Temporal Changes in Fixational Eye Movements After Concussion in Adolescents and Adults: Preliminary Findings

Concussions often involve ocular impairment and symptoms such as convergence insufficiency, accommodative insufficiency, blurred vision, diplopia, eye strain, and pain. Current clinical assessments of ocular function and symptoms rely on subjective symptom reporting and/or involve lengthy administration time. More objective, brief assessments of ocular function following concussion are warranted. The purpose of this study was to evaluate changes in fixational eye movements (FEMs) and their association with clinical outcomes including recovery time, symptoms, cognitive and vestibular/ocular motor impairment. Thirty-three athletes (13-27 years of age; 54.5% female) within 21 days of a diagnosed concussion participated in the study. A tracking scanning laser ophthalmoscope (TSLO) evaluated FEMs metrics during fixation on a center and corner target. Participants completed symptom (Post-Concussion Symptom Scale [PCSS]), cognitive (Immediate Post-concussion Assessment and Cognitive Testing [ImPACT], and Vestibular/Ocular Motor Screening (VOMS) evaluations. All measures were administered at the initial visit and following medical clearance, which was defined as clinical recovery. Changes in FEMs were calculated using paired-samples t tests. Linear regression (LR) models were used to evaluate the association of FEMs with clinical recovery. Pearson product-moment correlations were used to evaluate the associations among FEMs and clinical outcomes. On the center task, changes across time were supported for average microsaccade amplitude (p = 0.005; Cohen's d = 0.53), peak velocity of microsaccades (p = 0.01; d = 0.48), peak acceleration of microsaccades (p = 0.02; d = 0.48), duration of microsaccade (p < 0.001; d = 0.72), and drift vertical (p = 0.017; d = -0.154). The LR model for clinical recovery was significant (R2 = 0.37; p = 0.023) and retained average instantaneous drift amplitude (β = 0.547) and peak acceleration of microsaccade (β = 0.414). On the corner task, changes across time were supported for drift proportion (p = 0.03; d = 0.43). The LR model to predict clinical recovery was significant (R2 = 0.85; p = 0.004) and retained average amplitude of microsaccades (β = 2.66), peak velocity of microsaccades (β = -15.11), peak acceleration of microsaccades (β = 12.56), drift horizontal (β = 7.95), drift vertical (β = 1.29), drift amplitude (β = -8.34), drift proportion (β = 0.584), instantaneous drift direction (β = -0.26), and instantaneous drift amplitude (β = 0.819). FEMs metrics were also associated with reports of nausea and performance within the domain of visual memory. The FEMs metric were also associated with PCSS, ImPACT, and VOMS clinical concussion outcomes, with the highest magnitude correlations between average saccade amplitude and VOMS symptoms of nausea and average instantaneous drift speed and ImPACT visual memory, respectively. FEMs metrics changed across time following concussion, were useful in predicting clinical recovery, and were correlated with clinical outcomes. FEMs measurements may provide objective data to augment clinical assessments and inform prognosis following this injury.

Inborn Errors of Metabolism with Ataxia: Current and Future Treatment Options

A number of hereditary ataxias are caused by inborn errors of metabolism (IEM), most of which are highly heterogeneous in their clinical presentation. Prompt diagnosis is important because disease-specific therapies may be available. In this review, we offer a comprehensive overview of metabolic ataxias summarized by disease, highlighting novel clinical trials and emerging therapies with a particular emphasis on first-in-human gene therapies. We present disease-specific treatments if they exist and review the current evidence for symptomatic treatments of these highly heterogeneous diseases (where cerebellar ataxia is part of their phenotype) that aim to improve the disease burden and enhance quality of life. In general, a multimodal and holistic approach to the treatment of cerebellar ataxia, irrespective of etiology, is necessary to offer the best medical care. Physical therapy and speech and occupational therapy are obligatory. Genetic counseling is essential for making informed decisions about family planning.

Association of Multidomain Assessment Outcomes with Referral for Vestibular Therapy following Concussion

CONTEXT

Multiple aspects of a multidomain assessment have been validated for identifying concussion, however, researchers have yet to determine which components are related to referral for vestibular therapy.

OBJECTIVE

To identify which variables from a multidomain assessment were associated with receiving a referral for vestibular therapy following a concussion.

DESIGN

Retrospective chart review, level of evidence 3.

PATIENTS OR OTHER PARTICIPANTS

Participants (n=331; age: 16.9±7.2; 39.3% female) were diagnosed with a concussion per international consensus criteria by a clinical neuropsychologist after presenting to a concussion specialty clinic.

MAIN OUTCOME MEASURES

Medical chart data was extracted from the first clinical visit regarding pre-injury medical history, computerized neurocognition, Post-Concussion Symptom Scale (PCSS), Concussion Clinical Profiles Screen (CP-Screen) and Vestibular Ocular Motor Screening (VOMS) within 16.2±46.7 days of injury. Five backwards logistic regression models were built to associate the outcomes from each of the five included assessments with referral for vestibular therapy. A final logistic regression model was built using variables retained in the previous five models as potential predictors of referral for vestibular therapy.

RESULTS

The five models built from individual components of the multidomain assessment predicted referral for vestibular therapy (R2= 0.01-0.28) with 1 to 6 statistically significant variables. The final multivariate model (R2= 0.40) retained 9 significant variables, represented by each of the five multidomain assessments except neurocognition. Variables with the strongest association to vestibular therapy referral were motor vehicle accident mechanism of injury (odds ratio [OR]=15.45), migraine history (OR=3.25), increased headache when concentrating (OR=1.81) and horizontal vestibular ocular reflex (OR=1.63).

CONCLUSIONS

The present study demonstrates the utility of a multidomain assessment, and identifies outcomes associated with a referral for vestibular therapy following a concussion.

A window into eye movement dysfunction following mTBI: A scoping review of magnetic resonance imaging and eye tracking findings

Mild traumatic brain injury (mTBI), commonly known as concussion, is a complex neurobehavioral phenomenon affecting six in 1000 people globally each year. Symptoms last between days and years as microstructural damage to axons and neurometabolic changes result in brain network disruption. There is no clinically available objective biomarker to diagnose the severity of injury or monitor recovery. However, emerging evidence suggests eye movement dysfunction (e.g., saccades and smooth pursuits) in patients with mTBI. Patients with a higher symptom burden and prolonged recovery time following injury may show higher degrees of eye movement dysfunction. Likewise, recent advances in magnetic resonance imaging (MRI) have revealed both white matter tract damage and functional network alterations in mTBI patients, which involve areas responsible for the ocular motor control. This scoping review is presented in three sections: Section 1 explores the anatomical control of eye movements to aid the reader with interpreting the discussion in subsequent sections. Section 2 examines the relationship between abnormal MRI findings and eye tracking after mTBI based on the available evidence. Finally, Section 3 communicates gaps in our knowledge about MRI and eye tracking, which should be addressed in order to substantiate this emerging field.

Working Memory Phenotypes in Early Multiple Sclerosis: Appraisal of Phenotype Frequency, Progression and Test Sensitivity

Working memory (WM) impairments are common and debilitating symptoms of multiple sclerosis (MS), often emerging early in the disease. Predominantly, WM impairments are considered in a binary manner, with patients considered either impaired or not based on a single test. However, WM is comprised of different activated subcomponents depending upon the type of information (auditory, visual) and integration requirements. As such, unique WM impairment phenotypes occur. We aimed to determine the most frequent WM phenotypes in early MS, how they progress and which WM test(s) provide the best measure of WM impairment. A total of 88 participants (63 early relapsing–remitting MS: RRMS, 25 healthy controls) completed five WM tests (visual–spatial, auditory, episodic, executive) as well as the symbol digit modalities test as a measure of processing speed. RRMS patients were followed-up for two years. Factors affecting WM (age/gender/intelligence/mood) and MS factors (disease duration/disability) were also evaluated. Some 61.9% of RRMS patients were impaired on at least one WM subcomponent. The most subcomponents impaired were visual,–spatial and auditory WM. The most common WM phenotypes were; (1) visual–spatial sketchpad + episodic buffer + phonological loop + central executive, (2) visual–spatial sketchpad + central executive. The test of visual–spatial WM provided the best diagnostic accuracy for detecting WM impairment and progression. The SDMT did not achieve diagnostic accuracy greater than chance. Although this may be unsurprising, given that the SDMT is a measure of cognitive processing speed in MS, this does highlight the limitation of the SDMT as a general screening tool for cognitive impairment in early MS.

Detecting Cognitive Impairment in Idiopathic Intracranial Hypertension Using Ocular Motor and Neuropsychological Testing

Objective: To determine whether cognitive impairments in patients with Idiopathic Intracranial Hypertension (IIH) are correlated with changes in visual processing, weight, waist circumference, mood or headache, and whether they change over time.

Methods: Twenty-two newly diagnosed IIH patients participated, with a subset assessed longitudinally at 3 and 6 months. Both conventional and novel ocular motor tests of cognition were included: Symbol Digit Modalities Test (SDMT), Stroop Colour and Word Test (SCWT), Digit Span, California Verbal Learning Test (CVLT), prosaccade (PS) task, antisaccade (AS) task, interleaved antisaccade-prosaccade (AS-PS) task. Patients also completed headache, mood, and visual functioning questionnaires.

Results: IIH patients performed more poorly than controls on the SDMT (p< 0.001), SCWT (p = 0.021), Digit Span test (p< 0.001) and CVLT (p = 0.004) at baseline, and generated a higher proportion of AS errors in both the AS (p< 0.001) and AS-PS tasks (p = 0.007). Further, IIH patients exhibited prolonged latencies on the cognitively complex AS-PS task (p = 0.034). While weight, waist circumference, headache and mood did not predict performance on any experimental measure, increased retinal nerve fibre layer (RNFL) was associated with AS error rate on both the block [F_{(3, 19)}=3.22, B = 0.30, p = 0.022] and AS-PS task [F_{(3, 20)} = 2.65, B = 0.363, p = 0.013]. Unlike ocular motor changes, impairments revealed on conventional tests of cognition persisted up to 6 months.

Conclusion: We found multi-domain cognitive impairments in IIH patients that were unrelated to clinical characteristics. Marked ocular motor inhibitory control deficits were predicted by RNFL thickness but remained distinct from other cognitive changes, underscoring the significance of visual processing changes in IIH.

Ocular Motor Abnormalities in Anti-IgLON5 Disease

Objective

Anti-IgLON5 disease forms an interface between neuroinflammation and neurodegeneration and includes clinical phenotypes that are often similar to those of neurodegenerative diseases. An early diagnosis of patients with anti-IgLON5 disease and differentiation from neurodegenerative diseases is necessary and may have therapeutic implications.

Methods

In our small sample size study we investigated oculomotor function as a differentiating factor between anti-IgLON5 disease and neurodegenerative disorders. We examined ocular motor and vestibular function in four patients suffering from anti-IgLON5 disease using video-oculography (VOG) and a computer-controlled rotational chair system (sampling rate 60 Hz) and compared the data with those from ten age-matched patients suffering from progressive supranuclear palsy (PSP) and healthy controls (CON).

Results

Patients suffering from anti-IgLON5 disease differed from PSP most strikingly in terms of saccade velocity and accuracy, the presence of square wave jerks (SWJ) (anti-IgLON5 0/4 vs. PSP 9/10) and the clinical finding of supranuclear gaze palsy (anti-IgLON5 1/4). The presence of nystagmus, analysis of smooth pursuit eye movements, VOR and VOR suppression was reliable to differentiate between the two disease entities. Clear differences in all parameters, although not always significant, were found between all patients and CON.

Discussion

We conclude that the use of VOG as a tool for clinical neurophysiological assessment can be helpful in differentiating between patients with PSP and patients with anti-IgLON5 disease. VOG could have particular value in patients with suspected PSP and lack of typical Parkinson’s characteristics. future trials are indispensable to assess the potential of oculomotor function as a biomarker in anti-IgLON5 disease.

Delayed Onset of Inhibition of Return in Visual Snow Syndrome

Visual snow syndrome (VSS) is a complex, sensory processing disorder. We have previously shown that visual processing changes manifest in significantly faster eye movements toward a suddenly appearing visual stimulus and difficulty inhibiting an eye movement toward a non-target visual stimulus. We propose that these changes reflect poor attentional control and occur whether attention is directed exogenously by a suddenly appearing event, or endogenously as a function of manipulating expectation surrounding an upcoming event. Irrespective of how attention is captured, competing facilitatory and inhibitory processes prioritise sensory information that is important to us, filtering out that which is irrelevant. A well-known feature of this conflict is the alteration to behaviour that accompanies variation in the temporal relationship between competing sensory events that manipulate facilitatory and inhibitory processes. A classic example of this is the “Inhibition of Return” (IOR) phenomenon that describes the relative slowing of a response to a validly cued location compared to invalidly cued location with longer cue/target intervals. This study explored temporal changes in the allocation of attention using an ocular motor version of Posner's IOR paradigm, manipulating attention exogenously by varying the temporal relationship between a non-predictive visual cue and target stimulus. Forty participants with VSS (20 with migraine) and 20 controls participated. Saccades were generated to both validly cued and invalidly cued targets with 67, 150, 300, and 500 ms cue/target intervals. VSS participants demonstrated delayed onset of IOR. Unlike controls, who exhibited IOR with 300 and 500 ms cue/target intervals, VSS participants only exhibited IOR with 500 ms cue/target intervals. These findings provide further evidence that attention is impacted in VSS, manifesting in a distinct saccadic behavioural profile, and delayed onset of IOR. Whether IOR is perceived as the build-up of an inhibitory bias against returning attention to an already inspected location or a consequence of a stronger attentional orienting response elicited by the cue, our results are consistent with the proposal that in VSS, a shift of attention elicits a stronger increase in saccade-related activity than healthy controls. This work provides a more refined saccadic behavioural profile of VSS that can be interrogated further using sophisticated neuroimaging techniques and may, in combination with other saccadic markers, be used to monitor the efficacy of any future treatments.

Fellow Eye Deficits in Amblyopia

Amblyopia is a neurodevelopmental disorder of the visual system, as a result of discordant visual experience during infancy or early childhood. Because amblyopia is typically defined as monocularly reduced visual acuity accompanied by one or more known amblyogenic factors, it is often assumed that the fellow eye is normal and sufficient for tasks like reading and eye-hand coordination. Recent scientific evidence of ocular motor, visual, and visuomotor deficits that are present with fellow eye monocular viewing and with binocular viewing calls this assumption into question. This clinical update reviews the research that has revealed fellow ocular motor and visual deficits and the effect that these deficits have on an amblyopic child's visuomotor and visuocognitive skills. We need to understand how to prevent and rehabilitate the effects of amblyopia not only on the nonpreferred eye but also on the fellow eye.

Multiple sclerosis: Executive dysfunction, task switching and the role of attention

Background

It has been suggested that switching ability might not be affected in multiple sclerosis (MS) as previously thought; however, whether this is true under more ‘real-world’ conditions when asymmetry in task difficulty is present has not been ascertained.

Objective

The objective of this paper is to examine the impact of task difficulty asymmetry on task switching ability in MS.

Method

An ocular motor (OM) paradigm that interleaves the simple task of looking towards a target (prosaccade, PS) with the cognitively more difficult task of looking away from a target (antisaccade, PS) was used. Two switching conditions: (1) PS switch cost, switching to a simple task from a difficult task (PS switch), relative to performing two simple tasks concurrently (PS repeat); (2) AS switch cost, switching to a difficult task from a simple task (AS switch) relative to performing two difficult tasks concurrently (AS repeat). Forty-five relapsing–remitting MS patients and 30 control individuals were compared.

Results

Controls and patients produced a similar magnitude PS switch cost, suggesting that task difficulty asymmetry does not detrimentally impact MS patients when transitioning from a more difficult task to a simpler task. However, MS patients alone found switching from the simpler PS trial to the more difficult AS trial easier (shorter latency and reduced error) than performing two AS trials consecutively (AS switch benefit). Further, MS patients performed significantly more errors than controls when required to repeat the same trial consecutively.

Conclusion

MS patients appear to find the maintenance of task-relevant processes difficult not switching per se, with deficits exacerbated under increased attentional demands.

Reliability and Normative Reference Values for the Vestibular/Ocular Motor Screening (VOMS) Tool in Youth Athletes

BACKGROUND

The Vestibular/Ocular Motor Screening (VOMS) measure is a newly developed vestibular and ocular motor symptom provocation screening tool for sport-related concussions. Baseline data, psychometric properties, and reliability of the VOMS are needed to further understand the applications of this tool, especially in the youth population, where research is scarce.

PURPOSE

To establish normative data and document the internal consistency and false-positive rate of the VOMS in a sample of nonconcussed youth athletes.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

A total of 423 youth athletes (male = 278, female = 145) between the ages of 8 and 14 years completed baseline VOMS screening before the start of their respective sport seasons. Internal consistency was measured with Cronbach α and inter-item correlations.

RESULTS

Approximately 60% of youth athletes reported no symptom provocation on baseline VOMS assessment, with 9% to 13% scoring over the cutoff levels (score of ≥2 for any individual VOMS symptom, near point convergence distance of ≥5 cm). The VOMS displayed a high internal consistency (Cronbach α = .97) at baseline among youth athletes.

CONCLUSION

The current findings provide preliminary support for the implementation of VOMS baseline assessment into clinical practice, due to a high internal consistency, strong relationships between VOMS items, and a low false-positive rate at baseline in youth athletes.

Neurosensory Deficits Vary as a Function of Point of Care in Pediatric Mild Traumatic Brain Injury

Neurosensory abnormalities are frequently observed following pediatric mild traumatic brain injury (pmTBI) and may underlie the expression of several common concussion symptoms and delay recovery. Importantly, active evaluation of neurosensory functioning more closely approximates real-world (e.g., physical and academic) environments that provoke symptom worsening. The current study determined whether symptom provocation (i.e., during neurosensory examination) improved classification accuracy relative to pre-examination symptom levels and whether symptoms varied as a function of point of care. Eighty-one pmTBI were recruited from the pediatric emergency department (PED; n = 40) or outpatient concussion clinic (n = 41), along with matched (age, sex, and education) healthy controls (HC; n = 40). All participants completed a brief (∼ 12 min) standardized neurosensory examination and clinical questionnaires. The magnitude of symptom provocation upon neurosensory examination was significantly higher for concussion clinic than for PED patients. Symptom provocation significantly improved diagnostic classification accuracy relative to pre-examination symptom levels, although the magnitude of improvement was modest, and was greater in the concussion clinic. In contrast, PED patients exhibited worse performance on measures of balance, vision, and oculomotor functioning than the concussion clinic patients, with no differences observed between both samples and HC. Despite modest sample sizes, current findings suggest that point of care represents a critical but highly under-studied variable that may influence outcomes following pmTBI. Studies that rely on recruitment from a single point of care may not generalize to the entire pmTBI population in terms of how neurosensory deficits affect recovery.

Using Acute Performance on a Comprehensive Neurocognitive, Vestibular, and Ocular Motor Assessment Battery to Predict Recovery Duration After Sport-Related Concussions

BACKGROUND

A sport-related concussion (SRC) is a heterogeneous injury that requires a multifaceted and comprehensive approach for diagnosis and management, including symptom reports, vestibular/ocular motor assessments, and neurocognitive testing.

PURPOSE

To determine which acute (eg, within 7 days) vestibular, ocular motor, neurocognitive, and symptom impairments predict the duration of recovery after an SRC.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

Sixty-nine patients with a mean age of 15.3 ± 1.9 years completed a neurocognitive, vestibular/ocular motor, and symptom assessment within 7 days of a diagnosed concussion. Patients were grouped by recovery time: ≤14 days (n = 27, 39.1%), 15-29 days (n = 25, 36.2%), and 30-90 days (n = 17, 24.6%). Multinomial regression was used to identify the best subset of predictors associated with prolonged recovery relative to ≤14 days.

RESULTS

Acute visual motor speed and cognitive-migraine-fatigue symptoms were associated with an increased likelihood of recovery times of 30-90 days and 15-29 days relative to a recovery time of ≤14 days. A model with visual motor speed and cognitive-migraine-fatigue symptoms within the first 7 days of an SRC was 87% accurate at identifying patients with a recovery time of 30-90 days.

CONCLUSION

The current study identified cognitive-migraine-fatigue symptoms and visual motor speed as the most robust predictors of protracted recovery after an SRC according to the Post-concussion Symptom Scale, Immediate Post-concussion Assessment and Cognitive Testing, and Vestibular/Ocular Motor Screening (VOMS). While VOMS components were sensitive in identifying a concussion, they were not robust predictors for recovery. Clinicians may consider particular patterns of performance on clinical measures when providing treatment recommendations and discussing anticipated recovery with patients.

A Positive Vestibular/Ocular Motor Screening (VOMS) Is Associated With Increased Recovery Time After Sports-Related Concussion in Youth and Adolescent Athletes

BACKGROUND

Vestibular and ocular motor impairments are routinely reported in patients with sports-related concussion (SRC) and may result in delayed return to play (RTP). The Vestibular/Ocular Motor Screening (VOMS) assessment has been shown to be consistent and sensitive in identifying concussion when used as part of a comprehensive examination. To what extent these impairments or symptoms are associated with length of recovery is unknown.

PURPOSE

To examine whether symptom provocation or clinical abnormality in specific domains of the VOMS results in protracted recovery (time from SRC to commencement of RTP protocol).

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

A retrospective chart review was conducted of 167 patients (69 girls, 98 boys; mean ± SD age, 15 ± 2 years [range, 11-19 years]) presenting with SRC in 2014. During the initial visit, VOMS was performed in which symptom provocation or clinical abnormality (eg, unsmooth eye movements) was documented by use of a dichotomous scale (0 = not present, 1 = present). The VOMS used in this clinic consisted of smooth pursuits (SMO_PUR), horizontal and vertical saccades (HOR_SAC and VER_SAC), horizontal and vertical vestibular ocular reflex (HOR_VOR and VER_VOR), near point of convergence (NPC), and accommodation (ACCOM). Domains were also categorized into ocular motor (SMO_PUR, HOR_SAC, VER_SAC, NPC, ACCOM) and vestibular (HOR_VOR, VER_VOR). Cox proportional hazard models were used to explore the relationship between the domains and recovery. Alpha was set at P ≤ .05.

RESULTS

Symptom provocation and/or clinical abnormality in all domains except NPC ( P = .107) and ACCOM ( P = .234) delayed recovery (domain, hazard ratio [95% CI]: SMO_PUR, 0.65 [0.47-0.90], P = .009; HOR_SAC, 0.68 [0.50-0.94], P = .018; VER_SAC, 0.55 [0.40-0.75], P < .001; HOR_VOR, 0.68 [0.49-0.94], P = .018; VER_VOR, 0.60 [0.44-0.83], P = .002). The lowest crude hazard ratio was for ocular motor category (0.45 [0.32-0.63], P < .001).

CONCLUSION

These data suggest that symptom provocation/clinical abnormality associated with all domains except NPC and ACCOM can delay recovery after SRC in youth and adolescents. Thus, the VOMS not only may augment current diagnostic tools but also may serve as a predictor of recovery time in patients with SRC. The findings of this study may lead to more effective prognosis of concussion in youth and adolescents.

Validity and Reliability of the Vestibular/Ocular Motor Screening and Associations With Common Concussion Screening Tools

BACKGROUND

Sustaining a concussion commonly results in vestibular impairments that may be associated with balance deficits. To screen for vestibular impairments after a concussion, the Vestibular/Ocular Motor Screening (VOMS) tool was developed. The relationship between the VOMS and other concussion screening tools, such as the Balance Error Scoring System (BESS) and King-Devick (K-D), have not been explored.

HYPOTHESES

(1) VOMS would provide reliable results and not provoke symptoms in healthy adolescents and (2) VOMS test items would measure related aspects of vestibular function that are not measured through the BESS or K-D.

STUDY DESIGN

Cross-sectional, descriptive.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 105 healthy adolescents (53 male, 52 female; mean age, 15.4 years) completed the VOMS, BESS, and K-D tests. A subsample of 21 adolescents (16 male, 5 female; mean age, 15.5 years) completed the VOMS twice.

RESULTS

The median total symptom score for all 7 VOMS items was 0 (0-5). The majority of the individual VOMS test items total symptom scores demonstrated a significant correlation with each other ( rs = 0.25-0.66, P < 0.02). The individual VOMS items did not demonstrate a significant relationship to the BESS or K-D. VOMS items demonstrated high agreement in total symptom scores between testing trials, with near point convergence (NPC) distance demonstrating an intraclass correlation coefficient (ICC) of 0.95 (95% CI, 0.89-0.98; P < 0.001). The MDC95 (minimal detectable change with 95 confidence) for NPC distance was 4 cm.

CONCLUSION

The VOMS did not provoke vestibular symptoms in healthy adolescents. The VOMS items measured unique aspects of vestibular function other than those measured by the BESS or K-D with good reliability.

CLINICAL RELEVANCE

Clinicians should consider implementing the VOMS as part of a comprehensive concussion assessment if vestibular impairment is suspected. If NPC distance is measured twice, a difference of >4 cm would be considered real change outside of measurement error.

Disassociation between brain activation and executive function in fragile X premutation females

Executive dysfunction has been demonstrated among premutation (PM) carriers (55-199 CGG repeats) of the Fragile X mental retardation 1 (FMR1) gene. Further, alterations to neural activation patterns have been reported during memory and comparison based functional magnetic resonance imaging (fMRI) tasks in these carriers. For the first time, the relationships between fMRI neural activation during an interleaved ocular motor prosaccade/antisaccade paradigm, and concurrent task performance (saccade measures of latency, accuracy and error rate) in PM females were examined. Although no differences were found in whole brain activation patterns, regions of interest (ROI) analyses revealed reduced activation in the right ventrolateral prefrontal cortex (VLPFC) during antisaccade trials for PM females. Further, a series of divergent and group specific relationships were found between ROI activation and saccade measures. Specifically, for control females, activation within the right VLPFC and supramarginal gyrus correlated negatively with antisaccade latencies, while for PM females, activation within these regions was found to negatively correlate with antisaccade accuracy and error rate (right VLPFC only). For control females, activation within frontal and supplementary eye fields and bilateral intraparietal sulci correlated with prosaccade latency and accuracy; however, no significant prosaccade correlations were found for PM females. This exploratory study extends previous reports of altered prefrontal neural engagement in PM carriers, and clearly demonstrates dissociation between control and PM females in the transformation of neural activation into overt measures of executive dysfunction. Hum Brain Mapp 38:1056-1067, 2017. © 2016 Wiley Periodicals, Inc.

Saccadic and Postsaccadic Disconjugacy in Zebrafish Larvae Suggests Independent Eye Movement Control

Spontaneous eye movements of zebrafish larvae in the dark consist of centrifugal saccades that move the eyes from a central to an eccentric position and postsaccadic centripetal drifts. In a previous study, we showed that the fitted single-exponential time constants of the postsaccadic drifts are longer in the temporal-to-nasal (T->N) direction than in the nasal-to-temporal (N->T) direction. In the present study, we further report that saccadic peak velocities are higher and saccadic amplitudes are larger in the N->T direction than in the T->N direction. We investigated the underlying mechanism of this ocular disconjugacy in the dark with a top-down approach. A mathematic ocular motor model, including an eye plant, a set of burst neurons and a velocity-to-position neural integrator (VPNI), was built to simulate the typical larval eye movements in the dark. The modeling parameters, such as VPNI time constants, neural impulse signals generated by the burst neurons and time constants of the eye plant, were iteratively adjusted to fit the average saccadic eye movement. These simulations suggest that four pools of burst neurons and four pools of VPNIs are needed to explain the disconjugate eye movements in our results. A premotor mechanism controls the synchronous timing of binocular saccades, but the pools of burst and integrator neurons in zebrafish larvae seem to be different (and maybe separate) for both eyes and horizontal directions, which leads to the observed ocular disconjugacies during saccades and postsaccadic drifts in the dark.

Switching between two targets with non-constant velocity profiles reveals shared internal model of target motion

Several experiments have shown that smooth pursuit and saccades interact while tracking an object moving across the visual scene. It was proposed two decades ago that the amplitude of saccades triggered during smooth pursuit ('catch-up saccades') were corrected by a delayed sensory signal to account for the ongoing target displacement during catch-up saccades. However, recent studies used targets with non-constant velocity profiles and suggested that the correction of catch-up saccade amplitude must be done through an internal model of target motion. It is widely accepted that an internal model of target motion is also used by the central nervous system (CNS) to cancel inherent delays between visual input and smooth pursuit motor output, ensuring accurate tracking of moving targets. Our study proposes a new paradigm in which the target switches unexpectedly from one target with a non-constant periodic velocity profile to another with a non-constant aperiodic velocity profile. Our results confirm the hypothesis that the CNS uses an internal model of target motion to correct catch-up saccade amplitude. In addition, we reconcile the sensory delayed and the internal model of target motion hypotheses and show that a common internal model of target motion is shared within the CNS to control smooth pursuit and to correct catch-up saccade amplitude.

Traumatic brain injury and vestibulo-ocular function: current challenges and future prospects

Normal function of the vestibulo-ocular reflex (VOR) coordinates eye movement with head movement, in order to provide clear vision during motion and maintain balance. VOR is generated within the semicircular canals of the inner ear to elicit compensatory eye movements, which maintain stability of images on the fovea during brief, rapid head motion, otherwise known as gaze stability. Normal VOR function is necessary in carrying out activities of daily living (eg, walking and riding in a car) and is of particular importance in higher demand activities (eg, sports-related activities). Disruption or damage in the VOR can result in symptoms such as movement-related dizziness, blurry vision, difficulty maintaining balance with head movements, and even nausea. Dizziness is one of the most common symptoms following traumatic brain injury (TBI) and is considered a risk factor for a prolonged recovery. Assessment of the vestibular system is of particular importance following TBI, in conjunction with oculomotor control, due to the intrinsic neural circuitry that exists between the ocular and vestibular systems. The purpose of this article is to review the physiology of the VOR and the visual-vestibular symptoms associated with TBI and to discuss assessment and treatment guidelines for TBI. Current challenges and future prospects will also be addressed.

Reliability and Associated Risk Factors for Performance on the Vestibular/Ocular Motor Screening (VOMS) Tool in Healthy Collegiate Athletes

BACKGROUND

The Vestibular/Ocular Motor Screening (VOMS) is a newly developed screening tool that evaluates vestibular and ocular motor symptom (eg, headache, dizziness, nausea, fogginess) provocation after a sport-related concussion. Baseline data on the VOMS are needed to extend the application of this measure to broad age groups and to document normal variations in performance.

PURPOSE

The primary purpose of this study was to examine the internal consistency of the VOMS in a large sample of healthy, nonconcussed collegiate athletes. The secondary purpose was to investigate the effects of patient sex and history of motion sickness, migraines, and concussions on baseline VOMS scores.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 263 National Collegiate Athletic Association Division I athletes (mean ± SD age, 19.85 ± 1.35 years) completed self-reported demographic and medical history at preseason physical examinations and baseline screening. Internal consistency of the VOMS was assessed with Cronbach α. A series of univariate nonparametric tests (χ(2) with odds ratios [ORs] and 95% CIs) were used to examine the associations among medical history risk factors and VOMS clinical cutoff scores (score of ≥2 for any individual VOMS symptom, near point of convergence [NPC] distance of ≥5 cm), with higher scores representing greater symptom provocation.

RESULTS

Internal consistency of the VOMS was high (Cronbach α = .97), and 89% of athletes scored below cutoff levels (ie, 11% false-positive rate). Female athletes (OR, 2.99 [95% CI, 1.34-6.70]; P = .006) and those with a personal history of motion sickness (OR, 7.73 [95% CI, 1.94-30.75]; P = .009) were more likely to have ≥1 VOMS scores above cutoff levels. No risk factors were associated with increased odds of an abnormal NPC distance.

CONCLUSION

The VOMS possesses internal consistency and an acceptable false-positive rate among healthy Division I collegiate student-athletes. Female sex and a history of motion sickness were risk factors for VOMS scores above clinical cutoff levels among healthy collegiate student-athletes. Results support a comprehensive baseline evaluation approach that includes an assessment of premorbid vestibular and oculomotor symptoms.

Behavioral and Neural Plasticity of Ocular Motor Control: Changes in Performance and fMRI Activity Following Antisaccade Training

The antisaccade task provides a model paradigm that sets the inhibition of a reflexively driven behavior against the volitional control of a goal-directed behavior. The stability and adaptability of antisaccade performance was investigated in 23 neurologically healthy individuals. Behavior and brain function were measured using functional magnetic resonance imaging (fMRI) prior to and immediately following 2 weeks of daily antisaccade training. Participants performed antisaccade trials faster with no change in directional error rate following 2 weeks of training; however this increased speed came at the cost of the spatial accuracy of the saccade (gain) which became more hypometric following training. Training on the antisaccade task resulted in increases in fMRI activity in the fronto-basal ganglia-parietal-cerebellar ocular motor network. Following training, antisaccade latency was positively associated with fMRI activity in the frontal and supplementary eye fields, anterior cingulate and intraparietal sulcus; antisaccade gain was negatively associated with fMRI activity in supplementary eye fields, anterior cingulate, intraparietal sulcus, and cerebellar vermis. In sum, the results suggest that following training, larger antisaccade latency is associated with larger activity in fronto-parietal-cerebellar ocular motor regions, and smaller antisaccade gain is associated with larger activity in fronto-parietal ocular motor regions.

A Brief Vestibular/Ocular Motor Screening (VOMS) assessment to evaluate concussions: preliminary findings

BACKGROUND

Vestibular and ocular motor impairments and symptoms have been documented in patients with sport-related concussions. However, there is no current brief clinical screen to assess and monitor these issues.

PURPOSE

To describe and provide initial data for the internal consistency and validity of a brief clinical screening tool for vestibular and ocular motor impairments and symptoms after sport-related concussions.

STUDY DESIGN

Cross-sectional study; Level of evidence, 2.

METHODS

Sixty-four patients, aged 13.9 ± 2.5 years and seen approximately 5.5 ± 4.0 days after a sport-related concussion, and 78 controls were administered the Vestibular/Ocular Motor Screening (VOMS) assessment, which included 5 domains: (1) smooth pursuit, (2) horizontal and vertical saccades, (3) near point of convergence (NPC) distance, (4) horizontal vestibular ocular reflex (VOR), and (5) visual motion sensitivity (VMS). Participants were also administered the Post-Concussion Symptom Scale (PCSS).

RESULTS

Sixty-one percent of patients reported symptom provocation after at least 1 VOMS item. All VOMS items were positively correlated to the PCSS total symptom score. The VOR (odds ratio [OR], 3.89; P < .001) and VMS (OR, 3.37; P < .01) components of the VOMS were most predictive of being in the concussed group. An NPC distance ≥5 cm and any VOMS item symptom score ≥2 resulted in an increase in the probability of correctly identifying concussed patients of 38% and 50%, respectively. Receiver operating characteristic curves supported a model including the VOR, VMS, NPC distance, and ln(age) that resulted in a high predicted probability (area under the curve = 0.89) for identifying concussed patients.

CONCLUSION

The VOMS demonstrated internal consistency as well as sensitivity in identifying patients with concussions. The current findings provide preliminary support for the utility of the VOMS as a brief vestibular/ocular motor screen after sport-related concussions. The VOMS may augment current assessment tools and may serve as a single component of a comprehensive approach to the assessment of concussions.

Vestibular function in families with inherited autosomal dominant hearing loss

The inner ear contains the developmentally related cochlea and peripheral vestibular labyrinth. Given the similar physiology between these two organs, hearing loss and vestibular dysfunction may be expected to occur simultaneously in individuals segregating mutations in inner ear genes. Twenty-two different genes have been discovered that when mutated lead to non-syndromic autosomal dominant hearing loss. A review of the literature indicates that families segregating mutations in 13 of these 22 genes have undergone formal clinical vestibular testing. Formal assessment revealed vestibular dysfunction in families with mutations in ten of these 13 genes. Remarkably, only families with mutations in the COCH and MYO7A genes self-report considerable vestibular challenges. Families segregating mutations in the other eight genes do not self-report significant balance problems and appear to compensate well in everyday life for vestibular deficits discovered during formal clinical vestibular assessment. An example of a family (referred to as the HL1 family) with progressive hearing loss and clinically-detected vestibular hypofunction that does not report vestibular symptoms is described in this review. Notably, one member of the HL1 family with clinically-detected vestibular hypofunction reached the summit of Mount Kilimanjaro.

Changes in cerebellar activation pattern during two successive sequences of saccades

The changes in the cerebellar activation pattern of two successive fMRI scanning runs were determined for visually guided to-and-fro saccades in 12 healthy volunteers familiar with the study paradigm. Group and single subject-analyses revealed a constant activation of the paramedian cerebellar vermis (uvula, tonsils, tuber, folium/declive), which reflects constant ocular motor activity in both runs. A significant decrease in activation of the cerebellar hemispheres found in the second run is best explained by either a decrease in attention or the effects of motor optimization and learning. The significant, systematic changes of the cerebellar activation pattern in two successive runs were not expected, because the ocular motor task was simple, familiar, and highly automated. These findings indicate that similar effects may bias other cerebellar activation studies, in which sensorimotor tasks are repeated in a single session.