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Results for “VESTIBULAR APPARATUS”

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At least 523 records · Page 29Linked to original sources

PubMed1999

[Traverse connectivity of innervation in the vestibular sensory epithelium].

OBJECTIVE: To further understand the traverse connections of nerve components in the vestibular sensory epithelium. METHODS: The nerve innervations in the vestibular sensory epithelia and infraepithelia of ten healthy guinea pigs (16 ears) were observed by transmission electron microscopy. RESULTS: Type I sensory cells were intricately connected with type II cells. Afferent and efferent fibers as well as their endings had also complicated connections with nerve trunks and branches. The traverse connections appeared among nerve components in the vestibular sensory epithelium were extremely complicated, forming multilevel connections. They stemmed from and end in the crista ampullaris and the maculae. CONCLUSION: These complicated and multilevel connections are the basis of nerve activity in the vestibular apparatus.

Animals↗

PubMed1991

[The cytoskeleton of the Mauthner neurons in the guppy after returning from an orbital flight].

The ultrastructural investigations of the Mauthner neurons (M-cells) of P. reticulata were performed on the return of the fishes after a two weeks orbital flight, the M-cells of fishes from different control groups being simultaneously examined. The structure of M-cells from the experimental fishes was shown to be severely damaged. The changes involved the synaptic apparatus, postsynaptic areas, mitochondria and other organelles of the cytoplasm and the nucleus. Particular changes were seen in the neuronal cytoskeleton. While in the M-cells of intact fishes these were seen as evenly distributed microfilaments and neurofilaments, in the M-cells of experimental fishes the cytoskeleton looked as alternating bundles of condensed filaments. The first indications of cytoskeleton damage appeared in M-cells of the guppy from transport control group and strengthened in fishes from the group of synchronous control. Thus, the data obtained give us a possibility to suggest that the return on the Earth and following readaptation after a prolonged flight at conditions of microgravity and consequent disfunction of vestibular apparatus may result in the damage of central neurons receiving vestibular afferentation (such as M-cells). That, in turn, may be a cause of functional disorders of the central nervous system, including the nerve centres maintaining the organs of motion. These facts are necessary to take into consideration when more prolonged cosmic flights are planned.

Animals↗

PubMed1989

[Relationship between directions of cerebellar retractions and cochlear and vestibular nerve injuries].

It is said that lateral-to-medial retraction of the cerebellar hemisphere is hazardous because, by this retraction, avulsion injury of the cochlear nerve and internal auditory artery may be caused. Caudal-to-rostral retraction of the cerebellar hemisphere is, therefore, recommended in operations in the CP angle such as microvascular decompression procedures. From the results of our present study, however, it can be said caudal-to-rostral retraction can easily cause vestibular nerve damage. However, rostral-to-caudal retraction may damage the cochlear nerve just as lateral-to-medial retraction does. These differences of the eighth nerve injuries according to directions of cerebellar retractions are explicable from the fact that the vestibule and vestibular nerve are located posterior to the cochlea and cochlear nerve. Most of dysequilibrium appearing after manipulations in the CP angle may be due to vestibular nerve damage-avulsion of the vestibular nerve and its accompanying vessels from the vestibular apparatus.

Action Potentials↗

PubMed1980

[Vestibulometry in young children with infantile cerebral palsy].

A total of 648 vestibulometric observations of young children suffering from infantile cerebral paralysis revealed diverse vestibular disorders in 85% of the cases. Electronystagmographic findings make it possible to evaluate the functional potentialities of the child's brain in the conditions of cerebral pathology. A certain connection between the vestibular and the motor disturbances is noted. A high sensitivity of the vestibular apparatus to intracranial hypertension in the stage of its clinical compensation is revealed. The vestibulometric findings are used for forecasting the disease outcome and diagnosing disturbances of not only the vestibular, but also of the visual analyzer. The results of the study make it possible to evaluate the sick child's state most completely as early, as in the initial stages of the disease, and to outline the therapeutic strategy.

Ataxia↗

PubMed1989

[The vestibulospinal reflex and its tests].

Examination of vestibulospinal reflexes is an integral part of investigation of the balance apparatus activity. Four tests were selected to verify its utility and reliability, i.e. Romberg (stand II) and Hautant's tests for examining tonic reflexes, Fukuda's stepping test and writing test to monitor how the vestibular apparatus affects coordinated movement. The latter was, however, eliminated from clinical usage due to its unreliability. The final assessment of vestibulospinal reflexes is made more precise by simultaneous evaluation of the three remaining tests.

Humans↗

PubMed2006

Oculomotor plasticity during vestibular compensation does not depend on cerebellar LTD.

Vestibular paradigms are widely used for investigating mechanisms underlying cerebellar motor learning. These include adaptation of the vestibuloocular reflex (VOR) after visual-vestibular mismatch training and vestibular compensation after unilateral damage to the vestibular apparatus. To date, various studies have shown that VOR adaptation may be supported by long-term depression (LTD) at the parallel fiber to Purkinje cell synapse. Yet it is unknown to what extent vestibular compensation may depend on this cellular process. Here we investigated adaptive gain changes in the VOR and optokinetic reflex during vestibular compensation in transgenic mice in which LTD is specifically blocked in Purkinje cells via expression of a peptide inhibitor of protein kinase C (L7-PKCi mutants). The results demonstrate that neither the strength nor the time course of vestibular compensation are affected by the absence of LTD. In contrast, analysis of vestibular compensation in spontaneous mutants that lack a functional olivo-cerebellar circuit (lurchers) shows that this form of motor learning is severely impaired. We conclude that oculomotor plasticity during vestibular compensation depends critically on intact cerebellar circuitry but not on the occurrence of cerebellar LTD.

Animals↗

PubMed1976

Temporal bone histopathology in experimental hypovitaminosis A.

Twenty-five years ago hearing loss was observed in some subjects during a comprehensive study of the effects of hypovitaminosis A on human volunteers. Experimental studies documenting histopathological changes in the temporal bone due to hypovitaminosis A are conflicting. Even the recent textbooks of otolaryngology and physiology make no mention of a role of vitamin A in the ear. To explore the role of vitamin A in the ear adult and weanling rats maintained on a diet totally lacking vitamin A were sacrificed at intervals. Their temporal bones were examined with the light microscope. After six weeks on a vitamin A free diet weanling rats showed hypertrophy of the periostial portions of the otic capsule. At 16 weeks a narrowing of the internal auditory canal due to bony exostoses was present. The neuroepithelia of the cochlea and the vestibular apparatus were histologically normal even in the longest surfiving animals. Adult rats maintained on a vitamin A free diet showed minimal thickening of the bone adjacent to the internal auditory meatus. The cochlea and the vestibular appartus in these animals remained normal throughout the 28-week experiment. Although we have demonstrated marked abnormalities of the otic capsule in hypovitaminosis A, our results do not support those of some earlier investigators who reported that atrophy of the cochlear and vestibular neuroepithelium occurred in the absence of dietary vitamin A.

Age Factors↗

PubMed1977

Functional organization of the vestibular input to the anterior and posterior cerebellar vermis of cat.

1. Responses evoked by electrical stimulation (auditory division of the VIIIth nerve sectioned chronically) and natural stimulation of the vestibular apparatus were recorded in the anterior and posterior cerebellar vermis of cats anesthetized with Ketamine or Nembutal. Under Ketamine the functional state of the cerebellar cortex was similar to that of the decerebrate or encéphale isolé preparation. 2. Vestibular-evoked responses were found bilaterally throughout the vermis (lob. I-X) and parts of pars intermedia and were, for the most part, mediated via the mossy fiber-granule cell pathway although natural stimulation occasionally evoked climbing fiber responses in Purkinje cells. 3. Lesion and stimulation experiments suggested that the polysynaptic potentials recorded in the dorsal folia of the anterior and parts of posterior vermis were mediated, at least in part, by the lateral reticular nucleus. Potentials recorded in the deeper folia often had shorter latencies and were probably mediated by primary and/or secondary vestibular fibers. Studies with horseradish peroxidase (injections in lob. V and VI) supported these notions. 4. An analysis of Purkinje cell responses to sinusoidal rotation and steps of angular acceleration or velocity indicated that P-cells in these regions signalled angular head velocity in the mid-frequency range. Single canal responses as well as multi-canal convergent P-cell responses were found. Purkinje cells also responded to static head displacement.

Animals↗

PubMed1988

Neurohumoral mechanism of space motion sickness.

This paper reviews existing hypotheses concerning the mechanisms of adaptation of the vestibular apparatus and related somatosensory systems to microgravity with reference to the flight data. Having in view theoretical concepts and experimental data accumulated in space flights, a conceptual model of the development of a funtional system responsible for the termination of vestibular dysfuntion and space motion sickness manifestations is presented. It is also shown that changes in the hormonal status during motion sickness induced by vestibular stimulation give evidence that endocrine regulation of certain functions can be involved in adaptive responses.

Adaptation, Physiological↗

PubMedDate not supplied

[The otoneurological symptoms in giant adenomas of the hypophysis].

Analysis of the otoneurological symptomatology in 32 patients with hypophyseal tumors showed that they extended most frequently into the sphenoidal sinus, the cells of the ethmoidal sinus, the superoposterior parts of the nose, and the nasopharynx. The focal symptoms of compression of the adjoining parts of the brain (frontal, temporal) were manifested in 11 among 32 cases by olfactory disorders (loss of olfaction in 4 patients, diminished olfaction in 2, olfactory hallucinations in 4 patients, and impaired recognition of odors in 1 patient). Asymmetric action of the tumor on the subcortical structures in the fronto-parietal-temporal parts was manifested by side asymmetry of the experimental nystagmus, complete spatial disorientation of the patient after the rotation test with a false sensation of collapse to the side of the slow phase of nystagmus with vigorous motor compensatory disharmonic deviation of the trunk and limbs in the direction of the rapid nystagmus phase. The effect of the giant hypophyseal tumor on the brain stem was often manifested for a large distance (simultaneously on the diencephalic level, on the level of the midbrain, and in the posterior cranial fossa). Among a group of 32 patients 18 had the decompensated phase of affection of the vestibular apparatus. The effect of the tumor on the diencephalic parts of the brain was attended by sharply intensified vestibulovegetative reactions which should be considered as a stimulation symptom. In giant cell hypophyseal tumors, however, intensification of vestibulovegetative reactions after experimental vestibular tests does not occur in many cases, which is due to death and areactivity of the diencephalo-hypothalamic structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗

PubMed1977

Toxicity of aminoglycoside antibiotics.

In cats, aminoclycosides cause vestibular damage followed in a few days by renal damage. The reverse is true in the dog, except that streptomycin causes vestibular damage prior to renal damage. To avoid toxicities, therapeutic doses of aminoglycosides should not be given longer than a week and they should be given cautiously in animals with renal impairment. Failure of the kidneys to eliminate aminoglycosides will result in very high blood levels, even with therapeutic doses, that can cause further renal and vestibular damage. The oral administration of aminoglycosides is seldom dangerous when normal therapeutic doses are employed. Although it is remote, the possibility exists that animals with renal impairment and intestinal obstruction may become intoxicated. Kanamycin is less nephrotoxic to dogs than neomycin and it is less destructive to the auditory nerve than vestibular damage than streptomycin. Gentamicin in cats is twice as toxic to the vestibular apparatus as streptomycin and more toxic to the cochlea than streptomycin or dihydrostreptomycin. Neomycin is more toxic than kanamycin, gentamicin, and streptomycin to both cats and dogs. Amikacin causes renal damage in dogs similar to other aminoglycosides. It also causes vestibular damage.

Aminoglycosides↗

PubMed1981

Temporal bone histopathologic findings in Down's syndrome.

We report the results of a histopathologic study of 12 temporal bones from seven patients with Down's syndrome and of a dimensional study of the cochlea and the vestibular apparatuses of most of these specimens. Histopathologic study disclosed numerous abnormalities of the middle ear but only a limited number of inner ear abnormalities. The dimensional study showed that, while in the majority of cases the cochlea was shortened, most of the vestibular measurements were within the normal range. We also discuss hearing loss in patients with Down's syndrome and present our hypothesis that remnants of mesenchymal tissue in the round window niche might cause a certain degree of conductive hearing loss in such cases.

Adolescent↗

PubMedDate not supplied

Participation of the medial reticular formation of the medulla oblongata in the supraspinal control of locomotor and postural activities in the guinea pig.

The influence of microinjections of novocaine (1.5 microliters of a 2% solution) into the ventromedial areas of the reticular formation of the medulla oblongata on the effects of electrical stimulation of the mesencephalic locomotor region, and of adequate stimulation of the vestibular apparatus, was investigated in experiments on decerebrate guinea pigs. It was demonstrated that such injections are accompanied by a reversible increase in the threshold of stimulation of the region indicated, necessary for the initiation of locomotor rhythmicity, as well as by the suppression of vestibular influences on the activity of the flexor muscles of the extremities. The role of the reticular formation of the brainstem in the supraspinal control of posture and locomotion is discussed.

Animals↗

PubMed1985

Posture-correlated responses to vestibular polarization in vermal versus intermediate posterior cerebellar cortex.

Cerebellar lesion experiments have led to the concept that the medial longitudinal zone controls postural tone while the intermediate zone controls discrete movement. This study is a test of the hypothesis that, of the two zones, the medial zone is more closely linked to the resting discharge of vestibular afferent fibers, a prime source of neural tonus underlying the tonus of posture. Unilateral polarizations of the vestibular apparatus via the round window in awake, unrestrained guinea pigs caused step changes of postural attitude, the direction of which was polarity dependent. In anesthetized animals, these currents caused nonadapting step changes, or posture-correlated responses in the level of resting discharge in vestibular primary afferent fibers. In the medial and the intermediate cerebellar cortices of the posterior lobe, the proportion of step-like responses was similar, in contradiction to the hypothesis. This suggests that the cerebellar computations for controlling both postural tonus and discrete movements require information about vestibular tonus in terms of simple spike activity.

Action Potentials↗

PubMed1984

Clinical monitoring of the effects of gentamicin by electrocochleography.

Eight patients receiving prolonged treatment with gentamicin for bacterial endocarditis were monitored for possible ototoxicity using transtympanic electrocochleography as an adjunct to pure tone audiometry, vestibular function tests and serum gentamicin levels. An immediate effect of intravenous gentamicin on the cochlea, shown by changes in the whole nerve action potential and/or cochlear microphonic was recorded in seven patients, none of whom had experienced vestibular or auditory symptoms with gentamicin prior to testing. Two patients subsequently developed evidence of vestibular dysfunction, and a high frequency sensorineural hearing loss occurred in a third individual. There have been no previous report of the immediate effects of gentamicin on the human cochlea to date. The significance of these findings in routine clinical monitoring of ototoxicity is discussed in the light of clinical and animal evidence for the possible mode of action of aminoglycosides on the auditory and vestibular apparatus.

Action Potentials↗

PubMed1979

[Vestibulo-ocular reactions by infants and young children (author's transl)].

Neurootological research demonstrated significantly different vestibulo-ocular reactions by infants and young children as compared to adults. Neurohistological research has demonstrated that the vestibular apparatus is developed by birth and therefore should be fully functional. Fifty full-term and healthy infants and children between 9 days and 24 months of age were placed on an electrically controlled rotating chair in order to determine the functional development of the vestibular system. The rotational test program consisted of a supraliminal acceleration stimulus of 3 degrees/s2, a constant rotation at 90 degrees/s for 3 minutes, and a final abrupt deceleration stimulus. The frequency and amplitude of the per- and post-rotatory nystagmus reaction were analysed from the electronystagmogram. The nystagmus frequencies demonstrate a low level in the first month. The per- and post-rotatory deviate clearly from each other in the following months. The amplitude values also start out low in the first month then climb thru the 7th month and finally stabilize or drop slightly in both the per- and post-rotatory phases. The accumulated results will be discussed and typical examples will be demonstrated.

Age Factors↗

PubMed2004

[The vestibular function in patients with various forms of chronic purulent otitis media].

A complex vestibulologic examination of 131 patients with otitis media purulenta chronica (OMPC) was made. The patients were divided into groups and subgroups basing on the course of OMPC and presence or absence of subjective vestibular disorders. Vestibular function was assessed in various OMPC forms. Vestibular abnormalities were found in all the examinees. Therefore, all OMPC patients should be examined vestibulologically for early detection of initial, subclinical changes of the inner ear vestibular apparatus and decision on treatment policy.

Adolescent↗

PubMedDate not supplied

[Characteristics of prolactin secretion in response to different degrees of lesions of the vestibular analyzer].

The prolactin concentration in blood of 58 patients was measured during vestibular crisis and compensation of vestibular disorders. The results were compared with the clinical development of the disease and localization of vestibular problems. Patients with acute vestibular lesions at the central level of vestibular disorders showed a significant increase of prolactin concentrations that was higher than the concentrations in patients with the peripheral vestibular syndrome at the decompensation stage. Hyperprolactinemia during central vestibular dysfunction is viewed as a manifestation of dopamine deficiency of the tuberoinfundibular area. It is suggested that inadequacy of dopaminergic structures is one of the factors reducing adaptive and compensatory capabilities of the vestibular apparatus when its central compartments are injured.

Adult↗