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Results for “VESTIBULAR NERVE”

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At least 19 recordsLinked to original sources
PubMed1987

Morphometry and ultrastructure of the squirrel monkey (Saimiri sciureus) vestibular nerve.

Vestibular nerves of squirrel monkeys (Saimiri sciureus) embedded in plastics and epoxies were examined with light microscopy (LM) and transmission electron microscopy (TEM), and computerized measures were obtained and analyzed statistically. An average of 12,412 perikarya and 12,005 myelinated nerve fibers was obtained. Approximately 0.7% of the perikarya appeared unmyelinated under LM. About 500 unmyelinated fibers were counted. The cross-sectional area of 1,864 perikarya was 200-650 micron 2. The cross-sectional area of 1,346 nerve fibers was 3-11 micron 2 for the axoplasm and 11-12 micron 2 for the myelin sheath of the same fiber. Myelin thickness was directly proportional to the axoplasm cross-sectional area of the nerve fibers. The cross-sectional area of central axons and peripheral dendrites differed significantly (p less than 0.001). The initial segments of peripheral dendrites were usually smaller, but longer than the initial segments of the central axons. Both initial segments increased in diameter after the first node of Ranvier. Schmidt-Lantermann incisures were more abundant in thick and heavily myelinated fibers than in thin and lightly myelinated fibers. Larger perikarya usually had larger fibers and vice versa, within the first 100-200 micron from the first node of Ranvier. No major ultrastructural differences were found between myelinated and unmyelinated perikarya, except at the hillock region. The Nissl substance was preferentially located in the peripheral cytoplasm.

Animals↗
PubMed1994

Neural conduction velocity of the human auditory nerve: bipolar recordings from the exposed intracranial portion of the eighth nerve during vestibular nerve section.

We measured the conduction velocity of the intracranial portion of the auditory nerve in 3 patients undergoing vestibular nerve section to treat Ménière's disease. The conduction velocity varied from patient to patient, with an average value of 15.1 m/sec. The latency of peak III of the brain-stem auditory evoked potentials (BAEPs) increased by an average of 0.5 msec as a result of exposure of the eighth nerve, and if that increase is assumed to affect the entire length of the auditory nerve (2.6 cm) evenly, then the corrected estimate of conduction velocity would be 22.0 m/sec. Estimates of conduction velocity based on the interpeak latencies of peaks I and II of the BAEP, assuming that peak II is generated by the mid-portion of the intracranial segment of the auditory nerve, yielded similar values of conduction velocities (about 20 m/sec).

Electroencephalography↗
PubMed1994

Click-evoked responses from the exposed intracranial portion of the eighth nerve during vestibular nerve section: bipolar and monopolar recordings.

We compare the click-evoked compound action potentials from the exposed intracranial portion of the eighth nerve using bipolar and monopolar recording electrodes in patients undergoing vestibular nerve section. It is assumed that a bipolar recording electrode will only record propagated neural activity in the auditory nerve, whereas a monopolar recording electrode may in addition record electrical activity that is conducted passively to the recording site. The results of the present study confirm that the earliest detectable propagated neural activity in the intracranial portion of the auditory nerve occurs with a latency that is close to that of peak II of the brain-stem auditory evoked potentials, and the results also confirm that the late components in the click-evoked compound action potentials that have been demonstrated previously using the monopolar recording technique represent propagated neural activity in the auditory nerve. The results also indicate that the responses that are recorded by a bipolar recording electrode, when the small tips of which are placed on the eighth nerve when it is relatively dry, represent only small populations of nerve fibers. Even when an attempt is made to align the two tips of a bipolar electrode with the course of the auditory nerve, this type of electrode may record from different populations of nerve fibers.

Acoustic Stimulation↗
PubMedDate not supplied

Responses of hypothalamic neurons to stimulation of the vestibular nerve and lateral vestibular nucleus in the rabbit.

Acute experiments were performed on rabbits to study the responses of neurons in the anterior, ventromedial, and posterior nuclei of the hypothalamus to single, paired, and rhythmic stimulation of the vestibular nerve and lateral vestibular nucleus of Deiters. The data obtained showed that neurons of the posterior nucleus of the hypothalamus were the most sensitive. Three types of response were seen from hypothalamic neurons, with short, long, and intermediate latent periods. This provides evidence that ascending afferent spike activity from the lateral vestibular nucleus of Deiters to the hypothalamus is mediated by mono-, oligo-, and polysynaptic pathways.

Animals↗
PubMed1995

Release of glutamate from the vestibular nerve in the medial vestibular nucleus as a neurotransmitter: in vivo microdialysis study.

Histochemical and electrophysiological studies suggest that glutamate is the primary afferent neurotransmitter from the vestibular nerve to vestibular nucleus. To further examine this possibility, a microdialysis study using alpha-chloralose-anesthetised cats was performed to elucidate whether glutamate is released from the vestibular nerve terminal in the medial vestibular nucleus (MVN). A microdialysis probe (CMA/10.2 mm) was inserted into the MVN and perfused with Ringer solution at 2 microliters/min. Samples were collected at 10-min intervals. Endogeneous glutamate was measured using the HPLC-ECD method. When electrical repetitive stimuli (200 microseconds duration, 0.5 mA, and 5 Hz) were given to the vestibular nerve for 10 min, an increase in the release of glutamate was observed in the MVN but not in the spinal trigeminal nucleus. These findings indicate that glutamate is the afferent neurotransmitter from the vestibular nerve to the MVN neurons.

Afferent Pathways↗
PubMed2000

Comparison of postoperative headache after retrosigmoid approach: vestibular nerve section versus vestibular schwannoma resection.

OBJECTIVE: To evaluate intradural drilling as a mechanism for the development of postoperative headache after retrosigmoid craniectomy. STUDY DESIGN: A retrospective review of charts was performed on 565 retrosigmoid approaches to the cerebellopontine angle performed between January 1980 and January 1998. Patients treated with retrosigmoid vestibular nerve section without intradural drilling were compared with patients who underwent retrosigmoid removal of vestibular schwannomas in which intradural drilling was performed for exposure of the internal auditory canal. SETTING: Private practice tertiary referral center. PATIENTS: Consecutive patients undergoing retrosigmoid approach between January 1980 and January 1998 were reviewed. MAIN OUTCOME MEASURES: The presence of headache, duration of headache, and severity of headache were noted. RESULTS: In this large series, 54% of patients experienced headaches after vestibular schwannoma removal, and 5% of patients experienced headaches after vestibular nerve section (p < 0.01, chi-square). CONCLUSIONS: Postoperative headache is not a characteristic of retrosigmoid craniectomy in the absence of intradural drilling. Intradural drilling is a probable cause of headache after the retrosigmoid approach. Cranioplasty is not necessary to prevent a high incidence of postoperative headache after retrosigmoid approach.

Adolescent↗
PubMed2002

Vestibular function after acoustic neuroma removal with preservation of one branch of the vestibular nerve.

BACKGROUND: Vestibular compensation after acoustic neuroma surgery is affected by many parameters. Apart from surgical approach, age of the patient, and comorbidity, the use of rehabilitative vestibular training and the degree of preoperative vestibular compensation play their respective roles. OBJECTIVE: To examine whether and how surgical preservation of one branch of the vestibular nerve affects the compensation process in patients after acoustic neuroma removal. STUDY DESIGN: Prospective study involving 29 patients with acoustic neuromas. In 15 patients operated on by the middle fossa or retrosigmoid approach, one branch of the vestibular nerve could be preserved intraoperatively, and the course of the compensation process was followed (Group 1). Fourteen other patients with acoustic neuroma, who were operated on via a translabyrinthine approach, served as a control group (Group 2). MAIN OUTCOME MEASURE: The evaluation of vestibular compensation was accomplished clinically, by electronystagmography, and by dynamic posturography. RESULTS: An accelerated vestibular compensation was found in all examinations for Group 1, and 3 months after surgery 47% of the patients in this group were back to work without substantial restrictions, compared with 29% of Group 2. At the end of 6 months, however, there was no more significant difference between the two groups. CONCLUSION: The long-term results of vestibular compensation do not seem to be influenced by partial preservation of the vestibular nerve, whereas the compensation process seems to be accelerated when the nerve is partially preserved.

Electronystagmography↗
PubMed1981

[The function of the human posterior vertical canal and the extent of central compensation in unilateral dissection of the vestibular nerve].

The vestibular nerve innervates the semicircular canals through two branches. The first branch innervates the anterior vertical and the horizontal canals and the second branch innervates the posterior vertical canal. In transtemporal neurectomy the dissection of the vestibular nerve was sometimes only in the upper part. In these cases the fibres to the posterior vertical canal are still intact. In Düsseldorf 41 patients were treated by transtemporal neurectomy from 1970 until 1977. Five of these patients show an incomplete dissection of the vestibular nerve. They had a normal endolymph circulation with afferent nerve fibres only from the posterior vertical canal. These patients were examined by caloric and rotatory stimulation in different head positions. Vertical and horizontal eye movements were simultaneously recorded. The stimulation of the posterior vertical canal shows a rotatory eye movement. The results were compared with the second Ewald law.

Caloric Tests↗
PubMed1992

Cochleovestibular nerve compression syndrome. II. Vestibular nerve histopathology and theory of pathophysiology.

The present study was undertaken to systematically examine and characterize pathological changes in vestibular nerve specimens obtained at surgery in patients with symptomatic cochleovestibular nerve compression syndrome (CNCS). Vestibular nerves were obtained in six cases of CNCS and were intermingled with vestibular nerves obtained in cases of Meniere's disease. All of the nerve specimens were coded and reviewed microscopically in a blind-study fashion by the neuropathologist. The vestibular nerves obtained from CNCS cases showed significant endoneurial fibrosis, compared to controls (specimens from patients with Meniere's disease). Based on observations in this study, as well as the clinical symptoms and audiovestibular test findings in these patients, a theory of pathophysiology in CNCS of the cochleovestibular nerve is proposed. The implications of this theory are discussed with respect to the diagnosis of CNCS.

Axons↗
PubMed1998

Analysis of patients with persistent dizziness after vestibular nerve section.

Vestibular neurectomy can be an effective operation for the control of persistent dizziness refractory to medical treatment or even endolymphatic sac surgery. Past studies have reported favorable results, creating an almost deceptive impression of the procedure's success rate. However, not all patients will respond favorably. Some will continue to have significant postoperative disequilibrium and, worse yet, persistent vertigo. To analyze the reasons for continued problems, 142 patients undergoing various surgical approaches employed to divide the vestibular nerve (retrolabyrinthine, middle fossa, retrosigmoid and translabyrinthine) were retrospectively, reviewed. Twenty-nine patients (20%) continued to have significant dizziness despite vestibular neurectomy. The reasons for failure were incomplete vestibular nerve section, poor central nervous system compensation, new vestibular disease in the opposite ear, obstructive anatomy, the presence of other central nervous system diseases, and unknown causes. This paper will detail the advantages and disadvantages of various vestibular neurectomy approaches and will present recommendations for further treatment of this difficult-to-manage group of patients.

Adult↗
PubMedDate not supplied

[Response of the hypothalamic neurons to stimulation of the vestibular nerve and lateral vestibular nucleus in rabbits].

Effects of single, double, and rhythmic stimulation upon hypothalamic neurons responding to the 1st excitatory phase of lateral vestibular nucleus stimulation, were studied. The data obtained show that activation of some hypothalamic neurons following stimulation of the lateral vestibular nucleus has a monosynaptic character. The findings suggest that ascending afferents from the lateral vestibular nucleus to the hypothalamus pass via oligo- as well as polysynaptic pathways.

Afferent Pathways↗
PubMedDate not supplied

Vestibular nerve section.

INTRODUCTION: Vestibular nerve section is considered to be the most effective surgical procedure for control of intractable symptoms secondary to labyrinthine and eighth nerve function. This study was developed to retrospectively evaluate the efficacy of vestibular nerve section in patients treated for disabling labyrinthine dysfunction. METHODS: A retrospective review of hospital and office records was carried out on 39 patients who underwent vestibular nerve section. All patients received a comprehensive questionnaire to subjectively evaluate efficacy. RESULTS: Questionnaires were returned from 36 of 39 patients. Follow-up averaged 51 months. A decrease in vertiginous attacks was reported by 94% of patients. An improvement in activity tolerance was reported by 30% of patients. Preoperative tinnitus and ear fullness reportedly improved after surgery in 53% and 65% or patients respectively. Complications encountered included cerebrospinal fluid (CSF) leak (six patients), meningitis (two patients), and intracranial fluid collection (one patient). CONCLUSION: Vestibular nerve section is a relatively safe and effective method of treatment for intractable vertigo.

Activities of Daily Living↗