Cochlear Nerve

Responses were compared before, during and after experimental manipulations including pharmacological blockade of the auditory nerve, section of the auditory nerve, section of the efferent nerves, removal of the cochlear nucleus, and focal cooling of the cochlear nerve and/or cochlear nucleus.  

In addition, we determined that neurofilaments of the vestibular nerve mature earlier than neurofilaments of the cochlear nerve.  

Over the last 10 years, we have extended the use of ABI to nontumor (NT) adults and children with cochlear or cochlear nerve malfunctions who would not or did not benefit from a cochlear implant (CI). Thirty-six had NF2 (34 adults and 2 children), and 78 (49 adults and 29 children) had NT cochlear and cochlear nerve disorders.  

An absent cochlear nerve (CN) is a contraindication to cochlear implantation. Recently, some authors have reported the relationship between cochlear nerve canal (CNC) stenosis and CN hypoplasia. MATERIALS AND METHODS: During a period of 78 months, 21 children (42 ears) with unilateral or bilateral sensorineural hearing loss underwent both HRCT and MRI of the cochlear nerve.  

OBJECTIVE: Microvascular compressions of the cochlear nerve can lead to tinnitus. Decompressing the cochlear nerve may result in improvement in tinnitus if the auditory nerve is not too damaged for recovery. MATERIALS AND METHODS: Twenty patients undergo a microvascular decompression of the vestibulocochlear nerve for unilateral intractable tinnitus. CONCLUSION: Microvascular decompression of the cochlear nerve can improve tinnitus intensity in selected patients if decompression is performed early, before the end of the 4th year.  

We developed a cochlear nerve action potential (CNAP) monitoring technique using a microdissector and compared the results of CNAP and auditory brainstem response (ABR) monitoring.  

No child with cochlear nerve deficiency (CND) in their implanted ear achieved open-set speech perception abilities.  

We describe a case of successful identification and functional preservation of facial and cochlear nerves in a patient with acoustic neuroma.  

PURPOSE: We aimed to determine any differences, if present, between the cross-sectional area of the cochlear nerve (CN) of elderly patients with sensorineural hearing loss (SNHL) and of young patients with normal hearing.  

CONCLUSIONS: Malformation of inner ear with the developed cochlear nerve nowadays is the indication for CI.  

Modern magnetic resonance imaging has significantly improved the diagnosis of cochlear nerve deficiencies. We report the case of a 3-year-old girl with unilateral cochlear nerve aplasia, normal middle and inner ear anatomy, and an absence of otoacoustic emissions, all of which erroneously suggested cochlear damage.  

The width of the second turn of the cochlea (CW), the cochlear height (CH), and the width of the bony canal for the cochlear nerve (WCN) were measured on a reference plane containing the modiolus, the posterior semicircular canal, the footplate, and the stapes arch.  

OBJECTIVE: Hearing loss after removal of vestibular schwannomas with preservation of the cochlear nerve can result from labyrinthine injury of the posterior semicircular canal and/or common crus during drilling of the posterior wall of the internal auditory meatus.  

Lesion studies of the olivocochlear efferents have suggested that feedback via this neuronal pathway normally maintains an appropriate binaural balance in excitability of the two cochlear nerves (Darrow et al., 2006). If true, a decrease in cochlear nerve output from one ear, due to conductive or sensorineural hearing loss, should change cochlear nerve response in the opposite ear via modulation in olivocochlear feedback.  

Here, we show, using cochlear functional assays and confocal imaging of the inner ear in mouse, that acoustic overexposures causing moderate, but completely reversible, threshold elevation leave cochlear sensory cells intact, but cause acute loss of afferent nerve terminals and delayed degeneration of the cochlear nerve.  

CONCLUSION: It is recommended that CM testing be carried out routinely in children with severely abnormal click ABRs so as not to miss out AN; Behavioral hearing can not be predicted by auditory evoked responses; if audiological profile of AN is detected, further MRI exploration of well-developed cochlear nerve is necessary..  

CONCLUSION: Multi-channel cochlear implantation can be performed in patients with inner ear malformation, but should not be attempted in patients with poor cochlear and cochlear nerve development.  

Type I neurons make up 90-95% of the cochlear nerve and contact single inner hair cells to provide acoustic analysis as we know it.  

RESULTS: Intraoperative brainstem auditory evoked potential monitoring, direct cochlear nerve action potential monitoring, and facial nerve electromyography are the main tools used to assess the functional integrity of an anatomically intact cranial nerve.  

Presbycusis, or the aging ear, involves mainly the inner ear and the cochlear nerve, causing sensorineural hearing loss.  

Eight patients (1.2%) had poor SDS that appeared to be out of proportion to the degree of hearing loss depicted by the postoperative PTA thresholds, suggesting retrocochlear or cochlear nerve pathology (group 3).  

Surgically the lesion was attached to the cochlear nerve. Pathological evaluation revealed what is best described as an angiolipomatous hamartoma of the cochlear nerve.  

The degree of overlap among cochlear nerve fibers stimulated by different electrodes results in electrode interaction, which has been shown to have a significantly deleterious effect on speech recognition performance in multi-electrode cochlear implant users.  

MRI findings that convey important information for hearing-preservation VS surgery are: length of tumor-cochlear nerve contact, involvement of the internal auditory canal, incomplete filling of internal auditory canal, tumor size less than 15 mm and the intralabyrinthine signal intensity on 3DFT-CISS gradient-echo images.  

OBJECTIVES: Deficient cochlear nerves (CN) have been associated with poor cochlear implant performance. In 7% of ears, the cochlear nerve was unable to be measured secondary to the proximity of the CN to IAC wall.  

It has been believed to be associated with congenital sensorineural hearing loss and to be a result of aplasia or hypoplasia of the vestibulocochlear nerve or the cochlear branch. In previously presented cases and in our case, the separated small canals were vacant and without a cochlear nerve fiber.  

Previous work in our laboratory suggested that NT3 and its receptor TrkC in the mouse cochlear nucleus (CN) may be involved in directing neuronal migration and initial targeting of inputs from cochlear nerve axons in the embryo.  

Hearing loss has been attributed to many factors, including degeneration of sensory neurons in the auditory pathway and demyelination along the cochlear nerve. Furthermore, the contribution of glial cells, which myelinate the cochlear nerves, is poorly understood.  

BACKGROUND AND PURPOSE: cochlear nerve deficiency (CND), including aplasia and hypoplasia, is a rare cause of congenital hearing loss.  

OBJECTIVES: We analyzed whether radiographically demonstrated anterior inferior cerebellar artery (AICA) vascular compression of the cochleovestibular nerve in asymmetric hearing loss could be correlated to either the symptomatic ear or to cochlear nerve diameter. The cross-sectional area of the cochlear nerve was measured. RESULTS: Symptomatic ears could be correlated to a decreased cochlear nerve diameter, but not to the degree of AICA penetration into the internal auditory canal. CONCLUSIONS: AICA vascular compression of the cochleovestibular nerve does not appear to correlate to hearing loss or to cochlear nerve diameter. The finding of decreased cochlear nerve diameter in symptomatic ears implies an alternative mechanism for asymmetric hearing loss..  

The aim of this study was to define the effect on tinnitus of tumor removal, cochlear nerve resection, and useful hearing preservation in patients with VSs. In the 171 patients with preoperative tinnitus, the cochlear nerve was resected in 85 (49.7%) and preserved in 86 (50.3%), but there was no significant difference in the incidence of postoperative tinnitus between these 2 groups (p = 0.293). Among those without preoperative tinnitus, the cochlear nerve was resected in 45 cases (63.4%) and tinnitus appeared postoperatively in 3 (6.7%). CONCLUSIONS: Tumor removal via the retrosigmoid lateral suboccipital approach may provide some chance for improvement of tinnitus in patients with VSs; however, neither cochlear nerve resection nor useful hearing preservation affects the postoperative development of tinnitus..  

OBJECTIVES: To describe the importance of imaging with the use of magnetic resonance (MR) or computed tomography (CT) during the diagnostic workup of a patient with sensorineural hearing loss to determine the status of the cochlear nerve. METHODS: A pediatric database was used to find patients with diagnoses of absent cochlear nerve. Four patients were excluded because they had absence of the entire inner ear structures ipsilateral to the aplastic cochlear nerve (two cases) and because they had multiple congenital anomalies (two cases). CONCLUSIONS: Agenesis of the cochlear nerve may be more common than previously thought, especially in an otherwise healthy, nonsyndromic, school-aged child.  

CONCLUSIONS: The results indicate that successful hearing preservation surgery in large VSs is possible with meticulous technique and attention to adhesions between the tumor and the cochlear nerves..  

Data concerning tumor size (Stage 1, intracanalicular; Stage 2, < or =15 mm in the cerebellopontine angle [ CPA]; Stage 3, 15-30 mm in the CPA; and Stage 4, >30 mm in the CPA), intraoperative facial nerve displacement (Type 1, anterior to the tumor; Type 2, anterior and superior to the tumor and separated from the cochlear nerve; Type 3, superior to the tumor; and Type 4, posterior to the tumor), degree of tumor adhesion (weak, intermediate, and strong) and postoperative facial function according to the House and Brackmann classification at days 10, 30, 90 and 180 were collected.  

The auditory pathways are a system of afferent fibers (through the cochlear nerve) and efferent fibers (through the vestibular nerve), which are not limited to a simple information transmitting system but create a veritable integration of the sound stimulus at the different levels, by analyzing its three fundamental elements: frequency (pitch), intensity, and spatial localization of the sound source.  

Hearing and cochlear nerve exploration can be carried out using three principal methods: pure-tone and speech audiometry, evoked otoacoustic emissions (EOAEs), and brainstem auditory evoked potentials (BAEPs). CONCLUSION: Auditory functional assessment is essential for optimal care of tumor or functional pathologies involving the cochlear nerve and/or the cerebellopontine angle..  

Critical complications arising during MVD surgery are the stretching of the VIII nerve - the main cause of hearing loss - labyrinthine artery manipulation, direct trauma with instruments, or a nearby coagulation, and at end of the surgery neocompression of the cochlear nerve by the prosthesis positioned between the conflicting vessel(s) and the VIIth-VIIIth nerve complex.  

OBJECTIVES: There are a significant number of children who do not show any auditory development with a cochlear implant (CI), possibly due to cochlear nerve (CN) aplasia/hypoplasia.  

The nerve has two components, the vestibular nerve, that detects head and body motion, and the cochlear nerve that detects sound.  

Neuroimaging identified hypomyelination and cochlear nerve aplasia. This case represents the first description of aplasia of the cochlear nerve due to a SOX10 mutation..  

Absent cochlear nerves were remarkably common, being found in eight patients (73%). CONCLUSIONS: cochlear nerve aplasia appears by far the most common cause of UNHL in children.  

Enhancement of the CSF space in the IAC fundus was seen in all but two subjects: one had enlarged endolymphatic duct and sac syndrome (EEDS), and the other had cochlear nerve agenesis.  

With single-dose SRS, critical hearing preservation variables include: 1) strict attention to prescription dose 3D conformality so that the ventral cochlear nucleus (VCN) receives cochlear nerve when visualizable with contrast-enhanced T2-weighted MR volumetric imaging techniques and exclusion the dura mater of the anterior border of the internal auditory canal; 3) a tumor margin dose prescription

More recently, cochlear implantation has been used in selected cases of NF-2, following tumor removal, where the patient is left with bilateral profound hearing loss but with anatomical continuity of the cochlear nerve. In the setting of a negative fast auditory brainstem response (ABR), but preserved cochlear nerve action potential (CNAP), the option of a CI can be considered. To this end we propose that a multicenter trial be undertaken to further elucidate the role of intraoperative monitoring to determine the functional preservation of the cochlear nerve..  

RESULTS: Average age of patients with professional damage of cochlear nerve was 50 y.  

Although cochlear implant is the treatment of choice, current evidence show that it benefits only those patients with endocochlear lesions, but not those with cochlear nerve deficiency or central nervous system disorders.  

A cytoreductive surgery was performed and the cochlear nerve was preserved. She then underwent removal of the right VS stage III with no possible preservation of the cochlear nerve.  

We have introduced a newly designed intracranial electrode enabling continuous monitoring of the cochlear nerve compound action potential (CNAP).  

Concurrently, neurological deterioration involving trigeminal, facial, and cochlear nerve functions were also assessed.  

Patients presented most commonly with deficits of the vagus nerve, followed by vestibular/cochlear nerve and glossopharyngeal nerve deficits.  

OBJECT: The authors analyzed the tumor capsule and the tumor-nerve interface in vestibular schwannomas (VSs) to define the ideal cleavage plane for maximal tumor removal with preservation of facial and cochlear nerve functions. In specimens of tumors removed en bloc with the cochlear nerves, the authors found that the connective tissue layer, corresponding to the perineurium of the cochlear nerve, clearly bordered the nerve fibers and tumor tissue. CONCLUSIONS: Based on these histological observations, complete tumor resection can be achieved by removal of both tumor parenchyma and tumor capsule when a clear border between the tumor capsule and facial or cochlear nerve fibers can be identified intraoperatively. Conversely, when a severe adhesion between the tumor and facial or cochlear nerve fibers is observed, dissection of the vestibular nerve-tumor interface (the subcapsular or subperineurial dissection) is recommended for preservation of the functions of these cranial nerves..  

To evaluate its potential, the authors examined waterjet dissection of the vestibulocochlear nerve in rats. METHODS: Lateral suboccipital craniectomy and microsurgical preparation of the vestibulocochlear nerve were performed in 42 rats. RESULTS: In using up to 6 bar, the cochlear nerve was preserved in all cases.  

RESULTS: The anatomical integrity of the cochlear nerve was preserved in 75.8% of the cases.  

MAIN OUTCOME MEASURE: Identification of an abnormality of the intracranial contents, inner ear, and cochlear nerve. Forty-nine of 271 ears (18%) with SNHL demonstrated an either absent (26/49 [ 53%]) or deficient (23/49 [ 47%]) cochlear nerve. The most common abnormalities seen were an abnormal cochlea and abnormal cochlear nerve.  

cochlear nerve aplasia (as evidence of only one existing nerve in three dimensional magnetic resonance imaging) and hypoplastic cochleas are among the most difficult cases and sometimes children are considered unsuitable for cochlear implantation.  

Viability of cochlear nerve and spiral ganglion following radiation is questioned.  

The findings include absent semicircular canals, narrow orifice for the cochlear nerve, and abnormalities of the oval and round window, the facial canal and the ossicles.  

This method takes advantage of the refractory properties of the cochlear nerve, combining the responses to different types of stimulation pulses in order to obtain the biological response free of artifact.  

Alexa Fluor 568-labeled bovine serum albumin (BSA) was applied to round window membranes as a tracer to explore the cochlear distribution of drug delivery and was detected in the lateral wall, spiral ganglion, cochlear nerve, and organ of Corti.  

Brainstem auditory evoked potentials (BAEPs) were routinely used to monitor cochlear nerve function during these operations.  

Their sensory function is poorly understood because their afferent innervation, the type-II spiral ganglion cell, has small unmyelinated axons and constitutes only 5% of the cochlear nerve.  

PURPOSE: The aim of this study was to evaluate the diameters of the various bony canals of the inner ear in patients with sensorineural hearing loss (SNHL) and establish criteria for detecting hypoplasia of the bony canal of the cochlear nerve. RESULTS: The diameter of the bony canal of the cochlear nerve was significantly smaller in affected ears than in unaffected ears (P < 0.01). CONCLUSIONS: Most (60%) of the patients with unilateral SNHL showed a significant difference in the diameters of the bony canals of the cochlear nerve between the affected and unaffected sides; moreover, the mean value was significantly smaller in affected ears.  

High magnification failed to demonstrate any meningeal cleavage plane between the facial or cochlear nerve and the tumor.  

Dopamine (DA), another transmitter of the lateral olivocochlear (LOC) efferents making synapses on cochlear nerve dendrites, controls auditory nerve activation and protects the sensory nerve against overactivation.  

In primary rat cochlear nerve cells, simvastatin decreased staining for NF200, a neuro-cytoskeletal protein.  

In the auditory pathway, the formation of GFAP aggregates was observed only in GFAP-positive cells of the cochlear nerve. Transgenic mice showed more severe ABR deficits and OHC damage, suggesting that cochlear nerve glial cells with GFAP aggregates play a role in noise susceptibility. Thus, we should focus more on the roles of cochlear nerve glial cells in SNHL..  

METHODS: A consecutive series of 31 cases in 30 patients with medial VSs (mean size 31 mm) who underwent surgery between 1997 and 2005 via a suboccipitolateral route was evaluated with respect to pre- and postoperative cochlear nerve function, extent of tumor removal, and radiological findings. CONCLUSIONS: The cochlear nerve in medial VSs requires special attention due to the atypical intracisternal growth pattern. Even in large tumors, hearing could be preserved in 37% of cases, since the cochlear nerve in medial schwannomas may not exhibit the adherence to the tumor capsule seen in tumors with comparable size involving the internal auditory canal..  

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