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At least 289 records · Page 16Linked to original sources
PubMed1992

Latency enhancement of the cochlear nerve compound action potential (CAP).

Forward maskers within two frequency-intensity domains are capable of decreasing (enhancing) CAP latency: one region flanks the low frequency tail, the other flanks the tip/high frequency slope regions of the latency tuning curve (TC). By contrast, amplitude enhancement typically does not flank the high frequency slope region.

Acoustic Stimulation↗
PubMed1999

[Microsurgical anatomy of a large size tumor of vestibulo-cochlear nerve].

The microsurgical anatomy peculiarities of a large size tumor of n. vestibulocochlearis (NVC) were studied, basing on intraoperative (in 380 patients) and sectional (30) observations data. The distinguishing of three main anatomic-topographical variants of a large size NVC tumor growth has great significance for elaboration of the microsurgical tumoral excision method.

Cochlear Nerve↗
PubMed1999

Acoustic neuroma: outcome of surgical resection and study on the anatomy of facial and cochlear nerves.

The treatment of acoustic neuroma (vestibular schwannoma) has evolved greatly. In this report, we studied the history of acoustic tumour surgery, and documented the value of technical advances in benefiting patients. We also present our outcome of surgery for this benign tumour in support of its use as the treatment of choice. In 611 patients undergoing initial surgery at Johns Hopkins from 1973-1994, complete resection was obtained in all but one case (intentional), and permanent morbidity and mortality rate was 0.3%. Including temporary morbidity, the rate was 3.8%. Tumour recurrence was seen in only 0.8% of cases. The facial nerve was preserved in 97.6% and function at one-year was House-Brackmann grade 1 or 2 in 89.7%. Lastly, we present results of an anatomical study localizing the nerves and vessels, and the frequency of involvement by tumour, associated with acoustic neuromas in 1006 surgical cases. We continue to offer surgery as the best treatment option for the majority of our patients, and prefer the suboccipital route because of its unrestricted access to all posterior fossa structures, and ability to preserve hearing.

Adolescent↗
PubMed1982

The effects of intracochlear cyanide and tetrodotoxin on the properties of single cochlear nerve fibres in the cat.

1. Tuning properties and spontaneous discharge rate of single cochlear fibres in the anaesthetized cat were determined under conditions where millimolar concentrations of KCN were instilled into the scala tympani. 2. Short-term effects on the tuning properties were obtained, in which the threshold of the low threshold sharply tuned tip segment of the frequency-threshold ('tuning') curve (f.t.c.) was elevated by up to 40 db, without changes in the threshold of the low frequency 'tail' segment of the f.t.c., or necessarily changes in the spontaneous and maximally evoked activity. These changes were accompanied by a shift of the characteristic frequency tip segment towards lower frequencies. All these effects could be reversed. 3. The long-term effects of repeated KCN instillations produced irreversible changes similar to the short-term effects. 4. These changes correlated well with depression of the amplitude of the gross cochlear action potential but not with the cochlear microphonic potential, both recorded at the round window. 5. Instillations of tetrodotoxin (TTX) rapidly reduced and blocked the cochlear fibre discharges without effects on their tuning, in contrast to the effects of KCN.

Action Potentials↗
PubMedDate not supplied

Some unresolved problems concerning the cochlear nerve.

Three types of afferent fibers innervate the hair cells of the organ of Corti: 1) specific radial fibers which establish contacts with a very few neighboring internal hair cells; 2) spiral fibers, each one of which establishes contact with a number of external hair cells distributed throughout long segments of the cochlea; and 3) unspecific radial fibers which are collaterals arising radially at irregular intervals from fibers of the ganglionic spiral bundles and which establish contact with internal hair cells. The existence of spiral ganglionic bundles of fibers oriented apicalward has long been described, and the fact that a number of ganglionic spiral fibers give off radial collaterals to innervate internal hair cells was illustrated by Cajal and by Lorente de Nó. However, those structural details are not mentioned in the modern literature. In the ventral nucleus there are neurons with efferent axons which join the trapezoid body and cells with short axons ramified within the ventral nucleus itself. Two types of cells with efferent axons are illustrated and described, the spherical or bushy cell and the basket cell; and it is shown that branches of division of the two types of efferent axons form association tracts which end in the tuberculum acusticum. Also, the fact is illustrated that fibers having their cells of origin in that tuberculum form association paths which end in the ventral nucleus by means of extensive ramifications which form numerous synaptic endings. The dendritic and fibrillar plexuses in the ventral nucleus are described, an analysis is made of the relationships between the two plexuses and of the synaptic junctions that mediate transmission of nerve impulses. The synaptic junctions belong to a considerable number of types and in all illustrations the important fact repeatedly appears that one and the same fiber may form synaptic endings of widely different sizes and shapes located either on the same neuron or, more frequently, on different neurons. The intimate structure of each type of synaptic ending cannot be revealed by light microscopy, but only light microscopy can reveal to which kind of fiber the synaptic endings do belong. The presentation is concluded with a brief and preliminary discussion of physiological corollaries of certain general features of the anatomy of the acoustic system.

Animals↗
PubMed1988

Effect of spider venom on cochlear nerve activity consistent with glutamatergic transmission at hair cell-afferent dendrite synapse.

Venom from the spider Argiope trifasciata, a highly specific blocker of the ionic channels associated with invertebrate glutamatergic receptors, was perfused through scala tympani of the basal turn of the pig cochlea. Its effect on spontaneous and driven activity of single afferent neurons was studied. 0.1 U/ml spider venom altered the maximum driven activity without an effect on spontaneous activity. 1 U/ml spider venom suppressed both spontaneous and driven activity. These findings are consistent with the hypothesis that L-glutamate is the neurotransmitter of the synapse between inner hair cells and primary auditory afferent neurons. The results also suggest that the differences in spontaneous activity between neurons may originate in variations in neurotransmitter release.

Animals↗