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At least 487 records · Page 27Linked to original sources
PubMed1993

[The effect of age on inhibition of visual fixation of the rotatory-induced nystagmus reaction].

The interactive functions between sensory systems show changes that depend on the development of the growing body. Important conditions for the development of the visual suppression of vestibular evoked nystagmus reactions are the maturation of the visual system, the presence of a functioning vestibular system and close connections between both systems. Response to vestibular, visual and combined vestibular and visual stimulation does not only change during early childhood. We have also learnt from studies of adults of different ages that there are characteristic changes in nystagmus reactions to vestibular stimulation, in optokinetic reactions and in vestibular-spinal functions during the whole period of life. 272 randomly selected neuro-otologic routine patients aged between one year and four months and eighty-eight years and ten months were included in the study to analyse age-related changes of visual suppression during rotatory stimulation. The rotatory stimulation consisted of an sinusoidal stimulus pattern with amplitudes of +/- 180 degrees and a period duration of 20s. The vestibular stimulation was performed in total darkness and with a visual target which was attached to the chair in front of the patient's eyes. The results of this study demonstrate that the amplitudes of nystagmus reactions, evoked by sinusoidal harmonic acceleration, can be quantitatively suppressed by visual fixation. The degree of suppression depends on age. The fixation indices provide the ability to measure the degree of this suppression in percent. The trend to better fixation suppression increases up to the end of the age of forty. The ability to suppress vestibular nystagmus decreases, however, after reaching the fortieth year of life. The analysis of smooth pursuit shows after the sixtieth year of life a continuous rise in the number of saccades with increasing age. These changes are caused by aging processes in cerebral tissues which lead to functional changes e.g. in the interactive functions between sensory systems.

Adolescent↗
PubMed1995

[Vestibular neuritis: a frequently unrecognized cause of diplopia].

The vestibular function plays an essential role in the stabilization of the image on the retina. In addition, when the head is tilted, it contributes to maintain horizontally the plane of the gaze. Vestibular changes can result in oscillopsia and/or diplopia. The latter is related to occurrence of a skew deviation. The authors emphasize the frequent occurrence of diplopia following disorders of the vestibular nerve, specially after vestibular neuritis. In clinical practice, the causal relationship between vestibular neuritis and diplopia is often unrecognized.

Adult↗
PubMed1992

[Strabismus induced by peripheral vestibular lesions].

Little attention has been paid in the ophthalmological literature to strabismus resulting from lesions located in the peripheral vestibular system. However, this phenomenon is commonly encountered in clinical practice. As a rule, this kind of strabismus shows a prominent vertical component. It is generally combined with a change in perception of verticality, conjugate cyclotorsion of the eyes, and head tilt. This association is known as "ocular tilt reaction". It occurs in a number of clinical settings which are believed to be related with alteration in the otolithical and/or vertical semicircular canal pathways. Strabismus occurring as a feature of ocular tilt reaction might result from different mechanisms according to the location of the lesion, e.g. in the utricles, in the midbrain tegmentum, and in the dorso-lateral medulla oblongata. This phenomenon is illustrated here with the report of a patient suffering from Ménière disease, who underwent selective vestibular neurectomy. Methods of ophthalmological evaluation in such cases is described.

Aged↗
PubMed2001

Three-dimensional analysis of eye movements during off vertical axis rotation in patients with unilateral labyrinthine loss.

3D analysis of eye movements during off vertical axis rotation (OVAR) was carried out in seven subjects with unilateral labyrinthine loss (ULL). The modulation component (MOC) of these patients was not different from that of normal subjects. However, the horizontal MOC was significantly smaller when the rotation was directed towards the diseased side as opposed to the healthy side. With rotation to the diseased side, most subjects exhibited a horizontal bias component (BIC) to the opposite side as compared with the diseased side in normal subjects. The vertical and torsional BICs were also influenced to some extent by lack of input from the unilateral labyrinth. These results indicate that a unilateral otolith organ plays a major role in the production of the horizontal BIC contralateral to the direction of rotation, which is strongly related to the velocity storage mechanism in the central nervous system. In addition, the unilateral otolith organ exerts some influence on the generation of the horizontal MOC and also the BIC of vertical and torsional eye movements.

Acceleration↗
PubMed2002

Changes in fos expression in the rat brainstem after bilateral labyrinthectomy.

In order to elucidate the role of the vestibulocerebellar neural circuits during two-stage bilateral labyrinthectomy (BL) we examined Fos-like immunoreactive (-LIR) neurons as a marker of neural activation in the rat brainstem after BL and the projections of these neurons into the vestibulocerebellum using retrograde tracing and immunohistochemical techniques. Simultaneous BL did not show any Fos expression in the medial vestibular nucleus (MVe). However, with an interval of > 6 h between the two stages of BL, Fos-LIR neurons were induced in the ipsilateral (ipsi-) MVe of the side operated on second, partially projecting into the ipsi-vestibulocerebellum. A previous study demonstrated that some of the unilateral labyrinthectomy-induced Fos-LIR neurons in the ipsi-MVe projected into the ipsi-vestibulocerebellum and inhibited the contra-MVe neurons, resulting in the restoration of the right-left balance. Taken together with our present data, it is suggested that some of the labyrinthectomy-induced Fos expression in the ipsi-MVe is representative of a switch-on signal for the vestibulo-cerebello-vestibular inhibitory neural circuits, which remain turned off after symmetrical lesions such as simultaneous BL but are turned on after severe asymmetrical lesions in order to restore the balance.

Adaptation, Physiological↗
PubMed2003

Otolith dysfunction during vertiginous attacks in Ménière's disease.

OBJECTIVE: Vertiginous attacks of Ménière's disease (MD) are characterized by various types of vertigo, namely rotatory vertigo, dizziness and drop attack. When a patient complains of dizziness without spontaneous nystagmus, otolith dysfunction cannot be ruled out. The purpose of this study was to evaluate otolith dysfunction during vertiginous attacks of MD or delayed endolymphatic hydrops. MATERIAL AND METHODS: Vestibular function tests were carried out daily for several days in 11 patients (MD, n = 9; delayed endolymphatic hydrops, n = 2) during vertiginous attacks. Otolith function was evaluated by means of the static torsional position of both eyes [static ocular torsion (OT)] whilst in an upright position. We defined otolith dysfunction as an abnormal change (range) in OT without spontaneous nystagmus or as an abnormal change in OT without a change in spontaneous nystagmus. RESULTS: Four patients had an abnormal change (range) in OT without spontaneous nystagmus or an abnormal change in OT without a change in spontaneous nystagmus during vertiginous attacks of MD. CONCLUSIONS: Otolith dysfunction occurs in patients during vertiginous attacks of MD. In cases of ataxia without spontaneous nystagmus, otolith dysfunction most likely causes atypical attacks of MD.

Adolescent↗
PubMed1998

Enhancement of GABA-mediated inhibition of rat medial vestibular nucleus neurons by the neurosteroid 20-hydroxyecdysone.

In vivo electrophysiological and patch-clamp studies were performed to determine whether 20-hydroxyecdysone (20-HE), a neurosteroid, influenced neuronal activities of the medial vestibular nucleus (MVN) using chloral hydrate-anesthetized rats and dissociated MVN neurons, respectively. Single neuronal activities of MVN were extracellularly recorded with a glass-insulated silver wire microelectrode attached along a seven-barreled micropipette. Each micropipette was filled with 20-HE, glutamate, bicuculline or 2 M NaCl. These chemicals were applied microiontophoretically to the immediate vicinity of the target neurons. Microiontophoretically applied 20-HE (20-80 nA) dose-dependently decreased rotation-induced firings of both type I and II neurons, which were identified according to their responses to horizontal sinusoidal rotations. Microiontophoretically applied bicuculline, a GABAA receptor antagonist, inhibited 20-HE-induced decreases in neuronal firing of MVN. These findings suggest that 20-HE potentiates the action of GABA, probably by acting directly on the GABAA receptor of MVN neurons. In addition, microiontophoretically applied 20-HE decreased firings induced by glutamate in both type I and II neurons. This decrease by 20-HE was also antagonized with bicuculline. Furthermore, the effects of 20-HE on GABA-induced currents in acutely dissociated MVN neurons were investigated using the whole-cell patch-clamp technique. Under voltage-clamp conditions, GABA (10 microM)-induced currents were potentiated in the presence of 20-HE (100 microM). These findings suggest that 20-HE inhibits MVN neurons by acting on the modulatory site on GABA receptor-ion channel complexes to potentiate GABA inhibition.

Animals↗
PubMed1975

Vestibular dysfunction in hereditary ataxia.

A kindred with a unique autosomal dominantly inherited ataxia of late onset is described. Manifestations of the condition include defective optokinetic nystagmus and absent or abnormal oculo-vestibular responses, in association with normal cochlear function. It is possible that these latter features may serve as "markers" to indicate the presence of the disease in presymptomatic young adults, thereby facilitating important genetic counseling.

Adolescent↗
PubMed2005

Torsional optokinetic nystagmus after unilateral vestibular loss: asymmetry and compensation.

The aim of this study was to analyse torsional optokinetic nystagmus (tOKN) in 17 patients with Menière's disease before and after (1 week, 1 month and 3 months) a curative unilateral vestibular neurotomy (UVN). The tOKN was investigated during optokinetic stimulations around the line of sight directed towards either the lesioned or the healthy side, at various constant angular velocities. Dynamic properties of tOKN and static ocular cyclotorsion were analysed using videonystagmography. Patients' performances were compared with those of 10 healthy subjects. The results indicate that, in the acute stage after UVN, patients exhibited drastic impairment of tOKN velocity that depended on the direction of stimulation: tOKN velocity increased for ipsilesional stimulations and decreased for contralesional stimulations. These changes were responsible for a dramatic tOKN asymmetry, with ipsilesional directional preponderance of torsional slow-phase eye velocity. The changes were associated with static ocular cyclotorsion towards the operated side. Despite progressive compensation of tOKN deficits over time, tOKN velocity still differed from that recorded preoperatively, and tOKN asymmetry remained uncompensated 3 months after UVN. A static ocular cyclotorsion remained up to 3 months after lesion. These results are the first description of tOKN deficits and recovery after unilateral vestibular loss. They show that vestibular cues contribute to gaze stabilization during optokinetic stimulation around the line of sight. They also strongly suggest that tOKN impairment could be part of the long-term asymmetrical functions reported after unilateral loss of vestibular functions.

Adult↗
PubMed1993

Neuro-otology.

New techniques for the assessment of vestibulospinal, neck-afferent, and viscerograviceptive function may show future clinical applications for a broader assessment of balance function in neuro-otological patients. Magnetic resonance imaging studies revealed that many intralabyrinthine disorders (labyrinthitis, hemorrhage, schwannomas) can be adequately visualized. Perceptual and oculomotor clinical studies improved our understanding of vestibular disordered function in the roll (coronal) plane. Therapeutic studies highlight the importance of a team approach, with individually tailored programs for the rehabilitation of patients with vestibular disorders. Reasonable agreement on the criteria for attempting hearing preservation during acoustic neuroma surgery seems to have been reached.

Brain Stem↗
PubMed2004

Ménière's disease.

PURPOSE OF REVIEW: Ménière's disease is characterized by spontaneous attacks of vertigo, fluctuating sensorineural hearing loss, aural fullness, and tinnitus. The pathologic process involves distortion of the membranous labyrinth with the formation of endolymphatic hydrops. This review describes the pathogenesis and etiology as well as the diagnosis and treatment of Ménière's disease. RECENT FINDINGS: Initial management of Ménière's disease can involve a low-salt diet and a diuretic. Treatment with intratympanic injection of gentamicin can be beneficial when vertigo persists despite optimal medical management. Recent studies have shown that gentamicin reduces vestibular function in the treated ear, although complete ablation of this vestibular function is not typically required in order to achieve control of vertigo. SUMMARY: Vertigo is often the most debilitating symptom associated with Ménière's disease. Many treatment options exist for the management of vertigo. Intratympanic injection of gentamicin (low dose) can be used in patients for whom vertigo has not been controlled by medical measures. Ongoing research is providing a greater understanding of the effects of gentamicin on vestibular function and of the mechanisms through which gentamicin leads to control of vertigo.

Combined Modality Therapy↗
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↗
PubMed2003

Vestibular compensation: analysis of postural re-arrangement as a control index for unilateral vestibular deficit.

Patients with an acute unilateral vestibular lesion show an impaired balance control. The initial presentation is vertigo followed by postural instability; but with time, the global balance functions can be completely restored by a process called vestibular compensation. The aim of our study was to evaluate short and long-term variations of postural parameters in 20 patients affected by vestibular neuritis (VN), and to compare these patients to 20 normal individuals using computerized static posturography (CSP) along with patient feedback throughout the spectral frequency analysis. This analysis showed in patients with no residual dizziness a frequency shift of body sway from low to middle frequencies as a probable expression of the compensatory strategies used by the central nervous system. On the other hand, patients with persistence of postural instability did not show any frequency shift. Our results seem to provide an early index of a proper occurring compensation so that we can adjust therapeutic protocols according to each patient's functional modifications.

Female↗
PubMed2006

Total sleep deprivation can increase vestibulo-ocular responses.

The effect of sleep deprivation on the vestibular function is largely unknown. Some studies have found that postural balance or vestibular reflexes are decreased in sleep-deprived subjects while others found no change. The aim of this study was to evaluate the effect of sleep deprivation on the vestibulo-ocular reflex (VOR). Horizontal eye movements were recorded in healthy subjects during earth vertical axis rotation in darkness once after an ordinary night sleep and once after 26-29 h of sleep deprivation. In the first experiment (n = 8), for which rotation was a 60 degrees s(-1) velocity step, sleep deprivation induced a significant increase in VOR gain. In the second experiment (n = 12), for which rotation was sinusoidal (0.2 Hz +/- 25 degrees s(-1)), sleep deprivation induced no significant modification in VOR gain. The difference between the two studies was the abrupt onset of the step stimulation in comparison with the sinusoidal rotation. Because of its unexpected onset and the potential threat to postural balance, the step stimulation may activate the system specialized in reorienting attention towards salient or behaviourally relevant events. This system includes the right temporoparietal cortex, an area also involved in VOR control. A number of studies have found that sleep deprivation alters the activity of this cortical area during attentional tasks. It is therefore our hypothesis that the difference between the effects of these two vestibular stimulations results from a sleep deprivation-induced modulation of the right temporoparietal cortex.

Adult↗