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Results for “NERVES, ACOUSTIC”

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PubMed1979

[Audiologic diagnosis of sensorineural deafness by discriminant analysis (author's transl)].

The audiometric test-battery surely is a help to the diagnosis of a lesion of the VIIIth nerve. The discriminant analysis is the most suitable statistic procedure for reduction of the test-battery and for clearer decision in cases of ambigous constellation of findings. The persons are divided into three groups: normals, patients with presumable inner-ear disturbance, and those with lesions of the acoustic nerve. By means of the classification-coefficients (a result of the discriminant analysis) in new cases a diagnosis per conclusionem can be found on-line.

Audiometry↗

PubMed2002

[Unilateral tinnitus--diagnostics and treatment].

900 patients with tinnitus were treated between January 1998 and August 2000 in ENT Rehabilitation Center in Poznan. Unilateral tinnitus was observed in more than 50% of the patients. In all the patients a history was taken paying a special attention to the loudness estimation by the patient and to the influence of the tinnitus on the everyday life. Laryngological, audiological and neurological examinations and laboratory tests were performed. In some cases endocrinological examination was performed. In the group of patients with unilateral tinnitus a special attention was paid to the possibility of ponto-cerebellar angle tumour. After audiological diagnostics CT or MRI examinations were performed. Authors emphasize, that in patients with unilateral tinnitus a proper observation is required to exclude expansive process within the acoustic nerve.

Activities of Daily Living↗

PubMed1975

Far-field acoustic response: origins in the cat.

Short-latency evoked potentials recorded from the vertex of adult cats in response to click stimulation (the far-field acoustic response) were analyzed in a series of lesion experiments to determine the origins of each component. The resultant data indicate that the primary generator of potential is the acoustic nerve; of potential 2, the cochlear nucleus; of potential 3, neurons of the superior olivary complex activated by projections crossing the midline; of potential 4, neurons of the ventral nucleus of the lateral lemniscus and preolivary region activated equally by crossed and uncrossed projections; and of potential 5, neurons of the inferior colliculus activated primarily by crossed projections.

Acoustic Stimulation↗

PubMed2006

Long-term follow-up reveals low toxicity of radiosurgery for vestibular schwannoma.

AIM: The long-term effects of radiosurgery of vestibular schwannomas were investigated in a group of consecutively treated patients. METHODS AND MATERIALS: Between 1995 and 2001, 26 patients (median age: 67, range: 30-82) with a vestibular schwannoma were treated by Linac-based stereotactic radiosurgery (SRS). The median follow-up was 49 months (16-85 months). Only progressive tumours were treated. The median size of tumours was 18 mm (range 9-30 mm). Before SRS, 11 patients had a useful hearing (Gardner-Robertson classes 1 and 2). Single doses of 10-14 Gy were prescribed at the 80% isodose at the tumour margin. The follow-up consisted of regular imaging with MRI the first 3-6 months after the intervention, followed by additional yearly MRIs, a hearing test and a neurological examination. RESULT: The 5-year-probability of tumour control (defined as stabilization or decrease in size) was 95%. Five-year-probability of preservation of hearing and facial nerve function was 96% and 100%, respectively. Hearing was preserved in 10 out of 11 patients who had a normal or useful hearing at the time of treatment. Mild and transient trigeminal toxicity occurred in 2 (8%) patients. It appeared to be significantly correlated to the dose used (p=0.044). However, only a tendency to significance could be demonstrated in the relationship between the two factors when using the Cox analysis (hazard ratio=1.7; 95% CI: 0.7-3.9; p=0.23). CONCLUSIONS: With the doses used, our study demonstrates that SRS provides an equivalent tumour control rate when compared to surgery, as well as on a long-term basis, an excellent preservation of the facial and the acoustic nerves. Although no permanent trigeminal toxicity was observed, our data confirm that doses below 14 Gy can avoid transient dysesthesias.

Adult↗

PubMed1993

Modeling axon membranes for functional electrical stimulation.

Four models are discussed which can be used to predict the behavior of warm-blooded axons, when excited by electric fields. Up to now, most results were obtained with the Frankenhaeuser-Huxley model, but nearly all of them are wrong in time scale and the cathodic block phenomenon was not observable because the temperature dependence of the gating mechanism has been neglected. However, in the corrected form this model reacts with similar excitability as the two other myelinated nerve models which consider that the potassium current is negligible in mammalian axon membranes. Strength-duration relations for cathodic and anodic excitations, as well as for cathodic blockade, are presented. Paradoxically, the "warm" squid model of Hodgkin and Huxley is the only one which reflects phenomena known from stimulations of the (myelinated) acoustic nerve by cochlear implants.

Animals↗

PubMed1995

Solitary primary lymphoma of the cerebellopontine angle: case report.

A 27-year-old woman had a solitary primary B-cell lymphoma that involved the right cerebellopontine angle. The tumor invaded the ipsilateral acoustic nerve and produced profound sensory neural hearing loss. Surgical resection was promptly followed by radiotherapy and a concluding brief chemotherapy treatment. The patient survived 34 months after the initial onset of the disease or 22 months after the combined treatments. Only six lymphomas affecting the cerebellopontine angle, three primary and three secondary, have been recorded. The combination of surgical treatment and radiotherapy appeared to offer encouraging results for primary lymphomas. The differential diagnosis of lymphoma of the cerebellopontine angle includes common acoustic neurilemoma, meningioma, epidermoid tumor, and other rare neoplasms involving this region that required pathological verification to distinguish them.

Adult↗

PubMed1995

The internal auditory canal revisited. The high-definition approach.

The internal auditory canal (IAC) is a bony canal that contains nerves and vessels and is lined by meninges. Pathologic processes may arise from each of these structures. Congenital, developmental, and acquired pathologic conditions may involve the bone of the canal and lead to excessive narrowing or expansion. Lesions formed within the canal include hemangiomas, vascular malformations, and inflammatory and neoplastic processes arising from the facial and acoustic nerves and meninges. Finally, other rare lesions, such as choristomas and metastases, may occur within the IAC, which are not related to its normal content. High-definition computed tomography, MR imaging, and MR angiography allow diagnoses of IAC or cerebellopontine-angle cistern lesions, some of which could not be identified by older techniques.

Ear, Inner↗

PubMed2003

Radiation-induced schwannomas of the nervous system. Report of five cases and review of the literature.

Radiation therapy has important delayed effects on the central nervous system. Prominent among these effects is radiation necrosis of nervous tissue, but an oncogenic effect is also recognized. Both benign and malignant intracranial tumors can develop in irradiated fields, particularly in children. Most of these tumors are sarcomas, meningiomas or gliomas and only occasionally schwannomas. We report 5 cases of postirradiation acoustic nerve schwannoma observed in our Department.

Adult↗

PubMed2004

Lesions of the cerebellopontine angle and internal auditory canal: diagnosis and differential diagnosis.

Schwannoma of the eighth cranial nerve (acoustic neuroma) is, by far, the most common cerebellopontine angle lesion. There is, however, a wide variety of differential diagnostic possibilities that must be considered when viewing images of patients with sensorineural hearing loss (SNHL), vertigo, and dizziness. This communication is intended to provide the reader with an approach to this problem. Detailed anatomy of the region is also included in this communication.

Cerebellopontine Angle↗

PubMed1979

Auditory brainstem evoked responses in brainstem compression due to posterior fossa tumors.

Five patients with unilateral posterior fossa tumors were investigated with Auditory Brainstem Evoked Responses (B.E.R.). The B.E.R., recorded from the ear ipsilateral to the tumor, were consistent with a lesion of the acoustic nerve or the cochlear nuclei in all patients. The contralaterally evoked responses in four patients with large tumors and radiological signs of brainstem compression showed normal latencies and amplitudes of the first three waves, while waves IV and V were definitely abnormal with respect to amplitudes and latencies. (The 4th patient had a normal wave IV and a delayed, small wave V). In one patient with a relatively small acoustic neurinoma the contralateral B.E.R. were normal. It is concluded that the upper pontine and lower midbrain level, presumed sites of generation of wave IV and V of the B.E.R., are more susceptible to brainstem compression due to unilateral posterior fossa tumors, than the lower parts of the brainstem.

Adult↗

PubMed2000

[Histopathological studies of intratemporal growth behavior of middle ear carcinoma].

BACKGROUND: Otological hemorrhage otorrhea, and pain are amongst the first clinical signs of the middle ear carcinoma, which is usually diagnosed in advanced stages. Sudden deafness, facial nerve paralysis, and other symptoms of inner ear damage may be observed in the final stage. However, middle ear carcinoma is diagnosed extremely seldom in its early stages. The clinical management of this pathology is based on the knowledge of the tumor's pathways and its anatomic behavior. METHODS: Our study investigated 20 cases of middle ear carcinomas from the Wittmaack temporal bone bank (14 squamous cell carcinomas, 5 adenocarcinomas, and 1 adenoidcystic carcinoma) to analyze the behavior of the tumor growth and its influence on clinical symptoms. The aim was to determine criteria for early clinical diagnosis. RESULTS: The tumor arises in different regions of the temporal bone, and varying symptoms will subsequently reflect its pathway. When the tumor is confined to the middle ear area, its main location is the hypotympanum from which tumor spreads into the eustachian tube and, via infiltration of the adjacent bone structures (anterior wall of the middle ear), into the tensor tympani muscle and the sympathetic plexus of the internal carotid artery. Destruction of the ossicles was observed in the mid-tympanic cavity, and often only a thin layer of fibrous tissue from the Fallopian canal separated the tumor from the facial nerve (this nerve was rarely affected directly). The medial wall (labyrinthine wall) of the tympanic cavity remained intact in the majority of examined cases. The tympanic sinus, the round window niche, and the oval window niche did not show tumor infiltration. In the epitympanum, the tumor grew and infiltrated the adjacent mastoid. Larger tumors affected the internal auditory canal and infiltrated the acoustic nerve and the labyrinth. CONCLUSION: Improving the poor prognosis of middle ear carcinoma requires early diagnosis based on axial computed tomography (CT). Important factors in patient selection include age (50-70 years), sex (mostly women), and especially clinical symptoms (otorrhea, pain, hearing loss).

Adenocarcinoma↗

PubMed2005

[Exposing the rabbit cerebellopontine angle through post-sigmoid sinus approach and recording the direct compound action potential of the auditory nerve].

OBJECTIVE: To study the way of exposing the rabbit cerebellopontine angle through post-sigmoid sinus approach and recording the direct compound action potential of the auditory nerve, and to investigate the stability of DCAP N1 wave latency. METHOD: Fifteen New Zealand rabbits which had normal Preyer's auricle reflex were selected. Each one was studied in the left ear. After anaesthetized,the cerebellopontine angle of rabbits were exposed through post-sigmoid sinus approach under aseptic status,then the needle-shaped pole were inserted into the facial-acoustic nerve complex. The DCAP was recorded at the immediateness, 2 h and 5 h after the insertino sequentially. At last, DCAP N1 wave latencies of 15 rabbits were statisticed and analyzed using paired-samples t-test. RESULT: To the 15 sides, the distinct curves with well differentiated waves were induced in the all three times. No significant difference in any N1 wave latency had been found among the 3 times. CONCLUSION: The rabbit cerebellopontine angle could be exposed and the direct compound action potential of the auditory nerve could be recorded successfully by the way studied in this experiment. In normal state, the individual value of DCAP N1 wave latency is stable. During the process of surgery in which the cerebellopontine angle has been exposed, the DCAP N1 wave latency is a practical index for monitoring of hearing impairment.

Action Potentials↗

PubMed1975

[The influence on sound damages by an extract of ginkgo biloba (author's transl)].

A fraction of Ginkgo biloba, used in experiments with animals ensured significantly the diminution of sound damages caused by white noise or by a pure tone of 4.5 kHz. Higher amplitudes of the acoustic nerve potentials show the protective effect of this fraction of Ginkgo biloba at acute sound damages. It is moreover possible to hold physiologically the adaptation of excitation of the hair cells of the organ of Corti by the fraction of Ginkgo biloba before and after sound damage caused by white noise or during a pure tone of 4.5 kHz. The influence of the fraction of Ginkgo biloba can be seen by a significantly slower recovery of the noise damaged evoked potentials of the acoustic cortex. An efferent protective influence on the neurons of the acoustic cortex is discussed. The fraction of Ginkgo biloba in this form of solution has not been tested for clinical use but it seems to be rich in meaning.

Animals↗

PubMedDate not supplied

[A model for the study of the ototoxic effects of drugs in an experiment].

The authors compared sensitivity of the acoustic analyzer elements to ototoxic drugs in cat experiments. The model proposed assesses primary responses of the brain cortical acoustic zone (BCAZ) to sound stimulation. The drugs effect on the analyzer's periphery was determined from changes in bioelectric responses of the cochlea to sound stimulation (microphone potential, potential of the acoustic nerve action). The arguments are presented for feasibility of using primary BCAZ responses evoked by electric stimulation of thalamocortical radiation fibers coming from the medial geniculate body for examination of the drug effects on the analyzer's cortex. Parallel registration of the above bioelectrical reactions in the same animal for a long time makes it possible to compare sensitivity of different elements of the acoustic analyzer to ototoxic medication.

Acoustic Stimulation↗

PubMed1988

Uni-lateral hearing-loss with acoustic neuroma patients: electrocochleographic findings.

38 patients with proven acoustic neuroma were examined. Intratympanic electrocochleography was performed with alternating clicks of 90 dB (nHL) intensity and a stimulus rate of 20 per second; 500 sweeps were averaged. Widening of the Cochlear Action Potential (CAP)-complex by a mean of 1.6 ms was the most striking finding. Summating potentials (ratio of SP-amplitude to CAP-amplitude) were enlarged to 0.6, compared to 0.2 in healthy persons and 0.8 in patients suffering from Meniere's disease. The most noticeable result was the loss of amplitude using very short interstimulus intervals. With a stimulus-rate of 97 per second amplitudes of acoustic neuroma patients were reduced by 49.9%. Acoustic neuroma patients show pathological inner ear potentials. Some of the changes such as increased SP are found in patients with Meniere's disease, supposingly caused by endolymphatic hydrops. For tumours of the acoustic nerve the hydrops theory does not seem likely; the loss of amplitude due to adaptation within the first neuron seems to point to mechanical reasons due to the pressure of the tumour itself.

Audiometry, Evoked Response↗

PubMed1990

[Vestibular efferent neurons of the guinea pig forming projections into the saccule].

The distribution of vestibular efferent neurons projecting to the saccule and efferent neurons transmitting axons to the acoustic nerve (cochlear efferent neurons) has been studied in guinea pig by comparison using the method of retrograde axonal transport of horseradish peroxidase. The saccular efferent neurons are revealed bilaterally in the subendymal granular fundus of the fourth ventricle of the brain and more laterally of the facial nerve genu, ipsilaterally in the small-celled reticular nucleus as well as in nuclei of the supraolivary complex: nucleus of lateral oliva and lateral nucleus of the trapezoid body. The cochlear efferent neurons are localized ipsilaterally in the reticular caudal nucleus of the bridge in the anteroventral cochlear nucleus and in nuclei of lateral and medial olivae. In the medial nucleus of the trapezoid body such neurons are found contralaterally. Thus, the regions of the vestibular saccular efferent neurons are partially overlapped with such of the cochlear efferent units. Possible participation of the vestibular efferent neurons of the saccule in the mechanism of the acoustic perception is discussed.

Animals↗

PubMed1989

[Acoustic oto-emissions: the ear emits sounds].

Otoacoustic emissions are sounds emitted by the inner ear. Their genesis requires the outer hair cells of the organ of Corti to be intact. Analysis of these sounds provides a fine evaluation of cochlear function. Evoked otoacoustic emissions (in response to a sound) are constant in subjects with normal hearing, whereas they always have pathological characteristics in patients with endocochlear conduction or perceptive deafness. When the acoustic nerve or the central nervous system are affected, otoacoustic emissions are normal for as long as the pathological process has no repercussions on the inner ear. This new functional exploratory method is of particular interest, being simple, non-invasive, rapid and objective. One of its main uses in adults is early detection of a lesion of the organ of Corti by e.g. ototoxic drugs or acoustic trauma. In children, it might become a test for objective detection of deafness, being easier to perform than evoked potentials of the brain stem.

Acoustic Stimulation↗

PubMed1976

[Cogan's syndrome with angitis of cranial nerves, aortitis, endocarditis, and glomerulonephritis (author's transl)].

A 34-year-old woman died of left-heart failure due to combinated aortic-valve disease three years after manifestation of Cogan's syndrome characterized by sudden inner-ear deafness, loss of equilibrium, interstitial keratitis, and progressive loss of vision during pregnancy. At necropsy there was evidence of recurrent endocarditis of the aortic valves with stenosis and regurgitation, severe angitis of the thoracic aorta with marked secondary sclerosing changes as the cause of the heart failure. Angitis within the optical fasciculus and stato-acoustic nerve was the cause of the vestibular and optical defects. Primary changes in the visual and auditory cortices, the retina and inner ear were excluded as causes. There was also acute membrano-proliferative glomerulonephritis, which may have been coincidental.

Acute Disease↗