3D body segment oscillation and gait analysis for vestibular disorders

Objective

To investigate the patterns of gait and locomotion in three dimension space in patients with vestibular disorders.

Methods

A 3D motion analysis system was employed to evaluate locomotor pattern and body's oscillation during gait under different conditions (normal, slow, fast speeds walking with eye open and normal speed walking with eyes closed) of nine patients with vestibular disorders. Twenty-one markers placed on the subject to record kinematics and locomotions of the head, spine and pelvis segments while walking. For each locomotor trial, the walking speed, locomotor patterns as well as the absolute angular dispersions of six segments around the roll, pitch and yaw axes were calculated to assess the equilibrium strategies of head, trunk and pelvis. Data was also recorded in 10 healthy subjects as control.

Results

Patients’ cadence is faster, and the stride time at normal walking speed is shorter than that of the controls (p < 0.05). The body sway has also been documented some impairment in patients. With respect to the control, patients’ oscillation of trunk around yaw axis at fast speed is less (p < 0.05), which means the patient seems need less shoulder torsional movement. Moreover, the most prominent changes in patients are the sway of hip in roll, which is significant less than controls at fast (p < 0.01), slow speed (p < 0.01) and in eye-closed condition (p < 0.05).

Conclusion

Our investigation corroborates those reports that higher velocities would be helpful for the increased gait stability in patients with vestibular disorders. And the body always try to keep the stability of head during gait, even under vestibular deficit conditions.     

Effects of using cane and vestibular rehabilitation on the walking function in elderly patients with dizziness

ObjectiveAdults over the age of 65 years with balance disorders are at about twice the risk of falls, compared with those without balance disorders. Falls contribute to about 74% of the proximal femoral fractures commonly seen in the elderly. Since balance disorders are more prevalent in older adults than in younger adults, it is important to deal with balance disorders in older adults to prevent falls and the resulting deterioration in their ADL (activity of daily living). In this study, we investigated the effects of vestibular rehabilitation (VR) and cane use on improving gait and balance in patients aged over 65 years with balance disorder.Methods: Patients aged over 65 years presenting to the Department of Otolaryngology at St. Marianna University School of Medicine between July 1 and November 1, 2018, with symptoms of dizziness for ≥ 3 months and a Japanese translation of the Dizziness Handicap Inventory score of ≥ 26 were included in the study. We quantitatively analyzed their gait before and after VR, and with and without the use of a cane.ResultsA total of 21 patients participated in the study (14 women; mean age 73.9 ± 6.9 years). Before VR, using a cane made no difference to step length or walking speed. After VR, using a cane increased step length from 50.5 cm (95% confidence interval [CI], 47.4–53.7 cm) to 52.0 cm (95% CI, 48.9–55.1 cm) (p = 0.039). There was no change in walking speed. A comparison of walking assessment results while using a cane before and after VR showed that step length increased from 49.9 cm (95% CI, 46.6–53.2 cm) to 52.0 cm (95% CI, 48.9–55.1 cm) (p = 0.005), and walking speed increased from 90.5 cm/s (95% CI, 82.7–98.4 cm/s) to 96.1 cm/s (95% CI, 88.3–103.9 cm/s) (p = 0.005).ConclusionsWalking speed and step length with the use of a cane significantly improved following VR. VR and cane use may act synergistically to improve walking.     

Improvements in trunk sway observed for stance and gait tasks during recovery from an acute unilateral peripheral vestibular deficit

OBJECTIVES: Our aim was to track improvements in postural control during recovery from an acute unilateral peripheral vestibular deficit (UVL), presumably due to vestibular neuritis, and to determine if recovery rates were different for stance and gait tasks. Postural control was quantified using simple measurements of trunk sway: amplitudes of trunk sway angle and angular velocity, in the roll and pitch directions as well as task duration, were examined for a battery of stance and gait tasks. These measures were collected at the onset of the deficit and then 3 weeks and 3 months later. STUDY DESIGN: A repeated-measures design was used for UVL subjects and age-matched healthy controls. Stance tasks involved standing on 1 or 2 legs with eyes open or closed. Gait tasks consisted of tandem gait, walking normally with eyes closed, or with the head rotating or head pitching, walking up and down stairs and walking over a series of low barriers. Stance and tandem gait tasks were repeated using a foam support surface instead of a normal floor. PATIENTS: Twenty-eight patients with acute UVL were examined. MAIN OUTCOME MEASURES: The range of trunk sway angular displacement and angular velocity in the pitch and roll directions was measured for each task in addition to task duration. The measures were compared with those of normal subjects. RESULTS: The amplitudes of pitch trunk sway for 2-legged stance tasks with eyes closed underwent the greatest reduction 3 weeks after UVL onset. At 3 months, trunk sway was almost normal for all 2-legged stance tasks. One-legged stance tasks with eyes open showed a similar but slower improvement. Stance time without a fall showed a very rapid improvement for 1-legged tasks but was still shorter than that of normal subjects at 3 months. Trunk sway for the simple gait tasks was within normal range at 3 months; however, task duration was still longer than normal. More complex gait tasks, such as walking 8 tandem steps on foam or walking up and down stairs, showed no improvement in trunk roll sway at 3 months. A mix of variables from mainly gait tasks best identified a balance deficit due to UVL, with complex gait tasks becoming more important for identification purposes as compensation progressed. The accuracy of UVL identification with durations alone was 75% of the accuracy with combined trunk sway and duration measures. CONCLUSIONS: These data suggest that recovery of normal trunk control during the compensation process for unilateral vestibular hypofunction is more rapid for stance tasks than gait tasks. Even at 3 months, trunk sway for complex gait tasks was not normal. Thus, trunk sway for gait tasks provides a better insight into remaining deficits in balance control of vestibular-loss patients than the sway of stance tasks.     

Laryngopharyngeal reflux disease in the Greek general population,prevalence and risk factors

Gait function may be impaired in patients with vestibular disorders, making gait assessment in the clinical setting relevant for this patient population. The purpose of this study was to evaluate the discriminant validity of a gait assessment protocol between patients with vestibular disorders and healthy participants. Furthermore, test re-test reproducibility and the measurement error of gait performance measures in patients with vestibular lesions was performed under different walking conditions. Gait parameters of thirty-five patients with vestibular disorders and twenty-seven healthy controls were assessed twice with the GAITRite® system. Discriminant validity, reproducibility (intra class correlation [ICC]) and the measurement error (standard error of measurement [SEM], smallest detectable change [SDC]) were determined for gait speed, cadence and step length. Bland-Altman plots were made to assess systematic bias between tests. A significant effect of grouping on gait performance indicates discriminant validity of gait assessment. All tests revealed differences between patients and healthy controls (p < 0.01). The ICCs for test re-test reproducibility were excellent (0.70-0.96) and measurement error showed acceptable SDC values for gait parameters derived from three walking conditions (9-19 %). Bland-Altman plots indicated no systematic bias. Good validity and reproducibility of GAITRite® system measurements suggest that this system could facilitate the study of gait in patients with vestibular disorders in clinical settings. The SDC values for gait are generally small enough to detect changes after a rehabilitation program for patients with vestibular disorders.     

The role of the labyrinth, proprioception and plantar mechanosensors in the maintenance of an upright posture

The maintenance of an upright posture in man requires information from vision, the labyrinth, proprioception and plantar mechanosensors. In order to evaluate the role of the labyrinth, proprioception and plantar mechanosensors, stabilometry was performed in subjects with closed eyes. Ten patients with bilateral severe or complete labyrinthine paresis were studied, as well as 9 patients with severe proprioceptive disorders and 10 normal healthy persons whose plantar mechanosensors were anesthetized by hypothermia. Both the area of sway and the total locus length (accumulated shift distance length) were evaluated. On closing eyes, in patients with labyrinthine disorders demonstrated that the area of sway increased more than length. On the other hand, in patients with proprioceptive disorders, length increased more than the area. In plantar anesthetized subjects, similar to the labyrinthine disorder cases, the area of sway increased more than length. These findings suggest that the labyrinth is a main monitor of the area of body sway, while proprioception is a principle monitor of the velocity of body movement of sway (or locus length). The plantar mechanosensor monitors the area of body sway similar to the labyrinth, but works less than the labyrinth. The locus length is the distance per minute and reflects the velocity of body sway. Thus, the length per area is a parameter for the velocity of body sway per area. Since proprioceptive disorders increase both the locus length and the length per area, present findings suggest that if proprioception is damaged, the body begins to move faster. Compensated labyrinthine disorders have a tendency to increase the length per area, indicating that if a labyrinthine disorder is compensated, the body adapts and moves faster to maintain an upright posture.     

The role of the labyrinth,proprioception and plantar mechanosensors in the maintenance of an upright posture

The maintenance of an upright posture in man requires information from vision, the labyrinth, proprioception and plantar mechanosensors. In order to evaluate the role of the labyrinth, proprioception and plantar mechanosensors, stabilometry was performed in subjects with closed eyes. Ten patients with bilateral severe or complete labyrinthine paresis were studied, as well as 9 patients with severe proprioceptive disorders and 10 normal healthy persons whose plantar mechanosensors were anesthetized by hypothermia. Both the area of sway and the total locus length (accumulated shift distance length) were evaluated. On closing eyes, in patients with labyrinthine disorders demonstrated that the area of sway increased more than length. On the other hand, in patients with proprioceptive disorders, length increased more than the area. In plantar anesthetized subjects, similar to the labyrinthine disorder cases, the area of sway increased more than length. These findings suggest that the labyrinth is a main monitor of the area of body sway, while proprioception is a principle monitor of the velocity of body movement of sway (or locus length). The plantar mechanosensor monitors the area of body sway similar to the labyrinth, but works less than the labyrinth. The locus length is the distance per minute and reflects the velocity of body sway. Thus, the length per area is a parameter for the velocity of body sway per area. Since proprioceptive disorders increase both the locus length and the length per area, present findings suggest that if proprioception is damaged, the body begins to move faster. Compensated labyrinthine disorders have a tendency to increase the length per area, indicating that if a labyrinthine disorder is compensated, the body adapts and moves faster to maintain an upright posture.     

The diagnosis of central vestibular disorders based on the complementary examination of the vestibulospinal reflex

Objectives:Stance and gait unsteadiness along with vertigo contribute to a central vestibular disorder.For objective analysis ultrasound-computer-craniocorpography(US-COMP-CCG)can be used.Aim of the study was to characterize the unsteadiness in central vestibular disorders and discuss the possible diagnostic usage of US-COMP-CCG.Methods and results:Hundred-and-ninety patients(70 male and 120 female,mean age±SD,58.94±15.27)suffering from central vestibular disorder and 230 healthy control patients(78 male and 152 female,mean age±SD,50.94±15.27)were enrolled.Stance and gait analysis was according to vestibulospinal tests of US-COMPCCG.IBM SPSS V24 software was used for statistical analysis.Mann-Whitney U test and Chi-square test were used,along with sensitivity and specificity categorization.The significance level was p<0.05.According to schematic and statistical analysis instability and postural sway were increased in the vertigo population and statistically significant difference was shown.Upon categorical analysis significant correlation was detected[standing test:longitudinal sway(p<0.00001),lateral sway(p<0.00001),forehead covering area parameters(p=0.0001);stepping test:longitudinal deviation(p=0.05),lateral sway(p=0.011)parameters].Conclusions:Clinicians should consider that postural instability is prominently present in this population and might be of a diagnostic importance.     

正常人与眩晕患者姿势图的定量研究

采用人体重心动摇计与计算机联机，测试６８名正常人及８２例中枢与末梢性眩晕患者的姿势图及有关参数，测试结果证明：①人体重心晃动轨迹分为中心型、前后型、左右型、多中心型、弥散型五种图形，正常人中心型多见，中枢性眩晕弥散型多见，末梢性眩晕介于二者之间；②正常人与患者各参数比较，眩晕患者晃动的轨迹长、速度大，与正常人比较差异有极显著性，中枢及末梢性病变组间比较差异无显著性；③正常人不同年龄组各项参数比较，２０岁组平衡功能最佳，重心晃动的面积小、轨迹短、速度慢，与５０岁以上组比较差异有极显著性，证明５０岁以后前庭功能开始衰变。     

Three-dimensional analysis of human locomotion in normal subjects and patients with vestibular deficiency

The purpose of this study was to clarify the role of the vestibular system in human locomotion. The subjects were nine healthy controls, nine patients with unilateral vestibular deficiency (UVD) and nine patients with bilateral vestibular deficiency (BVD). The UVD subjects were Ménière's disease patients who were being treated with administration of gentamicin into the tympanic cavity. BVD subjects were hearing-impaired individuals who showed no response to the ice-water caloric test. A total of 13 markers were attached to the head, trunk (C7), hip and foot in order to measure translational and rotational motions with the aid of a video image processing system. All subjects were instructed to restrict their stride length to approximately 80 cm while walking on a treadmill and watching a visual target. However, walking speed varied depending on the ability of the subject to maintain body equilibrium. The results showed that walking speed and step frequency were significantly lower for the UVD and BVD groups than for the normal group. Analysis of head movements in the sagittal plane showed a counteracting motion between pitch rotations and vertical translation as previously reported. We also found head counteracting motions between yaw rotation and lateral translation in the horizontal plane. These mechanisms are thought to help stabilize the gaze during walking. When the head fixation point was calculated by projecting the naso-occipital axis line during walking, the head counteracting motion was found to assist the vestibulo-ocular reflex in stabilizing the gaze. In addition, normal subjects seemed to use head stabilization as a space strategy in order to minimize head yaw movement. In contrast, UVD and BVD subjects adopted head stabilization as a trunk strategy.     

Three-dimensional Analysis of Human Locomotion in Normal Subjects and Patients with Vestibular Deficiency

The purpose of this study was to clarify the role of the vestibular system in human locomotion. The subjects were nine healthy controls, nine patients with unilateral vestibular deficiency (UVD) and nine patients with bilateral vestibular deficiency (BVD). The UVD subjects were Ménière's disease patients who were being treated with administration of gentamicin into the tympanic cavity. BVD subjects were hearing-impaired individuals who showed no response to the ice-water caloric test. A total of 13 markers were attached to the head, trunk (C7), hip and foot in order to measure translational and rotational motions with the aid of a video image processing system. All subjects were instructed to restrict their stride length to 80 cm while walking on a treadmill and watching a visual target. However, walking speed varied depending on the ability of the subject to maintain body equilibrium. The results showed that walking speed and step frequency were significantly lower for the UVD and BVD groups than for the normal group. Analysis of head movements in the sagittal plane showed a counteracting motion between pitch rotations and vertical translation as previously reported. We also found head counteracting motions between yaw rotation and lateral translation in the horizontal plane. These mechanisms are thought to help stabilize the gaze during walking. When the head fixation point was calculated by projecting the naso-occipital axis line during walking, the head counteracting motion was found to assist the vestibulo-ocular reflex in stabilizing the gaze. In addition, normal subjects seemed to use head stabilization as a space strategy in order to minimize head yaw movement. In contrast, UVD and BVD subjects adopted head stabilization as a trunk strategy.     

Influence of proprioceptive input from leg, thigh, trunk and neck muscles on the equilibrium of standing]

To investigate and compare the roles of proprioceptive input from the leg, thigh, trunk and neck muscles on equilibrium, we performed static posturography in 50 normal subjects in the standing position on a force platform by applying vibratory stimulations to the muscles. The length of the displacement of the center of gravity, maximum sway length and sway area were measured. The amplitude of the body sway was maximum when the stimulation was applied to the dorsal neck. The forward shift of the center of gravity was also marked by stimulation applied to the dorsal neck. The amplitude of the body sway on stimulation of the leg muscles was also marked, although less than that of dorsal neck stimulation. The backward shift during stimulation of the gastrocnemius and the forward shift during stimulation of the anterior tibialis were remarkable. The results indicate that the leg muscles, which directly regulate the movement of the ankle joint, and the dorsal neck muscles, which change the static equilibrium through the central nervous system, are important for maintaining the standing posture.     

静态平衡功能定量分析

目的测试正常人各年龄段之姿势图，并比较正常人与眩晕者姿势图的各参数。方法采用日本Anima公司G5500型静态平衡仪对164名正常人及167名眩晕病人进行重心动摇测试。受试者直立于平衡台上，足底中心与平台之基准点一致，睁闭眼各测60S，计算机绘制人体重心移动的图形，重心移动的外周面积、轨迹长度、XY轴偏离基准点的距离；重心摇动波谱的谱质量分析。结果（1）睁闭眼立于平台60S的各参数中，以重心移动的外周面积及轨迹长度的变量能最精确地代表平衡功能．20～49岁正常人较20岁以下、50岁以上者重心移动的外周面积小、轨迹短，有统计学差异；（2）正常人重心在矢状面（Y轴）位移，大于冠状面（X轴）位移，且有统计学差异；（3）重心动摇的频谱分析，正常人与病人谱质量集中于0．2～1．9Hz的中频段，约占54～62％；其次是0．02～0．19Hz的低频约占24～30％；2～10Hz的高频段只点12～16％；（4）正常人睁闭眼轨迹长度比值均在1.32以下，末梢与中枢眩晕病人之比值分别为1．49及1．5，与正常人有统计学差异，说明眩晕者维持平衡更多依赖于视觉代偿。结论姿势图测定是无创性、定量检查方法，可以判断前庭功能状态，是继眼震电图以后，了解前庭系统功能的另一途径。     

年龄和视觉对直立静态平衡的影响

为研究年龄和视觉系统对人体立位姿态平衡功能的影响，应用ST－939人体重心平衡仪，对127名正常人进行立位姿态平衡功能测试，观察重心移动的外围面积、路径总长和平均速度以及重心在不同圆内的分布图（即姿态图）结果显示：①正常人重心移动的外周面积、路径总长和平均速度随年龄增长而增大；②70岁组闭睁眼测试面积差值最大。本项研究结论认为在20～60岁年龄内姿态平衡功能最佳，60岁以后出现衰退。在年长者中视觉系统在控制立体姿态平衡中起重要作用。     

Postural Stability of Preoperative Acoustic Neuroma Patients Assessed by Sway Magnetometry: Are They Unsteady?

OBJECTIVE: The objective was to evaluate the preoperative postural stability of acoustic neuroma patients using sway magnetometry. STUDY DESIGN: Prospective two-center study. METHODS: Fifty-one patients (mean age, 53 years) diagnosed with unilateral acoustic neuroma on magnetic resonance imaging at two tertiary referral centers were studied. Preoperatively, each patient had sway patterns (with eyes open and with eyes closed, and standing on foam) recorded for 120 seconds by sway magnetometry. Path length for 30 seconds was calculated. The Romberg coefficient (path length with eyes open divided by path length with eyes closed) was calculated. RESULTS: Forty-four percent of patients had abnormal path lengths with eyes open, and 49% with eyes closed. The Romberg coefficients were significantly lower than normal (P <.001; 95% CI, 0.19-0.87). Mean Romberg coefficient was 0.59 (normal value = 0.73), and all patients had a coefficient of less than 1. CONCLUSIONS: Half of preoperative acoustic neuroma patients are unsteady, exhibiting abnormal sway patterns based on path length measurements. The increase in sway path length demonstrable in normal subjects with eyes closed was significantly exaggerated in patients with acoustic neuroma.     

Long-term postural abnormalities in benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo (BPPV) is a disorder in which patients suffer from acute rotatory vertigo due to the presence of free otoconial debris migrating into one or more semicircular canals during head movements and resulting in abnormal stimulation of the ampullary crest. A prolonged loss of equilibrium of unclear origin is also present. Static posturography is a useful tool for the study of postural control systems and their role in these abnormalities. The aim of the present study was to evaluate the frequency of body sway and long-term instability of BPPV patients by posturography frequency analysis. Twenty patients with canalithiasis of the posterior semicircular canal and 20 normal controls were subjected to static posturography. Informed consent was obtained from all subjects. Patients were tested 1 h after diagnosis, and 3 days and 12 weeks after the characteristic Epley repositioning maneuver. Patients with BPPV showed significantly increased body sway both on lateral (X) and anteroposterior (Y) planes compared to normal subjects. Corporal oscillation with a broad-frequency spectrum was observed in both closed and open eye tests. The repositioning maneuver decreased the X plane body sway, while the anteroposterior sway was unchanged. Twelve weeks after treatment, a normalization of the anteroposterior sway was observed. Results of this study suggest that the long-term postural disturbance associated with BPPV differs from the acute disequilibrium that subsides after canalith repositioning: the former is a sagittal plane/broad spectrum body sway, while the latter is primarily a frontal plane/low frequency sway. The Epley maneuver was shown to reduce frontal sway, a postural abnormality that might therefore be linked to posterior semicircular canal function. Conversely, the observed sagittal body sway was only partially relieved by the restoration of canal function, and therefore, may be more related to the chronic dizziness observed in these patients.     

Postural stability after vestibular schwannoma surgery

Factors related to postural stability and the course of recovery after vestibular schwannoma surgery were analyzed in a retrospective study of 177 patients and in a prospective study of 44 patients. Before surgery, 7 of the 44 patients in the prospective group complained of postural instability. The body sway velocity was measured. In the retrospective study, the sway velocity was abnormal under nonvisual control in 63% of the patients and under visual control in 34%. The sway velocity correlated with tumor size, smooth pursuit deficit, and postoperative work history. We compared patients with abnormal postural control to those with normal postural control, and found that the former relied to a greater extent on visual information and the latter on proprioceptive information. In the prospective study, the sway velocity increased after the operation, and 1 year after surgery it had not returned to preoperative values. In the logistic regression analysis, a translabyrinthine approach, rehabilitation, the patient's age, and preserved function of the facial nerve predicted a good outcome of postural stability. The retrosigmoid approach and depression were the most significant risk factors for postoperative gait difficulties. Vestibular rehabilitation increased the reliance on proprioception for maintenance of postural control and improved postural stability.     

Postural behaviour responses to visual stimulation in patients with vestibular disorders

Patients with different vestibular disorders exhibit changes in postural behaviour when they receive visual stimuli, reproducing environmental stimulation. Postural control was studied using an AMTI Accusway platform, measuring the confidential ellipse (CE) and sway velocity (SV). Postural responses were recorded according to the following stimulation paradigm: i) without specific stimuli; ii) smooth pursuit with pure sinusoids of 0.2 Hz (foveal stimulation); and iii) optokinetic stimulation (retinal stimuli). Patients with central vestibular disorders (CVD), cerebellar damage and unilateral peripheral vestibular lesions (UPVL) in asymptomatic periods were studied. A group of normal subjects was studied as control. Signal processing was done with a scalogram by wavelets in order to observe the relation between time and frequency in postural control. While patients with CVD and cerebellar disease showed a significant increase in CE and SV in the three conditions of the paradigm compared to the normal group, the patients with UPVL showed no change. Wavelets processing showed that the main sway occurs in the Y axis (antero-posterior) and below at 0.4 Hz in normal subjects, while the CVD and cerebellar patients showed sway frequencies in both the X and Y axes. The clinical implications of these findings are discussed.     

A comparison between oculomotor rehabilitation and vestibular electrical stimulation in unilateral peripheral vestibular deficit

Rehabilitation therapy is proved to be effective in reducing disability in patients with persistent symptoms of disequilibrium after acute unilateral peripheral vestibular deficit. The aim of this study was to evaluate the effects of oculomotor rehabilitation (group 2) on static balance and a dizziness handicap and to compare those with the effects to vestibular electrical stimulation (group 1). Before and after therapy, we tested 28 patients, using static posturography and.the dizziness handicap inventory short form. After therapy, all subjects reported a reduction of symptoms (p = .00019). In group 1, the reductions seen in eyes-opened length of the oscillations and eyes-opened and eyes-closed surface of the body sway were statistically significant, respectively (p = .04; p = .02; p = .02). Group 2 patients revealed better stability on all parameters, and the reductions of eyes-opened length and of eyes-opened correlation function between length and surface were statistically significant (p = .01 and p = .01, respectively). Analysis of the equilibrium system subcomponents did not show any variation. Oculomotor exercises,employed in most rehabilitative protocols and including head movements to improve vestibular adaptation, have proved to reduce the perceived overall impairment and postural sway in patients with recent unilateral vestibular disorders, even though the disorders are not associated with head movements. Comparison of our two study groups did not show any significant difference, revealing that both forms of therapy are effective.     

Stabilometry in balance assessment of dizzy and normal subjects.

Normal adults and patients referred to the Dizzy Clinic at the Medical College of Ohio had their standing balance assessed during combinations of normal and altered visual and somatosensory orientation conditions using a fixed-force platform to measure center-of-pressure translations. Significant differences were identified between normal subjects and dizzy patients, depending on the particular diagnostic category, the sensory condition tested, and the particular sway component being measured. Patients with central and peripheral vestibular dysfunctions had significantly greater sway than all other categories in most test conditions, especially with eyes closed and with a visual conflict dome while standing on a foam surface. The central vestibular dysfunction and peripheral vestibular dysfunction groups could be differentiated statistically under eyes-closed and visual conflict-foam conditions. The normal and psychogenic groups could not be differentiated statistically for any test conditions except one: there was significantly greater mean anterior/posterior sway displacement in the psychogenic group compared with all other diagnostic categories for the eyes-open foam test condition. Our results indicate that static stabilometry recordings of postural sway can be used to evaluate and quantify a dizzy patient's ability to receive and process vestibular, visual, and somatosensory-proprioceptive cues for postural stability. It can also be used to monitor patients with vestibular disorders and to document their responses to rehabilitation programs.     

Temporal changes in postural sway caused by ultrashort-acting hypnotics: triazolam and zolpidem

Two ultrashort-acting hypnotics, triazolam 0.25 mg and zolpidem 10 mg, were studied for their effects on equilibrium function in humans. Eight healthy male subjects participated in a double-blind, placebo-controlled study after informed consent. They subjected to static equilibrium tests, oculomotor tests and an assay of drug concentrations in the blood. Zolpidem was statistically significant in postural sway in tandem stance test, as defined by parametric values of tracing sum length and polygonal area of foot pressure center measured by a gait analysis system. In the tandem stance test, triazolam was statistically significant in postural sway only as defined by the polygonal area. However, in the Romberg test, the only statistically significant difference in zolpidem use was observed in polygonal area values. Blood concentrations of triazolam and zolpidem were found to closely correlate with the extent of postural sway in both tandem stance and Romberg tests. In this study, zolpidem with minimal muscle-relaxant effect incurred imbalance more extensively than triazolam, which is known for its effect of muscle relaxation. In addition, gaze deviation nystagmus was observed only in zolpidem use in 5 of 8 subjects (62.5%). From these results, it is suggested that in the use of hypnotics, sway derives from the suppression of the central nervous system relevant to awakening rather than from muscle relaxation. The prior reference to blood concentrations of hypnotics should help improve safety care in minimizing loss of balance control and possible fall.