Vestibular-ocular Reflex Gain Research Articles

Concurrent vestibular activation and postural training recalibrate somatosensory, vestibular and gaze stabilization processes.

Postural instability is a common symptom of vestibular dysfunction that impacts a person's day-to-day activities. Vestibular rehabilitation is effective in decreasing dizziness, visual symptoms and improving postural control through several mechanisms including sensory reweighting of the vestibular, visual and somatosensory systems. As part of the sensory reweighting mechanisms, vestibular activation exercises with headshaking influence vestibular-ocular reflex (VOR). However, combining challenging vestibular and postural tasks to facilitate more effective rehabilitation outcomes is under-utilized. Understanding how and why this may work is unknown. The aim of the study was to assess sensory reweighting of postural control processing and VOR after concurrent vestibular activation and weight shift training (WST) in healthy young adults. Forty-two participants (18-35years) were randomly assigned into four groups: No training/control (CTL), a novel visual feedback WST coupled with a concurrent, rhythmic active horizontal or vertical headshake activity (HHS and VHS), or the same WST with no headshake (NHS). Training was performed for five days. All groups performed baseline- and post-assessments using the video head impulse test, sensory organization test, force platform rotations and electro-oculography. Significantly decreased horizontal eye movement variability in the HHS group compared to the other groups suggests improved gaze stabilization (p = .024). Significantly decreased horizontal VOR gain (p = .040) and somatosensory downweighting (p = .050) were found in the combined headshake groups (HHS and VHS) compared to the other two groups (NHS and CTL). The training also showed a significantly faster automatic postural response (p = .003) with improved flexibility (p = .010) in the headshake groups. The concurrent training influences oculomotor function and suggests improved gaze stabilization through vestibular recalibration due to adaptation and possibly habituation. The novel protocol could be modified into progressive functional activities that would incorporate gaze stabilization exercises. The findings may have implications for future development of vestibular rehabilitation protocols.

Altered Oculomotor and Vestibulo-ocular Function in Children and Adolescents Postconcussion.

To document (1) oculomotor (OM) and vestibulo-ocular (VO) function in children with concussion who were symptomatic at the time of assessment and to compare it with that in children with concussion who were clinically recovered (asymptomatic) and in children with no concussive injury, and (2) the extent to which OM and VO function relates to postconcussion symptom severity in injured children. Participants were recruited from a concussion clinic or the community. A total of 108 youth with concussion (72 symptomatic; 36 recovered) and 79 healthy youth (aged 9-18 years). Youth with concussion were included if aged 9 to 18 years, had no previous concussion within the last 12 months, less than 90 days since injury, and no known existing visual disorders or learning disabilities. A prospective cross-sectional study. All participants were tested for OM and VO function with a commercial virtual reality (VR) eye-tracking system (Neuroflex®, Montreal,Québec, Canada). Participants in the concussion group who completed the postconcussion symptoms were scored with the Post-Concussion Symptom Inventory. There was a significant group effect for vergence during smooth pursuit (F2,176 = 10.90; P < .05), mean latency during saccades (F2,171 = 5.99; P = .003), and mean response delay during antisaccades (F2,177 = 9.07; P < .05), where children with symptomatic concussion showed poorer performance than clinically recovered and healthy children. Similar results were found in VO for average vestibular ocular reflex gain in the horizontal leftward (F2,168 = 7; P = .001) and rightward directions (F2,163 = 13.08; P < .05) and vertical upward (F2,147 = 7.60; P = .001) and downward directions (F2,144 = 13.70; P < .05). Mean saccade error was positively correlated to total Post-Concussion Symptom Inventory scores in younger clinically recovered children. VR eye tracking may be an effective tool for identifying OM and VO deficits in the subacute phase (<90 days) postconcussion.

Influence of Age and Cardiovascular Risk Factors in Vestibular Neuritis: Retrospective Cohort Study.

Retrospective cohort study. VN-diagnosed patients were included and divided into two groups: those with and without CVRFs. We analyzed the mean vestibular-ocular reflex (VOR) gain, measured through the video head impulse test (vHIT) at the diagnosis and one-year follow-up. We conducted a factorial analysis of variance (ANOVA) to evaluate the effect of age, sex, and CVRFs in the mean VOR gain. Sixty-three VN-diagnosed patients were included. There were no statistically significant differences in the mean VOR gain between both groups. However, in the subgroup analysis, there were statistically significant differences when comparing the mean VOR gain at the one-year follow-up between the group over 55 years of age 0.77 ± 0.20 and the group under 55 years 0.87 ± 0.15 (p = 0.036). Additionally, the factorial ANOVA demonstrated a significant main effect of age group on the mean VOR gain at the one-year follow-up (p = 0.018), and it also found a significant interaction between the factors of gender, age group, HTN (p = 0.043). CVRFs do not independently affect the mean VOR gain in VN patients' follow-ups. However, age significantly impacts VOR gain in VN and could be modulated by gender and hypertension.

Quantitative vestibular assessment: The development and validation of a novel, remote video head impulse test against in-clinic measurements.

To develop a novel remote head impulse test (rHIT), and to provide preliminary data validating the rHIT vestibular-ocular reflex (VOR) gains against the in-clinic vHIT. A convenience sample of 10 patients referred for vestibular assessment at our institution was recruited. In-clinic vHIT was used to quantify lateral VOR gains. Patients subsequently underwent an rHIT protocol, whereby patients performed active, lateral head rotations while their eyes and heads were recorded using a laptop camera and video-conferencing software. The vHIT and rHIT VOR gains were compared using paired t-tests, and a Pearson correlation coefficient between the gains was calculated. Absolute accuracy, sensitivity, and specificity of the rHIT were additionally calculated. Of the 10 patients recruited, 4 were male, and the average ± standard deviation (SD) age was 61.4 ± 15.3 years. As determined by the vHIT, 2 patients had normal bilateral VOR gains, 6 with unilateral vestibular hypofunction, and 2 with bilateral vestibular hypofunction. The correlation between the rHIT and vHIT gains was 0.73 (p < .001). The rHIT exhibited an absolute accuracy of 75.0%, sensitivity of 70.0%, and specificity of 80.0%. When ears had a vHIT VOR gain less than 0.40, the rHIT exhibited 100.0% accuracy. Conversely, 60.0% of deficient ears with vHIT VOR gains greater than 0.40 were incorrectly categorized by the rHIT. The rHIT may be better suited for detecting more severe vestibular deficiencies. Future iterations of the rHIT should aim to increase the video frame-rate capabilities to detect subtler VOR impairments. 4.

Correlation between nystagmus intensity and vestibular-ocular reflex gain in benign paroxysmal positional vertigo: A prospective, clinical study.

Video head impulse test (vHIT) and videonystagmography (VNG) provide significant benefits in evaluating benign paroxysmal positional vertigo (BPPV) and determining the semicircular canal localization of the otoconia. This study aimed to investigate the relationship between vestibular-ocular reflex (VOR) gains measured via vHIT and the slow-phase velocity (SPV) of nystagmus in patients with the posterior semicircular canal (PSCC)-BPPV. Sixty-two patients were included in this study and divided into the study (n = 32, patients with isolated PSCC-BPPV) and control (n = 30, age- and sex-matched healthy individuals) groups. While VOR gains were measured with vHIT in both groups and compared between groups, the SPV values of nystagmus observed during the Dix-Hallpike maneuver in the study group were recorded using VNG and compared with the VOR gains of the study group. There were significant differences in posterior canal VOR gains between the study and control groups (p < 0.001 and p < 0.01, respectively). Although the affected PSCC had decreased VOR gains versus the control group, it was still within the normal range. However, there was no significant relationship between the VOR gains of the affected PSCC and the SPV of the nystagmus. vHIT can help detect semicircular canal dysfunction in patients with PSCC-BPPV. The SPV values of nystagmus on VNG during the Dix-Hallpike maneuver do not correlate with the level of VOR gain.

Patterns of vestibular function in patients with dizziness after COVID-19 vaccination; dual tertiary referral center study

Background Although dizziness is a common symptom after vaccination, the mechanism, and prognosis are not well understood. Aims/Objectives This study aimed to investigate patients with dizziness after COVID-19 vaccination by analyzing objective information. Methods A retrospective study of patients who visited the outpatient clinics of two institutes with a complaint of dizziness occurring within 72 h after a COVID-19 vaccination. Results In most cases, patients experienced only a single event of dizziness, and the subjective symptom was relieved after a few weeks. All patients decreased gain of vestibular ocular reflex (VOR). The vestibular function test results showed signs of central vestibulopathy in some cases. We separated patients into two groups; the direction-fixed nystagmus (DFN) group and the direction-changing nystagmus (DCN) group. All patients showed decreased gain on the rotational chair test (RCT). The DFN group showed an 80% decrease in video head impulse test (vHIT) gain, whereas the DCN group only showed a decrease of 25%. In RCT, 66% of the DFN group showed asymmetry compared to 20% showing asymmetry in the DCN group. Conclusion and significance The patients who suffered from dizziness after the COVID-19 vaccination exhibited decreased VOR gain and in some cases signs of central vestibulopathy.

Artificial intelligence for early stroke diagnosis in acute vestibular syndrome.

ObjectiveMeasuring the Vestibular-Ocular-Reflex (VOR) gains with the video head impulse test (vHIT) allows for accurate discrimination between peripheral and central causes of acute vestibular syndrome (AVS). In this study, we sought to investigate whether the accuracy of artificial intelligence (AI) based vestibular stroke classification applied in unprocessed vHIT data is comparable to VOR gain classification.MethodsWe performed a prospective study from July 2015 until April 2020 on all patients presenting at the emergency department (ED) with signs of an AVS. The patients underwent vHIT followed by a delayed MRI, which served as a gold standard for stroke confirmation. The MRI ground truth labels were then applied to train a recurrent neural network (long short-term memory architecture) that used eye- and head velocity time series extracted from the vHIT examinations.ResultsWe assessed 57 AVS patients, 39 acute unilateral vestibulopathy patients (AUVP) and 18 stroke patients. The overall sensitivity, specificity and accuracy for detecting stroke with a VOR gain cut-off of 0.57 was 88.8, 92.3, and 91.2%, respectively. The trained neural network was able to classify strokes with a sensitivity of 87.7%, a specificity of 88.4%, and an accuracy of 87.9% based on the unprocessed vHIT data. The accuracy of these two methods was not significantly different (p = 0.09).ConclusionAI can accurately diagnose a vestibular stroke by using unprocessed vHIT time series. The quantification of eye- and head movements with the use of machine learning and AI can serve in the future for an automated diagnosis in ED patients with acute dizziness. The application of different neural network architectures can potentially further improve performance and enable direct inference from raw video recordings.

Report of oscillopsia in ataxia patients correlates with activity, not vestibular ocular reflex gain

Patients with cerebellar ataxia report oscillopsia, "bouncy vision" during activity, yet little is known how this impacts daily function. The purpose of this study was to quantify the magnitude of oscillopsia and investigate its relation to vestibulo-ocular reflex (VOR) function and daily activity in cerebellar ataxia. 19 patients diagnosed with cerebellar ataxia and reports of oscillopsia with activity were examined using the video head impulse test (vHIT), Oscillopsia Functional Index (OFI), and clinical gait measures. Video head impulse data was compared against 40 healthy controls. OFI scores in ataxia patients were severe and inversely correlated with gait velocity (r = -0.55, p < 0.05), but did not correlate with VOR gains. The mean VOR gain in the ataxic patients was significantly reduced and more varied compared with healthy controls. All patients had abnormal VOR gains and eye/head movement patterns in at least one semicircular canal during VHIT with passive head rotation. Patients with cerebellar ataxia and oscillopsia have impaired VOR gains, yet severity of oscillopsia and VOR gains are not correlated. Patients with cerebellar ataxia have abnormal oculomotor behavior during passive head rotation that is correlated with gait velocity, but not magnitude of oscillopsia.

Video head impulse testing to differentiate vestibular neuritis from posterior circulation stroke in the emergency department: a prospective observational study

Background and aimsVertigo is a common presentation to the emergency department (ED) with 5% of presentations due to posterior circulation stroke (PCS). Bedside investigations such as the head impulse test...

Skill-Related Adaptive Modifications of Gaze Stabilization in Elite and Non-Elite Athletes.

The vestibular ocular reflex (VOR) provides gaze stability during head movements by driving eye movements in a direction opposing head motion. Although vestibular-based rehabilitation strategies are available, it is still unclear whether VOR can be modulated by training. By examining adaptations in gaze stabilization mechanisms in a population with distinct visuomotor requirements for task success (i.e., gymnasts), this study was designed to determine whether experience level (as a proxy of training potential) was associated with gaze stabilization modifications during fixed target (VOR promoting) and fixed-to-head-movement target (VOR suppressing) tasks. Thirteen gymnasts of different skill levels participated in VOR and VOR suppression tasks. The gain between head and eye movements was calculated and compared between skill levels using an analysis of covariance. Across experience levels, there was a similar degradation in VOR gain away from −1 at higher movement speeds. However, during the suppression tasks, more experienced participants were able to maintain VOR gain closer to 0 across movement speeds, whereas novice participants showed greater variability in task execution regardless of movement speed. Changes in adaptive modifications to gaze stability associated with experience level suggest that the mechanisms impacting gaze stabilization can be manipulated through training.

Video Head Impulse Test in Persons with Blindness: Feasibility and Outcomes

To achieve balance, persons with blindness (PWB) use proprioceptive and vestibular cues rather than the visual system; however, PWB are equally susceptible to acquire vestibular disorders. Reliable assessments of the vestibular system in PWB are essential to determine the presence or absence of vestibular disorders. The saccular and the utricular functioning can be assessed using cervical vestibular-evoked myogenic potential and ocular vestibular-evoked myogenic potential, respectively. Evaluation of the functional integrity of the semicircular canals requires an assessment of the vestibular ocular reflex; however, this can be challenging in PWB. Video head impulse test (vHIT) assesses the vestibular ocular reflex (VOR) elicited against the natural high-frequency head movement in the planes of all six semicircular canals. This study aimed to explore the feasibility and outcomes of administering vHIT in PWB. Standard (static) groups comparison. Nineteen young PWB and 23 age-matched adults with "normal" vision (control group) were included in the study. PWB underwent vHIT once, while the control group was tested in three conditions; condition 1 was used to simulate blindness for the control group, where vHIT was done in a pitch-dark room without prior instructions; condition 2 included vHIT testing in daylight, without a fixed visual target and any instructions; and condition 3 involved vHIT in daylight in the presence of a set visual target and with standard instructions to maintain visual focus on the visual target. The VOR gain was abnormal in the PWB group for all the canals. Among the PWB, the lateral canals (mean = 0.63) had the best VOR gain, followed by the anterior canals (mean = 0.53) and the posterior canals (mean = 0.31). In the control group, the VOR gain was significantly reduced in condition 1. There was no significant difference between the VOR gain in the PWB group and the control group in condition 1 for the lateral and the anterior canals. A higher proportion of participants in the PWB group had the presence of refixation saccades. VOR is significantly reduced in PWB but not completely absent. There may be a need to develop normative data for blind individuals to decide whether or not a person with blindness has a vestibular dysfunction, specifically a VOR deficit.

Feasibility of Preoperative Video Head Impulse Test to Predict the Nerve of Origin in Patients with Vestibular Schwannomas.

Vestibular schwannoma (VS) originates from Schwann cells in the superior or inferior vestibular nerve. Identifying the precise origin will help in determining the optimal surgical approach. We retrospectively analyzed the preoperative vestibular function test according to VS origin to determine whether the test is a valuable indicator of tumor origin. Forty-seven patients with VS (male:female = 18:29, mean age: 54.06 ± 13.50 years) underwent the cochleovestibular function test (pure-tone audiometry, caloric test, video head impulse test (vHIT), cervical and ocular vestibular-evoked myogenic potential, and posturography). All patients then underwent surgical removal of VS, and the schwannoma origin was confirmed. The tumor originated from the superior vestibular nerve (SVN group) in 21 patients, the inferior vestibular nerve (IVN group) in 26 patients, and an undetermined site in eight patients. The only value that differed significantly among the groups was the gain of the vestibular-ocular reflex (VOR) in the ipsilesional posterior canal (iPC) during the vHIT. Our results indicate that VOR gain in the iPC may be used to predict the nerve origin in patients with VS. Other cochleovestibular function tests have limited value to discriminate nerve origins, especially in cases of medium to large VS.

Evaluation of the vestibular system with video head impulse test in pregnant women with hyperemesis gravidarum.

We aimed to evaluate the semicircular canal functions of the vestibular system in pregnant women with hyperemesis gravidarum. This is a prospective case-control study. Among pregnant women in their first trimester (<14. gestational weeks) who presented to our outpatient clinic, 36 patients diagnosed with hyperemesis gravidarum defined as persistent nausea and vomiting requiring intravenous hydration or loss of at least 5% of prepregnancy weight and 34 healthy pregnant without nausea and vomiting were included. Otorhinolaryngologic examination and video head impulse test (vHIT) was performed to all patients. Vestibular-ocular reflex (VOR) gain and gain asymmetry were assessed between groups. The VOR gains in each semicircular canal did not differ between hyperemesis and control groups. Using a VOR gain cut-off value of 0.8, the groups were compared in terms of the frequency of low values. In the hyperemesis group, abnormally low gain values of left anterior canal were more frequently observed than in the control group (32 [88.9%], 22 [64.7%], respectively, P = 0.01). In left anterior-right posterior (LARP) plane VOR gain asymmetry was higher in hyperemesis group (13.5 [1.0-71.0], 6.0 [0.0-35.0], P = 0.001). No significant gain asymmetry was detected between the groups in the other planes. Semicircular canal functions were not abnormal globally in women with hyperemesis gravidarum. However, higher LARP plane asymmetry and low LA gain in women with hyperemesis suggests need for further research to clarify functional role of vestibular system on hyperemesis gravidarum.

Importance of Video Head Impulse Test Parameters for Recovery of Symptoms in Acute Vestibular Neuritis.

To examine the importance of video head impulse test parameter for recovery of symptoms in acute vestibular neuritis (AVN). Prospective study. Tertiary referral hospital. Twenty-seven patients with AVN were enrolled. We divided patients into two groups according to both dizziness handicap inventory (DHI) score and visual analog scale (VAS) at 6 months: Group F (symptoms free), DHI = 0 and VAS = 0; Group R (symptoms residual), DHI more than zero or VAS more than zero. All patients underwent video head impulse test paradigm (HIMP), and suppression head impulse test paradigm (SHIMP) initially and at 1 month. Patients were also asked to complete DHI and VAS initially, at 1 month and 6 months. We compared measured parameters between Group F and R. In HIMP, Group F showed higher vestibular-ocular reflex (VOR) gain, higher occurrence of covert corrective saccade (CS), lower occurrence and peak velocity of overt CS, and lower PR score than Group R at 1 month. In SHIMP, Group F showed higher VOR gain, higher occurrence and peak velocity of anti-CS, and higher PR score than Group R at 1 month. Above parameters of both HIMP and SHIMP at 1 month would be important factors to predict the residual symptoms in chronic phase of AVN.

Veterans with dizziness recruit compensatory saccades in each semicircular canal plane although VOR gain is normal.

Exposure to brain injury via blast or blunt mechanisms disrupts multiple sensorimotor systems simultaneously. Large numbers of US Gulf War era and Operation Iraqi/Enduring Freedom veterans with traumatic brain injury (TBI) are suffering the symptom of dizziness - presumed due to "Multi-Sensory Impairment", a clinical pattern of damage to the auditory, visual and vestibular sensorimotor systems. To describe the oculomotor response to rapid head rotation in a population of veterans with dizziness. We also describe the reliability of using the video head impulse test (vHIT) in a veteran population. We used the vHIT to evaluate the vestibular-ocular reflex (VOR) gain and presence of compensatory saccades (CS) in each semicircular canal of 81 veterans (31% TBI) with dizziness. Data was collected using the ICS Otometric™ vHIT. Data was processed using both the Otometric™ software and custom software written in MATLAB™. This data was evaluated through Kruskal-Wallis rank-sum test and analysis of regression. Veterans with dizziness recruit CS in all semicircular canal planes even though their VOR gain is normal. The vHIT is a reliable clinical test to quantify the metrics of the VOR and CS in veterans. Veterans with dizziness symptoms use compensatory saccades in all planes of semicircular canal rotation, despite having normal peripheral VOR gain during rapid head rotation. The video head impulse test is a stable measure of vestibular slow phase and metrics of compensatory saccades in veterans with dizziness.

Video head impulse test in vestibular migraine

IntroductionVestibular migraine as an entity was described in 1999 and its pathophysiology is still not established. Simultaneously with research to better understand vestibular migraine, there has been an improvement in vestibular function assessment. The video-head impulse test is one of the latest tools to evaluate vestibular function, measuring its vestibular-ocular reflex gain. ObjectiveTo evaluate vestibular function of vestibular migraine patients using video-head impulse test. MethodsCross-sectional case-control study homogeneous by age and gender with vestibular migraine patients according to the 2012–2013 Barany Society/International Headache Society diagnostic criteria submitted to video-head impulse test during intercrisis period. Results31 vestibular migraine patients were evaluated with a predominantly female group (90.3%) and mean age of 41 years old. Vestibular function was normal in both patient and control groups. Gain values for horizontal canals were similar between the two groups, but gain values for vertical canals were higher in the group with vestibular migraine (p<0.05). Patients with vestibular migraine felt more dizziness while performing the video-head impulse test than control subjects (p<0.001). ConclusionsPatients with vestibular migraine present normal vestibular function during intercrisis period when evaluated by video-head impulse test. Vertical canals, however, have higher gains in patients with vestibular migraine than in control subjects. Vestibular migraine patients feel dizziness more often while conducting video-head impulse test.

Differential effects of inferior olive lesion on vestibulo-ocular and optokinetic motor learning.

The combined operation of optokinetic reflex (OKR) and vestibular-ocular reflex (VOR) is essential for image stability during self-motion. Retinal slip signals, which provide neural substrate for OKR and VOR plasticity, are delivered to the inferior olive. Although it has been assumed that the neural circuitry and mechanisms underlying OKR and VOR plasticity are shared, differential role of the inferior olive in the plasticity of OKR and VOR has not been clearly established. To investigate the differential effect of inferior olive lesion on OKR and VOR plasticity, we examined the change of OKR and VOR gains after gain-up and gain-down VOR training. The results demonstrated that inferior olive-lesion differentially affected cerebellum-dependent motor learning. In control mice, OKR gain increased after both gain-up and gain-down VOR training, and VOR gain increased after gain-up VOR training and decreased after gain-down VOR training. In inferior olive-lesioned mice, OKR gain decreased after both gain-up and gain-down VOR training, and while VOR gain did not significantly change after gain-up VOR training, VOR gain decreased after gain-down VOR training. We suggest that multiple mechanisms of plasticity are differentially involved in VOR and OKR adaptation, and gain-up and gain-down VOR learning rely on different plasticity mechanisms.

High-Frequency Horizontal Semicircular Canal Function in Certain Menière's Disease.

To characterize video head impulse testing (vHIT) in definitive Menière's disease and to investigate the relationship between vHIT results and other audiovestibular function tests. Fifty-four patients with certain Menière's disease, that is, patients with clinically definite Menière's disease and endolymphatic hydrops visualized by locally enhanced inner ear MR imaging, were recruited for this study. All patients underwent vHIT. The vestibular-ocular reflex gain at 60 ms and refixation saccades were the outcome parameters measured. Saccades were characterized by determining the saccade frequency, their mean latency, and their mean velocity. Seven of 54 patients had bilateral normal vHITs. Clearly pathologically vHITs with decreased gain and refixation saccades were observed in further seven patients. The majority of patients exhibited vHITs with refixation saccades but normal gain. Saccades mostly occurred bilaterally. There was no correlation between vHIT gain or saccades and caloric irrigation, cervical vestibular evoked myogenic potential or audiometry for Menière's ears. Furthermore, vHIT gain or saccades correlated neither with age nor with the duration of the disease. Pathological low vHIT gain values are rarely observed in patients with certain Menière's disease, while refixation saccades occur very frequently. In the majority of patients, saccades occur bilaterally. In Menière's disease, in contrast to vestibular neuritis, there is no compensatory decrease of saccade latency over time.

Vestibular cerebellar evoked potentials in humans and their modulation during optokinetic stimulation.

We recorded evoked potentials (EPs) from over the posterior fossa and in parallel ocular vestibular evoked myogenic potentials (OVEMPs) during visuo-vestibular stimulation in a sample of 7 male and 11 female human subjects. In 9 of the 18 subjects we were able to record EPs reliably in the form of an early biphasic positive-negative wave with latencies ~12 and 17 ms ipsilateral to head acceleration direction (P12-N17) and a slightly later, contralateral, biphasic positive-negative wave with latencies ~19 and 23 ms (P19-N23). The amplitudes of the responses varied widely between subjects. Both P12 and N23 EPs were modulated by the mode of visual stimulation, larger for vection (sense of movement) compared with optokinetic nystagmus and for congruent movement. We suggest that the EPs measured over the posterior fossa are a manifestation of climbing fiber responses of cerebellar cortical Purkinje cells, i.e., a form of vestibular cerebellar EP (VsCEP). The two subject groups with and without VsCEPs were distinguished by the magnitude of their OVEMPs and their subjective experience of vection. The modulation of VsCEPs by visual context may be a manifestation of cerebellar control of linear vestibular ocular reflex gain. NEW & NOTEWORTHY We report likely vestibular cerebellar evoked potentials (VsCEPs) produced by lateral head impulses recorded in intact humans over the posterior fossa. VsCEPs occurred as short-latency P12-N17 waves ipsilateral to the direction of head motion and as P19-N23 contralaterally and were present in half our subjects. Their properties suggest that the VsCEPs may be of a climbing-fiber origin. VsCEPs are related to the perception of motion and, possibly, control of linear vestibular ocular reflex gain.

Vestibular Outcomes in Bilateral Posterior Semicircular Canal Occlusion for Refractory Benign Positional Vertigo.

Bilateral posterior semicircular canal (PSCC) occlusion is a successful treatment of bilateral benign positional vertigo (BPV) refractory to particle repositioning manoeuvers. Little about the effects on the vestibular ocular reflex (VOR) postoperatively, which is the intent of this study. All patients who underwent bilateral posterior canal occlusion for BPV at the University Health Network by the senior author (J.A.R.) between 2001 and 2017 with pre- and postoperative vestibular testing were included in the study.All patients underwent a detailed history and neuro-otological examination including dynamic visual acuity (DVA). Laboratory testing including video head impulse testing or magnetic scleral search coil testing, video nystagmography, cervical and ocular vestibular evoked myogenic potentials and audiological testing before and following their procedure at 1, 6, and 12 months postoperatively. Three patients were included in the study, all females, with a mean age of 41 years (range 36-44 yr). All patients had developed bilateral BPV after head trauma. Mean length of follow-up was 26 months (range 6-84 mo). All patients demonstrated a reduction in the vertical VOR of between 0.37 and 0.57/s at 1 month postocclusion. Between 6 and 12 months postoperatively, an improvement in their vertical VOR between 0.45 and 0.75/s was observed. Clinically, all patients reported complete resolution of their positional vertigo with a negative Dix-Hallpike bilaterally at follow-up. None reported oscillopsia, which was confirmed with DVA testing. Bilateral PSCC occlusion results in a reduction in the vertical VOR of the PSCCs.Over a 6 to 12 month time period improvement in the VOR gain can be demonstrated, most likely due to central compensation. There is clinical correlation with improvement in DVA testing. Bilateral PSCC occlusion is a safe and effective treatment for bilateral BPV proved refractory to particle repositioning manoeuvers.