Ocular Motor System Research Articles

Longitudinal investigation of optic chiasm in patients with traumatic brain injury

BackgroundTraumatic brain injury (TBI) often precipitates a cascade of neurophysiological alterations, impacting structures such as the optic nerve and ocular motor system. However, the literature lacks expansive investigations into the longitudinal changes in the optic chiasm and its relationship with the clinical recovery of visual processing. This study aimed to scrutinize longitudinal changes in optic chiasm volume (OCV) and establish the relationship of OCV with process speed index at 12 months post-injury. Process speed index is derived from Wechsler Adult Intelligence Scale IV.MethodsThorough cross-sectional and longitudinal analyses were executed, involving 42 patients with moderate to severe TBI and 35 healthy controls. OCV was acquired at 3, 6, and 12 months post-injury using T1-weighted images. OCV of healthy controls and that of patients with TBI at 3, 6, and 12 months post-injury were compared using a Mann-Whitney U test. A multiple linear regression model was constructed to assess the association between OCV and PSI and to predict PSI at 12 months post-injury using OCV at 3 months post-injury.ResultsOCV of patients with TBI was significantly larger compared to healthy controls, persisting from 3 to 12 months post-injury (p < 0.05). This increased OCV negatively correlated with PSI at 12 months post-injury, indicating that larger OCV sizes were associated with decreased PSI (p = 0.031). Furthermore, the multiple linear regression model was significant in predicting PSI at 12 months post-injury utilizing OCV at 3 months post-injury (p = 0.024).ConclusionFor the first time, this study elucidates the increased OCV and the significant association between OCV in sub-chronic stage and PSI at 12 months post-injury, potentially providing clinicians with a tool for anticipatory cognitive rehabilitation strategies following TBI.

VEGF expression disparities in brainstem motor neurons of the SOD1G93A ALS model: Correlations with neuronal vulnerability

Amyotrophic lateral sclerosis (ALS) is a rare neuromuscular disease characterized by severe muscle weakness mainly due to degeneration and death of motor neurons. A peculiarity of the neurodegenerative processes is the variable susceptibility among distinct neuronal populations, exemplified by the contrasting resilience of motor neurons innervating the ocular motor system and the more vulnerable facial and hypoglossal motor neurons. The crucial role of vascular endothelial growth factor (VEGF) as a neuroprotective factor in the nervous system is well-established since a deficit of VEGF has been related to motoneuronal degeneration. In this study, we investigated the survival of ocular, facial, and hypoglossal motor neurons utilizing the murine SOD1G93A ALS model at various stages of the disease. Our primary objective was to determine whether the survival of the different brainstem motor neurons was linked to disparate VEGF expression levels in resilient and susceptible motor neurons throughout neurodegeneration. Our findings revealed a selective loss of motor neurons exclusively within the vulnerable nuclei. Furthermore, a significantly higher level of VEGF was detected in the more resistant motor neurons, the extraocular ones. We also examined whether TDP-43 dynamics in the brainstem motor neuron of SOD mice was altered. Our data suggests that the increased VEGF levels observed in extraocular motor neurons may potentially underlie their resistance during the neurodegenerative processes in ALS in a TDP-43-independent manner. Our work might help to better understand the underlying mechanisms of selective vulnerability of motor neurons in ALS.

Preliminary Baseline Vestibular Ocular Motor Screening Scores in Pediatric Soccer Athletes.

The utility of baseline vestibular and ocular motor screening (VOMS) in high school and collegiate athletes is demonstrated throughout the literature; however, baseline VOMS data at the youth level are limited. In addition, with the recent adoption of the change scoring method, there is a need to document baseline VOMS total and change scores in a pediatric population. To document baseline VOMS total and change scores and to document the internal consistency of the VOMS in pediatric soccer athletes. We hypothesized that the VOMS would demonstrate strong internal consistency in pediatric soccer athletes. Cross-sectional study. Pediatric soccer athletes (N = 110; range = 5-12y) completed the VOMS at baseline. Descriptive statistics summarized demographic information, VOMS total scores, and VOMS change scores. Cronbach α assessed internal consistency for VOMS total scores and change scores. Twenty-one (19.1%) participants had at least one total score above clinical cutoffs (≥2 on any VOMS component and ≥5cm on average near point convergence). Forty (36.4%) participants had at least one change score above clinical cutoffs (≥1 on any VOMS component and ≥3cm on average near point convergence). The internal consistency was strong for total scores with all VOMS components included (Cronbach α = .80) and change scores (Cronbach α = .89). Although results suggest VOMS items measure distinct components of the vestibular and ocular motor systems, caution should be taken when interpreting VOMS total and change scores in pediatric athletes, as overreporting symptoms is common, thereby impacting the false-positive rate.

Usefulness of eye tracking systems in multiple sclerosis

Multiple sclerosis (MS) is a chronic disease of the central nervous system characterized by inflammation and neurodegeneration. It represents the leading cause of nontraumatic disability in young adults in many places around the world.Currently, for the objective quantification of the damage of the visual pathway swept‐source OCT (SS‐OCT) is considered the most appropriate technique. Additionally, during the course of the disease multiple neurological deficiencies can appear, including eye motility disorders.Patients may develop various ocular motor disorders (OMDs) affecting visual function and significantly increasing disability. These alterations involve visual function and may decrease quality of life perceived by patients because they affect, among other functions, reading capability.OMDs, can be analysed by several recording systems, although they have not been incorporated into the practice routine clinic due to its complexity, high costs and also because the value of these alterations is probably not known.It is possible that an accurate examination of motility eye, may have a substantial impact on the diagnosis and management of those patients. OMDs has been suggested as potential biomarker of early neurological deterioration and its evaluation could contribute to obtaining progression and response to treatments, facilitating translational development of so‐called precision medicine.Eye trackers are state‐of‐the‐art tools that can obtain valuable information of OMDs in neurological degenerations. In MS, oculomotor alterations as saccadic dysmetria, saccadic intrusions, nystagmus, fixational deficits, smooth pursuit impairment, skew deviation, optokinetic and vestibulo‐ocular reflex impairments, may go unnoticed because systematic examination of the oculomotor systems do not use routinely these techniques.As mentioned, objective recordings of eye movements through eye‐tracking systems are not currently performed widely, despite that they have been described as an important adjunct in diagnosis, documentation, and management of different neurologic conditions.In addition, eye tracking is also a capable method to investigate the relationship between behaviour and neural mechanisms. Eye motion recordings provide a measure of functional preservation of the nervous system, which should be recognized to be of significant importance in assessing a disease in which disability is manifested by disruption of normal neuronal functions.In fact, it has been described that eye tracking tasks (especially saccadic tasks) are often used as an adjunct to traditional scales for cognitive assessment. In addition, eye tracking data confirmed that MS is characterized by attention deficits.In conclusion, there is a growing interest in the use of eye tracking systems as biomarkers for MS. Specifically in this work we have analysed a large series MS patients to detect if any of the anomalies that patients refer to, such as reading difficulties, are related to disorders of the ocular motor systems.

Poster Session I: Dissociation of torsional eye movements and perception during optokinetic stimulation by visual cues of gravity.

An optokinetic stimulus rotating about the naso-occipital axis drives torsional eye movements and causes a bias in perception of upright measured with a subjective visual vertical (SVV) task. In addition, a static image with tilted visual cues of gravity orientation will induce optostatic torsion and biases SVV. We posit that a visual gravity cue provided by a frame combined with a torsional optokinetic stimulus would increase measured torsion and further bias SVV. We use a VR headset with eye-tracking to place the subject in a virtual room with circles forming either a rectangular room (frame condition) or a tubular room (no-frame condition). We place a fixation point at the center of the room while the subject performs a SVV task. The room either rotates about the naso-occipital axis at 0.05 Hz, 0.1 Hz, or 0.2 Hz, with an amplitude of ±20°, or has a static tilt of 0° or ±30°. Static frame conditions had the expected bias of SVV and optostatic torsion compared to the control no-frame condition. In sinusoidal rotation conditions, for SVV, there was a significant difference in the amplitude of the response between the frame (5.4 ± 2.6°; mean ± std) and no-frame (3.0 ± 1.3°) condition, while there was no significant difference for torsion, frame (0.8 ± 0.6°) and no-frame (0.7 ± 0.6°). Our results indicate that while perception integrates a moving visual cue into its estimation of upright orientation, the ocular motor system is only affected by those cues when they are static.

P071 Simple Vestibular-Occular Motor Assessment as a Predictor of Driving Performance Vulnerability following extended Wakefulness

Abstract Introduction Driver fatigue is a significant contributor to road crashes, but identifying individuals at driving risk is challenging. We examined the potential of simple baseline vestibular ocular motor system (VOMS) assessment via virtual reality goggles to predict subsequent vulnerability to driving simulator impairment following extended wakefulness. Methods 49 individuals (Mean±SD Age 32.6±12.9, 45% Males) underwent 9hr baseline sleep opportunity followed by approximately ~29hrs extended wakefulness with five 60min driving assessments. Cluster analysis classified drivers into vulnerable (n=17) or resistant (n=32) groups based on their worst steering deviation and number of crashes from driving tests. Baseline VOMS were performed ~10mins prior to the first three drives (1, 7 and 13hrs of wakefulness). XGBoost machine learning model was trained using baseline VOMs features to predict vulnerable vs resistant groups from driving tests 4 and 5 (19 and 25hrs of wakefulness) Model performance was evaluated using 5-fold cross-validation approach using ROC analysis. Results XGBoost machine learning ranked all 70 VOMS metrics on their importance in predicting vulnerable vs resistant groups. Top 10 VOMs metrics assessed during baseline non-sleep deprived tests demonstrated a strong ability to predict the driver's performance following extended wakefulness, differentiating between the vulnerable vs resistant groups (AUC 0.73 [95%CI 0.61-0.83, p&amp;lt;0.001]). Conclusion VOMs tests conducted at baseline holds promise for predicting future driving impairment. This approach has the potential to be highly valuable in determining an individual's fitness to drive. Future validation in independent samples, sleep disordered population and in-field on-road testing are needed to confirm these promising findings.

O072 Simple Vestibular-Occular Motor Assessment as a Predictor of Alertness State and Driving Impairment during Extended Wakefulness

Abstract Introduction Driver fatigue contributes to 2-16% of road crashes, highlighting the need for improved detection of at-risk drivers. We used a novel and brief test of vestibular ocular motor system (VOMS) assessed via virtual reality goggles to predict alertness state and driving simulator performance during 29hr extended wakefulness. Methods 49 individuals (Mean±SD Age, 32.6±12.9, 45% Males) undergone 9hr baseline sleep opportunity followed by ~29hrs extended wakefulness with five 60min driving assessments. Cluster analysis, combining steering deviation and number of crashes were used to split participants into groups of either poor vs good driving performance. VOMS assessment was conducted using virtual reality goggles approximately 10mins before and after each drive. Predictive importance of VOMs metrics were ranked using XGBoost machine learning model, which was then utilized to distinguish between poor vs good driving groups. Model performance was evaluated using a 5-fold cross-validation approach using ROC analysis. Results XGBoost machine learning ranked all 70 VOMS metrics on their importance in predicting driving performance group for each drive. Top 10 metrics from pre-drive VOMS test predicted both daytime driving (tests 1-3, AUC 0.8 [95%CI 0.64-0.93], p&amp;lt;0.001) and night-time driving (tests 4-5, AUC 0.78 [95%CI 0.6-0.95, p&amp;lt;0.001]). Post-driving VOMS assessments also predicted daytime (AUC 0.74 [95%CI 0.53-0.9, p&amp;lt;0.001] and night-time driving (AUC 0.76 [95%CI 0.52-0.94, p&amp;lt;0.001]). Conclusion VOMS assessment show promise as a short and effective assessment of sleepiness to predict driving failure. Future validation in independent samples, sleep disordered population and in-field on-road testing are needed to confirm these promising findings.

EXAMINATION OF THE CONTROL SYSTEM OF AN ARTIFICIAL EYE IMPLANT

Due to various reasons, a person who is missing one eye may experience psychological as well as excruciating suffering. Enucleation and evisceration surgery are the most often used methods to remove a sick or injured eye. The patient is often fitted with a bespoke implant into the orbital tissues after the surgeon removes the eye. In order to keep the socket from looking hollow and depressed, this replaces volume. Once the socket has stabilized, a prosthetic shell—also known as an artificial eye, glass eye, or ocular prosthesis—is placed within. An ocular implant can mechanically replace the lost eye. There have been significant developments in this field. To replace the missing eye, an ocular prosthesis was developed. Physically, the prosthetic seems natural. The eye, however, is stationary or just slightly mobile. development of an independent ocular motor system is the objective of this study in order to give the artificial eye more realistic movement. The detection of natural eye movement is a crucial issue. This study includes an overview of eye movement detecting techniques. Then eye movement detection using the fusion approach is created. The first aspect that is recorded and stored is the eye movement. Then, during the experiment, the sensor array yields the eye movement signal, and the matching rule yields the eye position. The experimental system, fusion technology, and early findings are covered in the majority of this work. Keywords: Sensor array, fusion, artificial eye, orbital implant, and ocular control.

What Is a Preferred Retinal Locus?

This review examines the concept of the preferred retinal locus (PRL) in patients with macular diseases. Considering monocular and binocular viewing, we (a) explain how to identify the PRL and discuss the pitfalls associated with its measurement, (b) review the current hypotheses for PRL development, (c) assess whether the PRL is the new reference point of the ocular motor system, and discuss (d) the functional and (e) the clinical implications of the PRL. We conclude that the current definition of the PRL is probably incomplete and should incorporate the need to evaluate the PRL in the framework of binocular viewing. We emphasize the need for more research.

Profiling Vestibular Evoked Myogenic Potentials Findings in Cerebellar Disorders

Cerebellar dizziness is a common clinical sign in patients with cerebellar dysfunction with several multifaceted consequences in the life of an individual. The clinical diagnosis of this type of dizziness is delayed or overlooked as its frequency is underestimated. Inaccurate examination of the vestibular or ocular motor systems contributes to this effect. However, with expansion of use of ocular vestibular evoked myogenic potentials (oVEMPs) in the diagnosis of central disorders, makes it an important tool used in routine practice. The present study shows that oVEMP is majorly affected in various cerebellar disorders, making it a sensitive test to be used in suspected patients. Based on the vestibular evoked myogenic potential results and complete audiological profile in the patients with cerebellar demyelination and cerebellar atrophy, medical team was able to arrive at a diagnosis when the radiological findings were inconclusive. This study shows that oVEMPs are neurological responses, sensitive to cerebellar dysfunction.

Reorganization of sensory networks after subcortical vestibular infarcts: A longitudinal symptom-related voxel-based morphometry study.

We aimed to delineate common principles of reorganization after infarcts of the subcortical vestibular circuitry related to the clinical symptomatology. Our hypothesis was that the recovery of specific symptoms is associated with changes in distinct regions within the core vestibular, somatosensory, and visual cortical and subcortical networks. We used voxel- and surface-based morphometry to investigate structural reorganization of subcortical and cortical brain areas in 42 patients with a unilateral, subcortical infarct with vestibular and ocular motor deficits in the acute phase. The patients received structural neuroimaging and clinical monitoring twice (acute phase and after 6months) to detect within-subject changes over time. In patients with vestibular signs such as tilts of the subjective visual vertical (SVV) and ocular torsion in the acute phase, significant volumetric increases in the superficial white matter around the parieto-opercular (retro-)insular vestibular cortex (PIVC) were found at follow-up. In patients with SVV tilts, spontaneous nystagmus, and rotatory vertigo in the acute phase, gray matter volume decreases were located in the cerebellum and the visual cortex bilaterally at follow-up. Patients with saccade pathology demonstrated volumetric decreases in cerebellar, thalamic, and cortical centers for ocular motor control. The findings support the role of the PIVC as the key hub for vestibular processing and reorganization. The volumetric decreases represent the reciprocal interaction of the vestibular, visual, and ocular motor systems during self-location and egomotion detection. A modulation in vestibular and ocular motor as well as visual networks was induced independently of the vestibular lesion site.

An Eye on Movement Disorders.

Eye disorders spanning a range of ocular tissue are common in patients with movement disorders. Highlighting these ocular manifestations will benefit patients and may even aid in diagnosis. In this educational review we outline the anatomy and function of the ocular tissues with a focus on the tissues most affected in movement disorders. We review the movement disorders associated with ocular pathology and where possible explore the underlying cellular basis thought to be driving the pathology and provide a brief overview of ophthalmic investigations available to the neurologist. This review does not cover intracranial primary visual pathways, higher visual function, or the ocular motor system.

The Rac-GAP alpha2-Chimaerin Signals via CRMP2 and Stathmins in the Development of the Ocular Motor System.

A precise sequence of axon guidance events is required for the development of the ocular motor system. Three cranial nerves grow toward, and connect with, six extraocular muscles in a stereotyped pattern, to control eye movements. The signaling protein alpha2-chimaerin (α2-CHN) plays a pivotal role in the formation of the ocular motor system; mutations in CHN1, encoding α2-CHN, cause the human eye movement disorder Duane Retraction Syndrome (DRS). Our research has demonstrated that the manipulation of α2-chn signaling in the zebrafish embryo leads to ocular motor axon wiring defects, although the signaling cascades regulated by α2-chn remain poorly understood. Here, we demonstrate that several cytoskeletal regulatory proteins-collapsin response mediator protein 2 (CRMP2; encoded by the gene dpysl2), stathmin1, and stathmin 2-bind to α2-CHN. dpysl2, stathmin1, and especially stathmin2 are expressed by ocular motor neurons. We find that the manipulation of dpysl2 and of stathmins in zebrafish larvae leads to defects in both the axon wiring of the ocular motor system and the optokinetic reflex, impairing horizontal eye movements. Knockdowns of these molecules in zebrafish larvae of either sex caused axon guidance phenotypes that included defasciculation and ectopic branching; in some cases, these phenotypes were reminiscent of DRS. chn1 knock-down phenotypes were rescued by the overexpression of CRMP2 and STMN1, suggesting that these proteins act in the same signaling pathway. These findings suggest that CRMP2 and stathmins signal downstream of α2-CHN to orchestrate ocular motor axon guidance and to control eye movements.SIGNIFICANCE STATEMENT The precise control of eye movements is crucial for the life of vertebrate animals, including humans. In humans, this control depends on the arrangement of nerve wiring of the ocular motor system, composed of three nerves and six muscles, a system that is conserved across vertebrate phyla. Mutations in the protein alpha2-chimaerin have previously been shown to cause eye movement disorders (squint) and axon wiring defects in humans. Our recent work has unraveled how alpha2-chimaerin coordinates axon guidance of the ocular motor system in animal models. In this article, we demonstrate key roles for the proteins CRMP2 and stathmin 1/2 in the signaling pathway orchestrated by alpha2-chimaerin, potentially giving insight into the etiology of eye movement disorders in humans.

Childhood Onset Strabismus: A Neurotrophic Factor Hypothesis

ABSTRACT Strabismus is a genetically heterogeneous disorder with complex molecular and neurophysiological causes. Evidence in the literature suggests a strong role for motor innervation in the etiology of strabismus, which connects central neural processes to the peripheral extraocular muscles. Current treatments of strabismus through surgery show that an inherent sensorimotor plasticity in the ocular motor system decreases the effectiveness of treatment, often driving eye alignment back toward its misaligned pre-surgical state by altering extraocular muscle tonus. There is recent interest in capitalizing on existing biological processes in extraocular muscles to overcome these compensatory mechanisms. Neurotrophins are trophic factors that regulate survival and development in neurons and muscle, including extraocular muscles. Local administration of neurotrophins to extraocular muscles partially reversed strabismus in an animal model of strabismus. The hypothesis is that sustained release of neurotrophins gives more time for the ocular motor system to adapt to a slow change in alignment in the desired direction. The effect of neurotrophins on extraocular muscles is complex, as different neurotrophic factors have diverse effects on extraocular muscle contraction profiles, patterns of innervation, and density of extraocular muscle precursor cells. Neurotrophic factors show promise as a therapeutic option for strabismus, which may help to improve treatment outcomes and offset devastating amblyopia and psychosocial effects of disease in strabismus patients.

Effects of vestibular spontaneous nystagmus on visual smooth pursuit function

Objective: The aim of the study is to analyze the effects of vestibular spontaneous nystagmus(SN) on the smooth pursuit function of visual ocularmotor system. Methods: A total of 46 patients with acute unilateral peripheral vestibular syndrome with SN (26 cases of vestibular neuritis, 6 cases of Ramsay Hunt Syndrome (RHS) with vertigo, 14 cases of sudden deafness with vertigo) were included in this work. In the study group, the results of SPT and SN test with videonystagmography(VNG) were also reviewed. Taking SPT parameters, the influence of SN intensity on SPT gain, asymmetry and waveform and their correlation were analyzed.SPSS19.0 software was used for statistical analysis. Results: Among the 46 patients, there were 36 cases of SN pointing to the healthy side(SN intensity range of 2.68°/s-32.53°/s), and 10 cases of SN pointing to the affected side (SN intensity range of 2.66°/s-16.54°/s). SN intensity was divided into 3 groups, including light(0.50°/s-5.00°/s), medium(5.01°/s-10.00°/s) and strong(>10.01°/s), accounting for 14 cases(30.4%), 18 cases(39.1%) and 14 cases(30.4%), respectively. The differences of the gain of SPT to the fast phase and slow phase direction in the overall groups and light, medium and strong groups of SN intensity respectively were statistically significant(ttotal=13.338, tlight=6.184, tmedium=8.436, tstrong=8.477, all of P<0.001). The difference of SPT gain in SN fast phase direction between groups with different SN intensity was statistically significant(F=9.639, P<0.001),there was no statistically significant difference in SPT gain between the groups on the SN slow phase direction(F=1.137, P=0.330).The SN intensity significantly negatively correlated with the SPT gain of the fast phase direction of SN (r=-0.433, P=0.003), that was, the SPT gain on the fast phase direction of SN decreased with the increase of SN intensity. There was no significant correlation between SN intensity and the gain of SPT on the slow phase direction of SN (r=-0.061, P=0.687). SPT waveform analysis showed that type I, type II and type III accounted for 8 cases(17.4%), 21 cases(45.6%) and 17 cases(37.0%), respectively. The corresponding mean values of SN intensity were (3.71±0.69)°/s, (7.44±1.88)°/s, (20.04±5.53)°/s, respectively, without type IV wave. The intensity of SN was positively correlated with the asymmetric value of the gain of SPT left and right(r=0.450,P=0.002). That was, with the increase of SN strength, the asymmetric value also increased, and the worse the asymmetry of the gain of SPT left and right pursuit was, the worse the SPT waveform was. Conclusion: SPT gain, asymmetry and SPT waveforms are all affected by SN, and the greater the intensity of SN, the greater the influence on the three. When SN is strong, type III waves may occur, suggesting that acute peripheral vestibular syndrome can also affect the visual ocularmotor systems.

Diagnosis and Differential Diagnosis of Peripheral and Central Vestibular Disorders

The diagnosis of the various peripheral and central vestibular disorders is mainly based on the patient history (time course, type of symptoms, modulating factors, and accompanying symptoms) and a systematic clinical examination of the vestibular, ocular motor, and cerebellar systems (examination for nystagmus, head impulse test, positional maneuvers, Romberg test and examination for central ocular motor signs). The two most important laboratory tests are the "video-head impulse test" and caloric irrigation. Fortunately, the diagnosis of vestibular disorders has become easier and more precise as a result of the very clinically oriented diagnostic criteria of the Bárány Society (www.jvr-web.org/ICVD.html).

The complexity of eye-hand coordination: a perspective on cortico-cerebellar cooperation

BackgroundEye–hand coordination (EHC) is a sophisticated act that requires interconnected processes governing synchronization of ocular and manual motor systems. Precise, timely and skillful movements such as reaching for and grasping small objects depend on the acquisition of high-quality visual information about the environment and simultaneous eye and hand control. Multiple areas in the brainstem and cerebellum, as well as some frontal and parietal structures, have critical roles in the control of eye movements and their coordination with the head. Although both cortex and cerebellum contribute critical elements to normal eye-hand function, differences in these contributions suggest that there may be separable deficits following injury.MethodAs a preliminary assessment for this perspective, we compared eye and hand-movement control in a patient with cortical stroke relative to a patient with cerebellar stroke.ResultWe found the onset of eye and hand movements to be temporally decoupled, with significant decoupling variance in the patient with cerebellar stroke. In contrast, the patient with cortical stroke displayed increased hand spatial errors and less significant temporal decoupling variance. Increased decoupling variance in the patient with cerebellar stroke was primarily due to unstable timing of rapid eye movements, saccades.ConclusionThese findings highlight a perspective in which facets of eye-hand dyscoordination are dependent on lesion location and may or may not cooperate to varying degrees. Broadly speaking, the results corroborate the general notion that the cerebellum is instrumental to the process of temporal prediction for eye and hand movements, while the cortex is instrumental to the process of spatial prediction, both of which are critical aspects of functional movement control.

Hyperventilation Increases the Randomness of Ocular Palatal Tremor Waveforms.

Hyperventilation changes the extracellular pH modulating many central pathologies, such as tremor. The questions that remain unanswered are the following: (1) Hyperventilation modulates which aspects of the oscillations? (2) Whether the effects of hyperventilation are instantaneous and the recovery is rapid and complete? Here we study the effects of hyperventilation on eye oscillations in the syndrome of oculopalatal tremor (OPT), a disease model affecting the inferior olive and cerebellar system. These regions are commonly involved in the pathogenesis of many movement disorders. The focus on the ocular motor system also allows access to the well-known physiology and precise measurement techniques. We found that hyperventilation causes modest but insignificant changes in the intensity of oscillation displacement (i.e., how large the eye excursions are) and velocity (i.e., how fast do the eyes move during oscillations). We found the robust increase in the randomness of the oscillatory waveform during hyperventilation and it instantaneously reverts to the baseline after hyperventilation. The subsequent analysis classified the oscillations according to their waveform shape and randomness into different clusters. The hyperventilation substantially changed the cluster type in 60% of the subjects, but it reverted to the pre-hyperventilation cluster at the conclusion of the hyperventilation. In summary, hyperventilation instantaneously affects the randomness of the oscillatory waveforms but there are less substantial effects on the intensity. The deficits reverse immediately at the end of the hyperventilation.

Dizziness and Vertigo: The Skillful Examination

The visual, ocular motor and vestibular systems have intimate neural and close anatomical relationship that dictates their assessment in a patient with dizziness and vertigo. Recognition of the pearls and pitfalls of a targeted clinical examination HINTS/HINTS "Plus" allows the clinician to probe at the bedside the most crucial hypothesis in a patient with acute isolated vestibular syndrome, "Is this a stroke?" By applying a methodical approach to examination of patients with dizziness and vertigo, localization of the offending lesion, management, and even elucidation of the underlying diagnosis is feasible.

The effect of an interval fatigue protocol on Vestibular/Ocular Motor Screening (VOMS) performance

ABSTRACTObjective: The purpose of this study was to examine the effect of a fatigue protocol on Vestibular/Ocular Motor Screening (VOMS) performance.Design: Within subjects, repeated measures, crossover.Methods: Fifteen healthy, physically-active participants (22.20 ± 1.424 years) completed 2 sessions under 2 conditions. A pretest VOMS, condition protocol, and a posttest VOMSwere performed. The control condition consisted of rest, while the experimental consisted of a fatigue protocol.Results: The primary outcome measures were VOMS performance scores and Near Point of Convergence (NPC) measurements. Statistically significant interaction effects for NPC, F(1,14) = 9.38, p = .008, and total VOMS score, F(1,14) = 10.96, p = .005 were observed. For NPC, posttest (9.12 ± 4.99 cm) was significantly different, t(14) = −2.60, p = .021, than pretest scores (7.12 ± 3.19 cm). For total VOMS score, posttest experimental scores (4.93 ± 5.12) were significantly different, t(14) = −3.06, p = .009, than pretest severity scores (1.73 ± 3.67).Conclusions: Significant increases were found in total VOMS and NPC scores following exertional fatigue. Exertional fatigue affects symptoms associated with vestibular, and/or ocular motor system assessments. Clinicians should use the VOMS with caution immediately following activity and allow time for recovery from acute fatigue.