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At least 1,153 records · Page 64Linked to original sources
PubMed1995

New diagnostic tests for the function of utricles, saccules and somatic graviceptors.

Clinical tests that allow us to discriminate between utricular, saccular and somatic effects on gravity perception and control are desirable but wanting. A new test battery is presented which combines four experimental paradigms based on the subjective horizontal body position (SHP), namely, a test on a tiltable board and on a sled centrifuge under varied leg position, with two paradigms based on the subjective visual vertical (SVV). It is shown by a combination of experiments and deductions, that, why, and how these tests can separate the effects of otoliths from those of somatic graviceptors, the effects of the utricles from those of the saccules, and the effects of the constituents of the somatic graviception from each other. The present study demonstrates the capabilities of the tests as well as their limitations.

Animals↗
PubMed1995

Dose-related effects of alcohol on dynamic posturography and oculomotor measures.

Four healthy male volunteers < 30 years of age participated in a blinded study of placebo versus low (0.45 g/kg lean body weight = LBW), medium (0.80 g/kg LBW) and high (1.05 g/kg LBW) dose ethanol ingestion to investigate its effect upon gaze and posture control. Serial electronystagmography and computerized platform posturography were performed at different points along each subject's blood alcohol concentration (BAC) curve as measured by breath analysis. Smooth pursuit and positional testing revealed subtle abnormalities at sub-intoxicating BACs. In addition, instability on posturography was evident on the Sensory Organization Test with no statistically significant influence observed on muscle latency testing as determined by sway analysis. We conclude that even low ethanol BAC levels produce widespread gaze and posture control effects which can be easily documented.

Adult↗
PubMed1995

Nystagmus in benign paroxysmal positional vertigo: a three-component analysis.

Three-component analysis of nystagmus was carried out in 10 patients with benign paroxysmal positional vertigo (BPPV), focusing on the horizontal, vertical and torsional components, with the aid of a computerized eye movement analysis system. Using a pendular rotation stimulus we also measured three eye components of eye movement evoked from the vertical semicircular canals in 3 normal subject; two components (vertical and torsional) of nystagmus in patients with BPPV were compared with that of eye movements derived from the vertical semicircular canals. The time course of slow phase velocity of three components in BPPV patients was similar. In BPPV, the torsional component of eye movements was larger than that of the vertical component without obvious horizontal eye deviation. On the other hand, the vertical component from vertical semicircular canals was larger than that of the torsional component. From the view point of the vestibulo-ocular reflex, it is difficult to support the idea that the pathology of BPPV is localized only to the posterior semicircular canal.

Electronystagmography↗
PubMed1995

Postural control and vestibular function in patients selected for cochlear implantation.

Postural control and vestibular and eye motor function were evaluated in 7 postlingually deaf patients before cochlear implantation as vibration toward the calf muscles or galvanic electrical stimulation of the vestibular nerves perturbed stance. The patients were compared with 21 control subjects. Vibration-induced bodysway was increased in the patients compared to the normals. Galvanic stimulation induced a bodysway that was not significantly different from that of the control group suggesting that the patients selected for cochlear implantation, and with otherwise reduced postural control, are sensitive to electrical stimulation of the vestibular nerve. This finding may contribute with a complementary hypothesis to the causes of dizziness among cochlear implant patients.

Adult↗
PubMed1995

The effect of roll-tilt on ocular skew deviation.

Static roll-tilt of normal healthy subjects causes the ocular tilt reaction (OTR) one component of which is disconjugate vertical eye position (skew deviation). In this study the magnitude of skew was measured subjectively by the use of a computerized Hess test at three static roll-tilt angles (head erect, left ear down and right ear down) and two viewing distances (20 cm and 60 cm). The results showed that during static roll-tilt there was a small skew deviation, the magnitude of which was increased at close viewing distances.

Afferent Pathways↗
PubMed1995

Observation of positional nystagmus with infrared CCD camera.

Using infrared CCD camera and electronystagmography we analyzed positional nystagmus in 33 patients with peripheral positional vertigo. Patients were classified into three types; (a) lateral type: nystagmus occurs in lateral position, (b) sagittal type: nystagmus occurs in head-hanging position (so-called benign paroxysmal positional vertigo, BPPV), and (c) mixed type. Nystagmus in the lateral type was horizontal and that in the sagittal type was rotatory. In all types, the vertigo and nystagmus began with a few seconds' latency after head tilt and briefly increased to a maximum, and then gradually decreased. The duration of horizontal nystagmus in the lateral and mixed type was significantly longer than that of rotatory nystagmus in the sagittal type mixed type. The mean value of the former was 90.6 s and that of the latter 18.1 s. We suggest that the velocity storage mechanism of the horizontal vestibulo-ocular reflex (VOR) is considerably different from that in the vertical VOR.

Adolescent↗
PubMed1995

Three-dimensional (3-D) eye movement analysis in patients with positioning nystagmus.

Benign paroxysmal positioning vertigo (BPPV), and nystagmus (BPPN) is the commonest type of rotational vertigo. Typical BPPN is generally believed to arise from one posterior semicircular canal. If this is true, the syndrome would offer the unique possibility to study vestibular responses when just one single semicircular canal is excited. In this study we used search coils to measure 3-D eye positions in 3 patients with BPPN. We present a complete 3-D description of the eye movements induced in BPPN. We found that in our patients the eyes rotate rather precisely in the plane of one posterior semicircular canal, suggesting that BPPN in our cases is indeed solely produced by the posterior semicircular canal.

Adult↗
PubMed1995

Posturography: head stabilisation compared with platform recording. Application in vestibular disorders.

Posturography with simultaneous recording of the head movements (H-recording) and of the pressure of the feet on the platform (P-recording) has been applied in patients with peripheral vestibular disorders. For the whole testing (four tests with visual and proprioceptive interaction) 40% showed an identical degree of abnormality for the measurements of surface in P- and H-recording. In a large majority of the patients, showing a difference between H- and P-recording, this difference indicated a lower degree for the H-recording. Concerning the four tests separately, the differences for eyes closed tests were more frequently positive (larger surface for head movements) than for eyes open tests. Also on foam rubber there was more difference than on stable platform. Especially the test with eyes closed on foam rubber showed more differences. These data show that in a minority of patients the comparison of H-recording and P-recording affords complementary information showing in these cases some independence of head stabilisation and foot-stabilisation. Head-recording can be used as a posturographic technique but one has to keep in mind the possible differences with platform-recording.

Functional Laterality↗
PubMed1995

Vestibular stimulation perturbs human stance also at higher frequencies.

The effect of primary vestibular disturbance on postural control was investigated in 11 normal subjects exposed to perturbation by bi-polar binaural galvanic stimulation of the vestibular nerve. The stimulus consisted of 30 s of sinusoidal galvanic stimulation at frequencies of 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0 Hz, with a current of +/- 1 mA, the subject standing with open or closed eyes and the response evoked being recorded with a force platform. As compared with resting values, i.e. no stimuli, variance of lateral body sway was significantly greater at all frequencies tested in the closed eyes condition and at frequencies of 0.2, 0.5, 1.0, 3.0 and 4.0 Hz in the open eyes condition; using a high pass filter with a cut-off frequency of 0.1 Hz, variance of lateral body sway was significantly greater at frequencies 0.2, 0.3, 0.5, 1.0 and 2.0 Hz in the closed eyes condition and at frequencies 0.5 and 2.0 Hz in the open eyes condition. These findings suggest that in the lateral plane vestibular input affects and probably contributes to human postural control over a wider frequency range than suggested by findings in previous studies. Moreover, the visual contribution appears to enable the subject to suppress vestibular input causing lateral body sway only in the lower frequency range (here at 0.2 and 0.3 Hz). This evidence of vestibular contribution to postural control in the lateral plane is consistent with the response characteristics of the vestibulo-ocular reflex.

Adolescent↗
PubMed1995

Randomized perturbed posturography in abstinent chronic alcoholics.

Equilibrium is maintained by visual, proprioceptive and vestibular afferent influx, central coordination and motor efferents. Eleven male abstinent chronic alcoholic volunteers aged 44-65 years (mean 57 years) were investigated by randomized perturbed posturography. They had all been long time heavy drinkers. Ocular smooth pursuit and visual suppression of the vestibulo-ocular reflex showed abnormalities in a previous study, but they had no signs or symptoms of polyneuropathy. The current study demonstrated larger (but generally not significantly so) sway areas, and in all tests on the randomly moving support surface the sway velocities were significantly larger than in the controls. It is concluded that randomized perturbed posturography is valuable in dysequilibrium assessment in chronic alcoholics.

Adult↗
PubMed1995

Vestibular plasticity following orbital spaceflight: recovery from postflight postural instability.

Results of previous studies suggested that the vestibular mediated postural instability observed in astronauts upon return to earth from orbital spaceflight may be exacerbated by an increased weighting of visual inputs for spatial orientation and control of movement. This study was performed to better understand the roles of visual and somatosensory contributions to recovery of normal sensori-motor postural control in returning astronauts. Preflight and postflight, 23 astronaut volunteers were presented randomly with three trials of six sensory organization test (SOT) conditions in the EquiTest system test battery. Sagittal plane center-of-gravity (COG) excursions computed from ground reaction forces were significantly higher on landing day than preflight for those test conditions presenting sway-referenced visual and/or somatosensory orientation cues. The ratio of summed peak-to-peak COG sway amplitudes on the two sway-referenced vision tests (SOTs 3 + 6) compared to the two eyes closed tests (SOTs 2 + 5) was increased on landing day, indicating an increased reliance on visual orientation cues for postural control. The ratio of peak-to-peak COG excursions on sway-referenced surfaces (SOTs 4, 5 & 6) to an earth fixed support surfaces (SOTs 1, 2 & 3) increased even more after landing suggesting primary reliance on somatosensory orientation cues for recovery of postflight postural stability. Readaptation to sway-referenced support surfaces took longer than readaptation to sway-referenced vision. The increased reliance on visual and somatosensory inputs disappeared in all astronauts 4-8 days following return to earth.

Astronauts↗
PubMed1996

The subjective horizontal in eccentric rotation influenced by peripheral vestibular lesion.

Peripheral vestibular equilibrium disorders may originate in various parts of the labyrinth or the vestibular nerve. Traditionally, the function of the lateral semicircular canals has been assessed with caloric irrigation, and sometimes falsely been interpreted as a vestibular nerve lesion. The vertical semicircular canals are not easily assessed. Caloric testing with the head in different positions is not very helpful, but the canals may pairwise be tested using specific rotational techniques. Often the otolithic organs, capable of detecting linear acceleration forces, are forgotten as a source of vertigo and dizziness. We have implemented horizontal rotatory testing with the subject seated eccentrically facing the direction of rotation as a means of assessing otolithic function. The subject experiences a lateral tilt and is instructed in darkness to put a short light bar in the position he thinks a water surface would have, which is identical to his perceived tilt. In 39 normal subjects, a theoretical tilt of 24 degrees was estimated as approximately 19.5 degrees, and the standard deviation was 6 degrees. A side difference index was proposed to be normal if below 25%. The preliminary findings in a few patients with known labyrinthine lesions are presented. We propose that otolithic as well as lateral semicircular canal functions are useful to monitor in patients with suspected peripheral equilibrium disorders.

Adult↗
PubMed1997

Active posture control during experimental motion sickness in guinea-pigs.

This study evaluated active posture control in guinea-pigs under motion sickness stimulation. Twelve guinea-pigs, which received training to stay on a moving perch, were divided into two groups: a motion sickness stimulation group and a control group. The motion sickness group was given a combined stimulation of turntable rotation and optokinetic drum rotation, and the control group was given turntable stimulation alone. Motion sickness was evaluated by conditioned taste aversion to saccharin solution. Active posture control was evaluated by the angle of nose tip displacement and the staying duration (length of time that guinea-pigs stayed on the turntable). The consumption of saccharin solution increased in the control group but did not increase in the motion sickness group. The motion sickness group showed a significant increase in the mean angle of nose tip displacement and a significant decrease in the staying duration on the turntable. These results indicate that active posture control was disturbed by motion sickness stimulation.

Animals↗
PubMed1997

Postural stability, neck proprioception and tension neck.

We examined whether tension neck (TN) may due to inadequate proprioceptive and vestibular activation of the cervico-collic reflex (CCR). CCR and vestibulospinal responses (VSRs) were recorded from 106 forest workers by stimulating the neck, lumbar or calf proprioceptors by vibration. The VSRs were recorded with posturography. TN occurred in 27 out of 106 subjects. The subjects with TN (48.5 years) were older than those without TN (43.1). The mean body sway during quiet stance was the same in both groups during the neck stimulation. In subjects with tension neck stimulation of neck or lumbar proprioceptors caused excessive, unpredictable body excursion in the lateral and anteroposterior direction that continued after stimulation. Results from stimulation of lower limb proprioceptors did not significantly differ between the 2 groups. In logistic regression analysis a model to predict TN consisting of perstimulatory postural stability (odds ratio 1.4) and poststimulatory postural stability (odds ratio 1.8) turned out to be statistically significant. The anatomical findings of CCR in the medulla oblongata suggest that neck muscle afferents control the posture and muscle activity of the neck. The erroneus facilitation of proprioception in TN subjects indicate that TN may be raised by inadequate facilitation of CCR.

Adult↗
PubMed1997

Stability limits for visual feedback posturography in vestibular rehabilitation.

Vestibular rehabilitation therapy (VRT) is used to enhance compensation after peripheral vestibular lesion. In visual feedback posturography (VFP) a patient can practice postural control actively on a force platform and progress in the VRT can be objectively measured. The aim of the study was to determine normative values for stability limits (SL) in the VFP. Eleven healthy subjects were measured with force platform in visual feedback condition. Subjects were instructed to move their center of gravity (COG) marker to given targets, which were displayed on a computer screen in front of them. Target distance from the center of the platform was increased step by step to determine the SL in 8 directions. Hit delays (HD) to the targets and hold percentages (HP) within the targets were measured to quantify the difficulty of the individual targets as a function of subject's shoe size. With fixed feet position the SL in anterior direction increased 1.2 times the absolute increase in shoe length. An almost similar increase was found in anterolateral direction. The knowledge of the mechanical SL is important, because targets near SL should be avoided for safety reasons.

Adult↗
PubMed1998

Postural modulation of the segmental reflex: effect of body tilt and postural sway.

This purpose of this study was to clarify the relationship between segmental reflex excitability and posture and to investigate potential mechanisms responsible for modulation of the H-reflex (HR) in unsupported standing. Soleus (S) and lateral gastrocnemius (LG) HRs were recorded from subjects (N=12S, N=11LG) while their static posture was altered from supine to vertical (5 positions). This was compared to an unsupported standing position in which the subjects naturally underwent a small degree of postural sway, a dynamic posture condition. Although individual profiles suggested varied relationships between the S and LGHR and the angle of body tilt, the group data did not reveal significant differences. There was, however, a significant (p < .01) decrease in the S (43% 49%) and LG (34%-46%) HR when subjects stood without support compared to all static postures. This decrease occurred even though the tonic or background activity of the S and LG was present only when subjects were free standing. To determine whether weight-bearing was responsible for the HR depression, 3 additional conditions were compared (N=3), supported standing without weight-bearing (90 degrees NWB), supported standing with weight-bearing (90 degrees WB), and free standing. Again, S and LGHRs were depressed only when subjects were free standing. Presynaptic inhibition presumably accounts for the depression of the HR in unsupported standing. Data from 8 of the subjects were collected under the same 6 conditions using a shorter interstimulus interval (1 Hz stimulus instead of 0.1 Hz) which produced low frequency depression (LFD) of the S and LG HR. LFD reduced the amplitude of the S HR an average of 43% (p < .05) when subjects were in a supported static position but only 21% when subjects were free standing. Although tonic activity of the S was present only when subjects were free standing, in 2 (of 8) individuals the EMG in free standing was not measurably different from static conditions. In these individuals, free standing still depressed the SHR by 35%; however, the shorter stimulus interval now produced the same degree of LFD when subjects were free standing (35%) as when they were standing with support (37%). The data suggest that 2 presynaptic mechanisms, although independent, interact to control spindle afferent feedback when subjects are free standing. Postural sway appears to be necessary to reduce the gain of the HR when subjects are standing, whereas, LFD is influenced by the degree of muscle activation.

Adolescent↗
PubMedDate not supplied

Stability of the human body investigated by sway magnetometry.

A new technique using a pre-calibrated magnetometer has been used to investigate the stability of the human body. Transducer coils were attached to a belt which was worn by the subject. Sway was measured over 30 s periods with eyes open and eyes closed. For 10 normal subjects, the mean sway speed was 3.6 +/- 0.9 mm/s with eyes open, and 5.3 +/- 1.5 mm/s with eyes closed. The mean ratio for eyes open to eyes closed was 0.68 +/- 0.10. The test was simple to perform and gave reproducible results.

Adult↗