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PubMed1998

Body response to binaural monopolar galvanic vestibular stimulation in humans.

We investigated the possibility of obtaining an anteroposterior body response to galvanic vestibular stimulation (GVS) by applying an equivalent stimulus to both sides of the vestibular apparatus. An original 'double fronto-mastoidal' stimulation was used on eight subjects standing with their head facing forwards. Both the onset and the cut-off of the current did induce an anteroposterior body tilt, without any lateral component. The amplitude of the tilt increased as a function of stimulus intensity. GVS evokes anteroposterior or lateral sway of similar spatio-temporal features according to the stimulation configuration. We suggest that the central nervous system makes use of the discrepancy between the left and right vestibular activity to orientate the response: equivalent afferent flows would result in an anteroposterior body response whereas lateral sway is obtained with discrepant ones.

Adult↗

PubMed1980

Male and female characteristics in vestibular testing: a step toward the selection of the best participants for space flight.

Vestibular disturbances in connection with space flight were reported by a majority of participating astronauts and cosmonauts. These include motion sickness symptoms in the first few days of the space flight, as well as standing, gait and orientation disturbances after the return to Earth. The Aerospace Medical Community has been trying to select those people that are particularly adapted to the above stresses or that can be further adapted through training programs. As the circle of selectees extends to women, the problem arises as to whether differences between men and women exist under the conditions of space flight. In seeking answers to this question we studied a group of 42 women and 44 men, who were further subdivided according to their subjective motion sickness sensitivity, as determined by a questionnaire. Using this material, 26 men and 22 women were designated as motion sickness resistant, and 18 men and 20 women were designated as nonresistant. The vestibular test battery given these test subjects consisted of caloric, rotatory, optokinetic, vestibulo-spinal and vestibulo-vegetative testing. Because of the mixed orthostatic and vestibular problems seen after space flights, we also studied the response of the vestibular apparatus during peripheral blood pooling as induced by lower body negative pressure. The collected historical and test data are analyzed in this paper with emphasis on the relationship to motion sickness tendency.

Aerospace Medicine↗

PubMed2000

Orientation of the body response to galvanic stimulation as a function of the inter-vestibular imbalance.

We proposed to study and quantify the anteroposterior component, on top of the lateral one, of the body sway induced by different configurations of galvanic vestibular stimulation (GVS) in order to advance the understanding of the orientation of the response. Four stimulation configurations were used in two separate experiments: monaural, binaural, and opposite double monaural in the first experiment (11 subjects); monaural and double monaural in the second (13 subjects). The postural response of the subjects, standing with their eyes closed, to the stimulus (0.6 mA, 4 s) was assessed by measuring the displacement of the center of pressure (CoP) using a force platform. As usual, binaural GVS induced a strictly lateral deviation of the center of pressure. The opposite double monaural condition induced a similar lateral sway to that obtained in the binaural mode, although with a very different stimulation configuration. Monaural GVS induced an oblique, stereotyped deviation in each subject. The anteroposterior component comprised a forward deviation when the anode was on the forehead and a backward deviation when the anode was on the mastoid. The lateral component, directed towards the anode as in the binaural design, was twice as large in the binaural than in the monaural mode. The second experiment showed that double monaural stimulation elicited an anteroposterior deviation (backwards when the anode was on the mastoids and forwards when it was on the forehead) that was equivalent to the addition of two complementary monaural configurations. The present results show that monaural stimulation activates one side of the vestibular apparatus and induces reproducible, stereotyped deviations of the CoP in both the anteroposterior and lateral plane. Secondly, binaural GVS appears to result from the addition of two complementary monaural stimulations. Lateral components of the response to each stimulation, being in the same direction, are summed, whilst anteroposterior components, being in opposite directions, cancel each other out. The opposite happens when both labyrinths are polarized in the same way, as in the double monaural configuration. We suggest that the orientation of the response to GVS is a function of the imbalance between right and left vestibular polarization, rather than a function of the actual position of the electrodes.

Electric Stimulation↗

PubMed1998

Caloric response and postural control in patients with nasopharyngeal carcinoma after radiotherapy.

Since radiotherapy is the treatment of choice for nasopharyngeal carcinoma, the influence of irradiation on the temporal bone is of great concern for these patients. In this study, the caloric test and posturography were used to investigate vestibular function in 41 irradiated patients with nasopharyngeal carcinoma. Caloric testing showed a high incidence of canal paresis; five unilateral and 10 bilateral. Factors such as middle ear effusion had no significant effect on the occurrence of canal paresis. Posturography showed no difference from the control group. The authors conclude that the influence of irradiation on the vestibular apparatus of patients with nasopharyngeal carcinoma might result in a canal paresis, while postural control is preserved. Central compensation may play an important role in the postural control of these patients.

Adult↗

PubMed1994

[Instrumental study of vertigo: when and how?].

Any case of vertigo and equilibrium disorder for which an origin is not rapidly determined requires exploration for diagnosis. This exploration comprises two parts: first, that of peripheral components, including a standard audiometric examination, completed by study of the evoked auditory potentials. This is followed by vestibular examination comprising at least caloric tests of both ears, usually associated with rotation tests; second, exploration of the central pathways, by electro-oculography, study of pursuit and saccadic movements. The techniques of posturography, especially dynamic posturography by the equi-test, allow determination of the role of the vestibular apparatus in equilibrium and to define the respective roles of the labyrinth, vision and sensitivity in equilibrium. The technique is rapidly developing and will no doubt include the study of coordination of head and eye movements, study of stabilisation of vision and the head, and in particular study of otolithic function.

Audiometry↗

PubMed1983

The effect of head position upon jaw reflexes in the rat.

The vestibular apparatus of the decerebrate rat was stimulated by tilting the head dorsally or ventrally, with or without an associated stimulation of neck afferents i.e. either the head alone, or the head and body together, was tilted. The effect of such conditions, upon short latency reflexes elicited in antagonistic jaw and hyoid muscles, was examined. Reflexes in the different jaw and hyoid muscles were affected differently when the head was tilted, whether or not neck movement was permitted. Variations in the pattern of response in different animals were explicable on the basis of the known variable recovery of neck reflexes opposing the influence of the vestibular afferents. Head position can therefore be an important but complex factor which may enhance or depress reflex activity differentially in the different masticatory muscles, at least in the experimental situation.

Animals↗

PubMed1986

[Critical remarks on the interpretation of the thermal reaction of the labyrinth to weightlessness and evidence for the validity of the extended Bárány theory].

The literature on the biophysics of the vestibular apparatus in weightlessness is reviewed. The results of caloric in the prone position are compared to those in the supine position. The rate of convection and expansion of the endolymph are evaluated. Bárány's theory continues to be valid, because the rate of convection forms a greater proportion of the effective total stimulus than expansion.

Caloric Tests↗

PubMed1976

[Vertical vergence pathways].

Two pathways for vertical vergence probably exist: the cortical one carrying a psycho-optical reflex, the other sub-cortical connected to the vestibular apparatus and more probably to the otolith system. The sub-cortical pathway is essentially a vestibulo-cerebellar oculomotor pathway; but in addition there certainly exist direct vestibulo-oculomotor connections and long tracts passing through the interstitial nucleus of Cajal and the reticular formation.

Afferent Pathways↗

PubMed1990

Nephrotoxic and ototoxic agents.

It is well established that many drugs, such as the aminoglycoside antibiotics and the chemotherapeutic drug cisplatin, are capable of inducing both nephrotoxicity and ototoxicity. The factors that selectively predispose the kidney and inner ear to the toxic effects of these agents as well as the mechanism by which damage is produced are not well defined. The two organs differ greatly in their exposure to these toxic agents. The kidney has an abundant vascular supply and tends to selectively concentrate a number of drugs within the renal cortex or medulla, often to toxic levels. The vascular supply of the inner ear is not as extensive. In addition, the stria vascularis of the cochlea may act as a functional regulator of drug entry into inner ear fluids. The absorption of drugs into perilymph and endolymph is poorly understood. Selective accumulation theories of drug accumulation in the inner ear must be questioned because of the results of recent pharmacokinetic studies, which give contrary data. Drug-induced ototoxicity and nephrotoxicity can be explained on a cellular level. Studies using radiolabeled gentamicin suggest that binding mechanisms of the drug to the plasma membrane of the outer hair cells of the cochlea and vestibular apparatus and to the brush border receptors of the renal proximal convoluted tubules are similar. This suggests the same receptor sites for aminoglycosides occur in otic and renal organs. Calcium channels are implicated because of the reversibility of aminoglycoside-induced changes in the cochlear microphonic by calcium and other divalent cations. Calcium channel blockers, such as verapamil, reduce the nephrotoxicity of a number of drugs that are also ototoxic. Studies are needed to assess potential prevention of ototoxicity by use of these same calcium channel blocking agents. Aminoglycosides concentrate within the lysosomes of renal proximal tubular cells. Possibly, they also may concentrate in lysosomes within the cells of cochlear and vestibular structures. Nephrotoxic heavy metals concentrate within proximal tubular cells and, some, such as lead or bismuth, specifically concentrate within intracytoplasmic or intranuclear inclusion bodies. Studies are necessary to determine if the same metals accumulate within the cochlear and vestibular cells, inclusion bodies, or both. These questions and others must be answered before it can be determined why many nephrotoxic drugs and agents are also ototoxic.

Adolescent↗

PubMedDate not supplied

[The effect of pyridoxine on the cerebral hemodynamics in vestibular disorders].

By means of hydrogen clearance on conscious rabbits with implanted platinum electrodes it was established that pyridoxine (1 and 10 mg/kg) used against the background of sea sickness decreased the dilatational reaction of the cerebral vessels occurring during the stimulation of the vestibular apparatus, reduced the blood supply to the cerebral hemispheres with insignificant changes of oxygen tension in the cortical structures, relieved acidosis and hypoxemia developing during sickness in the orthostatic position, increased oxygenation of the arterial blood without influencing significantly pathomorphological shifts in the brain tissue.

Animals↗

PubMed2002

Morphological changes in the frog cerebellar cortex after unilateral section of the statoacustic nerve.

To investigate a possible role of the cerebellum in vestibular compensation that follows a lesion to the vestibular apparatus, the morphological changes of the cerebellar cortex of adult frogs following unilateral statoacustic nerve section was analyzed by means of electron microscopy starting from 3 days after the neurectomy for up to 6 months. On the ipsilateral side, massive abnormality was found in all layers at early postsurgical intervals. This involved both nerve fibers and cell bodies. Fibers often appeared condensed or vacuolated with poorly compacted myelin sheath. Cells had electronlucent and vacuolated cytoplasm to varying extent. Alterations became less conspicuous after 30 days and after 60 days altered nerve cells were no longer present. On the contralateral side, only a few Purkinje and granule cells were affected at early postsurgical stages. This may derive from the fact that, in the frog, some of the vestibular primary afferents reach contralateral cerebellar cortex. At 30 days, alterations had substantially progressed, and at 60 days they involved all the cortical layers. Fiber debris was present in the granular and molecular layers and numerous Purkinje cells were electrondense and shrunken. This lateness in alteration may be a consequence of the prolonged silence of the vestibular nucleus contralateral to the lesion. At 4 and 6 months the tissue architecture was normal.

Animals↗

PubMed1990

[Stabilometry and definition of the threshold of galvanic vestibular stimulation in normal subjects: an experimental study].

The effect of the galvanic stimulation on the vestibular apparatus has been evaluated by registration on the postural deviations, using a stabilometry platform. We have studied the galvanic body-sway responses in a group of normal subjects, using a binauricolar bipolar stimulation, with the electrodes attached by means of surgical tape to the mastoid area. The records of body-sway responses have demonstrated in 80% of the considered cases a significant variation of all positional parameters after a current intensity of 2 mA, according the body sways toward the positive stimulus. At the same current intensity only five of the studied subjects have shown multidirectional swinging, in three cases joined with a subjective slight sway toward the ear stimulated with positive polarity. Therefore the galvanic test, joined with the posturography, proves to be a useful auxiliary method in vestibular investigation, allowing us to lower the threshold of galvanic stimulation and to make the electric stimulus better supported for the patient.

Adult↗

PubMed1993

[Electron-microscopic study of the vestibular dark and wall cells].

The ultrastructure of the dark cells and wall cells in the vestibular apparatus of the healthy guinea pigs (21 ears) and disordered guinea pigs (12 ears) were observed using transmission electron microscopy. The results showed that otoconia were absorbed mainly by the dark cells, secondly the wall cells. A non-cellular substance was found on the surface of the dark and wall cells and in the endolymphatic space. Probably this substance is related to the absorption of otoconia, particularly the disordered otoconia.

Animals↗

PubMed2006

Ocular vestibular evoked myogenic potentials (OVEMPs) produced by air- and bone-conducted sound.

OBJECTIVE: To determine the origin and properties of short latency extraocular potentials produced by activation of the vestibular apparatus using two modes of acoustic stimulation. METHODS: Extraocular potentials were measured in 10 normal subjects using a bipolar montage to increase selectivity. Three dimensional eye movements were also recorded in five subjects. The subjects were stimulated with both air-conducted (AC) and bone-conducted (BC) sound using a single cycle of a 500Hz sine wave. RESULTS: Short latency positive and negative potentials that peaked at 8.1-12.7ms for AC and 7.5-13.9ms for BC stimulation were recorded, which were distinct for the two eyes and for the two modes of stimulation. The extraocular potentials began prior to the onset of eye movements, which peaked at 16.5-20.1ms for AC, 17.8-25.0ms for BC stimulation. CONCLUSIONS: The pattern of short latency eye movements and extraocular potentials induced by AC and BC vestibular stimulation are distinct. As the potentials preceded the eye movements and were not correlated morphologically with them, the source of the observed potentials is not an eye movement and thus we refer to them as ocular vestibular evoked myogenic potentials (OVEMPs). SIGNIFICANCE: The potentials had properties consistent with modulation of the electromyogenic activity of the extraocular muscles and if interpreted as originating from displacement of the eye will give misleading results. AC and BC acoustic stimulation are likely to activate differing profiles of vestibular end organs.

Acoustic Stimulation↗

PubMed1994

[Reeducation of patients with vertigo].

The use of physical therapy in the treatment of vertigo is based on the plasticity and the restoration and adaptive qualities of the vestibular apparatus. Indications for physical therapy and the choice of techniques are based on the location of the lesions: exercises aimed at habituation in positional vertigo, with use of the rocking manoeuvre in the case of cupulolithiasis, and stimulation of spinal, labyrinth, visual or extraocular muscle proprioceptors in the case of unilateral lesions of the first neuron or in ototoxic destruction. These techniques give lasting effects and avoid prolonged treatment by anti-vertigo drugs which, by impairing the development of compensation, often lead to persisting functional disorders.

Humans↗

PubMedDate not supplied

Craniocorpography in the diagnosis and therapeutic indication of endolymphatic hydrops.

The glycerol test helps to establish the differential diagnosis between Ménière's disease and other vertigo disturbances, but the test becomes very long and in its primary form informs us only about the cochlear response to the osmotic changes produced by glycerol in the inner ear, and tells us nothing about the vestibular response. In patients with unilateral endolymphatic hydrops we have performed simultaneously the glycerol test with audiometric and craniocorpographic (CCG) control. The response of the vestibular apparatus to the glycerol becomes evident in 84.5% of cases on average in 30 min. By contrast, the variation in the hearing-threshold appears in only 54% of cases and required on average 60 min. At the same time, CCG is easier and shorter to perform than audiometry, showing five different types of response to glycerol. The combined use of audiometry and CCG allows us to predict with sufficient accuracy the response of the endolymphatic hydrops to the treatment, simplifying the therapeutic indication and the choice of the surgical technique.

Adult↗

PubMed1999

A new mouse insertional mutation that causes sensorineural deafness and vestibular defects.

This article describes a new recessive insertional mutation in the transgenic line TgN2742Rpw that causes deafness and circling behavior in mice. Histologic analysis revealed virtually complete loss of the cochlear neuroepithelium (the organ of Corti) in adult mutant mice. In association with the neuroepithelial changes, there is a dramatic reduction of the cochlear nerve supply. Adult mutants also show morphological defects of the vestibular apparatus, including degeneration of the saccular neuroepithelium and occasional malformation of utricular otoconia. Audiometric evaluations demonstrated that the mice displaying the circling phenotype are completely deaf. Molecular analysis of this mutant line revealed that the transgenic insertion occurred without creating a large deletion of the host DNA sequences. The mutant locus was mapped to a region on mouse chromosome 10, where other spontaneous, recessive mutations causing deafness in mice have been mapped.

Animals↗

PubMed1999

Vestibular semicircular canal epithelium of the rat in culture on filter support: polarity and barrier properties.

The inner ear of mammals contains the vestibular apparatus which is involved in the maintenance of posture and balance. The tubular structure of the apparatus is bathed by the potassium-rich endolymph and sodium-rich perilymph in the luminal and abluminal compartments, respectively. The luminal compartment is lined by a continuous epithelium with islets of receptor organs, which separates the luminal from the abluminal compartment. The present work focuses on the epithelium, without the receptor organs, and shows that it can be reconstituted in culture. The epithelium from 4-day-old Wistar rats was grown on microporous membranes. High transepithelial electrical resistances (4000-6000 Omega.cm2) were achieved after 4-8 days in culture. The epithelium was characterized by the presence of cytokeratin, ZO-1 protein, occludin, and the presence of tight junctions and kinocilia. The transepithelial resistance of the cell monolayer withstood endolymph/perilymph dual bathing when the apical pole of the cells was in contact with endolymph, but collapsed in the reverse configuration. Weak but statistically highly significant basal to apical rubidium (86Rb) transport was observed. These findings show that this epithelium maintains its in vivo polarity and could enhance the potassium composition of endolymph up to maturity. This new culture model, in which dual bathing is possible, should enable further in vitro studies of the sensory vestibular epithelia.

Animals↗