Background and Introduction: Vestibular schwannomas (VSs) are the most common tumors of the cerebellopontine angle, typically presenting unilaterally with ipsilateral sensorineural hearing loss (SNHL). The mechanism of tumor-induced hearing loss has recently been shown to be related to secreted tumor factors, in addition to mechanical compression of the adjacent auditory nerve, and these factors may percolate through CSF or blood to affect contralateral hearing as well.Methods: This is a retrospective study of medical records for patients treated for VS at Mass Eye and Ear from January 1994 through October 2018. Included patients had unilateral VS and sequential audiometry allowing for longitudinal assessment of hearing over time. Mass Eye and Ear's audiology database was used to select age- and sex-matched case controls, also with sequential audiometry, from the non-VS population. Subgroup analysis was performed by age, sex, baseline hearing, and tumor size at initial diagnosis. Hearing loss progression was performed using Kaplan-Meier analysis to account for variable follow-up times.Results: A total of 661 patients were identified with VS and sequential audiometry. The population was predominantly female vs. male , driven primarily by younger patients with Koos 4 tumors . Patients with normal baseline hearing bilaterally (N = 241) demonstrated no significant difference in hearing loss progression in VS-contralateral vs. control ears. Patients with abnormal baseline VS-ipsilateral hearing (N = 190), however, demonstrated significantly higher likelihood of reaching moderate SNHL in VS-contralateral ears. Subgroup analysis by age, sex, and baseline tumor size did not yield any subgroup-specific trends for hearing loss progression.Discussion and Conclusion: This is the largest study to date tracking long-term bilateral hearing outcomes in patients with VS, and demonstrates that, in patients with abnormal hearing in the VS-ipsilateral ear, there exists a long-term risk of progression to moderate hearing loss in the contralateral ear as well. Combined with the absence of significant changes in word understanding in the affected ears, these findings may provide clues to the nature of tumor-secreted factors involved in VS-associated hearing loss. Female predominance within the VS patient population is confirmed, driven mostly by younger female patients with Koos 4 tumors. Vestibular schwannomas (VSs) are Schwann cell tumors that typically originate from the nerve sheath of a vestibular branch of the eighth cranial nerve within the internal auditory canal (IAC), and in 95% of patients cause sensorineural hearing loss (SNHL) , 2. As tDespite VS being an important cause of human SNHL, the underlying pathophysiological mechanisms causing SNHL in patients with VS tumors are still incompletely understood . Early hSecretions produced by sporadic VS tumors could have the potential to reach the contralateral ear by percolating through cerebrospinal fluid (CSF) or blood. Because the vast majority of VS patients suffer from SNHL in the ipsilateral ear, any potential effect of tumor secretions on contralateral hearing is of high clinical relevance. Until now, no study has been done with a large enough patient population, incorporating sufficiently comprehensive audiometric data, to investigate the possible effect of sporadic VS on hearing in the contralateral ear. This study examines whether in patients with unilateral sporadic VS, the progression of SNHL in the contralateral ear is faster than would be otherwise expected for unrelated age-related hearing loss in the general population.A retrospective chart review was performed of patients diagnosed with VS from January 1994 to October 2018 at Massachusetts Eye and Ear. Institutional Review Board (IRB) approval was obtained from the Human Studies Committee at Massachusetts Eye and Ear and Massachusetts General Hospital (IRB 16-103H).Review of electronic medical and billing records at Mass Eye and Ear identified 1009 patients aged 18 years and older with diagnosis codes consistent with VS: 225.1 (ICD-9) and D33.3 (ICD-10), and who additionally had undergone sequential audiometry at Mass Eye and Ear, in order to permit analysis of longitudinal changes in hearing. Patient charts and imaging were reviewed to confirm absence of bilateral VS or three or more total schwannomas or meningiomas, to avoid inclusion of any patients with NF2 . PatientAfter defining the VS study population, an age- and sex-matched case control population was selected at a 3:1 ratio from the general patient population at Mass Eye and Ear; patients in the case control population were required to have a diagnosis code of SNHL or mixed hearing loss and sequential audiometry performed at Mass Eye and Ear, without any other known otologic disease and with normal hearing at baseline in at least one ear. When >3 case control candidates were available, priority for inclusion was given to patients for whom frequency of audiometric testing most closely matched their assigned VS patient. All case control patients with significant change in hearing for either ear at any time during follow-up  were further reviewed in detail for any history of occult otologic disease, and excluded from the case control group if identified by chart review. Each case control patient had normal hearing in at least one ear, with either one or both ears included for analysis depending on baseline hearing status.Kaplan-Meier analysis was performed to evaluate survival with endpoint defined by set audiometric criteria; ipsilateral ears were censored if undergoing either surgery or radiation therapy. Log rank test was applied to evaluate significance in rate of endpoint achievement between VS-ipsilateral ears and VS-contralateral ears, and between VS-contralateral ears and case control group ears. All analyses were performed in Matlab  and Excel .VS patients were stratified by baseline audiometry; audiologic measurements included speech audiometry [word recognition score (WRS%)] and threshold audiometry (dB HL). Word recognition score was calculated using standardized word list of monosyllables, measured as a percentage of correctly recognized words after listening to a recorded word list in quiet, typically at 70 dB or at the level at which the patient's speech intelligibility curve plateaus. Pure tone average (PTA) threshold was calculated as a three-tone average of bone conduction thresholds across 500 Hz, 1 kHz, and 2 kHz frequencies as the primary threshold-based hearing metric; alternate methods such as including the 4 kHz frequency within a four-tone average, and use of AAO-HNS hearing classification were also employed secondarily to confirm findings and trends. Normal baseline hearing was defined as WRS ≥ 92% and a pure-tone average (PTA) threshold of ≤ 25 dB assessed by bone conduction; additionally, if a patient's initial audiometry was performed in the setting of sudden SNHL, however subsequent audiometry demonstrated return to normal hearing within 90 days, then baseline hearing was considered normal for purposes of baseline hearing assignment. If an ear had normal baseline air thresholds but was not assessed for bone thresholds, then baseline hearing was also assigned as normal.Progression of audiometric changes were assessed both ipsilateral and contralateral to known VS tumors. Progression of hearing loss over time was evaluated using Kaplan-Meier analysis, with change in hearing used to define endpoint. For PTAs, the primary assigned endpoint was defined as moderate hearing loss (PTA > 40 dB), with secondary endpoint of moderately severe hearing loss (PTA > 55 dB) per definition by the American Speech-Language-Hearing Association. For WRS%, the primary endpoint was defined as WRS < 78% , with secondary endpoint defined as word understanding <60%  , 18.Review of tumor sizes at the time of each patient's index audiometry was performed via interpretation of primary imaging or review of imaging reports, depending on availability within the medical record. In cases where neither primary imaging nor reports were available, patients were included for analysis as part of the entire population, but not for analysis stratified by tumor size. Given that VS tumors typically grow slowly, at an average of 1–2 mm/year, and given that changes <1 mm are within the margin of error for historically available imaging resolution, imaging was considered representative of baseline tumor size if completed within 12 months of the patient's first available audiogram , 20.Tumor extent was assessed according to the Koos grading system. Tumors were divided into various classes, described as Koos 1 , Koos 2 , Koos 3 (touching the brainstem without compression of the brainstem), or Koos 4 (touching the brainstem with compression of the brainstem) . For patN = 243) or were found to have NF2 (N = 14) and were therefore excluded. Patients with no VS most frequently had a meningioma (N = 39), facial nerve schwannoma (N = 29) or intrachochlear schwannoma (N = 18). Furthermore, 25 patients had SNHL, seven had labyrinthine schwannoma, five had Meniere's disease, two had benign paroxysmal positional vertigo, and one had vestibular neuritis; none of these had imaging or audiometric evidence of retrocochlear pathology. An additional 117 cases had no evidence of any pathology involving the labyrinthine system, facial nerve, or vestibulocochlear nerve. Eighty-five patients were excluded due to existence of prior surgery or radiation in the area of the cochlear nerve preceding first audiometry. Six patients were excluded due to other reasons: three patients with glioma in addition to VS, one patient with Von Hippel-Lindau syndrome in addition to VS, and two patients with known long-standing contralateral deafness at time of index audiometry . Patients who did not meet criteria for NF2 but had one additional non-VS schwannoma or meningioma in addition to a unilateral VS (N = 28) were analyzed separately from the included patient population in order to compare these patients with suspected NF2, but not meeting strict criteria, with the general VS patient population, with plan to exclude them from final analysis if significant differences in outcomes were found (re found .p = 0.0035). Of all patients with unilateral VS, 274 patients (41.5%) eventually received surgery alone as treatment, 104 patients (15.7%) received radiotherapy alone, 14 patients (2.1%) received both surgery and radiotherapy and in 269 patients (40.7%) the tumor was monitored through watchful waiting without any surgical or radiologic intervention. In total, 534 patients had imaging within 12 months of index audiometry, and 518 within 6 months. The median tumor size was 12 mm, with a minimum of 1.5 mm to a maximum of 52 mm (standard deviation 7.9 mm). The remaining 127 patients could not be stratified by tumor size—these patients either had no imaging records available within 12 months of index audiometry or had undergone surgical or radiation treatment before the earliest available imaging. Patients with one additional non-VS schwannoma or meningioma were significantly older  and had smaller average tumor size , however did not differ compared to the general population in terms of sex distribution, tumor laterality, or treatment modality.After the exclusions noted above, a core population of 661 patients diagnosed with unilateral VS were identified and described in p = 0.0012) than in smaller tumors. Significance for female vs. male predominance in the population was only seen in Koos 4 tumors as well . Increasing Koos classification was associated with larger tumors and increasing likelihood of surgical intervention, while patients with lower Koos classification had smaller tumors and were more likely to be managed without either surgery or radiotherapy. Radiation therapy was most commonly applied to patients with Koos 2 and Koos 3 tumors; multimodal therapy, the least common approach, was primarily reserved for Koos 4 tumors.Of the 534 patients with contemporary baseline imaging available, 511 could be stratified by their tumor's Koos classification as shown in Baseline audiometric analysis, as shown in p = 0.008) or four-tone PTA criteria (p = 0.038). Median time to endpoint was 17.9 years in VS-contralateral ears by three-tone PTA criteria, and 17.7 years by four-tone PTA criteria  than other patient demographics, while distribution of the sexes did not differ when considering patients with Koos 4 classification and baseline abnormal VS-ipsilateral hearing, or in patients with Koos 1–3 tumor classification regardless of baseline hearing status.Evaluation of all of the above hearing outcomes by alternate PTA metrics, for example AAO-HNS hearing classification groups, revealed the same trends toward hearing loss over time as the analysis performed using either three- or four-tone PTAs.This retrospective study demonstrates that in patients with unilateral VS and baseline abnormal hearing in the VS-ipsilateral ear, the progression of SNHL in the contralateral ear is significantly greater than expected for unrelated age-associated hearing loss in the general population. This finding is limited only to progression of thresholds to the level of moderate hearing loss, however directionally similar non-significant trends are also noted for other threshold- and word understanding-based endpoints. This interesting finding needs further examination in a future prospective study using a large number of patients with carefully documented otologic histories and sound exposures, as the finding suggests that VS-secreted factors may affect hearing in the contralateral ear. In the meantime, an alternative explanation for our finding could also be that patients with baseline abnormal VS-ipsilateral hearing and accelerated hearing loss in the VS-contralateral ear have an underlying process that expedites bilateral hearing loss, such as history of unreported prior audiotrauma. Findings regarding progression of VS-ipsilateral hearing loss in patients with baseline normal hearing are in line with previous research . The impFor the majority of VS patients in our study, progression of VS-contralateral hearing loss is significantly delayed and of a less-severe degree than in the VS-ipsilateral ear. This suggests that if percolating VS-secreted factors or extracellular vesicles do reach the contralateral ear, they must either suffer some level of degradation during passage through CSF or blood, or become too diluted to exert the full-strength ototoxic effect beyond a certain distance from the tumor. It is also possible that an immune mediated mechanism could play a role in the pathophysiology of hearing loss progression, as immune and inflammatory mechanisms have previously been found to occur in other inner ear pathologies such as Ménière's disease, DFNA34 hearing loss and related autoimmune and autoinflammatory diseases of the inner ear –26. A grEither an inflammatory or immune-mediated pathway would have the potential to stimulate innate immune responses against the contralateral ear, however it is uncertain whether this effect would be consistent with changes in contralateral hearing observed. The classic finding for hearing loss caused by VS tumors would be loss of word understanding out of proportion to change in thresholds, which we observe in ipsilateral ears. However, in the contralateral ear we find that threshold change rather than change in word understanding is most significant. The shape of KM curves in Of key clinical significance, the lack of effect regarding higher-threshold endpoints or word understanding on contralateral hearing is a positive clinical indicator in patients with VS, and can provide some additional reassurance to patients in whom the contralateral ear is often their only hearing ear. In patients with normal baseline hearing in the VS-ipsilateral ear, assurance can be provided that no effect is seen on VS-contralateral hearing by any metric, however it would still be important to update patient expectations with any change in clinical status over time. Five patients with normal baseline hearing bilaterally did reach moderate VS-contralateral hearing loss at ≥17 years' follow-up , howeverOur study reveals a significant female predominance of VS, which is in line with female predominance for VS that has also been seen in previous retrospective studies –30. A pop = 0.0012). When evaluating tumor size in other patient groups, however, no correlation is observed between tumor size and patient age, and no correlation between tumor size and progression of hearing loss either ipsi- or contralaterally. Evaluation of long-term hearing in patients with Koos 4 tumors is difficult since most patients undergo either surgery or radiation therapy very soon after diagnosis, after which time they are less likely to continue with long-term audiometric follow-up. Patients with smaller tumors that do not compress the brainstem are more likely to be found incidentally or with mild symptoms, and are more likely to be followed without immediate intervention. Within Koos 1–3 patients, no correlation is found between tumor size and progression of hearing loss either ipsi- or contralaterally, which supports prior findings that tumor size alone is a poor predictor of hearing loss progression (Within the four Koos classification groups the age of Koos 4 patients was found to be significantly lower than in other groups (gression , 10.The age of patients with an additional non-VS schwannoma or meningioma, but not meeting strict NF2 criteria, is significantly higher compared to the unilateral VS group. It is possible that these older patients have simply had more time and opportunity to develop multiple sporadic schwannomas or meningiomas, even without predisposing NF2 mutation. That no difference is seen in either ipsi- or contralateral hearing loss progression in this patient population, compared to patients with unilateral VS only, is reassuring that they are not hiding an occult NF2 mutation, and supports use of current guidelines for limiting NF2 diagnosis to only patients with either bilateral VS, ≥3 schwannomas or meningiomas, or unilateral VS plus known family history.Given that splitting the VS patients by age, sex or tumor size showed no significant difference in SNHL progression, none of these subgroups seem to be confounders for contralateral hearing loss progression. Directionality and significance of results are shown to be consistent regardless of whether three- or four-tone PTA is used as the primary metric for threshold hearing; this finding is particularly valuable given that three-tone PTA measurements are most closely associated with speech reception thresholds, and thus of highest clinical utility, while mechanisms for progressive SNHL can often first affect only higher-threshold frequencies , 37. TheFirstly, due to the retrospective study design, availability of records was not complete for all patients, particularly in ability to assess tumor size in some patients. Audiometric follow-up is also highly variable, limiting granularity of longitudinal tracking of hearing outcomes. As Mass Eye and Ear is a tertiary referral center, patients in many cases may have undergone prior audiometry at outside facilities before initial presentation, and these records were not reliably accessible. Furthermore, for many patients with known VS undergoing long-term clinical surveillance, the contralateral ear was not tested at the same frequency or level of detail as for the ipsilateral ear, leading to the potential for premature censoring of some contralateral ears.Secondly, during the study period covering 24 years, improvements in MRI resolution could have influenced accuracy of tumor size assessment. However, this is unlikely because the smallest tumor noted is 1.5 mm, still detectable even with a 1.5 T MRI , and tumThirdly, the diagnosis of VS can only be made with 100% certainty through confirmative pathology, which is not available when watchful waiting or radiotherapy is applied. However, even in these cases the diagnosis of VS is very close to definitive because VSs are the most common tumors in the CPA and they lack distinctive radiographic features of other tumors such as the dural tail of a meningioma –43.Of particular interest to this analysis is the selection of appropriate case controls—patients with SNHL but no other known sensorineural otologic history and thus presumed presbycusis, as well as a similar interval for follow-up audiometry compared to the study population. A potential selection bias could be present within the case control group if patients with occult otologic history were included, and if this history were not evident based on superficial review of diagnostic codes alone. To minimize this bias we performed detailed chart review on any case control patients who demonstrated significant change in hearing over time, and replaced those with other otologic histories with “clean” controls for whom the baseline otologic disease burden was equivalent to those of VS-contralateral ears, as detailed in the Methods section. This finding reinforces the continued importance of detailed chart review in the context of large database analyses, since over-reliance on the “face value” of historical diagnosis codes can easily overlook key components to the patient history.This study represents to date the largest study tracking long term bilateral hearing outcomes in patients with VS. Our findings definitively demonstrate an increased risk of hearing loss in the VS-contralateral ear in patients with baseline VS-ipsilateral abnormal hearing. No variations in risk of contralateral hearing loss were found based on patient age, sex, tumor size, or degree of VS-ipsilateral hearing loss. In patients with baseline normal VS-ipsilateral hearing, no risk to long-term contralateral hearing was found by any metric or in any subgroup. Patients with baseline abnormal hearing in the VS-ipsilateral ear should be counseled of the increased risk to contralateral hearing, and additional care should be taken to avoid other otologic insults such as audiotrauma or potentially ototoxic medications. Alternately, patients with baseline normal VS-ipsilateral hearing can be reassured that the presence of a unilateral tumor does not predispose to worsening hearing loss in the contralateral ear, however should hearing loss in the VS-ipsilateral ear progress then the risk to hearing in the VS-contralateral ear may increase accordingly.In light of previous research indicating role of secreted factors that may contribute to accelerated hearing loss progression in VS patients, these results indicate that the composition of these secreted factors do appear to be conducive to long-distance percolation through CSF or blood, although likely with some degradation or dilution, given that the effect on contralateral hearing seen in this study is much slower and less severe than the effects seen in the VS-ipsilateral ear. Immune or inflammatory-mediated processes uniquely affecting the inner ear may also play a role. Understanding key characteristics of these potentially relevant mechanisms, and the interplay between them, can help guide future research to better characterize and evaluate the composition and role played by each of these mechanisms.konstantina_stankovic@meei.harvard.edu.The data analyzed in this study is subject to the following licenses/restrictions: Datasets can be made available upon request to interested parties. The primary dataset includes service dates for certain procedures which are considered protected under HIPAA guidelines, and as such cannot be shared publicly. Requests to access these datasets should be directed to The studies involving human participants were reviewed and approved by Partners Human Research Committee Massachusetts Eye and Ear Infirmary. Written informed consent for participation was not required for this study in accordance with the national legislation and the institutional requirements.KS conceived the project and supervised all the work. SE, ME, and KS designed the study. SE and CR collected data from patient charts. SE wrote code for data analysis. Primary analysis and interpretation were then performed by SE and CR, with input from all authors. SE, CR, and KS wrote the manuscript. All authors edited the manuscript and approved the final version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Therioaphis trifolii (Monell), Homoptera, Drepanosiphidae] is a well-known destructive pest that can significantly reduce alfalfa yields. Herein, the morphology of antennal sensilla of T. trifolii has been examined by using scanning electron microscopy and the ultrastructure of sensilla stellate and placoidea was described by transmission electron microscopy. Stellate sensilla, placoid sensilla, and coeloconic sensilla were found on the 6th segment, and a single sensillum placoidea was located on the 5th segment. Placoid sensilla were also present on the 3rd antennal segment of alate and apterous aphids, and the number was similar between two morphs. Two types of trichoid sensilla and coeloconic sensilla were found on the antennae, respectively. The results of ultrastructure showed that stellate sensilla are innervated by three neurons, while placoid sensilla present three groups of neurons, equipped with 2–3 dendrites in each neuron group. Immunocytochemical localization of odorant-binding proteins (OBPs) was performed on ultrathin sections of sensilla stellate and placoidea, and we observed that the antiserum against OBP6 intensively labeled all placoid sensilla from both primary and secondary rhinaria. OBP7 and OBP8 could also be detected in placoid sensilla, but less strongly than OBP6. In addition, OBP6, OBP7, and OBP8 were densely labeled in stellate sensilla, suggesting OBP6, OBP7, and OBP8 may sense alarm pheromone germacrene A in T. trifolii.The spotted alfalfa aphid [ Therioaphis trifolii (Monell) (Homoptera: Aphididae), is a cosmopolitan pest of legumes, mainly in the tribes Trifoliae and Loteae -β-farnesene and germacrene A, have been identified in aphids until now. (E)-β-Farnesene has been found in all studied species of subfamilies Aphidinae and Chaitophorinae, while germacrene A was identified only within the genus Therioaphis of the subfamily Drepanosiphinae -β-farnesene (E)-β-farnesene perception in most aphids, such as in Rhopalosiphum padi and Acyrthosiphon pisum  is still scanty and fragmentary. This study was conducted to investigate the function of antennae in T. trifolii by studying the distribution and fine structure of chemosensilla, using both scanning and transmission electron microscopy, and mapping the expression of OBPs in such sensilla. Our research offers data related to the candidate OBPs potentially involved in perception of semiochemicals in aphid T. trifolii, which will provide original strategies for aphid’s integrated management. Herein, we report on the morphology and ultrastructural characterization of the different types of antennal sensilla in SAA T. trifolii by scanning and transmission electron microscopy. In addition, the distribution and expression of OBP6, OBP7, and OBP8 in sensilla stellate and placoidea was investigated.While biochemical research on the olfactory system of aphids is rapidly progressing, information at the anatomical level for SAAs T. trifolii was reared on alfalfa (Medicago sativa) at 20–22°C, 60–70% relative humidity with a photoperiod of 16: 8 h (light: dark) at College of Grassland Science and Technology, China Agricultural University, Beijing, China.Spotted alfalfa aphid T. trifolii, twenty alate and apterous adult aphids were used in this study for scanning electron microscopy (SEM). The heads of all samples were carefully excised with fine forceps under a stereomicroscope. The heads were first kept in 70% ethanol for 48 h at room temperature and then cleaned in an ultrasonic bath (250 W) for 5 s in the same solution. After dehydrated by an ethanol serial solution  (For better confirmation of the number and types of sensilla on the antenna of 90–100%)  in each 4 in 0.1 M PBS (pH 7.2), and followed by dehydration in an ethanol series solutions  for 3 min each. After being dehydrated with pure acetone three times for 10 min each, the samples were embedded in Epoxide resin 618 through mixtures of 2: 1, 1: 1, 1: 2 of acetone and Epoxide resin 618  and then kept in pure Epoxide resin 618 overnight. Polymerization was accomplished with heating from 30 to 60°C (5°C/6 h), at 60°C for 48 h in tightly closed gelatin capsules filled completely with the resin monomer. Ultrathin sections were cut with a diamond knife  on a Leica EM UC6 microtome  and then mounted on Formvar-coated grids. The sections were observed on a HITACHI H-7500 TEM . Pictures were only adjusted for brightness and contrast.The antennae used for Transmission electron microscopy (TEM) were excised and prefixed for 2 days with paraformaldehyde (4%) and glutaraldehyde (2.5%) in 0.1 M phosphate buffered saline , then postfixed for 1 h with 1% OsOThe antennae used were prefixed in paraformaldehyde (4%) and glutaraldehyde (2%) in 0.1 M PBS (pH 7.4) and then dehydrated in an ethanol series. The samples were embedded in LR White resin, and ultrathin sections were cut and mounted on Formvar-coated grids. For immunocytochemistry, the grids were subsequently floated, each time for 5 min, on 25-μL droplets of the following solutions, along with the procedure adapted from A. pisum were kindly provided by Dr. Paolo Pelosi, University of Pisa . Image analysis was performed with ImageJ .In this study, the antisera against OBP6, OBP7, and OBP8 of  of Pisa , and useT. trifolii are composed of three parts: a scape (Sc), a pedicel (Pe), and a long flagellum (F), with a total length of 1.8 mm .The results showed that the antiserum against OBP6 of ectively . The lymectively , with a The stellate sensilla on the 6th segment were also labeled by OBP6, OBP7, and OBP8 antisera, mainly in the branches and sensillum lymph surrounding the dendrites .T. trifolii.In this study, we investigate the structure, morphology, and distribution of sensilla and the expression of three OBPs  in the antenna of SAA T. trifolii also contained six segments. Based on external morphology, the antennae sensilla of SAA are classified into four types, including placoid sensilla, stellate sensilla, coeloconic sensilla, and trichoid sensilla. One striking observation is the presence of stellate sensilla on the 6th segment of primary rhinaria in this aphid. To our best knowledge, stellate sensilla were only identified in aphid species in the subfamily Drepanosiphinae -β-farnesene has been found in all studied species of subfamilies Aphidinae and Chaitophorinae, while germacrene A was identified only within the genus Therioaphis of the subfamily Drepanosiphinae (E)-β-farnesene in both M. persicae and A. pisum (E)-β-farnesene which is the only component of the alarm pheromone in M. persicae and A. pisum (Immunocytochemistry experiments have been used widely to study the location of OBPs in insects . Most lisiphinae . Our resA. pisum . Our immA. pisum . WhetherOverall, we identified the main sensilla types on the antenna of alfalfa spotted aphid, whose alarm pheromone is different from other aphids. Using TEM, we clarified the ultrastructure of stellate sensilla, which is absent in other aphid besides the subfamily Drepanosiphinae. Our findings will enrich recognition to the antennae sensilla of aphids. In addition, our study will provide insights into determining new strategies for control of these worldwide pests by interfering with their chemical communication.The original contributions presented in the study are included in the article/LB conceived the project and designed the research. LS, YL, and YS performed the research. LS, XW, and LB analyzed the data and wrote the manuscript. All authors reviewed and approved the manuscript for publication.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.


Hearing loss affects access to spoken language, which can affect cognition and development, and can negatively affect social wellbeing. We present updated estimates from the Global Burden of Disease (GBD) study on the prevalence of hearing loss in 2019, as well as the condition's associated disability.We did systematic reviews of population-representative surveys on hearing loss prevalence from 1990 to 2019. We fitted nested meta-regression models for severity-specific prevalence, accounting for hearing aid coverage, cause, and the presence of tinnitus. We also forecasted the prevalence of hearing loss until 2050.An estimated 1·57 billion  people globally had hearing loss in 2019, accounting for one in five people (20·3% [19·5–21·1]). Of these, 403·3 million (357·3–449·5) people had hearing loss that was moderate or higher in severity after adjusting for hearing aid use, and 430·4 million (381·7–479·6) without adjustment. The largest number of people with moderate-to-complete hearing loss resided in the Western Pacific region (127·1 million people [112·3–142·6]). Of all people with a hearing impairment, 62·1% (60·2–63·9) were older than 50 years. The Healthcare Access and Quality (HAQ) Index explained 65·8% of the variation in national age-standardised rates of years lived with disability, because countries with a low HAQ Index had higher rates of years lived with disability. By 2050, a projected 2·45 billion (2·35–2·56) people will have hearing loss, a 56·1% (47·3–65·2) increase from 2019, despite stable age-standardised prevalence.As populations age, the number of people with hearing loss will increase. Interventions such as childhood screening, hearing aids, effective management of otitis media and meningitis, and cochlear implants have the potential to ameliorate this burden. Because the burden of moderate-to-complete hearing loss is concentrated in countries with low health-care quality and access, stronger health-care provision mechanisms are needed to reduce the burden of unaddressed hearing loss in these settings.Bill & Melinda Gates Foundation and WHO. Hearing loss is common and can negatively affect multiple aspects of an individual's life when unaddressed or when individuals' communication needs are unsupported. Auditory deprivation can detract from quality of life and access to spoken communication, which can impede development of child spoken languageLancet Commission on Global Hearing Loss aims to examine how to reduce the burden of hearing loss, convening expert working groups on prevention, policy, technology, and protection.The Lancet are complemented by plans from WHO to release the first-ever world report on hearing. The report seeks to utilise best available evidence to present a consistent narrative on hearing loss and hearing health care, call attention to priorities and best practices for hearing health care, and describe trends in the global distribution of hearing loss.The effect of hearing loss is broadly recognised by several stakeholders, including researchers, clinicians, policy makers, and people living with the condition.Researchers have called for urgent multi-disciplinary action on hearing health care, including comprehensive screening programmes, increased access to hearing devices, and noise-reduction strategies.Evidence before this studyThe prevalence of hearing loss is estimated annually through the Global Burden of Disease (GBD) study, a systematic overview of the prevalence of 369 diseases and injuries. The latest GBD study on hearing loss was based on estimates from 10 years ago. Since then, we have obtained new sources of data through systematic reviews of population-representative studies, collaborator input, and additional targeted searches. Sources up to Dec 31, 2008, were obtained from a previously published systematic review. In GBD 2013, we did a systematic review of sources published 2008–13 onward using the following PubMed search string: “(hearing loss[Title/Abstract] OR deafness[Title/Abstract] OR hearing loss[Title/Abstract]) AND  AND (“2008”[PDAT] : “3000”[PDAT]) AND ”.In GBD 2016, we did an update systematic review of sources published between Nov 26, 2008, and Nov 30, 2016, using the following PubMed search string: “(hearing loss[Title/Abstract] OR deafness[Title/Abstract] OR hearing loss[Title/Abstract] OR audiometry[Title/Abstract]) AND  AND (“2008/11/26”[PDAT]: “3000”[PDAT]) AND ”, without any language restrictions. Sources that included self-reported data, did not report hearing loss in the less severe ear, were not population representative, or did not report a definitive decibel-level threshold for reported hearing loss were excluded. Sources that reported bilateral hearing loss according to the GBD reference definition were included.Added value of this studyThe GBD hearing loss paper published in 2010 was informed by 42 studies in 29 countries. Our analysis provides an update that is informed by 215 survey sources from 77 countries. Method changes for the GBD 2019 iteration include new methods of adjusting data using non-standard hearing thresholds and splitting data with gender unspecified by sex. These GBD estimates are accompanied by forecasts of hearing loss prevalence until 2050, providing a comprehensive picture of current and future disease trends. We found that 1·57 billion people  had hearing loss in 2019, contributing to 43·45 million (29·68–61·80) years lived with disability as the third largest cause of disability in GBD. The global number of individuals with hearing loss is also projected to increase by 56·1% (47·3–65·2) in the next 30 years despite stable age-standardised prevalence.Implications of all the available evidenceThis study accompanies the 2021 WHO World Hearing Report, which describes the burden of hearing loss using the GBD 2019 results and standards for ear and hearing care, and sets standards for policy and prevention. Our analysis provides evidence that hearing loss is largely caused by ageing, will increase in prevalence in coming years, and is more prevalent in countries with low health-care access. Cost-effective, preventive, and treatment interventions for hearing loss are available, including school-based screening programmes, hearing devices , and clinical management of ear disease. Health-care services must be prepared for large projected increases in burden, particularly in low-income and middle-income countries where ear specialists and audiologists are scarce.The Global Burden of Diseases, Injuries, and Risk Factors (GBD) Study is a comprehensive attempt to quantify the contribution of hearing loss relative to other causes of ill health. The study provides annual data on the prevalence and associated levels of disability for 369 diseases and injuries, as well as 87 risk factors. Estimates are updated annually, most recently for GBD 2019—the most recent GBD paper on hearing loss was based on GBD 2010 estimates.The 2019 GBD produced estimates for 369 diseases and injuries; high-level methods have been described in detail elsewhere.In addition to prevalence and incidence, GBD uses the years lived with disability (YLDs) metric to compare the morbidity associated with different non-fatal conditions. YLDs are calculated by multiplying the prevalence of a condition with its associated disability weight, reflecting the severity of that disease relative to all other health states. Disability weights range from 0  to 1, which is equivalent to death.This study complies with the Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER) recommendations .16GBD defines hearing loss as the quietest sound an individual can hear in their better ear, taken as the pure-tone average of audiometric thresholds of 0·5 kHz, 1 kHz, 2 kHz, and 4 kHz. Hearing loss is reported in the GBD by seven mutually exclusive severity categories .17 Two hThis manuscript was produced as part of the GBD Collaborator Network and in accordance with the GBD Protocol.We used input data obtained via systematic reviews of epidemiological, population-representative surveys. Sources up to Nov 26, 2008, were obtained via a published systematic review, For data sources that reported prevalence by age and sex separately, we applied the proportion of female and male prevalence to age-specific data. We then ran a meta-regression on the log ratio of female and male prevalence in MR-BRT .To model hearing loss, we first ran three DisMod-MR 2.1 models to estimate the prevalence of no hearing loss (0–19 dB), mild hearing loss (20–34 dB), and moderate-to-complete hearing loss (≥35 dB). Socio-demographic Index Fourth, severity-specific prevalence of hearing loss was adjusted to account for hearing aid usage . We calcFifth, we estimated the prevalence of hearing loss due to underlying causes—ie, chronic otitis media, congenital birth defects, meningitis, and age-related or other factors . From biSixth, we estimated the prevalence of hearing loss with and without tinnitus . We estiResults are presented by Healthcare Access and Quality (HAQ) Index as well as by WHO region. HAQ Index is a summary measure of the quality of national health systems that ranges from 0 to 100 and is based on analysis of avoidable deaths for 32 causes (methods described elsewhere).WHO member states are classified into six distinct regions: the Western Pacific region, South-East Asia region, European region, Region of the Americas, African region, and Eastern Mediterranean region . RegionaForecasts of hearing loss prevalence were generated using age-specific prevalence rates for the years 1990, 1995, 2000, 2005, 2010, 2015, and 2019 as input data into a regression, with year, WHO region, and age as predictors. We included an interaction term between region and year and a cubic spline on age. Sex-specific regression models were run 1000 times, and the resulting coefficients were used to predict rates in the years 2030, 2040, and 2050. Predicted rates were multiplied by forecasted population for each WHO location to obtain case numbers, and then aggregated to obtain global estimates.Source counts were calculated by summing all surveys that were considered for incorporation into the model, including those that were eventually excluded from the analysis . We counted a survey reporting data from multiple countries as multiple data sources. In total, input data consisted of 215 survey sources in 77 countries . Modelling of hearing loss prevalence considered 113 survey sources in 54 countries. Modelling of hearing aid coverage considered 100 survey sources in 44 countries. Other data came from ten data sources in two countries (data coverage and age-standardised coverage rates are shown in the An estimated 1·57 billion (95% UI 1·51–1·64) people had hearing loss in 2019, accounting for 20·3% (19·5–21·1) of the global population. Of these, 1·17 billion (1·12–1·22) people (74·3% [71·8–76·8]) had mild hearing loss. 12·65 million (10·34–15·48) individuals had complete hearing loss. Without adjustment for hearing aid use, 430·4 million (381·7–479·6) people globally had moderate-to-complete hearing loss in the better-hearing ear.Globally, the number of people with moderate-to-complete hearing loss increased from 225·3 million (95% UI 197·6–250·9) in 1990, to 403·3 million (357·3–449·5) in 2019, a 79·1% (73·8–84·1) increase.Age-standardised prevalence of moderate-to-complete hearing loss remained constant over the same period , from 25·02 million (16·96–35·34) to 43·45 million (29·68–61·80). Of the YLDs attributed to hearing loss in 2019, 65·2% (52·5–76·6) were caused by moderate-to-complete cases and 34·8% (23·4–47·5) were caused by mild cases. In 2019, 7·00 million (4·76–10·06) YLDs were attributable to occupational noise exposure .r2 0·66).The burden of all hearing loss is greatest at lowest levels of the HAQ Index, with a difference of more than 3 times in YLD rates between countries with the lowest and highest HAQ Index values . A lineaAlthough 66·6% (95% UI 62·9–69·9) of moderate-to-complete hearing loss cases were moderate in severity (35–49 dB), this severity accounted for 34·0% (26·2–42·6) of disability attributed to moderate-to-complete hearing loss . Of all GBD Compare.Across the age spectrum, hearing loss was most severe in those approximately younger than 5 years and those older than 70 years, meaning that the proportion of cases that were moderately severe, severe, profound, or complete was much larger in these age groups . HearingThe cause of hearing loss changed from infections and congenital birth defects to other factors over age . Under aBetween 1990 and 2019, the crude prevalence rate of all hearing loss increased by 27·8% (95% UI 26·6–29·0), from 15·9% (15·3–16·6) in 1990 to 20·3% (19·5–21·1) in 2019. By contrast, the global age-standardised prevalence rate of all hearing loss remained stable, changing from 19·1% (18·4–19·9) in 1990 to 19·3% (18·5–20·0) in 2019. The increase in hearing loss cases while age-standardised reates remained stable indicates that increases in prevalent cases are driven by population growth and ageing.By 2050, a projected 2·45 billion (95% UI 2·35–2·56) people will have hearing loss, a 56·1% (47·3–65·2) increase from 2019, despite stable age-standardised prevalence . An estiResponsible for over 40 million YLDs, hearing loss was ranked as the third most common cause of YLDs in the GBD. Compared with other disease categories in the GBD, age-related and other hearing loss was the third largest cause of global YLDs in 2019 after low back pain and migraine, and was ranked first among sensory disorders. Age-related and other hearing loss was the leading cause of global YLDs compared with all causes that were explicitly modelled in the GBD for individuals older than 70 years.Over 1·5 billion people live with hearing loss, 403 million 26%) of whom have moderate-to-complete hearing loss in their better ear. All others have mild hearing loss. Although referred to as mild, such hearing loss can cause difficulties depending on its nature and the individual's hearing needs.% of whomThe distribution of individuals with moderate-to-complete hearing loss varies across regions. Geographical variation could be attributable to several factors, including the prevalence of occupational noise exposure, preventable infections such as chronic otitis media and meningitis, and health-care access. A clear association exists between ageing and hearing loss, given that most of those with hearing loss are older than 50 years. The progression of hearing loss with age also means that high-income countries have the highest all-age prevalence of hearing loss, driven mainly by their ageing population profile.Although hearing loss is common in old ages, globally 70 million children aged 0–15 years also live with this condition. Although the prevalence of hearing loss is low in children compared with in adults, hearing loss was most severe in both the youngest and oldest individuals. When unaddressed, childhood hearing loss can affect spoken language development, literacy skills,The clear association between hearing loss and age means that nearly everyone, if they live long enough, will have some degree of hearing loss, and at least 50% will have moderate-to-complete hearing loss requiring intervention. As the world population grows and ages over the coming decades,Although hearing loss poses a substantial burden that will increase in coming years, methods of addressing this burden are available and cost-effective. Models indicate that passive screening in conjunction with hearing aid provision is an efficient intervention, with a cost of almost US$1000 per disability-adjusted life-year averted.27–31,33 Health-care services need to be prepared for the projected increases in burden, particularly in low-income and middle-income countries where ear specialists and audiologists are scarce.Our study was developed in close collaboration with WHO and links closely with its world report on hearing. This report further elaborates on the public health implications of the rising prevalence of hearing loss. With the figures and projections noted in our study as its basis, the world report outlines the framework of a global public health response that is focused on integrated people-centred ear and hearing care. By the use of available technological solutions with evidence-based public health approaches, hearing loss can be prevented, identified, treated, and rehabilitated, to curtail the condition's projected increase in prevalence and overcome the adverse affects on individuals and society. This approach includes cost-effective interventions and strategies such as hearing screening for newborn babies, school-aged children, adults, and older adults as well as the use of hearing technology  and clinical management of ear diseases.We acknowledge the limitations of this study, most importantly the sparsity of the data on which these estimates are based. The lack of prevalence data is most marked in low-income countries, which have increased prevalence of severe hearing loss and insufficient access to audiometric technologies required for diagnosis. Data on hearing aid coverage is particularly sparse, with no severity-specific data outside of high-income countries and almost no data sources at all in Asia, north Africa, or Central Africa. This data gap might lead to overestimation of hearing aid coverage  in low-income or under-represented locations. Moreover, we exclusively relied on NHANES data to calculate severity adjustment factors for hearing loss prevalence and split prevalence by presence of tinnitus, neglecting geographical variation in the prevalence of hearing loss and tinnitus. Additional research is needed to gain a deeper understanding of hearing loss prevalence, concurrence with tinnitus, and hearing aid coverage in areas where data are limited.Data on the causes of hearing loss are also sparse because few surveys report prevalence of hearing loss by underlying cause. This difficulty presents challenges because the causes of hearing loss differ substantially in children compared with in adults.Although meta-regression tools enable us to leverage information from data-rich locations to estimate prevalence in locations with no data, data sparsity can make distinguishing between true variation in prevalence and measurement error particularly difficult. This issue is compounded by few predictive covariates or risk factors, because the association between hearing loss and other factors (like noise exposure) is not well quantified and likely to be masked by age. Data on self-reported hearing loss or audiometric data recorded with mobile technologies could potentially assess disease burden in locations where audiologists are sparse. However, telehealth methodologies are not yet widely used, and the generalisability of self-reported data is unclear.GBD estimates of hearing loss are adjusted for hearing aid coverage, shifting the proportion of people with a hearing aid in each severity category to the category directly below. This adjustment might be crude in nature, masking the effect of hearing health care in reducing disability and neglecting variation in treatment effect between individuals. Whereas providers in eye care refer to best-corrected vision loss to mobilise resources towards those who are most amenable to treatment, no complementary best-corrected measure for hearing loss exists. Acquisition of data on best-corrected hearing loss could contribute to an understanding of the proportion of individuals with hearing loss who are amenable to intervention.A systematic review of hearing loss prevalence will be completed for GBD 2020 to identify new sources of information in data-sparse locations. Additionally, we aim to revise modelling methods in upcoming years, assessing how prevalence is adjusted on the basis of hearing aid coverage, the proportion of individuals with hearing loss concurrent with tinnitus, and the severity distribution of hearing loss due to otitis media. We aim to forecast the avoidable burden of hearing loss with rapid implementation of hearing health-care interventions, provided additional data on intervention coverage is obtained. This forecast could provide policy makers with tools to effectively allocate hearing health-care services and plan for future scenarios.The results of this study point to a growing public health challenge, which needs global attention and a definitive response. The increasing prevalence of hearing loss, high contribution to global disability, and large unmet need for hearing aids together serve as a call for urgent attention. Cost-effective, preventive, and treatment solutions to mitigate the effects of hearing loss exist, including childhood screening programmes, earplugs and other noise-reduction technologies, hearing devices, and early treatment of otitis media and meningitis. Health system capacity must be scaled up to address growing needs, particularly in low-income settings.tvos@uw.eduCorrespondence to: Prof Theo Vos, Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA 98195, USA https://vizhub.healthdata.org/gbd-compare.Data presented in this manuscript are made publicly available at


Due to the close anatomical relationship between the auditory and vestibular end organs, hearing-impaired children have a higher risk for vestibular dysfunction, which can affect their (motor) development. Unfortunately, vestibular dysfunction often goes unnoticed, as vestibular assessment in these children is not standard of care nowadays. To timely detect vestibular dysfunction, the Vestibular Infant Screening–Flanders (VIS–Flanders) project has implemented a basic vestibular screening test for hearing-impaired infants in Flanders (Belgium) with a participation rate of 86.7% during the first year and a half. The cervical Vestibular Evoked Myogenic Potentials (cVEMP) test was applied as vestibular screening tool to map the occurrence of vestibular (mainly saccular) dysfunction in this population. At the age of 6 months, 184 infants were screened. No refers on vestibular screening were observed in infants with permanent conductive hearing loss. In infants with permanent sensorineural hearing loss, a cVEMP refer rate of 9.5% was observed. Failure was significantly more common in infants with severe-profound compared to those with mild-moderate sensorineural hearing loss (risk ratio = 9.8). Since this is the first regional study with a large sample size and successful participation rate, the VIS–Flanders project aims to set an example for other regions worldwide. Several studies in young children with a bilateral severe vestibular dysfunction have shown a reduced balance performance and a delayed acquisition of gross motor milestones 10. Vestibular dysfunction can also influence fine motor skills, as well as writing, reading and learning skills, and may even hamper the cognitive and socio-emotional development of children17. Timely detection of vestibular dysfunction is crucial in order to provide parental counselling and start adequate vestibular rehabilitation at a young age19. Therefore, a standard vestibular assessment is needed in young children that are at risk for a vestibular dysfunction, such as hearing-impaired children. Because of the close anatomical and embryological relationship between the peripheral auditory and vestibular organs, it seems evident that whatever reason causes damage to the auditory structures, may also negatively affect the vestibular end organs20. This was confirmed in a systematic review by Verbecque et al. who demonstrated a significantly higher occurrence of vestibular dysfunction in children with sensorineural hearing loss compared to normal-hearing children in all included studies21.The vestibular end organs play an essential role in the maintenance of balance control and gaze stabilisation during posture and movements25. However, paediatric vestibular dysfunction often goes unnoticed due to the atypical expression of vestibular symptoms and the limited communicative abilities of young children26. Additionally, paediatric vestibular assessment remains challenging and time-consuming, and child-friendly equipment and two experienced examiners are often needed. Therefore, paediatric vestibular assessment in clinical practice is only performed in specialized centres that have appropriate equipment, and is mostly limited to cochlear implant candidates31 and children with a suspicion of vestibular dysfunction32. To overcome the lack of vestibular assessment in young hearing-impaired children, the Vestibular Infant Screening–Flanders (VIS–Flanders) project has been set up in June 2018 in Flanders (Belgium) in order to give each newborn with a confirmed hearing loss access to a basic screening of the vestibular function by using only one vestibular test. This Flemish research project includes a standard vestibular screening by means of the cervical Vestibular Evoked Myogenic Potentials (cVEMP) test at the age of 6 months33. Although the vestibular screening by means of the cVEMP mainly evaluates saccular function and does not evaluate all vestibular end organs, the cVEMP is chosen as screening tool because this is a short, objective and child-friendly test35. Several studies have also demonstrated a higher percentage of otolith dysfunction compared to semicircular canal dysfunction in hearing-impaired children due to the closer anatomical and embryological relationship between the otolith organs and the cochlea38. Furthermore, the results of the cVEMP strongly correlate with the motor performance of hearing-impaired children, as the otoliths detect linear and gravitational accelerations during translational movements10. The rationale for vestibular screening at the age of 6 months is the following: (1) the hearing loss is confirmed in the majority of the children by that age39, (2) gross motor milestones can already give an idea of the child’s vestibular function3, and (3) most children have already developed sufficient head stabilisation due to sufficient development and control of neck musculature, which is fundamental for reliable cVEMP assessment40. In addition, possible cochlear implant surgery which entails a potential risk for vestibular (mainly otolith) deficits43, has not been performed yet44. As a result, the vestibular (mainly saccular) status is known before some of these children will undergo cochlear implant surgery. This early screening enables a timely referral to limit the impact on the child’s motor development19. The rationale of implementing this screening specifically for hearing-impaired children is their higher risk for vestibular dysfunction as mentioned earlier. Moreover, the vestibular screening could be perfectly added to the existing neonatal hearing screening programme for all newborns in Flanders (Belgium) 46. Since all reference centres have auditory brainstem responses (ABR) equipment, which includes a cVEMP module, the implementation of the vestibular screening is practically feasible on a large scale. After confirmation of the hearing loss, the vestibular screening is scheduled at the age of 6 months in one of the reference centres  and included both normal-hearing and hearing-impaired infants.Recently, there is an increasing interest among clinicians in the vestibular function of hearing-impaired children and several researchers have proven the feasibility of vestibular testing from an early age on by adapting the standard test protocol to childrenThe aim of this paper is to report the vestibular screening results obtained in the first cohort of hearing-impaired infants enrolled in the VIS–Flanders programme and to increase awareness about vestibular dysfunction in these children. Therefore, this is the first study using the cVEMP as a standard vestibular screening tool on a large regional scale for hearing-impaired infants, regardless of their degree and type of hearing loss. These results will enable a more accurate and representative estimation of the occurrence of vestibular (mainly saccular) dysfunction in hearing-impaired infants.All infants with a confirmed permanent hearing loss  detected by the neonatal hearing screening programme were screened for a possible vestibular dysfunction in one of the 25 reference centres involved in the hearing screening programme. Infants with early-onset permanent hearing loss (before 10 months of age)  were also included in the study. To determine the hearing loss characteristics, the results of the click-evoked ABR, high frequency tympanometry (1000 Hz), and transient evoked or distortion product otoacoustic emissions (OAE) were collected across all centres. The degree of hearing loss was categorized in accordance with the criteria of the International Bureau for Audiophonology. In subjects with bilateral hearing loss, the worst ear was taken into account to categorize the degree of hearing loss. The leading ethical committee of the Ghent University Hospital and all local ethical committees of the participating centres approved data collection of all subjects (registration number B670201835971). According to the Helsinki Declaration, written informed consents of parents were obtained before the start of the vestibular screening test.33. To circumvent frequently occurring middle ear disorders in infants, bone-conducted stimuli  were presented at the ipsilateral mastoid48. More specific, 500 Hz tone bursts were used with a rise/fall time of 1 ms and a 2 ms plateau time, an intensity level of 59 decibel normalized hearing level (dB nHL) ), and a stimulus repetition rate of 5 Hz. In all participating centres, the Neuro-Audio commercial device and accompanying software  was used to automatically record and visually monitor electromyographic (EMG) background activity on a screen. The electromyographic (EMG) activity was measured by placing 1 ground electrode on the forehead, 1 reference (i.e. inverting) electrode on the sternum (i.e. between 1 and 2 cm below the sternoclavicular junction) and 2 active (i.e. noninverting) electrodes symmetrically on both bellies of the sternocleidomastoid (SCM) muscles. Subsequently, all participating centres were instructed to apply impedances of the self-adhesive electrodes below 5 kΩ and inter-electrode impedances below 2 kΩ before performing the vestibular screening test. The algorithm of the software automatically applied a pre-stimulus EMG recording of at least 20 ms to quantify the EMG background activity. Data acquisition was automatically accepted if the mean rectified voltage (MRV) values ranged between 80 and 250 µV and rejected outside this range. The EMG signals underwent amplification (5000 times) and bandpass filtering (10–1500 Hz). Minimum 35 and maximum 100 accepted sweeps were recommended and averaged for each trial.Around the age of 6 months, hearing-impaired infants were screened with the cVEMP test, as depicted in the previous publication of Martens et al.33. In this way, the child was motivated to maintain sufficient and stable SCM muscle contraction. Both examiners could observe the automatically EMG controlled recording on the screen in order to compare SCM muscle tension within and between the different trials of both sides. At least two trials were recorded on each side to check the reproducibility of the waveform. If more than two reproducible trials were recorded, two trials with comparable SCM muscle tension (i.e. preferred difference in averaged EMG levels ≤ 30 µV) were selected for further analysis on each side. To assure that all centres applied the same procedure and that reliable cVEMP results were obtained, one audiologist of the VIS–Flanders team was responsible to train and support all centres in performing the screening.One examiner operated the software, while the second examiner kept the child and the bone conductor in place during monaural stimulation. During the screening, the subjects were placed with the upper body upon a sloping pillow in supine position. Thereby, the examiner rotated and raised the head towards the contralateral (non-test) side and placed the bone conductor with the index finger at the ipsilateral (test) mastoid without touching the helix of the auricle, while slightly supporting the head with the other hand. During each acquisition, special attention was paid to ensure that the bone conductor was always correctly kept in the above described position. At the same time, the parent provided distraction at the contralateral side with some toys or a moviecVEMP responses are considered as normal (i.e. pass) if at least two reproducible biphasic P1-N1 waveforms are observed. Additionally, the rectified amplitude of at least one of the trials needs to reach the normative cut-off value of 1.3, which is based on normative data of the Ghent University Hospital obtained in a group of 34 healthy control subjects . cVEMP responses are considered as aberrant (i.e. refer) in case of inconclusive (i.e. insufficient SCM muscle tension), abnormal  or absent (i.e. no reproducible waveforms) responses.33.Figure p < 0.05.The Statistical Package for Social Science (SPSS) software  was applied for data analysis. Descriptive statistics were used to compare the screening results among different groups regarding the degree, laterality and type of hearing loss. The two-tailed Fisher’s Exact test was used in infants with sensorineural hearing loss to evaluate the association between the screening results , the laterality of sensorineural hearing loss  and the degree of sensorineural hearing loss . The latter associations were considered as statistically significant if From June 2018 until February 2020, vestibular screening was offered to 191 infants. Four of these infants were excluded from the dataset because further audiological assessment showed normal hearing. In one case, the parents withdrew their consent. Moreover, two additional cases were excluded as the first vestibular screening results were inconclusive (i.e. insufficient SCM muscle tension) and the parents refused the second screening test. The vestibular screening results of 184 infants  were included in the analysis. At the moment of the first screening, the mean age of the infants was 6.8 months (standard deviation (SD): 1.8 months). 8.7% (16/184) of these infants were rescheduled for a second vestibular screening . During the second screening, the infants had a mean age of 9.3 months (SD: 2.2 months). None of the infants received cochlear implants before the first or second screening. A unilateral or bilateral permanent sensorineural hearing loss was reported in the majority of the subjects (91.8% (169/184)), whereas a unilateral or bilateral permanent conductive hearing loss  was less frequently found (8.2% (15/184)). None of the children had a mixed type of hearing loss. A congenital hearing loss was found in 98.9% (182/184), whereas an early-onset hearing loss (i.e. before the age of 10 months) was reported in 1.1% (2/184) of the subjects. Both infants had sensorineural hearing loss caused by meningitis at the respective age of 2 months and 4 months.45. Consequently, the percentage of the target population with a congenital hearing loss subjected to the vestibular screening during the first 21 months of this project was estimated at 86.7% (182/210) (i.e. participation rate).The Flemish infant welfare agency ‘Kind en Gezin’ reported a permanent congenital hearing loss  in 122 infants on average per year, which is based on the most recently available data (i.e. between 2013 and 2016)All infants with a permanent conductive hearing loss n = 15) finally passed the vestibular screening test on both sides. More specifically, bilateral pass was found in 93.3% (14/15) on the first vestibular screening test, whereas 6.7% (1/15) needed a retest due to insufficient SCM muscle tension. Only infants with permanent sensorineural hearing loss  were taken into account for further analysis. In infants with sensorineural hearing loss (n = 169), bilateral pass was found in 90.5% (153/169) of the infants tested, yielding a refer rate of 9.5% (16/169). Table 5 finallyp = 0.784). Unilateral absent cVEMP responses were found at the same side of the hearing loss in all six infants with a unilateral hearing loss who failed the screening (Table p = 0.003). Noteworthy, only one subject with a mild-moderate hearing loss failed the vestibular screening  dysfunction based on the cVEMP screening results of a representative group of hearing-impaired infants. Secondly, this study investigated whether the vestibular screening results differed among various hearing loss characteristics, including the type, degree and laterality.47. A number of other reasons could account for the different participation rate of both studies, such as the different ages of the study participants. Verrecchia et al. (2019) conducted the cVEMP test in younger infants  compared to the VIS–Flanders project . Moreover, the VIS–Flanders project solely focussed on infants with a confirmed hearing loss, whereas Verrecchia et al. (2019) also included normal-hearing infants at risk for hearing impairment. The higher participation rate in the current study may also be explained by the strong collaboration between the VIS–Flanders project and the meticulously organised neonatal hearing screening programme in Flanders, which enabled a large-scale implementation for the entire target population. The above mentioned differences emphasize the added value of implementing the cVEMP as a standard screening tool after the confirmation of the hearing loss around the age of 6 months. By then, parents are probably less likely to refuse the cVEMP test because some time is given first to emotionally process the child’s hearing loss, to start the child’s auditory rehabilitation, and to be properly informed about the importance of vestibular screening.In this study, 86.7% of the estimated target population participated to the vestibular screening. This finding demonstrates that it is indeed feasible to implement a vestibular screening test, covering the majority of congenitally hearing-impaired infants across an entire region. Nevertheless, an estimated 13.3% of the infants probably missed the vestibular screening, which may be attributed to parents who declined their child’s participation, subjects who did not show up at several appointments, subjects who moved abroad after birth, and critically ill infants in which auditory and vestibular evaluations were not a number one priority during the first year of life. Whereas a rather high participation rate was observed in our study, Verrecchia et al. (2019) reported a participation rate of only 60% in their target group. The authors of the latter study attributed the low participation rate to the preoccupation of the parents with the outcome of the hearing tests50, which indicated that the anatomical proximity of the cochlea and the vestibular end organs played a major role in the higher risk for vestibular dysfunction in sensorineural hearing-impaired infants. All children with a permanent conductive hearing loss in the latter study showed normal bone-conduction cVEMP responses49. Therefore, it is assumed that otolith (mainly saccular) dysfunction is less likely to occur in children with a permanent conductive hearing loss. In infants with sensorineural hearing loss, a refer rate of 9.5% was found in the current study, consisting of 7.7% of infants with unilateral or bilateral abnormal or absent cVEMP results and 1.8% of infants with inconclusive results. The presence of vestibular (mainly saccular) dysfunction remained unknown in the infants with inconclusive results caused by bilateral insufficient SCM muscle tension. Noteworthy, these infants were also classified in the refer group, because the lack of sufficient head stabilisation suggests the presence of a vestibular (otolith) dysfunction or a delayed motor development5. This implies that this specific group definitely needs referral for motor assessment. In contrast to our findings, the systematic review of Verbecque et al. reported a considerably higher percentage of deviant cVEMP results  on at least one side in children with sensorineural hearing loss21. This higher percentage can be explained by the fact that the included study populations in this systematic review mainly consisted of older children, which can result in different cut-off values, delayed-onset vestibular dysfunction and potential post-cochlear implant effects31. Moreover, most of the included studies focussed on children with severe-profound hearing loss21, whereas the current study also included children with mild-moderate hearing loss. Nevertheless, the cVEMP refer rate of 14.7% in children with severe-profound hearing loss in the current study is still lower compared to the included studies by Verbecque et al.21. However, these included studies were conducted in specialized centres for cochlear implantation, congenital cytomegalovirus infection, and complex pathologies, thus, possibly included subjects with a higher risk for vestibular dysfunction. While the majority of the included studies applied the cVEMP with air-conduction stimuli21, the current study used bone-conduction stimuli. The use of different stimuli may also explain different percentages of aberrant cVEMP results. Although saccular afferents predominantly project to cervical muscles, bone-conduction and air-conduction cVEMP tests stimulate the saccular macula with different modalities53. In other words, the mechanisms of activating otolithic receptors by air-conduction and bone-conduction stimuli are dissimilar but the exact mechanisms are still being investigated56.Moreover, the VIS–Flanders project is the first to offer the vestibular screening to all hearing-impaired infants in an entire region, which enables a more representative estimation of aberrant cVEMP results in the overall population of young hearing-impaired children. Recently, the above mentioned study of Verrecchia et al. showed a higher cVEMP abnormality rate of 36.4% in their small subgroup with a sensorineural hearing loss compared to our refer rate of 9.5%47. As already mentioned, this study also focussed on a different target population, including both normal-hearing and hearing-impaired infants. Moreover, the already discussed lower participation rate in this study may imply that parents, who were concerned about vestibular or motor deficiencies in their child, were more likely to participate, which may possibly lead to a higher percentage of vestibular (mainly saccular) dysfunction in the study sample57.In the current study, all cVEMP refers were recorded in infants with a sensorineural hearing loss, as none of the infants with a permanent conductive hearing loss failed the vestibular screening. These findings were in accordance with the results of Sheykholesami et al.59. Concerning the relation with the degree of hearing loss, a significantly higher cVEMP refer rate occurred in infants with severe-profound compared to mild-moderate sensorineural hearing loss in the current study. In line with these results, Verbecque et al. reported higher percentages of deviant cVEMP results in more severely hearing-impaired children across literature21, which can be directly related to the close anatomical and embryological relationship of the cochlea and the otolith organs37.Regarding the relation with the laterality of hearing loss, the current study could not reveal a significantly different cVEMP refer rate in the group with a unilateral and bilateral sensorineural hearing loss, thereby highlighting the necessity of vestibular assessment even in infants with only unilateral hearing loss. These research findings are consistent with previous studies that also detected vestibular dysfunction in children with unilateral sensorineural hearing loss33. As longitudinal and extensive vestibular assessment is currently not feasible on a large scale in clinical practice, the vestibular screening at least ensures an early identification of vestibular (mainly saccular) dysfunction and subsequent motor referral if needed. Furthermore, the VIS–Flanders project increases awareness among parents and caregivers on vestibular dysfunction in hearing-impaired children, and provides information about the limitations of the screening test and the importance of an extensive vestibular assessment if necessary. In the future, it is aimed to more precisely map the predictive factors for vestibular dysfunction, such as the etiology of hearing loss, in a larger sample size of hearing-impaired infants in order to set guidelines to refine the vestibular screening protocol.The first limitation of this vestibular screening protocol is the use of only the cVEMP. As a result, the peripheral vestibular system is not completely evaluated, which may lead to an underestimation of the overall vestibular dysfunction in this population. The second limitation is that the vestibular function is screened only once at the age of 6 months, and in some cases twice if a retest is needed within 3 months. Therefore, children with a progressive or delayed-onset hearing or vestibular deficit will be missed as well. In spite of these two limitations, the VIS–Flanders project makes it possible to offer a basic vestibular screening to hearing-impaired infants on a large scale, as the cVEMP test is a short, objective and child-friendly test of which the equipment is widely availableThe VIS–Flanders project is the first in its kind to implement a standard vestibular screening by means of the cVEMP test for hearing-impaired infants in an entire region. This study showed a 9.5% vestibular screening refer in a representative population of infants with unilateral or bilateral sensorineural hearing loss. This study also showed that the implementation of a vestibular screening programme is feasible, since a participation rate of 86.7% was achieved. In line with previous studies, a significantly higher proportion of infants with unilateral or bilateral severe-profound sensorineural hearing loss failed the vestibular screening compared to those with unilateral or bilateral mild-moderate sensorineural hearing loss (RR = 9.8). Besides the degree of hearing loss, future studies also need to focus on the underlying etiology of hearing loss in order to more precisely map the predictive factors for vestibular dysfunction in this population and to refine the vestibular screening protocol. As this study clearly indicates that a standard vestibular screening in hearing-impaired infants is feasible on a large regional scale, the VIS–Flanders project aims to increase awareness about vestibular dysfunction in hearing-impaired children by setting an example for other regions worldwide.


The mucopolysaccharidoses (MPSs) are lysosomal storage disorders associated with progressive multi-organ and skeletal abnormalities. Clinical manifestations can affect each of the five senses: hearing, vision, smell, taste, and touch.On 24–26 May 2018, 46 specialists with expertise in managing symptoms of MPS and experts specialized in evaluating and managing impairments in each one of the five senses gathered in Lisbon, Portugal at the “MPS & the five senses” meeting to discuss how loss of one or multiple senses can affect activities of daily living (ADL) and quality of life (QoL) in MPS patients and best practices in evaluating and managing the loss of senses in these individuals. The meeting confirmed that MPS can affect the senses considerably, but how these impairments affect ADL and overall QoL from a patient’s perspective remains unclear. A better insight may be achieved by prospectively collecting patient-reported outcome (PRO) data internationally in a standardized way, using a standard battery of tools. To identify relevant PRO tools, a systematic literature review and a selection of existing published questionnaires, focused on adults with no intellectual delay, were performed after the meeting. The search strategy identified 33 PRO tools for hearing, 30 for speech, 125 for vision, 49 for touch (including pain and upper limb function), and 15 for smell/taste. A further selection was made based on several criteria, including applicability/relevance for MPS, applicability in different countries (languages)/cultures, availability in English, ease of use, validation, and normative data, resulting in a final set of 11 tools. In addition to these sense-specific PRO tools, a general QoL tool, the EuroQol (EQ)-5D-5 L, was selected to assess overall QoL and reveal coping behaviors.MPS can affect each of the five senses, but current knowledge on the impact of sense impairments on QoL/ADL in MPS patients remains limited. Collection of data in a standardized fashion using sense-specific patient-reported outcome tools and a general QoL tool may fill the current knowledge gap. The mucopolysaccharidoses (MPSs) comprise a group of lysosomal storage disorders caused by deficiencies in enzymes involved in the catabolism of glycosaminoglycans (GAGs) . PatientThe various clinical manifestations of MPS may considerably affect each of the five senses: hearing, vision, smell, taste, and touch –7. HowevThe “MPS & the five senses” expert meeting was held on 24–26 May 2018 in Lisbon, Portugal to discuss how loss of one or multiple senses can affect ADL and QoL in individuals with MPS, best approaches to evaluate loss of senses using PRO tools, and management of loss of senses in these individuals. A total of 46 specialists with expertise in managing symptoms of MPS and experts specialized in the evaluation and management of impairments in each one of the five senses attended this meeting; four adult patients with MPS testified about their impairments and the impact these impairments have on ADL and QoL.The objectives of the present paper are to provide an overview of the overall findings of the “MPS & the five senses” meeting and to identify the most relevant PRO tools for assessing impairment in the senses and their impact on ADL/QoL in MPS patients.Progressive hearing loss is a common feature of all MPS disorders, and is mainly due to recurrent otitis media, middle ear effusion, ossicle deformity, inner ear (cochlea) abnormalities and alterations in the auditory nerve , 9. WhilBecause of the high prevalence of hearing impairment, regular monitoring for hearing loss in individuals with MPS is important. Hearing-specific questionnaires may be useful to assess the impact of hearing impairment on the patient’s QoL , 15. ManIndividuals with MPS frequently present with ocular manifestations that can result in impaired vision and even blindness , 18. AltVisual impairment and blindness can considerably affect a patient’s independence, mobility, ADL, social interactions, education, work, and overall QoL –21. ReguThere are several clinical manifestations of MPS that may cause impairments in smell and/or taste, i.e. adenoid hypertrophy, chronic rhinosinusitis, recurrent upper respiratory tract infections, thickened nasal cartilages, macroglossia, dental defects , and possibly neurodegenerative disease , 24–26. Olfactory dysfunction may negatively affect one’s appetite, personal hygiene, social relationships, detection of hazardous odors , and ADL (e.g. cooking), and may result in weight loss . TherefoMusculoskeletal disease involving the upper limbs , nerve compression syndromes , and central nervous system changes can result in impaired sensation and function of the upper extremities in MPS patients , 34–36. Impaired sensation or pain and musculoskeletal abnormalities in the upper extremities may significantly affect ADL and self-care, and can lead to limitations in activity and social participation , 42. CTSImpairments in upper extremity function and pain in individuals with MPS can be evaluated using functional tests , and/or PRO tools , 37, 46.Although it is clear that MPS can have a considerable negative impact on each of the five senses, it remains unclear how patients perceive these impairments and how these affect their overall QoL. Literature on this subject is very sparse, and PRO tools for assessing impairments of the senses and their impact on QoL/ADL are generally not part of routine clinical care of MPS patients. A voting round during the MPS & the five senses meeting showed that only a minority of the attendees currently use these kinds of PRO tools in MPS patients in their practice. Nevertheless, PRO tools and physical tests  can complement each other in decision-making for disease management. It is important to make a distinction between health and how patients perceive their health, which depends on how patients are coping with their impairments.A better insight into how MPS affects the senses and how loss in one or more senses affects ADL and overall QoL in patients with this disease can be achieved by prospectively collecting data internationally in a standardized way, using a standard battery of tools. As interactions between the senses are important, all senses should be evaluated. It has been well established that loss in one of the senses can lead to compensatory plasticity and sharpening of other senses . HoAt the MPS & the five senses meeting, there was general agreement that creating new or adapting existing PRO tools specifically for MPS patients is difficult due to the small patient number to test validity of these tools. Instead, existing PRO tools could be useful for evaluating these patients. However, selecting the most appropriate PRO tools for MPS patients is extremely challenging, because of the high number of available tools. The following criteria were perceived most important: 1) applicability to patients with MPS, 2) applicability to different countries (languages) and cultures, 3) ease of use (≤10 min to complete), 4) validation, and 5) availability of normative data.With the above criteria in mind, the experts converged on the use of the five-level EuroQol five-dimensional questionnaire (EQ-5D-5 L) as the recommended general QoL tool to document changes in QoL in patients with MPS . The EQ-After the meeting, a robust EMBASE literature search was performed in June 2018 to identify different PRO questionnaires used in other conditions related to the five senses, that may also be useful in the evaluation of sense impairments and their impact on QoL and/or ADL in MPS patients (Supplementary file 1). The searches were focused on tools for adult patients with no intellectual delay, who are able to complete questionnaires themselves.The search strategy yielded a total of 421 unique hits, and identified a total of 33 tools for hearing, 30 for speech, 125 for vision, 49 for touch (including pain and upper limb function), and 15 for smell and taste. A selection of these PRO tools was made based on several criteria outlined in Supplementary file 1, including applicability/relevance for MPS, applicability in different countries (languages)/cultures, availability in English, ease of use, validation, and normative data. Table MPS can lead to considerable impairments in each of the five senses. However, current knowledge on the impact of sense impairments on QoL/ADL in patients with MPS remains very limited. Further research, i.e. collection of data in a standardized fashion using sense-specific PRO tools (e.g. those summarized in Table Additional file 1. Details of literature search and selection of tools