Determining the Agreement Between Common Measures Related to Vestibulo-ocular Reflex Function After a Mild Traumatic Brain Injury in Children and Adolescents

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A battery of complementary tests is needed to assess vestibulo-ocular reflex (VOR) in pediatric mild traumatic brain injury (mTBI).

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This battery should include both symptom- and performance-based measures.

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Best practice recommendation is needed for such a battery in clinical settings.

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Cervical injury presence may influence symptoms induced during VOR testing.

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There is value of assessing for cervical injury post pediatric mTBI.

Objective

To (1) determine the level of agreement between symptom provocation and performance-based tests of vestibulo-ocular reflex (VOR) function after pediatric mild traumatic brain injury (mTBI) and (2) describe the level of symptom provocation induced by a VOR task in individuals with and without cervical findings.

Design

Cross-sectional.

Setting

This study was conducted at a tertiary care pediatric hospital.

Participants

A total of 101 participants (N=101) aged 6-18 years within 3 weeks of mTBI diagnosis were included (54.5% female; mean age, 13.92±2.63 years; mean time since injury at assessment, 18.26±6.16 days).

Interventions

None.

Main Outcome Measures

Symptom provocation (Vestibular/Ocular Motor Screening tool), performance (clinician-observed VOR performance, head thrust test [HTT], computerized dynamic visual acuity test, video head impulse test), and cervical impairment (cervical flexion-rotation test, range of motion test, self-reported neck pain). Agreement was evaluated using Cohen's κ statistic.

Results

No outcomes demonstrated agreement with symptom provocation (κ=−0.15 to 0.14). Fair agreement demonstrated between clinician-observed VOR performance and HTT (κ=0.32), with little to no agreement demonstrated between other measures. Proportions reporting test-induced dizziness and headache were greater among individuals with cervical findings (29.1%-41.8%) than without (2.3%-6.8%).

Conclusions

Findings support that symptom provocation and performance-based tests measure different constructs and thus have distinct roles when assessing VOR function. Findings suggest results from measures of symptom provocation may be influenced by coexisting cervical impairments, underlining the value of assessing for cervical injury after pediatric mTBI.

Characterizing the evolution of oculomotor and vestibulo-ocular function over time in children and adolescents after a mild traumatic brain injury

Background

Impairments to oculomotor (OM) and vestibulo-ocular reflex (VOR) function following pediatric mTBI have been demonstrated but are poorly understood. Such impairments can be associated with more negative prognosis, affecting physical and mental wellbeing, emphasizing the need to more fully understand how these evolve.

Objectives

to determine i) the extent to which performance on clinical and computerized tests of OM and VOR function varies over time in children and adolescents at 21 days, 3-, and 6-months post-mTBI; ii) the proportion of children and adolescents with mTBI presenting with abnormal scores on these tests at each timepoint.

Design

Prospective longitudinal design.

Setting

Tertiary care pediatric hospital.

Participants

36 participants with mTBI aged 6 to18.

Procedures

Participants were assessed on a battery of OM and VOR tests within 21 days, at 3- and 6-months post injury.

Outcome measures

Clinical measures: Vestibular/ocular motor screening tool (VOMS) (symptom provocation and performance); Computerized measures: reflexive saccade test (response latency), video head impulse test (VOR gain), and dynamic visual acuity test (LogMAR change).

Analysis

Generalized estimating equations (parameter estimates and odd ratios) estimated the effect of time. Proportions above and below normal cut-off values were determined.

Results

Our sample consisted of 52.8% females [mean age 13.98 (2.4) years, assessed on average 19.07 (8–33) days post-injury]. Older children performed better on visual motion sensitivity (OR 1.43, p = 0.03) and female participants worse on near point of convergence (OR 0.19, p = 0.03). Change over time (toward recovery) was demonstrated by VOMS overall symptom provocation (OR 9.90, p = 0.012), vertical smooth pursuit (OR 4.04, p = 0.03), voluntary saccade performance (OR 6.06, p = 0.005) and right VOR gain (0.068, p = 0.013). Version performance and VOR symptom provocation showed high abnormal proportions at initial assessment.

Discussion

Results indicate impairments to the VOR pathway may be present and driving symptom provocation. Vertical smooth pursuit and saccade findings underline the need to include these tasks in test batteries to comprehensively assess the integrity of OM and vestibular systems post-mTBI.

Implications

Findings demonstrate 1) added value in including symptom and performance-based measures in when OM and VOR assessments; 2) the relative stability of constructs measured beyond 3 months post mTBI.

Evaluating the Vestibulo-Ocular Reflex Following Traumatic Brain Injury: A Scoping Review

Purpose:To identify the tests and tools used to evaluate vestibulo-ocular reflex (VOR) function after traumatic brain injury (TBI) in all age groups and across TBI severity.Methods: An electronic search was conducted to include relevant peer-reviewed literature published up to November 2019. Studies included those done with humans, of all ages, and had assessments of oculomotor and/or vestibulo-ocular function in TBI.Results: Of the articles selected (N = 48), 50% were published in 2018/2019. A majority targeted mild TBI, with equal focus on non-computerized versus computerized measures of VOR. Computerized assessment tools used were videonystagmography, dynamic visual acuity/gaze stability, rotary chair, and caloric irrigation. Non-computerized tests included the head thrust, dynamic visual acuity, gaze stability, head shaking nystagmus, rotary chair tests and the vestibular/oculomotor screening tool. High variability in administration protocols were identified. Namely: testing environment, distances/positioning/equipment used, active/passive state, procedures, rotation frequencies, and variables observed.Conclusions: There is a rapid growth of literature incorporating VOR tests in mild TBI but moderate and severe TBI continues to be under-represented. Determining how to pair a clinical test with a computerized tool and developing standardized protocols when administering tests will help in developing an optimal battery assessing the VOR in TBI.

Vestibular-ocular reflex dysfunction following mild traumatic brain injury: A narrative review

Mild traumatic brain injury (mTBI) is a prevalent injury which occurs across many populations, including children and adolescents, athletes, military personnel, and the elderly. mTBI can result in various subjective symptoms and clinical deficits, such as abnormalities to the vestibulo-ocular reflex (VOR). Over 50% of individuals with mTBI are reported to have VOR abnormalities, which strongly contribute to feelings of dizziness and unsteadiness. Dizziness is a strong predictor for prolonged recovery following mTBI and is additionally linked with mental health difficulties and functional limitations affecting likelihood of return to work. Early diagnosis, and subsequent treatment, of VOR deficits following mTBI may greatly improve recovery outcomes and a patient's quality of life, but a thorough comprehension of the related pathophysiology is necessary to understand the assessments used to diagnose VOR abnormalities. Therefore, the purpose of this article is i) provide readers with an introduction on the VOR physiology to facilitate understanding about mTBI-related abnormalities, and ii) to discuss current assessments that are commonly used to measure VOR function following mTBI. As the VOR and oculomotor (OM) systems are heavily linked and often work in tandem, discussion of the relevant aspects of the OM system is also provided.

Parasite vaccines: The new generation

Parasites cause some of the most devastating and prevalent diseases in humans and animals. Moreover, parasitic infections increase mortality rates of other serious non-parasitic infections caused by pathogens such as HIV-1. The impact of parasitic diseases in both industrialised and developing countries is further exacerbated by the resistance of some parasites to anti-parasitic drugs and the absence of efficacious parasite vaccines. Despite years of research, much remains to be done to develop effective vaccines against parasites. This review focuses on the more recent vaccine strategies such as DNA and viral vector-based vaccines that are currently being used to develop vaccines against parasites. Obstacles yet to be overcome and possible advantages and disadvantages of these vaccine modalities are also discussed.

Trapping efficacy of Duddingtonia flagrans against Haemonchus contortus at temperatures existing at lambing in Australia

The aim of this study was to determine the trapping efficacy of Duddingtonia flagrans against Haemonchus contortus at the temperature ranges experienced around lambing in the major sheep producing regions of Australia. Faeces were collected from Merino wethers, maintained in an animal house and which had received either D. flagrans chlamydospores for a 6-day period (DF) or not (NIL). Faeces were incubated at one of four daily temperature regimens which were composed of hourly steps to provide 6-19 degrees C, 9-25 degrees C, 14-34 degrees C and 14-39 degrees C to mimic normal diurnal air temperature variation. Enumeration of the number of preinfective and infective larvae that had migrated from or remained in faecal pellets was used to calculate percentage recovery and trapping efficacy of D. flagrans. Recovery of H. contortus larvae of both stages was significantly lower in DF faeces but the magnitude of the effect was considerably greater for infective larvae. Mean recovery of infective larvae from NIL and DF faeces was 10.6 and 0.4%, respectively, indicating a mean trapping efficacy of 96.4%. The lowest trapping efficacy (80.7%) was observed at 6-19 degrees C but total recovery of infective larvae, from DF faeces, was greatest at the two highest temperature regimens, although still less than 0.9%. The results of this study indicate that typical Australian lambing temperatures should not be a barrier to the use of D. flagrans as an effective biocontrol of H. contortus in Australia.

The role of As60A, a TGF-beta homolog, in Anopheles stephensi innate immunity and defense against Plasmodium infection

We have examined the constitutive and induced expression of As60A in Anopheles stephensi females. As60A is expressed throughout the body of A. stephensi, including the midgut, fat body and developing eggs. We discovered that As60A is induced in the midgut and carcass of A. stephensi in response to Plasmodium infection. Induction of As60A correlates with periods of parasite motility and reproduction. Further, induction is dependent on the intensity of parasite infection: low numbers of parasites do not induce As60A expression. Thus, we conclude that As60A is a component of the A. stephensi immune response to Plasmodium infection. The involvement of a member of the transforming growth factor beta (TGF-beta) super family in the mosquito immune response is analogous to the involvement of TGF-beta1 in the mammalian immune response to Plasmodium. The modulation of As60A and A. stephensi nitric oxide synthase (AsNOS) expression in response to Plasmodium indicates that homologs of effector (NOS) and regulator (TGF-beta1) gene super families may defend evolutionarily diverse hosts against a shared pathogen.

Phylogeny of ticks (Ixodida) inferred from nuclear ribosomal DNA

Phylogenetic relationships of 9 species of ticks were inferred from nucleotide sequences of the D1 domain of large subunit ribosomal DNA (rDNA), the V4 region of small subunit rDNA and sequences immediately adjacent to these regions. Six of the 7 subfamilies in the Argasidae and Ixodidae were represented: Ornithodorinae and Argasinae from the Argasidae (soft ticks); and Ixodinae, Amblyomminae, Haemaphysalinae and Rhipicephalinae from the Ixodidae (hard ticks). A mite, Phytoseiulus persimilis, from the Mesostigmata, the putative sister group of the Ixodida, was used for out-group reference. Our sequence alignment, which contained the D1, V4 and adjacent sequences, comprised 503 sites; 209 of these varied among the species studied and 77 were phylogenetically informative, i.e. at least 2 different nucleotides were represented at least twice. This alignment was subjected to maximum parsimony, genetic distance and maximum likelihood analyses. We found strong support in bootstrap resampling experiments for the following relationships: (i) monophyly of the 7 species of Ixodidae (98-100% support); (ii) monophyly of the 2 species of Amblyomma (93-99%); (iii) monophyly of the 6 species of Metastriata (96-99%); (iv) a sister-group relationship between Ixodes pilosus and the 6 species of Metastriata (98-100%); and (v) a sister-group relationship between Ornithodoros capensis (Ornithodorinae) and the 7 species of Ixodidae (94-99% support). The last result may be preliminary evidence that the Argasidae family (soft ticks) is paraphyletic since the 2 argasid species did not form a monophyletic group. The paraphyletic status of the Argasidae has been previously suggested by Black & Piesman (1994; Proceedings of the National Academy of Sciences U.S.A. 91: 10034). Our study indicates that the D1, V4 and adjacent sequences may be used to answer long-standing questions about the phylogeny of the Ixodida.