Vestibulo-ocular Research Articles

Wall-Eyed Internuclear Ophthalmoplegia: History and Hypothesis.

Most patients with internuclear ophthalmoplegia (INO) are orthotropic, although a subset is exotropic. When INO is bilateral, this is termed wall-eyed bilateral internuclear ophthalmoplegia (WEBINO). In 1979, Sharpe described his "first case" of wall-eyed monocular internuclear ophthalmoplegia (WEMINO) as "a unique clinical syndrome" characterized by unilateral INO and ipsilateral exotropia. WEMINO was clinically identified in seven patients, with oculographic correlation in six and neuropathological confirmation in one. Oculographic features of exotropic INO patients were compared with those of six orthotropic INO patients using magnetic search coil and infrared oculography. All clinically defined WEMINO patients showed slowed, hypometric ipsilateral saccades by oculography. Six patients had ipsilateral exotropia, and three had ipsilateral hypertropia. Ipsilateral abducting saccades had faster peak velocities for smaller saccades, more so for orthotropic patients. Exotropic patients had normal sinusoidal mean vestibulo-ocular reflex (VOR) gains and phases; orthotropic patients had subnormal mean VOR gains and phase leads. WEMINO is a clinical ocular motor syndrome characterized by unilateral slow, hypometric adducting saccades with exotropia and hypertropia of the ipsilateral eye. We propose that it results from discrete unilateral damage to burst-tonic fibers in the medial longitudinal fasciculus (MLF) with sparing of the adjacent extrafascicular pathways. Paradoxically, orthotropic INO results from more extensive damage to ascending pathways lateral, ventral and caudal to the MLF. Direct injury to the medial rectus subnucleus is not required. This manuscript was in preparation at the time of Dr Sharpe's death in 2013 and is an acknowledgement of his forward-thinking, as his hypotheses have stood the test of time.

Video Head Impulse Test Coherence Predicts Vertigo Recovery in Sudden Sensorineural Hearing Loss with Vertigo.

The labyrinthitis poses inferior quality of life with prolonged vestibular symptoms in patients with sudden sensorineural hearing loss with vertigo (SSNHLV). This study utilized a novel coherence analysis in video head impulse test (vHIT) to investigate vertigo outcomes in SSNHLV patients. A retrospective review included 48 SSNHLV patients completing high-dose steroid treatment between December 2016 and April 2023, and 38 healthy volunteers were prospectively enrolled between November 2022 and April 2023 in our academic tertiary referral center. Magnitude-squared wavelet coherence was measured between eye and head velocities in vHIT to represent the degree of correlation across different frequency bands. Vertigo recovery, assessed by visual analog scale equal to zero at 2 weeks and 2 months, was analyzed using a multivariable Cox regression model. The VAS among patients with SSNHLV was 5.73 ± 2.45 (mean ± standard deviation). Higher coherent frequencies in the horizontal semicircular canal (SCC), posterior SCC, mean, and minimal coherent frequencies of all three SCCs combined were significantly associated with early complete vertigo remission at two weeks post-treatment. In the multivariate analysis, the minimal coherent frequency among the three SCCs emerged as an independent factor (hazard ratio [HR] 2.040, 95% confidence interval [CI] 1.776-2.304). At two months post-treatment, in addition to the previously significant parameters, vestibulo-ocular reflex (VOR) abnormality in the posterior SCC, gains in the horizontal and posterior SCCs, total and overt saccades in the horizontal SCC, coherent frequency in the anterior SCC, and mean VOR gain of all three SCCs combined were also statistically significantly related to total vertigo relief. The greater minimal coherent frequency among the three SCCs was a strong factor contributing to earlier relief of vertigo in patients with SSNHLV. Coherence analysis in vHIT may be more sensitive than time series analysis for evaluating vertigo prognosis prediction.

The vestibular implant: effects of stimulation parameters on the electrically-evoked vestibulo-ocular reflex

IntroductionThe vestibular implant is a neuroprosthesis which offers a potential treatment approach for patients suffering from vestibulopathy. Investigating the influence of electrical stimulation parameters is essential to improve the vestibular implant response. Optimization of the response focuses on the electrically evoked vestibulo-ocular reflex. It aims to facilitate high peak eye velocities and adequate alignment of the eye movement responses. In this study, the basic stimulation parameters of the vestibular implant were tested for their effect on the electrically evoked vestibulo-ocular reflex.MethodsFour stimulation parameters, including the stimulation amplitude, phase duration, stimulus rate and speed of change of stimulation, were systematically tested in a cohort of nine subjects with a vestibulo-cochlear implant. These parameters were tested to evaluate their effect on fitting settings (i.e., threshold of activation, upper comfortable limit and dynamic range) as well as on the electrically evoked vestibulo-ocular reflex (peak eye velocity and alignment).ResultsIt was confirmed that, in addition to current amplitude, the peak eye velocity of the response can be increased by increasing the phase duration and pulse rate. Both parameters have little effect on the alignment of the eye response. However, a longer phase duration decreased the range between the threshold of activation and the upper comfortable limit of the electrical stimulation (i.e., dynamic range). Furthermore, these results show that next to the amplitude of the stimulation, the speed of change in stimulation has a determinative positive effect on the peak eye velocity.ConclusionThe observations in this study imply that the vestibular implant response, in terms of peak eye velocity, can be optimized with a higher pulse rate and longer phase duration. However, this comes at a trade-off between the dynamic range and power consumption. This study provides essential insights for fitting strategies in future vestibular implant care.

Wernicke's Encephalopathy

Wernicke encephalopathy is a thiamine deficiency condition that has a wide range of somatic causes in addition to alcohol abuse. Most patients do not have the classical clinical triad — oculomotor dysfunction, ataxia and cognitive impairment at the onset of the disease, which makes timely diagnosis difficult. The disease may manifest as dizziness, unsteadiness, double vision, or cognitive impairment. Key clinical manifestations include symmetrical gaze-evoked nystagmus, truncal ataxia, bilateral abducens paresis, internuclear ophthalmoplegia, bilateral vestibular-ocular reflex reduction, and anterograde amnesia. To make a diagnosis, the presence of a condition leading to thiamine deficiency is required. The diagnosis is confirmed by MRI, but even with clinical suspicion of Wernicke encephalopathy, it is necessary to initiate parenteral therapy with thiamine in an adequate dose. With timely treatment, the disease has a good prognosis.

Effect of Chiropractic Intervention on Oculomotor and Attentional Visual Outcomes in Young Adults With Long-Term Mild Traumatic Brain Injury: A Randomized Controlled Trial

ObjectiveThis study aimed to establish if chiropractic care can improve oculomotor and cognitive symptoms in individuals with persistent postconcussion syndrome (PPCS). MethodsA single-blind, randomized controlled intervention study recorded baseline computerized eye-tracker assessment (CEA) outcomes in 40 young adults with PPCS following mild traumatic brain injury. Participants were randomly allocated to either a chiropractic or age-matched active control intervention, and the change in CEA outcomes following intervention was compared between the chiropractic and control groups. A battery of CEAs including egocentric localization, fixation stability, pursuit, saccades, Stroop, and the vestibulo-ocular reflex, were used to assess oculomotor function, visual attention/processing, and selective attention. ResultsRelative to the control group, participants receiving the chiropractic intervention scored better in the Stroop test (P < .001), had improved gaze stability during both vestibulo-ocular reflex (P < .001) and fixation stability (P = .009), and a lower vertical error in egocentric localization (P < .001). However, performance was poorer in pursuits, where they had an increased tracking error (P < .001). ConclusionChiropractic care in participants with PPCS significantly improved static and dynamic gaze stability, and performance in the Stroop test, compared with a control intervention. These results suggest that chiropractic care can offer a novel avenue for alleviating certain visual and cognitive symptoms in patients with PPCS. It also adds to the growing evidence that suggests that some longstanding PPCS visual symptoms may have a spinal or proprioceptive basis.

The Impact of Sleep Deprivation on Video Head Impulse Test Results.

To investigate the association between sleep deprivation and vestibular dysfunction by Video Head Impulse Test (vHIT). This prospective clinical trial explores the impact of acute sleep deprivation on the vestibular-ocular reflex (VOR) in medical residents. The study involved healthy physicians from diverse medical disciplines. Participants underwent vHIT assessments before and after a 26-h shift. The examinations focused solely on the right lateral semicircular canal. Participants further completed a demographics and fatigue questionnaire, including the Fatigue Severity Scale (FSS) questionnaire and a Visual Analog Fatigue Score (VAFS). The study involved 30 medical residents. Participants experienced a statistically significant decrease in VOR gain in the right horizontal semicircular canal during a 26-h shift (p < 0.01). While the FSS and VAFS questionnaires showed no significant difference before and after the shift, the analysis of ∆VOR gain indicated a statistically significant increase associated with decreased sleep time during the shift (p = 0.018, 95% Confidence Interval [0.08, 0.68]). The most substantial increase in ∆VOR occurred between 22-26 h of sleep deprivation. No significant differences were observed in ∆VOR between genders, ages, disciplines, department shifts versus emergency room shifts, or years of residency. vHIT can be used as an objective, reliable screening tool for severe sleep deprivation among physicians. The decrease in the VOR gain may indicate that vestibular function is influenced by sleep deprivation. The clinical significance of these findings is still questioned, more studies may help to assess this effect. 3 Laryngoscope, 2024.

Toward Intelligent Head Impulse Test: A Goggle-Free Approach Using a Monocular Infrared Camera.

To assess vestibular function, video head impulse test (vHIT) is taken as the gold standard by evaluating the vestibulo-ocular reflex (VOR). However, vHIT requires the patient to wear a specialized head-mounted goggle equipment that needs to be calibrated before each use. For this, we proposed an intelligent head impulse test (iHIT) setting with a monocular infrared camera instead of the head-mounted goggle and contributed correspondingly a video classification approach with deep learning to vestibular function determination. Within the iHIT framework, a monocular infrared camera was set in front of the patient to capture test videos, based on which a dataset DiHIT of HIT video clips was set up. We then proposed a two-stage multi-modal video classification network, trained on the dataset DiHIT, that took as input the eye motion and head motion data extracted from the facial keypoints via HIT clips and outputted the identification of the semicircular canal (SCC) being tested (SCC identification) and determination of VOR abnormality (SCC qualitation). Experiments on this dataset DiHIT showed that it achieved the accuracy of 100% in prediction of SCC identification. Furthermore, it attained predictive accuracies of 84.1% in horizontal and 79.0% in vertical SCC qualitation. Compared with existing video-based HIT, iHIT eliminates goggles, does not require equipment calibration, and achieves complete automation. Furthermore, iHIT will bring more benefits to users due to its low cost and ease of operation. Codes and use case pipeline are available at: https://github.com/dec1st2023/iHIT. 3 Laryngoscope, 2024.

Amplification of vibration induced nystagmus in patients with peripheral vestibular loss by head tilt.

In patients with unilateral loss of vestibular function (UVL) vibration of the skull leads to a response of the vestibulo-ocular reflex (VOR) called vibration-induced nystagmus (VIN), with slow phases usually directed toward the paretic ear. This response is thought to result from the difference between the neural discharge in semicircular canal afferents from the healthy and the affected labyrinth. The brain interprets this difference as a sustained imbalance in angular (rotational) vestibular tone, which in natural circumstances would only occur when the head was rotating at a constant acceleration. To study this effect, we used a contemporary model of the neural network that combines sensory information about head rotation, translation, and tilt relative to gravity to estimate head orientation and motion. Based on the model we hypothesize that in patients with UVL, the brain may estimate not only a "virtual" rotation from the induced canal imbalance but also a subsequent "virtual" translation from the incorrect computation of the orientation of the head relative to gravity. If this is the case, the pattern of vibration-induced nystagmus will depend on the orientation of the head relative to gravity during the stimulation. This model predicts that this "virtual" translation will alter the baseline VIN elicited with the head upright; augmenting it when the affected ear is down and diminishing it when the affected ear is up. Confirming this hypothesis, we recorded VIN in 3 patients with UVL (due to vestibular neuritis) in upright, right ear-down, and left ear-down positions and each showed the expected pattern. From a practical, clinical view, our results and modeling suggest that positional VIN might reveal a hidden imbalance in angular vestibular tone in patients with UVL, when patients have equivocal signs of a vestibular imbalance, such as a minute amount of spontaneous or vibration-induced nystagmus with the head upright. This research provides insights into the underlying mechanisms of vestibular processing, the analysis of nystagmus in patients with UVL, and guides the design of a new bedside diagnostic test to assess vestibular function in patients with dizziness and imbalance.

Effects of aging on otolith morphology and functions in mice.

Increased fall risk caused by vestibular system impairment is a significant problem associated with aging. A vestibule is composed of linear acceleration-sensing otoliths and rotation-sensing semicircular canals. Otoliths, composed of utricle and saccule, detect linear accelerations. Otolithic organs partially play a role in falls due to aging. Aging possibly changes the morphology and functions of otoliths. However, the specific associations between aging and otolith changes remain unknown. Therefore, this study aimed to clarify these associations in mice. Young C56BL/6 N (8 week old) and old (108-117 weeks old) mice were used in a micro-computed tomography (μCT) experiment for morphological analysis and a linear acceleration experiment for functional analysis. Young C56BL/6 N (8 week old) and middle-aged (50 week old) mice were used in electron microscopy experiments for morphological analysis. μCT revealed no significant differences in the otolith volume (p = 0.11) but significant differences in the otolith density (p = 0.001) between young and old mice. μCT and electron microscopy revealed significant differences in the structure of striola at the center of the otolith (μCT; p = 0.029, electron microscopy; p = 0.017). Significant differences were also observed in the amplitude of the eye movement during the vestibulo-ocular reflex induced by linear acceleration (maximum amplitude of stimulation = 1.3G [p = 0.014]; maximum amplitude of stimulation = 0.7G [p = 0.015]), indicating that the otolith function was worse in old mice than in young mice. This study demonstrated the decline in otolith function with age caused by age-related morphological changes. Specifically, when otolith density decreased, inertial force acting on the hair cells decreased, and when the structure of striola collapsed, the function of cross-striolar inhibition decreased, thereby causing a decline in the overall otolith function.

Video head impulse gain is impaired in myotonic dystrophy types 1 and 2.

This study was undertaken to examine vestibulo-ocular reflex (VOR) characteristics in myotonic dystrophy type 1 (DM1) and type 2 (DM2) using video head impulse testing (vHIT). VOR gain, refixation saccade prevalence, first saccade amplitude, onset latency, peak velocity, and duration were compared in DM1, DM2, age-matched normal controls, and patients with peripheral and central vestibulopathies. Fifty percent of DM1 and 37.5% of DM2 patients demonstrated reduced VOR gain. Refixation saccade prevalence for horizontal canal (HC) and posterior canal (PC) was significantly higher in DM1 (101 ± 42%, 82 ± 47%) and DM2 (70 ± 45%, 61 ± 38%) compared to controls (40 ± 28% and 43 ± 33%, p < 0.05). The first saccade amplitudes and peak velocities were higher in HC and PC planes in DM1 and DM2 compared to controls (p < 0.05). HC slow phase eye velocity profiles in DM1 showed delayed peaks. The asymmetry ratio, which represents the percentage difference between the first and second halves of the slow phase eye velocity response, was therefore negative (-22.5 ± 17%, -2.3 ± 16%, and - 4.7 ± 8% in DM1, DM2, and controls). HC VOR gains were lower and gain asymmetry ratio was larger and negative in patients with DM1 with moderate to severe ptosis and a history of imbalance and falls compared to the remaining DM1 patients (p < 0.05). In peripheral vestibulopathies, saccade amplitude was larger, peak velocity was higher, and onset latency was shorter (p < 0.05) than in DM1. In central vestibulopathy (posterior circulation strokes), saccade peak velocity was higher, but amplitude and onset latency were not significantly different from DM1. VOR impairment is common in DM1 and DM2. In DM1, refixation saccade characteristics are closer to central than peripheral vestibulopathies. Delayed peaks in the vHIT eye velocity profile observed in patients with DM1 may reflect extraocular muscle weakness. VOR impairment and VOR asymmetry in DM1 are associated with imbalance and falls.

Evaluation of VOR function with vHIT in unilateral pediatric cochlear implant users

ObjectiveThe changes in the inner ear affect both the cochlea and the vestibule and these effects are observed after cochlear implantation surgery. The aim of the current study is to evaluate the effect of unilateral cochlear implant use on vestibulo-ocular reflex (VOR) in children. MethodsIn the current study, 29 cochlear implanted children, aged 7–18 years, were include as the study group and 32 children, in the same age range, were included with normal-hearing as the control group. vHIT was used to evaluate VOR and the results of unilateral CI users were compared with the control group. The study group was evaluated in two different situations: cochlear implant sound processor on (CI-ON) and cochlear implant sound processor off (CI-OFF). The data obtained in the evaluations were compared between the implanted ear and the non-implanted ear between the CI-ON and CI-OFF states within the study group and between the study group and the control group. ResultsWhen the CI-ON and CI-OFF conditions in the study group were compared, no significant difference was found (p > 0.05). Similarly, no significant difference was found between the implanted ear and the non-implanted ear (p > 0.05). Also, there was no significant difference in the comparisons between the study group and the control group (p > 0.05). ConclusionvHIT is a functional test method that can be used in children to test vestibular function after cochlear implant. vHIT is a comfortable test to use after cochlear implantation to demonstrate the functionality of the vestibular system. And it provides consistent results regardless of whether the speech processor is on or off.

Detection of human drowsiness by the vestibulo-ocular reflex compensating for heartbeat-induced head perturbations

The vestibulo-ocular reflex (VOR) stabilizes vision during head movements by counter-rotating the eyes in the orbits. Although considered one of the simplest reflexes due to its minimal neuronal circuity comprising a 3-neuron arc, previous studies have shown that VOR performance deteriorates in both monkeys and humans when they are drowsy. Given constant head perturbations under dynamic environments, the VOR has been proposed as a viable biomarker for detecting human drowsiness in automobiles and other moving vehicles. However, under stationary environments where exogenous head movements are absent, its applicability has been questioned. In this study, we demonstrate that each heartbeat generates small yet distinctive head movements, and the VOR compensates for these minor head perturbations. Furthermore, we show that the effectiveness of VOR responses varies with the degree of drowsiness, indicating that the VOR can serve as an indicator of drowsiness, even in stationary contexts such as in classrooms and offices.

Clinical and Video-Oculographic Characteristics of Spinocerebellar Ataxia Type 27B (GAA-FGF14 Ataxia): A Single-Center Retrospective Study

An intronic GAA repeat expansion in the FGF14 gene was recently identified as a common cause of autosomal dominant GAA-FGF14 ataxia (SCA27B). We aimed to characterize in detail the clinical and video-oculographic features in our cohort of SCA27B patients. We genotyped the FGF14 GAA repeat expansion in 52 patients with unsolved late-onset cerebellar ataxia. Brain MRI and nerve conduction study, as well as video-oculographic (VOG) assessment, were performed. Eight patients (15.4%) with pathogenic GAA repeat expansion in the FGF14 gene were found. The median age at onset was 51 years (range—23–63 years). Sensory axonal neuropathy was found in 5/8 patients. Cerebellar atrophy was observed in 5/8 patients, and in one case, pontocerebellar atrophy was found. All tested patients had impaired smooth pursuit, 5/6 patients had impaired vestibulo-ocular reflex suppression, nystagmus, and an increased number of square wave jerks, 4/6 patients had horizontal gaze-evoked nystagmus, 3/6 had spontaneous downbeat nystagmus, and 1/6 had an upbeat one. Video head impulse test gain was lower than 0.8 on both sides in 2/4 patients, along with the presence of overt saccades. Further studies in different cohorts are needed to complete the phenotype of the FGF14-related disorders.

Transiently worse postural effects after vestibulo-ocular reflex gain-down adaptation in healthy adults.

Suffering an acute asymmetry in vestibular function (i.e., vestibular neuritis) causes increased sway. Non-causal studies report associations between lateral semicircular canal function and balance ability, but direct links remain controversial. We investigate the immediate effect on body sway after unilateral vestibulo-ocular reflex (VOR) gain down adaptation simulating acute peripheral vestibular hypofunction. Eighteen healthy adults, mean age 27.4 (± 12.4), stood wearing an inertial measurement device with their eyes closed on foam before and after incremental VOR gain down adaptation to simulate mild unilateral vestibular neuritis. Active head impulse VOR gain was measured before and after the adaptation to ensure VOR gain adaptation. Percentage change for VOR gain was determined. Sway area was compared before and after VOR adaptation. VOR gain decreased unilaterally exceeding meaningful change values. Sway area was significantly greater immediately after VOR gain down adaptation, but quickly returned to baseline. In a subset of subjects VOR gain was re-assessed and found to remain adapted despite sway normalization. These results indicate that oculomotor adaptation targeting the lateral semicircular canal VOR pathway has an immediate, albeit transient increase in body sway. Rapid return of body sway to baseline levels suggests dynamic sensory reweighting between vestibular and somatosensory inputs to resolve the undesirable increased body sway.

Assessment of hearing and balance functions in patients with acromegaly by the use of an audiovestibular test battery: a cross-sectional study.

Patients with acromegaly may have abnormalities in their hearing and balance as a result of modifications in body composition and involvement of the temporal bone. The objective of this study is to examine if there are any changes in the auditory and vestibular systems in individuals with acromegaly by using audiogram and vestibular function tests. This prospective study included 33 healthy controls and 33 acromegaly patients who were matched for age and gender distribution. A pure-tone audiometry test was conducted, including frequencies ranging from 250Hz to 8000Hz. Videonystagmography (VNG) was employed to assess nystagmus, an essential parameter used for assessing vestibular functions. The Video Head Impulse Test (v-HIT) was used to assess the vestibulo-ocular reflex (VOR). The Dizziness Handicap Inventory (DHI) was applied to evaluate the subjective complaints of the participants. The acromegaly patients had significantly elevated hearing thresholds at all frequencies (250, 500, 1000, 2000, 4000, and 6000Hz) compared to the control group (p < 0.005). The VNG tests, including gaze horizontal, gaze vertical, saccade, spontaneous nystagmus, optokinetic, smooth pursuit, and positioning tests, did not show any statistically significant difference between the two groups (p values > 0.05). The patient group demonstrated reduced VOR gains compared to the control group in the anterior and posterior channels (p < 0.005). There was no statistically significant difference between the two groups for the occurrence of aberrant eye movements (p values > 0.05). The patient group had a total DHI score of 6.6 ± 3.2, while the control group had a score of 3.2 ± 2.6 (independent samples t-test; p < 0.001). Therefore, The patient group exhibited significantly greater subjective vestibular symptoms. Patients with acromegaly experience impaired auditory function. The central vestibular system remains unaffected, while the gains of the vestibulo-ocular reflex (VOR) in the posterior and anterior semicircular canals are decreased. Additionally, these patients report experiencing subjective dizziness. Screening for hearing and balance in patients with acromegaly may improve the quality of life of patients and prevent problems related to balance disorders at an early stage.

Local anaesthetic delivery through indwelling retrobulbar catheters for ocular pain control in horses

AbstractBackgroundEquine corneal disease is common and painful. Current pain mitigation strategies are often suboptimal, especially early in the disease.ObjectivesTo evaluate the effects of local anaesthetic delivery via indwelling retrobulbar catheter on corneal sensitivity, pupil size, pupillary light responses (PLRs), and ocular motility in normal horses.Study designRandomised, controlled crossover experiment.MethodsOne eye was randomly selected from seven horses. A 20‐gauge catheter was placed in the retrobulbar space and injected with 10 mL of 0.5% bupivacaine or 0.9% saline. Cochet–Bonnet esthesiometry (CBE), pupil photogrammetry, PLRs, and oculocephalic reflexes were evaluated before injection (t = 0) and t = 0.25, 1, 3, 6, 9 and 12 h after injection. Following a 7–14 day washout period, this procedure was repeated using the alternative injection solution. Corneal touch thresholds (CTTs) derived from CBE and pupillary areas (PA; as measured from photographs) were compared across time for each group. PLRs and oculocephalic reflexes were compared between groups at each evaluation time point.ResultsSaline did not affect CBE, PA, PLRs or oculocephalic reflexes at any time point. Bupivacaine reduced CTT compared with saline for 6 h, with maximum reduction at t = 1 h (bupivacaine: 0.08 ± 0.20 cm; saline: 4.21 ± 0.39 cm; p &lt; 0.001). Bupivacaine increased PA compared with saline for 3 h, with maximum increase at t = 3 h (bupivacaine: 349.75 ± 84.80 mm2; saline: 194.65 ± 27.03 mm2; p = 0.04). Bupivacaine injection reduced PLRs for 9 h and oculocephalic reflexes for 3 h; saline had no effect. Mild adverse effects included chemosis, blepharoedema, and transiently reduced palpebral reflex.Main limitationsReduction in CTT may not directly translate to pain control in clinical horses with corneal disease. Adverse effects of repeated injections were not evaluated.ConclusionsInjection of bupivacaine via an indwelling retrobulbar catheter in horses reduces corneal sensitivity and may be useful in reducing pain in horses with corneal disease.

Cervical Spine Vibration Modifies Oculomotor Function in Young Adults with Traumatic Brain Injury

ObjectiveThe purpose of this study was to investigate if vibrational interference of spinal proprioception affects oculomotor function, visual attention and processing, and selective attention in individuals with mild traumatic brain injury (mTBI) compared to healthy age-matched controls. MethodsThis study was a parallel design, single-session intervention with 20 young adults with mTBI and 20 age-matched controls. Each completed a battery of computerized eye-tracking assessments (CEAs), including egocentric localization, fixational stability, smooth pursuit, saccades, Stroop, and the vestibulo-ocular reflex (VOR), and then had their cervical spine function (flexion-relaxation ratio) recorded at baseline. Spinal vibration (100 Hz) was applied to the cervical spine and the CEA battery was repeated. CEA outcomes were compared to baseline and between mTBI and control groups. ResultsFollowing cervical vibration, significant pre to post-differences were seen in both the mTBI and control group for egocentric localization, fixation stability, pursuit, saccades, Stroop, and VOR. At baseline, there was a significant difference between the mTBI and control groups across many CEA measures, with the mTBI group performing more poorly in egocentric localization, pursuit, saccades, Stroop, and VOR. The mTBI group also had a poorer flexion-relaxation ratio than the control group. ConclusionCervical spine vibration improved cognitive and oculomotor performance in the mTBI group for VOR, Stroop, and pursuit, but had mixed effects on the control group. These findings suggest that some optometric mTBI symptoms may result from spinal or proprioceptive dysfunction, as altering proprioceptive input appears to positively impact visual outcomes.

Comparing saccades in Visually Enhanced Vestibular-Ocular Reflex and video head impulse test in vestibular assessment

ObjectiveThis study aimed to develop and evaluate a novel software tool for robust analysis of the Visually Enhanced Vestibular-Ocular Reflex (VVOR) and video head impulse test (vHIT) saccades. MethodsA retrospective study was conducted on 94 patients with Meniere's Disease (MD), unilateral vestibular hypofunction (UVH), and vestibular migraine (VM). The MATLAB-based VVOR Analysis System and Saccades All in One software were utilized for data processing. New techniques, VVOR_diff and VVOR_cycle, were deployed for saccade parameter extraction. ResultsSaccade incidence rates, examined through vHIT, VVOR_diff, and VVOR_cycle, exhibited distinct patterns in MD, UVH, and VM patients. Frequent instances of multiple saccades within a single cycle were noted on the affected side in MD and UVH patients. Statistically significant differences in saccade gain and incidence rates between the affected and unaffected sides were evident in MD and UVH patients. Notably, high inter-method and intra-method correlations suggested consistency across different methods and potential interactions within one. ConclusionThe software proved effective in extracting saccades and reducing noise in VVOR data, thereby enhancing the evaluation of vestibular function and potentially improving diagnostic accuracy for vestibular disorders.

Role of the video head impulse test in the evaluation of vestibulo-ocular reflex in individuals with Parkinson's disease.

<p>Parkinson&rsquo;s disease (PD) is the most common movement disorder and the second most common neu&shy;rodegenerative disease of the central ner&shy;vous system. Dizziness is frequently reported by PD patients, yet there is a paucity of research focusing on the vestibulo-ocular reflex (VOR) in this population using high-frequency vestibular testing. This study aims to investigate the VOR in individuals with PD using the video head thrust test with and without suppression.&nbsp;</p>. <p>Forty individuals with PD and 40 healthy individuals were included in the study. According to the Hoehn-Yahr Scale, individuals with PD were defined as early stage with a score of 1&ndash;2.5 and middle to late stage with a score of 3 to 5. The Head Impulse Testing Paradigm (HIMP) and Suppression Head Impulse Testing Paradigm (SHIMP) were applied to all individuals.</p>. <p>No statistically significant difference was observed between the PD group and the control group in terms of semicircular canal (SCC) gains in both HIMP and SHIMP tests. No catch-up saccades were observed in the right anterior, right posterior, left anterior, and left posterior SCC planes in the PD and control groups. However, in the right lateral SCC plane 32 patients in the PD group had saccades, while 8 patients in the control group had saccades. In the left lateral SCC plane, 32 patients in the PD group and 9 patients in the control group had catch-up saccades. A statistically significant difference was observed in the number and amplitude of saccades in the right and left lateral SCC planes compared to the control group (p&lt;0.05). In addition, in the PD group, the amplitude, peak velocity, and latency of the anticompensatory saccades seen in SHIMP showed a statistically significant difference compared to the control group (p&lt;0.05).</p>. <p>VOR in the vertical SCC plane was not affected in individuals with PD. However, VOR in the lateral SCC plane was affected. It was concluded that when evaluating VOR with both HIMP and SHIMP in individuals with PD, the presence of catch-up saccades should be focused on and evaluated for possible vestibular dysfunction, even though SCC gains are normal. This study will contribute to a deeper understanding of vestibular function in PD, potentially informing better management strategies for dizziness in this population.&nbsp;</p>.

CANVAS For A Diagnosis: Can You Hear The Hooves Of Zebras?

Abstract Background A 75year old male presented to a Movement Disorder Service with complex multimorbidity including: chronic pain, type 2 diabetes mellitus, hypoventilatory obesity syndrome, biliary calculus, moderate aortic stenosis, marked orthostatic hypotension, pulmonary hypertension, coronary artery bypass grafting, permanent pacemaker for complete atrioventricular block, carpal tunnel release bilaterally, polypharmacy and bilateral cataracts. History elucidated a distal to proximal sensory loss over 20years and neuropathic pain without nerve conduction confirmation; and progressively ataxic gait over several years. He also complained of hypophonia, bruxism, excessive daytime somnolence, passages, transitions, visual agnosia, textural illusion, oscillopsia, irritability, inflexibility, hoarding, impulsivity, disorganisation, inattention, apathy, depression and aspontaneity. He was intolerant of nocturnal continuous positive airway pressure device. Epworth score was 21. Methods Examination demonstrated: marked orthostatic hypotension, preserved cognition, hypersomnolence, dyspraxic dysgraphia, palmar and antecubital agraphaesthesia, downbeat horizontal nystagmus at eccentric gaze positions, square wave jerks, bidirectionally impaired head impulse test, dysmetric saccades, asymmetric cerebellar signs in upper and lower limbs, rightward Pisa syndrome, kinesigenic dystonic axial posturing, rightward laterocollis and equivocal Babinski/Oppenheim reflexes. Gait assessment demonstrated sensory and cerebellar ataxic features with marked apraxia. No pes cavus. Results Computed tomography of brain had Fazekas 1 small vessel disease, Medial temporal atrophy score 1, Koedam 1 and age-commensurate cerebral and cerebellar atrophy. RFC1 gene testing confirmed biallelic intronic AAGGG repeat expansion disorder. Conclusion Cerebellar Ataxia Neuropathy and Vestibular Areflexia Syndrome (CANVAS) should be considered in patients with presentations from mid-life of progressive sensory ataxic neuropathy, altered vestibular ocular reflex, gaze evoked nystagmus and prominent dysautonomia. CANVAS is a rare autosomal recessive genetic disorder with a protean presentation. Referral to Genetics Services should be undertaken for family counselling. Keeping an open mind in complex, multimorbid patients to a potentially unifying diagnosis is important to guide prognostication. The rumble of hooves in the distance is not always that of horses.