Pathological conditions in cochlea, such as ototoxicity, acoustic trauma, and age-related cochlear degeneration, induce cell death in the organ of Corti and degeneration of the spiral ganglion neurons (SGNs). Although macrophages play an essential role after cochlear injury, its role in the SGNs is limitedly understood. We analyzed the status of macrophage activation and neuronal damage in the spiral ganglion after kanamycin-induced unilateral hearing loss in mice. The number of ionized calcium-binding adapter molecule 1 (Iba1)-positive macrophages increased 3 days after unilateral kanamycin injection. Macrophages showed larger cell bodies, suggesting activation status. Interestingly, the number of activating transcription factor 3 (ATF3)-positive-neurons, an indicator of early neuronal damage, also increased at the same timing. In the later stages, the number of macrophages decreased, and the cell bodies became smaller, although the number of neuronal deaths increased. To understand their role in neuronal damage, macrophages were depleted via intraperitoneal injection of clodronate liposome 24 h after kanamycin injection. Macrophage depletion decreased the number of ATF3-positive neurons at day 3 and neuronal death at day 28 in the spiral ganglion following kanamycin injection. Our results suggest that suppression of inflammation by clodronate at early timing can protect spiral ganglion damage following cochlear insult. Hearing loss could occur due to various conditions such as administration of ototoxic reagents including aminoglycoside antibiotics, acoustic trauma, infection, and aging2, and interferes with daily communication, which reduces quality of life. Earlier studies have shown that patients with hearing loss experience a higher prevalence of associated adverse health effects than individuals with normal hearing, including social isolation, depression4, and dementia5. Children with hearing loss have reduced educational opportunities including language acquisition and social acquisition6 while adults have a much higher unemployment rate compared with those with normal hearing7. Even single-sided deafness impairs listening abilities including speech perception in background noise and sound localization8.An estimated 1.57 billion  individuals reportedly had hearing loss in 2019, accounting for one in five people (20.3% [19.5–21.1]). Among those, about 25.7% (403.3 million people) had hearing loss that was moderate or higher in severity after adjusting for hearing aid use9. Neuronal cell death in the spiral ganglion prevents restoration of hearing even with cochlear prosthesis. Therefore, preservation of spiral ganglion neurons (SGNs) is crucial for maintaining hearing function during and after pathological situations.The pathology of hearing loss includes initial cochlear damage, hair cell death in the organ of Corti, and subsequent nerve degeneration in spiral ganglion10. Recent studies, however, have revealed that macrophages reside in the different sites of cochlea such as the basilar membrane, osseous spiral lamina, spiral ligament, stria vascularis, and spiral ganglion, and play regulatory roles in the maintenance of cochlear environment11. Furthermore, pathological conditions such as insults targeting hair cells induce migration and accumulation of cochlea-resident, and peripheral macrophages especially in specific areas of cochlea as described above14.In physiological conditions, the inner ear is protected from inflammatory reaction by the cochlea blood-labyrinth barrier, highly specialized capillary networks in the stria vascularis that selectively pass ions, fluids, and nutrients to the cochlea15. Although this classification does not meet all pathological conditions, the regulation of macrophage is important to preserve the function in damaged cochlea. For example, in noise-induced hearing loss mouse model, activation of macrophage was observed in cochlea together with induction of IL-1β, a proinflammatory cytokine, 3–7 days after injury, suggesting M1 inflammatory effect in the cochlea16. In the same model, macrophage depletion using clodronate liposome suppressed hearing loss. Similarly, blockade of IL-6 with anti-IL-6 receptor antibody improved hearing at 4 kHz in noise-damaged mice cochlea, possibly by suppressing inflammatory responses of cochlear macrophages and preserving SGNs17. In an ototoxic injury animal model, expression of fractalkine receptor CX3CR1 on cochlear macrophages has been reported to protect hair cells14.The function of macrophages is generally classified into M1 inflammatory/toxic and M2 anti-inflammatory/tissue repair ones during tissue damage18. In addition, we investigated the effect of macrophage depletion on the hearing and degeneration of SGNs by using clodronate-liposome  were measured at day 7 with a click and four test frequencies  to the left , right  and sham-operated  ears. In the deafened side, ABR thresholds were significantly elevated compared with the contralateral side and with sham-operated ears in response to stimuli at every frequency  staining was next performed to analyze the morphological changes of the cochlea 7 days after kanamycin injection. The organ of Corti from kanamycin-injected mice, but not from sham-operated mice, demonstrated loss of outer and inner hair cells, rupture of the reticular lamina and Corti tunnel, but partial preservation of pillar cells and other supporting cells Fig. b–e. MostHematoxylin–Eosin (HE) staining also revealed that the SGNs were well preserved at day 7, when mice presented significant hearing loss, but were only sparsely observed at day 28 after kanamycin injection Fig. a. Quanti22, and βIII-tubulin (green color), a marker of neurons, were performed using sections derived from sham-operated mice and mice 1, 3, 7, 14 and 28 days after kanamycin-induced unilateral hearing loss  (red color), a marker of damaged neurons at early stagesTo assess the activation status of macrophages in the spiral ganglion after kanamycin injection, immunohistochemistry for ionized calcium-binding adapter molecule 1 (Iba1), a highly conserved cytoplasmic protein commonly used as a microglial marker, was performed. The number of Iba1-positive cells increased and peaked 3 days after kanamycin injection.  were administered at a dose of 3.6 mg clodronate/mouse 24 h after kanamycin injection. Immunohistochemistry revealed that Iba1-positive macrophages were almost not observed 3 days after kanamycin injection  is a hydrophilic molecule that depletes osteoclasts and has been used as a first-generation bisphosphonate to treat osteoporosis with comparatively fewer side effects than traditional treatments16. Although it remains unclear why Corti organ morphology and hearing function were only partially restored by CL in our model, we speculate that hair cell damages occurred rapidly after kanamycin injection into cochlea, so that the effect of CL administered 24 h later was limited to degeneration of SCNs which occurred gradually. Therefore, it may be important to perform CL administration in different timings including several hours after kanamycin injection to see the effect to the hair cells.A previous report demonstrated protection of outer hair cells and preservation of long-term hearing function by CL in a noise-induced hearing loss mouse model29. Kaur et al., have identified critical roles of Fractalkine (CX3CL1)/CX3CR1 signaling between neuron and macrophage for the recruitment of macrophage and protection of SGNs from degeneration30. The discrepancy between their neuroprotective function and our neurotoxic function of macrophage after hair cell damage may suggest the existence of several signaling pathways which determine the protective/toxic fates of macrophage. In this regard, it is noteworthy that ATF3, a transcription factor associated with nerve injury22, was induced almost at the same timing to microglia activation . Intra-tympanic aminoglycoside treatment caused high-frequency hearing loss in XBP1+/- mice and the densities of spiral ganglion cells and synaptic ribbons decreased in that model while sensory cells were preserved. Co-injection of the chemical chaperone tauroursodeoxycholic acid attenuated hearing loss, suggesting that suppressing ER stress in the cochlea could protect the neurons in the spiral ganglion33. Further studies are required to clarify the role of ATF3 in the neuron-macrophage interaction and in the neuroprotective/neurotoxic effect of macrophages after cochlear injury.Regarding the underlying mechanisms, our results suggest a role of neuron-macrophage interaction in the setting of macrophage activation and neurodegeneration in the spiral ganglion after kanamycin administration, as previously reportedalkine CXCL1/CX3CR34 demonstrated that supporting cells in the organ of Corti function as macrophage-like cells, protect adjacent hair cells from pathogens. Similarly, there was a report for the supporting cells to protect hair cells by secreting heat shock protein 70 in ototoxic drug-induced hair cell death model35. Therefore, remaining supporting cells may have a beneficial effect to SGNs and macrophages in the spiral ganglion. Further study is required to clarify this point.Besides neuron-macrophage interaction in the spiral ganglion, we speculate that restoration of the organ of Corti by CL may indirectly improve SGN survival. Hayashi et al.36. Following cochlear implantation, the outcomes of hearing function remains variable. Physiological and anatomical variations have been suggested as factors influencing individual differences37. The number of remaining spiral ganglion cells is also an important factor39. Cochlear implant stimulates residual SGNs, hence remaining SGNs may be linked to better surgical outcomes. Our results suggest that regulation of inflammation in the inner ear could preserve SGNs, thereby improving the hearing outcome following cochlear implantation.In clinical settings, one of the most common and successful surgical approaches for sensorineural deafness is cochlear implantation, which stimulates the auditory nerve directly and transduces sound into neural activityIn conclusion, we observed activation of macrophage almost at the same timing as the initial neuronal damage in SG after unilateral kanamycin injection, suggesting a role of neuron-macrophage interaction in that model. Furthermore, pharmacological depletion of macrophage using CL protected SGNs against degeneration, suggesting a toxic role of macrophage in the same model.40. Mice were socially housed and kept under 12-h dark/light cycle. The relative humidity in the air-conditioned room was maintained at 50–55% and temperature at 21–22 °C. The animals had access to food and water ad libitum throughout the study. All procedures were supervised and approved by the Jichi Medical School Institute of Animal Care and Use Committee (21016-02) and were in accordance with the Japanese Physiological Society’s guidelines for animal care Institutional Review Board and with the ARRIVE guidelines.Male C57BL6/J mice were obtained from Oriental Yeast Co., Ltd.  and used in the study at 7–9 weeks of age. Only male mice were used in this study, because there was a report for the sex difference in the rate and severity of sensorineural hearing loss41. In brief, a small incision was made behind the left ear and the skin was retracted to expose the bulla. A small hole was made in the bulla and 1-μL 30% kanamycin in saline was injected into the cochlea through the round window using a Hamilton syringe. Once kanamycin was injected through the round window, the fascia graft was packed gently around the round window, thus sealing the hole on the round window to prevent the perilymph leaks. Then, the skin overlying the bulla was sutured and the animal was allowed to recover  received kanamycin injection through the round window membrane, as previously describedAnimals were randomly divided into five groups and their ABRs were measured at days 1 (N = 5), 3 (N = 5), 7 (N = 5), 14 (N = 5), and 28 (N = 5) to evaluate changes in the hearing threshold after drug administration. ABR recordings and assessments were analyzed by independent researchers blinded to the procedures. The evoked response signal-processing system  was used for ABR measurement. Animals were anesthetized with intraperitoneal injections of 0.75 mg/kg medetomidine hydrochloride, 4.0 mg/kg midazolam, and 5.0 mg/kg butorphanol tartrate and then placed in a soundproof chamber. ABRs were administered through tone pips and recorded via subcutaneous electrodes placed in the pinna and vertex, with a ground electrode placed in the back near the tail. Click and tone stimuli of 4, 8, 16, and 32 kHz were generated from 100 to 10 dB in 10 dB steps and finally 5 dB intervals near the threshold; average waveforms were generated from 256 responses. The threshold was determined by a single observer who noted the lowest sound level at which a recognizable waveform was recorded on a screen of tracings stacked from highest to lowest sound level. Waveforms were confirmed as auditory-evoked responses by their increased latency and decreased amplitude as the sound intensity of the stimulus decreased.Mice were anesthetized with an intraperitoneal injection of 0.75 mg/kg medetomidine hydrochloride, 4.0 mg/kg midazolam, and 5.0 mg/kg butorphanol tartrate, then transcardially perfused with 0.01 M phosphate buffered saline (PBS) followed by fixation in 4% paraformaldehyde solution. After decapitation, the temporal bones were dissected and the cochleae were fixed in a 4% paraformaldehyde solution overnight, decalcified with 0.12 M Ethylenediamine tetra acetic acid and cryopreserved in 30% sucrose. The cochleae were rinsed in PBS and dehydrated in 70, 80, and 90% ethanol for 15 min, in 100% ethanol for 30 min and 60 min. Clearing was performed twice with xylol for 30 min. The specimens were subsequently immersed three times in liquid paraffin, blocked using solid paraffin in a paraffin case, and incubated at 46–52 °C for 1 day. The tissues were cut into 4-μm-thick sections and then subjected to HE staining.https://imagej.nih.gov/ij/). Histological assessments were analyzed by independent researchers blinded to procedures.For immunohistochemistry, the tissues were cryoprotected in 30% sucrose and sectioned at 10-μm thickness on a horizontal sliding microtome and then processed for immunohistochemistry with ATF3 , Iba1 , and βIII-tubulin . DAPI  was used as nuclear counterstain. Histological observation and image acquisition were conducted using an Olympus BX51 microscope . For quantification, SGNs in basal, middle, and apical turns were discriminated, and the numbers of SGNs were counted per spiral ganglion area using image J software  and 28 days  after the surgery, mice were euthanized by perfusion under anesthesia, and the cochleae were collected for immunohistochemical analysis. ABRs were also measured 28 days after kanamycin injection .Macrophage depletion was induced by CL (N = 16), in which clodronate (18 mg/mL) is encapsulated into liposomes and delivered to the tissues of interests. CL and control (PBS)-encapsulated liposomes were purchased from Hygieia Bioscience  and stored at − 80 °C and until use. We administered 200 μL of CL or control liposome by intraperitoneal injection 24 h after kanamycin injection . This dose was selected based on the recommendation by the manufacturer and previously published literatureStatistical analyses were conducted using SPSS v. 26.0 software . The numbers of surviving SGNs, ATF3-positive neurons and Iba1-positive macrophages in the spiral ganglion were evaluated with a one-way analysis of variance (ANOVA). ABR results and comparative analysis of SGNs between the macrophage-depleted and control groups were evaluated with a two-way ANOVA. The Bonferroni post hoc test was used for comparing the conditions. All values are represented as mean ± SEM. p < 0.05 was considered statistically significant.


Difficulties in performing activities of daily living (ADL) are common in patients with Korsakoff‘s syndrome (KS). The aim of this study was to identify factors associated with ADL dependence in nursing home residents with KS. This exploratory, cross-sectional study included 281 residents with KS from 9 specialized nursing homes in the Netherlands. We examined demographic, cognitive, somatic, and (neuro)psychiatric characteristics. ADL dependence was assessed with the Inter-RAI ADL Hierarchy Scale. Multivariable logistic regression analyses were used to identify factors associated with ADL dependence. Cognitive impairment , female gender , staying in a nursing home for ≥5 years , and impaired awareness  were significantly associated with higher ADL dependence. Chronic obstructive pulmonary disease (COPD) was significantly associated with lower ADL dependence . The model explained 32% of the variance. The results suggest that when choosing interventions aimed at improving ADL functioning, special attention should be paid to residents living more than five years in the nursing home, with a female gender, with more severe cognitive impairments, and/or with COPD. Korsakoff’s syndrome (KS) is a neuropsychiatric disorder caused by severe thiamine deficiency, predominantly in the context of alcohol abuse and malnutrition . There aThe various physical and cognitive problems in KS have a major impact on the ability to carry out activities of daily living (ADL) ,10. ADL ADL independence leads to a slower decline in mobility and improved quality of life, as well as improved emotional well-being and improved cognitive functioning; finally, encouraging autonomy in ADL tasks can reduce challenging behavior in the elderly and those with dementia ,13,14,15Despite the obvious positive effects of encouraging ADL independence, research also shows that most nursing home residents spend their days inactive and are more dependent in their ADL tasks . This hiSeveral studies in elderly care have investigated predictors and factors associated with ADL dependence. Muscle mass, strength, and physical performance were found to be predictors for future ADL dependence ,20. CareAs far as we know, no research is performed that focuses on factors that are associated with ADL dependence in residents with KS. This study, therefore, aims to explore a wide range of factors across many domains to examine which factors are associated with ADL dependence in nursing home residents with KS and other alcohol-related disorders.This explorative, cross-sectional observational study used the dataset of the previously conducted exploratory descriptive study called the “Korsakov Study”, collected between 2014 and 2016. The “Korsakoff Study” examined the prevalence and severity of neuropsychiatric symptoms in patients with KS living in Dutch nursing homes .In total, 281 residents with KS from 9 specialized nursing homes, ranging from 7 to 82 participants per nursing home, were included in the initial “Korsakoff-Study”. Due to the heterogeneous nature of the terminology, the term KS is used in this study as an umbrella term to describe the Dutch KS nursing home population in its full scope. All participating nursing homes provide specialized care to KS residents and participate in the “Dutch Korsakoff Knowledge Centre (KKC)”. Details on enrollment, procedures, and results of the study have been previously described . Study iADL dependence was assessed with the Activities of Daily Living Hierarchy Scale of the interRAI-LTCF (ADL-H). This scale measures performance on four self-care tasks  and was found to be reliable and valid for use in home care and mental care ,23. The Everyday cognitive performance was measured with the validated InterRAI Cognitive Performance Scale (CPS) . The CPSAwareness of functional deficits was assessed with the Patient Competency Rating Scale (PCRS). The PCRS includes both a self-rating list and an informant rating list. The participant judged his/her own ability to complete several everyday tasks, and this was compared to the ratings of the first responsible nurse or nursing assistant. The discrepancy between the participant’s and nurse’s ratings represents the level of self-awareness .Neuropsychiatric symptoms (NPS) were assessed using the Neuropsychiatric Inventory Questionnaire (NPI-Q). The presence of NPS (yes/no) and their severity  were determined. The severity of NPS is expressed as a sum score. The NPI-Q is a short questionnaire derived from the more comprehensive Neuropsychiatric Inventory (NPI)  and is a2 and AIC. For the significant variables (p ≤ 0.05) in the models we calculated odds ratios (OR). For the statistical analysis, the package “Stats” in R-Statistics 4.0.4 was used.We dichotomized the main outcome measure ADL-H according to the degree of ADL dependence at the two cut-off points and used two prespecified full logistic regression models to examine the factors associated with ADL dependence. The “main model” used a cut-off point similar to that used in the original “Korsakoff-Study”, and the “sensitivity analysis model” used a cut-off point similar to that considered clinically relevant. From both models, we reported the outcomes: regression coefficients, confidence intervals, and significance levels and model performance measures: Nagelkerke RAll subjects gave their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki and approved by the Institutional Review Board of the Amsterdam UMC (WC 2014-010 on 30 January 2014) and considered not subject to the Dutch Medical Research Involving Human Subjects Act. Data were stored at Amsterdam UMC and were only accessible through a secured network environment.The sociodemographic and clinical characteristics are reported in The group distribution according to the initial ADL-H cut-off point in the main model resulted in an unequal distribution of participants in both groups, namely 72 impaired participants (26%) vs. 209 (74%) independent or supervised participants. All characteristics were more prevalent in the ADL-impaired group, except COPD (24% vs. 30%) and personality disorders (10% vs. 11%). The minority of the participants were female (22%) and they were 8% more impaired than males. Lowering the cut-off point on the ADL-H used in the sensitivity analysis increased the size of the ADL-supervised/dependent group: n = 182 (65%), versus the ADL-independent group of n = 99 (35%).β = 2.01, p = 0.002, followed by gender β = 1.17, p = 0.02, and five or more years of residing in a nursing home β = 1.13, p = 0.02. The presence of COPD showed a negative association with ADL functioning β = 1.19, p = 0.03. After sensitivity analysis, severe cognitive impairment remained significant: β = 1.89, p = 0.001. Gender and length of admission were no longer found to be significant. Moderate cognitive impairment β = 1.15, p = 0.003, and severe impaired awareness β = 1.45, p = 0.005, were also significantly associated with ADL dependence, contrary to the main model.In the main multivariable logistic model, significant associations were found for four variables . ParticiOR were calculated for the significant variables of both models . The maiThis study examined demographic and clinical characteristics associated with ADL dependence in nursing home residents with KS and other alcohol-related disorders. The results of this study indicated a strong association between severe cognitive impairment and ADL dependence. Both the main model and the sensitivity analysis indicated that the odds of ADL dependence increase by factors of 7.5 and 6.6, respectively, when the resident is severely cognitively impaired. Length of stay in a nursing home as well as female gender were found to increase the odds of ADL dependence by factors of 3.1 and 3.2, respectively. Surprisingly, COPD was found to be significantly associated with decreased ADL dependence (OR = 0.3). The association with COPD was no longer found to be significant in the sensitivity analysis. However, the sensitivity analysis showed a significant association (OR = 4.3) between level of awareness and ADL dependence. No significant associations were found with age, use of psychotropic drugs, psychiatric disorder, or NPS in both models. Both models explained 32% of the variance in ADL dependence, leaving 68% unexplained.The strong association between ADL dependence and cognitive impairment we found supports and extends the previous literature reporting similar findings ,31,32,33Surprisingly, age was not found to be significantly associated with ADL dependence, unlike residing more than 5 years in a nursing home. This rather contradictory result suggests that older patients with KS may still be ADL independent, but younger patients who are institutionalized for a longer period may become ADL dependent at some point. It is known that as a result of a long-term stay in a nursing home, institutionalized behavior can occur, such as taking less initiative and thinking less creatively. Residents are increasingly adapting to their environment and becoming less self-reliant ,36. InstIn contrast to other studies, which found that ADL dependence is significantly correlated to general and disease-specific health status in patients with advanced COPD , we founIt is also somewhat surprising that in our study we found a significant association between female gender and increased ADL dependence, since in previous studies regarding factors associated with ADL dependence, “gender” was not found to be significantly associated. Yet these studies were conducted on community-dwelling elderly, patients with dementia, and elderly care ,20,21,31Factors associated with ADL dependence have been studied more extensively in nursing home residents with dementia. These studies reported that apathy is a strong predictor of ADL dependence . ContrarThis study used a large study sample from nine specialized nursing homes spread across the Netherlands . The samFindings of our study may help professional caregivers to better understand the potential risk of becoming ADL-dependent and to choose interventions with the aim to prevent further deterioration in ADL, minimize disability, improve patients’ independence, and delay institutionalization as long as possible ,44. GiveThis nationwide study aimed to identify factors associated with ADL dependence in patients with KS living in nursing homes. Based on the analysis, it can be concluded that several physical and cognitive factors are associated with ADL dependence. The results suggest that when choosing interventions aimed at improving ADL functioning, special attention should be paid to residents living more than five years in the nursing home, with female gender, with more severe cognitive impairments, and/or with COPD. Future research should identify which specific cognitive functions most affect ADL functioning and how functional status and cognitive impairment can be reliably and validly measured in KS. Finally, further research is needed to assess the role of institutionalization and its impact on ADL independence.


An MRI is potentially hazardous for patients with retained ferromagnetic bullets. Recent studies have aimed to develop dual-energy computed tomography (DECT) as a screening tool for recognising highly ferromagnetic bullets. Inconsistent findings have been ascribed to inherent CT technology differences. Previous research demonstrated significant Hounsfield unit (HU) measurement variation among single-source CT machines.This study investigated the theoretical dual-energy index (DEI) variation between DECT machines when evaluating the potential ferromagnetic properties within the same sample of ex vivo bullets and metal phantoms.An experimental ex vivo study was conducted on eight metal phantoms and 10 unused bullets individually positioned in the same Perspex head phantom and scanned on two DECT machines. Two senior radiology registrars independently recorded the HU readings, and DEI values were calculated. Statistical analysis was performed using non-parametric methods for paired data, namely the Signed Rank Test. The DEI values based on mean HU readings between the DECT machines were compared.Inter- and intra-reader agreement was not statistically significant. The metal phantoms had poor interscanner agreement, with an overlap of the ferromagnetic and non-ferromagnetic ranges. The bullets had good interscanner agreement, with a similar ferromagnetic to non-ferromagnetic relationship.The use of DEI values negates the previous assumption that significant interscanner variability exists among different DECT technologies while assessing highly attenuative ex vivo bullets.This investigation demonstrated that even though HU readings may be variable, the implementation of the DEI equation translates this into comparable values with good interscanner agreement. According to the South African crime statistics released for 2019–2020, firearm violence resulted in 7351 murders  and 12 718 attempted murder cases . Firearms were further implicated as the main tool of intimidation in most other crime categories and established relations with multiple murders.3 Recent research highlighted gunshot wounds as a leading cause of spinal cord injuries, mostly involving younger males. Patients experienced a higher rate of adverse medical complications and morbidity, often required surgery, and had prolonged hospital admissions.4Law enforcement and criminal interactions are not the only source of gunshot injuries, as these may also occur during sport and hunting. Non-fatal gunshot injuries are widespread, and as a result, penetrating trauma makes up a large portion of the trauma population requiring medical care.5Continuous advances and improvements in emergency medical care and technology will likely decrease trauma fatalities. It can reasonably be concluded that secondary evaluation techniques and residual lesion identification will become increasingly important as patients require further and definitive care.6 A recent study found that only highly ferromagnetic bullets can potentially shift in vivo position within MRI magnetic fields and that most bullets are non-ferromagnetic.5 It was concluded that bullet migration within the static magnetic field is minimal and related to the shape and orientation of the bullet.7 It was further shown that the potential ferromagnetic heating effect does not appear significant.8 This indicates that MRI might not be an absolute contraindication if the bullet (and composition) is known.5 Highly ferromagnetic bullets cause large amounts of MRI susceptibility artefacts, which degrade image quality and thus reduce clinical relevance.5An MRI was previously deemed an absolute contraindication for patients with retained bullets, especially if these were close to vital structures. The main concerns are the potential hazards of in vivo position shift and the heating effect of the bullet within the MRI magnetic field. A recent investigation found that ferromagnetic MRI-related incidents are underreported and that there is a definite desire among radiology staff to broaden and advance the knowledge base and culture regarding the safety aspects of ferromagnetic materials related to MRI investigations.9The Shellock MRI safety list is an invaluable resource if the bullet in question is known. Unfortunately, the current list of bullets is very limited and mostly rated for 1.5 Tesla (T) MRI fields. Clinical 3T and 7T MRI machines are becoming more widely utilised and the increased magnetic fields may elicit different or more dramatic interactions.10 quantify coronary calcification,11 contrast agent uptake measurements,12 ventilation-perfusion assessment with Xenon gas,13 and discriminate intracranial haemorrhage from contrast medium.14Dual-energy computed tomography (DECT) has in recent years demonstrated its ability to characterise urinary calculi,15 There are no minimum or maximum limitations to the Hounsfield scale.16Materials composed of different elemental compositions may produce very similar Hounsfield units (HUs) at a given energy, which significantly complicates the differentiation and classification of such materials. Each voxel’s HU represents a linear attenuation coefficient, which is not unique to any given material but rather a function of the material’s composition, its photon energy interaction and its mass density.15 This was initially explored and described by Godfrey Hounsfield, who stated in 1973, ‘Two pictures are taken of the same slice, one at 100 keV and the other at 140 keV … so that areas of high atomic numbers can be enhanced’.17 Alvarez and Macovski further investigated DECT in 197617 and demonstrated that even with polyenergetic X-ray spectra, one could still separate the measured attenuation coefficients into their contributions from the principal forms of photon interaction with matter, namely photoelectric effect and Compton scatter.18The DECT can be defined as the use of attenuation measurements acquired with different energy spectra, in addition to the known changes in attenuation between those spectra, to differentiate and quantify material composition.19 and identified a potential relationship between a bullet’s ferromagnetic properties and dual-energy index (DEI) value. The DECT has been proven superior to single-source CT while attempting to differentiate between high-density materials because of acquiring data sets at different X-ray beam energies.20Forensic medicine studies have found DECT capable of differentiating between commonly found foreign materials,Bullets are made of a variety of materials. Traditionally, bullet cores contain lead, or an antimony-lead alloy, while bullet jackets are made of copper or gilding metal . Various materials are commonly used in modern bullets, including bismuth, aluminium, bronze, copper, steel, tin, tungsten, plastics and rubber.21 Bullet characterisation with clinical CT machines has multiple obstacles pertaining to both artefact generation  and reconstruction algorithms.22 The cupping artefact encountered with metals is a subcategory of beam hardening and scatter, leading to misinterpreting the obtained image as a representation of the bullet jacket and core. The ‘core’ portion of the bullet image is a combination of high attenuation and photon starvation, whereas the ‘jacket’ portion is the outer layer composed of scatter artefacts.23The different high-density metals that constitute bullets might be discernible with industrial CT equipment (> 320 kV), but the radiation doses are not compatible with clinical applications in healthcare.25 The end goal is to determine MRI safety in patients with retained bullets, especially when close to vital structures. Most of these studies have identified a potential relationship, although the results have been inconsistent.Recent studies have aimed to combine DECT with the extended HU scale (EHUS) to discriminate between highly ferromagnetic and non-ferromagnetic bullets.27 These studies demonstrated that highly ferromagnetic and non-ferromagnetic bullet DEI numbers clustered together within respected, although inconsistent, ranges.27 Interscanner variability has not been evaluated among different DECT machines utilising DEI values.A commonly identified limiting factor has been CT technology differences. The CT machine manufacturer has been constant, but models and machine service ages differed.The purpose of this study was to investigate the theoretical DEI variation between different DECT machines while evaluating the potential ferromagnetic properties within the same sample of ex vivo bullets and metal phantoms.This experimental ex vivo study comparatively examined metal phantoms and bullets on two different DECT machines. Eight solid rod metal phantoms  were investigated, representing the wide range of metals used in bullet production. The solid rods were bright bar steel, dark bar steel, tungsten, stainless steel, brass, lead, aluminium and copper. The copper rod was excluded from the study after the MRI testing, as it demonstrated strong magnetism and thus represented an alloy rather than pure copper.Ten unused bullets of various calibres were examined . The mai28 These were air rifle projectiles, shotgun pellets, paintballs and BB gun pellets.According to suggestions from previous research, some ballistic projectile categories were excluded from the study because of size, composition, and CT spatial resolution restrictions.29 The projectiles and metal phantoms were individually suspended on a string in front of a marked non-ferrous vertical board at the portal of an MRI machine , and the deflection angles from vertical were documented. Torque value investigation was not performed, as previous studies have indicated a linear relation between deflection angle and torque propensity.24Empirical ferromagnetic testing for each bullet and metal phantom was performed according to methods described in multiple previous studies concerning the deflection angle.Three metal phantoms were non-ferrous, three demonstrated marked ferromagnetic properties, and one had intermediate ferromagnetic properties. The copper metal phantom was found to be a ferromagnetic copper alloy and was excluded from further testing.Five bullets were non-ferromagnetic, one demonstrated mild ferromagnetic properties, and four were markedly ferromagnetic. Two ferromagnetic bullets had a larger deflection angle (exceeding 90°) compared with the ferromagnetic metal phantoms.A realistic and reproducible study environment was achieved using a Perspex head phantom (large cylinder 16 cm diameter) while evaluating all metal phantoms and bullets. A central cylindrical cavity within the Perspex phantom enabled a reproducible perpendicular central placement of metal phantoms and bullets within the CT machine gantries.The metal phantoms and bullets were individually scanned on two different single-source DECT machines, which varied in manufacturer, production date, operational time, software and post-processing capabilities:General Electric CT Discovery 750 HD 64-slice installed at Universitas Academic Hospital, Clinical Imaging Sciences Department (December 2011). Acquisition and processing were performed on the accompanying workstation (AW Volume share 4). Data collection was carried out on AGFA PACS because of technical limitations on the AW Volume share workstation.Siemens Healthcare Somatom Definition AS+ 128-slice installed at Pelonomi Academic Hospital, Clinical Imaging Sciences Department (December 2020). Acquisition and processing were performed on the AW. Data collection was performed on the Syngo.via workstation.The Siemens Somatom CT scanner allowed the EHUS (−10 240 to +30 710) activation during reconstruction. The GE Discovery required a complete system restart after activating the EHUS function, following which the EHUS was continuously active till manually deactivated.26: tube voltage 100 kV and 140 kV, exposure 400 mAs, rotation time 0.5 s, pitch 0.6, slice collimation 2 mm × 64 mm × 0.6 mm, slice acquisition 2 mm × 64 mm × 0.6 mm. Reconstruction was on a sharp tissue kernel with EHUS activated. Slice thickness was 1.5 mm on the Siemens Somatom and 1.25 mm on the GE Discovery. Both were set to 1 mm increments.26Temporal sequential scanning of the entire scan volume was performed with tube strength at 100 kV and 140 kV on each metal phantom and projectile to allow for similar machine settings. This approach was used because the dual-energy programme settings did not allow for individual tube setting alterations, nor did the Siemens Somatom allow activation of the EHUS within the dual-energy programmes. Metal phantoms and bullets were scanned with the following parameters30 was central, without incorporating the edge, and covering more than one pixel. Two sets of readings were obtained per bullet and examination, at least five slices apart. The HU readings were recorded for mean, maximum, minimum and standard deviation (s.d.). The region of interest (ROI) placementTwo independent senior radiology registrars performed all the readings, one of whom was blinded to the ferromagnetic testing. Metal phantoms and bullets were allocated a specific description used throughout the investigation period. To evaluate intra-reader agreement, a second round of scans and readings were performed on the bullets 2–4 weeks after the initial scans.26:The DECT data were reconstructed and measured using an EHUS at two different energy levels. These readings were then converted to a DEI value using a standard equationFor the low kV, the EHUS reading was at 100 kV and the high kV at 140 kV.The DEI was calculated for all measured HU readings . The mean HU readings and the corresponding DEI values were submitted for statistical analyses and used for further interpretation.Descriptive statistics, namely frequencies and percentages for categorical data and medians and percentiles for numerical data, per type of bullet and metal phantom, were calculated. As a result of the small sample sizes, the bootstrap methodology was not appropriate; therefore, the bullet types were compared by means of non-parametric methods. Inter- and intra-rater reliabilities were calculated and described by means of non-parametric methods for paired data, namely the Signed Rank Test. Intraclass correlations (ICC) using the Shrout-Fleiss formula were calculated. The analysis was performed by the Department of Biostatistics, Faculty of the Health Sciences, University of the Free State.Ethical approval to conduct the study was obtained from the University of the Free State Health Sciences Research Ethics Committee (HSREC) and permission to conduct the study at a state hospital was obtained from the Free State Department of Health . No consent was required in this study.p-values: ICC for ROI1 = 0.65:0.90900, ROI2 = 1.00:0.92990, ROI3 = 0.64:0.86502, ROI4 = 0.19:−0.00536) and the GE Discovery had good p-values with poor ICC .31 The poor ICCs were negative and correlated with a wider s.d. on the GE Discovery. The metal phantoms demonstrated a wide p-value range and excellent ICC on the Siemens Somatom , but poor ICC for the GE Discovery ,31 which had a statistically significant variation on the second ROI readings obtained on the GE Discovery.Inter-reader agreement for the mean DEI values was not statistically significant. The Siemens Somatom had excellent ICC , and GE Discovery . The proposed reason for the smaller p-values on the GE Discovery is likely because of the wider s.d. range obtained for the mean ROIs. The metal phantoms demonstrated reduced intra-reader agreement with Investigator 2 (R2) obtaining higher p-values on both Siemens Somatom  and GE Discovery . Investigator 1 (R1) obtained statistically significant ROI readings on the Siemens Somatom.Intra-reader agreement was not statistically significant for the bullets’ mean DEI values between the two radiology registrars (R1 and R2) with similar Metal phantoms  were useMetal phantom DEI values for both investigators were within similar ranges . Further analysis of the DEI values demonstrated that the ferromagnetic metals’ DEI ranges were centrally located within the non-ferromagnetic ranges, which is different from previous studies. The average DEI values for the ferromagnetic and non-ferromagnetic metals differed slightly .Metal phantom DEI values for both investigators were once more within similar ranges, although R2 obtained a narrower range . Further analysis of the DEI values demonstrated that the ferromagnetic metals’ DEI ranges were within the upper half of non-ferromagnetic ranges, which is different from previous studies. The average DEI values for the ferromagnetic and non-ferromagnetic metals differed more pronounced . Investigator 1 (R1) had a single significant outlier point (−0.1992), which significantly decreased the average DEI value for the ferromagnetic metals.The HU measurements  were obtThe bullet mean DEI values of both investigators had wider ranges compared with the metal phantoms . Further analysis of the DEI values demonstrated that the ferromagnetic bullet DEI ranges were within the non-ferromagnetic ranges, which was different from previous studies. The average DEI values for the ferromagnetic and non-ferromagnetic bullets differed more significantly than the metal phantoms . The non-ferromagnetic bullets had more pronounced positive outlier DEI values, which increased the average DEI values.The bullet mean DEI values of both investigators were once more within similar ranges . Further analysis of the DEI values demonstrated that the ferromagnetic bullet DEI ranges were within the non-ferromagnetic ranges, which was different from previous studies. The average DEI values for the ferromagnetic and non-ferromagnetic bullets differed more pronounced . The non-ferromagnetic bullets had more pronounced positive outlier DEI values, which increased the average DEI values.30This study aimed to investigate the proposed interscanner variability described as a limiting factor in previous literature pertaining to DECT as a screening tool for ferromagnetic ballistic projectiles because of previous inconsistent findings.30 demonstrated a considerable HU variability between different CT machines, except for brass, which was found to completely attenuate X-ray beams and thought to obscure the differences observed with other materials. Ruder et al.30 also showed that DECT-capable machines had the lowest HU readings among the researched CT machines, although dual-energy was not utilised. The researchers used 80 kV tube voltage and a fixed tube current time product of 130 mAs. These settings were a practical decision because of the CT machine limitations, as 80 kV was the only tube voltage available on all the machines.30 Paulis et al.23 concluded that higher tube voltages and current time products reduce artefact influences on material differentiation, following which they recommended 150 kV tube voltage and 400 mAs exposure.Ruder et al.30 holds for single-source HU readings, and the current investigation also had variable individual HU readings among the studied DECT machines. However, the use of DEI values was found to be more consistent between the investigated DECT readings. The DEI values are functions of the HU readings and require different energy levels to calculate, which has the result that the CT technology differences are negated. It can be deduced that the CT technology differences affecting the low kV readings, similarly, influence the high kV readings and that this is annulled during the DEI value calculation.The conclusion of Ruder et al.20 concluded that DECT was more reliable at differentiating materials than single-energy CT. They found that the optimal tube voltage combination was 100 kV/140 kV, although exposure was adjusted to produce constant radiation doses. Diallo et al.26 used the same scan parameters and CT manufacturers, although the models differed (Somatom Definition Flash vs Somatom AS+). Both studies identified a DEI difference between ferromagnetic and non-ferromagnetic bullets, although the relations were opposite. Multiple other research studies30 have been conducted using Siemens models, which do not account for the proposed inter-manufacturer variability. The reason for the variability among results has been ascribed to individual machine differences.Winklhofer et al.Our investigation was conducted with two completely different DECT machines, which currently appears to be the only study to utilise other manufacturers. We believe the machines represent a broad enough CT technology variation to represent the proposed limitations previously identified in the tabled articles. Our research advances the literature by evaluating this previously suggested interscanner variability.The machines had variable DEI ranges for the metal phantoms , with co26 and the opposite to Winklhofer et al.30 The current findings demonstrate a more pronounced overlap of DEI values while comparing ferromagnetic to non-ferromagnetic bullets, whereas previous studies had a more pronounced difference with less overlap.The bullets  had a muDespite these variations with previous similar research, the main objective of this investigation was to assess variability between different DECT machines. The average bullet DEI values were comparable between the machines . Furthermore, even the average ferromagnetic  and non-ferromagnetic  bullet DEI values were comparable and within close proximity to each other. The average DEI values give a false impression of a wide difference between ferromagnetic and non-ferromagnetic values, as the ranges largely overlap. Significant outlier values for the non-ferromagnetic bullets increase the average DEI values, however, the outlier DEI values are similar between the DECT scanners.20 Core readings were used for DEI value calculation and analysis, as the ‘jackets’ have previously been shown to be unhelpful.23 Undamaged unused bullets were used, and optimally placed within the centre of the gantries at perpendicular angles to the X-ray beams. This was done to limit projectile variables and test the research question in isolation. We are aware that bullets will orientate randomly and deform upon impact, and the position related to the gantry and surrounding structures may be different in real life situations. The metal phantom and bullet samples were small; however, we believe that these were sufficiently representative. Larger metal phantom and projectile samples may have increased statistical relevance, although larger studies have been conducted on single machines. Finally, ex vivo analysis is still under investigation and not yet applicable to emergency radiology. Further research and agreement are required before implementation on the living should be considered.This research investigation had a couple of limitations worth mentioning and may require future study. Small projectiles and fragments were excluded based on CT spatial resolution limitations.In conclusion, the use of DEI values negates the previous assumption that significant interscanner variability exists among different DECT technologies while assessing highly attenuative ex vivo ballistic projectiles. Previous research indicated that different HU measurements are obtained with different CT machines, but this has not yet been reassessed on DECT machines utilising DEI values. This investigation has demonstrated that even though HU readings may be variable, the implementation of the DEI equation translates this into comparable values with good interscanner agreement.Future research on DECT implementation for MRI safety prediction related to bullets should use DEI as a reference rather than HU only.


Untreated hearing loss is a significant public health issue affecting the quality of life of millions of Americans. Barriers to treatment invite novel and innovation solutions, but as these solutions create new treatment delivery models, they also may—purposefully or accidentally—challenge the values of the field.Value-sensitive design methodology is used in this study to identify the values in current hearing health care service delivery. We performed qualitative content analysis of questionnaires, clinical practice guidelines, and professional ethics documents that represent the intended and enacted values in audiology.The result is a comprehensive list of values that can be used as a structured codebook for systematic textual analysis of materials representing current best practices in the provision of hearing health care services. A secondary result is an analysis of the relative importance of values in audiology, inferred from the frequency of references to each value.Subjective benefit, professional duties, and self-efficacy were the core values identified in the current provision of audiologic care, and these values should be central to considerations for new hearing health care models and technologies. Hearing loss is a serious public health problem that affects an estimated two thirds of adults over the age of 70 years . In the Despite the high prevalence of hearing loss and its associated negative effects, significant disparities exist in treatment. Few people who could benefit from treatment seek it; less than 30% of adults over 70 years old who would benefit from a hearing aid report using one , and theThere is a long history of research exploring reasons behind the apparent preference for nonuse of hearing aids among candidates for amplification. Commonly cited differences between cohorts of hearing aid users and nonusers include degree of hearing loss, personal feelings about hearing aid use, ability to pay the cost of devices and associated treatment, comfort with wearing and using devices, expectations about outcomes, and social support . More reThe PCAST and NASEM reports proposed an over-the-counter (OTC) hearing aid model as a solution. In 2017, legislation was passed that introduced a new class of amplification devices to be sold directly from manufacturer to consumer . While OTC is likely to address issues of cost and access related to devices, its implementation could also represent a shift away from the professional rehabilitative services associated with audiology and successful hearing aid outcomes. Remote service delivery (teleaudiology) is another solution that has been widely implemented to improve access to care. Teleaudiology can increase access to crucial services for vulnerable populations that experience barriers to attending clinic appointments . TeleaudThere is a need to compare different solutions in terms of their capability to help underserved individuals overcome barriers to treatment. With a better understanding of the differences in competing models, we might mitigate unintended consequences that could negatively affect patients and consumers. This study analyzed traditional, clinical audiology to identify what is considered important in the current dominant model of hearing health care service delivery. Specifically, this study aimed to evaluate hearing health care as it pertains to the epidemic of untreated hearing loss. According to the Value-sensitive design (VSD) is an approach used to describe, consider, evaluate, or proactively design for social values supported by a technology, product, or service , 2013. Fwhat values are and where they can be found , and codes of ethics. Questionnaires represent A three-step qualitative content analysis approach was used to create a comprehensive list of the values in hearing health care. Our research goals guided our choice of qualitative research design and techniques . We adapStep 1: Identify source material representing the intended and enacted values in hearing health care. We collected textual documents that describe the provision of audiological services for American adult patients who could benefit from treatment in the form of amplification devices or aural rehabilitation services. A literature review was conducted to collect potential questionnaires representing enacted values in the provision of audiological services. The electronic database PubMed/MEDLINE and the search engine Google Scholar were used for searches of questionnaires addressing adults with hearing difficulty or hearing aids. Databases were searched for peer-reviewed articles containing outcome questionnaire batteries for hearing health care services published between 1960 and 2020 using the search term “outcome assessment” in conjunction with each of the following terms: “hearing aid,” “audiology,” “hearing,” “aural rehabilitation,” and “communication.” The search was conducted in August 2020 and updated in February 2021. Questionnaires were included in the study if they were published between January 1960 and January 2020, were written in English, and contained a complete corpus of outcome questions. Questionnaires were excluded if they were published prior to January 1960, were written in a language other than English, or did not contain outcome-related questions. In total, the search generated 43 hits. After questionnaires that did not meet the inclusion criteria were excluded, a total of 24 questionnaires were chosen for analysis. Another literature review was conducted to collect CPGs. CPGs exist for various services; however, we targeted those addressing treatment of adult patients with hearing aids. To collect relevant CPGs, we conducted “hand searches” of professional organization websites relevant to audiology. Key professional organizations included the American Academy of Audiology (AAA), the American Speech-Language-Hearing Association (ASHA), The Independent Hearing Aid Fitting Forum, and the Audiology Practice Standards Organization. One code of ethics was obtained from each of the websites of these four professional organizations, with the exception of AAA where two CPGs were elicited. To collect relevant codes of ethics, we conducted another hand search of professional organization websites relevant to audiology. Key professional organizations included AAA, the Academy of Doctors of Audiology, ASHA, and the National Board for Certification in Hearing Instrument Sciences. One code of ethics document was obtained from each of the websites of these four professional organizations. Our final corpus included a total of 33 relevant documents to be analyzed for values. We collected five CPGs, four codes of ethics, and 24 questionnaires  and that these values should be central to considerations in the design of new hearing health care models. At the same time, professional duties currently dominate attention to moral values in the field. If the role of professionals is reduced in future hearing health care delivery models, the field must grapple with how best to preserve attention to moral values. Audiology is a gatekeeping model of health care, where access to treatment (hearing aids) is controlled and limited by those with a professional degree. The emphasis on self-efficacy identified here is consistent with a shift in hearing health care toward empowering adults with perceived difficulty hearing to pursue solutions without the involvement of a health care provider. An OTC model, for example, prioritizes the core value of self-efficacy but would likely de-emphasize the value of professional duties. The identification of key audiology values is the first step toward evaluating the benefits and limitations of alternative service delivery models. By establishing the list of values and their relative importance in traditional audiology, we can evaluate how they are facilitated by current and future products and services.intended and enacted values in hearing health care for American adults. It is possible that the documents chosen for this study do not encompass all aspects of hearing health care and that the analysis of additional documents in Step 3 could have produced values that were not captured in our corpus. However, the fact that all codebook values were found in the chosen CPGs is evidence that we would not find new values by including additional CPGs (There are limitations associated with the use of a directed content analysis approach. Using theory to guide the coding process could bias researchers, potentially leading to overly supportive evidence and blinding researchers to contextual aspects of a phenomenon . The infnal CPGs .The purpose of this study was to capture information about core values in audiology as a starting point in the process of using VSD to improve the treatment of hearing loss. The codebook developed in this project was used to capture and interpret information about the values currently prioritized in audiology and can serve as a template to assess the values inherent to hearing health care service delivery. As teleaudiology, OTC, and other hearing health care service delivery models are adopted, this codebook can be used to ensure that important values are preserved or that a shift in values is enacted intentionally to overcome current barriers to treatment. In future work, we hope to guide the development and implementation of innovative solutions that address untreated hearing loss using the codebook presented here.A comprehensive list of values representing the field of audiology was obtained using qualitative content analysis. Subjective benefit, professional duties, and self-efficacy were the core values identified in the current provision of audiologic care. VSD has the potential to address barriers to the access and use of hearing health care services that have been identified under the traditional model of audiology. A comprehensive codebook of values is a useful tool for the critical analysis of the shifting regulations, products, and services of hearing health care in the United States.The data sets generated and/or analyzed during this study are available from the corresponding author on reasonable request.


This study aimed to evaluate the effects of hyperbaric oxygen therapy (HBOT) on the hearing recovery of patients with idiopathic sudden sensorineural hearing loss (ISSNHL). The clinical data of 79 patients diagnosed with ISSNHL and treated with HBOT between January 2017 and December 2019 were retrospectively reviewed. The pure tone audiometry (PTA) scores before and after HBOT were recorded. The associations of HBOT efficacy with demographic and clinical characteristics and the duration from disease onset to HBOT administration were determined. The average PTA score was 80.06 ± 25.94 dB before and 60.75 ± 21.26 dB after HBOT; the difference was significant. HBOT improved the hearing of 55.7% of the patients with ISSNHL . There was a significant inverse relationship between the duration from symptom onset to HBOT administration and PTA score reduction after HBOT, which was adjusted for factors including age, sex, laterality of hearing loss, initial PTA score, reception of intratympanic steroid injections, tinnitus, dizziness, vertigo, diabetes, hypertension, and coronary artery disease. Commencing HBOT at an earlier stage is closely linked to greater improvements in hearing for patients with ISSNHL. Idiopathic sudden sensorineural hearing loss (ISSNHL) is characterized by a sudden onset of hearing impairment, typically exceeding 30 decibels (dB) over three consecutive frequencies within 72 h. It is not fatal, but it significantly impairs the quality of life of affected individuals. The annual incidence of ISSNHL ranges from 5 to 27 per 100,000 individuals, with approximately 66,000 new cases reported in the United States alone .The pathogenesis of ISSNHL has been debated, and several mechanisms have been suggested . In addiHyperbaric oxygen therapy (HBOT) is a widely recognized and accepted medical intervention. It involves the controlled inhalation of pure oxygen within a pressurized environment, typically exceeding 1.4 absolute atmospheric pressure. This treatment significantly elevates the concentration of oxygen in the bloodstream, enhancing its efficient transportation to tissues. It achieves this by surpassing levels achievable through normal respiration, thanks to increased dissolved oxygen concentration in plasma, a phenomenon governed by Henry’s law, which stipulates that the amount of diffused gas in a liquid is directly proportional to its partial pressure above the liquid.During HBOT, transcutaneous oxygen pressure measurements often demonstrate improved tissue oxygenation ,10,11. TISSNHL has been investigated as a potential indication for HBOT since the 1970s, guided by the hypothesis that HBOT can alleviate cochlear hypoxia ,11. BesiIn our daily practice, we have observed that the chances of hearing loss recovery in patients with ISSNHL increase when they receive HBOT at an earlier stage from the onset of symptoms. However, the question arises: what constitutes ‘early’ in this context, and does the timing of HBOT indeed influence the recovery rate? Additionally, we have noted instances where patients with ISSNHL were referred for HBOT evaluation as a salvage therapy only after other treatment modalities had failed to improve hearing loss for a duration of four weeks or longer from symptom onset. Unfortunately, our clinical observations suggest limited benefits in such cases.To bridge this knowledge gap, we initiated a retrospective study to investigate the potential impact of the timing of HBOT on the prognosis of patients with ISSNHL. Our objective was to validate our hypothesis: that earlier administration of HBOT would lead to more significant improvements in hearing recovery.This retrospective study analyzed the data of patients diagnosed with SSNHL who received HBOT at the Far Eastern Memorial Hospital (FEMH) between 2017 and 2019. The inclusion criteria for this study involved selecting patients aged 20 years or older, diagnosed with ISSNHL, and who received HBOT at FEMH. The exclusion criteria for this study included age of <20 years, known hearing loss etiology, bilateral or previous ipsilateral hearing loss, HBOT initiation beyond 180 days after symptom onset, insufficient follow-up data for pure-tone audiometry (PTA), fewer than three HBOT sessions, and lack of audiogram data beyond one week after the initial HBOT session. A cohort of 79 patients who satisfied the inclusion criteria was included in the analysis. Along with HBOT, most patients  received steroid treatments, such as systemic steroids  or ITSIs, in otorhinolaryngology clinics. Ethical approval was obtained from the Far Eastern Memorial Hospital Ethics Committee . Informed consent is waived under FEMH Ethnics Committee agreement due to the observational nature of the investigation. No new interventions or interactions with patients are involved, as the data has already been collected for clinical purposes. Additionally, the retrospective design ensures that patient identities remain anonymized, and confidentiality is maintained throughout the research process.The therapy center at the FEMH used the HAUX Starmed 2200 hyperbaric chamber, manufactured by Haux-Life-Support GmbH in Karlsbad, Germany, for HBOT administration. Each HBOT session was conducted at a pressure of 2.5 absolute atmospheres and lasted for 120 min. This protocol comprises a 15-min descent time, a 90-min bottom time, and a 15-min ascent time. Patients received pure oxygen during the bottom and ascent phases, with two 5-min air breaks during the bottom phase to mitigate the risk of oxygen toxicity, and the last 3 min of the ascent phase also involved a switch to air. Each session’s duration of pure oxygen breathing is estimated to be 92 min. The treatment sessions were conducted daily. Ten to 20 HBOT sessions have been recommended by previous studies, but the actual number of sessions varied for each patient based on their needs and response to treatment.PTA was used to evaluate hearing improvement in individuals presenting with ISSNHL symptoms. PTA scores in decibels (dB) were determined for the frequencies of 250, 500, 1000, 2000 and 4000 Hz. The average PTA score was calculated and is reported in this study. The initial PTA score was determined based on the most recent audiogram obtained before HBOT initiation. The outcomes were recorded following the completion of the HBOT sessions. In this study, the overall improvement was defined as an average PTA improvement exceeding 10 dB or a final average PTA score below 29 dB.The main aim of this retrospective study was to examine the correlations between the efficacy of HBOT and various factors. These factors included the duration from the onset of symptoms to the initiation of HBOT, demographic characteristics, clinical features , and use of systemic corticosteroids or ITSIs.t-test or Wilcoxon signed-rank test was used to compare the pre-and post-HBOT continuous data.The Kolmogorov-Smirnov test was used to assess the normality of the numerical data. Normally distributed data are expressed as mean ± standard deviation, whereas non-normally-distributed data are represented as medians . Categorical data were presented as frequencies and percentages. The paired-sample To investigate the differences in hearing improvement across various durations from symptom onset to HBOT, a combination of one-way ANOVA/Welch and post-hoc Games-Howell analyses were conducted. Univariate and multivariate linear regression were used to assess the impact of the duration from symptom onset to HBOT on hearing improvement while considering other covariates.p < 0.05. All statistical analyses were performed using SPSS software version 22.0 .The threshold for determining statistical significance was set at The study enrolled 79 participants. p < 0.001).p < 0.001) (Linear regression showed an inverse correlation between the duration from symptom onset to the initiation of HBOT and the reduction in PTA score (ΔPTA) after HBOT  . Comparep < 0.001), even subsequent to meticulous adjustment for these aforementioned variables (delineated in Incorporating a multivariate linear regression analysis, we accounted for several potential variables that could potentially influence the observed improvement. These encompassed factors such as age, sex, laterality of hearing loss, initial PTA score, receipt of ITSI, as well as coexisting conditions including tinnitus, dizziness, vertigo, diabetes, hypertension, and coronary artery disease. The analysis revealed a noteworthy correlation between the efficacy of HBOT and the time elapsed from the onset of symptoms to the commencement of treatment (Beta = −0.296, In these 79 patients with idiopathic sudden sensorineural hearing loss and receiving HBOT, the most common complication is eardrum barotrauma, whose severity is often mild and self-limited. They did not experience CNS toxicity during HBOT.The primary objective of this retrospective study was to establish the ideal timing for initiating HBOT in patients diagnosed with ISSNHL. To achieve this, we examined the influence of the timing of HBOT initiation on hearing improvement. Our findings revealed a significant negative correlation between the duration from symptom onset to the commencement of HBOT and the magnitude of improvement in the PTA score. These results strongly indicate that initiating HBOT earlier is associated with greater hearing improvement in patients with ISSNHL. Notably, this observation is a novel contribution to the existing literature.The pathophysiology of ISSNHL is closely related to the condition of the inner ear . In a syGoto et al.  observedOur study also revealed a significant positive correlation between the severity of initial hearing loss and improvement in PTA scores. Individuals with more severe hearing loss at baseline may experience marked benefits from HBOT. In another retrospective study by Ajduk et al., significant improvements in hearing thresholds were observed across all frequencies for patients with hearing loss exceeding 61 dB who received salvage HBOT after failed steroid treatment for ISSNHL .Most patients in our study received systemic corticosteroids within one week of experiencing ISSNHL symptoms. Therefore, recovery from hearing impairment in our study was not affected by the duration from symptom onset to the administration of systemic steroids.Based on our observations, ITSIs had no significant impact on hearing improvement in patients diagnosed with ISSNHL receiving HBOT. A meta-analysis conducted by Sialakis et al.  also indComorbidities such as diabetes mellitus, hypertension, and coronary artery disease did not have a significant effect on the overall improvement in hearing loss in patients with ISSNHL. This implies that individuals with these comorbidities may benefit from HBOT as a viable treatment option for ISSNHL.We obtained audiograms within 180 days from the onset of ISSNHL to monitor changes in the PTA scores. Based on our patient data, we observed that hearing changes tended to stabilize approximately one month after ISSNHL onset. Moon et al.  suggesteSeveral other studies have explored the optimal timing of HBOT for ISSNHL . We believe our study adds a valuable contribution to the existing literature for several compelling reasons:1. **Novel Inverse Relationship**: Our study distinguishes itself by being among the few to elucidate an inverse relationship between the duration of receiving HBOT from the onset of symptoms and the improvement of hearing loss. Unlike most papers on this topic that simply identify specific time windows, we delve into the dynamic relationship between timing and outcomes.2. **Comparable Patient Numbers**: Our study ensures comparability by maintaining similar patient numbers across different durations. This approach strengthens the validity of our comparisons regarding the effects of treatment duration.3. **Clinical Realism**: We acknowledge the clinical reality where some patients turn to HBOT as a salvage therapy after other treatments have failed. Drawing from our observations, we advocate for early HBOT intervention, as we have noticed that delays in treatment initiation may result in less favorable outcomes.These distinctive features of our study enrich the current body of literature on HBOT for ISSNHL, providing valuable insights for both researchers and clinicians.This study had several limitations primarily attributed to its retrospective design and relatively small sample size. Additionally, the treatment regimens, including systemic corticosteroids and ITSIs, administered to each patient were not standardized but based on individualized assessments. This may have influenced the outcomes of the study. To validate these findings, further studies involving larger samples and more rigorous study designs are required.This study underscores the critical role of the timing of HBOT initiation in determining the prognosis of patients with ISSNHL. Our findings strongly support the notion that commencing HBOT at an earlier stage is closely linked to greater improvements in hearing for patients with ISSNHL. This discovery holds substantial implications for clinical decision-making, emphasizing the importance of early HBOT administration as an integral part of the treatment for ISSNHL, rather than solely as a last-resort salvage therapy following unsuccessful attempts with other treatment modalities. Future prospective studies with larger sample sizes are warranted to validate these results and gain deeper insights into the therapeutic advantages of HBOT in ISSNHL.


Gene therapy for hearing loss: from mechanism to clinic” encompasses 11 manuscripts on the topic of gene therapy for sensorineural hearing loss, inner ear development regulation and clinical surgery treatment.As the most prevalent sensory disorder, hearing loss causes patients a great deal of hardship and leads to a number of psychological and mental disorders. Such as the elderly individuals with presbycusis will causing social isolation, depressive symptoms and mild cognitive impairment. In addition, the cochlear hair cell loss and the degradation of auditory cortex are typical pathological alterations that lead to presbycusis. As pathological changes occur during the process of hearing loss, cognitive abilities and sound perception can be affected by lesions in the cochlea, auditory nerve, or auditory center. The common factors that can cause sensorineural hearing loss include genetic factors, medicines, infections, diseases, trauma, age, and the environment. With in-depth investigation of the pathophysiology of hearing disorders and enhancement of diagnosis and treatment technologies, gene therapy in hearing regeneration is gradually attracting our interest and is a future exploration direction. Gene therapy is a novel approach to preventing hair cell death, promoting hair cell regeneration and regulating the expression of genes associated with deafness. Remarkable advances have been made in gene therapy for hearing loss, but there are still many obstacles to overcome. New technologies and material applications will help us better understand the process of hearing loss and optimize the impact of gene therapy to restore auditory function. This Frontiers Research Topic entitled “Hou et al. conducted a series of experiments using an FGF22 knockout mouse model (Fgf22−/−) to explore the relationship between the Fgf22 gene and synaptic defects in HHL. The authors found that Fgf22−/− mice had lower wave I amplitudes at 8 and 16 kHz than Fgf22+/+ mice. However, the numbers of inner hair cells and ribbon synapses in Fgf22−/− mice was not significantly different from those in Fgf22+/+ mice. The authors found that FGF22 deletion may cause calcium channels to be more easily activated and cause Ca2+-triggered exocytosis in response to stimuli. The real-time PCR results showed that the synaptic vesicle-related proteins SNAP-25 and Gipc3 were significantly decreased in Fgf22−/− mice, which may affect the function of IHC ribbon synapses and induce HHL.In the cochlea, inner ear cells are in charge of receiving acoustic signals and transmitting auditory information to the brain. Ribbon synapses can facilitate the conveying of signals to the appropriate spiral ganglion neurons by inner ear cells. However, hidden hearing loss (HHL) caused by ribbon synapse loss is usually ignored, and the mechanisms underlying ribbon synapse loss are largely unknown. Wu et al. devoted much work to the protective role of pitavastatin (PTV), a new-generation lipophilic statin, on neomycin-induced hair cell loss. In in-vitro experiments, PTV protected not only HEI-OC1 cells but also cochlear explant cultures from hair cell damage caused by neomycin. In a mouse model, pretreatment with intraperitoneal injection of PTV prevented neomycin-induced hearing loss and hair cell damage. The authors further explored the mechanism underlying the protective effect of PTV and found that PTV could inhibit neomycin-induced apoptosis and ES under neomycin stimulation. In addition, PTV could inhibit PERK/eIF2α/ATF4 signaling to attenuate ER stress and inhibit the Rho/ROCK signaling pathway to protect against neomycin-induced ototoxicity.Endoplasmic reticulum (ER) stress is well-investigated in aminoglycoside-induced hearing loss, and ER stress inhibition exhibits a protective effect on aminoglycoside-induced ototoxicity. Chen P. et al. reviewed the pathological mechanisms of connexin-26 (Cx26)-related hearing loss. Members of the Cx family play important roles in the cochlea, as these proteins can form gap junctions, which maintain the balance of ion and substance exchange between cells. The authors summarized two types of Cx26 transgenic mice, congenital deafness and late-onset progressive deafness model mice, and described the different pathological changes of these two models. Cxs are crucial for gap junction (GJ) combination, and Cx26 mutation disrupts the GJ system, which maintains stable endocochlear potential. The authors further explored the hypothesis that Cx26 deficiency causes cochlear potassium recycling dysfunction and put forth his own perspective. Furthermore, the authors discussed the crucial regulatory functions of Cx26 in the Ca2+ signaling pathway throughout the development of the inner ear. GJs play an important role in energy supply and glucose transport in the inner ear during development and hair cell (HC) survival. Mutations in Cx26 cause energy supply limitations and lead to Corti development disorder, OHC function decline and hearing failure.Fei et al. introduced semicircular canal occlusion (SCO) to the treatment of vertigo in clinical and related basic research. SCO was initially applied to treat benign paroxysmal positional vertigo (BPPV). Later, semicircular canal fistula and Meniere's disease were also treated with SCO. The vertigo of most patients with Meniere's disease is controlled vertigo after SCO. The efficiency and safety of TSCO in the ear with endolymphatic hydrops were confirmed in animal models. Some patients with refractory BVVP who undergo posterior SCO show complete resolution of positional vertigo after long-term follow-up. However, some patients experience short-term hearing loss, which can recover within 6 months. Superior SCO is an ideal operation for treating superior semicircular canal dehiscence syndrome and has a low incidence of complications. Although the vertigo of most patients who undergo SCO is alleviated, there are still a few reports of hearing deterioration after SCO. Hence, further exploration is needed to determine the effect of SCO on hearing and vestibular function.Chen Z.-R. et al. tested the efficiency and safety profiles of cotransduced dual-AAV vectors in the vestibular sensory epithelium of mice. First, mixtures of dual-AAV-ie vectors with CGA or CMV promoters were injected into the adult and neonatal mouse inner ear. Compared with adult mice, the cotransduction rates in the striolar and extrastriolar region hair cells were significantly higher in neonatal mice. After diphtheria toxin administration to damage the utricle HCs, the authors found that the cotransduction rate increased in striolar and extrastriolar region HCs compared with those of control adult mice. Three months after dual-AAV-ie vector transduction, mouse auditory and vestibular functions were tested, and no significant effects were observed. The cotransduction efficiency was also maintained for 3 months in adult mice. This study provided a feasible safety profile for future gene therapies through the cotransduction of dual-AAV vectors into the vestibule.Adeno-associated virus (AAV) is a widely used vector for gene therapy in animal models and clinical trials. However, due to its packaging capacity, AAV cannot deliver a large gene or multiple genes. Therefore, a procedure for the cotransduction of dual-AAV vectors has been developed to solve these problems. Ma et al. reviewed 53 GPCRs expressed in the cochlea and offered a new GPCR-based medication development strategy for hearing loss therapy. In the manuscript, class A, class B2, class C and class F GPCRs in the cochlea and their functions are described. With the development of structural analysis, researchers have designed several GPCR structure-oriented drugs that target the complicated structure of GPCRs. With the exploration of cochlear gene therapy and GPCR-related gene therapy drugs that are applied in the treatment of other organ diseases, it is hoped that inner ear-oriented GPCR-related drugs will emerge in the near future.G protein-coupled receptors (GPCRs) are the largest superfamily of mammalian cell surface receptors, and some of them are related to hearing disorders. Song et al. observed IHC ribbon synapse changes from P1-P28, and the data showed that the number of synapses undergoing pruning was accompanied by the activation and migration of macrophages. The expression of CX3CR1 was significantly associated with macrophage activation, and the expression level was increased at P7 and gradually decreased thereafter. Moreover, consecutive injection of a CX3CR1 inhibitor for 7 days after P7 showed that synapse pruning was affected, with impaired hearing in adulthood. Spiral neurons secreted CX3CL1 to recruit migrating macrophages at postnatal day 7. Exogenous supplementation with CX3CL1 activated synapse pruning and reduced the number of IHC ribbon synapses, and hearing was also impaired at P28. These results indicate that ribbon synaptic remodeling by macrophages via the CX3CL1/CX3CR1 axis occurs postnatally in mice prior to the onset of hearing and that this remodeling is essential for the development of hearing.Cochlear ribbon synapse maturation in postnatal mice requires morphological and functional modifications. Chen J. et al. reviewed the morphological changes, biological functions and potential mechanisms for HC regeneration in KO. The structure of KO-SCs folds, cell gaps widen, and columnar cell numbers decrease and are replaced by cuboidal-like cells during maturation. The rhythmic morphological changes may be triggered by the intracellular Ca2+ concentration and contractile protein activation. Spontaneous ATP and Ca2+ release from KO-SCs is crucial for cochlear development, and KO-SCs secrete glycoproteins for tectorial membrane formation. Chen J. et al. also described the regulatory role of the apoptosis pathway, thyroid hormone signaling and autophagy in KO-SC programmed degeneration. Through the regulation of a variety of transcription factors and signaling pathways, KO-SCs can be a source of progenitor cells for hair cell regeneration in the early postnatal period, providing opportunities for the treatment of hearing disorders in the future.As a transient cellular cluster structure, Kölliker's organ (KO) plays a crucial role in cochlear development and degenerates during cochlear maturation. Meng et al. compared the changes in vestibular function and hearing after different semicircular canal surgery techniques were performed for labyrinthine fistula treatment. In Group 1, the labyrinthine fistula was only partially covered with simple fascia when dexamethasone injection was administered. In Group 2, the labyrinthine fistula was capped with a “sandwich” composed of fascia, bone meal, and fascia. After surgery, several Group 1 patients experienced vertigo symptoms. The patients in Group 2 with type II labyrinthine fistulas showed short-term vertigo symptoms after surgery but no occurrences of vertigo during a long-term follow-up. For the patients with type I labyrinthine fistulas, there was no significant difference between bone conduction (BC) and air conduction (AC) thresholds or the A-B gap after surgery. However, for patients with type II labyrinthine fistulas, the recovery of the A-B gap in Group 2 was poorer than that in Group 1, but there was a significant recovery in hearing compared to preoperative hearing.Mu et al. explored FOXG1-related epigenetic modifications that affect HC survival in cisplatin treatment. The expression of FOXG1 and the autophagy pathway were initially activated in both in vivo and in vitro models after cisplatin administration, and the expression decreased at high doses of cisplatin treatment. Subsequently, the authors found that the inhibition of FOXG1 and the autophagy pathway might be regulated by H3K9 methylation. Pretreatment with BIX01294, a G9a inhibitor that could transiently and reversibly inhibit H3K9me2 activity, reverse the inhibition of FOXG1 and autophagy and alleviate the HC damage and hearing loss induced by cisplatin. Interestingly, the authors also found that FOXG1 and H3K9me2 could affect the activation of the autophagy pathway by regulating autophagy-related miRNAs and affecting the ROS levels and apoptosis ratio changes in OC1 cells after cisplatin treatment.Sun et al. provided a review of recent research progress in the role and regulation of autophagy and ferroptosis in the inner ear. As an important physiological process for metabolic waste degradation and reuse, autophagy plays a key role in maintaining normal cellular functions. In the auditory system, autophagy activation mostly promotes HC survival, such as in aging, ototoxic drug use and noise-related hearing loss. The autophagy pathway is regulated by many factors and signals, and this pathway needs to be further explored for deafness prevention. The authors also described ferroptosis regulation mechanisms in the auditory system and demonstrated that the prevention of ferroptosis activation had a protective effect on HCs during ototoxic drug exposure and aging-induced auditory cortex degeneration. Ferritinophagy, autophagy-induced ferroptosis, has recently attracted much attention from many researchers. Ferritinophagy is a kind of selective autophagy process that is mediated by NCOA4. NCOA4 induces the binding of autophagosomes and ferritin, and free Fe2+ increases with the degradation of ferritin and induces ferroptosis in cells. More studies are needed to clarify the mechanisms of ferritinophagy in the auditory system.For this Research Topic, research on inner ear hair cell protection, ribbon synapses and organ of Corti development regulation and clinical middle ear surgery was collected. The content of this Research Topic includes recent research progress in the auditory system and the latest inner ear gene therapy methods and thus could provide a reference for further exploration of auditory disorders.SZ and ZH participated in writing the manuscript. ZH, SZ, WL, YS, and QZ participated in reviewing the manuscript. All authors contributed to the article and approved the submitted version.