Objective:This study aims to investigate the mechanism and potential effects of two exposures to 100 dB sound pressure level（SPL） broadband white noise, with a 14-days interval, on the myelin sheath of the cochlear auditory nerve in mice. The research provides experimental evidence for understanding the pathophysiological processes of noise-induced hearing loss and hidden hearing loss. Methods:Fifteen 6-week-old male C57BL/6J mice with normal hearing thresholds were randomly divided into three groups: a control group（no noise exposure）, a single noise exposure group, and a double noise exposure group. The single noise exposure group was exposed to 100 dB SPL white noise for 2 hours, and ABR thresholds were measured 1 day（P1） and 14 days（P14） after the exposure. The double noise exposure group was exposed to the same conditions of 100 dB SPL white noise for 2 hours, followed by a second identical exposure 14 days later. ABR thresholds were measured 1 day（P15） and 14 days（P28） after the second exposure. The cochleae of all three groups were then collected for immunofluorescence observation of the basilar membrane and transmission electron microscopy to observe changes in the structure of the auditory nerve myelin sheath. Results:In the single noise exposure group, ABR thresholds at all frequencies were significantly elevated compared to the control group at P1. There were no significant changes in ABR thresholds at any frequency at P14. In the double noise exposure group, ABR thresholds at all frequencies were significantly elevated compared to the control group at P15 and P28（P<0.001）. After the first noise exposure, immunofluorescence observation revealed no significant weakening of the auditory nerve myelin sheath signal; transmission electron microscopy showed no significant changes in myelin sheath morphology. However, after the second noise exposure, immunofluorescence observation revealed a weakening of the myelin sheath signal, and transmission electron microscopy showed thinning of the myelin sheath, disruption of the lamellar structure, and separation from the axon, indicating demyelination. Conclusion:Two exposures to 100 dB SPL broadband white noise can lead to damage to the auditory nerve myelin sheath in mice, whereas a single exposure does not cause significant changes.
Animals ; Male ; Myelin Sheath/pathology* ; Mice ; Cochlear Nerve/pathology* ; Mice, Inbred C57BL ; Noise/adverse effects* ; Hearing Loss, Noise-Induced/physiopathology* ; Cochlea ; Evoked Potentials, Auditory, Brain Stem

OBJECTIVE: To investigate diagnostic value and clinical application of MRI in the children with sensorineural hearing loss (SNHL) before cochlear implantation. METHOD: MRI images of 80 children with the diagnosis of SHNL were retrospectively analyzed in combination with the latest classification of inner ear malformation. RESULT: There were 152 ears of inner ear malformation of 80 cases (160 ears), including 38 ears of cochlear malformation, 33 ears of vestibular malformation, 41 ears of semicircular canal malformation, 37 ears of vestibular aqueduct enlargement, 40 ears of internal auditory canal malformation, and 46 ears of cochlear nerve malformation. CONCLUSION MRI can provide detailed and reliable anatomical information for children with SNHL before cochlear implantation, and help to make the classification diagnosis. Therefore MRI is of great clinical significance for operation plan guidance and prognosis assessment.
Child ; Cochlear Implantation ; Cochlear Nerve ; pathology ; Hearing Loss, Sensorineural ; diagnosis ; pathology ; Humans ; Magnetic Resonance Imaging ; Retrospective Studies ; Semicircular Canals ; pathology ; Temporal Bone ; pathology ; Tomography, X-Ray Computed ; Vestibular Aqueduct ; abnormalities ; pathology

OBJECTIVES: The aim of the present study was to evaluate the internal auditory canal (IAC) and the nerves inside it to define possible structural differences in cases with subjective tinnitus of unknown origin. METHODS: Cases applying to the ear, nose and throat department with the complaint of tinnitus with unknown origin and having normal physical examination and test results were included in the study (n=78). Patients admitted to the radiology clinic for routine cranial magnetic resonance imaging (MRI) and whose MRI findings revealed no pathologies were enrolled as the control group (n=79). Data for the control group were obtained from the radiology department and informed consent was obtained from all the patients. Diameters of the IAC and the nerves inside it were measured through enhanced images obtained by routine temporal bone MRIs in all cases. Statistical evaluations were performed using Student t-test and statistical significance was defined as P<0.05. RESULTS: Measurements of IAC diameters revealed statistically significant differences between the controls and the tinnitus group (P<0.05). Regarding the diameters of the cochlear nerve, facial nerve, inferior vestibular nerve, superior vestibular nerve, and total vestibular nerve, no statistically significant difference was found between the controls and the tinnitus group. CONCLUSION: Narrowed IAC has to be assessed as an etiological factor in cases with subjective tinnitus of unknown origin.
Cochlear Nerve ; Ear ; Facial Nerve ; Humans ; Informed Consent ; Magnetic Resonance Imaging ; Nose ; Pathology ; Pharynx ; Physical Examination ; Temporal Bone ; Tinnitus* ; Vestibular Nerve

BACKGROUND AND OBJECTIVES: Auditory neuropathy is a hearing disorder characterized by the absence or the marked impairment of the auditory brainstem responses with the preservation of the cochlear microphonics (CMs) and otoacoustic emissions. This suggests that outer hair cell (OHC) function is normal but proximal auditory function to OHCs is impaired. It is assumed that the lesion is localized at the level of the inner hair cells (IHCs), auditory nerve fibers, or the synapse between them. This study was aimed to observe the change of hearing threshold and pathology of spiral ganglion cell induced by ouabain application, and present basic data to explain the auditory neuropathy. MATERIALS AND METHOD: Twenty ears of twenty normal hearing cats were used in this study. Cats were treated with 100 microL ouabain (1 mM) applied on the round window. After three days, compound action potential (CAP) and CM were measured and the cochlea was obtained. Pathologic change of spiral ganglion cell was evaluated under light microscope after H&E stain. Normal saline was injected for the control group. RESULTS: In the ouabain group, CAP threshold was increased in all tested frequencies (p<0.001) and the difference of CM threshold was not significant in all frequencies (p>0.05). There was significant difference between CAP and CM threshold shift (p<0.001). In the control group, there was no significant difference in CAP and CM thresholds. Light microscopic findings show that the condensed chromatin and nuclear fragments of spiral ganglion cells of an ear was exposed to ouabain, and outer hair cell and inner hair cell were not damaged. CONCLUSION: This study shows that the CAP threshold was significantly increased but the CM threshold was not changed in the ouabain group. Ouabain induced damage of spiral ganglion cells. This study is not sufficient to explain auditory neuropathy because threshold shift of CAP is not obvious, but it would be helpful to explain that selective damage of spiral ganglion cell would be the mechanism of auditory neuropathy.
Action Potentials ; Animals ; Cats* ; Chromatin ; Cochlea ; Cochlear Nerve ; Ear ; Evoked Potentials, Auditory, Brain Stem ; Hair ; Hearing ; Hearing Disorders ; Ouabain* ; Pathology ; Spiral Ganglion* ; Synapses

BACKGROUNDMost patients with auditory neuropathy (AN) could receive good even the best effects after cochlear implantation. How to diagnose AN objectively and accurately is very important. In this study, we screened the patients with AN according to the presence or absence of compound action potential (CAP) of intraoperative round window electrocochleography (RW ECochG).

METHODSIntraoperative RW ECochG was performed on 32 patients with profound sensorineural deafness, who had normal cochlea during cochlear implantation surgery under general anesthesia in the standard operating room. The cochlear microphonic (CM) and CAP of RW ECochG was observed and recorded.

RESULTSThe presence of CM but the absence of CAP of RW ECochG occurred in 12 among the 32 patients. They were suspected to suffer from AN. The rest patients who had CM and CAP of RW ECochG were thought not to suffer from AN.

CONCLUSIONApplication of intraoperative RW ECochG during the cochlear implantation surgery may objectively and accurately screen the patients with AN, and can give a meaningful clue for implanted device working.

Adolescent ; Adult ; Audiometry, Evoked Response ; methods ; Child ; Child, Preschool ; Cochlear Nerve ; pathology ; Electrophysiology ; methods ; Evoked Potentials ; Female ; Humans ; Infant ; Male ; Round Window, Ear ; Vestibulocochlear Nerve Diseases ; diagnosis ; Young Adult

Cochlear Nerve ; chemistry ; pathology ; Cranial Nerve Neoplasms ; metabolism ; pathology ; Diagnosis, Differential ; Female ; Heart Neoplasms ; metabolism ; pathology ; Humans ; Immunohistochemistry ; Middle Aged ; Neoplasms, Multiple Primary ; metabolism ; pathology ; Neurilemmoma ; metabolism ; pathology ; S100 Proteins ; metabolism ; Vestibulocochlear Nerve Diseases ; metabolism ; pathology ; Vimentin ; metabolism

BACKGROUND AND OBJECTIVES: Tinnitus is one of the most obscure otological pathologies. There is no universally proved treatment modality for tinnitus. Intratympanic lidocaine injection is one of the therapeutic trials. In this study, authors investigated the effects of intratympanically delivered lidocaine on the auditory system in humans. MATERIALS AND METHODS: Two percent of 0.25 cc lidocaine was delivered intratympanically to the affected ears in 5 normal hearing patients with unilateral tinnitus. We assessed auditory function by pure tone audiometry, tympanometry, tinnitus study, auditon evoked otoacoustic emissions, and ABR to observe possible druge Rects in the auditory system. In all five patients, saline was injected to the other intact ear for control purposes. RESULTS: Saline injection did not create significant changes in any of the measures. Intratympanic lidocaine injection did not make any differences between pre- and post-injection audiologic tests except otoacoustic emissions and tinnitus study. It suppressed otoacoustic emmisions and reduced loudness of tinnitus by 10 dB. Lidocaine injection did not cause any changes in latencies or amplitudes in the auditory brainstem response (ABR). CONCLUSION: These results suggest that intratympanically delivered lidocaine has an effect on the organ of Corti structures in human subjects without significantly affecting the auditory nerve or the central auditory pathways. Further investigations on the concentration and volume of intratympanically delivered lidocaine should be made in order to manage patients with tinnitus clinically.
Acoustic Impedance Tests ; Audiometry ; Auditory Pathways ; Cochlear Nerve ; Ear ; Evoked Potentials, Auditory, Brain Stem ; Hearing ; Humans ; Lidocaine* ; Organ of Corti ; Pathology ; Tinnitus* ; Tympanic Membrane