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 811 records · Page 45Linked to original sources
PubMed1997

Wolfram syndrome: a neuropathological study.

Neuropathological examination was carried out on a patient aged 37 years who had suffered from Wolfram syndrome. Atrophy of the olfactory bulbs and tracts, atrophy of the optic nerves and chiasm, loss of neurons in the lateral geniculate nuclei mainly affecting the small cell layers, atrophy of the superior colliculus, loss of fibers in the cochlear nerve and mild loss of neurons in the cochlear nuclei and inferior colliculus, mild olivopontocerebellar atrophy, and demyelination of the pyramidal tracts were the main neuropathological findings. These correlated with anosmia, loss of vision, loss of hearing, cerebellar symptoms and signs, Babinski sign, and clonus, respectively, clinically observed in this patient. Mild neuron loss and gliosis in the preoptic and paraventricular area of the hypothalamus and mild motor neuron loss in the spinal cord did not reach thresholds of impaired function, although loss of neurons in discrete bulbar nuclei might have accounted for the late episode of food aspiration and suffocation. The relationship between memory loss, personality disturbances, and signs of prefrontal release and mild loss of neurons in the anterior and dorso-medial nuclei of the thalamus remains unclear.

Adult↗
PubMed2001

Cochlear schwannomas.

In a series of 179 cerebellopontine angle (CPA) tumors, the authors present nine cases (5%) that were cochlear nerve neuromas. There were six men and three women (mean age, 51 years). Preoperative magnetic resonance imaging confirmed the diagnosis in one case with a labyrinthine extension and raised suspicions in the other four cases, which were confirmed during surgery. The remaining neuromas were discovered intraoperatively. The mean time between first observation and surgery was 9 months. Preoperatively, all patients underwent a complete otoneurological assessment. The middle fossa approach was used for the patient with the labyrinthine extension, and the retrosigmoid approach was used for the other eight cases. In all patients facial nerve function was preserved. Sudden or major hearing loss without associated vestibular symptoms or preoperative facial paralysis may be predictive of a cochlear component of a CPA tumor. The near-field relationships of cochlear neuromas located at the level of the acoustic and facial nerves can be appreciated because of their small size and strong contrast enhancement.

Journal Article↗
PubMed1987

Catecholamine content of cochlear and facial nerves. High-performance liquid chromatography analyses in normal and mutant mice.

The catecholamine content in cochlear and facial nerves was determined using high-performance liquid chromatography coupled with electro-chemical detection. Minute amounts of norepinephrine were detected in both nerves in normal CBA/CBA mice and homozygotic jerker mouse mutants, whereas norepinephrine was found only in the facial nerve in the dancer heterozygotic mouse mutant. Dopamine and epinephrine were not detected in any of the mouse strains.

Animals↗
PubMed1996

The anatomy of the cochlear nuclei and superior olivary complex of arboreal Australian marsupials.

Cytoarchitectural and morphometric analyses were carried out on the cochlear nuclear and superior olivary complexes of nine representative possums and gliders, members of a large group of nocturnal, arboreal Australian marsupials, many of which have well developed vocalizations. The cochlear nuclear complex was displaced medial to the restiform body in all species; this has previously been reported in other marsupials. The dorsal cochlear nucleus was generally very much larger than any other nucleus in this complex. A small cochlear nerve root nucleus was present in all species, a feature shared with rodents. The anteroventral cochlear nucleus was present throughout almost the entire rostrocaudal extent of the complex. The component nuclei of the superior olivary complex had similar positional relationships to those in eutherians. The lateral superior olive was the largest nucleus, having a volume usually greater than the sum of the volumes of the medial superior olive and medial nucleus of the trapezoid body. The smaller species had a very much larger number of neurons in the superior olive relative to brain size than did the larger species. A similar disproportion was demonstrated between cochlear nucleus volume and brain weight.

Animals↗
PubMed1990

Selectively eliminating cochlear microphonic contamination from the frequency-following response.

The frequency-following response (FFR) is the scalp recorded response to low frequency stimuli. As an electrophysiological method for determining auditory threshold, it has application in both clinical and research settings. However, the response is often contaminated with the cochlear microphonic (CM), reflecting the response of outer hair cells, rather than neural generators (i.e., auditory nerve, cochlear nucleus, superior olivary nucleus, inferior colliculus, etc.). The FFR needs to be a purely neural response to establish its clinical and experimental usefulness. The methods applied to date have failed to accomplish this. The present study demonstrates a method of deriving a pure neural response by subtracting a forward masked FFR, which contains only CM, from an unmasked FFR. To confirm that the residual response after forward masking is solely CM, one needs to record two forward masked responses with opposite phase probe stimuli. When the responses are added they will sum to zero only if the residual response with forward masking is pure CM. This study demonstrates that the traditional method for removing CM from FFR, by simple summation of unmasked responses recorded with stimuli of opposite phase, does not accurately reflect the amplitude or frequency of the FFR, while the proposed method provides an accurate assessment of the FFR amplitude free of CM contamination.

Acoustic Stimulation↗
PubMed2005

Spatiotemporal patterns of neuronal programmed cell death during postnatal development of the gerbil cochlea.

During early postnatal development, afferent neurons of the cochlear (spiral) ganglion progressively refine their projections to auditory hair cells so that, by hearing onset, most cochlear nerve fibers innervate a single hearing receptor. One mechanism that might contribute to these changes in cochlear innervation is the programmed cell death (apoptosis) of developing neurons within the spiral ganglion. In the present study, we used the TUNEL method and morphological criteria to identify apoptotic cells within the spiral ganglion of the Mongolian gerbil during the first week of postnatal life when afferent projections to the cochlea are actively refined in this species. The locations of individual apoptotic spiral ganglion cells were mapped onto three-dimensional reconstructions of the entire ganglion for an age-graded series of gerbils to produce the first high-resolution, spatiotemporal maps of apoptotic ganglion cell death for the postnatal cochlea. We observed a significant increase in apoptosis in the spiral ganglion from postnatal day (P) 4 through P6. During this time, the most intense apoptotic activity occurred in regions of the spiral ganglion providing innervation to the lower middle and apical turns of the cochlea. The time course and regional variation of programmed cell death within the developing gerbil spiral ganglion are discussed in terms of the postnatal refinement of cochlear innervation and its possible functional significance for hearing in gerbils.

Age Factors↗
PubMed1991

Intraoperative cranial nerve monitoring during posterior skull base surgery.

Intraoperative monitoring of neurophysiologic function is rapidly evolving as an important adjunct during skull base surgery to reduce the incidence of neurologic deficit. Facial nerve monitoring is an excellent model, since electrical and mechanical evoked potentials can be directly presented to the surgeon in real-time through an acoustic loudspeaker display. The lower cranial nerves may also be monitored using similar electromyographic techniques. Auditory system monitoring is more difficult due to the low amplitude response that requires averaging and filtering to extract the evoked potential. In conjunction with auditory monitoring, improved hearing preservation may be further enhanced by concomitant facial nerve monitoring, since the surgeon is alerted to traumatic manipulations that may affect both facial and cochlear nerves. Techniques and interpretative issues are presented to maximize the efficacy and safety of cranial nerve monitoring.

Journal Article↗
PubMedDate not supplied

Contrast-enhanced CISS MRI of vestibular schwannomas: phantom and clinical studies.

PURPOSE: The purpose of this work was to assess the changes of signal intensity on constructive interference in steady state (CISS) 3D Fourier transformation (3DFT) MRI after administration of Gd-DTPA and to evaluate the efficacy of contrast-enhanced CISS-3DFT MRI to depict the seventh and eighth cranial nerves affected by vestibular schwannomas. METHOD: All scans were carried out on a 1.5 T MR unit. First, an experimental study was conducted to evaluate the changes in signal intensity of the CISS-3DFT sequence in relation to the concentration of contrast medium. Second, nine consecutive patients with 11 vestibular schwannomas underwent CISS-3DFT imaging before and after contrast agent administration. Signal intensities of the tumors and nerves were measured and compared between the pre- and postcontrast images. Visualization of the facial and cochlear nerves was rated on pre- and postcontrast CISS imaging independently. RESULTS: On the phantom study, the CISS-3DFT sequence showed a constant increase in signal intensity as the concentration of Gd-DTPA increased. The contrast between the nerves and tumors significantly increased after contrast agent administration (from 0.1 to 9.0 as mean contrast-to-noise ratio). The ability to depict the nerves was also significantly higher for postcontrast CISS-3DFT imaging than for precontrast. CONCLUSION: Although the CISS-3DFT sequence offers similar contrast as other heavily T2-weighted sequences, the signal intensity of contrast-enhanced tumors increased on CISS-3DFT imaging. Contrast-enhanced CISS imaging was valuable for evaluating the seventh and eighth cranial nerves affected by vestibular schwannomas.

Adult↗
PubMed2005

Tumors of the jugular foramen: diagnosis and management.

OBJECTIVE: Jugular foramen tumors are rare cranial base lesions that present diagnostic and management difficulties. With the availability of new diagnostic procedures these tumors have been more precisely studied and questions of whether, when, and how these lesions should be treated often arise. Data from 106 consecutive patients surgically treated in the past 17 years were retrospectively analyzed to identify surgical outcomes. METHODS: The tumors were approached by a multidisciplinary team composed of neurosurgeons, ear, nose, and throat surgeons, and neuroradiologists. Hypervascular lesions were embolized 3 to 5 days before surgery. The same surgical technique was used to resect all tumors. The surgical defect was covered with vascularized myofascial flaps. The internal carotid artery was infiltrated in two patients, and a saphenous graft bypass was carried out before removal of the lesions. The facial nerve was reconstructed with nerve grafts (great auricular nerve) or XII/VII anastomosis in five cases. Postoperative radiotherapy was carried out for malignant and invasive tumors. RESULTS: Paragangliomas were the most frequent lesions, followed by schwannomas and meningiomas. Complete excision was possible in 89% of benign tumors and 80% of paragangliomas. Lower cranial nerve deficit was the most frequent complication (10 patients, 9.4%), transient in 4 patients. Facial and cochlear nerve paralysis occurred in 8 patients (7.5%). The function of the facial nerve recovered spontaneously in 3 patients. Four patients (3.7%) developed postoperative cerebrospinal fluid leakage. Four patients (3.7%) died after surgery. CONCLUSION: Radical removal of benign jugular foramen tumors is the treatment of choice and may be curative. Large lesions can be radically excised in one surgical procedure with preservation of lower cranial nerves. Cranial base reconstruction with vascularized myofascial flaps reduces the incidence of postoperative cerebrospinal fluid leakage. Damage of the lower cranial nerves is the most serious surgical complication.

Adolescent↗
PubMed1999

[Unilateral neurosensory hearing loss as a manifestation of multiple sclerosis].

Sensorineural hearing loss is an uncommon symptom of multiple sclerosis (MS). We report a patient with confirmed MS in which sudden unilateral hearing loss was the main manifestation of an episode. Auditory findings, including the auditory-evoked brainstem potentials, suggested impairment of the distal tract of the right VIII cranial nerve. Clinical and electrophysiological abnormalities disappeared with steroid therapy. Acute inflammatory demyelinative lesions of the peripheral cochlear nerve may cause acute hearing loss in MS.

Adult↗
PubMed1999

Auditory brainstem responses, electrocochleograms, and cochlear microphonics in the myelin deficient mutant hamster 'bt'.

Electrophysiological studies of the auditory pathway were performed on the mutant hamster 'bt' which is known to have myelin deficiencies in the central nervous system. Auditory brainstem responses (ABRs), electrocochleograms (EcochGs), and cochlear microphonics (CMs) were recorded. ABRs in 'bt' demonstrated markedly transformed waveforms with significantly prolonged latencies. EcochG in 'bt' showed significantly prolonged N1 latencies of the compound action potentials (CAPs) while 'bt' showed normal CMs. The myelin deficient mutant hamster 'bt' may have myelin deficiencies not only in the brainstem auditory pathway but also in the cochlear nerve.

Animals↗
PubMed1989

Computer-generated three-dimensional reconstruction of the cochlea.

Computer-generated three-dimensional reconstructions of the nerve fibers from the organ of Corti to the spiral ganglion were used to determine the optimum maximal length of the cochlear implant electrode. The spiral ganglion within the modiolus is much shorter than the organ of Corti. The spiral ganglion has 1 3/4 turns and reaches no higher than the middle of the second turn of the organ of Corti, which has 2 3/4 turns. The spiral ganglion is concentric and basal with respect to the organ of Corti. The spiral ganglion dendrites within the osseous spiral lamina of the basal turn project radially, nearly perpendicular to the central axis of the modiolus. Upon entering the modiolus, they turn basally at an angle of approximately 120 degrees. The projection of dendrites within the osseous spiral lamina became increasingly oblique as the ganglion extended apically. The organization of the cochlear nerve results from the spiraling of the ganglion. These findings are in agreement with previous reports. Implications of these findings and their possible relevance to the optimum length of the cochlear implant electrode are discussed with reference to cochlear damage resulting from longer electrodes.

Cochlea↗
PubMed2001

Immunohistochemical localization of nitric oxide synthase and soluble guanylyl cyclase in the ventral cochlear nucleus of the rat.

The diffusible messenger nitric oxide (NO) is implicated in auditory processing. It acts in the brain largely through activation of soluble guanylyl cyclase (sGC), a heterodimer comprised of alpha and beta subunits. The authors used immunohistochemistry to study the NO/guanosine 3',5'-cyclic monophosphate (cGMP) pathway in the cochlear nucleus of Sprague-Dawley rats. Central fibers of the cochlear nerve were stained for neuronal nitric oxide synthase (NOS-I) but not for sGCbeta. Within the ventral cochlear nucleus, a large fraction of principal cells were immunopositive for both NOS-I and sGCbeta; these cells could be seen at times receiving contacts from NOS-I-positive fibers. sGC staining of somatic cytoplasm extended into the distal dendritic tree. At variance with this pattern, NOS-I was concentrated mainly in somata. Double-labeling experiments showed that most of the principal neurons expressed both antigens. By contrast, in the granule cell domain, small cells that were immunopositive for NOS-I rarely corresponded to those that were immunopositive for sGC. To assess whether NOS-I and sGC immunoreactivities colocalize with their respective catalytic activities, the authors performed multiple labeling with L-citrulline (a by-product of the formation of NO from L-arginine) and cGMP, respectively. L-citrulline was restricted to NOS-I-positive elements, and the large majority of NOS-expressing neurons were positive for citrulline. Multiple labeling revealed that almost all sGC-positive neurons also accumulated cGMP both in the ventral cochlear nucleus and in the granule cell domain. These data suggest that NO is a signaling molecule in the cochlear nucleus, perhaps functioning in both a paracrine manner and an autocrine manner.

Animals↗
PubMed1989

[Function-saving microsurgery in suboccipital removal of large acoustic neuromas].

Various successful approaches are available for acoustic neurinoma surgery, permitting total tumor removal and preservation of cranial nerve function. In smaller and medium sized tumors excellent results can be achieved with respect to facial and cochlear nerve function using the transtemporal approach. For larger tumors similar results can be achieved by the suboccipital approach. The results of 45 completely removed large acoustic neurinomas all operated upon via the suboccipito-lateral approach with microsurgical techniques and neurophysiological monitoring are presented. The average tumor size, excluding the portion within the internal auditory canal was 3 cm. Anatomical preservation of the VIIth cranial nerve was achieved in nearly all cases. Satisfactory to excellent facial nerve function was preserved in 70% of all cases. Initial hearing was preserved in 29%. However delayed postoperative hearing loss was encountered in 13%. Therefore definite hearing preservation was achieved in 16% of the cases. Intraoperative monitoring, especially of auditory evoked potentials, was very helpful in achieving these functional results.

Adult↗
PubMed1995

Responses of dorsal cochlear nucleus single units to electrical pulse train stimulation of the auditory nerve with a cochlear implant electrode.

In response to 100-ms duration electrical stimulation within the range 50-400 pulses per second (pps), and at 1.6- to 2.4-mA stimulus current, a range of poststimulus time histogram (PSTH) patterns were observed from dorsal cochlear nucleus (DCN) units, they were usually primarylike, onset or "negative response" and occasionally buildup or pauser patterns. It appeared that the excitatory and suppressive processes, also termed neural drives, in response to 2.5-pps electrical stimulation were the main determinants of DCN unit responses to 50- to 400-pps stimulation. This was demonstrated by a model of DCN responses to electrical stimulation of the auditory nerve. The neural drives required to model the PSTH patterns were (i) an excitatory process with a latency of < 5 ms, (ii) a second excitatory process latency of 4.5-10 ms, (iii) a long acting suppressive process with a latency of < 15 ms and a duration of > 70 ms, (iv) a short acting suppressive response with a latency of 2.5-3.7 ms and a duration usually < 5 ms, but always < 20, and (v) a drive contributing spontaneous activity to the unit. In addition to these processes which were observed at 2.5 pps, an additional, transient suppressive process was postulated to operate only at 50-400 pps. It was postulated that the PSTH patterns observed were due to differences in the strengths of these drives between units.

Animals↗
PubMed2006

Innervation of the apical turn of the human cochlea: a light microscopic and transmission electron microscopic investigation.

HYPOTHESIS: A light and transmission electron microscopic investigation of the apical turn of a freshly fixed human cochlea. BACKGROUND: Our knowledge about the human cochlea rests to a large extent on animal species research. An opportunity to obtain tissue from normal-hearing persons occurs during surgery for life-threatening petroclival meningioma. This study presents detail on the morphology and innervation of the apical part of the human cochlea using light microscopic and transmission electron microscopic level sectioning. METHODS: The tissue was histologically processed after removal during petroclival meningioma surgery. The cochlea was serially sectioned perpendicularly to its long axis, and at regular distances semithin sections were reembedded and prepared for transmission electron microscopy. Nerve fibers/fascicles were traced from the area of the spiral ganglion to the level of the inner hair cells, and a cochleotopic "map" of the cochlear nerve supplying the apical portion was constructed. RESULTS: The apical turn was found to be innervated by 3,694 myelinated nerve fibers representing approximately 10% of the total number of fibers innervating the cochlea. The total number of unmyelinated nerve fibers was 513. The majority belonged to the efferent olivocochlear system and the intraganglionic spiral bundle or represented Type II afferent neurons innervating outer hair cells. CONCLUSION: The significance of the anatomic findings in relation to cochlear implantation is discussed.

Adult↗