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 397 records · Page 22Linked to original sources
PubMed1987

Avulsion rupture of the internal auditory artery during operations in the cerebellopontine angle: a study in monkeys.

The effect of manipulations in the cerebellopontine (CP) angle on the cochlear nerve was studied in 12 rhesus monkeys to elucidate how surgical procedures in the CP angle may affect the peripheral auditory system. Brain stem auditory evoked potentials and compound action potentials from the cochlear nerve were recorded throughout the experiments and were studied to determine the level of injury to the cochlear nerve. After the manipulations, the animals were perfused with fixatives and their temporal bones were removed and examined histologically. The monkeys showed electrophysiological changes similar to those observed in humans as a result of surgical manipulations in the CP angle. Avulsions of the internal auditory artery and cochlear nerve fibers at the area cribrosa were the most common histological findings. The auditory evoked potentials were suddenly and irreversibly lost during the manipulations in 3 monkeys, and hemorrhagic foci were identified histologically in these animals at the fundus of the internal auditory canal (the area cribrosa). No morphological changes at locations other than the area cribrosa were identified in these 3 monkeys. The results of this study indicate that injury to the internal auditory artery at the area cribrosa may play an important role in the abrupt loss of hearing experienced by some patients while they are undergoing operations in the CP angle. This study also led to speculation regarding the possible existence of collateral circulation to the cochlea as a factor in injury to the internal auditory artery during acoustic neurinoma operations.

Animals↗
PubMed1999

Spatial organization of the reciprocal connections between the cat dorsal and anteroventral cochlear nuclei.

We are studying the interconnections between the anteroventral cochlear nucleus (AVCN) and the dorsal cochlear nucleus (DCN). Biotinylated dextran was injected into the DCN, where the best frequency of responses was also recorded. Ventrotubercular neurons in AVCN were labeled, along with cochlear nerve fibers and the axons of cells in DCN. In AVCN, a central band of labeled cochlear nerve axons and large endbulbs was labeled. Bordering this band was a 'fringe' of smaller tuberculoventral axonal endings forming pericellular nests. Most AVCN neurons projecting to DCN were stellate, elongate, or giant cells, located in the posterior division of AVCN, regardless of the DCN injection site. About 75% of the labeled AVCN cells lay within the bands of labeled cochlear nerve fibers. Another 15% were in the outer fringes on either side of these bands, while 10% were outside the bands and the fringes. These findings suggest that most AVCN neurons projecting to the DCN conform to the tonotopic map. A significant portion of the ventrotubercular neurons occupy side-bands in AVCN. Reciprocally, the tuberculoventral tract forms a robust fringe of axonal endings flanking the central bands. The neuronal and axonal bands and side-bands may underlie excitatory and inhibitory signal transformations.

Animals↗
PubMed2002

Electrical stimulation of the auditory nerve via cochlear implants in patients with auditory neuropathy.

Auditory neuropathy (AN) is a term used to describe an auditory disorder in which there is evidence of normal outer hair cell function (otoacoustic emissions and/or cochlear microphonics) and poor function of the auditory nerve (absent or highly distorted auditory brain stem response starting with wave I). Many of these patients have evidence of generalized peripheral nerve disease, leading to an assumption that the peripheral portion of the auditory nerve is the most likely site of lesion. A small group of these patients has received cochlear implants, and the majority of them achieve average to above-average performance. Although this outcome may seem incongruous with neural disease, average performance by patients with AN may be a result of the reintroduction of neural synchrony by electrical stimulation and/or the fact that most deaf patients have poor nerve survival. Although cochlear implants are promising for deaf patients with AN, more study of the disorder is needed.

Adult↗
PubMedDate not supplied

Intraoperative measurements of auditory-evoked potentials in three patients with acoustic neuroma.

Auditory brainstem responses (ABRs), electrocochleograms and the evoked potentials from the internal auditory canal were recorded simultaneously in 3 acoustic neuroma (AN) patients. The neural conduction in the internal auditory canal was examined by recording the compound action potentials of the cochlear nerve. In an AN patient with wave I only in the ABR, the neural conduction of the excitement in the cochlear nerve was blocked within the internal auditory canal. In 2 AN patients with elongated interpeak latency differences between waves I and V in ABRs, the neural conduction velocity of the cochlear nerve was lower than that of normal subjects. These results provide neurophysiological evidence that low neural conduction velocity in the cochlear nerve results in the abnormal ABR.

Adult↗
PubMed1986

Pathophysiological mechanisms of intraoperative and postoperative hearing deficits in cerebellopontine angle surgery: an experimental study.

Pathophysiological mechanisms responsible for intraoperative and postoperative hearing deficits associated with cerebellopontine (CP) angle operations were explored experimentally in dogs. The CP angle operative manipulations performed were the same as those experienced by human patients, and auditory evoked potentials were monitored intraoperatively. As a result of the operative manipulations, petechial or confluent hemorrhages occurred at the compressed portions of the cochlear nerve, and intravascular clots were often observed. Disintegration of the nerve fibers was verified by ultrastructural examination. Moreover, rupture of the microvasculature within the cochlear nerve occurred at locations remote from the operative site, due to stretching of the nerve trunk. The Obersteiner-Redlich zone, the Schwann-glial junction of the cochlear nerve, was a locus minoris resistentiae in CP angle surgery; the vasa nervorum easily bled at this zone and the peripheral and central myelins easily separated at their junctional zones ("central" avulsion injury). Intracochlear hemorrhages were identified as the most probable cause of the sudden loss of all components of the auditory evoked potentials, a frequent predictor of postoperative hearing loss, although rupture, occlusion, or vasospasm of the main trunk of the internal auditory artery have also been implicated as possible causes of such hearing losses. The results of this study show that hearing preservation is highly dependent on preserving not only the nerve at the operative site but also the remote O-R zone and intracochlear structures.

Animals↗
PubMed2006

Role of CT and MRI in the preoperative evaluation of auditory brainstem implantation in patients with congenital inner ear pathology.

PURPOSE: The purpose of this study was to evaluate the reliability of computed tomography (CT) and magnetic resonance imaging (MRI) in characterising cochlear nerve anomalies in auditory brainstem implant candidates with congenital hearing loss. MATERIALS AND METHODS: Seventeen patients affected by congenital sensorineural hearing loss were examined by CT and MRI. Inner ear malformations eligible for auditory brainstem implants were classified according to the Casselman classification. All patients subsequently received auditory brainstem implants. RESULTS: Suspected congenital anomalies were confirmed by CT and MRI in all 17 patients. There were 5/17 bilateral cochlear nerve aplasias and 12/17 cochleovestibular anomalies. Of these, 5/12 patients had a common cochleovestibular cavity, 2/12 had bilateral cochlear aplasia and cochlear nerve agenesis, 1/12 had type I incomplete partition, 2/12 had type II incomplete partition and 2/12 had cochlear hypoplasia. CONCLUSIONS: Preoperative CT and MRI assessment of patients with sensorineural hearing loss is reliable. MRI provided additional information, identifying the possible absence of cochlear nerve and excluding other central nervous system (CNS) diseases.

Adolescent↗
PubMedDate not supplied

Histologic findings in two very small intracanalicular solitary schwannomas of the eighth nerve.

Two very small intracanalicular tumors, resected en bloc with the complete eighth nerve, were serially sectioned in order to study the relationship between the tumors and the nerves of origin. Both cases met the size criteria for hearing conservation surgery; however, the patient with the smaller tumor and the better hearing had no recognizable cochlear nerve fibers passing the tumor. The cochlear nerve in the patient with poorer hearing was completely free of tumor. The tumor with the infiltrated cochlear nerve seemed to originate from the inferior vestibular nerve. The other tumor seemed to arise from the superior vestibular nerve. Proximally, the tumors occupied a more central location in the involved nerves, but they abruptly became eccentric and exophytic as they proceeded laterally. Nerve fibers remaining about the tumors were displaced to the periphery. These nerve fiber aggregates became quite thin and attenuated, frequently separating into smaller aggregates which, ultimately, were incorporated into the tumors. As fibers came closer to the tumors, they tended to change from their longitudinal direction toward a more circumferential orientation about the surface of the tumors. The tumor-nerve fiber interfaces were quite variable throughout the course of the tumor, ranging from large aggregates of nerve fibers distinctly separate from the tumors to aggregates separate but tightly applied to the tumors without a tissue plane between, to aggregates partially incorporated within the periphery of the tumors, to aggregates completely incorporated into the periphery of the tumors.(ABSTRACT TRUNCATED AT 250 WORDS)

Cochlear Nerve↗
PubMed1995

Neuronal organization of the cochlear nuclei in alligator lizards: a light and electron microscopic investigation.

The organization of neurons and fibers in the cochlear nuclei of the alligator lizard (Gerrhonotus multicarinatus) was examined with light and electron microscopy. In this species, much is known about the anatomy and physiology of the inner ear including the cochlear nerve, but little is known about the synaptic connections of cochlear fibers on second-order neurons. These data will help to develop general principles addressing the cellular organization of the vertebrate auditory system. Subdivisions of the cochlear nuclei were defined on the basis of their histologic appearance and neuronal composition. Neuron classes were proposed from their light microscopic and ultrastructural features. Nucleus magnocellularis medialis consists of a homogeneous population of neurons called "lesser ovoid" cells. Nucleus magnocellularis lateralis consists of "greater ovoid" and "small" cells. Nucleus angularis lateralis consists of "spindle" cells. Lastly, nucleus angularis medialis contains a population of large neurons called "duckhead" and "multipolar" cells, and a population of smaller neurons called "bulb" and "agranular" cells. These neuron populations are differentially innervated by tectorial and free-standing cochlear fibers that are associated with separate frequency ranges. All neuronal populations except agranular cells were observed to receive synaptic input from cochlear nerve fibers. In nucleus magnocellularis medialis and nucleus angularis medialis, primary afferents form both chemical and electrical synapses with resident neurons. These observations imply that acoustic information is synaptically processed in fundamentally distinct ways in the cochlear nuclei of alligator lizards and distributed along separate neural circuits. Thus, the characteristic structural and functional dichotomy of the alligator lizard inner ear is extended to central auditory pathways by way of cochlear nerve projections.

Animals↗
PubMed2006

Absent semicircular canals in CHARGE syndrome: radiologic spectrum of findings.

BACKGROUND AND PURPOSE: This paper describes the CT findings that characterize the middle and inner ear anomalies in coloboma, heart defects, choanal atresia, mental retardation, genitourinary, and ear anomalies (CHARGE) syndrome. With this information, neuroradiologists will be better prepared to provide clinically relevant information to their referring physicians regarding this rare syndrome. MATERIALS AND METHODS: CT studies from 13 patients were reviewed by 2 neuroradiologists with Certificate of Additional Qualification. Each ear was counted separately for a total of 26 ears. Middle and inner ear anomalies associated with CHARGE syndrome were categorized. Investigational review board approval was obtained. RESULTS: Twenty of 26 (77%) ears demonstrated cochlear aperture atresia. Four of these ears were evaluated with MR imaging and were found to lack a cochlear nerve. Twenty-one of 26 (81%) cochlea had some form of dysplasia. Six of 26 (23%) round windows were aplastic. Three of 26 (12%) round windows were hypoplastic. Twenty-one of 26 (81%) oval windows were atretic or aplastic. Fifteen of 26 (58%) vestibules were hypoplastic or dysplastic. There were 5 of 26 (19%) enlarged vestibular aqueducts. Twelve of 26 (46%) vestibular aqueducts had an anomalous course. All cases demonstrated absent semicircular canals. Twenty-three of 26 (88%) facial nerve canals had an anomalous course. Four of 26 (15%) tympanic segments were prolapsed. Three of 26 (12%) temporal bones had an anomalous emissary vein referred to as a petrosquamosal sinus. Twenty-one of 26 (81%) middle ear cavities were small. Twenty-three of 26 (93%) ossicles were dysplastic with ankylosis. Three of 26 (12%) internal auditory canals were small. CONCLUSION: The CT findings that correlate to the anomalies of CHARGE syndrome affect conductive as well as sensorineural hearing. Stenosis of the aperture for the cochlear nerve aperture on CT is suggestive of hypoplasia or absence of the cochlear nerve, which has been demonstrated in some cases by MR. Absence of the cochlear nerve would be a contraindication to cochlear implantation.

Abnormalities, Multiple↗
PubMed2006

Auditory outcomes in tumor vs. nontumor patients fitted with auditory brainstem implants.

Auditory brainstem implants (ABIs) are currently indicated for patients older than 12 years with neurofibromatosis type 2 (NF2) who had bilateral schwannoma removed. Over the last 10 years, we have extended the indications for ABIs to nontumor children and adult patients with cochlear or cochlear nerve injuries or malfunctions who would not benefit from a cochlear implant. We have provided ABIs for patients with cochlear nerve aplasia and other injuries, and patients in whom any benefit was, or would be, severely compromised as in extensive cochlear ossification. In the present chapter we report our recent findings in adult ABI patients and compare the psychophysical and speech perception outcomes in tumor with those in nontumor patients. We demonstrate that the ABI can stimulate the central auditory system in a way that gives the ability of open set speech understanding, and can thus be indicated in nontumor adult patients who are not candidates for a cochlear implant. From April 1997 to January 2006, a total of 80 patients, 62 adults and 18 children, were fitted with ABIs in the University of Verona ENT Department; age ranged from 14 months to 70 years. Twenty-six patients had NF2 with bilateral vestibular schwannoma removal, and 54 had nontumor diseases of the cochlear nerve or cochlea. The retrosigmoid approach was used in all patients. All patients had a functioning implantation, and no complications were observed during the operation, activation as well as long-term use of the ABI. All patients, except 1 (NF2), reported auditory sensations with activation of various numbers of electrodes (from 5 to 21). Different electrodes elicited different pitch sensations. At 1 year after implantations nontumor adults scored from 12 to 100% in open set speech perception tests (average 59%), and tumor (NF2) patients scored from 5 to 30% (average of 11%). The differences between these results are statistically significantly (p < 0.01). To investigate the cause of the differences in performance between tumor and nontumor ABI recipients, a series of psychophysical tests were done consecutively in 39 adult patients with implants (25 nontumor and 14 tumor patients) from May 1999 to April 2004 and with a follow-up of at least 1 year. The outcome of this study shows that: (1) The ABIs allow most tumor and nontumor patients to experience improved communication as well as awareness of environmental sounds. (2) Nontumor patients had better hearing outcomes than tumor patients when the variation in the auditory benefit with the ABI in relation to the patient's underlying pathological conditions were taken into consideration. (3) A significant number of nontumor patients are able understand speech at a level comparable to that of the most successful cochlear implant users including conversational telephone use. (4) The ABI represents the tool for hearing rehabilitation in patients with profound hearing loss who cannot be fitted with cochlear implants.

Adolescent↗
PubMed1981

Demyelinating disease as the assumed cause of hearing loss and vertigo. A case report with light- and electron-microscopic findings.

A patient initially presenting typical symptoms of idiopathic sudden deafness later developed disabling episodic vertigo, which led to translabyrinthine eighth nerve transection. Morphological examination of the removed cochlear nerve specimen revealed a demyelinating process in the neuroglial portion of the nerve. The major part of the peripheral, neurolemmal portion of the cochlear nerve was normal. The inferior vestibular nerve was fibrotic. The major part of the superior vestibular nerve was normal. Some of its peripheral bundles showed increased endoneurial fibrosis. It is suggested that a demyelinating process was the cause of the patient's symptoms.

Adult↗
PubMed1994

Vulnerability of hearing function during acoustic neuroma surgery.

Intraoperative monitoring of auditory evoked potentials reveals possible correlations between surgical maneuvers and the function of auditory structures and pathways in cerebellopontine angle surgery. Direct cochlear nerve action potentials (CNAPS) furnish realtime information on the function of the cochlea and cochlear nerve and were utilized in 14 patients undergoing removal of small (12-18 mm) unilateral acoustic tumors. The latency of the first negative component (N1) of the CNAPs proved extremely sensitive in detecting intraoperative auditory damage and was a good predictive index of postoperative auditory outcome. Evaluation of temporal and morphological CNAP patterns allowed identification of coagulation close to the cochlear nerve, drilling of the internal auditory canal and removal of the intrameatal portion of the tumor as the most critical steps in hearing preservation.

Adult↗
PubMed1997

The expression of messenger RNAs coding for growth factors, their receptors, and eph-class receptor tyrosine kinases in normal and ototoxically damaged chick cochleae.

Messenger RNAs coding for growth factors and receptor tyrosine kinases were measured by quantitative competitive and by semi-quantitative reverse-transcription polymerase chain reaction in whole and dissected chick inner ears. The fibroblast growth factor (FGF) receptor 1 chick embryonic kinase (CEK) 1 was expressed in all structures examined (otocyst, hatchling whole cochlea, cochlear nerve ganglion, and cochlear and vestibular sensory epithelia), although slightly more heavily in the otocyst. The related fibroblast growth factor receptors CEK 2 and 3 were preferentially expressed in the nerve ganglion and in the vestibular sensory epithelium, respectively. FGF1 mRNA was low in early development, increasing to mature levels at around embryonic age 11 days, while FGF2 mRNA was expressed at constant levels at all ages. In response to ototoxic damage, FGF1 mRNA levels were increased in the early damaged cochlear sensory epithelium. Immunohistochemistry for CEK1 showed that normal hair cells expressed the receptor heavily on the hair cell stereocilia, while with early damage, CEK1 came to be expressed heavily on the apical surfaces of the supporting cells. In normal chicks, the CEK4 and CEK8 eph-class receptor tyrosine kinases were expressed relatively heavily by the cochlear nerve ganglion, and CEK10 was expressed relatively heavily by the cochlear hair cell sensory epithelium. The results suggest that the FGF system may be involved in the response of the cochlear epithelium to ototoxic damage. The eph-class receptor tyrosine kinase CEK10 may be involved in cell interactions in the cochlear sensory epithelium, while CEK4 and CEK8 may play a role in the cochlear innervation.

Animals↗
PubMed1985

Retrolabyrinthine vestibular neurectomy with simultaneous monitoring of eighth nerve and brain stem auditory evoked potentials.

We have used retrolabyrinthine vestibular neurectomy in 36 of 49 cases as the primary surgical procedure to relieve vertigo. Most of the patients (46 of 49) had Meniere's disease. Results indicate that 71% (35 of 49) of the patients had no vertigo after the operation, while 22% (11 of 49) had much improvement. Hearing was maintained within 20 dB of the preoperative level in 78% (38 of 49) of the patients. During surgery in the last 23 patients, direct nerve potentials were recorded from the middle ear promontory and the intracranial cochlear nerve. Brain stem auditory evoked responses were simultaneously recorded in the last 10 patients. It appears that the intraoperative direct cochlear nerve potentials can be used as a sensitive monitor of trauma to the cochlear nerve during and after vestibular neurectomy. If the latency of the eighth nerve action potential changes less than 0.3 msec and the waveform does not change after vestibular neurectomy, there is an excellent chance that hearing at 1 month after surgery will be within 15 dB of the level before surgery. The retrolabyrinthine vestibular neurectomy has replaced the middle fossa vestibular neurectomy and the endolymphatic subarachnoid shunt procedure in our clinic.

Brain Stem↗
PubMed1979

Functional and histological findings in acoustic neuroma.

27 patients with acoustic neuroma were operated on by translabyrinthine tumor removal. At operation 8th nerve compartments were identified and removed for study. Results of the audiological test battery and vestibular tests were compared with histological state of the nerve specimens studied. The tumor appears only seldom to invade the cochlear nerve in cases with 'cochlear' hearing loss, but in the majority of cases with 'retrocochlear' hearing loss the cochlear nerve is invaded.

Cochlear Nerve↗
PubMed1994

The trajectory of the sympathetic nerve fibers to the rat cochlea as revealed by anterograde and retrograde WGA-HRP tracing.

Wheat germ agglutinin-horseradish peroxidase conjugate was injected in the unilateral superior cervical ganglion (SCG), and the projection pathways of postganglionic sympathetic nerve fibers innervating the cochlea were traced in the rat. The labeled axons advanced along the internal carotid artery (ICA), and a few advanced caudally in the major petrosal nerve (MPN) and entered the facial nerve, while the majority ran rostral to the pterygopalatine ganglion at the point where they crossed the MPN in the carotid canal. The rest of the labeled fibers remained on the surface of the ICA and advanced to the cranial cavity. Most of the labeled fibers along the facial nerve joined the cochlear nerve and finally reached the osseous spiral lamina through the spiral ganglion. Some of the labeled fibers ran along the anterior inferior cerebellar artery from the basilar artery which was previously thought to have been the only pathway. We could not find any labeled fiber on the modiolar artery from anterior inferior cerebellar artery in the cochlea. These observations are consistent with our hypothesis that the sympathetic fibers innervating the neural tissues or related structures follow nerve fibers and meninges as matrices of projection pathways rather than arteries.

Animals↗
PubMed1987

Audiologic diagnosis of central versus eighth nerve and cochlear auditory impairment.

122 subjects divided into four groups according to the site of lesion (cochlea, eighth nerve, brainstem and temporal lobe) were subjected to an audiometric test battery, including pure-tone sensitivity measures, recruitment testing, tone decay, Békésy audiometry, speech audiometry, stapedius reflex measures and auditory brainstem response (ABR) audiometry. The results were contrasted among the four groups by calculating several measures of test performance, including sensitivity, specificity, efficiency, A' (test performance) and plots on the receiver operating characteristic (ROC) space of pure positives versus false alarms. In the differential diagnosis between eighth nerve and cochlear site, the various measures did not rank the tests in the same order: (a) for efficiency: ABR, Békésy audiometry; (b) for A' (similarly to the analysis into the ROC space): ABR, recruitment, Békésy, stapedius reflex, speech audiometry, tone decay. In distinguishing an eighth nerve from a brainstem site, it is important to consider amount of hearing loss, presence of tinnitus, abnormal tone decay and Békésy audiometry patterns. ABR adds significant diagnostic efficiency only when waves II, III and V are detectable: a prolonged I-II interpeak interval (IPI) and a normal III-V IPI are characteristic of the eighth nerve site. ABR gives good diagnostic support in the intrinsic brainstem lesions by suggesting changes in the generator sites of the component waves. The audiometric diagnosis of temporal lobe lesions involving the auditory cortex still relies upon speech audiometry: tests specifically designed for this purpose by Bocca and Calearo and by Jerger - i.e. the 'sensitized sentences' and the identification of synthetic sentences under ipsi- or contralateral competing message - are commendable for their sensitivity and efficiency in distinguishing brainstem from temporal lobe sites. In brainstem sites, the most affected ear is ipsilateral to the lesion for ABR, but contralateral for speech audiometry.

Adolescent↗