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At least 55 records · Page 3Linked to original sources
PubMed1980

Glioma of the acoustic nerve.

We report a case of astrocytoma of the acoustic nerve. Most gliomas arise from the brainstem, and seldom originate in the acoustic or other "true" cranial and spinal nerves. Clinical features of this rare acoustic tumor differ from those of brainstem gliomas, but are indistinguishable from typical acoustic neurilemoma. We discuss the diagnosis and histogenesis of glioma arising in the eighth cranial nerve. Demonstration of glial fibrillary acid protein, an antigen specific for astrocytes, is a new method of verifying the diagnosis. Review of the literature indicates that a few cases of epithelial-like tumors of peripheral nerves may have been of neuroepithelial origin. The evidence, however, generally is not sufficient to exclude the possibility of metastatic neoplasms or other tumors such as malignant schwannoma and melanoma. Most of these putative gliomas contained gland-like tissue, and did not have the morphologic appearance of astrocytoma, as in approximately five reported examples, and in our case.

Adult↗
PubMed2003

Lipochoristomas (lipomatous tumors) of the acoustic nerve.

CONTEXT: Lipochoristomas (lipomatous choristomas) are rare tumors of the acoustic nerve (cranial nerve VIII/vestibulocochlear nerve) within the internal acoustic canal and sometimes the cerebellopontine angle, and are histogenetically believed to be congenital malformations. Their clinically indolent behavior has recently prompted a more conservative management protocol in a quest for maximal nerve/hearing preservation. This approach contrasts sharply with that for the common internal acoustic canal/cerebellopontine angle tumors, the neuroepithelial neoplasms (acoustic schwannomas and meningiomas), which behave more aggressively and have more prominent clinical manifestations. Owing to their rarity, the clinicopathologic features of cranial nerve VIII lipochoristomas have been obtained mainly through case reports. OBJECTIVE: We present the clinicopathologic features of 11 cases of lipochoristomas of cranial nerve VIII. DESIGN: The 11 cases were documented between 1992 and 2003. We performed complete clinical reviews with histologic, histochemical, and immunohistochemical analyses of formalin-fixed, paraffin-embedded tumor samples. RESULTS: The patients were 8 men and 3 women with hearing loss of the right ear (5 patients) or the left ear (6 patients). No patient had bilateral tumors. All lipochoristomas histologically possessed mature adipose tissue admixed with varied amounts of mature fibrous tissue, tortuous thick-walled vessels, smooth muscle bundles, and skeletal muscle fibers, the latter verified with immunohistochemistry. CONCLUSIONS: The histomorphologic and immunophenotypic evidence showed that these tumors are better characterized as choristomas than as simple "lipomas," as they have been labeled in the past. Their overall nonaggressive clinical nature in addition to the characteristic radiologic and histomorphologic findings are important clinicopathologic features for the pathologist to recognize and differentiate, especially during frozen section evaluations, in order to direct the neurosurgeon to a more appropriate conservative therapeutic intervention.

Adult↗
PubMed1980

The location by early auditory evoked potentials (EAEP) of acoustic nerve and brainstem demyelination in multiple sclerosis (MS).

Tone pips of suprathreshold intensities elicit an acoustic nerve response (I) and six low amplitude brainstem potentials (II-VII) during the initial 10 ms. Seven waves were studied in 40 control subjects and 5 waves (I-V) in 47 patients with MS. The results suggest involvement of the auditory pathway of 24 of 27 patients in the clinically "definite", of 5 of 9 cases in the "probable" and in none of 5 patients in the "possible" MS groups. EAEPs were normal in 6 cases with a spinal form with one exception where changes of potential were indicative of a midbrain lesion. Dysfunction within the acoustic pathway was observed at the level of the acoustic nerve and in the medulla oblongata, pons and midbrain. The significance of the bilateral EAEP abnormalities found in some patients at different levels is discussed with regard to a polytopic location of the underlying lesion.

Adult↗
PubMed1986

A study of the application of the Hodgkin-Huxley and the Frankenhaeuser-Huxley model for electrostimulation of the acoustic nerve.

By means of electrostimulation of the acoustic nerve profoundly deaf patients can, in the best cases, reach almost complete speech understanding without lip reading. In this paper the information content of the signals supplied to patients is examined by a study of action potential generation by means of the Hodgkin-Huxley and the Frankenhaeuser-Huxley equations solved by means of a digitally controlled analogue computer. The response to sinusoidal signals and to signals with the wave shape of certain vowels is investigated and compared with results from animal experiments and observation on patients.

Action Potentials↗
PubMed1994

Stereotactic radiosurgery for acoustic nerve tumors in patients with useful preoperative hearing: results at 2-year follow-up examination.

Twenty patients with acoustic nerve tumors (mean diameter < or = 30 mm) and useful preoperative hearing were examined 2 years after stereotactic radiosurgery to determine the effectiveness of the surgery in the control of tumor growth and the preservation of cranial nerve function. Results showed tumor volume stabilization (12 cases) or reduction (seven cases) was achieved in a total of 19 patients (95%). Useful hearing (defined as Gardner and Robertson Class I or II) preservation was obtained in 100% of cases immediately postoperatively, 50% at 6 months, and 45% at both 1 and 2 years. Two years after stereotactic radiosurgery, facial nerve function was preserved in 90% of patients and 75% continued to have normal trigeminal nerve function. All patients returned to and maintained their preoperative functional status within 3 to 5 days after radiosurgery. These findings indicate that stereotactic radiosurgery with multiple isocenters and narrow radiation beams is a safe and effective management strategy for progressive acoustic nerve tumors. Auditory, facial, and trigeminal nerve function can be preserved in most patients. Prevention of further growth and preservation of cranial nerve function appear to be satisfactory goals in the current management of patients with acoustic neuromas.

Adult↗
PubMed1995

Acoustic nerve in peripheral neuropathy: a BAEP study. Brainstem Auditory Evoked Potentials.

We performed BAEP study to evaluate acoustic nerve involvement in 102 patients affected by peripheral neuropathies of different etiology, predominantly hereditary and inflammatory acquired neuropathies. Prolonged latency of early waves, indicative of slowing in VIII nerve conduction, was found in a high percentage of cases. Abnormalities were far more frequent (44% vs 14%) and severe in patients with demyelinating rather than axonal neuropathy. Among demyelinating neuropathy, the most severe latency delay was found in Hereditary Motor and Sensory Neuropathy type III. The pattern of acoustic nerve involvement differed slightly between Hereditary Motor and Sensory Neuropathy type I and acquired inflammatory demyelinating polyradiculoneuropathy, perhaps reflecting different pathogenetic mechanisms and different sites of VIII nerve demyelination.

Adolescent↗
PubMed1975

Compound action potential and single acoustic nerve fibres activity generation: an equivalent neuron approach.

The peripheral acoustic system can be easily subdivided into three distinct subsystems: a mechanical one (middle ear and basilar membrane), the set of mechanical-to-neural transducers (the inner and outer hair cells) and the neural part. The functional behaviour of the external and middle ear is well known, but the processes concerned with the transduction of mechanical motion into neural activity are still under investigation. Actually the mechanism of transmission of information concerning acoustic stimuli to the central nervous pathways is not clearly known. On the basis of physiological knowledge, a mathematical model reproducing the pattern of activity of the acoustic nerve, in response to the most typical acoustic stimuli, is proposed. This has been simulated on a digital computer.

Action Potentials↗
PubMed1988

Synaptic endfeet in the 'acoustic nerve nucleus' of the rat. An electron microscopic study.

The medial portion of the cochlear nerve of the rat contains astrocytes, oligodendrocytes and neurons. These neurons form what has been called the 'acoustic nerve nucleus'. This nucleus has been studied here at the electron microscopic level. Its neurons are large and round, showing an eccentric nucleus, fibrillary bodies and rough endoplasmic reticulum which is not arranged in stacks. The somata and dendrites receive synaptic endfeet which can be classified into three groups according to vesicle size and shape. In general, the ultrastructural characteristics of these cells are similar to those of bushy cells as reported by other authors. The 'acoustic nerve nucleus' can be considered to be the most peripheral part of the anterior ventral cochlear nucleus.

Animals↗
PubMed1991

[Experience with electrostimulation of the acoustic nerve before cochlea implantation].

The electrical stimulation of the acoustic nerve plays an essential role in the selection of patients for cochlea implantation. The performance of a deaf ear under the conditions of electrical stimulation can be assessed by means of the pre-operative promontory test using a transtympanic needle electrode. Five components of this test were applied to 48 patients: the determination of perception threshold and upper comfortable level for pulse and burst stimulation, the pitch test, the temporal difference test and the gap detection test. The mean values emerging from these examinations may be useful as guidelines for the interpretation of individual results. A cross correlational analysis of the data was performed in order to eventually discover redundancies among the different test components. Indeed, the threshold values for pulses of a given duration are highly correlated to those for bursts of the corresponding frequency. One of these tests may therefore be eliminated for routine test purposes. Similarly, the assessment of time resolution capabilities with the temporal difference limen test yields results which show a strong correlation with those of the gap detection test.

Auditory Threshold↗
PubMedDate not supplied

Epithelioid Schwannoma of the acoustic nerve.

A 25-year-old woman presented with left progressive deafness due to an intracranial tumor of the cerebello-pontine angle. Biopsy and subsequent total surgical excision indicated origin from the acoustic nerve. Histologically, the tumor showed typical feature of Schwannoma associated with a population of epithelioid cells. Three years after surgery no local invasion, no relapse, and no metastasis were noted. Immunohistochemistry showed a strong positivity for S100 protein in the cytoplasm of Schwannian and epithelioid tumoral cell components. This positivity in the epithelioid cells correspond to a well differentiated cell population derived from a Schwann cell precursor explaining the benign course of the tumor. In the absence of similar cases of epithelioid Schwannoma of the acoustic nerve in literature, we will discuss the differential diagnosis, potential evolutivity, and origin of the epithelioid cells.

Adult↗
PubMed1988

Acoustic nerve conduction abnormalities in Guillain-Barré syndrome.

We recorded brainstem auditory evoked potentials (BAEPs) in two patients with Guillain-Barré syndrome (GBS). One patient was acutely deaf with total absence of BAEP waveforms indicative of acoustic nerve conduction block. Hearing improved during early convalescence, and there were prolonged wave I latencies. Normal BAEPs were recorded on recovery. A second patient had bilaterally prolonged wave I latencies. These BAEP findings suggest that acoustic nerve conduction abnormalities from demyelination may occur in GBS.

Adult↗
PubMed1976

The structural maturation of the stato-acoustic nerve in the cat.

The maturation of the stato-acoustic nerve in the cat was studied by light and electron microscopy from the fetal stage to the adult. Measurement of the outer diameter of the fibers and the study of the myelination process revealed that myelination begins earlier for the vestibular nerve than for the cochlear nerve: by the fifty-third day of gestation 64% of the vestibular fibres have already passed the promyelin stage whereas for the cochlear nerve this promyelin stage begins for the majority of fibers on the fifty-seventh gestation day. Afterward, maturation proceeds more rapidly for the cochlear nerve. In the case of both nerves, maturation is still incomplete at two months of age. Concerning the relationship between the thickness of the myelin sheath and the axoplasmic diameter, there is already a good correlation by the fifty-seventh day of gestation in the vestibular nerve, whereas it appears several days after birth in the cochlear nerve.

Age Factors↗
PubMed1962

Second order neurons in the acoustic nerve.

In silver-stained preparations of the rat auditory system large neurons were distributed over the whole length of the acoustic nerve. These neurons received many synaptic endings which arose from collaterals of the acoustic fibers. The axons of the neurons ascended toward the cochlear nuclei. Similar neurons were found in the mouse, but not in the bat or cat.

Animals↗