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At least 919 records · Page 51Linked to original sources
PubMed1997

Localization of secretory phospholipase A2 in mouse cochlear tissues and cultured cells.

OBJECTIVE: To localize the expression of secretory phospholipase A2 (sPLA2) in the cochlear duct. DESIGN: By means of an immunocytochemistry technique that used rabbit anti-porcine pancreatic phospholipase A2 antiserum, sPLA2 sites were identified in vivo and in vitro in the adult mouse cochlear duct. SUBJECTS: Eight C57BL/6N normal adult male mice (11-12 weeks old) (6 mice for the in vivo study, 2 mice for the in vitro study). RESULTS: Different patterns of immunostaining for sPLA2 were observed in tissues of the cochlear duct. High levels of sPLA2 were detected in the following areas: the basal cells of the stria vascularis, the organ of Corti, the spiral ganglion, and the cochlear nerve; moderate levels of sPLA2 were found in the suprastrial and poststrial portions of the spiral ligament; low levels of sPLA2 were observed in the marginal and intermediate cells of the stria vascularis and the infrastrial portion of the spiral ligament. Immunoreactivity for sPLA2 also was detected in cultured marginal cells of the stria vascularis and in fibrocytes of the spiral ligament. CONCLUSIONS: Secretory phospholipase A2 is present in mouse cochlear tissues and individual cultured cells. These results suggest that the levels of sPLA2 expression in the cochlear duct are cell specific.

Animals↗
PubMed2006

MRI of the vestibular nerve after selective vestibular neurectomy.

CONCLUSION: In patients with Ménière's disease and persisting vertigo attacks after vestibular neurectomy (VNx) MRI of the vestibulocochlear nerve can identify residual vestibular nerve fibres that could be responsible for the vertigo attacks. OBJECTIVE: To test if MRI of the vestibulocochlear nerve can corroborate the presence of residual vestibular nerve fibres in patients with persisting vertigo attacks and residual vestibular function after VNx. MATERIALS AND METHODS: Vestibulocochlear nerve bundles of seven post-VNx unilateral Ménière's patients were imaged using 1.5 Tesla MRI with steady state free precession (SSFP) sequences. Reformatted MR images orthogonal to the vestibulocochlear nerve axis in internal auditory canal were compared on the VNx and intact sides. Vestibular function was assessed with caloric tests, three-dimensional head impulse tests and vestibular evoked myogenic potentials. Of the seven patients only one was asymptomatic (totally free of vertigo); six had continued to experience vertigo attacks, albeit not as long or as severe as before VNx. RESULTS: On the VNx side, MRI showed intact facial and cochlear nerves in all seven patients. In the six symptomatic patients, although superior and inferior vestibular nerve bulk and signal were reduced, residual bulk suggestive of inferior vestibular nerve was evident, correlating with evidence of residual posterior canal function on impulsive testing in all six symptomatic patients. In the asymptomatic patient, superior and inferior vestibular nerves were absent on MRI and impulsive testing revealed no residual posterior canal function.

Adult↗
PubMed1985

Problems in interpreting abnormal auditory brainstem responses in comatose patients.

Auditory brainstem responses (ABRs) provide a way to evaluate central nervous system function in young, confused, uncooperative or comatose patients. Auditory brainstem responses represent activity in or around the vestibulocochlear (VIII) cranial nerve, cochlear nucleus, superior olivary complex, lateral lemniscus, and inferior colliculus. Many factors affect recording of the auditory brainstem response. These factors include technical factors, chronic alcoholism, demyelinating diseases, ototoxic drugs, barbiturates, hearing loss, otitis media, and hypothermia.

Brain Stem↗
PubMed1990

[The mechanism of speech perception using multichannel cochlear implant].

The mechanism of speech perception in patients with Australian multi-channel cochlear implant was investigated. 1) Vowel recognition abilities of patients were sufficient with this implant, whereas, consonant recognition abilities were insufficient. 2) Although the cochlear hair cells were functionally damaged, cochlear nerves had the ability to characterize frequency. 3) The signals from the implanted material were very simple compared to those from normal cochlea, however these patients could understand speech well, perhaps due to aid from the central nervous system.

Adult↗
PubMed1991

[A case of postinfectious polyradiculoneuropathy initially manifested as sudden and severe bilateral hearing loss].

A 48-year-old man noted epi-gastralgia, right back pain and lumbago. One week later he developed sudden and severe bilateral hearing loss and progressive difficulty in walking due to generalized muscle weakness of the four extremities. In AIDP, involvement of the 8th cranial nerve is very rare. At the initial stage of the illness ABR disclosed prolonged latency of wave V, and other waves were not detected at all. Thereafter the ABR findings improved gradually with concomitant improvement of the clinical signs and symptoms, and waves I and III became identifiable together with a shortening of the latency of wave I. These ABR findings suggest that the main lesion in this patient involves the peripheral part of the cochlear nerve. Antibody titers for HSV-I were high in CSF and serum at the initial stage, and decreased gradually in parallel with the improvement of the neurological signs and symptoms. Seven cases of AIDP or Guillain-Barré syndrome with impairment of the 8th cranial nerve have been reported in the literature. Nevertheless, the present case is of interest because of the severity of the hearing impairment and also because this is the first case for which the time courses of ABR findings and HSV-I antibody titers are available.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1992

The CNS-PNS transitional zone of the rat. Morphometric studies at cranial and spinal levels.

The transitional zone is that length of rootlet containing both central and peripheral nervous tissue. The CNS-PNS interface may be defined as the basal lamina covering the intricately interwoven layer of astrocyte processes which forms the CNS surface and which is pierced by axons passing between the CNS and PNS. Study of transitional zone development defines morphologically the growth, relative movement and interaction of central and peripheral nervous tissues as they establish their mutually exclusive territories on either side of the CNS-PNS boundary, and helps to explain the wide variations in the form of the mature transitional zone. Nerve rootlets at first consist of bundles of bare axons. These become segregated by matrices of fine Schwann cell processes peripherally and of astrocyte processes centrally. The latter may prevent Schwann cell invasion of the CNS. Astrocyte processes branch profusely and come to form the principal central nervous tissue component of the transitional zone. Developmental changes in the transitional zone vary markedly between nerves, reflecting differences in its final morphology. Widespread relative movements and migration of CNS and PNS tissues take place during development, so that the central-peripheral interface changes shape and position, commonly oscillating along the proximodistal axis of the rootlet. For example, developing cervical ventral rootlets contain a transient central tissue projection, while that of lumbar ventral rootlets and to a lesser extent that of cervical dorsal rootlets alternately increase and decrease in length. In the developing cochlear nerve, a central tissue projection is present before birth, but regresses somewhat before a marked outgrowth of central nervous tissue along the nerve takes place, which reaches into the modiolus during the first week postnatum. During development, some astrocytic tissue may even break off and migrate distally into the root, giving rise to one or more glial islands within it. During the period immediately preceding birth, Schwann cells come to be present in very large numbers in that part of the rootlet immediately distal to the CNS-PNS interface, the proximal rootlet segment. Here they form prominent sleeves or clusters of closely packed cells which intertwine with and encapsulate one another on the rootlet surface. Such Schwann cell overcrowding in the proximal rootlet segment could result in part from distal overgrowth of the rapidly expanding CNS around axon bundles, which might strip the Schwann cells distally off the bundle segments so engulfed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Histologic findings in two very small intracanalicular solitary schwannomas of the eighth nerve: II. "Onion bulbs".

An "onion bulb" is a descriptive histologic term referring to concentric layers of Schwann cell processes about a myelinated nerve fiber. Between the layers of Schwann cells are increased amounts of longitudinally oriented collagen fibers. It is thought that onion bulbs form as a result of sequential segmental demyelination and remyelination attempts. This process can become so severe that the myelinated fiber loses its myelin and ultimately degenerates; however, many fibers remain viable and thinly myelinated. The physiologic effect of "onion bulbs" is to markedly decrease conduction velocity in the fiber affected. In the auditory system, incompletely myelinated cochlear nerve fibers in the infant and in patients with multiple sclerosis show delays of the auditory evoked potential latencies and psychoacoustic retrocochlear patterns. No anatomic substrate has been identified for these auditory tests patterns in the acoustic tumor (solitary schwannoma of the eighth nerve). Two very small intracanalicular acoustic tumors were resected en bloc with the nerve of origin, serially sectioned, stained for neural tissue, and studied by light microscopy. In both tumors, histologic findings consistent with onion bulb formation were discovered about some of the myelinated nerve fibers found deeply incorporated in the tumor mass. These findings suggest that demyelination, perhaps with the formation of onion bulbs, may be a histopathologic correlate for retrocochlear dysfunction seen in acoustic tumors.

Cranial Nerve Neoplasms↗
PubMed1998

Plastic changes in glycine and GABA release and uptake in adult brain stem auditory nuclei after unilateral middle ear ossicle removal and cochlear ablation.

[i] In young adult guinea pigs, the effects of unilateral ossicle removal and unilateral cochlear ablation were determined on [14C]glycine or [14C]GABA release and uptake measured in subdivisions of the cochlear nucleus (CN), the superior olivary complex, and the auditory midbrain, after 2 or 5, 59, and 145 postlesion days. Activities were compared to those of age-matched, unlesioned controls. [ii] [14C]Glycine release declined bilaterally in the anteroventral and dorsal CN after ossicle removal and in the dorsal CN after cochlear ablation. [iii] Transient elevations of release occurred at 59 days in the ipsilateral posteroventral CN ([14C]glycine) and bilaterally in the ventral nucleus of the lateral lemniscus ([14C]GABA) after ossicle removal, and bilaterally in the medial superior olive ([14C]glycine) after cochlear ablation. [iv] In the medial nucleus of the trapezoid body, [14C]GABA release was depressed bilaterally 5 days after ossicle removal, but was elevated at 145 days contralaterally after ossicle removal and ipsilaterally after cochlear ablation. [v] In the contralateral central nucleus of the inferior colliculus, [14C]GABA release was elevated persistently after ossicle removal. After cochlear ablation, release was elevated at 5 days, near the control at 59 days, and elevated again at 145 days. [vi] After both lesions, [14C]glycine uptake was elevated bilaterally in the CN and medial superior olive. [14C]GABA uptake became depressed by 59 or 145 days bilaterally in the auditory midbrain. [vii] These changes may stem from regulation and may contribute to mechanisms that generate symptoms such as loudness recruitment and tinnitus, which often accompany hearing loss.

Age Factors↗
PubMed2006

Lithium increases bcl-2 expression in chick cochlear nucleus and protects against deafferentation-induced cell death.

Approximately 20-30% of neurons in the avian cochlear nucleus (nucleus magnocellularis) die following deafferentation (i.e. deafness produced by cochlea removal) and the remaining neurons show a decrease in soma size. Cell death is generally accepted to be a highly regulated process involving various pro-survival and pro-death molecules. One treatment that has been shown to modify the expression of these molecules is chronic administration of lithium. The present experiments examined whether lithium treatment can protect neurons from deafferentation-induced cell death. Post-hatch chicks were treated with LiCl or saline for 17 consecutive days, beginning on the day of hatching. On the 17th day, a unilateral cochlea ablation was performed. Five days following surgery, the nucleus magnocellularis neurons were counted stereologically on opposite sides of the same brains. Lithium reduced deafferentation-induced cell death by more than 50% (9.8% cell death as compared with 22.4% in saline-treated subjects). Lithium did not affect cell number on the intact side of the brain. Lithium also did not prevent the deafferentation-induced decrease in soma size, suggesting a dissociation between the mechanisms involved in the afferent control of soma size and those involved in the afferent control of cell viability. A possible mechanism for lithium's neuroprotective influence was examined in a second set of subjects. Previous studies suggest that the pro-survival molecule, bcl-2, may play a role in regulating cell death following deafferentation. Tissues from lithium- and saline-treated subjects were examined using immunocytochemistry. Chronic administration of lithium dramatically increased the expression of bcl-2 protein in nucleus magnocellularis neurons. These data suggest that lithium may impart its neuroprotective effect by altering the expression of molecules that regulate cell death.

Afferent Pathways↗
PubMed2002

TrkB levels in the cochlear nucleus after unilateral cochlear ablation: correlations with post-lesion plasticity.

Tyrosine kinase B (TrkB) levels in the adult guinea pig cochlear nucleus (CN) were determined from Western blots for up to 60 days after unilateral cochlear ablation (UCA). Compared to TrkB levels on the intact side, those on the lesioned side were elevated in the anteroventral CN (AVCN) at 7 and 60 days and in the posteroventral CN (PVCN) at 30 days. TrkB levels were depressed in the AVCN and the dorsal CN (DCN) at 30 days. Elevations in the AVCN on the lesioned side at 7 days coincided with a period of synaptogenesis. Other changes were temporally related to up- or downregulations of transmitter release and synaptic receptor activities that were evident after UCA. The findings suggest that changes in signaling through TrkB may contribute to the plasticities in the CN that were evident after UCA.

Animals↗
PubMed1980

Pathologic significance of Meniere's symptom complex. A histopathologic and electron microscopic study.

Histologic and ultrastructural findings in the temporal bones of a patient clinically diagnosed as having unilateral Meniere's disease are presented. The patient underwent two endolymphatic subarachnoid shunt operations that failed to relieve symptoms and a middle fossa vestibular nerve section that completely relieved episodic vertigo and stabilized hearing in the ear operated upon. Histopathologic examination of the temporal bones showed no endolymphatic hydrops in either ear. The maculae and cristae on the side operated upon showed severe degenerative changes attributed to vestibular neurectomy. The cochleograms of the operated and contralateral ears showed degeneration of the sensorineural structures in the basal two turns of the cochlea. No apparent cause for the fluctuant hearing loss was found in the cochlea or the cochlear nerve of the involved ear. Light and electron microscopic studies of the vestibular nerve excised at the time of vestibular neurectomy showed that most of the nerve fibers and ganglion cells were essentially normal. Collagen tissue deposition was increased in some areas of the endoneurial space. Most myelinated nerve fibers in these areas had degenerated. Although these changes may be partly due to artifacts and partly due to aging, they probably are the result of a pathologic process affecting the vestibular nerve. These findings suggest that a revised approach to the etiology, pathogenesis, and treatment of Meniere's symptom complex is indicated.

Female↗
PubMedDate not supplied

[Our experience in neuroma surgery].

Our 24-year experience with acoustic neuroma surgery is reported. Three approaches were used in 34 patients: translabyrinthine (11 cases), transtemporal (2 cases), and retrosigmoid (21 cases). Prolonged facial paralysis occurred in 27% of patients with the translabyrinthine approach and in 15% with the retrosigmoid approach. Facial nerve monitoring was used in all operations with the retrosigmoid approach. In the translabyrinthine approach, 5 patients had CSF leak, 2 required secondary surgery, and 2 developed meningitis. With the retrosigmoid approach, 5 patients had CSF leak, 2 required secondary surgery, 3 developed meningitis (1 died), and 1 patient required emergency reoperation for posterior cranial fossa hematoma. Auditory function was preserved in one patient. The advantages of the retrosigmoid approach have become apparent: good exposure, speed, and preservation of the facial and cochlear nerves.

Adolescent↗
PubMed2005

Facial nerve stimulation after cochlear implantation.

OBJECTIVES: This study was designed to compare the incidence and nature of facial nerve stimulation (FNS) in patients receiving cochlear implants (CI) manufactured by Cochlear Corporation, Advanced Bionics Corporation, and MedEl. STUDY DESIGN: Retrospective chart review at a tertiary referral center. METHODS: The charts of 600 patients who received CIs from 1993 to 2003 with at least 1 year of follow-up were reviewed for significant FNS (FNS on at least 1 channel at functional stimulation levels). Data collected included age, sex, etiology of deafness, device type, electrode, FNS onset after initial stimulation, number and location of electrode contacts causing FNS, and loudness level at which FSN occurred. Nucleus straight and perimodiolar electrodes were also compared. RESULTS: Thirty-nine of 600 (6.5%) patients had FNS on at least one channel, (MedEl 3 of 43 [7.0%], Nucleus 29 of 440 [6.6%], and Clarion 7 of 117 [6.0%]). The incidence of FNS in Nucleus perimodiolar electrodes (16 of 250 [6.4%]) was similar to straight electrodes (13 of 190 (6.8%]), as was the mean number of electrodes causing FNS per patient (11 vs. 12). However, straight electrodes caused stimulation at significantly softer perceived loudness levels than perimodiolar electrodes (P < .0001). CONCLUSIONS: In this large series of CI FNS, the overall incidence of FNS is consistent with previous reports. All devices had a similar incidence of FNS, but perimodiolar electrodes produced FNS only at significantly higher loudness levels than straight electrodes, making them preferable for patients at risk for FNS receiving Nucleus devices.

Adolescent↗
PubMedDate not supplied

Sudden deafness: histopathologic correlation in temporal bone.

The histopathological study of two cases of sudden deafness is presented. The temporal bones showed cochleosaccular abnormality. The most striking pathological changes were collapse of the organ of Corti, atrophy of the tectorial membrane, atrophy of the stria vascularis, decrease in the number of the cochlear nerves, collapse of the saccular membrane and partial absence of the sensory epithelial layer in the saccular macula. These changes are quite similar in type to those occurring in labyrinthitis of known viral etiology and to those in previously reported cases of sudden deafness which were assumed to be of viral origin. This evidence suggests that a viral infection was the most probable etiology of sudden deafness in these ears. In addition, unusual findings of endolymphatic hydrops limited to the extreme basal end of the cochlear duct were found in Case 1. A patent cochlear aqueduct and circumscribed perilymphatic labyrinthine ossification in the superior seimicircular canal were also observed. With these histopathological findings, the possibility of viral infection via the meninges as well as via the hematogenous route into the inner ear is proposed.

Cochlea↗
PubMed1993

Assessment of central, peripheral, and autonomic nervous system functions in lead workers: neuroelectrophysiological studies.

To assess the effects of lead on central, peripheral, and autonomic nervous systems, the visual-, short-latency somatosensory-, and brainstem auditory-evoked potentials (VEP, SSEP, and BAEP), event-related potential (P300), distribution of nerve conduction velocities (DCV), and electrocardiographic R-R interval variability (CVRR), together with conventional median and radial nerve conduction velocities (NCV), were measured in the lead workers. The lead workers consisted of 22 gun metal foundry workers occupationally exposed to lead, zinc, and copper. In the lead workers with blood lead concentrations below 65 micrograms/dl, the latencies of the VEP (from the retina to the visual cortex), SSEP (from the brachial plexus to the brainstem), and P300 (which reflects cognitive function) were significantly prolonged when compared with the sex- and age-matched controls. All these latencies and the BAEP latencies (from the cochlear nerve to the brainstem) were significantly correlated with the indicators of lead absorption among these workers. The CVRR (especially, a component of parasympathetic activity) was significantly depressed in the lead workers. The slower (V10) velocity of the DCV, the motor, and sensory NCVs were also significantly slowed. These findings suggest that lead affects not only peripheral nerve but also the central and autonomic nervous functions at a subclinical level; zinc may antagonize the neurotoxic effects of lead.

Adult↗