Sustained bias of spatial attention in a 3 T MRI scanner.

When lying inside a MRI scanner and even in the absence of any motion, the static magnetic field of MRI scanners induces a magneto-hydrodynamic stimulation of subjects' vestibular organ (MVS). MVS thereby not only causes a horizontal vestibular nystagmus but also induces a horizontal bias in spatial attention. In this study, we aimed to determine the time course of MVS-induced biases in both VOR and spatial attention inside a 3 T MRI-scanner as well as their respective aftereffects after participants left the scanner. Eye movements and overt spatial attention in a visual search task were assessed in healthy volunteers before, during, and after a one-hour MVS period. All participants exhibited a VOR inside the scanner, which declined over time but never vanished completely. Importantly, there was also an MVS-induced horizontal bias in spatial attention and exploration, which persisted throughout the entire hour within the scanner. Upon exiting the scanner, we observed aftereffects in the opposite direction manifested in both the VOR and in spatial attention, which were statistically no longer detectable after 7 min. Sustained MVS effects on spatial attention have important implications for the design and interpretation of fMRI-studies and for the development of therapeutic interventions counteracting spatial neglect.

Temporal dynamics of ocular torsion and vertical vergence during visual, vestibular, and visuovestibular rotations.

Ocular torsion and vertical divergence reflect the brain's sensorimotor integration of motion through the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) to roll rotations. Torsion and vergence however express different response patterns depending on several motion variables, but research on their temporal dynamics remains limited. This study investigated the onset times of ocular torsion (OT) and vertical vergence (VV) during visual, vestibular, and visuovestibular motion, as well as their relative decay rates following prolonged optokinetic stimulations. Temporal characteristics were retrieved from three separate investigations where the level of visual clutter and acceleration were controlled. Video eye-tracking was used to retrieve the eye-movement parameters from a total of 41 healthy participants across all trials. Ocular torsion consistently initiated earlier than vertical vergence, particularly evident under intensified visual information density, and higher clutter levels were associated with more balanced decay rates. Additionally, stimulation modality and accelerations affected the onsets of both eye movements, with visuovestibular motion triggering earlier responses compared to vestibular motion, and increased accelerations leading to earlier onsets for both movements. The present study showed that joint visuovestibular responses produced more rapid onsets, indicating a synergetic sensorimotor process. It also showed that visual content acted as a fusional force during the decay period, and imposed greater influence over the torsional onset compared to vergence. Acceleration, by contrast, did not affect the temporal relationship between the two eye movements. Altogether, these findings provide insights into the sensorimotor integration of the vestibulo-ocular and optokinetic reflex arcs.

Vertical saccades during horizontal head impulses: a sign of posterior semicircular canal hypofunction.

Objective: We describe an uncharacteristic vestibular-ocular reflex (VOR) pattern, studied by video head impulse tests (VHIT) in patients suffering from unilateral isolated posterior semicircular canal (PSC) hypofunction. In these patients, we found an upward sliding of the eyes, followed by an oblique downward catch-up saccade during horizontal head impulse to the healthy side. Methods: We present a retrospective study of all VHIT exams presenting isolated PSC hypofunction between May 2020 and November 2022. Results: We found 37 patients, which led to the discovery of such incongruent eye movement in 19 cases; their gain data are shown and compared to the remaining 18 cases in which such an anomaly was absent. A control group of 31 healthy subjects was recruited to define the reference criteria for VHIT gain values. The correlation between the amplitude of the vertical saccade and the relative functional imbalance of the vertical semicircular canals was studied. Conclusions: We have observed that in approximately half of the subjects with isolated CSP deficiency, there is a VOR anomaly. A possible pathophysiological explanation of the unbalanced effect of vertical semicircular canal stimulation of a labyrinth during horizontal head thrust toward the opposite side is proposed. The planar incongruity of the response of the VOR described here appears more evident at the onset of the CSP deficit. Current VHIT systems do not detect this incongruent eye reflex. They can lead to an error in gain evaluation (pseudo-deficit) of the lateral semicircular canal of the healthy side and problems in performing the test (trace rejected). In the future, software for VHIT should take into account the possibility of non-coplanar ocular responses to cephalic stimuli.

Differentiation of peripheral and non-peripheral etiologies in children with vertigo/dizziness: The video-head impulse test and suppression head impulse paradigm.

OBJECTIVES: To identify the etiology of vertigo/dizziness and determine the effectiveness of the video-head impulse test (vHIT) and the suppression head impulse paradigm (SHIMP) tests in distinguishing between peripheral and non-peripheral etiologies in children who presented to the otolaryngology department with complaints of vertigo/dizziness. METHODS: The vHIT and SHIMP tests were applied to the children. The vestibulo-ocular reflex (VOR) gain and saccade parameters were compared. RESULTS: In 27 children presenting with vertigo/dizziness, the most common etiological factor was inner ear malformation (IEM) (n = 6/27, 22.2%), followed by cochlear implant surgery (11.1%) and migraine (11.1%). Vestibular hypofunction was indicated by the vHIT results at a rate of 60% (9/15 children) and SHIMP results at 73.3% (11/15 children) among the children with a peripheral etiology, while these rates were 8.3% (1/12 children) and 25% (3/12 children), respectively, in the non-peripheral etiology group. SHIMP-VOR and vHIT-VOR gain values had a moderate positive correlation (p = 0.01, r = 0.349). While there were overt/covert saccades in the vHIT, anti-compensatory saccade (ACSs) were not observed in the SHIMP test (p = 0.041). The rates of abnormal vHIT-VOR gain (p = 0.001), over/covert saccades (p = 0.019), abnormal vHIT response (p = 0.014), ACSs (p = 0.001), and abnormal SHIMP response (p = 0.035) were significantly higher in the peripheral etiology group. CONCLUSIONS: IEM was the most common etiological cause, and the rate of vestibular hypofunction was higher in these children with peripheral vertigo. vHIT and SHIMP are effective and useful vestibular tests for distinguishing peripheral etiology from non-peripheral etiology in the pediatric population with vertigo/dizziness. These tests can be used together or alone, but the first choice should be the SHIMP test, considering its short application time (approximately 4-5 min) and simplicity.

Frequency dependence of human thresholds: both perceptual and vestibuloocular reflex thresholds.

Although perceptual thresholds have been widely studied, vestibuloocular reflex (VOR) thresholds have received less attention, so the relationship between VOR and perceptual thresholds remains unclear. We compared the frequency dependence of human VOR thresholds to human perceptual thresholds for yaw head rotation in both upright ("yaw rotation") and supine ("yaw tilt") positions, using the same human subjects and motion device. VOR thresholds were generally a little smaller than perceptual thresholds. We also found that horizontal VOR thresholds for both yaw rotation about an Earth-vertical axis and yaw tilt (yaw rotation about an Earth-horizontal axis) were relatively constant across four frequencies (0.2, 0.5, 1, and 2 Hz), with little difference between yaw rotation and yaw tilt VOR thresholds. For yaw tilt stimuli, perceptual thresholds were slightly lower at the lowest frequency and nearly constant at all other (higher) frequencies. However, for yaw rotation, perceptual thresholds increased significantly at the lowest frequency (0.2 Hz). We conclude 1) that VOR thresholds were relatively constant across frequency for both yaw rotation and yaw tilt, 2) that the known contributions of velocity storage to the VOR likely yielded these VOR thresholds that were similar for yaw rotation and yaw tilt for all frequencies tested, and 3) that the integration of otolith and horizontal canal signals during yaw tilt when supine contributes to stable perceptual thresholds, especially relative to the low-frequency perceptual thresholds recorded during yaw rotation.NEW & NOTEWORTHY We describe for the first time that human VOR thresholds differ from human forced-choice perceptual thresholds, with the difference especially evident at frequencies below 0.5 Hz. We also report that VOR thresholds are relatively constant across frequency for both yaw rotation and yaw tilt. These findings are consistent with the idea that high-pass filtering in cortical pathways impacts cognitive decision-making.

The headshake enhances oculomotor response to galvanic vestibular stimulation in healthy subjects.

OBJECTIVE: To investigate whether a headshake applied during galvanic vestibular stimulation (GVS) can enhance GVS-induced nystagmus in healthy subjects. METHODS: In nineteen healthy participants, we evaluated an average slow-phase velocity (aSPV) of nystagmus in a head-still and after the headshake conditions, with/out the bitemporal 2 mA GVS. The GVS was applied also with polarity congruent (supporting) or incongruent (suppressing) to any preexisting spontaneous nystagmus. RESULTS: The orientation of GVS-induced nystagmus depended on GVS polarity. In the head-still condition, the GVS-induced nystagmus in 14 subjects (74%) for congruent and in 12 subjects (63%) for incongruent GVS. During headshake, we recorded nystagmus in 16 subjects (84%) for congruent and 15 subjects (79%) for incongruent GVS. The aSPV of congruent GVS-induced nystagmus was higher (p = 0.0003) by 1.33 (SE 0.26) deg/s for headshake compared to head-still condition. The aSPV of incongruent GVS also induced higher nystagmus (p = 0.0014) by 1.24 (SE 0.28) deg/s for the headshake condition. CONCLUSION: Our study adds a new principle to the knowledge of the central processing of a GVS response in healthy subjects. The GVS-safety profile of current up to 2 mA was sufficient to elicit a significant GVS nystagmus response in a head-still position in 63% and after a headshake in 79%. Compared to the GVS head-still condition, a headshake enhanced the GVS-induced nystagmus more than twice. SIGNIFICANCE: The headshake helps to identify GVS-induced nystagmus, which can be weak or absent during the head-still condition.

PP2B-Dependent Cerebellar Plasticity Sets the Amplitude of the Vestibulo-ocular Reflex during Juvenile Development.

Throughout life, the cerebellum plays a central role in the coordination and optimization of movements, using cellular plasticity to adapt a range of behaviors. Whether these plasticity processes establish a fixed setpoint during development, or continuously adjust behaviors throughout life, is currently unclear. Here, by spatiotemporally manipulating the activity of protein phosphatase 2B (PP2B), an enzyme critical for cerebellar plasticity in male and female mice, we examined the consequences of disrupted plasticity on the performance and adaptation of the vestibulo-ocular reflex (VOR). We find that, in contrast to Purkinje cell (PC)-specific deletion starting early postnatally, acute pharmacological as well as adult-onset genetic deletion of PP2B affects all forms of VOR adaptation but not the level of VOR itself. Next, we show that PC-specific genetic deletion of PP2B in juvenile mice leads to a progressive loss of the protein PP2B and a concurrent change in the VOR, in addition to the loss of adaptive abilities. Finally, re-expressing PP2B in adult mice that lack PP2B expression from early development rescues VOR adaptation but does not affect the performance of the reflex. Together, our results indicate that chronic or acute, genetic, or pharmacological block of PP2B disrupts the adaptation of the VOR. In contrast, only the absence of plasticity during cerebellar development affects the setpoint of VOR, an effect that cannot be corrected after maturation of the cerebellum. These findings suggest that PP2B-dependent cerebellar plasticity is required during a specific period to achieve the correct setpoint of the VOR.

Pre- and post-operative semicircular canal function evaluated by video head impulse test in patients with vestibular schwannoma.

OBJECTIVES: To evaluate pre- and post-operative semicircular canal function in patients with vestibular schwannoma (VS) by the video Head Impulse Test (vHIT). METHODS: Nineteen patients with VS who underwent surgery were enrolled in this study. The gain in vestibulo-ocular reflex (VOR) and the degree of scatter in catch-up saccades were examined pre- and post-operatively for the semicircular canals in VS patients. RESULTS: Ten of 19 cases (52.6 %) with VS were defined as demonstrating both superior vestibular nerve (SVN) and inferior vestibular nerve (IVN) impairment from the results of pre-operative vHIT. Hearing level and subjective vestibular symptoms showed significant correlations with pre-operative semicircular canal function. Compared to pre-operative vHIT results, VOR gains within 1 month after surgery were significantly reduced in all three canals; however, significant differences had disappeared in the anterior and posterior semicircular canals at 6 months after surgery. Cases of unknown origin had a significantly greater reduction in posterior semicircular canal function after surgery compared with those with disease of IVN origin. CONCLUSIONS: As vHIT could evaluate pre-operative vestibular nerve impairment, post-operative VOR gain reduction and the degree of vestibular compensation, semicircular canal function evaluated by vHIT provides a good deal of useful information regarding VS patients undergoing surgery compared to caloric testing, and vHIT should be performed pre- and post-operatively for patients with VS.

Is activation of the vestibular system by electromagnetic induction a possibility in an MRI context?

In recent years, an increasing number of studies have discussed the mechanisms of vestibular activation in strong magnetic field settings such as occur in a magnetic resonance imaging scanner environment. Amid the different hypotheses, the Lorentz force explanation currently stands out as the most plausible mechanism, as evidenced by activation of the vestibulo-ocular reflex. Other hypotheses have largely been discarded. Nonetheless, both human data and computational modeling suggest that electromagnetic induction could be a valid mechanism which may coexist alongside the Lorentz force. To further investigate the induction hypothesis, we provide, herein, a first of its kind dosimetric analysis to estimate the induced electric fields at the vestibular system and compare them with what galvanic vestibular stimulation would generate. We found that electric fields strengths from induction match galvanic vestibular stimulation strengths generating vestibular responses. This review examines the evidence in support of electromagnetic induction of vestibular responses, and whether movement-induced time-varying magnetic fields should be further considered and investigated.

Assessing the synergistic effectiveness of intermittent theta burst stimulation and the vestibular ocular reflex rehabilitation protocol in the treatment of Mal de Debarquement Syndrome: a randomised controlled trial.

INTRODUCTION: Mal de Debarquement Syndrome (MdDS) is a rare central vestibular disorder characterised by a constant sensation of motion (rocking, swaying, bobbing), which typically arises after motion experiences (e.g. sea, air, and road travel), though can be triggered by non-motion events. The current standard of care is non-specific medications and interventions that only result in mild-to-moderate improvements. The vestibular ocular reflex (VOR) rehabilitation protocol, a specialised form of rehabilitation, has shown promising results in reducing symptoms amongst people with MdDS. Accumulating evidence suggests that it may be possible to augment the effects of VOR rehabilitation via non-invasive brain stimulation protocols, such as theta burst stimulation (TBS). METHODS: The aim of this randomised controlled trial was to evaluate the effectiveness of intermittent TBS (iTBS) over the dorsolateral prefrontal cortex in enhancing the effectiveness of a subsequently delivered VOR rehabilitation protocol in people with MdDS. Participants were allocated randomly to receive either Sham (n = 10) or Active (n = 10) iTBS, followed by the VOR rehabilitation protocol. Subjective outcome measures (symptom ratings and mental health scores) were collected 1 week pre-treatment and for 16 weeks post-treatment. Posturography (objective outcome) was recorded each day of the treatment week. RESULTS: Significant improvements in subjective and objective outcomes were reported across both treatment groups over time, but no between-group differences were observed. DISCUSSION: These findings support the effectiveness of the VOR rehabilitation protocol in reducing MdDS symptoms. Further research into iTBS is required to elucidate whether the treatment has a role in the management of MdDS. TRN: ACTRN12619001519145 (Date registered: 04 November 2019).

Impaired cerebellar plasticity hypersensitizes sensory reflexes in SCN2A-associated ASD.

Children diagnosed with autism spectrum disorder (ASD) commonly present with sensory hypersensitivity or abnormally strong reactions to sensory stimuli. Such hypersensitivity can be overwhelming, causing high levels of distress that contribute markedly to the negative aspects of the disorder. Here, we identify a mechanism that underlies hypersensitivity in a sensorimotor reflex found to be altered in humans and in mice with loss of function in the ASD risk-factor gene SCN2A. The cerebellum-dependent vestibulo-ocular reflex (VOR), which helps maintain one's gaze during movement, was hypersensitized due to deficits in cerebellar synaptic plasticity. Heterozygous loss of SCN2A-encoded NaV1.2 sodium channels in granule cells impaired high-frequency transmission to Purkinje cells and long-term potentiation, a form of synaptic plasticity important for modulating VOR gain. VOR plasticity could be rescued in mice via a CRISPR-activator approach that increases Scn2a expression, demonstrating that evaluation of a simple reflex can be used to assess and quantify successful therapeutic intervention.

A novel methodology to demonstrate vestibulo-ocular reflex using caloric stimulation in undergraduate physiology laboratory.

The study aims to develop a novel methodology to demonstrate the vestibulo-ocular reflex (VOR) and nystagmus by caloric stimulation in an undergraduate medical physiology laboratory. The experimental setup involved two sets of electrodes: one set positioned laterally to both eyes, and another set positioned vertically over either the right or left eye. The caloric method is used to stimulate ears, which involves irrigation of warm (44°C) and cold (30°C) water into the ears while maintaining a temperature difference of approximately ±7°C from the body temperature. The changes in chorioretinal potential were calibrated to angular displacement by a two-point calibration method, and angular velocity was derived after taking the first-time derivative. The results obtained from the digital data acquisition system were compared to the traditional instrument used in our Otorhinolaryngology Department [Interacoustics Videonystagmography (VNG) System for hospitals, medical grade] for the normal subject's data. No significant differences in angular velocity were noted (P > 0.05). The cold stimuli elicit a more pronounced VOR compared to the warm stimuli. It has been consistently observed that the onset of nystagmus occurs approximately 20 s after irrigation, reaching its peak intensity between 45 and 90 s, and gradually diminishing until it ceases after approximately 200 s. Our developed methodology enables the recording and quantification of nystagmus using easily accessible equipment. This study serves the goal of visualizing the physiological process of VOR and thereby fulfills the goal of an effective teaching tool for demonstrating to undergraduate medical students.NEW & NOTEWORTHY We developed a novel methodology to demonstrate and visualize the most common and important physiological phenomenon like the vestibulo-ocular reflex as a teaching module for undergraduate students.

[Update on central oculomotor disorders and nystagmus]. / Okulomotorikstörungen und Nystagmus.

The diagnosis of ocular motor disorders and the different forms of a nystagmus is based on a systematic clinical examination of all types of eye movements: eye position, spontaneous nystagmus, range of eye movements, smooth pursuit, saccades, gaze-holding function, vergence, optokinetic nystagmus, as well as testing of the function of the vestibulo-ocular reflex (VOR) and visual fixation suppression of the VOR. Relevant anatomical structures are the midbrain, pons, medulla, cerebellum, and cortex. There is a simple clinical rule: vertical and torsional eye movements are generated in the midbrain, horizontal in the pons. The cerebellum is relevant for almost all types of eye movements; typical pathological findings are saccadic smooth pursuit, gaze-evoked nystagmus or dysmetric saccades.Nystagmus is defined as a rhythmic, most often involuntary eye movement. It normally consists of a slow (pathological) drift of the eyes and a fast central compensatory movement of the eyes back to the primary position (re-fixation saccade). There are three major categories: first, spontaneous nystagmus, i. e. nystagmus which occurs in the gaze straight ahead position as upbeat or downbeat nystagmus; second, nystagmus that becomes visible at eccentric gaze only and third, nystagmus which can be elicited by certain maneuvers, e. g. head-shaking, head positioning, air pressure or hyperventilation, most of which are of peripheral vestibular origin. The most frequent central types of spontaneous nystagmus are downbeat and upbeat, infantile, pure torsional, pendular fixation, periodic alternating, and seesaw nystagmus. Many types of central nystagmus allow a precise neuroanatomical localization: for instance, downbeat nystagmus, which is most often caused by a bilateral floccular lesion or dysfunction, or upbeat nystagmus, which is caused by a lesion in the mesencephalon or medulla oblongata. Examples of pharmacotherapy are the use of 4-aminopyridine for downbeat and upbeat nystagmus, memantine or gabapentin for fixation pendular nystagmus or baclofen for periodic alternating nystagmus.

Catch-Up Saccades in Vestibular Hypofunction: A Contribution of the Cerebellum?

Long-term deficits of the vestibulo-ocular reflex (VOR) elicited by head rotation can be partially compensated by catch-up saccades (CuS). These saccades are initially visually guided, but their latency can greatly decrease resulting in short latency CuS (SL-CuS). It is still unclear what triggers these CuS and what are the underlying neural circuits. In this study, we aimed at evaluating the impact of cerebellar pathology on CuS by comparing their characteristics between two groups of patients with bilateral vestibular hypofunction, with or without additional cerebellar dysfunction. We recruited 12 patients with both bilateral vestibular hypofunction and cerebellar dysfunction (BVH-CD group) and 12 patients with isolated bilateral vestibular hypofunction (BVH group). Both groups were matched for age and residual VOR gain. Subjects underwent video head impulse test recording of the horizontal semicircular canals responses as well as recording of visually guided saccades in the step, gap, and overlap paradigms. Latency and gain of the different saccades were calculated. The mean age for BVH-CD and BVH was, respectively, 67.8 and 67.2 years, and the mean residual VOR gain was, respectively, 0.24 and 0.26. The mean latency of the first catch-up saccade was significantly longer for the BVH-CD group than that for the BVH group (204 ms vs 145 ms, p < 0.05). There was no significant difference in the latency of visually guided saccades between the two groups, for none of the three paradigms. The gain of covert saccades tended to be lower in the BVH-CD group than in BVH group (t test; p = 0.06). The mean gain of the 12° or 20° visually guided saccades were not different in both groups. Our results suggest that the cerebellum plays a role in the generation of compensatory SL-CuS observed in BVH patients.

Changes in vestibular-related responses to combined noisy galvanic vestibular stimulation and cerebellar transcranial direct current stimulation.

Vestibular nuclei and cerebellar function comprise vestibular neural networks that control vestibular-related responses. However, the vestibular-related responses to simultaneous stimulation of these regions are unclear. This study aimed to examine whether the combination of noisy galvanic vestibular stimulation (nGVS) and cerebellar transcranial direct current stimulation (ctDCS) using a complex transcranial electrical stimulation device alters vestibular-dominant standing stability and vestibulo-ocular reflex (VOR) function. The center of foot pressure (COP) sway and VOR of participants (28 healthy, young adults) were assessed under four conditions of transcranial electrical stimulation using nGVS and ctDCS. The COP was calculated with the participant standing on a soft-foam surface with eyes closed using a force plate to evaluate body sway. VOR measurements were collected via passive head movements and fixation on a target projected onto the front wall using a video head impulse test (vHIT). VOR gain was calculated in six directions using a semicircular canal structure based on the ratio of eye movement to head movement. The nGVS + ctDCS and nGVS + sham ctDCS conditions decreased COP sway compared to the sham nGVS + ctDCS and sham nGVS + sham ctDCS conditions. No significant differences were observed in the main effect of stimulation or the interaction of stimulation and direction on the vHIT parameters. The results of this study suggest that postural stability may be independently affected by nGVS. Our findings contribute to the basic neurological foundation for the clinical application of neurorehabilitation using transcranial electrical stimulation of the vestibular system.

Short-term learning of the vestibulo-ocular reflex induced by a custom interactive computer game.

Retinal image slip during head rotation drives motor learning in the rotational vestibulo-ocular reflex (VOR) and forms the basis of gaze-stability exercises that treat vestibular dysfunction. Clinical exercises, however, are unengaging, cannot easily be titrated to the level of impairment, and provide neither direct feedback nor tracking of the patient's adherence, performance, and progress. To address this, we have developed a custom application for VOR training based on an interactive computer game. In this study, we tested the ability of this game to induce VOR learning in individuals with normal vestibular function, and we compared the efficacy of single-step and incremental learning protocols. Eighteen participants played the game twice on different days. All participants tolerated the game and were able to complete both sessions. The game scenario incorporated a series of brief head rotations, similar to active head impulses, that were paired with a dynamic acuity task and with a visual-vestibular mismatch (VVM) intended to increase VOR gain (single-step: 300 successful trials at ×1.5 viewing; incremental: 100 trials each of ×1.13, ×1.33, and ×1.5 viewing). Overall, VOR gain increased by 15 ± 4.7% (mean ± 95% CI, P < 0.001). Gains increased similarly for active and passive head rotations, and, contrary to our hypothesis, there was little effect of the learning strategy. This study shows that an interactive computer game provides robust VOR training and has the potential to deliver effective, engaging, and trackable gaze-stability exercises to patients with a range of vestibular dysfunctions.NEW & NOTEWORTHY This study demonstrates the feasibility and efficacy of a customized computer game to induce motor learning in the high-frequency rotational vestibulo-ocular reflex. It provides a physiological basis for the deployment of this technology to clinical vestibular rehabilitation.

Application of the Barany Society's Presbyvestibulopathy Criteria in Older Adults With Chronic Dizziness.

OBJECTIVE: To evaluate the older adults with chronic dizziness using the Barany Society's presbyvestibulopathy (PVP) diagnostic criteria and to assess the clinical usability of the criteria. STUDY DESIGN: Retrospective study. SETTING: Single tertiary medical center. METHODS: Among a total of 1964 patients aged 60 years or older, 55 patients who had symptoms suitable for the PVP criteria and who underwent all 3 vestibular function tests were analyzed. Of these 55 patients, 13 patients were diagnosed with PVP based on the peripheral vestibular hypofunction criteria; the remaining 42 patients were categorized as patients without PVP. RESULTS: In both patients with PVP and patients without PVP, postural imbalance or unsteadiness was the most frequently reported vestibular symptom. The rotatory chair test contributed the most to the quantitative diagnosis of PVP (6 of 13), followed by the caloric response test (3 of 13) and video head impulse test (vHIT; 2 of 13). When we included the presence of catch-up saccades in addition to the vHIT gain in the diagnostic criteria, 5 patients without PVP were additionally diagnosed with PVP. Furthermore, when accounting for the inclusion of catch-up saccades, patients who experienced recurrent falls demonstrated a significantly higher rate of impairments in the lateral and posterior semicircular canals according to the multivariate analysis. CONCLUSION: Considering the catch-up saccades in addition to vHIT gain seemed to contribute to the diagnosis of PVP and prediction of recurrent fall risks in older adults. Further studies are needed to solidify the diagnostic criteria for PVP.

Sustained deviation of torsional eye position associated with transient semicircular canal stimulation.

BACKGROUND: Vestibular stimulation causes postural unsteadiness accompanied by a sensation of tilt. AIMS/OBJECTIVES: The mechanism of the sensation of tilt needs to be assessed by accurate calculation of the rotational axis of torsional eye position under various vestibular stimulations. MATERIAL AND METHODS: Twenty-two healthy subjects participated in the study. Thirteen subjects underwent bilateral vestibular stimulation by on-axis yaw rotation under various head positions, and eighteen subjects underwent unilateral vestibular stimulation by caloric irrigation under various head positions. Listing's Plane was plotted for the eye movement data obtained by three-dimensional video-oculography. RESULTS: The offset of Listing's Plane showed sustained deviation of torsional eye position that was more prominent in head positions that stimulated lateral semicircular canals more than vertical semicircular canals. There was a less prominent and directionally reversed offset in head positions that stimulated vertical canals more than lateral semicircular canals. CONCLUSION AND SIGNIFICANCE: The sustained torsional eye position was validated by accurate assessment using Listing's Plane. The mechanism behind the deviation may be due to a combination of multiple anatomical components within the vestibular apparatus, with potentially stronger influence from lateral semicircular canals.

Long-term dance training modifies eye-head coordination in response to passive head impulse.

Long-term dance training is known to improve postural control, especially in challenging postural tasks. However, the effect of dance training on the vestibulo-ocular reflex (VOR) has yet to be properly assessed. This study directly investigated whether VOR parameters are influenced by long-term dance training by testing dancers and controls using the video head impulse test. VOR gains using two of the most common methods (area ratio and instantaneous gains), latency and amplitude of the first saccade, if applicable, were computed. Results revealed a larger VOR gain as measured by area gain and instantaneous gain at 40 ms specifically for left-head impulses, but not right-head impulses. No significant differences in saccade frequency, amplitude, or latency were observed between groups. These differences appear to stem from a modified eye-to-head relationship during high-velocity head impulses in dancers. More specifically, the dancers' eyes lead head movement during passively applied head impulses, which result in higher VOR gain.NEW & NOTEWORTHY This study demonstrates, for the first time, that long-term dance training results in a nonlinear relationship between eye and head velocity within the first milliseconds following passive head impulse. The data also suggest a larger VOR gain in dancers. This finding suggests that dance training may modify eye-head relationship in passive high-frequency head movements. This is of particular interest for vestibular rehabilitation.