Postural stability and rotational tests: their effectiveness for screening dizzy patients

Impaired Vestibular Function After Cochlear Implantation in Children: Role of Static Posturography

To identify vestibular dysfunction in children after cochlear implant surgery and to study the utility of static posturography in evaluating vestibular function in children. A prospective study was carried out on 25 children between 2 and 7 years of age with sensorineural hearing loss with no overt vestibular dysfunction. All children underwent static posturography using Synapsis Posturographic System (SPS) software (Version 3.0, REV C) using a static platform with foam. The centre of pressure (COP) shift was recorded as statokinesiogram on the software and the mean vestibular, visual and somesthetic scores were obtained. Cochlear implantation (CI) surgery was done with insertion of Med-El Pulsar standard cochlear implant with 12 twin electrodes. Children were evaluated again after 4 weeks of CI surgery (2 weeks after switch on) with static posturography on the same SPS software. The scores obtained were compared with pre op value and data analyzed statistically by paired t tests on SPSS 18 software. The mean age was 4.6 years with range 2-7 years. All the children in the study were able to complete the test with no difficulty and the mean time required for each child was 10.2 min. The mean pre op somesthetic score was 95.16 (SD 1.52) and post op score was 94.06 (SD 1.79). The mean pre op visual score was 86.64 (SD 2.24) and post op score was 82.55 (2.89). The mean pre op vestibular score was 84.11 (SD 2.20) and post op score was 73.66 (SD 4.25). Correlation and statistical analysis of the pre and post values of each score revealed statistically significant reduction in vestibular scores post CI. The vestibular system is at high risk of injury leading to vestibular dysfunction in children during CI. Our study found the static posturography as a simple, fast and efficient tool to screen children for vestibular dysfunction post CI. Identifying the dysfunction early can help in initiating early rehabilitation measures.

Symptoms Associated with Vestibular Impairment in Veterans with Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a chronic and disabling, anxiety disorder resulting from exposure to life threatening events such as a serious accident, abuse or combat (DSM IV definition). Among veterans with PTSD, a common complaint is dizziness, disorientation and/or postural imbalance in environments such as grocery stores and shopping malls. The etiology of these symptoms in PTSD is poorly understood and some attribute them to anxiety or traumatic brain injury. There is a possibility that an impaired vestibular system may contribute to these symptoms since, symptoms of an impaired vestibular system include dizziness, disorientation and postural imbalance. To our knowledge, this is the first report to describe the nature of vestibular related symptoms in veterans with and without PTSD. We measured PTSD symptoms using the Posttraumatic Stress Disorder Checklist (PCL-C) and compared it to responses on vestibular function scales including the Dizziness Handicap Inventory (DHI), the Vertigo Symptom Scale Short Form (VSS-SF), the Chambless Mobility Inventory (CMI), and the Neurobehavioral Scale Inventory (NSI) in order to identify vestibular-related symptoms. Our findings indicate that veterans with worse PTSD symptoms report increased vestibular related symptoms. Additionally veterans with PTSD reported 3 times more dizziness related handicap than veterans without PTSD. Veterans with increased avoidance reported more vertigo and dizziness related handicap than those with PTSD and reduced avoidance. We describe possible contributing factors to increased reports of vestibular symptoms in PTSD, namely, anxiety, a vestibular component as well as an interactive effect of anxiety and vestibular impairment. We also present some preliminary analyses regarding the contribution of TBI. This data suggests possible evidence for vestibular symptom reporting in veterans with PTSD, which may be explained by possible underlying vestibular impairment, worthy of further exploration.

Neuroimaging to detect cortical projection of vestibular response to caloric stimulation in young and older adults using functional near-infrared spectroscopy (fNIRS)

Functional near-infrared spectroscopy (fNIRS) is a non-invasive and portable neuroimaging technique. The method uses non-ionizing laser light in the range of red to near-infrared to detect changes in cerebral blood oxygenation. In this study, we used fNIRS to investigate cortical hemodynamic changes in the temporo-parietal and frontal regions during caloric vestibular stimulation. Caloric stimulation has previously been investigated using functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), which serves as a validation of the fNIRS imaging modality toward the measurement of vestibular related brain regions. To date, only a single study has used fNIRS during caloric irrigations, which observed blood volume changes in the temporal-parietal area in healthy younger subjects. In this current study, fNIRS was used to measure cortical vestibular activation in 10 right-handed younger subjects (5 male and 5 female, age 25+/-6 years) and 10 right-handed older subjects (6 male and 4 female, age 74+/-5 years). We investigated both warm (44 °C) and cool (30 °C) unilateral caloric vestibular stimulation. Consistent with previous reports, we found that warm (44 °C) caloric irrigation caused a bilateral activation. In addition, we found that cool (30 °C) caloric irrigation caused contralateral activation of the temporo-parietal area. This study is the first to investigate age effects of the caloric stimulation on brain activity. We found that the older subjects had stronger bilateral effects than the younger subjects. Our results confirm previous fMRI and PET studies that showed cortical activation during caloric vestibular irrigation is dependent on side of irrigation, and temperature of irrigation. Furthermore, our results demonstrate that fNIRS is a viable technique in measuring cortical effects during vestibular tasks.

A comparison of electronystagmography results with posturography findings from the BalanceTrak 500

OBJECTIVE

To determine a correlation between conventional electronystagmography findings with results obtained from BalanceTrak 500 posturography assessment.

STUDY DESIGN

Individuals with a variety of dizziness and balance disorder symptoms were tested with both electronystagmography (ocular motor studies, positional/positioning testing, caloric testing) and computer posturography using the BalanceTrak 500.

SETTING

Tertiary referral center.

PATIENTS

Urban/rural midwesterners referred for dizziness and balance dysfunction symptoms.

INTERVENTION

Results of both testing modalities were sent to referring physicians.

OUTCOME MEASURES

Electronystagmography and posturography results.

RESULTS

When electronystagmography results were compared with BalanceTrak findings, a majority of patients whose electronystagmography findings indicated central and mixed causes, or peripheral lesions other than benign paroxysmal positional vertigo, had abnormal findings on posturography. Specifically, tests similar to the Balance Master Sensory Organization Tests 4 and 5 and a new test, Limits of Stability, presented the most difficulty for these individuals. Patients with normal electronystagmography findings and those with benign paroxysmal positional vertigo had mixed results on posturography. The results for specific individual electronystagmography tests were compared with those of posturography tests. No correlation was noted among any of the electronystagmography results and posturography findings. Furthermore, no correlation was observed between posturography and the causes of dizziness.

CONCLUSION

For many patients with dizziness and/or balance dysfunctions, posturography can provide additional information to that obtained with electronystagmography. This is especially apparent in individuals who have these symptoms but have normal or borderline normal electronystagmography findings.

What can posturography tell us about vestibular function?

Patients with balance disorders want answers to the following basic questions: (1) What is causing my problem? and (2) What can be done about my problem? Information to fully answer these questions must include status of both sensory and motor components of the balance control systems. Computerized dynamic posturography (CDP) provides quantitative assessment of both sensory and motor components of postural control along with how the sensory inputs to the brain interact. This paper reviews the scientific basis and clinical applications of CDP. Specifically, studies describing the integration of vestibular inputs with other sensory systems for postural control are briefly summarized. Clinical applications, including assessment, rehabilitation, and management are presented. Effects of aging on postural control along with prevention and management strategies are discussed.

Computerized Dynamic Posturography: What have we Learned from Space?

Computerized dynamic posturography (CDP) has been under development since 1970. Several reviews summarize key basic and clinical research studies and outline important clinical uses of CDP along with research applications. This report summarizes new information about the otolith control of posture obtained from the study of astronauts. The dynamics of recovery of postural control upon return from orbital flight provide insight to the peripheral vestibular and central nervous system components of vestibular compensation. The dynamics of postural compensation should aid the clinician in the diagnosis and management of imbalance of vestibular origin. (Otolaryngol Head Neck Surg 1998; 118:S45-S51.)

Classification of human rotation test results using parametric modeling and multivariate statistics

The usefulness of vestibular testing is directly related to the accuracy of the test interpretations. Two factors, subjective analysis of large test data sets and failure to make appropriate age corrections, tend to reduce test accuracy. Correction of these problems can be accomplished by application of physiologically based models of vestibular function and multivariate classification techniques to the test data, thereby creating a more objective test interpretation procedure. Herein we report our results on the use of this strategy for analysis of sinusoidal harmonic acceleration (SHA) test interpretation. For each patient, models reduce the large set of SHA test variables to three key parameters: asymptotic gain, vestibulo-ocular reflex time constant, and bias. In addition, the new technique objectively adjusts these parameters for the patient's age. Finally, each patient's set of parameters are statistically classified as either normal or as unilateral peripheral deficit. Based on learning sets of 57 normals and 30 patients with a full unilateral peripheral deficit, this new technique resulted in a misclassification rate between the categories of normal and full unilateral loss of 3.4%, comparing favorably to the present method's misclassification rate between normal and abnormal of 13.8%. We also analyzed and classified a test group consisting of patients with possible partial unilateral deficits using the same classification function as the normal and full unilateral learning sets. Even though the classifier was not optimized for the partial group, results seemed favorable relative to the human interpreter. These results validate the accuracy and utility of physiological parametric models and multivariate statistical classification in SHA test interpretation.

Unilateral peripheral semicircular canal lesion and off-vertical axis rotation

Off vertical axis rotation (OVAR) is a stimulus that can be used to assess the otolith-ocular reflex. However, experimental data suggest that isolated unilateral lesion of the lateral semicircular canal (SCC) nerve could modify responses to OVAR. Thus, to determine what nystagmus variables are not affected by SCC dysfunction and might be used as indices of otolithic disease, responses to OVAR were compared in 39 healthy controls and in 19 patients suffering from acute unilateral vestibular neuritis (VN), without any sign of otolith dysfunction. Horizontal and vertical slow phase velocities (SPV) were measured during earth vertical axis rotation (EVAR), and during OVAR at a tilt angle of 9 degrees and rotation velocity of 60 degrees/s. During OVAR, horizontal SPV consists of a sinusoidal modulation superimposed on a sustained bias opposite to the rotation. Vertical SPV consists of a sinusoidal modulation without bias. In patients, the bias shows directional preponderance (DP) toward the healthy side, strongly correlated to EVAR nystagmus DP. It would therefore simply reflect an imbalance, produced by the unilateral peripheral vestibular lesion, between right and left vestibular nuclei activity. On the other hand, vertical and horizontal modulations are not significantly different in patients and controls. Since the cause and the site of VN are not known, we cannot be sure that patients had pure SCC deafferentation. However, as all of them had SCC paresis it is concluded that OVAR modulations are not affected by a strong dysfunction of the pathways issued from the SCCs.

Otolith function tests in patients with unilateral vestibular lesions

This study was designed to assess the utility of otolith-ocular reflex testing in patients with complete unilateral peripheral vestibular deficits. Ten subjects were given a clinical vestibular test battery (ENG & vertical rotation) and research oriented tests of otolith function including dynamic posturography with head tilt and earth-horizontal axis rotation with otolith-visual interactions. Clinical tests confirmed the presence of a vestibular deficit and the side of the lesion. The results suggested the following: posturography during head tilt is not a reliable means of detecting unilateral peripheral vestibular dysfunction, while earth-horizontal axis rotation is a reliable means of assessing asymmetric otolith function. The Bias response during earth-horizontal axis rotation was significantly less during rotation ipsilateral to the lesioned ear compared to contralateral rotation while the Mod response was normal. The optokinetic test results in these subjects were normal while otolith-visual interactions were symmetrically reduced in these patients.

Clinical significance of type 5 patterns in platform posturography

Several abnormal patterns have been identified on the sensory portion of the computerized dynamic posturography test. The vestibular deficit pattern, also known as the "5-6" pattern, is frequently seen in patients with either uncompensated unilateral vestibular lesions, severe bilateral peripheral vestibular loss, or dysfunction involving the vestibular pathways in the brain stem and/or cerebellum. In both sensory conditions 5 and 6, the patient's balance/equilibrium is determined primarily by the vestibular system. A subgroup of the vestibular deficit pattern has been identified, in which only sensory condition 5 is abnormal. This article presents findings in several cases identified with the 5 pattern. Implications for diagnosis and for monitoring the recovery phase after treatment are discussed.

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.

Visual-vestibular interaction in humans during earth-horizontal axis rotation

Visual-vestibular interaction (VVI) using 60 degrees/s constant velocity earth horizontal axis (EHA) yaw rotation was measured in 7 human subjects. This so-called 'barbecue spit' rotation stimulated both the horizontal semicircular canals and the otolith organs. Subjects were tested with their eyes open in the dark (EOD), while fixating upon a target rotating with them (FIX), and while observing stationary optokinetic stripes (VVR). The resulting nystagmus slow component velocity (SCV) was analyzed. During EOD, subjects showed an exponentially decaying SCV response with a time constant of between 10 and 15 s that decayed to a non-zero baseline value (bias). Superimposed was a cyclic activity, modulation, whose period equalled the time for a complete revolution of the subject. During FIX, the average value of SCV was nearly zero indicating almost complete abolition of the exponential decay and bias components. The modulation component was reduced by half. During VVR, an exponential decay was observed in most subjects and the average value of the bias component nearly equalled that of the velocity of rotation. Modulation during VVR varied on a cycle-by-cycle basis. On average, the modulation component was nearly twice that for the EOD condition. We conclude that visual-vestibular interactions during EHA differ significantly from those during rotation about the vertical; specifically, there is a non-linear interaction between linear acceleration and optokinetic nystagmus.

Earth horizontal axis rotational responses in patients with unilateral peripheral vestibular deficits

We evaluated the vestibulo-ocular reflex (VOR) of five patients with surgically confirmed unilateral peripheral vestibular lesions. Testing used both earth vertical axis (EVA) and earth horizontal axis (EHA) yaw rotation. Results indicated that the patients had short VOR time constants, asymmetric responses to both EVA and EHA rotation, and normal EHA modulation components. These findings suggest that unilateral peripheral vestibular loss causes a shortened VOR time constant even with the addition of dynamic otolithic stimulation and causes an asymmetry in semicircular canal-ocular reflexes and one aspect of otolith-ocular reflexes.

Dynamic posturography and caloric test results in patients with and without vertigo

Patients with dizziness were evaluated with caloric stimulation and with dynamic platform posturography (Neurocom Equitest). The ability of these tests to detect abnormalities in patients with and without vertigo was assessed. In 159 patients, roughly a third had abnormal calorics while half experienced one or more "falls" during posturography. Calorics revealed proportionately more abnormalities in patients with vertigo, whereas posturography alone did not distinguish between patients with or without vertigo. Posturography did, however, identify abnormalities in a third of patients with normal calorics, regardless of their history of vertigo. Overall, more patients with vertigo had at least one abnormal test result (70%) compared with patients without vertigo (47%). We conclude that caloric abnormalities correlate with a history of vertigo, whereas posturographic deficits can be identified regardless of the presence of vertigo.

Indicators of the influence a peripheral vestibular deficit has on vestibulo-spinal reflex responses controlling postural stability

For a controlled sway stabilization task, the areas underlying EMG responses in ankle and neck muscles, as well as amplitudes of ankle torque responses, were shown to be significantly correlated with the clinically defined extent of a patient's peripheral vestibular deficit. The responses, elicited by ankle dorsiflexion of the support surface on which the subject stood, were statistically examined in order to select those measurements which would best indicate differences between a normal, a patient with a unilateral deficit, or one with a bilateral deficit. For this purpose, a stepwise discriminant analysis was performed on measurements of head and trunk angular accelerations in addition to muscle EMG and ankle torque signals. The primary measurements selected to optimally assign a subject to a population were the periods of ankle torque and neck extensor activity associated with correcting for the imposed body displacement backwards and maintaining upright head position respectively. The resulting division into populations was 100% correct. However, within the population of unilateral deficit patients, the technique failed to correctly identify those with acute from those with compensated deficit. This technique of investigating vestibulo-spinal reflex responses is more specific and sensitive than Romberg tests, because it will quantify and specify the underlying cause of the patient's balance and ambulatory disorder.

Subclinical vestibular pathology in patients with noise-induced hearing loss from intense impulse noise

Sixty patients with varying degrees of noise-induced hearing loss (NIHL) after long-term exposure to intense impulse noise from firearms, but without manifest clinical symptoms of vestibular pathology, were tested for body sway using a stable platform. The results were compared with those from 115 healthy referents examined in the same way. Subjects with NIHL showed significantly more body sway, estimated as movement of the centre of gravity in the horizontal plane, than did the referents. Subjects with more severe NIHL showed more sway than subjects with milder acoustic trauma. The results show that body sway is increased in patients with NIHL from exposure to impulse noise of high intensity in a way suggesting an exposure-effect relationship. This suggests subclinical disturbances of the vestibular system in these patients. The underlying mechanism may be simultaneous mechanical damage to both the cochlear and vestibular partitions by intense impulse noise.

Vestibular function and motor proficiency of children with impaired hearing, or with learning disability and motor impairments

Vestibular status and motor proficiency of 30 hearing-impaired and 15 motor-impaired learning-disabled children were documented to determine whether vestibular loss can account for deficits in motor co-ordination. Vestibular loss was differentiated from sensory organization deficits by means of VOR and postural orientation test results, which were compared with those of 54 normal seven-to 12-year-olds. Reduced or absent vestibular function in 20 hearing-impaired children did not affect development of motor proficiency, except in specific balance activities. However, sensory organization deficits in the learning-disabled group and in three of the hearing-impaired children were associated with widespread deficits in motor proficiency.

Postural control in single-limb stance

Postural control in single-limb stance has previously been shown to be impaired among soccer players with functional instability (FI) of the ankle joint. The aim of the present study was to further study the role of the ankle in postural control. A dynamic method was used involving optoelectronic movement recordings of body segments and force-plate recordings of the reaction ground force. Surface electromyography was recorded for the peroneus longus muscle. Thirty physically active men were selected. Fifteen of them had FI of the ankle chosen for recording. The results show that different patterns exist for maintaining equilibrium in single-limb stance. The ankle has a central role for postural corrections. The position of center of pressure is highly correlated to the position of the ankle and peroneal muscle activity. When the body was in disequilibrium, corrections were made at the hip. It is proposed that a change from an inverted pendulum model to a multisegmental chain model takes place when adjustments at the ankle joint no longer suffice to maintain postural control. The men with FI showed impaired postural control associated with increased upper segmental corrections.

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.

Diagnosis and surgical treatment of disabling positional vertigo

This report reviews the characteristic symptoms of disabling positional vertigo (DPV), and the tests used to reach a differential diagnosis of this disorder. Twenty-one patients were operated on consecutively for management of DPV between March, 1983, and September, 1984. In all patients one or more arteries or veins was found to be compressing the eighth cranial nerve when the nerve was exposed for microvascular decompression to relieve the symptoms of DPV. After the operation, 16 of the 21 patients were free of symptoms, or symptoms were so much improved that the patients returned to normal work or social life. Two patients had no improvement and three had limited relief of symptoms postoperatively. None of the patients experienced hearing loss as a result of the operation to relieve DPV, but one patient suffered a cerebellar contusion during the operation.

Postoperative vestibular dysfunction following head and neck surgery

Patients scheduled for major oncologic head and neck surgery underwent preoperative audiometry and rotational testing for vestibulo-ocular response (VOR). Patients with normal preoperative VOR and SRT less than 45 dB were subsequently retested following surgery for VOR. Patients deemed abnormal on postoperative rotational testing were retested until VOR returned to normal or one year, whichever came first. Eighty patients had normal VOR measured preoperatively. At the first postoperative testing 46 of these patients (58%) were determined to have significant VOR abnormalities. No differences in length of anesthesia, use of hypnotic or narcotic drugs, hepatic and renal abnormalities, and dehydration were noted in the patients who developed abnormal VOR, when compared to the patients who maintained normal VOR. One year post surgery twenty patients (43%) continued to demonstrate vestibular abnormality. The observation that major surgery reduces vestibular response has important monitoring and treatment implications. The integration of this data with the results of endolymphatic surgery are discussed.

Postural disturbance in patients with benign paroxysmal positional nystagmus

Abnormal vestibular function disrupts postural and ocular muscle control system references to gravity (earth) vertical. Vestibular disorders also prevent satisfactory resolution of normally redundant, but often conflicting, visual and somatosensory spatial references required for normal postural control during active and passive body motion. Using a moving platform and visual surrounds posturography technique to systematically interact visual, somatosensory, and vestibular inputs, it was clearly demonstrated that patients with the benign paroxysmal positional nystagmus type of distorted vestibular function employ an unstable, visually dependent postural sway distinct from the postural instability associated with unilateral or bilateral vestibular functional deficits. These findings have important clinical implications for diagnosis and management of patients with vestibular disorders.

Effects of age, sex and stimulus parameters upon vestibulo-ocular responses to sinusoidal rotation

We evaluated the vestibulo-ocular reflex (VOR) in 50 normal human subjects, uniformly distributed in age 20-59 years, and evenly distributed in sex by decade, using sinusoidal rotation over the frequency range of 0.005 to 1.0 Hz and three peak amplitudes of 25, 50, and 100 deg/sec. Age variations. The gain magnitude of the normal human VOR appears to decrease with increasing age. This trend becomes statistically significant at p less than 0.05 for the 0.005 and 0.01 Hz test points. Sex-related variations. There were no statistically significant differences in gain magnitude between the sexes but females had higher average gains than males for the lowest test frequencies. The phase data showed a trend with the average phase points for females being less than those for males. This difference was statistically significant at p less than 0.05 for the 0.005 Hz test frequency. Dynamic range. Increasing the stimulus amplitude by a factor of four yielded a small but statistically significant decrease in gain magnitude, thus suggesting a mild saturation-type of nonlinearity.

Disabling positional vertigo

We have identified a group of patients with vestibular disorders whose symptoms are not consistent with the commonly recognized syndromes such as Meniere's disease, benign paroxysmal positional vertigo, and vestibular neuronitis. These patients have a constant positional vertigo and are often nauseated to an extent that makes them disabled. Their symptoms do not respond to conventional medical treatment or habituating therapy. We have found specific clinical-pathological signs in these patients that indicate that the vestibular nerve is compressed intracranially by blood vessels. Treatment of nine such patients by microvascular decompression of the eighth nerve brought total relief of symptoms in eight patients and improvement in one. We suggest that this syndrome be named disabling positional vertigo.