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Journal of Visualized Experiments : JoVE Oct 2014Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted deaf...
Direct electrical stimulation of spiral ganglion neurons (SGNs) by cochlear implants (CIs) enables open speech comprehension in the majority of implanted deaf subjects(1-) (6). Nonetheless, sound coding with current CIs has poor frequency and intensity resolution due to broad current spread from each electrode contact activating a large number of SGNs along the tonotopic axis of the cochlea(7-) (9). Optical stimulation is proposed as an alternative to electrical stimulation that promises spatially more confined activation of SGNs and, hence, higher frequency resolution of coding. In recent years, direct infrared illumination of the cochlea has been used to evoke responses in the auditory nerve(10). Nevertheless it requires higher energies than electrical stimulation(10,11) and uncertainty remains as to the underlying mechanism(12). Here we describe a method based on optogenetics to stimulate SGNs with low intensity blue light, using transgenic mice with neuronal expression of channelrhodopsin 2 (ChR2)(13) or virus-mediated expression of the ChR2-variant CatCh(14). We used micro-light emitting diodes (µLEDs) and fiber-coupled lasers to stimulate ChR2-expressing SGNs through a small artificial opening (cochleostomy) or the round window. We assayed the responses by scalp recordings of light-evoked potentials (optogenetic auditory brainstem response: oABR) or by microelectrode recordings from the auditory pathway and compared them with acoustic and electrical stimulation.
Topics: Animals; Channelrhodopsins; Cochlear Nerve; Ganglia, Spinal; Mice; Mice, Transgenic; Microelectrodes; Neurons; Optogenetics
PubMed: 25350571
DOI: 10.3791/52069 -
Brain : a Journal of Neurology May 2013Abnormal auditory adaptation is a standard clinical tool for diagnosing auditory nerve disorders due to acoustic neuromas. In the present study we investigated auditory...
Abnormal auditory adaptation is a standard clinical tool for diagnosing auditory nerve disorders due to acoustic neuromas. In the present study we investigated auditory adaptation in auditory neuropathy owing to disordered function of inner hair cell ribbon synapses (temperature-sensitive auditory neuropathy) or auditory nerve fibres. Subjects were tested when afebrile for (i) psychophysical loudness adaptation to comfortably-loud sustained tones; and (ii) physiological adaptation of auditory brainstem responses to clicks as a function of their position in brief 20-click stimulus trains (#1, 2, 3 … 20). Results were compared with normal hearing listeners and other forms of hearing impairment. Subjects with ribbon synapse disorder had abnormally increased magnitude of loudness adaptation to both low (250 Hz) and high (8000 Hz) frequency tones. Subjects with auditory nerve disorders had normal loudness adaptation to low frequency tones; all but one had abnormal adaptation to high frequency tones. Adaptation was both more rapid and of greater magnitude in ribbon synapse than in auditory nerve disorders. Auditory brainstem response measures of adaptation in ribbon synapse disorder showed Wave V to the first click in the train to be abnormal both in latency and amplitude, and these abnormalities increased in magnitude or Wave V was absent to subsequent clicks. In contrast, auditory brainstem responses in four of the five subjects with neural disorders were absent to every click in the train. The fifth subject had normal latency and abnormally reduced amplitude of Wave V to the first click and abnormal or absent responses to subsequent clicks. Thus, dysfunction of both synaptic transmission and auditory neural function can be associated with abnormal loudness adaptation and the magnitude of the adaptation is significantly greater with ribbon synapse than neural disorders.
Topics: Acoustic Stimulation; Adaptation, Physiological; Adolescent; Adult; Aged; Auditory Perception; Child; Cochlear Nerve; Female; Hair Cells, Auditory, Inner; Hearing Disorders; Humans; Hyperacusis; Loudness Perception; Male; Middle Aged; Young Adult
PubMed: 23503620
DOI: 10.1093/brain/awt056 -
Archives of Pathology & Laboratory... Nov 2003Lipochoristomas (lipomatous choristomas) are rare tumors of the acoustic nerve (cranial nerve VIII/vestibulocochlear nerve) within the internal acoustic canal and...
CONTEXT
Lipochoristomas (lipomatous choristomas) are rare tumors of the acoustic nerve (cranial nerve VIII/vestibulocochlear nerve) within the internal acoustic canal and sometimes the cerebellopontine angle, and are histogenetically believed to be congenital malformations. Their clinically indolent behavior has recently prompted a more conservative management protocol in a quest for maximal nerve/hearing preservation. This approach contrasts sharply with that for the common internal acoustic canal/cerebellopontine angle tumors, the neuroepithelial neoplasms (acoustic schwannomas and meningiomas), which behave more aggressively and have more prominent clinical manifestations. Owing to their rarity, the clinicopathologic features of cranial nerve VIII lipochoristomas have been obtained mainly through case reports.
OBJECTIVE
We present the clinicopathologic features of 11 cases of lipochoristomas of cranial nerve VIII.
DESIGN
The 11 cases were documented between 1992 and 2003. We performed complete clinical reviews with histologic, histochemical, and immunohistochemical analyses of formalin-fixed, paraffin-embedded tumor samples.
RESULTS
The patients were 8 men and 3 women with hearing loss of the right ear (5 patients) or the left ear (6 patients). No patient had bilateral tumors. All lipochoristomas histologically possessed mature adipose tissue admixed with varied amounts of mature fibrous tissue, tortuous thick-walled vessels, smooth muscle bundles, and skeletal muscle fibers, the latter verified with immunohistochemistry.
CONCLUSIONS
The histomorphologic and immunophenotypic evidence showed that these tumors are better characterized as choristomas than as simple "lipomas," as they have been labeled in the past. Their overall nonaggressive clinical nature in addition to the characteristic radiologic and histomorphologic findings are important clinicopathologic features for the pathologist to recognize and differentiate, especially during frozen section evaluations, in order to direct the neurosurgeon to a more appropriate conservative therapeutic intervention.
Topics: Adult; Cerebellar Neoplasms; Cerebellopontine Angle; Cochlear Nerve; Cranial Nerve Neoplasms; Female; Follow-Up Studies; Formaldehyde; Hearing Loss; Humans; Immunohistochemistry; Lipoma; Magnetic Resonance Imaging; Male; Middle Aged; Paraffin Embedding; Tissue Fixation; Tomography, X-Ray Computed; Vestibulocochlear Nerve
PubMed: 14567720
DOI: 10.5858/2003-127-1475-LLTOTA -
Audiology & Neuro-otology 2012The belief that cochleovestibular schwannomas arise from the glial-Schwann cell junction has repeatedly been quoted in the literature, although there is no published...
The belief that cochleovestibular schwannomas arise from the glial-Schwann cell junction has repeatedly been quoted in the literature, although there is no published evidence that supports this statement. A systematic evaluation of the nerve of origin and the precise location of cochleovestibular schwannomas using our respective archival temporal bone collections was conducted. Forty tumors were within the internal auditory canal (IAC), while 10 were intralabyrinthine neoplasms. Of the 40 IAC schwannomas, 4 arose from the cochlear nerve, and 36 from the vestibular nerve. Twenty-one tumors clearly arose lateral to the glial-Schwann cell junction, while 16 tumors filled at least two thirds of the IAC, with the epicenter of the neoplasm located in the mid part or the lateral part of the IAC. Only 3 schwannomas were located in the medial one third of the IAC in the area of the glial-Schwann cell junction. We concluded that cochleovestibular schwannomas may arise anywhere along the course of the axons of the eighth cranial nerve from the glial-Schwann sheath junction up until their terminations within the auditory and vestibular end organs.
Topics: Adult; Aged; Aged, 80 and over; Cochlear Nerve; Female; Humans; Intercellular Junctions; Male; Middle Aged; Neuroglia; Neuroma, Acoustic; Schwann Cells; Temporal Bone; Vestibular Nerve; Vestibule, Labyrinth
PubMed: 21968195
DOI: 10.1159/000331394 -
Medical Science Monitor : International... Apr 2022Loudness recruitment is a common symptom of hearing loss induced by cochlear lesions, which is defined as an abnormally fast growth of loudness perception of sound... (Review)
Review
Loudness recruitment is a common symptom of hearing loss induced by cochlear lesions, which is defined as an abnormally fast growth of loudness perception of sound intensity. This is different from hyperacusis, which is defined as "abnormal intolerance to regular noises" or "extreme amplification of sounds that are comfortable to the average individual". Although both are characterized by abnormally high sound amplification, the mechanisms of occurrence are distinct. Damage to the outer hair cells alters the nonlinear characteristics of the basilar membrane, resulting in aberrant auditory nerve responses that may be connected to loudness recruitment. In contrast, hyperacusis is an aberrant condition characterized by maladaptation of the central auditory system. Peripheral injury can produce fluctuations in loudness recruitment, but this is not always the source of hyperacusis. Hyperacusis can also be accompanied by aversion to sound and fear of sound stimuli, in which the limbic system may play a critical role. This brief review aims to present the current status of the neurobiological mechanisms that distinguish between loudness recruitment and hyperacusis.
Topics: Acoustic Stimulation; Cochlear Nerve; Hearing Loss; Humans; Hyperacusis; Loudness Perception
PubMed: 35396343
DOI: 10.12659/MSM.936373 -
Otolaryngologia Polska = the Polish... Sep 2020<b>Background:</b> The aim was to present the methodology and interpretation of intraoperative hearing monitoring with simultaneous Transtympanic...
Detailed insight into transtympanic electrocochleography (TT-ECochG) and direct cochlear nerve action potential (CNAP) for intraoperative hearing monitoring in patients with vestibular schwannoma - methodology of measurements and interpretation of results.
<b>Background:</b> The aim was to present the methodology and interpretation of intraoperative hearing monitoring with simultaneous Transtympanic Electrocochleography (TT-ECochG) and direct Cochlear Nerve Action Potential (CNAP) measurements during vestibular schwannoma removal. <br><b>Materials and Methods:</b> Detailed methodology of measurements and interpretation of results are presented in three exemplary patients who underwent tumor removal via middle fossa approach (MFA) with the use of intraoperative monitoring of hearing with TT-ECochG and direct CNAP performed in real time. In addition, all responses were automatically recorded and stored along with surgical information and subjected to detailed analyses and calculation after surgery. <br><b>Results:</b> The following changes in TT-ECochG and direct CNAP responses were observed: Patient #1 - TT-ECochG and CNAP responses with minor, but transient, morphology changes (hearing was preserved); Patient #2 - CNAP responses changed significantly but, temporarily, from triphasic into biphasic responses later, with marked but partially reversible desynchronization of CNAP; changes in TT-ECochG responses were also observed but, at the end, returned to baseline (surgery-related deterioration of hearing); Patient #3 - irreversible changes of TT-ECochG and direct CNAP (complete loss of hearing). <br><b>Conclusions:</b> A combination of TT-ECochG and direct CNAP allows for real-time monitoring of auditory function during vestibular schwannoma resection and surgical manipulation which contribute to the risk of hearing loss. Therefore, the surgeon can be instantly informed about changes which could increase the possibility of preserving the patient's hearing.
Topics: Action Potentials; Adult; Audiometry, Evoked Response; Cochlear Nerve; Ear Neoplasms; Evoked Potentials, Auditory; Female; Humans; Male; Middle Aged; Monitoring, Intraoperative; Neurilemmoma; Neuroma, Acoustic
PubMed: 33408268
DOI: 10.5604/01.3001.0014.3668 -
The Journal of Neuroscience : the... Feb 2016Auditory nerve excitation and thus hearing depend on spike-generating ion channels and their placement along the axons of auditory nerve fibers (ANFs). The developmental...
UNLABELLED
Auditory nerve excitation and thus hearing depend on spike-generating ion channels and their placement along the axons of auditory nerve fibers (ANFs). The developmental expression patterns and native axonal locations of voltage-gated ion channels in ANFs are unknown. Therefore, we examined the development of heminodes and nodes of Ranvier in the peripheral axons of type I ANFs in the rat cochlea with immunohistochemistry and confocal microscopy. Nodal structures presumably supporting presensory spiking formed between postnatal days 5 (P5) and P7, including Ankyrin-G, NaV1.6, and Caspr. These immature nodal structures lacked low-voltage-activated KV1.1 which was not enriched at juxtaparanodes until approximately P13, concurrent with the developmental onset of acoustic hearing function. Anatomical alignment of ANF spike-initiating heminodes relative to excitatory input from inner hair cell (IHC) ribbon synapses continued until approximately P30. High-voltage-activated KV3.1b and KV2.2 were expressed in mutually exclusive domains: KV3.1b was strictly localized to nodes and heminodes, whereas KV2.2 expression began at the juxtaparanodes and continued centrally along the first internode. At spike-initiating heminodes in the distal osseous spiral lamina, NaV1.1 partly overlapped NaV1.6 and ankyrin-G. ANFs displayed KV7.2 and KV7.3 at heminodes, nodes, internodes, and the unmyelinated synaptic terminal segments beneath IHCs in the organ of Corti. In response to sound, spikes are initiated at the heminode, which is tightly coupled to the IHC ribbon synapse ∼20-40 μm away. These results show that maturation of nodal alignment and ion channel content may underlie postnatal improvements of ANF excitability and discharge synchrony.
SIGNIFICANCE STATEMENT
Acoustic and electrical hearing depends on rapid, reliable, and precise spike generation in auditory nerve fibers. A limitation of current models and therapies is a lack of information on the identities and topographies of underlying ion channels. We report the developmental profile of the auditory nerve spike generator with a focus on NaV1.1, NaV1.6, KV1.1, KV2.2, KV3.1b, KV7.2, and KV7.3 in relation to the scaffold ankyrin-G. Molecular anatomy of the spike generator matures in the weeks after developmental onset of hearing function. Subcellular positioning of voltage-gated ion channels will enable multicompartmental modeling of auditory nerve responses elicited by afferent chemical neurotransmission from hair cells and modulated by efferent neurotransmitters or evoked by extracellular field stimulation from a cochlear implant.
Topics: Animals; Ankyrins; Axons; Cochlea; Cochlear Nerve; Female; Hair Cells, Auditory, Inner; Hearing; Male; Nerve Fibers; Organ of Corti; Potassium Channels; Presynaptic Terminals; Ranvier's Nodes; Rats; Rats, Wistar; Sodium Channels; Spiral Lamina; Synapses
PubMed: 26888923
DOI: 10.1523/JNEUROSCI.3437-15.2016 -
Proceedings of the National Academy of... Aug 2006Binaural auditory neurons exhibit "best delays" (BDs): They are maximally activated at certain acoustic delays between sounds at the two ears and thereby signal spatial...
Binaural auditory neurons exhibit "best delays" (BDs): They are maximally activated at certain acoustic delays between sounds at the two ears and thereby signal spatial sound location. BDs arise from delays internal to the auditory system, but their source is controversial. According to the classic Jeffress model, they reflect pure time delays generated by differences in axonal length between the inputs from the two ears to binaural neurons. However, a relationship has been reported between BDs and the frequency to which binaural neurons are most sensitive (the characteristic frequency), and this relationship is not predicted by the Jeffress model. An alternative hypothesis proposes that binaural neurons derive their input from slightly different places along the two cochleas, which induces BDs by virtue of the slowness of the cochlear traveling wave. To test this hypothesis, we performed a coincidence analysis on spiketrains of pairs of auditory nerve fibers originating from different cochlear locations. In effect, this analysis mimics the processing of phase-locked inputs from each ear by binaural neurons. We find that auditory nerve fibers that innervate different cochlear sites show a maximum number of coincidences when they are delayed relative to each other, and that the optimum delays decrease with characteristic frequency as in binaural neurons. These findings suggest that cochlear disparities make an important contribution to the internal delays observed in binaural neurons.
Topics: Animals; Auditory Pathways; Cochlear Nerve; Inferior Colliculi
PubMed: 16908859
DOI: 10.1073/pnas.0601396103 -
Acta Otorrinolaringologica Espanola May 2008To evaluate the fraction of patients recovering to normal function after complete facial nerve paralysis secondary to acoustic neuroma surgery, and also to address the...
OBJECTIVE
To evaluate the fraction of patients recovering to normal function after complete facial nerve paralysis secondary to acoustic neuroma surgery, and also to address the ophthalmologic complications associated with it and the therapeutic options.
MATERIAL AND METHOD
We performed a retrospective review of 30 cases operated on in our department for acoustic neuroma and who, despite anatomical preservation of the facial nerve, developed a complete post-operative facial nerve paralysis (grade VI of House-Brackmann [HB]). We analyzed the evolution of the facial paralysis in relation to the tumour size, patient age, surgical approach and localization of the tumour. In addition, we studied the ophthalmologic complications and their treatment.
RESULTS
Only 5 of the 30 cases studied (16.6 %) recovered to normal facial nerve function (HB grade I). We observed a tendency for a poor recovery of the cases with tumour size bigger than 2 cm, males, those older than 65 years and lesions resected by the translabyrinthine approach. Only 1 patient presented serious ophthalmologic complications.
CONCLUSIONS
Our study reveals that only a small percentage of patients achieve total recovery of facial function. We have to be on the alert to ocular complications in this kind of patient.
Topics: Adult; Aged; Cochlear Nerve; Corneal Ulcer; Disease Progression; Facial Paralysis; Female; Humans; Male; Middle Aged; Neuroma, Acoustic; Peripheral Nervous System Neoplasms; Postoperative Complications; Retrospective Studies
PubMed: 18501157
DOI: No ID Found -
Medical Science Monitor : International... Jun 2015Despite improvements in microsurgical technique and the use of intraoperative electrophysiological monitoring, the potential for facial and cochlear nerve injury remains...
BACKGROUND
Despite improvements in microsurgical technique and the use of intraoperative electrophysiological monitoring, the potential for facial and cochlear nerve injury remains a possibility in the resection of vestibular schwannomas (VS). We reviewed a series of 221 cases of VS resected via a retrosigmoid approach at our institution from October 2008 to April 2014 and determined the incidence of postoperative facial and cochlear deficits.
MATERIAL AND METHODS
A total of 221 patients - 105 (47.5%) male and 116 (52.5%) female - with a mean age of 46.1 years (range 29-73 years), with VS ≥3 cm (n=183, 82.8%) and <3 cm (n=38, 17.2%) underwent surgical resection via a retrosigmoid approach and were evaluated for postoperative facial and cochlear nerve deficits.
RESULTS
Near-total resection (>95% removal) was achieved in 199 cases (90%) and subtotal resection (>90% removal) in 22 cases (10%). At 6 month follow-up, House-Brackmann grades I-III were observed in 183 cases (82.8%), grade IV in 16 cases (7.2%), and grade V in 22 cases (10%). Of the 10 patients that had preoperative functional hearing, 3 (33%) retained hearing postoperatively. Cerebrospinal fluid leakage occurred in 6 patients (2.7%), lower cranial nerve palsies in 9 patients (4.1%), and intracranial hematomas 3 cases (1.4%).
CONCLUSIONS
The observed incidence of persistent postoperative nerve deficits is very low. Meticulous microsurgical dissection of and around the facial and cochlear nerves with the aid of intraoperative electrophysiological nerve monitoring in the retrosigmoid approach allows for near-total resection of medium and large VS with the possibility of preservation of facial and cochlear nerve function.
Topics: Adult; Aged; Cochlear Nerve; Facial Nerve Injuries; Female; Humans; Intraoperative Neurophysiological Monitoring; Male; Microsurgery; Middle Aged; Neuroma, Acoustic; Neurosurgical Procedures; Otologic Surgical Procedures; Treatment Outcome
PubMed: 26056168
DOI: 10.12659/MSM.892607