Cervical muscle afferents play a dominant role over vestibular afferents during bilateral vibration of neck muscles

A previous study showed that vibratory stimulation of neck muscles in humans induced short-latency electromyographic (EMG) activation of lower leg muscles, producing postural reactions at the feet. These findings indicated that cervical proprioception contributes to stabilization of stance through rapidly integrated pathways. However, as vibration may excite both proprioceptive and vestibular afferents, and because of the proximity of neck muscles to the vestibular apparatus, neck muscle vibration could also have activated the vestibular system thereby contributing to the effect observed. To investigate any possible contribution of vestibular stimulation, vibratory stimuli were applied bilaterally and separately to the splenius muscles of the neck and the planum mastoideum overlying the vestibular organs. Ten normal subjects, with eyes closed, were exposed to vibratory stimulation of two different amplitudes and frequencies. Responses were assessed by EMG activity recorded from tibialis anterior and gastrocnemius muscles of both legs and by changes in center of pressure as measured by a force platform. Results indicated that vibration induced reproducible EMG and postural responses in the anteroposterior direction, particularly on cessation of vibration. EMG and postural responses were considerably lower and less consistent with mastoid vibration compared with neck muscles vibration. Previous reports suggest that vibratory stimulation could propagate to the vestibular organs and generate a vestibular-induced postural activation. However, our findings indicate that cervical muscles afferents play a dominant role over vestibular afferents when vibration is directed towards the neck muscles.     

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 neck muscle vibration on subjective visual vertical: comparative analysis with effects on nystagmus

In patients with unilateral vestibular dysfunction, vibratory stimulation to the neck muscles not only induces shift of the subjective visual vertical (SVV), but also enhances the generation of nystagmus. In the present study, the effects of neck vibration on the SVV were compared with those on nystagmus in patients with unilateral vestibular schwannoma (14 patients; 6 males and 8 females, mean age 54.2 years). The results indicated that the presence of nystagmus and magnitude of the SVV were generally correlated, neck vibration significantly increased the abnormal shift of the SVV and the presence of nystagmus, and the effects of vibration to the ipsilateral dorsal neck were significantly larger than those to the contralateral dorsal neck on the SVV, whereas no significant difference was observed in slow phase velocity of nystagmus. The present study suggests that both SVV and nystagmus induced by vibration have many similar clinical features and may be important in assessing the unilateral vestibular dysfunction.     

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.     

Effects of ocular fixation on perrotatory nystagmus in damped pendular rotation test

Summary Effects of ocular fixation on pendular rotation nystagmus were investigated in 65 patients. There were 25 with peripheral vestibular or vestibulo-cochlear disorders, 17 with central vestibular disorders, five with congenital nystagmus, 16 patients over 60 years old with vertigo in whom peripheral vestibular disorders were ruled out, however, the causes were unknown.Damped pendular rotation test (DPRT) was performed both under darkness and employing mental arithmetic and under ocular fixation. These findings were related to those of caloric vestibular suppression test (VST) by Takemori and those of optokinetic pattern test (OKP), eye tracking test (ETT), and spontaneous nystagmus.Thirteen of 17 patients with central vestibular disorders and five with congenital nystagmus showed loss of visual suppression during ocular fixation in DPRT, whereas in cases of peripheral lesions, visual suppression was observed. Loss of visual suppression during ocular fixation in DPRT was often seen in cases of brainstem and cerebellar lesions. In brainstem lesions, perrotatory nystagmus was evoked during ocular fixation, whereas no nystagmus was seen in darkness with eyes open. In cerebellar lesions, perrotatory nystagmus was partly suppressed or decreased during ocular fixation. Relationships between the direction of the visual suppression during ocular fixation in DPRT and the side of the lesion were not apparent.Ocular fixation test in DPRT has a diagnostic value not only for central lesions, but for differentiating brainstem lesion from cerebellar lesion with the findings in DPRT under darkness. The findings under ocular fixation in DPRT are closely related to those of VST in cases of caloric nystagmus.     

Results of combined treatment for vestibular receptor impairment with physical therapy and Ginkgo biloba extract (Egb 761)

Vestibular receptor impairment causes symptoms called vestibular organ peripheral lesion syndrome. Subjective and objective symptoms of vestibular lesion diminish gradually in the process of vestibular compensation. Stimulating a patient to action is a basic factor that influences on the compensation process. The aim of our studies was an evaluation of treatment results in patients with vertigo of peripheral origin with the use of gingko biloba extract together with kinezytherapy. Ginkgo biloba extract shows vasoactive, rheologic, metabolic and neural effects. We have examined 45 persons aged between 35 and 48 years (38 on average, 35 female, 13 male) with clinical symptoms of peripheral vestibular lesion. In each case we performed as follows: ORL physical examination, pure tone audiometry, suprathreshold audiometry, electronystagmography (eyes open and closed nystagmus, cervical tests, caloric tests according to Hallpike), static and dynamic posturography. In all of the cases vestibular rehabilitation originally programmed in our Clinic was applied. N 23 cases (17 female and 6 male) chosen at random, kinezytherapy together with gingko biloba in tablet was applied: 2 tablets twice a day for 3 months. Control examination were performed on 30, 60 and 90 days of treatment. Treatment results evaluation was based on anamnesis, electronystagmography, static and dynamic posturography. CONCLUSIONS: 1. In almost all of the cases with peripheral lesion of vestibular organ, after 30 days of application of gingko biloba extract together with kinezytherapy and without gingko biloba there was vestibular compensation confirmed in electronystagmography but there were disturbances in static and dynamic posturography. 2. Control examination in the course of treatment revealed gradual improvement in vestibular tests in both group (with and without biloba extract). But in patients treated with gingko biloba extract the improvement was more clear and faster an dynamic posturography. It implies central effect of gingko biloba extract that allows to gain full vestibular compensation sooner.     

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.     

Diagnostic value of vibration-induced nystagmus obtained by combined vibratory stimulation applied to the neck muscles and skull of 300 vertiginous patients.

On subjects with unilateral vestibular dysfunction, the application of a vibratory stimulation (100 Hz) to the two mastoids and the vertex, and to the right and left dorsal neck muscles produces a nystagmus directed towards the good ear in 85% of patients. Fixation must be suppressed by Frenzel's glasses or video nystagmoscopy. To be significant this nystagmus must appear in at least 3 of the 5 vibratory stimulated sites. On healthy subjects nystagmus is present in 6% of cases but never in those below 30 years. In subjects affected by central vertigo, nystagmus was elicited in 10% of cases and in subjects suffering from vertigo of unknown origin in 6% of cases. Vibration nystagmus which stops immediately after stimulation differs from head shaking nystagmus which is present in only 34% of unilateral vestibular dysfunctions. Vibration occasionally produces a pseudo-caloric nystagmus which persists after stimulation. We believe that vibratory stimulation is a useful test, quick and easy to perform. In conjunction with questionnaires, clinical examination, positional testing and the results of audiometry, it gives an immediate indication of a peripheral lesion when the vertigo is seen for the first time. With unilateral deafness, a positive test leads one to suspect an acoustic neuroma. Conversely if the test becomes negative after a vestibular neuritis when it was initially positive, it is a sign of recovery.     

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.     

Significance of pressor input from the human feet in anterior-posterior postural control. The effect of hypothermia on vibration-induced body-sway

The importance to postural control of the mechanoreceptors of the soles was investigated in thirteen healthy subjects. Body-sway velocity was evaluated before and after exposing the subject's feet to hypothermia, and when calf muscles were exposed to vibration at frequencies between 20 and 100 Hz. Subjects were tested both with eyes open and closed. Body-sway velocity was found to increase significantly during hypothermia of the feet. The difference in body-sway between hypothermal and normothermal conditions was less prominent when the subject's eyes were open though the difference was significant in both cases. The present results indicate the importance of the mechanoreceptors of the soles to postural control and elucidate their interaction with compensatory visual input in maintaining postural control. These findings also suggest, that factors affecting pressor input should be taken into consideration when assessing patients with complaints of dysequilibrium.     

Effects on the vestibulo- and opto-oculomotor system in rats by lesions of the commissural vestibular fibres

Eye movements were recorded from rats with a magnetic search coil system before and after sectioning of the midline commissural pathways in the brain stem at the level of the vestibular nuclei. After lesion, the findings were as follows: 1) During sinusoidal vestibular stimulation the eyes moved in a sinusoidal way similar to the head movement without any regular saccades. There was a reduced gain and a phase lead. 2) During optokinetic stimulation the eyes moved in the stimulus direction to an excentric position and stayed there until stimulation ceased. 3) During acceleratory/deceleratory rotation in the light there was a drift of the eyes in the direction of the expected slow phase movement to an excentric position. In some animals there was a directional asymmetry. The findings may be explained by a failure of the central neural integrator for horizontal eye movements. The results support the hypothesis that vestibular commissural fibres are of crucial importance for the function of this integrator system.     

应用mCTSIB评价眩晕患者姿势平衡

目的：应用站立海绵垫干扰直立人体本体觉,探讨该方法的临床检查测试——感觉整合和平衡的临床改良测试（mCTSIB）在眩晕患者姿势平衡评价中的意义。方法：对62例前庭末梢病变和44例前庭中枢病变患者进行mCTSIB。共进行4种条件下的测试,T1：睁眼站立于坚硬平板;T2：闭眼站立于坚硬平板;T3：睁眼站立于海绵垫;T4：闭眼站立于海绵垫。每种条件下睁眼和闭眼各站立30s。记录测试中身体倾倒情况,比较患者的mCTSIB和视频眼震图仪（VNG）结果。结果：在前庭末梢病变患者中,mCTSIB的异常率是45．16％（28／62）,与VNG的一致率为67．74％（42／62）;在前庭中枢病变患者中,mCTSIB的异常率是27．27％（12／44）,与VNG的一致率为81．82％（36／44）;在所有患者中,mCTSIB的异常率是37．74％（40／106）,与VNG的一致率为73．58％（78／106）。以倾倒为参数分析其在前庭末梢和前庭中枢病变患者中出现的异常率,差异无统计学意义（χ^2=3．505,P〉0．05）。结论：mCTSIB简便易行,虽不能作为鉴别前庭末梢和前庭中枢病变的方法,但适宜于眩晕患者应用感觉信息维持平衡能力的初步评价。     

Influence of Neck Proprioception on Vibration-induced Postural Sway

Objective --Several reports have shown that the direction of the postural responses induced by vestibular stimulation is affected by the positions of the neck and torso. The aim of this study was to investigate whether the postural responses to vibratory proprioceptive stimulation of the calf muscles are affected by the position of the head and thus by proprioceptive and vestibular information from the neck and head. Material and Methods --Ten normal subjects were exposed to vibratory proprioceptive stimulation of the calf muscles when the head was maintained in five different positions: in a neutral position facing forwards, with the head turned to the right or left sides or with the head tilted backwards or forwards. Body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface. Results --The analysis showed that only the anteroposterior body sway was significantly affected by the position of the head. The anteroposterior postural responses were primarily increased during the tests with the head tilted backwards or forwards, whereas the postural responses were unaffected by head torsion towards the sides. The lateral responses were primarily affected by vision and not by the position of the head. Conclusion --The findings suggest that the responses evoked by vibratory proprioceptive stimulation of the calf muscles may be affected by different mechanisms, either by purely proprioceptive information or by an interaction between proprioceptive and vestibular information. Moreover, the increasing difference between the test conditions over time suggests that fatigue of the neck muscles may be one of the factors affecting the responses induced by the perturbations.     

Paraspinal muscle response to electrical vestibular stimulation

Galvanic (electrical) vestibular stimulation (GVS) has been used to study the role of the vestibular system in postural control by inducing postural sway in standing subjects. The purpose of this study was to determine the timing and pattern of activation in the paraspinal muscles in response to GVS and to compare these responses with those in the muscles of the lower leg. Binaural-bipolar GVS was applied to the skin overlying the mastoid processes of 10 subjects while they stood on a force plate with their eyes closed. The stimulus consisted of a 0.6 mA 5-pulse sequence. Each pulse lasted for 2 s, followed by 4 s of rest. The centre of pressure (COP) vs. time for each trial was calculated from the reaction forces and moments. Surface electromyographic (EMG) signals from the paraspinal and gastrocnemius muscles were recorded bilaterally. The EMG signals were rectified and integrated (iEMG). The iEMG from the muscles on the cathodal side of the body were then subtracted from the iEMG of the anodal side muscles, to yield a differential EMG (dEMG). Both the paraspinal and gastrocnemius muscles became activated in response to the stimulus. The pattern of activation was consistent with the changes observed in the centre of pressure. The primary response in both muscles acted to move the body toward the anode. This primary response began at 74 +/- 20 ms in the paraspinal muscles and at 118 +/- 18 ms in the gastrocnemius. A second component of the response began at 232 +/- 27 ms in the paraspinal muscles and 262 +/- 54 ms in the gastrocnemius muscles. This second phase of the response was opposite in direction to the primary response and was responsible for decelerating the body and maintaining the deviated position of the centre of mass over the base of support. Following the termination of the stimulus, the opposite pattern of muscle activation in both the paraspinal and the gastrocnemius muscles was observed. The results of this study suggest that the paraspinal muscles may play a significant role in the frontal plane response to vestibular stimulation during stance in humans.     

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.     

Influence of neck proprioception on vibration-induced postural sway

OBJECTIVE: Several reports have shown that the direction of the postural responses induced by vestibular stimulation is affected by the positions of the neck and torso. The aim of this study was to investigate whether the postural responses to vibratory proprioceptive stimulation of the calf muscles are affected by the position of the head and thus by proprioceptive and vestibular information from the neck and head. MATERIAL AND METHODS: Ten normal subjects were exposed to vibratory proprioceptive stimulation of the calf muscles when the head was maintained in five different positions: in a neutral position facing forwards, with the head turned to the right or left sides or with the head tilted backwards or forwards. Body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface. RESULTS: The analysis showed that only the anteroposterior body sway was significantly affected by the position of the head. The anteroposterior postural responses were primarily increased during the tests with the head tilted backwards or forwards, whereas the postural responses were unaffected by head torsion towards the sides. The lateral responses were primarily affected by vision and not by the position of the head. CONCLUSIONS: The findings suggest that the responses evoked by vibratory proprioceptive stimulation of the calf muscles may be affected by different mechanisms, either by purely proprioceptive information or by an interaction between proprioceptive and vestibular information. Moreover, the increasing difference between the test conditions over time suggests that fatigue of the neck muscles may be one of the factors affecting the responses induced by the perturbations.     

外周性眩晕患者的平衡功能研究

目的评价外周性眩晕患者的平衡功能并分析视觉、本体觉在平衡维持中的特点,为平衡康复治疗提供基线数据。方法研究对象分两组,正常对照组47例,男性21例、女性26例,平均年龄（36．17±13．27）岁：外周性眩晕患者组45例,男性20例、女性25例,平均年龄（47．89±13．04）岁;分别进行硬平板和泡沫板的睁、闭眼共计6种感觉模式的平衡功能测试。结果①外周性眩晕组前后向和左右向的3种感觉评分与平衡评分均较正常对照组低;②除睁眼硬板条件外其余模式的Romberg商（RombergQuotient）,即静态闭眼时姿势面积与睁眼面积的比值、身体压力中心晃动的包络面积（statokinesigram,SKG）,EP90％身体晃动轨迹点的椭圆面积、最大晃动幅值等参数均较正常对照组增大;以上差异具有统计学意义。结论外周性眩晕患者平衡功能明显下降,而且涉及视觉和本体觉构成,平衡的康复与维持需借助视觉、本体觉补偿,平衡功能检查可为制定个体化前庭康复提供参考。     

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.     

Vestibular dysfunction causing instability in aged patients

Unilateral vestibular hypofunction (UVH) is a common vestibular dysfunction. Its influence upon the vestibulospinal reflex (VSR) is studied by posturography. The postural sway is disturbed when the VSR is disregulated because of the UVH. The degree of disturbance depends on the effectivity of the central compensation. Our results indicate that these adaptive mechanisms become less effective with advancing age. The importance of ocular fixation as a compensatory mechanism is also obvious. The comparison between posturographic recordings made with eyes open and those made with eyes closed, shows that, in elderly people, more abnormal posturographic recordings are found with eyes closed. Accordingly, with regard to the problem of falling in the elderly, the function of the vestibular system must be assessed and especially its influence upon the standing posture. The combination of classical vestibular and posturographic results affords this indispensable information.