PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Cochlear Nerve”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 775 records · Page 43Linked to original sources
PubMed1983

Frequency selectivity of hair cells and nerve fibres in the alligator lizard cochlea.

Receptor potentials of hair cells and spike discharges of cochlear nerve fibres were recorded with micropipettes from the free-standing region of the basilar papilla of anaesthetized alligator lizards in response to tones. In this region the hair-cell stereocilia are free-standing, i.e. they protrude directly into endolymph and are not in contact with a tectorial membrane. The frequency selectivity of hair-cell responses was measured by means of isovoltage contours of the d.c. (V0) and fundamental-a.c. (V1) component of the receptor potential, i.e. iso-V0 and iso-V1 contours. The frequency selectivity of the nerve-fibre discharge was measured by iso-rate (iso-V0) contours. Iso-V0, iso-V1 and iso-V0 contours are basically V-shaped with a characteristic frequency (c.f.) defined as the frequency at which minimum sound pressure (Pmin) is required to evoke the criterion value of the response. Receptor potential iso-V0 contours and neural iso-V0 contours have similar slopes: the mean slopes of the low-frequency sides (dB/decade) are -43.0 and -44.3; the slopes of the high-frequency sides are 85.0 and 80.2. The band widths of iso-V0 and iso-V0 contours away from c.f. are similar (mean values of Q30dB are 0.40 and 0.53, respectively). The band widths of iso-V0 contours near c.f. are narrower than those of iso-V0 contours (mean values of Q10dB are 2.34 and 1.20, respectively). However, the shapes of the contours near c.f. depend on the iso-response criteria, and we have not determined whether or not iso-V0 and iso-V0 contours are similar near c.f. The shapes of iso-V1 contours differ from those of iso-V0 and iso-V0 contours. Nerve fibre c.f.s are tonotopically organized in the nerve, with lowest c.f.s recorded from fibres innervating the border of free-standing and tectorial regions, a region in which hair-cell stereocilia are longest, and the highest c.f.s recorded from fibres innervating the end of the free-standing region in which hair-cell stereocilia are shortest. The c.f. of nerve-fibre response (and by implication hair-cell response) is, therefore, correlated with the height of the stereociliary tuft. The shapes of iso-V0 contours vary systematically with c.f. and, therefore, tonotopically with nerve position.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1982

[Electrical stimulation of the middle ear in total deafness: results in 375 cases (author's transl)].

Electrical stimulation of the middle ear can provoke sound sensations in 90 p. cent of patients with total deafness, as shown by auditory evoked potentials brain stem recordings. This signifies that cochlear nerve destruction is not complete, and rehabilitation by multiple electrode cochlear implants is possible. The liminal stimulation threshold level appears to be inversely proportional to the functional quality of the electrode-nerve interface obtained by the implants. The electrical stimulation of the middle ear test is therefore essential for selection of patients for operation, and for predicting the quality of rehabilitation that will be obtained.

Adolescent↗
PubMed1996

Intracochlear schwannoma.

In the case reported evaluation of unilateral endocochlear deafness in a 44-year-old man led to a diagnosis of a small intracanalicular neurinoma of the cochlear nerve which had invaded the first turn of the cochlear spiral.

Adult↗
PubMed2005

[Alteration of the auditory function and auditory nerve pathology in Guinea pigs with peripheral nerve demyelination].

OBJECTIVE: To study the auditory function and auditory nerve pathological changes of the experimental allergic neuritis (EAN) animal model in Guinea pigs. METHOD: To establish the animal model of EAN, heterologous myelin basic protein (MBP) of peripheral nerve was used to the immunize Guinea pigs. Serum anti-MBP-IgG levels, sciatic nerve conduction velocity (NCV), hearing thresholds and wave latencies, and pathological changes in auditory nerve, sciatic nerve and cochlea were observed. The immune lesions in inner ear were examined with immunohistochemistry. Auditory brainstem response (ABR) and compound action potential (CAP) were assayed weekly before and after immunization for a period of seven weeks. In the control group, antigen was replaced by the 0.9% saline. RESULT: Serum anti-MBP-IgG levels increased significantly in experimental group comparing with the control group (P < 0.01). Seiatic nerve conduction velocity decreased after immunization, as comparing with the control group (P < 0.01). Sciatic nerve and auditory nerve showed the existence of demyelination. There was significant increase of ABR and CAP thresholds and the latencies of wave I, III, V and N1 in experimental group when compared to the controls (P < 0.01), but no significant changes in inter-peak latencies of I-III, III-V were found( P > 0.05). In addition, there were 4 Guinea pigs (8 ears) in which only appeared lengthened wave latencies with normal hearing thresholds. Immunohistochemistry indicated that antibodies to inner ear from the MBP-sensitized animals distributed in cochlear nerve, neurofiber of inner ear and spiral ganglion cells. Cochlear scanning electron microscopy showed the pathology of inner hair cell with stereociliary disorder and cytoplasmic protrusions. CONCLUSION: The results suggest that auditory nerve demyelination are involved in this experimental allergic neuritis animal model and sciatic nerve demyelination as well, and the auditory abnormalities are elicited. This animal model seems to be a promising one of auditory dysfunction due to demyelination disorders.

Action Potentials↗
PubMed2005

The inhibitory effect of intravenous lidocaine infusion on tinnitus after translabyrinthine removal of vestibular schwannoma: a double-blind, placebo-controlled, crossover study.

OBJECTIVE: Intravenous infusion of lidocaine has previously been demonstrated to have a transient inhibitory effect on tinnitus in 60% of individuals. The site of action has variously been proposed as the cochlea, the cochlea nerve, and the central auditory pathways. To determine whether a central site of action exists, this study investigated the effect of intravenous infusion of lidocaine in individuals with tinnitus who had previously undergone translabyrinthine excision of a vestibular schwannoma, which involves division of the cochlear nerve. STUDY DESIGN: Double-blind, placebo-controlled, crossover study. SETTING: University hospital. PATIENTS: Patients who had undergone translabyrinthine removal of a unilateral, sporadic, and histologically proven vestibular schwannoma in the last decade and who had reported postoperative tinnitus at follow-up were identified from a departmental database. Sixteen patients participated (12 men and 4 women). The mean age (+/- standard deviation) of the patients was 58 +/- 8.6 years, and the meantime since operation was 24.3 +/- 7.3 months. INTERVENTION: Solutions of 2% lidocaine hydrochloride and sodium chloride 0.9% were prepared in identical randomized vials. The volume required for 1.5 ml/kg body weight lidocaine was calculated, and this volume was given over 5 minutes for either vial. Blood pressure, pulse oximetry, and cardiac monitoring were set up and performed throughout the infusions. All investigators were blinded. OUTCOME MEASURES: Patient-completed visual analogue scale measures of tinnitus intensity, pitch, and distress, performed before infusion, 5 minutes after infusion onset, and 20 minutes after infusion onset. RESULTS: A significant difference (Wilcoxon signed-rank test, p < 0.05) between placebo and lidocaine infusion conditions was demonstrated for change in visual analogue scale estimates (preinfusion versus 5 min postinfusion) of tinnitus loudness (p = 0.036), pitch (p = 0.026), and distress (p = 0.04). No significant difference between placebo and lidocaine infusion conditions was demonstrated for change in visual analogue scale estimates (preinfusion versus 20 min postinfusion) of tinnitus loudness (p = 0.066), pitch (p = 0.173), and distress (p = 0.058). The indication is of a short-lasting inhibitory effect on tinnitus of lidocaine infusion compared with saline placebo in patients who have undergone translabyrinthine excision of a vestibular schwannoma. CONCLUSION: Intravenous infusion of lidocaine has a statistically significant inhibitory effect on tinnitus in patients who have previously undergone translabyrinthine removal of a vestibular schwannoma. The site of action of lidocaine in this instance must be in the central auditory pathway, as the cochlear and vestibular nerves are sectioned during surgery, and this finding has important implications for the task of identifying other agents that will have a similar tinnitus-inhibiting effect.

Adult↗
PubMed1987

Cytochalasin D suppresses sound evoked potentials in the guinea pig cochlea.

Cytochalasin D (CD), an inhibitor of actin polymerization, was perfused through the guinea pig cochlea while monitoring various cochlear potentials. CD (10(-7)-10(-5) M) reduced the magnitude of the compound action potential of the cochlear nerve and the summating potential, and increased N1 latency. The cochlear microphonic potential was the least sensitive potential with only a slight effect being observed at 10(-5) M. The results are consistent with the hypothesis that actin has a role in cochlear function.

Actins↗
PubMed2006

Tissue resistivities determine the current flow in the cochlea.

PURPOSE OF REVIEW: In individuals with severe to profound hearing loss, cochlear implants bypass normal inner ear function by applying electrical current directly into the cochlea, thereby stimulating cochlear nerve fibers. Stimulating discrete populations of spiral ganglion cells in cochlear implant users' ears is similar to the encoding of small acoustic frequency bands in a normal-hearing person's ear. Thus, spiral ganglion cells stimulated by an electrode convey the information contained by a small acoustic frequency band. Problems that refer to the current spread and subsequent nonselective stimulation of spiral ganglion cells in the cochlea are reviewed. RECENT FINDINGS: Cochlear anatomy and tissue properties determine the current path in the cochlea. Current spreads largely via scala tympani and across turns. While most of the current leaves the cochlea via the modiolus, the facial canal and the round window constitute additional natural escape paths for the current from the cochlea. Moreover, degenerative processes change tissue resistivities and thus may affect current spread in the cochlea. SUMMARY: Electrode design and coding strategies may result in more spatial stimulation of spiral ganglion cells, resulting in a better performance of the electrode-tissue interface.

Cochlea↗
PubMed1992

Cochlear implants in the management of bilateral acoustic neuromas.

Multichannel cochlear implants currently provide the only modality for successful auditory rehabilitation of patients with bilateral profound sensorineural hearing loss who derive no benefit from amplification. We have developed a protocol for patients with neurofibromatosis and bilateral acoustic neuromas in which every effort is made to preserve hearing in at least one ear. Failing that, the cochlear nerve is spared, potentially allowing for the insertion of a cochlear implant. We present our data on one such patient whose auditory function was restored with a Nucleus mini 22-channel cochlear implant following removal of his acoustic neuroma.

Adult↗
PubMed1990

[Postoperative MR findings in acoustic neuromas: nerve edema within the internal auditory canal].

Postoperative MR findings of eleven acoustic neuromas were analyzed. MRI's were able to clearly visualize residual tumor around the 7th and 8th cranial nerves that were left to preserve cranial nerve function, although conventional X ray CT scans often failed to detect it due to artifacts in the parapetrous area. The facial nerves preserved during operations were also visualized from their brainstem portion to the internal auditory meatus. These findings indicate that MRI is excellent in delineating soft tissue in the CP angle that would be overlooked by conventional X ray CT scan. It was also found that the nerve bundles within the internal auditory canal gained increased signal intensity on the T1 and proton weighted images after surgical interventions and that this effect extended into the most distal end of the nerve bundles and even into the intracochlear portion of the cochlear nerve. The nerve bundles with increased signal intensity were conspicuously enhanced after intravenous administration of Gd-DTPA. This indicated that the blood nerve barrier of the nerves within the internal auditory canal were disrupted due to the surgical manipulations in excising tumors. Following such surgical manipulations, nerve edema ensued, although manipulations in the cerebello-pontine angle were done carefully and protectively under a surgical microscope. The clinical significance of disruption of the blood nerve barrier and following nerve edema were discussed from the standpoint of preservation of the 7th and 8th cranial nerve functions.

Blood-Brain Barrier↗
PubMed1978

Peripheral auditory processing in normal and abnormal ears: physiological considerations for attempts to compensate for auditory deficits by acoustic and electrical prostheses.

The processing of complex acoustic signals, such as speech, by the normal peripheral auditory system is described in terms of the properties of individual cochlear nerve fibres and the effects of lateral inhibition in the cochlear nucleus. The implications of the peripheral filtering of signals is indicated in psychophysical terms. In cochlear pathology, these filtering characteristics deteriorate, and the implications arising from the consequent deterioration in auditory frequency selectivity are outlined for the coding of loudness and for the analysis of speech. These considerations suggest theoretically ideal methods of compensation for recruitment by multichannel instantaneous compression, and for deterioration in format analysis by dichotic frequency partition. Finally, the implications for a minimal design for artificial electrical multi-electrode array stimulation of the cochlea in order to impart speech information to the profoundly deaf, are explored. Single wire stimulation, on the other hand, should be able to impart useful prosodic and minimal speech feature information to aid in lip reading and in the acquisition of speech.

Animals↗
PubMedDate not supplied

Topographical relationship of the facial and vestibulocochlear nerves in the subarachnoid space and internal auditory canal.

PURPOSE: Our purpose was to investigate the topographical relationship of the facial and vestibulocochlear nerves from the brain stem through the internal auditory canal. METHODS: We dissected 15 formalin-fixed cadaveric heads and performed MR examinations in 35 healthy subjects in order to examine the topographical relationship of the facial and vestibulocochlear nerves. The cadaveric dissections and the in vivo MR imaging findings were compared indirectly. RESULTS: The relationship between the facial and vestibulocochlear nerves showed some variation among individuals and according to the location of the nerves within the cisterns or canal. Near the brain stem, 53% of the vestibulocochlear nerves were partially segmented on MR images. The vestibulocochlear nerve was completely divided into separate nerves only in the most lateral portion of the canal, except in three cadaveric dissections, in which separation of the superior vestibular nerve was seen near the brain stem. The facial and cochlear nerves were of similar size on 36% of the MR images. The superior vestibular nerve was larger than the inferior vestibular nerve on 81% of the MR images. CONCLUSION: The appearance of the facial and vestibulocochlear nerves was variable but followed certain consistent patterns.

Adult↗
PubMed2000

Effectiveness of preoperative administration of an N-methyl-D-aspartate antagonist to enhance cochlear neuron resistance to intraoperative traumatic stress: an experimental study.

OBJECT: Cochlear neurons are inevitably exposed to traumatic stress during surgical removal of an acoustic neuroma; that event is an important cause of postoperative cochlear neuronal degeneration, with subsequent loss of spiral ganglion cells (SGCs). The object of this study was to investigate whether preoperative pharmacological treatment can enhance the resistance of cochlear neurons to the traumatic stress of surgery. METHODS: Cochlear neuronal degeneration was induced in 17 rats by controlled compression of the cerebellopontine angle portion of the cochlear nerve. Dizocilpine maleate (MK-801; 10 mg/kg), an N-methyl-D-aspartate (NMDA) antagonist, was administered intraperitoneally to six of the 17 rats 30 minutes before compression occurred. Two weeks after compression, each rat was killed, and the numbers of SGCs in histological preparations of temporal bones were counted. CONCLUSIONS: Spiral ganglion cells were more numerous in rats administered dizocilpine maleate (p < 0.03) than in rats that did not receive treatment, indicating that receptor-mediated glutamate neurotoxicity may participate in the pathogenesis of trauma-induced cochlear neuron death and that administration of an NMDA antagonist before surgery may protect the nerve from injury leading to hearing loss.

Animals↗
PubMed1996

Glutamine synthetase and glutamate metabolism in the guinea pig cochlea.

Glutamate is thought to act as a neurotransmitter of the sensory hair cells of the organ of Corti. Glutamine synthetase could be involved in a type of glutamate-glutamine cycle in the cochlea which could clear glutamate off the synaptic cleft and replenish the hair cell glutamate neurotransmitter store. Using both light and electron microscopic immunocytochemistry to localize this enzyme in the guinea pig cochlea, we have observed immunoreactive satellite glial cells surrounding parvalbumin-immunoreactive primary auditory neurons in the spiral ganglion. Glutamine synthetase was also detected in Schwann cells of the osseous spiral lamina which form the myelin sheath of nerve fibers. On the contrary, no immunoreactivity could be observed in the cochlear nerve and in the organ of Corti, although this organ contains structures able to take up glutamate. Although they confirm earlier works involving glutamine synthetase in the conversion of L-[3H]glutamate taken up by glial cells, our results suggest that the cochlear glutamate-glutamine cycle is not primarily involved in the recycling and replenishment of hair cell neurotransmitter glutamate. Alternatively, it is proposed that glutamine synthetase functions to limit the perilymphatic glutamate concentrations.

Animals↗
PubMed1997

Management of 1000 vestibular schwannomas (acoustic neuromas): surgical management and results with an emphasis on complications and how to avoid them.

OBJECTIVE: To identify the actual benefits and persisting problems in treating vestibular schwannomas by the suboccipital approach, the results and complications in a consecutive series of 1000 tumors surgically treated by the senior author were analyzed and compared with experiences involving other treatment modalities. METHODS: Pre- and postoperative clinical statuses were determined and radiological and surgical findings were collected and evaluated in a large database for 962 patients undergoing 1000 vestibular schwannoma operations at Nordstadt's neurosurgical department from 1978 to 1993. RESULTS: By the suboccipital transmeatal approach, 979 tumors were completely removed; in 21 cases, deliberate partial removal was performed either in severely ill patients for decompression of the brain stem or in an attempt to preserve hearing in the last hearing ear. Anatomic preservation of the facial nerve was achieved in 93% of the patients and of the cochlear nerve in 68%. Major neurological complications included 1 case of tetraparesis, 10 cases of hemiparesis, and caudal cranial nerve palsies in 5.5% of the cases. Surgical complications included hematomas in 2.2% of the cases, cerebrospinal fluid fistulas in 9.2%, hydrocephalus in 2.3%, bacterial meningitis in 1.2%, and wound revisions in 1.1%. There were 11 deaths occurring at 2 to 69 days postoperatively (1.1%). The techniques that were developed for avoidance of complications are reported. The analysis identifies preexisting severe general and/or neurological morbidity, cystic tumor formation, and major caudal cranial nerve deficits as relevant risk factors. CONCLUSION: The current treatment options of complete tumor resection with ongoing reduction of morbidity are well fulfilled by the suboccipital approach. By careful patient selection, the mortality rate should be further reduced to below 1%.

Cranial Nerve Diseases↗
PubMed2001

Nerve origin of the acoustic neuroma.

Two hundred and seventy-one Japanese patients who underwent surgical removal of neuroma from the cerebello-pontine angle using the translabyrinthine approach were retrospectively reviewed in order to investigate the nerve origin on an anatomical basis. In 269 out of the 271 cases, the origin of the neuromas was identified. Among these cases, 84.8 per cent of tumours originated from the inferior vestibular nerve (IVN), followed by the superior vestibular nerve (SVN) (8.9 per cent). Of the 5.6 per cent of tumours arising from the vestibular nerve, however, it could not be determined whether they originated from the SVN or IVN. Two cases of neuromas originating from the facial nerve were seen (0.7 per cent). No neuroma arose from the cochlear nerve. Currently, the diagnosis of acoustic neuromas is best made with Gd-enhanced magnetic resonance imaging (MRI). However, our data indicate that the development of a functional test of the individual IVN can be useful for screening most cases of acoustic neuroma and in facilitating their early diagnosis.

Cerebellar Neoplasms↗
PubMed2003

Preoperative high resolution CT and MR imaging in cochlear implantation.

INTRODUCTION: Accurate preoperative imaging of the temporal bone in patients receiving cochlear implants is important. High resolution computed tomography (HRCT) and magnetic resonance (MR) imaging are the 2 preoperative imaging modalities that provide critical information on abnormalities of the otic capsule, pneumatisation of the mastoid, middle ear abnormalities, cochlear ducts patency and presence of cochlear nerve. MATERIALS AND METHODS: The HRCT and MR imaging in 46 cochlear implant patients in our department were reviewed. RESULTS: Majority of our patients [34 patients (73.9%)] showed normal HRCT of the temporal bone; 5 (10.9%) patients had labyrinthitis ossificans, 2 (4.3%) had Mondini's abnormality and 2 (4.3%) had middle ear effusion. One patient each had high jugular bulb, hypoplasia of the internal auditory canal and single cochlear cavity, respectively. CONCLUSION: The above findings contribute significantly to our surgical decisions regarding candidacy for surgery, side selection and surgical technique in cochlear implantation.

Cochlear Diseases↗
PubMed1987

The effects of hypoxia on sensory cells of the cochlea in chinchilla.

The effects of hypoxia on the sensory epithelium of the cochlea were investigated in the chinchilla. Systemic hypoxia was produced by increasing the dead space of the respiratory tidal volume. A disarrangement of hair-cell stereocilia, and cytoplasmic protrusions from sensory cells are the main findings in cochleas from hypoxic animals; these changes take place firstly at the inner hair-cells then, with the increase in degree of hypoxia, at the outer hair-cells. These degenerative changes of sensory cells correlate well with both respiratory suppression and with the elevation of auditory threshold to click stimulation as monitored using the compound action potential recording from the cochlear nerve. The latter measure appears to be a useful indicator of cochlear hypoxia. Our morphological findings are similar to other studies including those which have reported on post-mortem cochlear hair-cell degeneration. Our studies indicate the deleterious effects of long term hypoxia on cochlear mechanisms and point to the need for careful monitoring of cardiovascular and respiratory functions in animals under anaesthesia for physiological studies of the auditory system.

Action Potentials↗