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Results for “Cochlear Nerve”

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At least 667 records · Page 37Linked to original sources

PubMed1991

[Endoscopy of porus acousticus internus].

The anatomical relationships between the arterial loop and the nerve in the porus acousticus region in 50 adult specimens were studied by endoscopy via the postsigmoid approach. No trauma to the intracranial structure occurred during the study. It was found that in 68 percent of specimens a cerebellar arterial loop existed in the porus acousticus region. There were six patterns of relationship between the arterial loop and the acoustico-facial boundle. A loop between the nerves, a loop under the nerves and a loop above the nerves were the common types. In 62 percent of specimens which presented a loop in this region, the loops were in close relationship with the canal or porus. In the remaining 38 percent the loops did not show any relationship with the canal. The findings were symmetrical in only 40 percent. The separation of the vestibular and the cochlear nerves could be seen in 51.1% of the specimens. The advantages of endoscopy in this region were discussed.

Adult↗

PubMed2005

Sensorineural hearing loss in patients with cerebral palsy after asphyxia and hyperbilirubinemia.

The location of lesions causing hearing loss in patients with cerebral palsy due to asphyxia or neonatal hyperbilirubinemia has remained unclear. We performed behavioral audiometry, distortion product otoacoustic emission (DPOAE) and auditory brainstem evoked response (ABR) in six patients with cerebral palsy due to asphyxia or neonatal hyperbilirubinemia in order to determine the lesion location causing their hearing impairment. In all cases, behavioral audiometry revealed a threshold elevation of 50-75 dB and ABR were no response. DPOAE were totally absent in five patients and normal in one patient. Our study suggests that lesions causing hearing loss potentially include the organ of Corti especially at the outer hair cells and the cochlear nerve.

Adolescent↗

PubMed1979

Some aspects of temporal coding by single cochlear fibres from regions of cochlear hair cell degeneration in the guinea pig.

Some temporal coding properties of cochlear nerve fibers are investigated in kanamycin-treated guinea pigs (GPs) with various degrees of outer hair cell (OHC) degeneration. In particular, the phase locking ability of fibres from pathological cochleas, and also their adaptation properties are compared with the properties of normal cochlear fibres. No systematic effects of OHC loss on these properties have so far been found. These preliminary results therefore suggest (in so far as these animals can be regarded as models of sensorineural hearing loss of cochlear origin in man) that little deterioration should be expected in functions purely dependent upon faithful temporal coding of the stimulus waveform.

Acoustic Stimulation↗

PubMed1997

Application of parasagittal surface coil MRI to otoneurological diagnosis.

Parasagittal surface coil magnetic resonance imaging (MRI) of the internal auditory canal and the inner ear was performed in patients with otoneurological diseases. T2-weighted fast spin-echo sequences, plain and enhanced T1-weighted sequences were used to examine the inner ear and the individual nerves in the internal auditory canal. Normal parasagittal images of the inner ear and the internal auditory canal and 4 patients with otoneurological disorders are presented. Precise location of the acoustic tumor was visualized and postoperative status of the internal auditory canal and the inner ear was assessed by the present method. The cochlear nerve was not identified in a patient with long-standing unilateral deafness. A follow-up study with MRI was performed in a patient with Meniere's disease who underwent endolymphatic-mastoid shunt surgery, showing gradual postoperative shrinkage of the shunted endolymphatic sac. The present method provides a new approach to the assessment of otoneurological disorders.

Adolescent↗

PubMed2001

A model of the electrically excited human cochlear neuron. II. Influence of the three-dimensional cochlear structure on neural excitability.

A simplified spiraled model of the human cochlea is developed from a cross sectional photograph. The potential distribution within this model cochlea is calculated with the finite element technique for an active scala tympani implant. The method in the companion article [Rattay et al., 2001] allows for simulation of the excitation process of selected elements of the cochlear nerve. The bony boundary has an insulating influence along every nerve fiber which shifts the stimulation condition from that of a homogeneous extracellular medium towards constant field stimulation: for a target neuron which is stimulated by a ring electrode positioned just below the peripheral end of the fiber the extracellular voltage profile is rather linear. About half of the cochlear neurons of a completely innervated cochlea are excited with monopolar stimulation at three-fold threshold intensity, whereas bipolar and especially quadrupolar stimulation focuses the excited region even for stronger stimuli. In contrast to single fiber experiments with cats, the long peripheral processes in human cochlear neurons cause first excitation in the periphery and, consequently, neurons with lost dendrite need higher stimuli.

Animals↗

PubMed1997

Management of vestibular schwannomas (acoustic neuromas): the value of neurophysiology for evaluation and prediction of auditory function in 420 cases.

OBJECTIVE: From 1978 to 1993, 1000 vestibular schwannomas were operated on at the Department of Neurosurgery at Nordstadt Hospital. The goal was to improve the chances of hearing preservation by recording auditory brain stem responses (ABRs). ABRs can be used for preoperative classification of cochlear nerve impairment and for prediction of the chances of hearing preservation. PATIENTS AND METHODS: In addition to the previously described audiometric testing, the patients underwent perioperative and intraoperative bilateral ABR recording at 100-dB condensation and rarefaction click stimulation. The classification system of five types of ABRs, as presented before, is based on the presence and on the latencies of Waves I, III, and V, with a special emphasis on Wave III's representing the activity of the first brain stem nuclei within the auditory pathway. According to an analysis of 420 preoperative ABRs, in case of a preoperative Type 1 or 2, the rate of hearing preservation is 80%. DISCUSSION: In the case of good clinical and audiometric hearing, a severely deteriorated ABR is mostly an indicator of severe nerve compression and adhesion by the tumor. In view of subsequently reported experiences with intraoperative ABR monitoring, the value of the presented system emphasizing the importance of Wave III is stressed and discussed with other views in the literature. The criteria presented here are not designed for recognition of retrocochlear disease but aim for evaluation of the state of the auditory nerve and its perspective. CONCLUSION: By the presented classification of ABR Type B1 through B5, preoperative prediction of the likelihood of hearing preservation is improved.

Adult↗

PubMed2003

Ultrastructure and immunocytochemical characteristics of cells in the octopus cell area of the rat cochlear nucleus: comparison with multipolar cells.

Cells in the octopus cell area of the rat ventral cochlear nucleus have been connected to the monaural interpretation of spectral patterns of sound such as those derived from speech. This is possible by their fast onset of firing after each octopus cell and its dendrites have been contacted by many auditory fibres carrying different frequencies. The cytological characteristics that make these large cells able to perform such a function have been studied with ultrastructural immunocytochemistry for glycine, GABA and glutamate, and compared to that of other multipolar neurons of other regions of the ventral cochlear nucleus. Cells in the octopus cell area have an ultrastructure similar to large-giant D-multipolar neurons present in other areas of the cochlear nucleus, from which they differ by the presence of a larger excitatory axo-somatic synaptic input and larger mitochondria. Octopus cells are glycine and GABA negative, and glutamate positive with different degree. Large octopus cells receive more axo-somatic boutons than smaller octopus cells. Fusiform octopus cells are found sparsely within the intermediate acoustic striae. These cells are large to giant excitatory neurons (23-35 microm) with 62-85% of their irregular perimeter covered with large axo-somatic synaptic boutons. Most boutons contain round vesicles and are glycine and GABA negative but glutamate positive. The latter excitatory boutons represent about 70% of the input to octopus cells. Glycine positive boutons with flat and pleomorphic vesicles account for 9-10% of the input while GABA-ergic boutons with pleomorphic vesicles represent about 20% of the synaptic input. Other few, multipolar cells within the rat octopus cell area are surrounded by more inhibitory than excitatory terminals which contain flat and pleomorphic vesicles, a feature distinctive from that of true octopus cells. The latter resemble multipolar cells seen outside the octopus cell area that project to the contralateral inferior colliculus and cochlear nucleus. Based on this study, two types of large multipolar cells are present in the octopus cell area: 1) those that receive about 70% of axo-somatic R boutons and stain more intensely for glutamate may correspond to pure onset neurons (Oi); 2) those with less than 33% of R axosomatic boutons, with less immunoreactivity to glutamate and sometimes glycine positive may represent the onset chopper neurons (Oc). In the octopus cell area the first type appears more prevalent. The present study suggests that octopus cells are a special type of excitatory D-multipolar neuron confined to the octopus cell area and mainly innervated by glutamatergic cochlear nerve terminals.

Animals↗

PubMed2003

Auditory nerve fibre responses to salicylate revisited.

Ototoxicity of salicylate is accompanied by a temporary hearing loss and tinnitus and has therefore been used to study tinnitus in animal models. Salicylate induced elevated central auditory activity has been interpreted as a correlate of tinnitus. Whether this elevated activity in the central auditory system is due to an increased activity in the auditory nerve is still under discussion. To explore this issue, we recorded the activity of single auditory nerve fibres in anaesthetised gerbils following systemic injection of salicylic acid. Firstly, compound action potential (CAP) thresholds were determined at 5-0 min intervals. Fifteen to 30 min after 200 mg/kg salicylic acid, threshold loss developed in the high frequency range. At 2 h CAP threshold loss reached a plateau amounting to 15-20 dB above 16 kHz, 0-5 dB below 2 kHz. An almost immediate start of threshold loss was observed after 400 mg/kg salicylic acid. A plateau of threshold loss was reached after 1.5 h with values of 25 dB in the high, 5-10 dB in the low frequency range. Secondly, responses of single auditory nerve fibres were studied after administration of 200 mg/kg salicylic acid. Frequency tuning curves and rate intensity (RI) functions at characteristic frequency (CF) were measured. Two hours and more after application, single fibre thresholds were elevated by about 20 dB at all CFs. Sharpness of tuning was reduced. Mean spontaneous rate was significantly reduced at CFs below 5 kHz (mean: 44 vs 28 AP/s). At CFs above 5 kHz mean spontaneous rate remained unchanged. In RI functions no change in maximum discharge rate was observed. The altered response properties can be interpreted by the known effects of salicylate on the prestin mediated active process of the outer hair cells. The elevated activity in the central auditory system after salicylate intoxication thus cannot be caused by cochlear nerve hyperactivity.

Action Potentials↗

PubMed1979

Neuroleptanesthesia for the guinea pig. An ideal anesthetic procedure for long-term physiological studies of the cochlea.

The guinea pig is notoriously difficult to anesthetize with conventional agents. Cardiorespiratory depression by general depressant anesthetic agents can render the cochlea abnormal. I report a technique that uses the specific neuroleptic and analgesia properties of the agents droperidol and phenoperidine, respectively, in combination with small doses of pentobarbital sodium, which is required only to produce unconsciousness. These agents can be given intraperitoneally, intramuscularly, or intravenously. The regimen allows performance of substantial surgery (including intracranial) and long-term (minimum, six to ten hours) physiological studies, such as those on the cochlea, with excellent cardiorespiratory stability. The method has been in continuous use in this laboratory since 1974 for single-fiber recordings from the cochlear nerve of normal and kanamycin-treated guinea pigs. This method has proved to be substantially more effective than use of pentobarbital, thiopental sodium, urethan, chloralose, or ketamine alone.

Animals↗

PubMed1988

Divergent projections of physiologically characterized rat ventral cochlear nucleus neurons as shown by intra-axonal injection of horseradish peroxidase.

An attempt was made to correlate electrophysiological and morphological characteristics of rat ventral cochlear nucleus neurons. Their axonal course and their soma morphology were investigated using the intra-axonal horseradish peroxidase method. Prior to labeling, neurons were characterized by recording their response patterns to acoustic stimulation with pure tones. Three types of cells were found: Category I (37 neurons) exhibited "primarylike" responses and a spontaneous firing rate below 10 spikes/s. Category II (21 neurons) showed "on" responses and little spontaneous activity. Category III (9 neurons) had "primarylike" responses like neurons in category I. However, the spontaneous activity rate of these neurons was significantly higher (mean: 95 spikes/s). Among the response categories, the morphological characteristics differed in some prominent aspects. Within each category, however, the morphological properties were rather similar. All neurons in category I were globular/bushy cells located in the area of the entrance of the cochlear nerve. The axon of each cell coursed along the ventral acoustic stria and consistently innervated the lateral superior olive ipsilaterally, and the nucleus of the trapezoid body and the nucleus of the lateral lemniscus contralaterally. Some neurons also projected to periolivary nuclei ipsilaterally and contralaterally. Neurons in category II were located in the posteroventral cochlear nucleus and were presumably multipolar/stellate cells. Their axons coursed via the intermediate acoustic stria and innervated mainly contralateral periolivary regions as well as the contralateral nucleus of the lateral lemniscus. Ipsilaterally, the lateral superior olive and the superior periolivary nucleus were innervated by some of the category II neurons. Somata types of neurons in category III could not be identified morphologically, but somata were located in caudal parts of the posteroventral cochlear nucleus that correspond to the octopus cell area. Their axons coursed via the intermediate acoustic stria and innervated periolivary regions and the contralateral nucleus of the lateral lemniscus. Thus, their axonal distribution differed only slightly from neurons in category II. These data confirm and extend previous findings regarding the efferent connections of ventral cochlear neurons. They emphasize the complexity of the axonal projection patterns of single cochlear nucleus cells. Since two types of response patterns and three types of axonal projection patterns have been observed, there remains an ambiguous relation between response pattern and axonal projection site.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗

PubMed2001

Clinical and neurophysiological observations after superior petrosal vein obstruction during surgery of the cerebellopontine angle: case report.

IMPORTANCE: Preservation of venous drainage during surgery of the cerebellopontine angle has received little attention. CLINICAL PRESENTATION: We describe changes in brainstem auditory evoked potentials after temporary obstruction of the superior petrosal vein during surgical resection of a small meningioma at the petrous apex via a standard suboccipital-lateral approach. Temporary clipping of the petrosal vein resulted in deterioration of the brainstem auditory evoked potentials. The tumor was removed with preservation of the superior petrosal vein. CONCLUSION: A transient postoperative cochlear nerve deficit emphasizes the importance of venous drainage and its preservation during surgery for small lesions of the cerebellopontine angle that do not distort normal anatomic structures.

Cerebellopontine Angle↗

PubMed1991

Three modality evoked potentials in Charcot-Marie-Tooth disease (HMSN-1).

Sixteen patients with dominant hereditary motor-sensory neuropathy type I (HMSN I), members of 5 families, underwent trimodality evoked potential studies. All patients had clinically normal optic nerves. History of deafness was present in 3 patients and sensory-neural hearing defect was found in 5 of 7 patients in whom audiometry was obtained. In 43.7 percent of the subjects significant prolongation of P100 of the VEP was found. Prolongation of N19 of the SEP was found in all 12 subjects examined. Significant bilateral prolongation of peak I of the ABEP was found in 37.5 percent of the subjects and in 50 percent of the ears examined: these findings indicated that in addition to peripheral nerves, the myelin of the optic and cochlear nerves is also affected in HMSN type I.

Adolescent↗

PubMed1996

Localization of the mineralocorticoid receptor in rat cochlear tissue.

Distribution of the mineralocorticoid receptor within rat cochlear tissue was studied by immunohistochemistry. Intense immunoreactions of mineralocorticoid receptor antibodies were observed in outer and inner hair cells of the organ of Corti, stria vascularis, spiral ligament and spiral ganglion cells. Moderate to weak immunostaining was observed in the spiral limbus and cochlear nerve. Results of this study suggest that cochlear tissue is a mineralocorticoid hormone target tissue.

Animals↗

PubMed1996

[Assessment of cochlear functions of patients with acoustic neuromas].

Electrocochleographic cochlear microphonics (ECochG-CM) and Evoked Otoacoustic Emissions (EOAE) were recorded for 17 patients with acoustic neuromas to assess their cochlear functions. ECochG-CM was recorded by a transtympanic needle electrode technique. The acoustic stimuli of EOAE were short tone bursts and thresholds of detection of the slow components were determined. In 13 of the 17 patients, elevated detection thresholds of ECochG-CM and/or abnormal interaural differences in detection thresholds of the slow components of EOAE were observed. The patients with hearing loss and an elevated thresholds of CM were believed to have cochlear impairments. Those with hearing loss and a relatively low detection threshold of CM were thought to have cochlear nerve damage and a smaller degree of cochlear impairment. The correlation of ECochG-CM and EAOE was 0.799. Both ECochG-CM and EOAE were useful in evaluating the cochlear functions of patients with acoustic neuromas. Although EOAE was easier to apply clinically, ECochG was indispensable when detailed examinations of cochlear functions were necessary.

Adult↗

PubMed1991

Vestibular neurotomy by retrosigmoid approach: technique, indications, and results.

During the past 15 years, 96 retrosigmoid vestibular neurotomies have been used in the surgical management of incapacitating Meniere's disease for the control of vertigo and preservation of hearing. This posterior approach of the pontocerebellar angle gives the best view on the acousticofacial nerve bundle, through a 2 x 2 cm suboccipital craniotomy immediately behind the mastoid and sigmoid sinus. Then the vestibular nerve is easily identified, separated from the cochlear nerve and sectioned, the facial nerve not being at risk, as it lies much deeper. Actually, the majority of authors agree that vestibular neurotomy is the most effective surgical treatment in relieving disabling vertigo (96% of cases) with serviceable hearing, but few surgeons know that the retrosigmoid approach is simpler and more reliable than the middle fossa or retrolabyrinthine approaches, with a low incidence of complications. The purpose of this paper is to emphasize the routine use of the retrosigmoid approach.

Aged↗

PubMed1976

Neurological applications of surface-recorded electrocochleography.

A new outpatient technique, involving the recording of auditory-evoked responses from scalp electrodes, is described. Responses are obtained from the cochlea, cochlear nerve, and auditory brain stem nuclei. The effects of various disorders on these responses are illustrated and the procedure is assessed as a diagnostic technique.

Auditory Perception↗

PubMed1984

Results and perspectives with extracochlear round window electrodes.

The results obtained with implanted electrodes at the round window are comparable to results with electrodes in the scala tympani or in the hearing nerve in respect to frequency and amplitude resolution with pulsatile and sinusoidal stimulation (with considerable interpatient variations). Although the subjective quality of the perceived sounds is expected to vary depending on the stimulation site, it seems that timing effects of electrical stimulation may play a major role in pitch perception as required for voice and sound recognition or prosody identification. Our technique is a safe procedure involving only routine middle ear surgery to place the induction coil within the mastoid bone and to put an electrode at the round window margin. By an external stimulator, sounds are transformed to electrical stimuli suited to excite surviving fibers of the cochlear nerve. This helps the patient to communicate and provides some basic cues for speech discrimination.

Adult↗

PubMedDate not supplied

Type II collagen-induced autoimmune sensorineural hearing loss and vestibular dysfunction in rats.

Autoimmune sensorineural hearing loss was induced in rats by immunizing them with native bovine type II collagen. Type I and denatured type II collagen, administered by an identical immunization procedure, would not induce disease. Evidence of sensorineural hearing loss was obtained by measuring the brainstem evoked potential and by observing histopathologic changes consisting of cochlear nerve degeneration and perineural vasculitis in affected animals. Immunized animals had high levels of antibodies to native type II collagen.

Animals↗