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At least 1,207 records · Page 67Linked to original sources
PubMed2005

Vestibular dysfunction of patients with mutations of Connexin 26.

The gap junctional network of the inner ear plays an important role in cochlear ionic homoeostasis. Mutations of connexin 26 can induce different types of hearing loss and even deafness. Therefore, it is hypothesized that gap junctions of the human vestibular organ are functionally impaired by mutations of connexin 26. In a prospective, nonrandomized study, the functional status of the semicircular canals and the otolith organs was assessed in one homozygous and six heterozygous carriers of connexin 26 mutations. Five out of seven patients (71.4%) had pathological vestibular evoked myogenic potentials, indicating a loss of saccular function. The utricular function (as tested by subjective haptic vertical) and the function of the semicircular canals (as tested by recording the vestibuloocular reflex) were largely normal. Thus, connexin 26 mutations can be associated with saccular defects of the vestibular receptors.

Adult↗
PubMed1978

Visual suppression test.

The visual suppression test is one of the visual fixation tests. It is performed by recording caloric nystagmus by ENG, and the maximum slow phase velocity of caloric nystagmus in darkness is compared with the slow phase velocity in light with eyes open. Visual suppression of slow phase velocity of caloric nystagmus is 54 +/- 12% in 52 normal adults ageing from 21 to 40. Visual suppression in normal subjects is not influenced by water temperature used for the caloric test and not changed by background illumination in light. Visual suppression is stronger when the target is closer to the eyes of the subjects. The following abnormalities have been diagnosed by this test: flocculus and nodulus lesions on the side of the lesion; inferior olive lesions; parietal lobe lesions; compensation after unilateral sudden loss of inner ear function.

Adult↗
PubMed2002

Perception of slow pitch and roll body tilts in bilateral labyrinthine-defective subjects.

The aim of the present study was to examine whether the perception of slow body tilts in total darkness was affected by a complete loss of vestibular function. Four blindfolded bilateral labyrinthine-defective subjects (LDs) and 12 normal subjects (Normals) were seated and immobilized with large straps against the back of a rotating L-shaped platform, and were passively displaced from the upright at 0.05 degrees x s(-1) in the pitch and roll dimensions. Subjects were asked to detect the slow change in their body orientation, by indicating as soon as possible the direction of tilt. After a brief period of practice observed for all LDs at the beginning of the session, results showed no significant difference between LDs and Normals in the mean detection threshold recorded for each direction of tilt. The mean perceptual threshold was 4.4 versus 5.1 degrees in the roll dimension, and 6.1 versus 6.1 degrees in the pitch dimension, for the LDs and Normals, respectively. These findings indicate that the accurate perception of body orientation in quasi-static conditions is mainly allowed by somatosensory information rather than by otolithic inputs.

Adult↗
PubMed2002

Vestibular compensation after ganglionectomy: ultrastructural study of the tangential vestibular nucleus and behavioral study of the hatchling chick.

The tangential nucleus is a major part of the avian vestibular nuclear complex, and its principal cells are structurally distinctive neurons participating in the vestibuloocular and vestibulocollic reflexes. After unilateral peripheral vestibular lesion, a behavioral recovery of function defined as vestibular compensation is observed. Because sprouting and hypertrophy of synapses have been reported in other regions of immature animals after central nervous system injury, we investigated whether this also occurs in the vestibular nuclei during compensation. To test this hypothesis, unilateral vestibular ganglionectomy was performed on 4-6-day-old hatchlings and vestibular function was tested during the next 2 months. Degeneration and evidence for regeneration of synapses were studied in the tangential nucleus at 1, 3, 7, and 56 days after surgery. Spoon endings, large vestibular terminals on the principal somata, degenerated 1-3 days after surgery. However, the small synaptic terminals showed no significant change in the percentage or number covering the soma or in mean terminal lengths in the deafferented or contralateral tangential nucleus. Furthermore, there was no evidence of neuron death in the tangential nucleus. Vestibular compensation occurred in three stages: 0-3 days, when vestibular synapses degenerated and severe behavioral deficits were seen; 4-9 days, when primary vestibular fibers degenerated centrally and marked improvement in both the static and the dynamic symptoms were observed; and 10-56 days, when changes in neuronal morphology were not detected but the dynamic symptoms gradually improved. Accordingly, after unilateral vestibular ganglionectomy, vestibular compensation proceeded without ultrastructural evidence of sprouting or hypertrophy of axosomatic synapses in the hatchling tangential nucleus. This rapid behavioral recovery of function distinguishes the vestibular system from other sensory systems, which, in general, exhibit much less robust recovery after injury to their peripheral receptors.

Adaptation, Physiological↗
PubMed2004

Delayed vertigo after stapes surgery.

OBJECTIVES: Stapes surgery restores partial or total hearing in almost 95% of cases, and in case of failure, revision surgery may often resolve the problem. Delayed vertigo is commonly related to perilymphatic fistula. The aim of this study is to report experience gained in revision stapes surgery in cases of delayed vertigo. STUDY DESIGN: This is an intervention study, before-after trial; it includes follow-up between 12 and 84 months that was based on clinical history and audiometric evaluations. METHODS: The work was carried out in the otologic surgery referral center of Piemonte in outpatient surgery. Nine patients (4 males and 5 females, between 43 and 60 years of age) who presented with delayed vertigo after stapes surgery were retrospectively reviewed. All nine underwent clinical history evaluation, pure tone audiogram, investigation of the vestibular system with a bithermal binaural caloric test, and fistula test. Vestibular tests were performed with electronystagmography recording. In all nine subjects, functional middle ear exploration was carried out by way of a transmeatal approach using local anesthesia. The demonstration of a perilymphatic leak was positive in only three (33%) cases, but the oval window region was filled with fibrin glue in all nine cases. RESULTS: At follow-up, vertigo was resolved in all cases with revision surgery, even though perilymph leak was positive only in three cases. CONCLUSION: From the results obtained, we feel that exploration of the middle ear should be always carried out in cases of delayed vertigo after stapes surgery with suspected perilymphatic fistula.

Adult↗
PubMed1999

[The investigation of the audio-vestibular and oculomotor functions in people more than eighty years old].

OBJECTIVE: To investigate audio-vestibular and oculomotor functions of octogenarian. METHOD: The audition were measured with audiometry and auditory brainstem response. The semicrcular, oculomotor and balance functions were examinated by electronystagmography and posturography. RESULT: 1. The hearing abnormality of speech frequency were 84.1 percent by audiometry; 2. The abnormal rats of semicircular function and posturogram were 38.5% and 74.4% respectively. The body sway locus and velocity of octogenarians have increased as compared with the group of 60 years old in the posturography; 3. The latency of saccade was prolonged and total hearmonic distortion of pusuit was increased than that of 60 years old in the oculomotor test. CONCLUSION: The easily falling of octogenarians may be related to disturbing of semicircular oculomotor and equilibrational functions.

Age Factors↗
PubMed2005

[Vestibular evoked muscle potentials dependency on neural origin and the location of an acoustic neuroma].

INTRODUCTION: Most acoustic neuromas (AN) originate from the inferior vestibular nerve (IVN). Vestibular evoked myogenic potentials (VEMP) are accepted as the only unilateral test for the function of the sacculus and the IVN. METHODS: The influence of the origin from the IVN and superior vestibular nerve (SVN), and the position of the AN in relation to the internal auditory canal on VEMPs was investigated. A total of 39 patients (aged: 30-67 years, mean: 53 years) were examined. The VEMPs were recorded on the activated sternocleidomastoid muscle and averaged over 200 stimuli. Tone bursts (95 dB nHL; 500 Hz; stimulation rate 5 Hz) were used to generate the VEMPs. RESULTS: The exact origin of the AN from the SVN or the IVN could be determined intraoperatively and correlated using VEMP in 28 patients. CONCLUSION: The origin of the AN has only a marginal influence on the results of VEMP measurements. The position of the AN in relation to the internal auditory canal seems to have more influence than the origin.

Acoustic Stimulation↗
PubMedDate not supplied

Vestibular tests in the selection of cosmonauts.

Vestibulo-vegetative disorders in cosmonauts and astronauts occurring during space flight compel otolaryngologists to search for vestibular tests enabling a precise evaluation of the activity of the vestibular apparatus and showing disposition to motion sickness. Otoneurological investigation of Polish candidates for cosmonaut status consisted of the following vestibular tests: caloric, rotatory, optokinetic, swinging torsion, statokinesimetric and vestibulo-vegetative. The value of various vestibular tests for aviation and space medicine is presented in this paper, taking into account the results of investigations of the equilibrium system with the group of pilots selected for space flight as well as extensive experience with candidates for the air service and also trained pilots and patients. The relatively frequent lack of correlation between the results of the applied tests, which renders difficult the proper evaluation of the equilibrium system, is emphasized in the paper. Finally, the results of investigations of acute habituation of the vestibular apparatus are discussed.

Adult↗
PubMed1987

The effects of alerting tasks on caloric induced vestibular nystagmus.

The present study compared the effects of four different mental altering tasks on the speed of the nystagmic slow component during caloric testing in 40 young adults. Subjects were randomly divided into four groups (10/group) and stimulated twice in each ear in a counterbalanced manner according to test ear, irrigating temperature, and alerting task. Analysis of the data revealed significant differences between treatment effects on the magnitude of the slow phase velocity of nystagmus. Results suggest that passive listening does not sufficiently alert subjects to ensure the adequate release of nystagmus suppression during vestibular testing.

Acoustic Stimulation↗
PubMed1979

The mechanism of inhibition of caloric nystagmus by eye closure.

24 normal adults and 324 clinical cases were examined, for the purpose of shedding light on the mechanism of inhibition of caloric nystagmus by eye closure. When the eyes were closed, an eye was suddenly adducted 13 +/- 5 degrees and elevated 55 +/- 11 degrees. These adductive and upward eye movements were normal responses caused by eye closure. Caloric nystagmus was inhibited by upward eye deviation. With the turning down of the vertical eye position, the caloric-nystagmus inhibition was released. During eye closure, there were four types of vertical eye-movement responses: (a) holding the eye position up, (b) fluctuation around an upward eye position, (c) gradual downward turning, (d) sudden downward turning, Types a, b and c were seen in normal subjects. However, type d was not seen in normal people.

Caloric Tests↗