Visual Influence on Postural Control,With and Without Visual Motion Feedback

Body sway was investigated in 20 healthy subjects to determine whether visual input must contain motion feedback information from the surroundings in order to influence postural control. Posturography was used to record body sway under the following visual conditions: eyes open with or without a restricted visual field; eyes open in ganzfield white light; eyes open in darkness with a head-fixed visual target; eyes open in darkness; and eyes closed in darkness. Stance was perturbed by means of a pseudorandomly applied vibratory stimulation to the calf muscles. Least sway was found with eyes open in an unrestricted visual field but increased in a restricted visual field. Greatest sway was found without visual motion feedback, i.e. under the following conditions: eyes closed; eyes open in darkness; eyes open in ganzfield white light; and with a head-mounted fixation point. Sway was significantly ( p < 0.05) greater with eyes open in darkness compared with eyes closed during the initial 50 s with perturbations. After 150 s, sway was almost identical under the four test conditions without visual motion feedback. Standing with eyes open in darkness was initially a disadvantage compared with having the eyes closed. The postural control system may be programmed to expect visual feedback information when the eyes are open, which may delay changes in postural strategy.     

Postural adaptation in elderly patients with instability and risk of falling after balance training using a virtual-reality system

Our aim in this study was to assess postural control adaptation quantitatively in unsteady elderly patients at risk of falls in open spaces and given balance training with a virtual-reality system reproducing environmental stimulation. Using a balance rehabilitation unit based on a virtual-reality system that changes sensory information (visual, vestibular, and somatosensory), we treated 26 elderly, unsteady patients who were prone to falling (age range, 73-82 years) and who were enrolled in a customized vestibular rehabilitation program. We assessed postural responses by posturography before and after 6 weeks in the vestibular rehabilitation program under two conditions: (1) standing, eyes open, static visual field, and (2) standing, eyes open, dynamic visual field through virtual-reality goggles, generating horizontal optokinetic stimulation (70 degrees per second angular velocity). We recorded postural responses with a platform measuring the confidential ellipse of the center-of-pressure distribution area and sway velocity with a scalogram analyzing postural behavior by wavelets. After 6 weeks of treatment, postural response confidential ellipse and sway velocity values were lower, evincing decreased amplitudes and sway frequency contents in the scalogram by wavelet under both stimulation paradigm conditions. These findings suggest postural adaptation under the two perceptual conditions when patients had static and dynamic visual fields. The possibility of treating elderly fallers with balance disorders using a virtual-reality environmental stimulation reproduction system is discussed.     

A quantitative analysis of postural control in elderly patients with vestibular disorders using visual stimulation by virtual reality

IntroductionPostural instability is one the most common disabling features in vestibular disorders.ObjectiveThis study aimed to analyze the limit of stability and the influence of manipulation of visual, somatosensorial and visual–vestibular information on postural control in older adults with vestibular disorder, with and without a history of falls.MethodsCross-sectional study. Participants – 76 elderly patients with vestibular disorder (G1, without falls; G2, with falls) and 41 healthy elderly subjects (control group; CG). Using posturography, analyzed were limit of stability area, body center of pressure, and velocity of oscillation in the standing position in 10 conditions, including open/closed eyes, unstable surface with eyes closed, saccadic and optokinetic stimuli, and visual–vestibular interaction.ResultsLimit of stability area in CG was better compared with G1-2, and center of pressure values were worse in G1 than in CG. Center of pressure area in all conditions and velocity of oscillation in the following conditions: open/closed eyes, optokinetic stimulation, and visual–vestibular interaction showed worse values in G2 than in CG. Center of pressure area in the following conditions: open/closed eyes, saccadic and optokinetic stimuli, visual–vestibular interaction, and unstable surface with eyes closed showed worse values in G2 than in G1.ConclusionOlder adults with vestibular disorder presented reduced limit of stability and increased postural sway in the following conditions: conflict between visual and somatosensory information and visual–vestibular interaction. Deterioration in postural control was significantly associated with history of falls.     

Age-related changes in human posture control: sensory organization tests.

Postural control was measured in 214 human subjects ranging in age from 7 to 81 y. Sensory organization tests measured the magnitude of anterior-posterior body sway during six 21 s trials in which visual and somatosensory orientation cues were normal, altered (by rotating the visual surround and support surface in proportion to the subject's sway), or vision eliminated (eyes closed). No age-related increase in postural sway was found for subjects standing on a fixed support surface with eyes open or closed. However, age- related increases in sway were found for conditions involving altered visual or somatosensory cues. Subjects older than about 55 y showed the largest sway increases. Subjects younger than about 15 y were also sensitive to alteration of sensory cues. On average, the older subjects were more affected by altered visual cues, whereas younger subjects had more difficulty with altered somatosensory cues.     

Short-term Adaptation in the Peripheral Auditory System is Related to the AMPA Receptor

A pattern of sound-induced paroxysms of the eye and head and other spinal motor neuron synkinesis (Tullio's phenomenon) in human subjects always implies either a pathological contiguity of the tympano-ossicular chain and membranous labyrinth or a dehiscence of the bone overlying the superior semicircular canal. However, it has become clear in the last decade that sound-evoked vestibular stimulation is not only a sign of disease but also a physiological phenomenon. The examination of such physiologically sound-induced vestibular (saccular) responses contributes today to the clinical testing of the vestibular organ, mainly in the form of vestibular-evoked myogenic potentials. In this study it was observed that, in a group of 20 normal subjects, a 500 Hz tonal stimulus of high intensity (105 dB HL=118.5 dB SPL), applied monoaurally, elicited postural responses. Each subject was studied under 4 different conditions: (i) head facing forwards, eyes open; (ii) head facing forwards, eyes closed; (iii) head rotated &;#44 90° to the right, eyes closed; and (iv) head rotated 90° to the left, eyes closed. Body sway, measured using a force platform, was recorded in all subjects, with eyes either open or closed. Postural responses, which were also elicited with a 250 Hz tonal stimulus, were not observed with a tone of 2000 Hz, with legs slightly flexed or with binaural stimulation. The postural sway (head facing forwards, eyes open or closed) was in a lateral direction towards the stimulated ear: with the stimulus applied to the right ear the subject had postural sway towards the right, with the stimulus applied to the left ear towards the left. When the head was rotated &;#44 90° sideways and the stimulus was given facing forwards (i.e. head rotated contralaterally to stimulated ear) the postural sway was in a forward direction; when the head was rotated &;#44 90° sideways and the stimulus was given facing backwards (i.e. head rotated ipsilaterally to stimulated ear) the postural sway was in a backward direction. The mean values (mm) of body sway obtained with the head facing forwards and the eyes closed were higher than those with the eyes open (21.7 and 22.8 vs 15.7 and 14.7 for the right and left ears, respectively); higher mean values were obtained with the head turned to the side contralateral to the ear stimulated and the eyes closed (29.3 and 24.8 for the right and left ears, respectively). Under this condition the body sway was mainly in a forward direction. The sound-evoked vestibulopostural reflex seems to be a useful test for exploring the saccular function and, as a click-evoked vestibulocollic reflex, can be considered a physiological Tullio phenomenon.     

Sound-evoked postural responses in normal subjects

A pattern of sound-induced paroxysms of the eye and head and other spinal motor neuron synkinesis (Tullio's phenomenon) in human subjects always implies either a pathological contiguity of the tympano-ossicular chain and membranous labyrinth or a dehiscence of the bone overlying the superior semicircular canal. However, it has become clear in the last decade that sound-evoked vestibular stimulation is not only a sign of disease but also a physiological phenomenon, The examination of such physiologically sound-induced vestibular (saccular) responses contributes today to the clinical testing of the vestibular organ, mainly in the form of vestibular-evoked myogenic potentials. In this study it was observed that, in a group of 20 normal subjects, a 500 Hz tonal stimulus of high intensity (105 dB HL = 118.5 dB SPL), applied monoaurally, elicited postural responses. Each subject was studied under 4 different conditions: (i) head facing forwards, eyes open; (ii) head facing forwards, eyes closed; (iii) head rotated approximately 90 degrees to the right, eyes closed: and (iv) head rotated approximately 90 degrees to the left, eyes closed. Body sway, measured using a force platform, was recorded in all subjects, with eyes either open or closed. Postural responses, which were also elicited with a 250 Hz tonal stimulus, were not observed with a tone of 2000 Hz, with legs slightly flexed or with binaural stimulation. The postural sway (head facing forwards, eyes open or closed) was in a lateral direction towards the stimulated ear: with the stimulus applied to the right ear the subject had postural sway towards the right, with the stimulus applied to the left ear towards the left. When the head was rotated approximately 90 degrees sideways and the stimulus was given facing forwards (i.e. head rotated contralaterally to stimulated ear) the postural sway was in a forward direction; when the head was rotated approximately 90 degrees sideways and the stimulus was given facing backwards (i.e. head rotated ipsilaterally to stimulated ear) the postural sway was in a backward direction. The mean values (mm) of body sway obtained with the head facing forwards and the eyes closed were higher than those with the eyes open (21.7 and 22.8 vs 15.7 and 14.7 for the right and left ears, respectively); higher mean values were obtained with the head turned to the side contralateral to the ear stimulated and the eyes closed (29.3 and 24.8 for the right and left ears, respectively). Under this condition the body sway was mainly in a forward direction. The sound-evoked vestibulopostural reflex seems to be a useful test for exploring the saccular function and, as a click-evoked vestibulocollic reflex, can be considered a physiological Tullio phenomenon.     

Effect of head extension on equilibrium in normal subjects

A dynamic posturography system was used to test the effect of 55 degrees head extension on postural sway in 20 normal subjects. There was a highly significant increase in sway with head extension under two conditions; in both, the support surface moves proportionally to body sway angle (sway-referenced feedback). The largest increase in sway occurred when the eyes were closed and the support surface was sway-referenced. This latter condition removes vision, reduces the effectiveness of ankle proprioception, and forces the subject to depend mostly on vestibular information for equilibrium. We suggest that head extension increases sway because the utricular otoliths are put into a disadvantageous position. This may be another example of the role of utricular input in the control of balance.     

Effects of tinnitus on posture: a study of electrical tinnitus suppression

We investigated the effects of tinnitus on postural responses using posturography. Thirty-three tinnitus patients (19 female and 14 male) ranging in age from 33 to 67 years (mean age, 53) were selected randomly at our outpatient clinic. Nobody complained of dizziness. Posturographic examination was given before and after 30-minute electrical stimulation. Items tested were envelope area, area (root mean square), total length, total length-area, mean amplitude of lateral body sway (mx), and anteroposterior sway (my). Those parameters did not improve in patients without tinnitus relief. Two postural measures (envelope area and mx) showed significant improvement in patients with tinnitus relief. These effects appeared only on positions involving restricted visual feedback. In a comparison of postural measures in patients with and without tinnitus relief, all parameters except total length and mx improved significantly in patients with eyes open. Our study showed that aside from the auditory system, tinnitus can affect balance, implying that tinnitus may be a factor in increasing unsteadiness in patients with tinnitus.     

Effects of lifetime ethanol consumption on postural control: a computerized dynamic posturography study

The relationship between lifetime alcohol consumption and postural control was investigated in 35 subjects with no clinically-detectable neurologic abnormalities, using computerized dynamic posturography (CDP) procedures. The estimated total number of lifetime alcoholic drinks was positively correlated with anteroposterior sway spectral power within the 2-4 Hz and 4-6 Hz frequency bands, in three Sensory Organization Test (SOT) conditions: eyes closed with stable support surface (SOT 2), eyes open with sway-referenced support (SOT 4), and eyes closed with sway-referenced support (SOT 5). All correlations remained significant after controlling for subject age, and were increased after excluding nine drug-abusing subjects. In contrast to the strong findings for frequency-based measures, no correlation was observed using conventional amplitude-based sway measures. These results suggest that 1) alcohol consumption compromises postural control in an exposure-dependent manner, and 2) sway frequency analysis reveals pathological processes not manifested in conventional CDP measures of sway amplitude.     

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.     

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.     

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。     

Balance control in quiet upright standing in patients with panic disorder

The postural stability of 30 panic disorder (PD) patients and 30 sex- and age-matched healthy control subjects (age range 27–40 years) was investigated by static posturographic tests of quiet standing on stable and foam surfaces with open and closed eyes. Postural stability was evaluated by sway velocity (SV) and power density of relative power spectrum (RPS) in five frequency ranges. There were no differences of SV between two groups during stance with open eyes on both surfaces. The SV of the PD patients standing with closed eyes was significantly higher compared to controls for the stance on the stable surface (anterior–posterior plane) and on the foam surface (both anterior–posterior and medial–lateral planes). The stance on foam surface did not cause any significant changes in power density of postural sways of healthy subjects, while this parameter was significantly higher for PD patients, especially in closed eyes condition when a sensory conflict may exist. The higher value of SV and RPS (0.5–1.0 Hz) in patients compared to controls suggests that the visual information has more important role in the postural balance when sensory conflict exists during stance on foam surface. We proposed that the altered information from the visual and proprioceptive inputs may induce anxiety and panic symptoms in PD patients, which enhances the sensory conflict, leads to abnormal work of the vestibular system and disturbs the standing balance.     

Somatosensory shift of postural control in dizzy patients

Conclusions: Postural control is dependent on the visual system in normal conditions. Shift from visual to somatosensory dependence in dizzy patients suggests that utilizing the stable visual references is recommended for the rehabilitation of dizzy patients. Objectives: To investigate which of the visual or somatosensory system is mainly used for substitution of the impaired spatial orientation in dizzy patients. Methods: We recruited 189 consecutive patients with or without dizziness and vestibular dysfunction. Dizzy patients were divided into three groups: acute, episodic, and chronic dizziness. Vestibular function was assessed by caloric test, traditional head impulse test, and head shaking nystagmus. Visual or somatosensory dependence of spatial orientation was assessed by posturography on a solid surface or on foam in eyes open or closed condition. The foam ratio (posturography with/without foam) when eyes were closed was indicative of somatosensory dependence of postural control, whereas the Romberg ratio on foam showed visual dependence. (Romberg ratio on foam)/(foam ratio with eyes closed) was calculated and used as an index of the visual/somatosensory dependence of postural control. Results: The visual/somatosensory ratio of postural control was significantly lower in dizzy patients as well as patients with vestibular dysfunction, however, no differences were found between acute, episodic, and chronic dizziness.     

Exercise with visual feedback improves postural stability after vestibular schwannoma surgery

We analyzed the effect of 2-week individualized visual feedback-based balance training on the postural control of patients undergoing retrosigmoid microsurgical removal of vestibular schwannoma. We performed prospective evaluation of 17 patients allocated into two groups: feedback group (9 patients, mean age 37 years) and standard physiotherapy group (8 patients, mean age 44 years). Patients in both the groups were treated once per day by intensive rehabilitation from 5th to 14th postoperative day. Rehabilitation of patients in the feedback group was performed using the visual feedback and force platform. Results were evaluated on the beginning and at the end of rehabilitation program (e.g. 5th and 14th postoperative day). Outcome measures included posturography during quiet stance under four different conditions by the modified Clinical Test for Sensory Interaction of Balance. Body sway was evaluated from center of foot pressure. Compensation of Center of pressure (CoP) parameters in stance on firm surface was similar in the control and feedback groups. However, in stance on foam surface with eyes closed the patients from the feedback group were better compensated and CoP parameters differed significantly (p < 0.05). This prospective clinical study suggests that specific exercises with visual feedback improve vestibulospinal compensation in patients after vestibular schwannoma surgery and thus can improve their quality of life.     

Postural control in patients with unilateral vestibular lesions is more impaired in the roll than in the pitch plane: a static and dynamic posturography study

The postural instability of patients with vestibular loss (11 with bilateral and 101 with unilateral vestibular loss) at different times following the lesion was investigated by means of posturography and compared to healthy subjects. In addition, subjects submitted to galvanic vestibular stimulation were also studied to compare their postural performances with those of patients with complete unilateral vestibular lesion. The platform consisted of a static computerized force platform, on which a seesaw platform could be placed to test the subjects in dynamic conditions. The displacement of the center of foot pressure was measured under different conditions: subjects standing on the fixed platform, eyes open and eyes closed and subjects standing on the seesaw platform, eyes open and eyes closed. In the last condition, balance was tested in the subject's pitch plane by allowing the platform to rotate forwards and backwards only and in the patient's roll plane by allowing the platform to rotate to the left and to the right. The results showed that in static conditions, only bilateral vestibular loss patients had abnormal values compared to controls. In contrast, in dynamic eyes-closed conditions, both bilateral and unilateral patients could be differentiated from controls. Bilateral patients were unable to stand up without falling in both pitch and roll planes. Unilateral patients fell in the first week following the lesion and exhibited increased postural oscillations in both planes from the 2-week up to the 1-year postlesion stage. In addition and more importantly, they fell more often or had higher sway in the roll than in the pitch plane. Therefore, this study suggests that dynamic posturography on a seesaw platform could be a valuable tool for clinical diagnosis and quantitative analysis of imbalance in patients suffering from a unilateral vestibular loss up to 1 year after the lesion.     

Effects of hypothermic anesthesia of the feet on vibration-induced body sway and adaptation

The aim of this study was to investigate the significance of information from the plantar cutaneous mechanoreceptors in postural control and whether postural control could compensate for reduced cutaneous information by adaptation. Sixteen healthy subjects were tested with eyes open or eyes closed with hypothermic and normal feet temperature during posturography where body sway was induced by vibratory proprioceptive stimulation towards both calf muscles. The hypothermic anesthesia was obtained by cooling the subject's feet in ice water for 20 minutes. Body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface by a force platform during the posturography tests. The reduction of cutaneous sensor information from the mechanoreceptors of the feet significantly increased the vibration-induced torque variance mainly in the anteroposterior direction. However, the effects of disturbed mechanoreceptors information was rapidly compensated for through postural adaptation and torque variance was in level with that without anesthesia within 50 to 100 seconds of stimulation, both when standing with eyes open and eyes closed. Our findings suggest that somatosensory input from mechanoreceptors in the foot soles contribute significantly in maintaining postural control, but the sensory loss could be compensated for.     

Stabilization of the head position in pitch plane: study of imbalance during a multisegment posturography examination

Our purpose was to evaluate head stabilization in pitch plane in patients with different kinds of imbalance when standing over firm and movable surfaces. We used the STATITEST (Société Mumedia, Belgium), a multisegment platform for recording and computing postural adjustments at different body levels. We detected these data by two sensors placed on the head and hip of each subject in four situations: eyes open on a firm surface (EOFS); eyes closed on a firm surface (ECFS); eyes open on a movable surface (EOMS); and eyes closed on a movable surface (ECMS). For each recording, a magnetic field was broadcast by an antenna placed in front of the patients. First, as the manufacturer did not provide the normal range limits for shoulder sway, we conducted a statistical analysis on a population and selected a sample of 31 normal individuals. Second, we performed the experiment with 91 patients in two steps: standard examination and an assessment with sensors on the head and shoulder. The following values of increased head-shoulder relationship were found: on EOFS, 6; on ECFS, 5; on EOMS, 6; and on ECMS, 11. We noted the predominance of smaller head adjustments, reflecting accurate head stability. However, a small percentage of patients showed increased head movement, a pigeonlike sway. A correlation of these individuals with postural strategies revealed that almost all adopted ankle strategies.     

Head and body sway in response to vertical visual stimulation

Conclusions. Postural responses differed according to the stimulus direction, i.e. vertical visual stimulation induced head rather than trunk displacements. Accordingly, it could be that center of foot pressure (COP) responses tended to underestimate the postural sway during visual stimulation. Objectives. To investigate head and body sway in response to vertical visual surround motion, and to examine the correlation between the displacements of head and body segments derived from video-motion analysis and COP measurements. Material and methods. Postural sway was assessed in 10 young female subjects by video-motion analysis of four different head and body segments, and by use of force-plate posturography. Head and body sway in the pitch plane was induced by rotating a random pattern of dots about the subject's inter-aural axis at a constant acceleration of 1°/s² or a constant velocity of 60°/s in darkness. Results. Generally, head displacement was greater than that of other body parts during vertical optokinetic stimulation (OKS). In most subjects, maximum head displacements were induced in the same direction as the visual motion. Downward OKS induced a forward head and body sway. The COP trajectory correlated well with the displacements of each head and body segment during downward OKS. In contrast, postural responses to upward OKS were complicated in terms of their time course. The correlation coefficient between each head and body segment and the COP varied among individuals for upward OKS.     

The balance control of bilateral peripheral vestibular loss subjects and its improvement with auditory prosthetic feedback

OBJECTIVES: We investigated whether long-term bilateral vestibular loss subjects could combine auditory biofeedback of trunk sway with their remaining natural sensory inputs on balance to provide an improved control of trunk sway. A successful integration of natural and artificial signals would provide a basis for a balance prosthesis. METHODS: Trunk sway of 6 bilateral peripheral vestibular loss subjects (BVL) was recorded using either angular position- or velocity-based auditory feedback or no feedback during stance and gait tasks. Roll and pitch trunk movements were recorded with angular velocity transducers mounted just above the waist and feedback without a delay to 4 loudspeakers placed at the left, right, front and rear borders of the 5 m long by 4 m wide test environment. The two types of auditory feedback or no feedback were provided to the subjects in random order. In the feedback modes, sway greater than a preset angle (ca. 0.5 deg) or velocity (ca. 3 deg/s) thresholds caused a tone to be emitted from the speaker towards which the subject moved. The tone volume increased with increasing angle or angular velocity amplitude. RESULTS: For all stance tasks BVL subjects without auditory feedback had a significantly different balance control with respect to that of normal controls. BVL sway values eyes open on a normal surface were reduced with auditory feedback with the greatest reductions in the roll plane. Specifically for the task of standing on 1 leg eyes open with position-auditory- feedback, amplitudes of pitch and roll angles and angular velocities were indistinguishable from those of normal controls. Sway during stance tasks on foam with eyes closed showed no improvement with feedback, remaining greater than normal. For some gait tasks there was a decrease in trunk sway with velocity feedback. CONCLUSION: These initial results indicate that subjects with vestibular loss could incorporate the auditory prosthetic sensory information into their balance commands, particularly in the roll plane if the balance task is performed with eyes open. Position information appears more useful than velocity information in reducing trunk sway during stance tasks. Future work will need to determine the effect of a training time on the improvement in balance control using such a prosthetic device and the ideal position and velocity auditory feedback combination.