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At least 559 records · Page 31Linked to original sources
PubMedDate not supplied

Degenerative changes in the human vestibular sensory epithelia.

A study of the vestibular end organs from humans of different ages is presented. The inner ears were exposed by microdissection, and the vestibular sensory regions were either sectioned and studied with light or electron microscopy, or prepared and studied with the surface specimen technique. A change, which can be related to aging, is the accumulation of lipofuscin inclusions in sensory and supporting cells, especially pronounced in the type I sensory cell. Changes of the hair bundles, such as disarrangement of cilia, increased fragility of cilia and formation of giant cilia, have also been observed in aged individuals. In three cases there was a history of vestibular disturbance of vertigo. All three cases had shown caloric hypo-reactivity. In two cases, one with a history of herpes zoster oticus and another with a brain stem glioma, no morphological changes which could be attributed to the diseases, were found. The third case showed degeneration of macula utriculi and the lateral and superior cristae, possibly as a result of vascular disturbance.

Adolescent↗
PubMedDate not supplied

Convergence of ampullar and macular inputs on vestibular nuclei unit of the rat.

181 vestibular nucleus neurons were examined for their responsiveness to rotation about the vertical axis and static tilts in roll and pitch planes in the rat. 68 of these units were sensitive to rotation and tilts (canal-otolith cells). In other words, 41.0% of the neurons responded to rotation (68/166). There was no significant difference in percentage of canal-otolith cells in type I and II neurons, which were 48.6% and 37.0% respectively. Vertical axis rotation when the head was tilted produced a simultaneous stimulation of the canal and otoliths. Using this stimulus method, the bias effect was observed in 72.5% of the canal-otolith cells (29/40). Furthermore, since vertical axis rotation with the head tilted elicited vertical canal responses, the rate of ampullary convergence was estimated by analysing response profiles obtained such rotations. The results obtained in the rat were compared with those in other species.

Animals↗
PubMedDate not supplied

Labyrinthine and somatosensory convergence upon vestibulo-ocular units.

The vestibular nuclei were investigated in 18 adult cats. Vestibulo-oculo-motor neurons were identified by antidromic stimulation of the ascending medial longitudinal fasciculus (MLF). The neurons were subjected to various stimuli: vestibular, neck, forelimb and hindlimb nerve stimulation on both sides. The recording was extracellular with micropipettes containing Fast Green. Only the medial and the superior vestibular nuclei were found to project to the MLF. All projecting units had input from the labyrinths. Excitatory response latencies to ipsilateral labyrinth stimulation never exceeded 3 msec. Both excitatory and inhibitory response latencies could be distributed into different categories. The majority of the neurons did not receive a somatosensory input, and surprisingly few convergent units could be seen. Peripheral somatosensory information apparently plays a minor role in vestibulo-ocular relations.

Afferent Pathways↗
PubMedDate not supplied

Dynamic range of the frequency response of the horizontal vestibulo-ocular reflex of the alert rhesus monkey.

The vestibulo-ocular reflex (VOR) of the alert rhesus monkey was studied using rotational acceleration in the horizontal plane. Both sinusoidal and pseudorandom binary sequence (PRBS) stimuli were used to perform parameters. Results from sinusoidal studies over the frequency range 0.01 to 1.28 Hz, with stimulus amplitudes ranging from 16 to 256 degrees/second were consistent with a linear model of the VOR. Results PRBS stimuli whose bandwidths extended from 0.008 to 0.45 Hz with amplitudes of 4 to 256 degrees corroborated the sinusoidal results. Sinusoidal data obtained at high rotational frequencies indicated that a peak VOR gain occurred at approximately 4 Hz. Close agreement between sinusoidal and PRBS data suggested that the rhesus VOR does not manifest the predictive behavior reported in studies of smooth pursuit eye movements.

Acceleration↗
PubMed1984

An approach to quantify central vestibular compensation.

Central vestibular compensation is the ultimate goal for the dizzy patient. Monitoring spontaneous nystagmus and caloric responses are not usually correlated with the patient progress and cannot be objectively documented. On the other hand, Temporal Asymmetry Shift (TAS) is a more accurate and objective measure of central vestibular compensation. Furthermore, its dynamic pattern offers a reliable indicator to differentiate between peripheral and central vestibular dysfunctions.

Adult↗
PubMed1984

Vestibulo-spinal control differs in patients with reduced versus distorted vestibular function.

Abnormal vestibular function disrupts a subject's reference to gravity (earth) vertical, and prevents resolution of conflicting or inaccurate visual and somatosensory spatial references. However, errors which patients make when attempting to resolve conflicting visual and somatosensory orientation inputs during upright stance differed markedly in patients with (1) symmetric or asymmetric reduced vestibular function, (2) benign paroxysmal positional nystagmus and vertigo, and (3) a combination of distorted and reduced function. Objective characterization of spatial orientation systems and compensatory strategies under altered sensory conditions is an essential first step toward identifying optimal treatment methods for each of these three types of vestibular deficient patients.

Humans↗
PubMedDate not supplied

Intrabeat relationship of postrotatory nystagmus in patients with neurological disorders.

The intrabeat relationships between velocity, amplitude and duration of the slow phase of nystagmus as well as between amplitudes of slow vs. fast phase of nystagmus were analysed during a postrotatory nystagmus response by using linear regression analysis. Three groups of patients were studied, each consisting of 10 subjects with lesions either in the peripheral vestibular system, in the frontal lobe, or in the brain stem. Irrespective of the site of the lesion, all groups exhibited the same response pattern: a reduction in amplitude control of the end-point of nystagmus and an increase in durational control. The most prominent changes were observed in patients with brain-stem lesion in whom the durational control of the slow phase of nystagmus was constant, with a mean slow phase duration of 150 to 250 ms in the case of 3 to 4 fast phases per second. No alterations were observed in the relationship between amplitude of slow vis-à-vis fast phase. The results indicate that analysis of intrabeat relationship may provide additional data on the side of the disorder affecting the vestibular system.

Adult↗
PubMed1989

Reduction of the time constant in the VOR as a protective mechanism in acute vestibular lesions.

Fourteen patients with vestibular neuritis were examined at onset of symptoms and after one year. Postrotatory time constant and gain in the vestibulo-ocular reflex (VOR) were measured after rotation with a velocity step of 150 deg/s. There was no significant difference in gain towards the healthy side at onset of the disease compared to recordings after one year. The time constant towards the healthy side was significantly shorter at onset compared to measurements after one year. The results reflect the loss of unilateral vestibular function on the velocity storage mechanism, both in the acute situation and after compensation. The findings indicate that reduction of the time constant in the VOR is not only due to unilaterally vestibular impairment but it is also an effect of the generally reduced activity in the vestibular system after a lesion and may act as protective mechanism in acute vertigo.

Acute Disease↗
PubMed1993

Bilateral vestibular neuronitis.

Bilateral vestibular neuronitis with a different onset time for each affected side was reported in two cases among 74 cases observed. The first case appeared 3 weeks and the other 5 years before involvement of the second ear. In the case with a short period before the second attack, the direction of nystagmus was unchanged throughout the clinical course. It is suggested that the direction of nystagmus depends upon the severity of each vestibular dysfunction. In the case with a long period when the vestibular compensation has been completed, paralytic nystagmus was observed and its direction corresponded with the side affected by canal.

Adolescent↗
PubMed1993

Effect of transdermally administered scopolamine on the vestibular system in humans.

In order to elucidate the effect of scopolamine on the vestibular system in humans, various experimentally-induced forms of nystagmus, i.e. caloric nystagmus, rotational nystagmus, optokinetic nystagmus, visual-vestibular interaction and optokinetic after nystagmus, were evaluated before and after the administration of two pieces of Scopoderm-TTS or placebo patches retro-auricularly. Scopolamine reduced the responses of both the caloric and optokinetic after nystagmus compared with the placebo. The possible action site of this drug is discussed.

Administration, Cutaneous↗
PubMed1993

Body sway response to experimental unbalance in normal subjects and patients with unilateral vestibular disorders.

The function of maintaining posture during temporary unbalance caused by experimental vestibular asymmetry was studied. Galvanic stimulation to the vestibular nerve causing body deviation to the stimulated ear was given to 31 normal subjects and 16 patients with peripheral vestibular disorders. The velocity of spontaneous body sway and that during body deviation caused by the galvanic stimulation were compared. The spontaneous body sway velocity was significantly higher than that of normal subjects. In normal subjects, the body sway velocity during body deviation remarkably increased, while that in patients did not. It is considered that large body sway in patients might conceal the fine compensatory body sway during the body deviation and that patients with unilateral vestibular dysfunction who have large body sway are always in a dysfunction state similar to that which normal subjects experience during body deviation caused by galvanic stimulation.

Dominance, Cerebral↗
PubMed1993

The contribution of proprioception to posture control in normal subjects.

In order to investigate the contribution of proprioceptive input to maintaining an upright position, stabilometry via 100-Hz vibratory stimulation applied to the Achilles tendon was studied and analyzed with respect to area, length and power spectra according to the method of fast Fourier transform (FFT). Twenty-one young medical students were analyzed in this study. When vibration was applied, the body sway was significantly greater than that of control in area and length with both eyes open and closed. There was a significant increase of total power in both the lateral (X) and antero-posterior (Y) directions with the eyes closed. With the eyes open, an increase was found only in the antero-posterior direction. The frequency band indicating the maximum spectrum did not shift. Significant increases in power spectra were found in the frequency range of more than 2 Hz in both two directions with the eyes closed. It was concluded that a vibration given to the Achilles tendon provoked a pronounced high frequency body sway especially in the antero-posterior direction when visual information was nullified, and that proprioceptive information may have a minor role compared with visual information.

Achilles Tendon↗
PubMed1993

Contribution of vision to the stabilization of body sway in patients with spinocerebellar degeneration.

Body sway was recorded with closed eyes, open eyes and visual feedback for 30 s each. Thirteen patients with spinocerebellar degeneration and 17 age-matched normal controls underwent the examination. Four parameters (area, length, sums of frequency spectrum in the anterior-posterior and lateral directions) were computed. Furthermore, Romberg ratios between closed and open eye conditions [Romberg c/o] and Romberg ratios between closed eyes and visual feedback conditions [Romberg c/f] were computed. Four parameters were significantly greater in the patients with spinocerebellar degeneration than in the normal controls. However, three of eight Romberg ratios were significantly greater in the patients with spinocerebellar degeneration than in the normal controls. The results implied that the proprioceptive-posture loop was mainly disordered while the visuo-postural loop was intact in patients with spinocerebellar degeneration.

Cerebellum↗
PubMed1995

Infralabyrinthine approach to vestibular neurectomy in Menière's disease.

The infralabyrinthine approach to vestibular neurectomy was performed in 9 patients with unilateral Menière's disease. According to the AAOO (1972) criteria, 7 of 9 cases were graded as class B and the remaining 2 cases as class C. Otherwise, according to the AAO-HNS (1985) criteria, 6 patients who could be followed over 2 years were all graded as 'complete' at the vertigo control. The compensation of the spontaneous vestibular signs was rapid in the first 2 postoperative weeks, though an occasional imbalance on movement persisted even 3 years after the operation. No specific caloric reaction was elicited in any patient after warm or cold water irrigation of the operated side in any postoperative period. There have been no serious complications except a delayed facial palsy that appeared in one case one week after surgery. This approach offers access to the vestibular nerve with minimal risk and morbidity.

Adult↗
PubMed1995

Discrimination of patients with acoustic neuroma and peripheral vestibular lesions with human posture dynamics.

A group of normal subjects (n = 17) was compared with groups of patients with a diagnosis of vestibular neuritis (n = 18), and acoustic neuromas (n = 35). Fisher linear discriminant analysis was applied to distinguish clusters of parameters characteristic for each disease. Hence it was possible to distinguish the vestibular neuritis patients from the normal group with statistical significance (p < 0.01). Also the patients with an acoustic neuroma could be distinguished from the normal subjects with statistical significance (p < 0.05).

Diagnosis, Differential↗