Posture testing (posturography) in the diagnosis of peripheral vestibular pathology

A Statistical and AI Analysis of the Frequency Spectrum in the Measurement of the Center of Pressure Track in the Seated Position in Healthy Subjects and Subjects with Low Back Pain

Measuring postural control in an upright standing position is the standard method. However, this diagnostic method has floor or ceiling effects and its implementation is only possible to a limited extent. Assessing postural control directly on the trunk in a sitting position and consideration of the results in the spectrum in conjunction with an AI-supported evaluation could represent an alternative diagnostic method quantifying neuromuscular control. In a prospective cross-sectional study, 188 subjects aged between 18 and 60 years were recruited and divided into two groups: "LowBackPain" vs. "Healthy". Subsequently, measurements of postural control in a seated position were carried out for 60 s using a modified balance board. A spectrum per trail was calculated using the measured CoP tracks in the range from 0.01 to 10 Hz. Various algorithms for data classification and prediction of these classes were tested for the parameter combination with the highest proven static influence on the parameter pain. The best results were found in a frequency spectrum of 0.001 Hz and greater than 1 Hz. After transforming the track from the time domain to the image domain for representation as power density, the influence of pain was highly significant (effect size 0.9). The link between pain and gender (p = 0.015) and pain and height (p = 0.012) also demonstrated significant results. The assessment of postural control in a seated position allows differentiation between "LowBackPain" and "Healthy" subjects. Using the AI algorithm of neural networks, the data set can be correctly differentiated into "LowBackPain" and "Healthy" with a probability of 81%.

Bilateral Asymmetry in Ocular Counter-Rolling Reflex Is Associated With Individual Motion Sickness Susceptibility

Accumulating evidence suggests that individual variations in vestibular functions are associated with motion sickness (MS) susceptibility. We investigated whether vestibular functions in the reflex and cortical pathways could predict the susceptibility of individuals to MS. MS-susceptible and control adults were recruited according to the Motion Sickness Susceptibility Questionnaire (MSSQ) score. Otolith reflex and cortical functions were assessed using the ocular counter rolling test and the head-tilt subjective visual vertical (HT-SVV) test, respectively. The bilateral asymmetry of each function was compared between the MS-susceptible and the control groups. Although the two tests for otolith functions were conducted using the same stimulation (lateral head tilt), bilateral asymmetry of otolith reflex rather than cortical function was significantly associated with MS susceptibility. Our data suggests that bilateral asymmetry in the otolith reflex pathway is capable of predicting susceptibility to MS to some extent. Our data also suggest that the association between vestibular function and MS susceptibility can vary based on the vehicle types. Future vehicles, such as self-driving cars, will make us aware of other vestibular functions associated with MS susceptibility.

The Feasibility of Equine Field-Based Postural Sway Analysis Using a Single Inertial Sensor

(1) Background: Postural sway is frequently used to quantify human postural control, balance, injury, and neurological deficits. However, there is considerably less research investigating the value of the metric in horses. Much of the existing equine postural sway research uses force or pressure plates to examine the centre of pressure, inferring change at the centre of mass (COM). This study looks at the inverse, using an inertial measurement unit (IMU) on the withers to investigate change at the COM, exploring the potential of postural sway evaluation in the applied domain. (2) Methods: The lipopolysaccharide model was used to induce transient bilateral lameness in seven equines. Horses were monitored intermittently by a withers fixed IMU over seven days. (3) Results: There was a significant effect of time on total protein, carpal circumference, and white blood cell count in the horses, indicating the presence of, and recovery from, inflammation. There was a greater amplitude of displacement in the craniocaudal (CC) versus the mediolateral (ML) direction. A significant difference was observed in the amplitude of displacement in the ML direction between 4-12 h and 168 h. (4) Conclusions: The significant reduction in ML displacement during the acute inflammation period alongside greater overall CC displacement may be a compensatory behaviour for bilateral lameness.

Postural symmetry evaluation using phase approximations of the follow-up CoP trajectories

This paper presents a method of postural symmetry evaluation implementing the so-called follow-up posturography. The method boils down to the assessment of similarity of the phase approximation of the counter-clockwise follow-up CoP (Center of Pressure) trajectory and the mirror image against the y-axis of the phase approximation corresponding to the clockwise follow-up CoP trajectory. The usability of the presented approach was tested on the data collected in the group of 30 patients rehabilitated after total hip arthroplasty. The observed difference between the values of the proposed postural symmetry coefficient obtained at the end and at the beginning of the rehabilitation program was statistically significant (p < 0.001). These values, however, were not significantly correlated with the values of postural symmetry coefficients computed in static posturography. Lack of significant correlations between the coefficients supports the reasoning that the new postural symmetry evaluation method quantifies symmetry of posture in terms of dynamic mechanisms, which are not manifested in the case of static posturography. As a major advantage of the herein discussed approach one can distinguish its potential to evaluate postural symmetry in dynamic conditions using relatively inexpensive single-plate posturographic platform.

Effect of blindfolding on centre of pressure variables in healthy horses during quiet standing

In a standing horse the centre of pressure (COP), measured as the resultant vertical ground reaction force (GRF) of all supporting limbs, is adjusted in response to visual, vestibular and proprioceptive information. Stabilographic analysis measures balance by tracking COP movements in the horizontal plane. Loss of visual input affects stability of balance in people and has clinical implications in that instability inherent in some neurological diseases increases with the eyes closed. The objectives of this study were to evaluate the visual contribution to postural stability in horses. The hypothesis was that the magnitude and variability of postural sway variables increases when visual input is removed. Vertical GRFs were measured using two synchronized force plates and COP movements were tracked in 20 horses as they stood without visible movements of the hooves, head or neck. Three trials of 60 s duration were recorded under sighted and blindfolded conditions. Stabilographic variables (craniocaudal and mediolateral COP amplitudes, velocities and mean power frequencies and their within-trial variabilities) were calculated and compared using univariate analysis of variance. Compared with the sighted condition, blindfolding increased the magnitude and the within-trial variability of craniocaudal and mediolateral COP amplitudes and mediolateral COP velocity. The findings indicated that loss of visual input had more effect on the measured COP variables in the time domain (amplitudes, velocities) than in the frequency domain (mean power frequency). The effects of blindfolding on postural stability should be further investigated as part of a diagnostic approach to the evaluation of balance in horses with neurological impairment.

Force plate gait analysis in Doberman Pinschers with and without cervical spondylomyelopathy

BACKGROUND

The most accepted means of evaluating the response of a patient with cervical spondylomyelopathy (CSM) to treatment is subjective and based on the owner and clinician's perception of the gait.

OBJECTIVE

To establish and compare kinetic parameters based on force plate gait analysis between normal and CSM-affected Dobermans.

ANIMALS

Nineteen Doberman Pinschers: 10 clinically normal and 9 with CSM.

METHODS

Force plate analysis was prospectively performed in all dogs. At least 4 runs of ipsilateral limbs were collected from each dog. Eight force platform parameters were evaluated, including peak vertical force (PVF) and peak vertical impulse (PVI), peak mediolateral force (PMLF) and peak mediolateral impulse, peak braking force and peak braking impulse, and peak propulsive force (PPF) and peak propulsive impulse. In addition, the coefficient of variation (CV) for each limb was calculated for each parameter. Data analysis was performed by a repeated measures approach.

RESULTS

PMLF (P = .0062), PVI (P = .0225), and PPF (P = .0408) were found to be lower in CSM-affected dogs compared with normal dogs. Analysis by CV as the outcome indicated more variability in PVF in CSM-affected dogs (P = 0.0045). The largest difference in the CV of PVF was seen in the thoracic limbs of affected dogs when compared with the thoracic limbs of normal dogs (P = 0.0019).

CONCLUSIONS AND CLINICAL IMPORTANCE

The CV of PVF in all 4 limbs, especially the thoracic limbs, distinguished clinically normal Dobermans from those with CSM. Other kinetic parameters less reliably distinguished CSM-affected from clinically normal Dobermans.

Posturography with virtual reality stimulations in normal young adults with no balance complaints

PURPOSE

To analyze the findings of posturography with virtual reality stimuli carried out in young healthy adults with no otoneurological complaints, based on the parameters center of pressure, limit of stability and sway speed for different visual stimuli, and regarding differences between female and male genders.

METHODS

Participants were 50 healthy individuals of both genders (50% female and 50% male) with ages ranging from 18 to 25 years (mean age 21.30 years), with no complaints regarding body balance, and with vestibular outcomes assessed through digital vectonistagmography within normal limits. Posturography was composed of 11 visual stimuli and determined the limit of stability area (LOS), the ellipse area, and the sway speed in ten sensorial conditions. Results were calculated for the studied age range and analyzed according to the values for each stimulus, with the aim to obtain normality parameters.

RESULTS

The average values obtained in posturography regarding limit of stability, ellipse area and sway speed for stimuli with viso-vestibular interaction presented significant differences between genders, and, in all cases, women obtained lower values than men.

CONCLUSION

The findings of posturography with virtual reality stimuli in healthy young adults evidence that the parameters center of pressure, limit of stability and sway speed present differences between genders and, therefore, must be considered separately.

Avaliação da manobra de reposicionamento de Epley em indivíduos com vertigem posicional paroxística benigna

OBJETIVO: avaliar os parâmetros estabilométricos após a manobra de reposicionamento de Epley em indivíduos com Vertigem Posicional Paroxística Benigna (VPPB) previamente confirmada através da manobra de Dix-Hallpike. MÉTODOS: estudo experimental que incluiu pacientes que apresentaram VPPB com nistagmo de posicionamento à prova de Dix-Hallpike, avaliados no ano de 2008, no Ambulatório Multidisciplinar de Vertigem, e que foram submetidos à manobra de reposicionamento de Epley e avaliados quanto ao equilíbrio postural pelo exame de Estabilometria, antes e após a citada manobra. RESULTADOS: os 13 indivíduos do gênero feminino com idade variando de 15 a 78 anos com VPPB, previamente confirmados e selecionados para a pesquisa, apresentaram melhora estatisticamente significante em parâmetros estabilométricos verificados da primeira para a segunda avaliação, confirmando melhora do equilíbrio postural, após a manobra de Epley. CONCLUSÃO: nesta pesquisa a manobra de reposicionamento de Epley mostrou-se como um procedimento de intervenção importante para a melhora das respostas do equilíbrio postural em indivíduos com VPPB avaliados pela estabilometria.

Posturography frequency analysis of sound-evoked body sway in normal subjects

Sound-evoked activation of the vestibular system has been suggested for a long time, and myogenic potentials have been recorded at the level of different muscular groups while a high intensity sound was applied. The aim of this study was to analyse sound-evoked postural responses in normal subjects and to correlate them with the activation of the vestibular system. Body sway was measured by posturography and elaborated through spectral frequency analysis in 40 healthy volunteers in the basal condition and after applying a sound stimulus monoaurally. Spectral frequency analysis results showed a significant increase, in presence of stimulus, of body sway at low and middle frequencies only on the lateral plane and in the closed-eyes condition. As it seems that these frequency ranges are mainly under vestibular control, our results suggest that sound activates specifically the vestibular system, and posturography during sound stimulation represents an alternative approach to assess vestibular function.

Postural control after a night without sleep

The present study analysed the efficiency of postural control after 12 h of nocturnal forced wakefulness using Romberg's test comprising 1 min of recording with eyes-open and 1 min of recording with eyes-closed, with a 1 min break between the two sessions. Our aim was to see if the decreased postural control efficiency after a sleepless night was unspecific (in both eyes-closed and eyes-open conditions) or selective (in only one of the conditions). A total of 55 students spent a whole night awake at our laboratory and were tested at 22:00 and 08:00 h. In general, the results showed that postural sway increased, performing the recording from eyes-open to eyes-closed condition. The statokinesigram length (SL or efficiency of the postural system) increased after the sleepless night, while in eyes-open condition, the length in function of surface (LFS or accuracy of postural control) and Romberg's index (or contribution of vision to maintain posture) significantly decreased. This could indicate that after a night without sleep, there is a slower elaboration of visual inputs in the postural control process. On the basis of these results, the effects of sleep deprivation on cognitive performance were considered from a neuropsychological point of view.

Avaliação de pacientes com queixa de tontura e eletronistagmografia normal por meio da estabilometria

As causas de tontura são de difícil diagnóstico. Atualmente dispomos de uma variedade de exames complementares, contudo, nenhum avalia bem a função vestibular. Os testes mais utilizados para este fim são as provas eletronistagmográficas e posturográficas. OBJETIVO: O objetivo do trabalho foi o de analisar os resultados da estabilometria de pacientes com queixa de tontura que apresentaram eletronistagmografia normal e compará-los aos de um grupo controle. FORMA DE ESTUDO: Prospectivo, do tipo seccional transversal. MATERIAL E MÉTODO: Realizou-se no SME do Serviço de Otorrinolaringologia do HUCFF/UFRJ. No total foram avaliados 22 pacientes (15 mulheres e sete homens) com idade média de 47,6±9 anos. O grupo controle foi de 25 sujeitos saudáveis (18 mulheres e sete homens) com idade média de 46,8±7 anos. Todos os indivíduos foram submetidos à estabilometria com os olhos abertos, em seguida por olhos fechados, durante 30 segundos cada. RESULTADOS: O grupo de pacientes apresentou resultados estatisticamente significativos em todos os parâmetros estabilimétricos avaliados quando comparados ao grupo controle. Na comparação dos resultados com os olhos fechados e abertos, apenas a velocidade média ântero-posterior no grupo controle foi significativa. CONCLUSÃO: Conclui-se que o grupo de pacientes apresentou resultados estatisticamente significativos em relação ao grupo controle em todos os parâmetros estabilométricos analisados, demonstrando, assim, que o grupo de pacientes com queixa de tontura apresentou maior instabilidade na posição ortostática do que o grupo de sujeitos saudáveis.

Evaluation of patients with dizziness and normal electronystagmography using stabilometry

The causes of dizziness are difficult to be diagnosed. At present we have a variety of tests and exams but none of them can adequately evaluate the vestibular function. The most commonly used tests are electronystagmography and posturography. Aim: The objective of this study was to analyze the results of stabilometry in patients with complaints of dizziness who had normal results in electronystagmography and to compare them with a control group. Study Design: The study was prospective and transversal. Material and method: It was conducted at the ENT department, University Hospital, Federal University of Rio de Janeiro. Twenty-two patients (fifteen women and seven men) aged on average 47.6±9 were evaluated. The control group was made up of twenty-five healthy individuals (eighteen women and seven men) aged on average 46.8±7. Results: In all analyzed parameters, there were statistically significant differences between the groups. Comparing the results with closed and opened eyes, the anterior-posterior mean velocity in the control group was the only statistically significant result. Conclusion: We concluded that the group of patients had statistically significant results in relation to the control group in all the analyzed parameters, showing that the group of patients with complaints of dizziness had more instability in standing position than the group of healthy individuals.

Effects of head extension on undisturbed upright stance control in humans

The purpose of the present experiment was to investigate whether and how the head extended posture, commonly encountered in many routine activities, affects undisturbed upright stance control mechanisms in humans. Sixteen young healthy adults stood feet together, with their eyes closed and were asked to sway as little as possible in two Neutral and Extended head conditions. Centre of pressure (CP) displacements, recorded using a force platform, were used to compute the motions of the vertical projection of the centre of gravity (CG(v)) and those of the difference CP - CG(v). A time-domain analysis shows increased mean velocity and surface covered by the trajectory of both elementary motions in the Extended head condition. A frequency analysis also reveals increased root mean squares on the CP - CG(v) motions, suggesting increased muscular activity in the Extended head condition. Furthermore, similar changes occur on CG(v) motions. Finally, modelling these trajectories as a fractional Brownian motion process demonstrates increased spatial transition point co-ordinates at which the corrective process is initiated and a more deterministic control mechanism in this corrective process involving CG(v) motions in the Extended head position. Together, the present findings suggest that head extension position yields a reorganisation of the control mechanisms for maintaining undisturbed upright stance.

Caloric response and postural control in patients with nasopharyngeal carcinoma after radiotherapy

Since radiotherapy is the treatment of choice for nasopharyngeal carcinoma, the influence of irradiation on the temporal bone is of great concern for these patients. In this study, the caloric test and posturography were used to investigate vestibular function in 41 irradiated patients with nasopharyngeal carcinoma. Caloric testing showed a high incidence of canal paresis; five unilateral and 10 bilateral. Factors such as middle ear effusion had no significant effect on the occurrence of canal paresis. Posturography showed no difference from the control group. The authors conclude that the influence of irradiation on the vestibular apparatus of patients with nasopharyngeal carcinoma might result in a canal paresis, while postural control is preserved. Central compensation may play an important role in the postural control of these patients.

Early recognition of postural disorders in multiple sclerosis through movement analysis: a modeling study

In the present study, spontaneous postural behavior has been analyzed in freely standing multiple sclerosis (MS) patients, exhibiting no clinically assessable abnormalities of postural control. This population has been compared with two other groups, healthy people and hemiparetic patients. This latter group represents a situation where the central nervous system (CNS) lesion is precisely localized in one anatomical site and no signal-conduction disorders are present; i.e., it has an opposite anatomical character with respect to the MS at a preclinical stage. The hypothesis underlying the modeling study is the presence of a controller block working in a feedback posture control system. This controller block receives the body sway as input, and produces the corresponding ankle torque stabilizing the body, the latter being modeled as an inverted pendulum. The CNS damage, caused by MS, is supposed to be reflected in some detectable change in the structure of the controller of the posture control system. The identification of the controller has been performed by means of a parametric estimation procedure which employed as input sequences, data recorded by means of a movement-analysis (MA) system. Reported findings show a structural changes of the model of the controller block in the posture control system. This result may suggest the presence of an MS-specific reorganization of the posture control system. Some speculation is finally made on the black-box approach in comparison with traditional posturography, to arrive at hypothesizing a progression path for postural disorders.

Head extension effect in static posturography

The effect of head extension on the standing position has been studied by analysis of recordings made by static posturography type III (SPGIII), a set of six test of posturography for sensory interaction. The head extension effect in posturography was evaluated by comparing the results of testing with head extension on a stable platform and on foam rubber to testing with a normal head position. In normal subjects head extension increased the postural sway, but there was no more effect on foam rubber than on the stable platform. For patients with peripheral vestibular disorders the head extension effect on the measured postural sway was evaluated by the difference from the normal condition. This difference could be positive, zero, or negative on the stable platform as well as on foam rubber. In both patients and normal subjects, foam rubber had no more effect than the stable platform. The several types of results could be seen in each category of peripheral vestibular disorders. Only minor nuances could be observed: positive differences were more pronounced in benign paroxysmal positional vertigo, whereas negative ones were more obvious in unilateral vestibular deficits. These findings, moreover, deny that head extension in SPGIII should be considered a condition revealing vestibular dysfunction, as has been supposed. As head extension has an influence on the neck proprioceptor as well as on the position of the otoliths, its effect is ambiguous, which makes the interpretation rather difficult. A neck proprioceptive as well as an otolithic explanation appears to have some clinical support.

A model of foot placement during gait

Foot placement is known to affect balance during gait; however, how foot placements are chosen is unknown. Objectives of this research were to analyze swing trajectories of the foot during gait with respect to the pelvis, and to propose a model of foot placement control which provides a stable base of support. Effects of gait speed and vision on this model of foot placement were then examined. Foot trajectories were analyzed using spherical coordinates referenced to the pelvis, termed the pelvic spherical coordinates (PSCs). A model was developed based on this coordinate system which predicts foot placement in terms of position and velocity with respect to the pelvis. It is proposed that foot placements are chosen to minimize the sum of PSC coordinates of the stance and swing feet. Foot velocity at heel contact is proposed to minimize the sum of the PSC stance and swing angular velocities. Experimental data were collected to test this model during walking trials of different speeds, both with and without vision. Results showed that sums of stance and swing feet PSCs were very close to zero at heel contact, supporting the positional control hypothesis. Sums of PSC velocities, however, were not zero at heel contact. Rather, individual swing leg PSC velocities were zero at heel contact, suggesting independent swing leg velocity control. Vision did not have an effect on position or velocity variables at heel contact. Gait speed did have an effect, particularly on PSC velocities at heel contact.(ABSTRACT TRUNCATED AT 250 WORDS)

Sensory interaction posturography in patients with benign paroxysmal positional vertigo

BPPV (benign paroxysmal positional vertigo) is a very common peripheral vestibular disturbance. The dysfunction becomes manifest mainly by vertigo and typical nystagmus. However, the vestibulospinal reflex (VSR) can also be disturbed. This can be shown by the SPGIII (static posturography type III), which is a platform technique evaluating 'sensory interaction' in a way comparable to that of the Equi-test. Half the patients with BPPV show disturbed posturographic results. By interfering with the sensory input of vision and/or proprioception, the separate contribution of each input can be evaluated. Different 'formulae' are seen, from complete normal results, through 'overall' formulae, i.e. an undifferentiated influence in all test-conditions, to specific formulae, where we find 'eye-closure' and 'head retroflexed'-effect and so-called 'vestibular formulae'. These formulae are an expression of the different degrees of compensation achieved by the centres and especially of the 'substituting' compensation by vision and proprioception. These results confirm that posturography does not provide a typical results-pattern, thus the type of peripheral vestibular disorder cannot be diagnosed by it alone. The results give functional information on how the standing position is achieved in these patients with a disturbed VSR-input. The several formulae prove that indeed different compensatory patterns are possible, as has been shown by experiments on vestibular compensation.

Postural compensation in children with congenital or early acquired bilateral vestibular loss

The relative roles of different receptor systems in compensating for vestibular loss were studied in 18 children (12 to 16 years of age) with congenital or early acquired bilateral vestibular loss (BVL) and impaired hearing, and compared to that in 33 normal children (9 to 16 years of age). Postural stability was studied with posturography evaluating the velocity of anterior-posterior body sway. With closed eyes the increase of sway velocity did not differ between the groups, either with or without simultaneous proprioceptive disturbances when the subjects were standing on a bare surface. Body sway velocities were found to increase more in subjects with a BVL than in normal children when subjects were standing on foam rubber. When proprioceptive cues were disturbed, body sway velocities increased in both groups, but significantly more in children with BVL when subjects stood on foam rubber. This occurred both with and without open eyes.

New posture equilibrometer for the diagnosis of vestibular disease

The vestibulospinal level of vestibular function is commonly neglected in the evaluation of vertiginous patients. We have now developed a new posture equilibrometer. A transducer is placed on the head of the subject being tested. With this meter we can record body swaying, X (left-right) and Y (fore-aft) components of angular displacement, angular velocity, and angular acceleration. A detailed analysis of the data can be made by having patients keep their eyes either open or closed during the Romberg test. The head is turned left or right in this test, while the eyes are opened and closed in the Mann test. The posture equilibrometer has enabled us to evaluate more precisely vestibulospinal function and sensory interactions.

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.

Vestibulospinal findings in two syndromes with spontaneous vertigo attacks

The influence of vestibular dysfunction upon the vestibulospinal reflex (VSR) in two common peripheral syndromes was investigated by two types of posturographic examination: "static" posturography, recording and analyzing the postural sway in stance, and "kinetic" posturography, recording the stepping in place test. The influence of the dysfunction was examined outside the attacks, ie, between attacks and not during or immediately after an attack, in patients with Meniere's disease and in others with a sudden vestibular loss syndrome, "neuronitis." However, in both syndromes the influence of the dysfunction was obvious only in some patients; this indicates that central adaptation intervened in the other patients. In this way, central compensation related to the VSR was assessed and compared with compensation for the vestibulo-ocular reflex assessed by the rotation tests. Discordance was shown in a number of cases, ie, a number of cases showed compensation for one reflex, but not for the other. Comparison of the results of both posturographic methods also showed discordance. Normal performance in the walking test could not always be correlated with normal performance in the standing test and vice versa.

Clinical application of vestibulospinal reflex tests in peripheral vestibular disorders

The influence of peripheral vestibular disturbances upon postural behaviour can be measured by posturography (PG). The results show that both otolithic and canal dysfunction can have some influence, whereas central compensation tries to suppress it. In this way, central compensation can be assessed by PG, which adds complementary information sui generis to the data of the 'classical' evaluation of a dizzy patient.

Effect of labyrinthine dysfunction upon head oscillation and gaze during stepping and running

Head oscillations and eye movements when stepping and running were studied in normal subjects and in patients with labyrinthine dysfunctions. In normal subjects, whereas linear head oscillations in the horizontal plane were very limited during both stepping and running, a marked increase in the vertical linear displacement induced pitching motions of the head during running. Patients with unilateral and bilateral lesions complaining of oscillopsia manifested lateral and diffuse oscillations, respectively, in the horizontal plane during stepping. The ratio of eye amplitude to head amplitude in the vertical plane showed larger values in subjects with labyrinthine lesions than in normals. The present results suggested that oscillopsia during upright locomotion is closely related to linear head oscillations with irregular and high-frequency components, in addition to dysfunction of the vestibulo-ocular reflex.

Vestibulo-ocular reflex and gaze functions in a patient with congenital inner ear anomalies

We report on the vestibulo-ocular reflex (VOR) and gaze functions during horizontal rotations as well as upright locomotions in a fisherman with congenital inner ear anomalies. The finding of a marked gaze disturbance due to low VOR gain during passive rotations resembled that found in early acquired lesions. There was an improvement during active rotations, suggesting an intensified cervico-ocular reflex. Although head oscillations in the horizontal plane were abnormally large during stepping and running, they were compensated for visually even at high frequencies. The absence of complaints of oscillopsia as well as his ability to achieve proper balance seemed to be accomplished by his optokinetic ability, regularly transformed head oscillations and modified perceptive mechanisms at higher cortical levels.

Postural body sway and exposure to high-energy impulse noise

Detailed neurological and audiological examinations and body-sway measurements with a stable platform were carried out on 60 subjects who had been exposed to high-energy intermittent noise from firearms and had various degrees of noise-induced hearing loss. The results were compared with those for 115 healthy controls. The exposed subjects showed significantly more body sway, estimated as movement of the centre of gravity in the horizontal plane, than the controls. This swaying correlated poorly with the recalled level of noise exposure, though subjects with more severe hearing loss (by audiometric deterioration of high-frequency sound, 4 kHz and 6 kHz) showed more sway than those with less severe hearing loss. Age was not significantly correlated with body sway among the controls but men seemed to sway more than women. These results suggest subclinical disturbance of the vestibular system among subjects with impulse-noise-induced hearing loss.