, was 69 years old , and hadOtoacoustic emissions and CM amplitudes were normal in OPA8 patients, consistent with preservation of OHCs function, whereas ABRs were abnormal in all but one subject. Specifically, in the youngest patients with normal thresholds, ABR morphology was preserved with detection of the main ABR waves; however, the amplitude of ABR components was markedly attenuated. Recent studies have reported that reduction of Wave I amplitude constitutes the first sign of cochlear damage in animals exposed to noise or in aging mice showing preserved cochlear receptors . This fiAcoustic reflexes to ipsilateral stimulation were detected in all but one OPA8 patient. However, the reflex morphology in response to 300 ms-tone stimuli was abnormal, in that the first rapid deflection from baseline was almost completely abolished with consequent delay of response peak latency, which appeared significantly higher in comparison to healthy controls. Recently, ECochG recordings revealed alterations of cochlear potentials in all OPA8 subjects. Both SP and CAP showed a striking reduction in amplitude, consistent with a reduction of cochlear output. This finding accords with the suprathreshold attenuation of ABR Wave I amplitude; however, it constitutes a much more reliable index of cochlear output reduction. A decrease of SP and CAP amplitude is also apparent in cochlear deafness  because Taken together, speech perception measures and ABR and ECochG findings, may indicate that the youngest members of the OPA8 family show subtle hearing dysfunctions associated with reduction in amplitude and increase in latency of auditory evoked potentials. As the disease progresses over time, auditory perceptions worsen, ABRs are absent or show profound alterations, while CAP shows further attenuation in amplitude and increase in peak latency. Thus, alterations of ABR and ECochG potentials seem to mirror the progressive deterioration of speech perception abilities. Similar changes have been reported by ECochG recordings obtained from OPA8 patients showed profound differences in comparison to subjects harboring OPA1 mutations, who showed the typical profile of classical post-synaptic AN. In the latter, the synchronous CAP was replaced by a prolonged low-amplitude negative potential, which is believed to result from activation of damaged neural fibers . In contOverall, ECochG recordings from OPA8 family are consistent with the findings obtained by Although behavioral hearing thresholds measured in quiet environments in chinchillas were not affected until IHC loss exceeded about 40%, hearing thresholds obtained in the presence of noise were significantly elevated compared to controls in animals with small IHCs lesions. This was explained by admitting that the central auditory system is able to compensate for a small decrease in the cochlear output so that cochlear damage becomes apparent only in challenging conditions. Indeed, Similar mechanisms might come into play in OPA8 patients. In younger subjects the preservation of both hearing thresholds and speech perception may be achieved by central compensatory mechanisms counteracting the attenuation of the cochlear output, whereas in older subjects both the deterioration of hearing thresholds and the impairment of speech perception could possibly reflect a decreased effectiveness of central compensating mechanisms in counteracting a further decrease of cochlear output. This hypothesis is also supported by the findings reported by Interestingly, the data obtained in this animal model resembled the findings we collected from subject #10, who showed mild hearing loss associated with a slight reduction in speech intelligibility  togetherWe document that the hearing dysfunction affecting OPA8 patients is underlain by hidden AN, possibly resulting from terminal afferent degeneration followed by IHCs loss. The functional alterations consist of abnormalities of both ABR and ECochG potentials together with poor morphology of middle ear acoustic reflexes at an early stage of the disease, whereas mild hearing loss and impairment of speech perception become apparent only at an advanced stage. Central mechanisms are likely to counteract the decrease of peripheral input and guarantee full compensation at an early stage of the disease.These findings provide a distinctive phenotypic profile of DOA associated with the OPA8 locus as compared with the OPA1-related DOA, which was associated to the classical profile of post-synaptic AN. Elucidation of the molecular pathogenesis will certainly shed further light on the selective auditory terminals and IHCs damage in patients with OPA8-related DOA.RS and VC designed research. RS wrote the manuscript. CLM, MLV, PB, and AM performed experiments and collected data. PS analyzed data. VC provided critical revision and commented on the manuscript at all stages. All authors contributed to this work.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.


This study aimed to explore the relationship between dependence in Activities of Daily Living and muscle strength, muscle morphology and physical function in older nursing home residents, taking possible confounders into consideration.A total of 30 nursing home residents  were included in this observational cross-sectional study. Performance of basic Activities of Daily Living (ADL) was assessed with the Resident Assessment Instrument and categorized as either independent or dependent. Isometric grip, quadriceps and elbow-flexor strength were determined by hand-dynamometry, muscle thickness and echo intensity by B-mode ultrasonography, a sit-to-stand task by using a stop watch and physical activity by the German-Physical-Activity Questionnaire. Degree of frailty was evaluated according to Fried’s frailty criteria, whereas cognition, depression, incontinence, pain and falls were part of the Resident Assessment Instrument.s = -0.44, p = .015), handgrip , elbow-flexor  and quadriceps strength , analysed by Spearman’s correlation. Chronic diseases  and incontinence  were positively correlated with ADL while the other variables were not related. Only quadriceps strength remained significant with logistic regression  = 4.7, p = .03), when chronic diseases, quadriceps and handgrip strength were considered (R2 .79). 11 kg was the best fitting value in this sample to predict performance in Activities of Daily Living, evaluated with Receiver-Operating Characteristic analysis, with a sensitivity of 100% and a specificity of 79%.Dependence in Activities of Daily Living was negatively correlated with physical activity (rQuadriceps strength had a positive independent relationship with performance in ADL in the nursing home residents studied. Although a large prospective study is needed to verify the results, maintaining quadriceps strength above 11 kg may be helpful in retaining independence in this cohort. In 2017, 15.7% of the Swiss population aged 80 years and over were institutionalized , with anThe ability of nursing home residents to perform ADL independently is associated with multiple factors, both modifiable and non-modifiable, but is mainly dependent on age, chronic disease and disability, with the latter factor being the most discriminant predictor . PhysicaPrevious studies involving community dwelling older people have shown the relevance of quadriceps strength for e.g. independent performance of sit-to-stand tasks , 16 and In the present study, we aimed to investigate whether muscle structure, strength, function or physical activity were predictive variables of dependence in ADL in nursing home residents, when accounting for cognition, depression, falls, incontinence, chronic disease, sedative medication and pain.A cross-sectional study of muscle characteristics and physical function of nursing home residents was undertaken in a long-term care institution in Switzerland between August and December 2017. Recruitment targeted older adults, aged 65 years and over. Exclusion criteria were a) an inability to understand study content and provide sign informed consent; b) severely impaired decision making  ; c) a hiNursing home residents were screened by the senior nurse for exclusion criteria based on the last RAI assessment. Only participants who were deemed competent to consent and voluntarily agreed to participate were considered for study inclusion. All study procedures complied with the principles of the Declaration of Helsinki for ethical research in humans and the study received approval from the local ethics committee (project-ID 2017-00839).Details are presented in the following report, which adheres to the reporting guidelines for cross-sectional studies .Sample size was calculated a priori using published data for quadriceps strength in nursing home residents . A totalParticipant demographics, medications history, medical history and independence in ADL were obtained using of the Long-Term Care Facility Resident Assessment Instrument . For assessment of ADL, urinary incontinence, cognitive performance and depressive symptoms, observations were judged and encoded by one of four nurses who were experienced RAI-item coders. All nurses had received the same training on the use of the tool in its application. Detailed RAI items are shown in One investigator, a physiotherapist, trained and experienced in musculoskeletal assessments and ultrasonography, completed the following test series for all participants.®, CompuFET, Hoggan Health Industries, Biometrics Europe). For measurement of elbow-flexor strength, the participant was seated on a chair, elbow flexed at 90°and forearm supinated. For measurement of quadriceps strength, the participant was seated on a plinth, with their back resting against a firm support, thighs fully supported, knees flexed to 90° and the lower legs hanging freely. The curved transducer pad of a hand-held dynamometer was positioned at 80% of the forearm and tibial length respectively, to resist maximal isometric force of the elbow flexors and quadriceps. The participants were asked to push against the dynamometer as hard as possible for 3 seconds. Strength was measured in Newtons (N), and converted into Kilograms (kg) by dividing N by 9.81. Torque was calculated in Newtonmeters (Nm) by multiplying force by the lever arm length of the forearm and tibia respectively. Hand-held dynamometry has been shown to be a valid and reliable technique to assess isometric strength in older adults .Of the group that was independent in ADL (n = 16), 9 participants could complete the 5STS, while 7 could not. Of the group that was dependent in ADL (n = 14), 5 participants could complete the 5STS, while 9 were not able to complete the 5STS.s = .41, p = .027) and incontinence , but was not associated with sex, age, falls, cognitive performance, sedative medication, depressive mood, pain or physical frailty at the univariate level , lower elbow-flexor strength  and lower physical activity  but moderately correlated with lower quadriceps strength . There was no correlation of ADL dependence with muscle morphology and functional mobility/the ability to rise from a chair 5 times  and factors that were moderately correlated with ADL  at the univariate level (2 = 0.786). However, quadriceps strength was the only independent predictor of dependence with an Odds Ratio (OR) of 0.353 , indicating a 65% lower risk of being dependent when quadriceps strength increased by 1 kg . However, while poor performance on the STS test (>10–13 seconds) has been shown to predict incidence of disability in older community-living older adults , 53, itsAn isometric quadriceps strength of > 11kg predicted ADL-independence by 100% and ADL-dependence by 79% in this study sample. The findings show that quadriceps strength was of high importance for explaining the variance in ADL performance; an improvement of 1 kg lowers the risk of becoming dependent by 65%. Interventional studies have shown that exercise programs of 8–12 weeks, including resistance exercises 2–3 times weekly, were effective in increasing quadriceps strength in older, nursing home residents by a minimum of 3 kg , 22. ThuPrevious research has established that quadriceps strength differs significantly in community living older people independent in ADL (3.5–3.8 N/kg) from those partially dependent (2.2–2.9 N/kg) , when inSome limitations of this cross-sectional study should be mentioned. Firstly, observations of behavior and emotions by nursing staff entailed the risk that some actions of the participants could have been unrecognized and therefore not recorded adequately. However, the observation period included seven days in which residents were closely observed by a trained nurse attentive to precise assessment. Therefore, the risk of information bias was likely to be small. Even though RAI data were obtained by different assessors, data can still be assumed sufficiently reliable since inter-rater reliability of the RAI items has been shown to be 0.63–0.92 (weighted Kappa) . SecondlThis study has shown that strength, physical activity and incontinence were potentially modifiable factors associated with ADL dependence in nursing home residents, with quadriceps strength being the only independent predictor of dependence in ADL, independent of age, frailty status, co-morbidities and cognitive function.Although further research is required, interventions aimed at increasing these physical abilities with a specific focus on enhancing leg muscle strength beyond target threshold values may be a useful strategy for reducing dependence in ADL of nursing home dwellers.S1 Appendix(DOCX)Click here for additional data file.S2 Appendix(DOCX)Click here for additional data file.S3 Appendix(DOCX)Click here for additional data file.S4 Appendix(DOCX)Click here for additional data file.


Although signal characteristics and sensory systems are predicted to co-evolve according to environmental constraints, this hypothesis has not been tested for acoustic signalling across a wide range of species, or any mammal sensory modality. Here we use phylogenetic comparative techniques to show that mammal vocal characteristics and hearing sensitivity have co-evolved to utilise higher frequencies in forest environments – opposite to the general prediction that lower frequencies should be favoured in acoustically cluttered habitats. We also reveal an evolutionary trade-off between high frequency hearing sensitivity and the production of calls with high frequency acoustic energy that suggests forest mammals further optimise vocal communication according to their high frequency hearing sensitivity. Our results provide clear evidence of adaptive signal and sensory system coevolution. They also emphasize how constraints imposed by the signalling environment can jointly shape vocal signal structure and auditory systems, potentially driving acoustic diversity and reproductive isolation. Sensory drive theory predicts that vocal signalling coevolves with auditory sensitivity, but empirical evidence is limited. Here, Charlton et al. show that vocal characteristics and hearing have coevolved in forest mammals, due to constraints imposed by the local signalling environment. Comparative studies of mammal vocal communication have shown that variation in body size3, sexual selection pressures on male calls2, selection pressures to highlight information encoded by formants4, and social group size are all drivers of mammal vocal signal diversity6. Additional comparative work on mammals indicates that the transition to social group living may also drive the evolution of high frequency hearing sensitivity7. Another long-standing explanation for the evolution of high frequency hearing in mammals is that it improves the ability to localise sound9 particularly for smaller animals that are more reliant on high frequencies to generate differences in sound intensity reaching the two ears8. While the expectation that smaller animals have better high frequency hearing sensitivity is broadly verified across mammal species10, several exceptions, typically affecting subterranean species, have been documented. These observations indicate that mammal hearing sensitivity is not merely constrained by inter-aural distances but also likely to be driven by other factors, such as the physical environment.A prime objective of animal communication research is to determine the ultimate factors affecting signal characteristics and the sensory capabilities of receivers11 the ability to perceive low-frequency sound could be important for species that need to communicate over large distances13. Although lower sound frequencies propagate best in any environment, they are thought to be particularly favoured by selection in acoustically cluttered environments15, such as dense forests, because higher frequencies should be more consistently attenuated than they are in open habitats due to scattering and absorption by stratified media . On the other hand, selection could favour high frequency hearing sensitivity for optimal sound localisation in dense forests with poor visibility, particularly for avoiding predation and localising prey, which would also help to counteract the attenuation of higher frequencies that occurs in forest environments18 and facilitate more effective vocal communication.For example, because higher sound frequencies are degraded more rapidly than lower frequencies during atmospheric transmission19 and these frequency components extend into the upper frequency range  have the potential to signal important bio-social information about the caller31 mammal vocal characteristics should co-evolve with hearing sensitivity in a predictable direction that is determined by the local signalling environment. Sensory drive posits that the abiotic and biotic environment will influence both signal and sensory systems, which then sets the direction of signal coevolution with respect to receiver sensitivity32. Support for the complete sensory drive model can be difficult to obtain, however, because it is necessary to reveal a sensory system characteristic that arises through perceptual adaptation to the local environment, and then find signal variation predicted by environmental constraints that corresponds to this sensory bias32. In addition, to infer underlying evolutionary processes requires comparative tests that take into account the phylogenetic relationships between different species34. While this approach has been used to provide good support for coevolution between visual traits and sensory systems35, until now, use of the comparative approach to test sensory drive predictions for vocal communication systems has only considered how vocal characteristics are adapted to transmission in different habitats34. As a result, whether or not the complete sensory drive model applies to vocal communication systems is still an open question.Furthermore, according to the Sensory Drive hypothesis31, we also show that forest mammals have more high frequency acoustic energy in their vocalisations than other terrestrial mammals, to match hearing sensitivity and optimise the transfer of acoustic information. Finally, for forest mammals with available audiogram and acoustic data we reveal a negative relationship between high frequency hearing sensitivity and high frequency acoustic energy in vocalisations, which suggests forest mammals further optimise vocal communication according to their high frequency hearing sensitivity.In this study we use phylogenetic comparative techniques across a wide range of taxa to test the sensory drive hypothesis on mammal vocal communication systems. We find that forest mammals have better high frequency hearing sensitivity when compared to other terrestrial mammals living in more open environments. In line with the sensory drive hypothesisH2) = 0.09, parameter estimate (β) = −3.20, 95% Credible Interval (CI) = −5.96 to −0.47, PMCMC = 0.030)    (Supplementary Table To quantify hearing sensitivity for each species we extracted the frequency of peak hearing sensitivity (in kHz) and calculated the mean hearing threshold values (in dB) for the frequency ranges 0–20 kHz and 10–20 kHz from published audiogram data (Supplementary Table 21) Fig.  and nega37. Vocal signals with relatively more high frequency acoustic energy will have shallower spectral slopes    of the line connecting spectral peaks, termed the spectral slope32. For the 17 species with available audiogram and acoustic data we found that peak hearing sensitivity  and relative high frequency hearing sensitivity  were both negatively correlated with spectral slope values  revealed that forest mammals have greater high frequency hearing sensitivity, and also produce vocal signals with more high frequency acoustic energy than mammals that live in more open habitats. We also revealed that poorer high frequency hearing sensitivity was predictive of shallower spectral slopes in forest mammal vocalisations. These findings suggest that hearing sensitivity and vocal signal characteristics have coevolved: firstly, to facilitate effective communication of information encoded in the upper frequency spectrum in forest environments, and then in the form of an evolutionary trade-off in forest mammals between high frequency hearing sensitivity and the production of calls with high frequency acoustic energy, with decreases in one creating a selection pressure for increases in the other. Although there is some evidence that mammal vocal signals31 applies to vocal communication systems across a wide range of mammals. Comparative work on mammalian auditory anatomy indicates that high frequency hearing is an ancestral trait40. Based on this premise, we suggest that it was retained in forest mammals to optimise sound localisation in a visually occluded environment, thereby helping animals to avoid predation, localise prey, and maintain social group cohesion. High-frequency hearing sensitivity could then open up a higher frequency band for auditory communication, leading to vocal signals with more high frequency acoustic energy via sensory drive31. Boosting the amplitude of higher frequencies in vocal signals would help to counteract high frequency sound attenuation in forests17, increase the perceptual salience of formants and any information that they encode, and place less emphasis on lower frequencies for information transfer in an environment with high levels of ambient noise at and below ~3 kHz12. Broadband signals with wider frequency spectra are also thought to be easier to locate41. Hence, this co-evolutionary process would not only facilitate the transfer of acoustic information encoded by the upper frequency spectrum (i.e. formants), but could also help animals locate vocalising conspecifics in densely forested environments with poor visibility. We suggest that the evolutionary trade-off within forest species reflects a minimal need to provide accurate (i.e. perceivable) information to receivers42 while avoiding the unnecessary production of more conspicuous signals that may incur a greater risk of predation41.Our findings also demonstrate that sensory drive43. We suggest that future studies examine whether mammal vocal signals and sensory systems co-evolve in response to anthropogenic noise, or to utilise frequency ranges that are less likely to be perceived and eavesdropped upon by predators. Sensory drive acting on vocal signals to optimise the transfer of acoustic information in different acoustic environments may prove to be an important driver of mammal vocal signal diversity. It may also explain why forest mammals sometimes produce vocal signals with higher frequency components than closely related species that live in more open habitats44, despite the general consensus that lower frequencies should be favoured in acoustically cluttered habitats15. Furthermore, given that acoustic signals potentially contribute to reproductive isolation45, our findings are also consistent with the notion that sensory drive has a wider role in the diversification of mammalian lineages46. Future studies should investigate whether acoustic adaptation to forest versus open environments leads to corresponding divergence in mating preferences based on mammal vocal characteristics. A greater understanding of how vocal signal characteristics, auditory perception, and mating preferences based on vocal traits adapt to different local environments will illuminate whether sensory drive contributes to mammal vocal signal diversity and the early stages of reproductive isolation in natural mammal populations.Finally, our findings also accord well with recent comparative work that suggests hearing sensitivity in primates is not solely constrained by inter-aural distances9. It is thought that this inverse relationship exists because low-frequency sounds (with longer wavelengths) are likely to bypass smaller heads with more closely spaced ears. Smaller species  are therefore more dependent on higher frequencies for sound localization, and thus, more sensitive to high sound frequencies9. Accordingly, we took functional head size data from the same source as the audiogram data to control for this factor in the comparative analysis (Supplementary Table n = 47 species) and auditory brainstem responses (n = 4 species). Importantly, common parameters of auditory sensitivity,  such as the frequency of best sensitivity and the high-frequency limit, are comparable between the two methods47.For the comparative analyses of hearing sensitivity we collected audiogram data from the literature for 51 terrestrial mammal species  and the Macaulay library at the Cornell Lab of Ornithology (https://www.macaulaylibrary.org), or extracted from commercially available audio CDs (Supplementary Table Uncompressed audio recordings (.wav) from 116 terrestrial mammal species were downloaded from the Animal Sound Archive at the Museum für Naturkunde Berlin  or low amplitude close range vocal signals  were not retained for the acoustic analysis, and more than one call type was collected for the majority (64%) of species (Supplementary Table https://www.iucnredlist.org//). All IUCN assessments are peer reviewed by specialists (for more details refer to: https://www.iucnredlist.org/assessment/process). Species stated as occurring primarily in forest environments with no more than three potential habitats were also classed as forest mammals. The other species in our analysis were listed as occurring in grassland, savannah, scrubland, desert, mountain, rocky areas (e.g. inland cliffs and mountain peaks), marine inter-tidal zones, and wetlands  for each species to control for this factor in the comparative analyses. When body mass data were not available from published studies, we referred to the PANTHERIA v.1 database  website (For each species the frequency of maximum hearing sensitivity (peak sensitivity) in kHz and hearing sensitivity threshold values across a frequency range of 0–20 kHz were extracted from published audiogram data (Supplementary Table www.praat.org). Recordings were initially segmented into separate vocalisations using the edit window and labelling facility in Praat and saved as individual sound files (.wav). We discarded recordings with excessive environmental noise, multiple callers with overlapping spectra, and/or sounds other than the targeted vocalisations , so that a total of 3701 sound files were retained for the acoustic analysis. All the sound files were down-sampled to 40 kHz, resulting in a Nyquist frequency of 20 kHz that corresponded to our maximum hearing threshold values. The mean intensity of all audio recordings was set to 60 dB prior to the acoustic analysis.The audio processing was conducted using Praat v5.1.32  script from GSU tools script f50, with species averaged hearing sensitivity values or spectral slope entered as a Gaussian response variable, habitat (forest or other) as a binary predictor variable, and the phylogenetic relationships among species as a random effect. For the analysis of the audiogram data log10 transformed functional head size was also entered as a covariate to control for this factor. For the analysis of the acoustic data we entered log10 transformed body mass as a covariate and presumed call function as a random effect to control for these factors. A recent mammal supertree51 was used to account for common ancestry among species, and pruned prior to each of the three separate analyses to include only species for which we had data  simulations. The Bayesian phylogenetic mixed models were implemented using the MCMCglmm package in R10 for the fixed effects, and a weakly informative inverse-Gamma prior with shape  and scale (beta) parameters of 0.001 for random effects. We ran each analysis for 11 million iterations with a burn-in of 100,000 and thinning interval of 10,000 to minimize autocorrelation in the chains. For each model we ran three independent chains (sensu refs. 52) and used the Gelman–Rubin test to ensure model convergence53. In all cases a scale reduction factor of one indicated that the chains were indistinguishable and had thus converged (Supplementary Tables 2) was calculated according to Hadfield and Nakagawa54 using the following equation: H2 = σ2a /(σ2a + σ2e), where σ2a is the phylogenetic variance and σ2e is the residual variance. A PMCMC value of <0.05 was used to denote significant differences between groups or relationships between variables.For the MCMC simulations we used the default MCMCglmm Gaussian prior with mean = 0 and variance = 10Further information on research design is available in the Supplementary InformationPeer Review FileReporting SummarySource Data


The treatment with 4.25% glucose increased procathepsin B by 3.1-fold and cathepsin B by 5.9-fold in the HPMCs. Cathepsin B induced the secretion of MMP-1, -2, and -3 and TIMP-1 in the HPMCs, but uPA was not excreted. In the PF murine models, cathepsin B reduced the thickness of the submesothelial layer and cystatin C attenuated the effect of cathepsin B. HPMCs secrete cathepsin B with exposure of PD solution, and cathepsin B might help protect against PF.Glucose-containing peritoneal dialysis (PD) solution causes peritoneal fibrosis (PF) characterized by accumulation of extracellular matrix (ECM) in the submesothelial layer. Cathepsin B is a lysosomal cysteine protease that degrades ECM, but its role in the PF remains unclear. Thus, we investigated the role of cathepsin B in PF. Procathepsin B was measured in the 73 PD effluents of 68 patients. Procathepsin B and cathepsin B after exposure of glucose and the effects of cathepsin B on the expression of matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases (TIMPs), and urokinase-type plasminogen activator (uPA) were measured in the supernatant of cultured human peritoneal mesothelial cells (HPMCs). The effect of cathepsin B and its inhibitor, cystatin C, on PF was investigated in the murine model. Procathepsin B was measured at 3.6  Peritoneal dialysis (PD) is one of the potential renal replacement therapies for ESRD, along with hemodialysis and kidney transplantation, and is the main treatment modality in some countries, such as Hong Kong, Colombia, and New Zealand . The totUltrafiltration failure is the main reason for stopping PD and occurs in 36% of PD patients using nonphysiologic PD solutions over 5 years . HypertoPeritoneal fibrosis occurs when extracellular matrix (ECM) synthesis exceeds its degradation. In terms of ECM production, many in vitro studies have revealed that human peritoneal mesothelial cells (HPMCs) excrete matrix proteins including collagens I, II, III, and IV, together with fibronectin, heparan sulfate, and dermatan sulfate proteoglycans, which are enhanced by high glucose stimulation –11. In cCathepsin B is a potent lysosomal cysteine protease that has been extensively studied in the context of malignancies. Its expression is increased in various human cancer cells, and it plays a role in tumor invasion by degrading the ECM directly and via MMP/TIMP and urokinase-type plasminogen activator (uPA) pathways –22. CystWe aimed to investigate the role of cathepsin B in peritoneal fibrosis in PD patients. We measured procathepsin B and cystatin C levels in PD effluent and determined if cultured HPMCs secreted procathepsin B and cathepsin B in response to high glucose conditions. We also examined the effects of cathepsin B on the secretion of MMPs, TIMPs, and uPA in in vitro cultured HPMCs and on peritoneal fibrosis in a chlorhexidine-treated mouse model.We enrolled consenting PD patients who underwent Kt/Vurea measurement and a peritoneal equilibrium test (PET) according to routine management protocols in two PD clinics of university-affiliated hospitals  in Korea. Total Kt/Vurea and modified PET using 4.25% glucose dialysate were measured routinely in the PD clinics within 1 month after starting PD, 6 months later, and then every year. Patients with acute illnesses requiring admission or with acute bacterial infection, including peritonitis, within 1 month were excluded.Twenty-four hours urine, unless the patient was anuric, and 24 hours PD effluent were collected from the patients. Renal and peritoneal Kt/Vurea was calculated using urea clearance data from a 24-hour collection of urine and PD effluent. The urea-distribution volume was calculated using the Watson equation [For PET, patients with an overnight dwell of 1.5% glucose dialysate were subjected to a 4-hour dwell with 4.25% glucose dialysate on the following morning. PD effluent samples were taken at 0- and 4-hour during the test, and blood samples were taken at 2-hour. The PD effluent/plasma ratio for creatinine (D/Pcr) was calculated and corrected for glucose interference using a correction factor derived by each center's laboratory. Cystatin C and procathepsin B were measured in the 2-hour blood samples during PET and the overnight PD effluent. Cystatin C was measured by nephelometry, and procathepsin B was measured by a quantitative sandwich enzyme immunoassay . We also measured CA 125 in the overnight PD effluent by electrochemiluminescence . All protocols were approved by the Institutional Review Board of the Eulji Medical Center and Inje University Ilsan Paik Hospital .g for 10 minutes at 4°C, and the cell pellet was then washed and resuspended in Medium 199  supplemented with 10% fetal bovine serum, L-glutamine 2 mM, penicillin 100 IU/ml, streptomycin 100 μg/ml, hydrocortisone 0.4 μg/ml, insulin 5 μg/ml, and transferrin 5 μg/ml. The cells were then seeded onto culture dishes and grown in the same medium at 37°C in humidified 5% CO2 in air. The culture medium was changed 24 hours after seeding and then every 3 days.Human omentum samples were obtained from consenting patients undergoing elective abdominal surgery, washed with sterile phosphate-buffered saline, and then incubated in 0.05% trypsin with 0.02% ethylenediaminetetraacetic acid solution for 20 minutes at 37°C. The suspension was centrifuged at 100 ×μg/ml. The concentration of procathepsin B and cathepsin B in the supernatant of HPMCs was measured by the sandwich enzyme immunoassay for procathepsin B and cathepsin B  6 hours later.We investigated the effect of glucose on procathepsin B and cathepsin B secretion by HPMCs after incubating the cells in serum-free medium to arrest and synchronize cell growth. The cells were treated with M199 as a control (glucose 5.6 mmol/L), with M199 containing 1.5% glucose (addition of glucose 77.7 mmol/L), 4.25% glucose (addition of glucose 230.5 mmol/L), and their osmotic controls  or lipopolysaccharide  5 We treated HPMCs with 1 and 5 ng/ml human cathepsin B (Sigma-Aldrich), respectively, and determined their effects on the secretion of MMPs, TIMPs, and uPA 12 hours later. The protein expression of MMP-1, MMP-2, MMP-3, TIMP-1, TIMP-2, and uPA in the supernatant was determined using enzyme-linked immunosorbent assay (ELISA) kits . All protocols were approved by the Institutional Review Board of the Eulji Medical Center .μg/ml mouse cathepsin B (R&D Systems) 0.3 ml (group 3), or 0.5 μg/ml cathepsin B 0.15 ml plus 5 μg/ml mouse cystatin C  0.15 ml (group 4) for a further 3 days. All mice were sacrificed on day 14.C57BL/6 male mice (age 20 weeks and weight 20–30 g) were purchased from Orient Bio Company . Peritoneal fibrosis was induced using a solution of 0.1% chlorhexidine gluconate and 15% ethanol dissolved in saline. A total of 40 mice were divided into four groups (10 for each group). Ten mice were treated with daily intraperitoneal injections of 0.3 ml normal saline for 6 days (group 1). The other 30 mice were treated with daily intraperitoneal injections of 0.3 ml chlorhexidine solution for 3 days and were then divided into three groups and treated with normal saline 0.3 ml (group 2), 0.5 After careful macroscopic inspection, the anterior walls were harvested and 5 mm tissue sections were fixed in 10% formalin and then embedded in paraffin. The sections were stained with hematoxylin and eosin and Masson's trichrome stains and examined in a blinded manner. The thickness of the submesothelial layer, defined as the area from the abdominal muscular surface to the peritoneal mesothelium, was measured at five random locations in each section. The mean submesothelial thickness was defined as the index for interstitial fibrosis. All procedures were carried under standard conditions in the Laboratory Animal Unit of Eulji University, and all experiments conformed to the Eulji University Institutional Animal Care and Use Committee .p < 0.05 was considered statistically significant.The normality of the data distributions was tested by Kolmogorov–Smirnov tests. Skewed variables were log transformed or analyzed by nonparametric tests. Values with a normal distribution were expressed as mean ± standard deviation (SD), and non-normally distributed values were shown as medians and interquartile ranges (IQR). Correlations between two continuous variables were analyzed by Spearman's correlation to investigate the factors associated with PD effluent procathepsin B and cystatin C. All statistical analyses were performed using SPSS 17.0 . μg/L, and the median PD effluent level was 5.4 μg/L. The mean cystatin C serum level was 4.4 mg/L, and the median PD effluent level was 0.6 mg/L. Cystatin C concentration was about 1000 times higher than procathepsin B concentration in serum and 100 times in the dialysate effluent. Cystatin C levels in serum were higher than in the dialysate effluent, while levels of procathepsin B showed the opposite pattern . But, procathepsin B and cystatin C levels were positively correlated with CA 125 levels in PD effluent . D/Pcr was also correlated with procathepsin B  and cystatin C  in PD effluent  (p=0.01) and 2.4-fold (p=0.01), respectively. Procathepsin B level after stimulation with 4.25% glucose was higher than that of its osmotic control, but, statistically insignificant (p=0.09).Stimulation with 1.5% glucose and its osmotic control had no effect on procathepsin B secretion by HPMCs  . Howeverp=0.01 and 2.7-fold; p=0.01, respectively) but, not by 1.5% glucose stimulation . 1.5% osmotic control increased the level of cathepsin B, but, statistically not significant  (p=0.03). LPS also induced procathepsin B and cathepsin B secretion by HPMCs .Cathepsin B in the supernatant of HPMCs was induced by 4.25% glucose and its osmotic control  . 4.25% gCathepsin B treatment induced the secretion of MMP-1, MMP-2, MMP-3, and TIMP-1 by HPMCs . Proteinμm thick in the control group (group 1) compared with 333 ± 59 μm in the chlorhexidine-treated group (group 2). Treatment of the fibrosis model mice with cathepsin B reduced the thickness of the submesothelial layer by 192 ± 25 μm (group 3), while the simultaneous addition of cathepsin B and cystatin C had no significant effect .Chlorhexidine treatment induced substantial peritoneal fibrosis after 14 days, as determined by microscopic examination . The subThis study provides the first evidence for cathepsin B secretion by HPMCs and for increased cathepsin B secretion following high glucose stimulation. Cathepsin B is a lysosomal cysteine protease, and its main function is the degradation of proteins that have entered the lysosomal system from outside the cell or from other compartments within the cell. The roles for cathepsin B in pathology may often be related to inappropriate location of the enzyme. Thus, the enzyme can be secreted as a proform procathepsin B and activated extracellularly .The results of our clinical study showed that procathepsin B levels were lower than cystatin C levels in the serum and dialysate effluent from PD patients. However, procathepsin B levels in PD effluent were higher than in serum and were correlated with CA 125, which is a known marker of peritoneal cell mass . These rEvidence for the effect of cathepsin B on peritoneal fibrosis is currently lacking. However, its role in ECM degradation suggests that it may have a protective function in peritoneal fibrosis. Cathepsin B was shown to promote the metastasis of cancer cells by degradation of the surrounding ECM, either directly or via activation of uPA, MMPs, and via inactivation of TIMPs –22. In cβ and ECM by HPMCs [The mechanism whereby cathepsin B influences HPMCs is not clear. HPMCs can synthesize MMP-1, -2, -3, -8, and -9, along with TIMP-1 and -2. High glucose stimulation decreased MMP-1 and MMP-8 secretion and increased TIMP-1 and TIMP-2 in HPMCs , 13. MMPby HPMCs –34. The Our clinical study has limitations due to the small sample size and the cross-sectional nature which lacks longitudinal data. In the HPMCs experiment, we only measured the protein expression of MMPs, TIMPs, and uPA with cathepsin B stimulation. The effect of the addition of cystatin C should be evaluated. And, the expression of MMPs, TIMPs, and uPA should be confirmed in the mouse model. We also used the murine model that prevents generalization of the results to humans. Further studies are needed to study the role of cathepsin B in peritoneal fibrosis in PD patients.The results of our in vivo study showing that cathepsin B decreased the thickness of the submesothelial layer suggest that cathepsin B, which is secreted by HPMCs after high glucose stimulation, might reduce peritoneal fibrosis in PD patients. Cathepsin B also increased the secretion of MMPs and TIMP-1, but not uPA, indicating that its effects in the peritoneum might be meditated by MMP pathways. Further studies are needed to confirm the effect of cathepsin B on the peritoneum and to explore the possibility of cathepsin B as a therapeutic target in PD patients with peritoneal fibrosis.


Sensorineural hearing loss is mainly acquired and affects an estimated 1.3 billion humans worldwide. It is related to aging, noise, infection, ototoxic drugs, and genetic defects. It is essential to identify reversible and preventable causes to be able to reduce the burden of this disease. Inflammation is involved in most causes and leads to tissue injury through vasospasm-associated ischemia. Vasospasm is reversible. This review summarized evidence linking inflammation-induced vasospasm to several forms of acquired sensorineural hearing loss. The link between vasospasm and sensorineural hearing loss is directly evident in subarachnoid haemorrhage, which involves the release of vasoconstriction-inducing cytokines like interleukin-1, endothelin-1, and tumour necrosis factor. These proinflammatory cytokines can also be released in response to infection, autoimmune disease, and acute or chronically increased inflammation in the ageing organism as in presbyacusis or in noise-induced cochlear injury. Evidence of vasospasm and hearing loss has also been discovered in bacterial meningitis and brain injury. Resolution of inflammation-induced vasospasm has been associated with improvement of hearing in autoimmune diseases involving overproduction of interleukin-1 from inflammasomes. There is mainly indirect evidence for vasospasm-associated sensorineural hearing loss in most forms of systemic or injury- or infection-induced local vascular inflammation. This opens up avenues in prevention and treatment of vascular and systemic inflammation as well as vasospasm itself as a way to prevent and treat most forms of acquired sensorineural hearing loss. Future research needs to investigate interventions antagonising vasospasm and vasospasm-inducing proinflammatory cytokines and their production in randomised controlled trials of prevention and treatment of acquired sensorineural hearing loss. Prime candidates for interventions are hereby inflammasome inhibitors and vasospasm-reducing drugs like nitric oxide donors, rho-kinase inhibitors, and magnesium which have the potential to reduce sensorineural hearing loss in meningitis, exposure to noise, brain injury, arteriosclerosis, and advanced age-related and autoimmune disease-related inflammation. Vasospasm is a consistent feature of all forms of cerebral inflammation including forms caused by infections like bacterial meningitis, cerebral malaria, and sterile vascular inflammation as detectable in diabetic ketoacidosis and brain injury , 2. VasoReports providing evidence relating to conditions associated with inflammation and SNHL and/or a focus on a potential association between inflammation-induced vasospasm and SNHL. As indicator of vasospasm was in the interpretation hereby taken that a proportion of people affected by a condition associated with SNHL showed laterality/ and or reversibility of the SNHL.Both animal and human studies.All studies reporting randomised controlled trials of anti-inflammatory or vasospasm-relieving drugs in prevention and/or treatment of SNHL.Studies which reported on the pathophysiology of cytokine-induced hearing loss or vasospasm.Included were the following studies:Studies in which patients with conductive hearing loss were investigated.Studies not reported in English language.Case reports on effect of treatment modalities on SNHL.Nonrandomised studies with regard to treatment trials in humans.Studies on compromise of vascular supply by arterial wall thickening, e.g., in vasculitis and endoluminal stenosis like in subendothelial atherosclerotic proliferation or in obstruction of the vascular lumen by embolism.Excluded were the following studies:Searches using the following keywords were carried out in September 2019: (i) “hearing loss” and “vasospasm” in the PubMed database and (ii) “sensorineural hearing loss” in the Cochrane Library database.References of relevant articles were searched and incorporated where indicated. For flow chart of literature search, see “Direct evidence” for inflammation-associated vasospasm causing SNHL studies where there was evidence of vasospasm on in vivo dynamic imaging like Doppler flow studies in patients with conditions with SNHL more than in patients without the same conditions. Evidence regarding vasoconstrictors and treatment with ant-inflammatory agents and vasodilators was similarly labelled if based on a model with direct evidence.“Features consistent with inflammation-associated vasospasm-induced SNHL” and the associated treatment addressing and/or leading to a change in those features.“Conditions associated with increased risk of inflammation associated with vasospasm-induced SNHL.” All forms of inflammation involving vasoconstriction causing cytokines were regarded as putting the cochlear perfusion at risk of vasospasm-induced compromise.In the descending order of strength of a potential causal association of inflammation-induced vasospasm and SNHL, conditions were categorized into 3 categories:Direct evidence for a vasospasm as etiological factor in acquired SNHL is the analysis of data from children with sudden SNHL where influence of noise exposure, medication and drugs including illicit substances, and exposure to chemicals at the work place which could cause temporary hair cell dysfunction is much less likely. A pooled analysis of 226 cases (ears) of sudden SNHL in children from two centres in China demonstrated 85% of children had unilateral hearing loss, of which the largest proportion was profound (51%). The hearing loss was reversible to a variable extent (including any form of recovery) in 48.6% , 4, and The hearing loss found associated with autoimmune-induced inflammation has features consistent with inflammation-associated vasospasm-induced sensorineural hearing loss. The hearing loss in autoimmune-induced inflammation is potentially reversible, and anti-inflammatory treatment can prevent and treat SNHL .Autoimmune diseases like systemic lupus erythematosus and Crohn's disease which induce overproduction of tumor necrosis factor (TNF) and rarer diseases like the cryopyrin-associated periodic syndromes with inflammasome activation and subsequent overproduction of interleukin-1(IL-1) like CINCA syndrome and Muckle–Wells disease have been associated with SNHL , 9. The In bacterial meningitis, severe inflammation of the meninges is observed which should, if there was a link between inflammation and SNHL lead to SNHL. Hearing loss is indeed observed in all forms of bacterial meningitis , 11.In a prospective study of 236 children with meningitis using brainstem auditory evoked responses, 38 were detected with hearing loss in the acute (early) phase of meningitis; among these, 32 were available for follow-up, and within the latter group, 22 recovered normal hearing, i.e., reversibility was seen in 68.7% of the cases available for documentation. The hearing loss was unilateral in 21 of the 38 children with hearing loss detected in the acute meningitis phase (= 55.3%). The 21 unilateral HL cases among 236 children with bacterial meningitis amounted therefore to 9% .Haemophilus influenzae meningitis . Su. Su10]. ningitis , whereasningitis .A prospective investigation of adults with bacterial meningitis by transcranial Doppler sonography related the degree of arterial narrowing to outcome including focal cerebral ischemic deficits, which were more frequent in patients with cerebral blood flow velocity >210 cm/s compatible with vasospasm .N = 132; very low-quality evidence) but did not have a significant effect on the number of infants with SNHL at two years . In one trial, dexamethasone reduced the likelihood of hearing loss at 4 to 10 weeks after discharge . There was no beneficial effect of corticosteroid therapy in low‐income countries [Other investigations confirmed features of cerebral vasospasm in bacterial meningitis. Patients with features of vasospasm had significantly increased concentrations of IL-1 and IL-6 in the CSF. Underlying mechanisms have been explored in a rat model, where cerebral blood flow as measured by injection and recovery of microspheres from the brain tissue was found to be reduced in pneumococcal meningitis. The cerebral blood flow could be restored by the endothelin-1 antagonist bosentan with a reduction in cortical cerebral injury. Strong evidence of a protective role of the vasodilator nitric oxide against vasospasm in bacterial meningitis was derived from an animal model of neonatal meningitis where inhibition of NO synthase worsened outcome in some models of bacterial meningitis, leading to local cerebral ischemia , 19. Theountries –22.All these lines of evidence revealed features consistent with inflammation-associated vasospasm-induced SNHL but no direct evidence for a link between the hearing loss observed and vasospasm of blood supply of the cochlea.A recent systematic review of 13 studies encompassing 773 patients found that the studies with the highest level of evidence reported a transient or chronic hearing loss of at least 10–15 dB across a range of frequencies in as many as 58% of patients with traumatic brain injury without bone fracture .Vasospasm has hereby previously been associated with brain injury and was more severe in patients with associated features of a systemic inflammatory response .In subarachnoid haemorrhage, vasospasm has been directly linked to hearing loss , 24. TheA retrospective case control study of neonatal brain injury including 58 infants with SNHL and comparing them with 116 controls without hearing loss established that cerebral infarction was significantly increased in infants with SNHL compared to normal hearing controls . Cerebraα inhibition using etanercept prevented noise-induced hearing loss by improvement of cochlear blood flow in vivo [The labyrinthine artery is known to constrict during and after noise overstimulation . TNF-α i in vivo , 29. Pro in vivo . For noiAge-related inflammatory diseases like type II diabetes and cardiovascular disease have been associated with SNHL , 32. In The theoretic possibility of vasospasm related to arteriosclerotic inflammation is raised by the transient audiovestibular dysfunction with transient hearing loss found as prodromal symptom of stroke affecting the supply area of the anterior inferior cerebellar artery in vertebrobasilar ischemic stroke affecting 8 to 31% of prospectively observed patients including patients with normal diffusion-weighted MRI after the attack . Brown eOverall, the findings in presbyacusis justify the conjecture of an increased risk of inflammation-associated vasospasm-induced sensorineural hearing loss as a contributory underlying mechanism.The pain of migraine-associated headaches has been linked to the activation of nociceptors by the vasoconstriction-inducing cytokines TNF and IL-1 , 39. TheInflammatory mediator action could explain the role of vasospasm in the pathogenesis of SNHL in all the aforementioned conditions. For many years, the cochlea was considered an “immune-privileged” organ because of the presence of a tight junction-based blood-labyrinth barrier. A number of more recent studies, however, showed that resident macrophages are always present in the cochlear lateral wall as well as in the spiral limbus and the scala tympani side of the basilar membrane, and they are activated by various types of insults, including noise exposure, ischemia, mitochondrial damage, and surgical stress leading to cytokine release including tumour necrosis factor .TNF-alpha was shown to be effective in decreasing cochlear blood flow at a dose of 5.0 ng/mL. Lower concentrations or placebo treatment did not lead to significant changes. After pretreatment with etanercept, a recombinant human TNF receptor p75 Fc fusion protein, which blocks TNF action, TNF-alpha at a dose of 5.0 ng/mL, no longer led to a change in cochlear blood flow .In a prospective clinical trial in Mongolian gerbils, tumor necrosis factor-alpha administered via continuous 8-day intrathecal flow induced SNHL across all frequencies compared to phosphate-buffered saline delivered intrathecally in controls and tumor necrosis factor-alpha antibody injected intraperitoneally reduced SNHL in the pneumococcal meningitis model .In a prospective observational study, tumor necrosis factor-alpha levels in peripheral venous blood were compared between patients with autoimmune inner ear disease and sudden SNHL compared to controls and steroid responders compared with steroid nonresponders. TNF levels were significantly higher in patients with sudden SNHL, and a high baseline plasma TNF of greater than 18.8 pg/ml had a positive predictive value higher than 97% for a sudden change in hearing threshold  and was The mechanism by which tumor necrosis factor causes a reduction in cochlear blood flow has been identified and involved contraction of cochlear pericytes which has in the guinea pig model been found to cause a reduction of capillary diameter by 3.6 ± 4.3%, which was reversible by anti-TNF therapy with ethanercept .The effect of TNF on vasoconstriction may be mediated by sphingosine-1-phosphate (S1P) .2+ sensitization of the contractile filaments, which frequently involves a rho-kinase, is also an effect of S1P and has been observed in human coronary smooth muscle cells. Inhibition of the rho A/rho-kinase pathway has hereby been shown to inhibit vasoconstriction [S1P has been demonstrated to lead to vasoconstriction in cerebral and basilar arteries in vivo in animal models. This effect was shown to be mediated by elevation of intracellular calcium levels by mobilisation from intracellular stores in smooth muscle cells. Catriction . It has triction . It has triction .β-actin. Biopolymer- ; SIBS) eluted DXMb retains its ability to prevent the death of explant auditory hair cells that were exposed to TNFa and to initiate the same patterns of upregulation and downregulation of antiapoptosis- and proapoptosis-related genes  that were observed in TNFa-challenged and TNFa-challenged, DXM-treated organ of Corti explants [The question is whether the chronic inflammation leading up to presbyacusis leads to SNHL via cytokine-induced apoptosis of hair cells of the inner ear or recurrent vasospasm in the labyrinthine artery. In addition to causing vasospasm, TNF could trigger programmed cell death (apoptosis) in hair cells of the inner ear and thus cause SNHL. The extrinsic pathway to apoptosis includes TNF alpha, which via TNF receptor-associated death domain activates cysteine-aspartic proteases (caspases)-8 and -10. Caspase-8 then can activate tBid to recruit the help of the intrinsic pathway and can activate caspases-3, -6, and -7. These caspases lead to the execution phase of cell death induction through their protein-cutting activity. Caspase-3 can hereby cause DNA and chromatin damage, rearrange the cytoskeleton, and disrupt intracellular transport . Apoptosexplants .Activation of phospholipase C-generated phosphatidylinositol trisphosphate causes calcium release which leads to myosin light chain kinase activation leading to myosin light chain activation and calcium-dependent vasospasm. Phosphorylation of myosin light chain (MLC) by MLC kinase is one of the most important steps for vascular smooth muscle contraction.Activation of protein kinase C (PKC) through phospholipase C-generated diacylglycerol  bisphosphate) can act through phosphorylation, hence activating the myosin light chain kinase. Prolonged contraction in cerebral vasospasm for up to two weeks can be mediated by this mechanism.PKC activation regulates MLC phosphorylation through activation of rho-kinase and the myosin-binding subunit (MBS) of MLC phosphatase (MLCPh).An investigation in patients with SAH showed that levels of IL-1 beta but not TNF-alpha were increased and correlated with the later development of vasospasm. IL-1 acts through G-protein-coupled receptors in three ways which cause contraction of vascular smooth muscle [2+ concentration, but rather mediating Ca2+ sensitization, is the rho A/rho-kinase pathway. In cultured human coronary vascular smooth muscle cells, inflammatory stimuli, such as IL-1 beta, increase rho-kinase expression (at both mRNA and protein levels) and function [A secondary pathway for vascular smooth muscle contraction that is not directly dependent on Cafunction .RhoA mRNA were upregulated in the spastic site than the control coronary site. Rho A/rho-kinase-mediated MLCP inhibition occurs mainly by phosphorylation and inhibition of MYPT-1, the regulatory subunit of MLCP, or by CPI-17-mediated inhibition of the catalytic subunit of MLCP. Rho-kinase hereby phosphorylates MBS, which results in the inhibition of MLCPh [2+ sensitization [Both endothelial NO production and NO-mediated signaling in vascular smooth muscle cells (VSMC) are targets and effectors of the rho A/rho-kinase pathway. In endothelial cells (ECs), the rho A/rho-kinase pathway negatively regulates NO production . In addiof MLCPh . These rtization .Endothelin-1 is one way of action of both TNF and IL-1 on vasospasm-induced hearing loss. Only ET-1 is produced in cerebral endothelium and mediates cerebral vasoconstriction via endothelin-A (ETA) receptors. ETA is localized in vascular smooth muscle cells, and stimulation leads to increase in intracellular calcium concentrations leading to vasoconstriction. ET-1 expression is enhanced by IL-1 and TNF and can be inhibited by NO, nitric oxide donor drugs, and dilator prostanoids via an increase in cellular cGMP. NO can produce relaxation of some blood vessels from some species via activation of potassium channels [Should cytokines have a role in SNHL one would expect that cytokine gene polymorphisms which are associated with differences in cytokine production differ between patients prone to hearing loss and those who are not. This is in fact the case.β − 511 T allele and the IL-1β + 3953 T allele was observed between sudden SNHL and controls. This suggests that the IL-1β − 511 and +3953 loci may play an important role in the etiopathogenesis of SSNHL [A significant difference in carriage of both the IL-1of SSNHL .Genetic linkage studies have investigated the association of polymorphisms of the TNF-alpha and TNF-beta genes with sudden SNHL comparing 97 SSNHL patients and 587 controls and found that the TNF-beta +252 A− ⟶ G polymorphism which is associated with increase in production of this cytokine was significantly increased in patients with SSNHL , a locus(1) Calcium-Channel Blockers. As illustrated in anti-phospholipid antibody syndrome, an autoimmune inflammatory syndrome, which is associated with cerebral vasoconstriction syndrome, centrally acting calcium antagonists like nimedipine, can reduce symptoms of cerebral vasoconstriction, which include hearing loss [ing loss .2+ channels protected against NIHL in mice and in guinea pigs, and blockade of T-type voltage-gated Ca2+ channels was effective in mice. Also consistent with a contribution of calcium-mediated events in hair cell damage, application of the calcineurin inhibitor FK506 attenuated NIHL in guinea pigs [Blockade of L-type voltage-gated Canea pigs –66.(2) Magnesium. An agent that can lead to vasodilatation by virtue of antagonism of calcium-dependent vascular smooth muscle contraction is magnesium. It seems to act through a variety of pathways. Experiments in laboratory animals demonstrated that as magnesium decreases, there is a greater secretion of catecholamines and prostaglandins, subsequently leading to a reduction of the blood flow because of vasoconstriction in the inner ear and with it, a higher risk of energetic depletion in the hair cells. Increased magnesium intake can thereby improve inner ear microcirculation. The muscle tone of the vessels diminishes with higher concentrations of intracellular free magnesium, and their reactivity to vasoactive substances decreases [ecreases –69.In addition to the well-characterized effects on vasodilation, biochemical effects of magnesium include modulation of calcium channel permeability, influx of calcium into cochlear hair cells, and glutamate release , 71.The first evidence for the importance of magnesium in prevention of SNHL was gained in observational studies of magnesium deficiency in rats and guinea pigs exposed to noise. Magnesium deficiency increased susceptibility to NIHL in rats  and guinThe results of magnesium in animal experiments have have been confirmed in 3 randomised controlled trials –79 summa(1) Etanercept. Etanercept is a widely used biological agent in the treatment of autoimmune diseases such as rheumatoid arthritis, psoriasis, and others by targeting TNF-α. This and other anticytokine therapies, which show promise in prevention or treatment of inflammation-induced SNHL, have been reviewed previously [α inhibitor etanercept has hereby been shown to reduce noise-induced threshold shifts [n = 17 in total) means that a clinically significant difference may have been missed [eviously , and thed shifts . A very n missed .(2) Steroids. The anti-inflammatory and proresolution glucocorticoid dexamethasone (DEXA), which is able to reduce TNF production, has been investigated after systemic, intratympanic, and combined delivery in sudden and noise-induced SNHL but with mixed results as shown in the following four meta analyses [analyses –86 (Tabl(3) Statins. Statins are inhibitors of the 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, which is a key enzyme of the mevalonate pathway, the metabolic pathway that produces cholesterol and other isoprenoids. It also has a direct effect on rho-kinase activity and hence the predisposition to vasospasm. This effect is mediated through several different mechanisms: because statins inhibit an early step in the cholesterol biosynthetic pathway, they also inhibit the synthesis of isoprenoids such as farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP), which are important posttranslational lipid attachments for intracellular signaling molecules such as the rho GTPases. Treatment with statins prevents endothelial nitric oxide synthase (eNOS) downregulation by prolonging the half-life of eNOS mRNA. The prolongation of half-life of eNOS mRNA by statins is reversed by GGPP, but not FPP, suggesting the involvement of small GTPases such as rho GTPase in this process. Indeed, decrease in rho GTPase responses as a consequence of statin treatment increases the production and bioavailability of endothelium-derived NO. The mechanism involves, in part, rho/rho-kinase- (ROCK-) mediated changes in the actin cytoskeleton, which leads to decreases in eNOS mRNA stability. In addition to increase in eNOS expression by statins, statins can also rapidly induce the phosphorylation and activation of eNOS via the phosphatidylinositol-3 kinase (PI3K)/protein kinase Akt pathway [α and interferon-γ expression [ pathway . Inhibit pathway . It has pression . In ratspression . The sampression  and morepression . In a prpression .n = 274), a 48% reduced odds of prevalent hearing loss was observed after multivariable adjustment (OR = 0.52 (95% CI = 0.29–0.93)) [This result confirmed a previous study: The Blue Mountains Hearing Study is a population-based survey of age-related hearing loss which aimed to assess associations between dietary intake of fats (saturated and monounsaturated fats and cholesterol) and certain food groups  with the prevalence, incidence, and progression of age-related hearing loss. It also investigated the link between serum lipids and cholesterol-lowering medication (statins) and hearing loss. Among persons self-reporting statin use (9–0.93)) .On the other hand, a population-based study in Taiwan showed a slight but significant association of previous statin use and SNHL ) [The only randomised double-blind clinical trial in this area was geared to investigate the impact of statins on presbyacusis. It was very small with a total of 50 patients. Pure-tone audiometry and tinnitus evaluation at enrolment and after 7 and 13 months of atorvastatin did not show any impact on hearing thresholds or tinnitus .(4) Oral Curcumin. Curcumin, a compound isolated from the plant Curcuma longa, is the principal curcuminoid of turmeric, a member of the ginger family. It has been shown to reduce vascular inflammation and the related vasospasm in cerebral blood vessels in animal models of subarachnoid haemorrhage [morrhage , 98.It is therefore not surprising that oral curcumin in a highly bioavailable preparation has been shown to reduce noise-induced SNHL in a murine model in a dose-dependent fashion .One mechanism may be its capacity for reduction of TNF expression  which is(5) Phosphodiesterase-5 Inhibitors. Phosphodiesterase-5 inhibitors are potent vasodilators and can relieve vasospasm. It is therefore conceivable that they could reduce or prevent inflammatory vasospasm-related hearing loss. The mechanism of action involves causing increased bioavailability of cGMP, a potent endogenous vasodilator: When nitric oxide (NO) forms in the body, it avidly binds to the heme moiety of the enzyme guanylyl cyclase, which is found in vascular smooth muscle cells. NO is formed by vascular endothelium and diffuses into the vascular smooth muscle cells adjacent to the endothelium where it binds to and activates guanylyl cyclase. This enzyme catalyzes the dephosphorylation of GTP to cGMP, which serves as a second messenger particularly for signaling smooth muscle relaxation. Cyclic GMP induces smooth muscle relaxation by multiple mechanisms includingIncreasing intracellular cGMP, which inhibits calcium entry into the cell, and decreasing intracellular calcium concentrations+ channels, which leads to hyperpolarization and relaxationActivating KStimulating a cGMP-dependent protein kinase that activates myosin light chain phosphatase, the enzyme that dephosphorylates myosin light chains, which leads to smooth muscle relaxationBecause of the central role of cGMP in NO-mediated vasodilation, drugs that inhibit the breakdown of cGMP (cGMP-dependent phosphodiesterase inhibitors) are used to enhance NO-mediated vasodilation.Experiments in the mouse model of noise-induced SNHL demonstrated that Pde5 inhibition protected against NIHL . Pde5 inThere have been concerns about an association of phosphodiesterase-5 inhibitor use and SNHL but this can be attributed to a confounding association of erectile dysfunction and hearing loss. Erectile dysfunction is the most common indication for phosphodiesterase-5 inhibition. Erectile dysfunction is liked to SNHL because both can be due to vascular dysfunction or vasospasm in the supplying artery in arteriosclerosis –107.Inflammation is a normal adaptive response aimed at restoring tissue functionality and homeostasis after infection and tissue injury, and suppressing it could have unintended negative consequences. Previous authors recognized the potentially important role of inflammation in causing age, noise, and drug-induced acquired SNHL but merely proposed to reduce the inflammatory response as a strategy to reduce SNHL . This apThe evidence for a link between inflammation-induced vasospasm and acquired SNHL revealed in this review can be categorized as indicating a risk, as showing features or directness for the conditions identified above see :In conditions like bacterial meningitis, there is some hearing loss and there is some indirect evidence that there is vasospasm in bacterial meningitis. Further research needs to link vasospasm with hearing loss in prospective observational studies focussing on cochlear blood supply.Similarly in traumatic brain injury, there is hearing loss in brain injury and there is vasospasm in brain injury, but the association between brain injury and vasospasm-mediated SNHL is only inferred from these two separate sets of findings, without being actually proven in any study.Inhibition of rho-associated kinases by agents like fasudil needs to be explored in all patients at risk of vasospasm associated hearing loss or with established acquired SNHL , 109.Ginkgo biloba-derived quercetin, rosmarinic acid, and curcumin, the application of which has been shown to dilate cochlear vasculature and improve cochlear blood flow as measured by Doppler flowmetry in the guinea pig ex vivo model [Future studies need to explore substances known to increase cochlear blood flow in ex vivo experiments, and these include herbal drugs used by traditional herbal medicine to treat hearing loss like vo model , 111.Tinnitus has been associated with vasospasm in subarachnoid haemorrhage  and migrVascular inflammation may not just be reduced in the labyrinthine artery by the modes of treatment explored in this review but other vascular beds as well, and future randomised controlled trials should incorporate other vestibular disorders including vertigo and tinnitus and vascular headaches as secondary outcomes as well as heart disease, stroke, vascular dementia, peripheral vascular disease, and their incidence could be monitored during long term follow-up of patients enrolled.There is mainly indirect evidence for vasospasm-associated SNHL in most forms of systemic or injury- or infection-induced local vascular inflammation. This opens up avenues in prevention and treatment of vascular and systemic inflammation as well as vasospasm itself as a way to prevent and treat most forms of acquired SNHL. Future research needs to investigate interventions antagonising vasospasm and vasospasm-inducing proinflammatory cytokines and their production in randomised controlled trials of prevention and treatment of acquired SNHL. Prime candidates for interventions are hereby inflammasome inhibitors and vasospasm-reducing drugs like nitric oxide donors, rho-kinase inhibitors and magnesium which have the potential to reduce SNHL in meningitis, exposure to noise, brain injury, arteriosclerosis, and advanced age-related and autoimmune disease-related inflammation.


Noise-induced hearing loss (NIHL) is the most common preventable cause of deafness. The degree of NIHL is determined by intensity, duration of exposure, spectral characteristics of the noise, and individual susceptibility. Industrial workers in both developed and developing countries are all at risk of suffering from NIHL.An industry-based descriptive cross-sectional study was conducted. Data was collected using structured questionnaires, where sound intensity and hearing assessment were measured using a portable sound level meter and a portable audiometer, respectively. Data was analyzed using Statistical Package for Social Sciences (SPSS) program version 21.Out of 265 industrial workers who were recruited in this study, 161 (60.8%) were males and the predominant age group was 22 to 35 years (43%). The prevalence of NIHL was found to be 58.5%. Of 155 workers with NIHL, 101 (67.7%) were males. The most common age group was greater than 49 years. Of those with work experience from 5 to 10 years, only 38.5% had NIHL. The most common symptom was hearing loss, accounting for 24.9% of cases.The overall prevalence of NIHL was higher in textile industry workers. The prevalence was higher in males, older workers, and those who experienced prolonged exposure. Noise-induced hearing loss is a sensorineural hearing deficit that begins at the higher frequencies  and develops gradually as a result of chronic exposure to excessive sound levels .Although the loss is typically symmetric, noise from such sources as firearms or sirens may produce an asymmetric loss. Hearing loss caused by exposure to recreational and occupational noise results in devastating disability that is virtually 100 percent preventable .Noise-induced hearing loss is the second most common form of sensorineural hearing deficit after presbycusis (age-related hearing loss). Shearing forces caused by any sound have an impact on the stereocilia of the hair cells of the basilar membrane of the cochlea; when excessive, these forces can cause cell death .Worldwide, the burden attributed to occupational noise ranges from 7% in western countries to 21% in developing countries (average 16%) . PrevaleA study done in America in a construction company reported 60% of operating engineers had NIHL, and a higher rate was observed among workers who reported longer years of working. Thirty-eight percent (38%) reported tinnitus, and 62% reported difficulty understanding what people said when speaking loudly .Studies from other parts of the world, such as Sweden, depicted a NIHL prevalence of 22%, and a study from South Africa found approximately 73.2% of miners in the industry to be exposed to noise levels above the legislated occupational exposure limit of 85 dBA .A study done in Dar es Salaam revealed the minimum peak noise level was 87 dBA, and the maximum was 116.5 dBA, with an average of 92.6 dBA. Of those investigated fully, 50.8% and 46.5% in area A and B, respectively, were found to have audiogram patterns typical of NIHL. The study revealed 22.5% and 18.6% of employees had permanent threshold shifts (PTS) in area A and B, respectively, while 28.2% and 27.9% had temporary threshold shifts (TTS) in area A and B, respectively. The study showed significant NIHL in the studied population [Despite the existing evidence of NIHL in industrial workers, data on NIHL in Southern and East Africa remains scarce. The aim of this study was thus to determine the magnitude of NIHL among textile industry workers in Dar es Salaam, Tanzania, creating a basis for limited data in Sub-Saharan Africa.This was an industry-based descriptive cross-sectional study conducted from May to December 2014, and it included all workers 60 years old or younger and meeting the inclusion criteria.Convenience sampling technique was utilized with selection based on the most available sample. Workers who met the inclusion criteria were chosen provided they were available during data collection, and they were added until the desired sample size was achieved.Workers in the production department who were 60 years old or younger, those who had a normal hearing assessment status at the time of employment, those who were in a noise-free zone for 16 hours or more, and those with at least five years of exposure to noise were set as the inclusion criteria.Workers with ear infections and those with other obvious causes of hearing loss apart from excessive noise  were excluded from participating in the study.A total of 265 industrial workers were recruited as the desired sample size.Structured questionnaires were used to collect data from the desired participants. Hearing assessments were performed by qualified audiologists. Hearing assessments were done in a room with the lowest sound intensity as much as possible (at most 35dBA).Data analysis was done using SPSS version 21. Statistical association was computed using cross tabulations, and a Chi-square test was used to compare proportions. P value of <0.05 was considered statistically significant.Workers were provided with information about the study and then asked to provide written consent to participate. They were free to discontinue participation at any point. Ethical approval was provided by the Research and Publication Committee of the Muhimbili University of Health and Allied Sciences (MUHAS).2 = 20.1, p-value < 0.001)  were between the ages of 22 to 35. The mean age was 40.28 (SD = 12.6), the minimum age was 22 years, and the maximum age was 60 years. Male predominance  was found in this study. There were more males than females in all age groups except 36 to 49 years, where there were 52.4% females  with work experience of 5 to 10 years. The lowest number of workers had work experience of 16 to 20 years   enrolled in the study were in the loom shade department. The loom shade department is the noisiest, with a sound intensity over 95 dB. Drawing frame and finishing were the only departments with a safe sound intensity of 77 to 85 dB. All workers reported working more than 8 hours per day, and none reported using hearing protective devices  with NIHL in the textile industry Figure .2 = 29.3, p-value < 0.001), and the most affected age group was more than 49 years old . By sex, 101 (62.7%) males were affected compared to 54 (51.9%) females, but this was not statistically significant  . Those who worked for more than 35 years (88%) had NIHL, compared to those who worked for 5 to 10 years (38.5%)  had hearing loss in both ears, notch presence was present in 90 (58.1%) workers, 40 (44.4%) had the notch in both ears, and the most common frequency demonstrating the notch present was 4000Hz for 43 (47.7%) workers (Table Hearing loss was reported in 66 24.9%) workers, tinnitus in 62 (23%) workers, and imbalance in 23 (8.7%) workers  could cause hearing loss by synergism.The study revealed the prevalence of NIHL based on sex to be 62.5% in males. Such male predominance appears to correlate with findings from other studies [This study revealed the prevalence of NIHL was increasing as the duration of exposure to excessive noise increased. The prevalence of NIHL based on work experience was 38.5% in those with 5 to 10 years of work experience, 55.6% in those with 11 to 15 years of work experience, 66.7% in those with 16 to 20 years of work experience, 62.9% in those with 21 to 25 years of work experiene, 71.4% in those with 26 to 30 years of work experience, 73.9% in those with 31 to 35 years of work experience, and 88% in those with more than 35 years of work experience. The pattern is similar to a study done in the United States that found the prevalence of NIHL was 75% for workers with 20 to 29 years, 89% for workers with 30 to 39 years, and 100% for workers with over 40 years in construction [This study revealed the common symptoms reported to be hearing loss (24.9%), tinnitus (23%), and imbalance (8.7%). This pattern is similar to the study done in the United States in which operating engineers reported hearing loss (62%) and tinnitus (38%) . In the In a study done in musicians, the most common symptom was tinnitus, followed by hearing loss (90% of musicians reported tinnitus), and a majority presented with hyperacusis . HyperacThe overall prevalence of NIHL was higher in textile industry workers. This calls for the need to provide protective gear to workers in stations generating excessive noise. Moreover, the prevalence was higher in males, older workers, and those experiencing prolonged exposure.


Orbital varix (or varicose) is an exceptional pathology with poor clinical sign. The blepharospasm can be a revealing cause. The long-term risk is optic atrophy and blindness. Magnetic resonance imaging is the best diagnostic tools. The rise of lesion dimensions by Valsalva maneuvers and prone position is characteristic. We report the observation of a 42-year-old young man, consulting for a blepharospasm of the left eye evolving for two years. Imaging investigations made the diagnosis of orbital varicose. The orbital varix are dilations and proliferations of intraorbital venules . They caA 42-year-old young man, a plumber, without notable pathological antecedents, consulting for a blepharospasm of the left eye evolving for two years. The patient had no clinically significant ocular history. There is no notion of trauma or accidental introduction of intraocular foreign body. The neurological examination was normal. There is a blepharospasm without proptosis. The patient's visual acuity was 20/20 in the two eye. Visual fields were intact, pupillary responses were equal and indirect fundoscopy was normal. All biochemical and hematological indices were normal. The cerebral MRI was unremarkable. The axial fine sections passing through the orbits show a left retro-orbital process in T1 low signal and T2 hyper signal , weakly The orbital varicose is rare. They are a dilation of venules developing most of the time from the ophthalmic vein , 2. TheyDoppler Ultrasonography confirms the vascular nature of the lesion , 4. It cOrbital varicose veins are exceptional. Blepharospasm may be an evocative symptom. Radiological examinations, mainly MRI, are essential to showing the vascular nature of the orbital lesion. Prone maneuver, which increases the size of the varicose, can establish the positive diagnosis.The authors declare no competing interests.