bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of the postural stability of elderly persons using time domain signal analysis
Authors: Rasku Jyrki , Pyykkö Ilmari , Juhola Martti , Garcia Melissa , Harris Tamara , Launer Lenore , Eiriksdottir Gudny , Siggeirsdottir Kristin , Jonsson Palmi , Hoffman Howard J. , Petersen Hannes , Rasmussen Cuno , Caserotti Paolo , Toppila Esko , Pajala Satu , Gudnason Vilmundur
Published: December 2019

A force platform is widely used in the evaluation of postural stability in man. Although an abundance of parameters are typically retrieved from force platform data, no uniform analysis of the data has been carried out. In general, the signal analysis does not analyze the underlying postural event, i.e., whether the signal consists of several small corrections or large excursions. In the present work, we studied the postural stability of 4589 elderly persons from Iceland on a force platform under visual and non-visual conditions during stance on a solid surface. We analyzed the internal relationship between frequently used time domain variables. In addition, we conducted a factor analysis using a subset of selected variables. Factor analysis yielded three components that can be considered different strategies for maintaining posture. In one control strategy, long swaying amplitues were pronounced, allowing the person to react when postural confidence limits are reached. In a second strategy, a high oscillation rate about the stationary point was the dominant characteristic of maintaining postural control. The third strategy appears to involve a short critical time period during which an open loop control changes into a closed loop that very rapidly controls excessive postural oscillations. The findings suggest that conventional parameters such as swaying velocity and amplitude alone do not provide sufficient information regarding a person's ability to maintain an upright stance.
Validation of centrifugation as a countermeasure for otolith deconditioning during spaceflight: Preliminary data of the ESA SPIN study1
Authors: Buytaert K.I. , MacDougall H.G. , Moore S.T. , Clement G. , Pattyn N. , Migeotte P.-F. , Wuyts F.L.
Published: December 2019

In the framework of further space exploration, countermeasures to combat the drawbacks of human space flights are essential. The present study focuses on the influence of microgravity on the otolith-ocular reflex and aims to test the hypothesis of artificial gravity being an adequate countermeasure for the deconditioning of the aforementioned reflex. The so-called SPIN study, commissioned by the European Space Agency, can be considered as a control experiment in the broad sense for the Neurolab mission (STS-90) during which 4 crewmembers of the space shuttle were subjected to in-flight centrifugation on the visual and vestibular investigation system (VVIS). After their nearly 16-day mission, they did not suffer from orthostatic intolerance and spatial disorientation. In addition, the relevant parameters of the otolith-ocular interaction remained unaffected. For this study cosmonauts from a long duration stay in the International Space Station that were not centrifuged in-flight were tested on the VVIS (1 g centripetal interaural acceleration) on 6 different days. Three measurements were taken about 1.5–2 months prior to launch and 3 were taken at 1, 4 and 9 days after return from space. Ocular counter-rolling was measured before, during and after rotation on the VVIS using infrared video goggles and compared pair wise using Friedman tests. The perception of verticality was monitored using an ultrasound system for perceptual evaluation. The preliminary results of 4 cosmonauts showed a surprisingly large inter-individual variability of the measurements. Although OCR and perception of verticality appeared to be influenced overall by the exposure to microgravity, the wide variability among the cosmonauts obscured any statistical significance, in particular due to one cosmonauts being inconsistent with the other 3. Despite the specificity of the tests under normal conditions, the diverse response to spaceflight of our subjects exposes the complexity of the peripheral and central neural adaptive processes.
Eye movements and motion perception during off-vertical axis rotation after spaceflight1
Authors: Clément Gilles , Wood Scott J.
Published: December 2019

Constant velocity off-vertical axis rotation (OVAR) provides dynamic linear acceleration stimuli that can be used to assess otolith function. Eight astronauts were rotated in darkness about their longitudinal axis 20° off vertical at low (0.125 Hz) and high (0.5 Hz) frequencies and their responses were compared before and after spaceflight. Eye movements were recorded using infrared videography and perceived motion was evaluated using a joystick with four degrees of freedom – pitch and roll tilt, front-back and lateral translation. Low-frequency OVAR generates tilt otolith-induced responses – modulation of ocular counter-roll and counter-pitch with perceived conical motion path – whereas high-frequency OVAR generates translational otolith-induced responses – modulation of horizontal and vergence slow phase velocity with perceived cylindrical motion path. While there were transient changes in the amplitude of the translational ocular responses on landing day, there were no major changes in the tilt ocular reflexes after adaptation to weightlessness. However, there was an increase in sensitivity to motion perception after spaceflight. Direct comparisons of pre- and postflight stimuli suggested that OVAR on landing day was less provocative of motion sickness than before spaceflight. These results confirm that some otolith reflexes elicited during passive motion may not be altered by short-duration spaceflight – or may readapt very quickly – and that the resolution of sensory conflict associated with postflight recovery involves higher-order neural processes.
The contribution of head position, standing surface and vision to postural control in young adults
Authors: Adamo Diane E. , Pociask Fredrick D. , Goldberg Allon
Published: December 2019

Postural control requires the integration of sensory information and is essential for performing every day movements and activities. Integrating sensory information from multiple sources may be challenging when competing sources of sensory information are affected. To further understand this complex relationship, this study investigated the contribution of varying sources of sensory information to postural control in healthy, young participants. Sixty young healthy adults (n=22 males; mean age, 24.6 ± 2.1 SD years and (n=38 females, mean age 24.0 ± 1.4 SD years) were asked to maintain a stable posture under conditions that varied standing surface, head position and the availability of visual information. Sway velocity was largest when standing on foam with eyes closed and head extended (2.07°/s) however, under the same visual-surface conditions with the head in a neutral position, sway velocity (1.59°/s) was smaller yet remained significant. Findings from this study suggest that postural sway responses are dependent on the combined integration of available sources of sensory information. It is anticipated that such baseline information will allow us to apply our findings to the clinical management of individuals suffering from balance and vestibular impairments.
The association between impaired perception of verticality and cerebral white matter lesions in the elderly patients with orthostatic hypotension
Authors: Aoki Mitsuhiro , Tanaka Kunihiko , Wakaoka Takanori , Kuze Bunya , Hayashi Hisamitsu , Mizuta Keisuke , Ito Yatsuji
Published: December 2019

Background: The morbidity of orthostatic hypotension (OH) increases with aging and the elderly often complain of dizziness associated with OH, which is implicated in white matter lesions (WMLs) on MRI. However little is known how WMLs are contributed to the development of dizziness in elderly patients. Objective: We evaluated the involvement of cerebral WMLs in the vertical perception in the elderly with OH. Methods: This study consisted of 71 dizzy patients who underwent the examinations including the Schellong orthostatic test and subjective visual vertical (SVV) test. Results: The male patients aged ⩾ 65 years with OH (1.9 ± 0.9°) showed a significantly higher magnitude of variance of SVV, which reflects an impaired vertical perception, in comparison with the male patients aged ⩾ 65 years without OH and the male patients aged < 65 years with OH (1.0 ± 0.4°, 0.9 ± 0.4°, p < 0.05). The variance of SVV significantly correlated with the volume of WMLs in both sides on MRI in the male, but not female patients (p < 0.01). Conclusions: Our results suggest that severe WMLs in the elderly with OH are involved in impaired perception of verticality, resulting in inducing subjective dizziness.
The University of California Los Angeles Dizziness Questionnaire: Advantages and disadvantages
Authors: Zur Oz , Carmeli Eli
Published: December 2019

Dizziness is one of the most troublesome symptoms of vestibular disorders, although its description remains somewhat imprecise, encompassing vertigo, lightheadedness, disequilibrium and giddiness. Symptoms include sensitivity to motion stimuli and discomfort with open spaces, such as empty streets and bridges. It is accompanied by varying degrees of anxiety and phobic behaviors. Several tools have been developed in an attempt to quantify the degree of disability, self-perceived health status and quality of life in patients with dizziness. This review focuses on the University of California, Los Angeles Dizziness Questionnaire (UCLA-DQ), which is used to assess the effect of dizziness on quality of life. This paper also includes a summary of the advantages and disadvantages of the UCLA-DQ and compares it to other instruments used to assess dizziness. In spite of a few disadvantages, we believe that this multidimensional questionnaire is an appropriate tool for evaluating patients with vestibular impairment. It should be used during the acute phase of symptoms, as well as during and after rehabilitative therapy, to assess patient improvement.
The diagnostic value of vestibular evoked myogenic potentials in patients with Meniere's disease
Authors: Egami Naoya , Ushio Munetaka , Yamasoba Tatsuya , Yamaguchi Takuhiro , Murofushi Toshihisa , Iwasaki Shinichi
Published: December 2019

Objective: To estimate the sensitivity and specificity of vestibular evoked myogenic potentials (VEMPs) in comparison with caloric test in diagnosing Meniere's disease (MD) among patients with dizziness. Methods: Data were retrospectively collected from 1,170 consecutive patients who underwent vestibular tests. Among them, 114 patients were diagnosed as having unilateral definite MD. VEMPs in response to clicks and short tone burst stimulation as well as caloric tests were performed. The sensitivity and specificity of each test were evaluated. The results of each test were compared with hearing level and staging of MD. Results: The sensitivity and specificity of VEMPs were 50.0% and 48.9%, while those of the caloric test were 37.7% and 51.2%, respectively. There was no significant difference in hearing level between patients appropriately or inappropriately identified by VEMPs, whereas there was a significant difference in those of the caloric test. Combined use of VEMP and caloric test increased the sensitivity to 65.8%. Conclusion: Although the sensitivity and specificity of VEMPs in diagnosing MD were not high, they were comparable to those of caloric test. VEMPs as well as caloric testing may give additional information as part of a diagnostic test battery for detecting vestibular abnormalities in MD.
Using core sets of the international classification of functioning, disability and health (ICF) to measure disability in vestibular disorders: Study protocol
Authors: Grill Eva , Furman Joseph M. , Alghwiri Alia A. , Müller Martin , Whitney Susan L.
Published: December 2019

Symptom frequency and severity in vestibular disorders often do not correlate well with patients' restrictions of activities of daily living and limitations of participation. Due to the lack of appropriate patient reported outcome measures (PRO), the extent of limitations and restrictions is mostly unknown. The International Classification of Functioning, Disability and Health (ICF) is a conceptual framework and classification to evaluate all aspects of health and disability. An ICF-based measure, the Vestibular and Participation Measure (VAP), was recently proposed. Also, an ICF Core Set for vertigo, dizziness and balance disorders was developed to describe what aspects of functioning should be measured. This study protocol describes the development and cross-cultural validation of a new measure, the VAP-extended (VAP-e), based on VAP and ICF Core Set on three continents. To determine objectivity and cross-cultural validity of the VAP and to find potentially redundant items, Rasch models will be used. The VAP-e will be created by modifying or adding items from the Activities and Participation and Environmental Factors component of the ICF Core Set. Reliability, objectivity and responsiveness of the VAP-e will be tested.
Increased myofiber remodelling and NFATc1-myonuclear translocation in rat postural skeletal muscle after experimental vestibular deafferentation
Authors: Luxa Nicholas , Salanova Michele , Schiffl Gudrun , Gutsmann Martina , Besnard Stéphane , Denise Pierre , Clarke Andrew , Blottner Dieter
Published: December 2019

Background: The vestibular system undergoes considerable modification during spaceflight [5]. This is paralleled by microgravity-induced muscle atrophy [6]. However, the possibility of vestibulo-autonomic regulatory mechanisms affecting skeletal muscle structure and function have not yet been addressed. Objective: We hypothesise that the vestibular system affects anti-gravitational skeletal muscle phenotype composition, size and the transcriptional factor called nuclear factor of activated T cells (NFATc1). Methods: In a laboratory study, we examined the morphological and histochemical properties including intramyocellular NFATc1 changes in slow-type soleus muscle of chemically labyrinthectomized rats (VLx; n=8) compared to a control group (Sham; n=6) after a period of one month. Results and conclusion: Neurochemical vestibular deafferentation resulted in smaller myofibre sizes, altered myofibre phenotype composition, high yields of hybrid fibre formation, and reduced myonuclear NFATc1 accumulation as signs of slow-type myofibre atrophy, myofibre type remodelling, and altered nuclear transcriptional activity in the postural soleus muscle of rats. We propose that vestibulo-autonomic modification of skeletal muscles occurs during prolonged microgravity. Our findings are likely to have implications for vestibular rehabilitation in clinical settings.
Motion sickness susceptibility in healthy subjects and vestibular patients: Effects of gender, age and trait-anxiety
Authors: Paillard A.C. , Quarck G. , Paolino F. , Denise P. , Paolino M. , Golding J.F. , Ghulyan-Bedikian V.
Published: December 2019

Several studies have suggested that anxiety may play a role in motion sickness susceptibility (MSS) variability. This study aimed to assess motion sickness susceptibility in healthy subjects and chronic vestibular patients and to investigate its relationship to gender, age and trait-anxiety. Healthy subjects (n=167) and chronic dizzy patients with various vestibulopathies (n=94), aged from 20 to 92 years old, were asked to complete Motion Sickness Susceptibility questionnaire (MSSQ) and trait-anxiety questionnaire (STAI-B). When patients were divided into those who had vestibular loss (n=51) vs. patients without vestibular loss (n=43), the MSSQ scores (mean ± SD) for patients with vestibular loss (18.8 ± 30.9) were lower than healthy subjects (36.4 ± 34.8), who were lower than vestibular patients without vestibular loss (59.0 ± 39.7). These significant differences could not be explained by gender, age, trait-anxiety, or interaction. Women had higher MSS than men, and MSS declined with age for healthy subjects and vestibular patients. The overall relationship between anxiety and MSS scores was weak and only reached significance in healthy subjects. These results support the conclusion that the vestibular system is heavily involved in MSS and that trait-anxiety may play a role in MSS but only in healthy subjects.
Mal de debarquement, motion sickness and the effect of an artificial horizon
Authors: Tal Dror , Wiener Guy , Shupak Avi
Published: December 2019

Background: Exposure to unfamiliar motion patterns commonly results in motion sickness and a false perception of motion, termed mal de debarquement, on the return to stable conditions. Objective: To investigate whether motion sickness severity is correlated with the duration and severity of mal de debarquement; to study the possible preventive effect of projecting earth-referenced scenes (an artificial horizon) during exposure to motion on the development of mal de debarquement. Methods: Thirty subjects were exposed to the recorded motion profile of a boat in a 3-degrees-of-freedom ship motion simulator. During the simulated voyage, the study participants were repeatedly put through a performance test battery and completed a motion sickness susceptibility questionnaire, while self-referenced and earth-referenced scenes were projected inside the simulator cabin. Six hours post disembarkation, subjects completed a questionnaire on mal de debarquement duration and severity. Results: Mal de debarquement, mostly of mild severity, was reported following 59% of the exposures to the provocative motion profile, and in 79% of cases lasted less than 6 hours. The incidence of mal de debarquement, its duration, and the severity of symptoms did not differ between the various artificial horizon projection modes. Significant correlations were found between motion sickness severity and the duration and severity of the mal de debarquement that followed. Conclusions: The significant correlations found between motion sickness severity and mal de debarquement duration and severity imply that both syndromes might stem from a failure to adapt to new motion conditions. There is a disparity between the previously reported reduction in motion sickness symptoms by an artificial horizon, and its failure to influence the duration and symptoms of mal de debarquement. This might be explained by the different response in the two syndromes, physical versus cognitive.
Acute VOR gain differences for outward vs. inward head impulses
Authors: Schubert Michael C. , Mantokoudis Georgios , Xie Li , Agrawal Yuri
Published: December 2019

Background: Vestibular rehabilitation is a sub-specialization within the practice of physical therapy that includes treatments designed to reduce gaze instability. Gaze stability exercises are commonly given for head rotations to the left and right, even in subjects with one healthy vestibular system (as in unilateral loss). Few studies have investigated the difference in the angular vestibular ocular reflex gain (aVOR) measured in the acute phase after deafferentation for ipsilesional head rotations that move the head away from center or towards center. Objective: The purpose of this study was to compare differences in acute aVOR gain when the head was passively rotated outward from an initially centered position (neck neutral) versus the head being rotated inward. Methods: We recorded head and eye velocity using video head impulse test equipment in patients with unilateral vestibular pathology scheduled for tumor resection via retrosigmoid approach (n=5) or labyrinthectomy due to Meniere's disease (n=2). Results: We found 1) no difference in the ipsilesional aVOR gain for inward or outward directed head impulse rotations and 2) head velocity is inversely correlated with aVOR gain for ipsilesional but not contralesional rotations. Conclusions: Bedside testing of the ipsilesional aVOR following acute vestibular ablation can be done with head impulse rotations to either side. In the acute stages, physical therapists should prescribe ipsilesional and contralesional gaze stability exercises.
Lateral canal BPPV with Pseudo-Spontaneous Nystagmus masquerading as vestibular neuritis in acute vertigo: A series of 273 cases
Authors: Asprella-Libonati Giacinto
Published: December 2019

Objective: To investigate the incidence of Lateral Semicircular Canal BPPV (LSC BPPV) with Pseudo-Spontaneous Nystagmus in patients preliminarily diagnosed for vestibular neuritis in the Emergency Department (ED). Methods: Retrospective study of 273 patients with acute vertigo and persistent horizontal nystagmus in upright position (male 110, female 163, 14–93 years old) observed over four years. All the patients were checked for any nystagmus modification by performing the Head Pitch Test (HPT) in the upright position. Results: The HPT modified the beating direction of the persistent horizontal nystagmus in 56 of the 273 examined patients. The positioning tests subsequently confirmed the diagnosis of LSC BPPV in all those 56 patients. There were 37 geotropic variants and 19 apogeotropic variants and all of them were successfully treated by performing liberatory manoeuvres in the course of the same session. Conclusion: Performing the HPT in the upright position helps to differentiate a direction fixed nystagmus from a direction changing one, and in so doing, to make the differential diagnosis between vestibular neuritis and LSC BPPV, achieving the goal of successfully treating LSC BPPV in the first session.
The first attack of Ménière's disease: A study through SVV perception, clinical and pathogenetic implications
Authors: Faralli Mario , Lapenna Ruggero , Mandalà Marco , Trabalzini Franco , Ricci Giampietro
Published: December 2019

This is a study of Subjective Visual Vertical (SVV) perception during acute attacks of Ménière's disease (MD) with comparative evaluation of concurrent nystagmus. We studied 21 patients with unilateral MD during the acute phase and 7 days later. Of the nine patients with an initial attack of MD, seven had an alteration of SVV perception and of these, three indicated a match with canal functional signs, while four patients showed an opposite trend of SVV perception relative to the spontaneous nystagmus. Nine of the 12 patients with definite MD had a pathological SVV perception always in correspondence with the same type of canal event. At 1-week control, no patient with an initial MD attack had alteration of SVV perception, whereas 5 patients with definite MD presented a pathological SVV perception toward the affected side. In the course of acute attacks of unilateral MD, clinical manifestations may include otolithic involvement and this may have an opposite trend compared to concomitant canal signs, especially during initial attacks. This behavior allows us to distinguish clinical signs of maculo-canal "correspondence" and "dissociation" with a significant prevalence of the second indication in those subjects with an initial MD attack.
The role of the thalamus in the human subcortical vestibular system1
Authors: Conrad Julian , Baier Bernhard , Dieterich Marianne
Published: December 2019

Most of our knowledge concerning central vestibular pathways is derived from animal studies while evidence of the functional importance and localization of these pathways in humans is less well defined. The termination of these pathways at the thalamic level in humans is even less known. In this review we summarize the findings concerning the central subcortical vestibular pathways in humans and the role of these structures in the central vestibular system with regard to anatomical localization and function. Also, we review the role of the thalamus in the pathogenesis of higher order sensory deficits such as spatial neglect, pusher syndrome or thalamic astasia and the correlation of these phenomena with findings of a vestibular tone imbalance at the thalamic level. By highlighting thalamic structures involved in vestibular signal processing and relating the different nomenclatures we hope to provide a base for future studies on thalamic sensory signal processing.
Less sickness with more motion and/or mental distraction
Authors: Bos Jelte E.
Published: December 2019

Background: Motion sickness may reduce passenger comfort and crew performance. Countermeasures are dominated by medication with specific and often undesirable side effects. Objective: To shown that sickness due to motion can be reduced by adding an inherent non-sickening vibration and by mental distraction. Methods: Eighteen blindfolded subjects were exposed to 20 minutes of off-vertical axis rotation (OVAR). Vibration was added by means of a head rest. Effects of OVAR and vibration were tested separately and in combination, while the subjects were performing an audio letter memorising task. This task was absent to test the effect of mental distraction. Effects were quantified by rating subjective misery and objective task performance. Results: Sixteen subjects completed the experiment and showed in mutual comparable conditions that head vibration reduced the amount of sickness by 25%, the mental distraction did so by 19%, and the combined effect resulted in a reduction of 39%. Their task performance decreased with increasing sickness. Conclusion: Sickness due to low-frequency motion can be reduced by adding a high-frequency vibration and by mental distraction. The effect of vibration can be understood by assuming an internal model used by the central nervous system to optimise the control of body motion.
Susceptibility to motion sickness is not increased following spinal cord injury
Authors: Macefield Vaughan G. , Walton Darren K.
Published: December 2019

Background: There are two leading theories on the origin of motion sickness. One, the sensory conflict theory, states that sensory information provided by one sensory channel does not match the expected input from another channel; commonly, these two inputs originate in the vestibular system and the eyes. The second theory – the postural instability theory – states that motion sickness comes about not through sensory conflict, but through an inability to control one’s posture. Objective: Given that people with a motor-complete spinal cord injury cannot control their muscles below the level of the spinal lesion, we predicted that susceptibility to motion sickness would be higher in individuals who have suffered a spinal cord injury. Methods: Twenty-one people living with chronic spinal cord injury (9 quadriplegics, 12 paraplegics) completed the Motion Sickness Susceptibility Questionnaire (MSSQ), via an online survey, to compare susceptibility to motion sickness before and after injury. Results: Spinal cord injury, regardless of level, did not produce an increase in susceptibility to motion sickness. Conclusion: We have tested the general validity of the postural-instability theory by assessing susceptibility to motion sickness in individuals with spinal cord injury. Despite the loss of postural control, there was no increase in motion sickness susceptibility.
Comparison of Horizontal Head Movements Evoked by Auditory and Visual Targets
Authors: Fuller James H.
Published: December 2019

Head movement propensity – the pattern of head saccades dependent on methods of target presentation – varies among individuals. The present group of 9 young adults was previously ranked in a visual saccadic task according to this propensity. The present report examines how and why this propensity changes if the saccades are made to auditory targets. 1) Spatially identical, interleaved, auditorily and visually elicited horizontal saccadic gaze shifts (jumps) differed in amplitude and in starting and/or ending position. The jumps were executed in two head movement modes: first, the non-aligned mode was a standard reaction-time single gaze step between two points. Second, the head-aligned mode required alignment of the head with the fixation (starting) point; thereafter both modes were identical. All results in the auditory task are expressed relative to the visual results. 2) In the non-aligned mode, head movement amplitudes were increased on average by 15% (for example, an 80° jump elicited a 12° larger head movement), and velocity decreased by 12%, reflecting the increased demands of the auditory task. More importantly, the differences between subjects was narrowed; that is, head movement propensity was homogenized in the auditory task. In the visual task, head-movers willingly move their heads off and across the midline, whereas non-movers are unwilling to leave the midline from eccentric starting points or to eccentric ending points. This is called the midline attraction effect and was previously linked to spatial reference frames. The homogenization in the auditory task was characterized by head-movers increasing, and non-movers decreasing, their midline attraction, suggesting altered spatial reference frames. 3) For heuristic purposes, the ideal head-mover is defined by a gain of 1.0 in the visual task, and by external earth-fixed reference frames. Similarly, the ideal non-mover has a gain of 0.0 and has a bias toward body (or some part of the body)-fixed reference frames. In the auditory task these gains (and reference frames) in head-movers and non-movers are homogenized (closer to 0.5), either by the participation of the head (movement of the ears in space) in sensory acquisition or by differences in central nervous processing of the two modalities, or both.
Vertigo After Sailing a Nineteenth Century Ship
Authors: Cohen Helen
Published: December 2019

Few papers describe illusions of motion after sailing for which subjects do not seek medical assistance. After sailing on a square-rigged ship for five-hour periods subjects were surveyed about the incidence, intensity, and quality of such illusions. Even on a calm day, 20% to 41% of the crew experienced post-sailing vertigo, but it only occurred among the nonprofessional sailors. This phenomenon is characterized by extinction with repeated exposure, a lag time to onset of about two hours, brief duration, and occurrence in enclosed visual surrounds. These data are similar to vestibular habituation and suggest that some central vestibular mechanisms may be involved.
Tilt Suppression, OKAN, and Head-Shaking Nystagmus at Long-Term Follow-Up After Unilateral Vestibular Neurectomy1
Authors: Brantberg K. , Fransson P.-A. , Bergenius J. , Tribukait A.
Published: December 2019

The functional status of the velocity storage mechanism was studied in patients at long-term follow-up (2 to 4 years) after unilateral vestibular neurectomy. The time constant of the vestibulo-ocular reflex (VORtc), the effect of head tilt on postrotatory nystagmus, optokinetic after-nystagmus (OKAN), and nystagmus after rapid head shaking were studied in 10 patients. In agreement with previous findings, VORtc was found to be short and most patients manifested OKAN, suggesting that unilateral peripheral vestibular loss is associated with a complete loss of storage within the the VOR but only a partial loss of velocity storage for visual input. However, at postrotatory head tilt the VOR time constant was further shortened, supposedly due to discharge of functioning velocity storage. Moreover, most patients manifested nystagmus after head shaking. These findings on tilt suppression and head-shaking nystagmus suggest that velocity storage within the VOR may function even in patients with complete unilateral vestibular lesions.
Functional Reach and Single Leg Stance in Patients with Peripheral Vestibular Disorders
Authors: Mann Gwendolyn C. , Whitney Susan L. , Redfern Mark S. , Borello-France Diane F. , Furmant Joseph M.
Published: December 2019

The purpose of this study was to compare functional reach distance and right single leg stance time in patients who had peripheral vestibular disease. Twenty-eight patients (15 female, 13 male) between the ages of 35 and 84 were asked to perform 3 trials each of functional reach (FR) and right single leg stance (SLS). SLS times were measured by a Kistler static force platform on line with a Caspar personal computer. FR distance was measured by using a free-standing 147-cm rule. In addition, each subject filled out the Dizziness Handicap Inventory (DHI). Trials were randomized to prevent fatigue or practice effects. A Pearson product-moment correlation was performed between FR and SLS (r=0.59, P=0.001), Post hoc analyses of the first, the best, and the average scores highlighted the importance of using means for comparison in a population as variable as the vestibularly impaired. Post hoc analyses showed no correlation between the DHI score and either functional reach distance or single leg stance time. However, when the subjects were divided into groups based on DHI score (group 1 with DHI≤49/100, group 2 with DHI≥50/100) and a pooled two-sample t-test was performed, a significant difference (P=0.05) was found in functional reach distance; the subjects who reported less perception of handicap reached farther than those who reported more perception of handicap. No difference was found between the two DHI groups in single leg stance time. Post hoc correlations of functional reach and single leg stance time. Post hoc correlations of functional reach and single leg stance within the two DHI groups showed a higher correlation in group 1 (DHI≤49/100), with r equals 0.65(P≤0.01), than in group 2 (DHI≥50/100), with r equals 0.38 (P=0.20). The study found a highly significant, moderate correlation between functional reach distance and single leg stance times in patients with peripheral vestibular disease. These results support the use of FR as an additional assessment tool with patients who have peripheral vestibular disease.
“Torso Rotation” Experiments; 1: Adaptation to Motion Sickness does not Correlate with Changes in VOR Gain
Authors: Bouyer L.J.G. , Watt D.G.D.
Published: December 2019

Following a 30-minute exposure to an unusual motor strategy called “Torso Rotation” (TR), the signs and symptoms of motion sickness appear along with perceptual illusions during movement, gaze and postural instability, and a significantly reduced vestibulo-ocular response (VOR) gain. With repeated exposure to TR, the motion sickness disappears and gaze instability seems to be reduced. Is this apparent improvement in gaze stability associated with a reduction of the transient change in VOR gain? Motion sickness (subjective questionnaire) and VOR gain (passive step rotations in darkness) were measured before and repeatedly after TR on 7 consecutive days. Despite a complete loss of symptoms in 3 to 4 days, the transient, daily change in VOR gain remained unaffected. Furthermore, there was no increase in the use of compensatory saccades. It is concluded that adaptation to TR-induced motion sickness is not the result of a change in VOR's sensitivity to TR.
Visual Influence on Head Shaking Using the Vestibular Autorotation Test1
Authors: Cheung Bob , Money Ken , Sarkar Paul
Published: December 2019

In this study we investigated the vestibular system by recording eye movements in response to voluntary high-frequency head-only movements using the Vestibular Autorotation Test (VAT; Western System Research Inc., Los Angeles, California). Our objective was to evaluate if the VAT could be implemented as one of the screening tests for vestibular integrity in aircrews and potential pilots. We attempted to record horizontal and vertical eye movements using electrooculography and head velocity with calibrated rotational velocity sensors. The gain and phase of the input and output signals were computed by discrete Fourier analysis. Seated subjects were instructed to fixate on a real or imaginary target while making smooth head oscillations about the spinal axis in time to an audible cue from 0.5 to 6.0 Hz during an 18-second test period. Test trials included two conditions in the light with subjects fixated on a real target (C1) or on an imaginary target on a blank screen (C2); three conditions in the dark in which subjects fixated on an imaginary target (C3), fixated on a remembered LED target in the dark after it was extinguished (C4), or fixated on a real target (C5). All the dark trials were performed after dark adaptation for 30 minutes. We were not able to obtain consistent vertical VOR response (when the subjects oscillated their head about the interaural axis) using the VAT. For horizontal eye movements from 2.0 to just over 4.7 Hz, when subjects fixated on an imaginary target, there was an unexpected and significant increase in the gain of the eye movement velocities in the dark as compared to the gain obtained in the light conditions. In the dark trials, the gain was significantly higher when the subjects fixated on an imaginary target as opposed to a real target. There was no difference in phase among all conditions. This test could potentially serve for preliminary screening for the integrity of the vestibular system as it is noninvasive and of short duration. However, caution must be exercised in controlling various variables. Extensive normative data are needed to properly assess this test as a screening tool for aircrews.
Treatment of Horizontal Semicircular Canal Benign Paroxysmal Positional Vertigo
Authors: Vannucchi P. , Giannoni B. , Pagnini P.
Published: December 2019

We evaluated a new therapeutic maneuver-Prolonged Position on the healthy side, for Benign Paroxysmal Positional Vertigo (BPPV) of the horizontal semicircular canal. We devised this type of physical treatment in accordance with the “canalolithiasis” theory of BPPV, in order to try to free the horizontal semicircular canal of otoconial debris. We compared the results obtained by Prolonged Position with two other physical therapies by dividing our horizontal canal BPPV patients into three therapeutic groups: 1) 35 patients treated with Prolonged Position; 2) 24 patients treated with head shaking in a supine position; 3) 15 patients for whom therapy was omitted. More than 90% of the patients treated with Prolonged Position recovered within 3 days, although 6 patients out of 35 subsequently developed BPPV of the posterior semicircular canal, which then responded well to a particular repositioning maneuver. The results of Prolonged Position were significantly better than those obtained by performing head shaking or by omitting treatment. Prolonged Position can be applied to patients of all ages and general conditions and does not require hospitalization.
Neuroanatomic Substrates for Vestibulo-Autonomic Interactions
Authors: Balaban Carey D. , Porter Jennifer D.
Published: December 2019

Recent anatomical studies have identified a network of central neural circuits that appear to integrate vestibular and autonomic information. Like vestibulo-ocular and vestibulospinal circuits, these pathways appear to be under inhibitory modulation by distinct regions in the medial aspect of the cerebellar cortex. These central circuits have the potential to explain the known influence of vestibular stimulation on autonomic motor responses through descending effects on brain stem autonomic regions. In a more global context, the extensive convergence of vestibular and autonomic information in both vestibular and autonomic brain regions is consistent with the concept that vestibular and visceral information (for example, blood pooling and visceral proprioception) are used to form a central representation of gravitoinertial parameters during movements. This representation can influence neural circuitry involved in postural control, cardiovascular control, perception of the spatial vertical and emotional or affective responses.
Vestibular Influences on Autonomic Cardiovascular Control in Humans
Authors: Biaggioni Italo , Costa Fernando , Kaufmann Horacio
Published: December 2019

There is substantial evidence that anatomical connections exist between vestibular and autonomic nuclei. Animal studies have shown functional interactions between the vestibular and autonomic systems. The nature of these interactions, however, is complex and has not been fully defined. Vestibular stimulation has been consistently found to reduce blood pressure in animals. Given the potential interaction between vestibular and autonomic pathways this finding could be explained by a reduction in sympathetic activity. However, rather than sympathetic inhibition, vestibular stimulation has consistently been shown to increase sympathetic outflow in cardiac and splanchnic vascular beds in most experimental models. Several clinical observations suggest that a link between vestibular and autonomic systems may also exist in humans. However, direct evidence for vestibular/autonomic interactions in humans is sparse. Motion sickness has been found to induce forearm vasodilation and reduce baro-reflex gain, and head down neck flexion induces transient forearm and calf vasoconstriction. On the other hand, studies using optokinetic stimulation have found either very small, variable, or inconsistent changes in heart rate and blood pressure, despite substantial symptoms of motion sickness. Furthermore, caloric stimulation severe enough to produce nystagmus, dizziness, and nausea had no effect on sympathetic nerve activity measured directly with microneurography. No effect was observed on heart rate, blood pressure, or plasma norepinephrine. Several factors may explain the apparent discordance of these results, but more research is needed before we can define the potential importance of vestibular input to cardiovascular regulation and orthostatic tolerance in humans.
Neural Control of the Cardiovascular System During Exercise
Authors: Kramer Jeffery M. , Waldrop Tony G.
Published: December 2019

Precise regulatory signals are required in order to adjust the cardiovascular and respiratory systems to meet the demands of exercise. Two neural mechanisms, central command and a reflex originating in contracting muscles, are known to play a large role in exercise-associated adjustments in cardiovascular and respiratory activity. The extent to which other regulatory reflexes, such as vestibulo-autonomic reflexes, are able to impact upon the cardiovascular and respiratory systems during exercise is largely unknown. Further, brain regions that may integrate these control mechanisms are only starting to be investigated. We propose that medullary brain nuclei may integrate both exercise and vestibular signals to produce a more coordinated, and therefore efficient, means of adaptation to exercise in a gravitational environment.
Further Evidence for Gender Differences in Circularvection
Authors: Darlington Cynthia L. , Smith Paul F.
Published: December 2019

This paper reports further evidence that gender is a significant factor in the experience of circularvection (CV), the illusion of self-rotation. Using optokinetic drum velocities between 24° and 92°/s, latency to experience Stage 2 or Stage 3 CV was measured. Males exhibited significantly longer CV latencies than females (P < 0.0001), although the difference was greater for Stage 3 CV than for Stage 2 CV. This result suggests that the potential influence of gender must be carefully controlled in visual–vestibular interaction experiments.
Comparison of Manual Whole-Body and Passive and Active Head-On-Body Rotational Testing with Conventional Rotary Chair Testing
Authors: Hanson Jason M. , Goebel Joel A.
Published: December 2019

New methods of rotational testing of the vestibulo-ocular reflex (VOR) using manually generated or patient-generated sinusoidal head movements have recently been advocated for clinical use in circumstances where conventional rotary chair testing methods are not feasible. However, studies seeking to provide evidence for the validity of these methods by comparing their results with an accepted “gold-standard” have been conspicuously absent in the literature. In this study, we compared results for VOR gain, phase, and asymmetry obtained using whole-body and head-on-body rotational stimuli with those obtained by conventional rotary chair testing in 35 subjects with either unilateral or bilateral vestibular deficits over the range of frequencies from 0.025 Hz to 1 Hz. Our results provide evidence for the validity of manual whole-body and active and passive head-on-body rotational testing methods by demonstrating excellent agreement between each of these and conventional rotational chair testing for VOR gain, phase, and asymmetry within the frequency range studied. Small differences at specific-paradigm datapoints are likely secondary to subtle limitations of our experimental design. With further refinement, we expect the new methods will be useful adjuncts for evaluating patients with vestibular complaints in selected clinical situations.
The Effect of Head-To-Trunk Position on the Direction of Arm Movements Before, During, and After Space Flight
Authors: Berger Meinhard , Lechner-Steinleitner Silvia , Kozlovskaya Inessa , Holzmüller Gerhard , Mescheriakov Sergei , Sokolov Alexej , Gerstenbrand Franz
Published: December 2019

This contribution deals with the examination of the consequences of different head-to-trunk positions on arm movements under normal gravity and during prolonged space flight. One of the objectives of this study was to investigate the influence of weightlessness on the condition of the spatial analysis system. Aimed arm movements in the horizontal plane (pointings towards two visual targets) were recorded, first with eyes open, head straight (learning part), then with eyes closed, head straight and during yaw or roll position of the head (performance part). Measurements related to these different head-to-trunk-positions were taken in one short-term and nine long-term cosmonauts preflight, inflight, and postflight. Terrestrial control experiments were carried out with an extended experimental design in 14 healthy volunteers. The analysis of these experiments revealed that, with eyes closed and the head in yaw position, cosmonauts before flight and control subjects exhibit significant slants of the movement plane of the arm. Contrary to terrestrial measurements, in space experiments roll tilt of the head to the right is correlated with considerable counterclockwise slant of the movement plane. This slant of the movement plane of the arm was interpreted as tilt of the internal representation of the horizontal coordinate. The effect is larger with greater distortion induced by the changed head position and with larger muscular involvement to keep this position. This effect is also increased by the reduction of information (for example, in microgravity). The amount and the direction of the horizontal offset of the arm movements are shown to be dependent on the head-to-trunk position, too. Additionally, we have found changes in the amplitude and in the duration of the arm movement, in the vertical offset, and in the curvature of the movement paths, depending on the experimental conditions.