Effect of shock wave power spectrum on the inner ear pathophysiology in blast-induced hearing loss.

Blast exposure can induce various types of hearing impairment, including permanent hearing loss, tinnitus, and hyperacusis. Herein, we conducted a detailed investigation of the cochlear pathophysiology in blast-induced hearing loss in mice using two blasts with different characteristics: a low-frequency dominant blast generated by a shock tube and a high-frequency dominant shock wave generated by laser irradiation (laser-induced shock wave). The pattern of sensorineural hearing loss (SNHL) was low-frequency- and high-frequency-dominant in response to the low- and high-frequency blasts, respectively. Pathological examination revealed that cochlear synaptopathy was the most frequent cochlear pathology after blast exposure, which involved synapse loss in the inner hair cells without hair cell loss, depending on the power spectrum of the blast. This pathological change completely reflected the physiological analysis of wave I amplitude using auditory brainstem responses. Stereociliary bundle disruption in the outer hair cells was also dependent on the blast's power spectrum. Therefore, we demonstrated that the dominant frequency of the blast power spectrum was the principal factor determining the region of cochlear damage. We believe that the presenting models would be valuable both in blast research and the investigation of various types of hearing loss whose pathogenesis involves cochlear synaptopathy.

Melatonin reduces radiation damage in inner ear.

The purpose of this study was to use a murine model to determine if melatonin can protect the inner ear from radiation-induced damage. A total of 81 4-week-old Balb/c mice were randomly divided into five groups: control group; 50 mg/kg melatonin group; 5 mg/kg melatonin+radiotherapy group; 50 mg/kg melatonin+radiotherapy group; radiotherapy group. The radiotherapy groups received 16 Gy irradiation and melatonin was administered by intraperitoneal injection 30 min before radiotherapy. On days 3 and 7 after irradiation the function of outer hair cells was determined by auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs) testing, pathological changes of inner ear cells were observed by light microscopy, and the expression of prestin mRNA was determined. ABR thresholds were increased and wave I latencies were extended after radiotherapy; however, the increases were lower in the groups that received melatonin (P < 0.05). DPOAEs showed radiotherapy-induced hearing loss at 8-12 kHz, and hearing loss was greater on day 7 than day 3. However, hearing loss was less in the melatonin groups (P < 0.05). Histopathological examination showed irradiation resulted in breaks and distortion of the cochlear basement membrane, disruption of the stria vascularis, and swelling of outer hair cells. Melatonin reduced these changes. Radiotherapy upregulated prestin mRNA expression. Radiotherapy-induced upregulation of prestin was decreased in the melatonin groups (P < 0.05), and the decrease was greater in the 50 mg/kg melatonin group (P < 0.05). Melatonin protects against radiation-induced cochlear damage by reducing damage to outer hair cells.

A unique radioprotective effect of resolvin E1 reduces irradiation-induced damage to the inner ear by inhibiting the inflammatory response.

BACKGROUND: In addition to the direct effects of irradiation, the induced inflammatory response may play an important role in the damage to the inner ear caused by radiotherapy for the treatment of head and neck cancers. Resolvin E1 (RvE1) has anti-inflammatory activity, acting by reducing neutrophil infiltration and proinflammatory cytokine expression. Therefore, in this study we sought to confirm whether the inflammation induced by irradiation was involved in damage to the inner ear after radiotherapy and to investigate the protective effect and underlying mechanism of RvE1 using mouse models. METHODS: A dose of RvE1 was delivered by intraperitoneal injection to mice before irradiation. Changes in the auditory brainstem response (ABR), relative balance ability, inner ear morphology and the expression levels of inflammatory factors in the inner ear were analyzed on days 7 and 14 after irradiation and compared among different experimental groups. RESULTS: Changes of ABR and relative balance ability showed the inner functions of experimental mice presented severe damage after irradiation, but the damage was significantly alleviated after RvE1 pretreatment compared to irradiation alone. Morphological analysis of the inner ear showed severe damage to the cochlea and vestibule after irradiation. In contrast, damage to the cochlea and vestibule was significantly reduced in the RvE1-pretreated group compared to that in the irradiation alone group. Along with these functional and morphological changes, the mRNA expression level of anti-inflammatory factors interleukin-2 was significantly increased, while those of proinflammatory factors interleukin-6 and tumor necrosis factor-α were significantly decreased in the inner ear of mice after RvE1 pretreatment compared to irradiation alone. CONCLUSIONS: We believe that inflammation induced by irradiation is involved in the damage to the inner ear caused by radiotherapy, and that RvE1 reduces the damage caused by irradiation to the inner ear by regulating the induced inflammatory response.

Generalized model of the microwave auditory effect.

A generalized theoretical model for evaluating the amplitudes of the sound waves generated in a spherical head model, which is irradiated by microwave pulses, is developed. The thermoelastic equation of motion is solved for a spherically symmetric heating pattern of arbitrary form. For previously treated heating patterns that are peaked at the sphere centre, the results reduce to those presented before. The generalized model is applied to the case in which the microwave absorption is concentrated near the sphere surface. It is found that, for equal average specific absorption rates, the sound intensity generated by a surface localized heating pattern is comparable to that generated by a heating pattern that is peaked at the centre. The dependence of the induced sound pressure on the shape of the microwave pulse is explored. Another theoretical extension, to the case of repeated pulses, is developed and applied to the interpretation of existing experimental data on the dependence of the human hearing effect threshold on the pulse repetition frequency.

Dosimetric evaluation of four whole brain radiation therapy approaches with hippocampus and inner ear avoidance and simultaneous integrated boost for limited brain metastases.

AIMS: To perform a dosimetric evaluation of four different simultaneous integrated boost whole brain radiotherapy modalities with hippocampus and inner ear avoidance in the treatment of limited brain metastases. METHODS: Computed tomography/magnetic resonance imaging data of 10 patients with limited (1-5) brain metastases were used to replan step-and-shoot intensity-modulated radiotherapy (sIMRT), dynamic intensity-modulated radiation therapy (dIMRT), volumetric-modulated arc therapy (VMAT), and helical tomotherapy (Tomo). The prescribed doses of 40-50 Gy in 10 fractions and 30 Gy in 10 fractions were simultaneously delivered to the metastatic lesions and the whole-brain volume, respectively. The hippocampal dose met the RTOG 0933 criteria for hippocampal avoidance (Dmax ≤17 Gy, D100% ≤10 Gy). The inner ear dose was restrained to Dmean ≤15 Gy. Target coverage (TC), homogeneity index (HI), conformity index (CI), maximum dose (Dmax), minimum dose (Dmin) and dose to organs at risk (OARs) were compared. RESULTS: All plans met the indicated dose restrictions. The mean percentage of planning target volume of metastases (PTVmets) coverage ranged from 97.1 to 99.4%. For planning target volume of brain (PTVbrain), Tomo provided the lowest average D2% (37.5 ± 2.8 Gy), the highest average D98% (25.2 ± 2.0 Gy), and the best TC (92.6% ± 2.1%) and CI (0.79 ± 0.06). The two fixed gantry IMRT modalities (step and shot, dynamic) provided similar PTVbrain dose homogeneity (both 0.76). Significant differences across the four approaches were observed for the maximum and minimum doses to the hippocampus and the maximum doses to the eyes, lens and optic nerves. CONCLUSION: All four radiotherapy modalities produced acceptable treatment plans with good avoidance of the hippocampus and inner ear. Tomo obtained satisfactory PTVbrain coverage and the best homogeneity index. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03414944 . Registered 29 January 2018.

[Effect of melatonin on expression of Prestin protein in the inner ear of mice following radiotherapy].

Objective: To investigate the effect of melatonin on the expression of prestin protein in the inner ear of mice following a single dose radiation therapy, so as to provide the basis for the mechanism study of radiation induced inner ear injury and its prevention. Methods: Sixty 4-week-old male mice were randomly divided into six groups, including the control group (A group), 50 mg/kg MLT group (B group), 5 mg/kg MLT group (C group), 50 mg/kg MLT + radiotherapy group (D group), 5 mg/kg MLT+ radiotherapy group (E group), and 16 Gy radiotherapy group (F group). Each experimental group was randomly subdivided into two subgroups, which were killed to harvest the cochlea on the 3rd and 7th days following 16 Gy radiation. The specimens were used for immunostaining and Western blot to detect the expression of prestin protein. SPSS 19.0 software was used for statistical analysis. Results: Prestin protein mainly distributed in the lateral membrane above the outer hair cell nucleus. When compared with A, B and C group, the expression of prestin protein in the inner ear was significantly up-regulated in F group (P<0.05). However, D and E group reduced the abnormal expression of prestin following radiotherapy when compared with F group, the difference was statistically significant (P<0.05), and the effect of D group was more significant than E group (P<0.05). Conclusions: The prestin protein of cochlea is mainly distributed in the lateral membrane above the outer hair cell nucleus. Following the high-dose radiotherapy, the prestin expression is upregulated, and melatonin can control the abnormal expression of prestin protein induced by radiotherapy with dose dependent.

Ototoxicity after radiotherapy for head and neck tumors.

PURPOSE: To investigate the incidence of radiation-induced ototoxicity according to the total dose delivered to specific parts of the auditory system, fractionation, and chemotherapy. METHODS AND MATERIALS: Records of 325 patients treated for primary extracranial head and neck tumors with curative intent who received radiotherapy between 1964 and 2000 (median follow-up, 5.4 years) were retrospectively reviewed. Reconstructions of the treatment plans were generated to estimate the doses received by components of the auditory system. RESULTS: Radiotherapy-induced morbidity developed in 41.8% of patients (external ear, 33.2%; middle ear, 28.6%; and inner ear, 26.8%). Univariate/multivariate analyses indicate that total dose received by parts of the auditory system seem to be significant, though fractionation and chemoradiation may contribute to the incidence of ototoxicities. Sensorineural hearing loss (SNHL) was observed in 49 patients (15.1%). Univariate and multivariate analyses indicated that age (p = 0.0177 and p = 0.005) and dose to cochlea (p < 0.0001 and p < 0.0001) were significant, and chemoradiation (p = 0.0281 and p = 0.006) may increase the incidence of SNHL. Five-year and 10-year actuarial risk of clinically overt SNHL increased to 37% (p > 0.0001) above doses of 60.5 Gy compared to 3% at doses below 60.5 Gy. For patients treated with adjuvant chemotherapy, clinically overt SNHL increased to 30% compared to 18% in the no-chemotherapy group at 10 years (p = 0.0281). CONCLUSION: Radiotherapy toxicity was observed in all parts of the auditory system with median doses for incidence varying between 60 Gy to 66 Gy. Total dose to organ seems to be a significant factor though fractionation and chemo-radiation may contribute to ototoxicities.

High-resolution numerical model of the middle and inner ear for a detailed analysis of radio frequency absorption.

In order to enable a detailed analysis of radio frequency (RF) absorption in the human middle and inner ear organs, a numerical model of these organs was developed at a spatial resolution of 0.1 mm, based on a real human tissue sample. The dielectric properties of the liquids (perilymph and endolymph) inside the bony labyrinth were measured on samples of ten freshly deceased humans. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-3700 MHz were carried out. For typical output power values of real handheld mobile communication devices the obtained results showed only very small amounts of absorbed RF power in the middle and inner ear organs. Highest absorption in the middle and inner ear was found for the 400 MHz irradiation. In this case, the RF power absorbed inside the labyrinth and the vestibulocochlear nerve was as low as 166 microW and 12 microW, respectively, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power were found to be more than one order of magnitude lower than the values given above. These results indicate that temperature-related biologically relevant effects on the middle and inner ear, induced by the RF emissions of typical handheld mobile communication devices, are unlikely.

Modeling of the internal fields distribution in human inner hearing system exposed to 900 and 1800 MHz.

This paper investigates the internal electric and magnetic field distribution and the specific absorption rate (SAR) values in a magnetic resonance imaging-based model of the inner hearing system exposed to 900 and 1800 MHz. The internal fields distributions were calculated using the Finite Integration Technique. The estimation of the field values was evaluated along lines passing through that target organ, specifically from the vestibular to the cochlear region and from the apex to the base of the cochlea. The specific findings are: 1) higher internal fields strength and SAR value in the vestibular region rather than in the auditory region, especially for the inner ear closer to the external source; 2) higher internal fields strength in the basal and apical region of the cochlea than in the middle one; 3) local differences in the internal fields distribution and SAR value, comparing the head models including or not the inner auditory system model; 4) results' variability evaluated by changing the head-source mutual position and the dielectric properties of the inner hearing system.

Radio frequency-induced temperature elevations in the human head considering small anatomical structures.

In order to enable a detailed numerical radio frequency (RF) dosimetry and the computations of RF-induced temperature elevations, high-resolution (0.1 mm) numerical models of the human eye, the inner ear organs and the pineal gland were developed and inserted into a commercially available head model. As radiation sources, generic models of handsets at 400, 900 and 1850 MHz operating in close proximity to the head were considered. The results, obtained by finite-difference time domain-based computations, showed a highly heterogeneous specific absorption rate (SAR) distribution and SAR-peaks inside the inner ear structures; however, the corresponding RF-induced temperature elevations were well below 0.1 degrees C, when considering typical output power values of handheld devices. In case of frontal exposure, with the radiation sources approximately 2.5 cm in front of the closed eye, maximum temperature elevations in the eye in the range of approximately 0.2-0.6 degrees C were found for typical device output powers. A reduction in tissue perfusion mainly affected the maximum RF-induced temperature elevation of tissues deep inside the head. Similarly, worst-case considerations regarding pulsed irradiation affected temperature elevations in deep tissue significantly more than in superficial tissues.

Contribution of bone marrow hematopoietic stem cells to adult mouse inner ear: mesenchymal cells and fibrocytes.

Bone marrow (BM)-derived stem cells have shown plasticity with a capacity to differentiate into a variety of specialized cells. To test the hypothesis that some cells in the inner ear are derived from BM, we transplanted either isolated whole BM cells or clonally expanded hematopoietic stem cells (HSCs) prepared from transgenic mice expressing enhanced green fluorescent protein (EGFP) into irradiated adult mice. Isolated GFP(+) BM cells were also transplanted into conditioned newborn mice derived from pregnant mice injected with busulfan (which ablates HSCs in the newborns). Quantification of GFP(+) cells was performed 3-20 months after transplant. GFP(+) cells were found in the inner ear with all transplant conditions. They were most abundant within the spiral ligament but were also found in other locations normally occupied by fibrocytes and mesenchymal cells. No GFP(+) neurons or hair cells were observed in inner ears of transplanted mice. Dual immunofluorescence assays demonstrated that most of the GFP(+) cells were negative for CD45, a macrophage and hematopoietic cell marker. A portion of the GFP(+) cells in the spiral ligament expressed immunoreactive Na, K-ATPase, or the Na-K-Cl transporter (NKCC), proteins used as markers for specialized ion transport fibrocytes. Phenotypic studies indicated that the GFP(+) cells did not arise from fusion of donor cells with endogenous cells. This study provides the first evidence for the origin of inner ear cells from BM and more specifically from HSCs. The results suggest that mesenchymal cells, including fibrocytes in the adult inner ear, may be derived continuously from HSCs.

Vestibular function disorders and potential mechanisms in irradiation nasopharyngeal carcinoma patients.

CONCLUSIONS: Vestibular function disorders were widespread among nasopharyngeal carcinoma (NPC) patients. The radiation doses to the inner ears were associated with the incidence of vestibular function disorders, but the correlations were mild. The inflammatory responses and possible resolution obstacles of inflammation participated in persistent vestibular function disorders after irradiation. OBJECTIVES: To investigate the incidence of vestibular function disorders in NPC patients after irradiation and potential mechanisms. METHODS: Patients who received radical intensity-modulated radiotherapy for their NPC were recruited. The serum levels of IL-6 and IL-17 were detected by ELISA method. Vestibular evoked myogenic potential (VEMP) tests were used to evaluate vestibular function and correlation analyses were used to analyze the potential mechanisms of vestibular function disorders. RESULTS: Thirty-eight patients were included. The incidences of abnormal ocular VEMP (oVEMP) and cervical VEMP (cVEMP) were 65.79% and 80.26% at the time of completion of radiotherapy, and 61.84% and 71.05% at 3 months after radiotherapy. The mean and maximum radiation doses to the inner ears were both significantly associated with abnormal oVEMP and cVEMP (p < 0.05, all), but the correlations were all mild. The serum levels of IL-6 and IL-17 were both significantly associated with abnormal oVEMP and cVEMP after irradiation (p < 0.05, all).

Cancer treatment in determination of hearing loss.

INTRODUCTION: Chemotherapy and radiotherapy in oncology have repercussions in hearing health, and can damage structures of the inner ear. These repercussions usually, result in a bilateral and irreversible hearing loss. OBJECTIVE: To identify sensorineural hearing loss cases with complaints of tinnitus and difficulty in speech understanding and investigate their relationship with the types of chemotherapy and radiotherapy the patients received. METHODS: Cross-sectional, clinical, observational, analytical, historical cohort study of 58 subjects treated in a public hospital in the state of Sergipe, diagnosed with neoplasia. The subjects were submitted to anamnesis, conventional pure tone audiometry, and speech recognition threshold. RESULTS: Of the 116 ears, 25.9% presented sensorioneural hearing loss characterized by changes in high frequencies. There was a positive correlation between hearing loss and the association of chemotherapy and radiotherapy (p=0.035; R=0.196). The auditory complaint analysis shows that most of the subjects had tinnitus and speech understanding difficulty, even with a normal auditory threshold. CONCLUSIONS: Cancer treatment causes hearing loss, associated with the administration of chemotherapy and radiotherapy. Cyclophosphamide increased the risk of causing hearing loss. Complaints of tinnitus and speech understanding difficulty were observed.

Radiation-induced oscillopsia in nasopharyngeal carcinoma patients.

PURPOSE: To apply a battery of audiovestibular function tests and magnetic resonance imaging (MRI) to investigate the causes of oscillopsia in nasopharyngeal carcinoma (NPC) patients after irradiation (RT). METHODS AND MATERIALS: Of 300 NPC patients, 12 (4%) developed oscillopsia after RT. The mean accumulated radiation dose to the nasopharynx was 112 +/- 30 Gy. Each patient underwent a battery of audiovestibular function tests, including audiometry and the dynamic illegible E, caloric, and rotational tests. RESULTS: Excluding 3 patients with neck fibrosis who could not perform the head turning movement, the remaining 9 patients displayed 100% abnormal dynamic illegible E test results and 100% abnormal refixation saccades. All 12 patients presented with bilateral hearing loss, caloric reductions, and reduced gains of the vestibular ocular reflex (VOR) on the rotational test, indicating bilateral VOR loss. After excluding tumor relapse and radiation necrosis of the brain by MRI, the oscillopsia in these 12 irradiated NPC patients was attributed to bilateral VOR loss. CONCLUSION: Radiation-induced oscillopsia in our NPC patients was attributed to bilateral VOR loss, possibly as a result of higher radiation doses. Hence, the therapeutic benefits of a second course of RT are associated with the potential risk of oscillopsia after RT.

Prospective study of inner ear radiation dose and hearing loss in head-and-neck cancer patients.

PURPOSE: To determine the relationship between the radiation dose to the inner ear and long-term hearing loss. METHODS AND MATERIALS: Eligible patients included those receiving curative radiotherapy (RT) for head-and-neck cancer. After enrollment, patients underwent three-dimensional conformal RT planning and delivery (180-200 cGy/fraction) appropriate for their disease site and stage. The inner ear was contoured on axial CT planning images. Dose-volume histograms, as well as the mean and maximal dose for each structure, were calculated. Patients underwent pure tone audiometry at baseline (before treatment) and 1, 6, 12, 24, and 36 months after RT. The threshold level (the greater the value, the more hearing loss) in decibels was recorded for 250, 500, 1000, 2000, 4000, and 8000 Hz. For patients receiving predominantly unilateral RT, the contralateral ear served as the de facto control. The differences in threshold level between the ipsilateral and contralateral ears were calculated, and the temporal pattern and dose-response relation of hearing loss were analyzed using statistical methods that take into account the correlation between two ears in the same subject and repeated, sequential measurements of each subject. RESULTS: Of the 40 patients enrolled in this study, 35 qualified for analysis. Four patients who received concurrent chemotherapy and RT were analyzed separately. The 31 unilaterally treated patients received a median dose of 47.4 Gy (range, 14.1-68.8 Gy) to the ipsilateral inner ear and 4.2 Gy (range, 0.5-31.3 Gy) to the contralateral inner ear. Hearing loss was associated with the radiation dose received by the inner ear (loss of 210dB was observed in ears receiving >/=45 Gy) and was most appreciable in the higher frequencies (>/=2000 Hz). For a 60-year-old patient with no previous hearing loss in either ear, after receiving 45 Gy, the ipsilateral ear, according to our clinical model, would have a 19.3-dB (95% confidence interval [CI], 15.5-23.0) and 5.4-dB (95% CI, 3.5-7.5) hearing decrement compared with the contralateral ear for 8000 Hz and 1000 Hz, respectively. Age and an initial hearing difference within an ear pair also affected hearing loss. The baseline hearing threshold was inversely related to radiation-induced hearing loss. The degree of hearing loss was dependent on the frequency tested, age, baseline hearing, and baseline difference in hearing between a patient's two ears. CONCLUSION: High-frequency (>/=2000 Hz) hearing acuity worsens significantly after RT in a dose-dependent fashion. A larger number of patients needs to be studied to validate these results. This knowledge can be applied to create guidelines regarding future dose limits to the auditory apparatus for patients undergoing head-and-neck RT.

Electromagnetic fields from mobile phones do not affect the inner auditory system of Sprague-Dawley rats.

The auditory system is the first biological structure facing the electromagnetic fields emitted by mobile phones. The aim of this study was to evaluate the cochlear functionality of Sprague-Dawley rats exposed to electromagnetic fields at the typical frequencies of GSM mobile phones (900 and 1800 MHz) by distortion product otoacoustic emissions, which are a well-known indicator of the status of the cochlea's outer hair cells. A population of 48 rats was divided into exposed and sham-exposed groups. Three sets of four loop antennas, one for sham-exposed animals and two for exposed animals, were used for the local exposures. Rats were exposed 2 h/day, 5 days/week for 4 weeks at a local SAR of 2 W/kg in the ear. Distortion product otoacoustic emissions tests were carried out before, during and after the exposure. The analysis of the data shows no statistically significant differences between the audiological signals recorded for the different groups.

Melatonin protects inner ear against radiation damage in rats.

OBJECTIVES/HYPOTHESIS: To examine the effects of N-acetyl-5-methoxytryptamine (melatonin) on radiation-induced inner ear damage. STUDY DESIGN: An experimental animal model. METHODS: Forty rats were randomized into five groups, as follows: 1) melatonin and then radiotherapy group (n = 8), which received intraperitoneal (i.p.) melatonin (5 mg/kg) followed by irradiation 30 minutes later; 2) radiotherapy and then melatonin group (n = 8), which received irradiation with i.p. melatonin (5 mg/kg) 30 minutes later; 3) melatonin group (n = 8), which received i.p. melatonin (5 mg/kg); 4) radiotherapy group (n = 8), which underwent only irradiation; 5) and the control group (n = 8), which received i.p. 0.9% NaCl. The medications and irradiation were administered for 5 days. All rats underwent the distortion product otoacoustic emission (DPOAE) test before and 10 days after the experiment. The middle ears of the rats were excised, and assessment of tissue alterations in the organs of Corti, spiral ganglions, and stria vascularis were compared among the groups. RESULTS: In the radiotherapy group, the DPOAE amplitudes at frequencies of 4000 to 6000 Hz were significantly decreased when compared with the controls. The DPOAE amplitudes both in the melatonin and then radiotherapy group and the radiotherapy and then melatonin group exhibited better values than they did in the radiotherapy group. Histopathological evidence of damage to the organs of Corti, spiral ganglions, and stria vascularis damage was markedly reduced in both these two groups when compared to the radiotherapy group. CONCLUSION: These results indicate that melatonin may have significant ameliorative effects on cochlear damage secondary to ionizing radiation.

Effects of chronic exposure to electromagnetic waves on the auditory system.

CONCLUSION: The results support that chronic electromagnetic field exposure may cause damage by leading to neuronal degeneration of the auditory system. OBJECTIVES: Numerous researches have been done about the risks of exposure to the electromagnetic fields that occur during the use of these devices, especially the effects on hearing. The aim of this study is to evaluate the effects of the electromagnetic waves emitted by the mobile phones through the electrophysiological and histological methods. METHODS: Twelve adult Wistar albino rats were included in the study. The rats were divided into two groups of six rats. The study group was exposed to the electromagnetic waves over a period of 30 days. The control group was not given any exposure to the electromagnetic fields. After the completion of the electromagnetic wave application, the auditory brainstem responses of both groups were recorded under anesthesia. The degeneration of cochlear nuclei was graded by two different histologists, both of whom were blinded to group information. RESULTS: The histopathologic and immunohistochemical analysis showed neuronal degeneration signs, such as increased vacuolization in the cochlear nucleus, pyknotic cell appearance, and edema in the group exposed to the electromagnetic fields compared to the control group. The average latency of wave in the ABR was similar in both groups (p > 0.05).

Inner ear deficits in irradiated nasopharyngeal carcinoma survivors.

OBJECTIVES/HYPOTHESIS: Despite the advancement of concurrent chemoradiotherapy, inner ear symptoms such as hearing loss, tinnitus, or vertigo/dizziness are still experienced in irradiated nasopharyngeal carcinoma (NPC) survivors. This study utilized an inner ear test battery to assess the causes and sequence of inner ear deficits in irradiated NPC survivors with a mean interval of 10 years after radiotherapy. STUDY DESIGN: Retrospective study. METHODS: Thirty-six irradiated NPC survivors were enrolled. Otoscopy and an inner ear test battery comprising audiometry were performed, as well as ocular vestibular-evoked myogenic potential (oVEMP), cervical VEMP (cVEMP), and caloric tests. RESULTS: Otoscopic examination revealed middle ear complications in 37 ears (51%), including radiation-induced otitis media in 32 ears and otitis media with effusion in five ears. Percentages of abnormal cVEMP test, oVEMP test, bone-conducted mean hearing level, and caloric test were 91%, 75%, 67%, and 39%, respectively, exhibiting a significantly declining sequence in inner ear deficits. Most (67%) NPC survivors had inner ear deficit originated from peripheral vestibular lesion, mainly due to sequela of otitis media. In contrast, 33% of them had inner ear deficit caused by central vestibular disorder. CONCLUSIONS: A significant sequential decline in inner ear function of irradiated NPC survivors was observed from the saccule to the utricle, cochlea, and semicircular canals. Most of them were due to sequela of otitis media, followed by central vestibular disorder. LEVEL OF EVIDENCE: 4.

Radioprotective Effect of Aminothiol PrC-210 on Irradiated Inner Ear of Guinea Pig.

Radiotherapy of individuals suffering with head & neck or brain tumors subserve the risk of sensorineural hearing loss. Here, we evaluated the protective effect of Aminothiol PrC-210 (3-(methyl-amino)-2-((methylamino)methyl)propane-1-thiol) on the irradiated inner ear of guinea pigs. An intra-peritoneal or intra-tympanic dose of PrC-210 was administered prior to receiving a dose of gamma radiation (3000 cGy) to each ear. Auditory Brainstem Responses (ABRs) were recorded one week and two weeks after the radiation and compared with the sham animal group. ABR thresholds of guinea pigs that received an intra-peritoneal dose of PrC-210 were significantly better compared to the non-treated, control animals at one week post-radiation. Morphologic analysis of the inner ear revealed significant inflammation and degeneration of the spiral ganglion in the irradiated animals not treated with PrC-210. In contrast, when treated with PrC-210 the radiation effect and injury to the spiral ganglion was significantly alleviated. PrC-210 had no apparent cytotoxic effect in vivo and did not affect the morphology or count of cochlear hair cells. These findings suggest that aminothiol PrC-210 attenuated radiation-induced cochlea damage for at least one week and protected hearing.