Head Injury and Blast Exposure: Vestibular Consequences

Relationships Among Baseline Concussion Balance Test and Gaze Stability Test Scores in Division-I Collegiate Athletes

CONTEXT

Sports-related concussions are commonly occurring injuries as a result of sports and recreation that may cause alterations in brain functioning. It is important to be able to evaluate the impact of these injuries on function to manage the injury recovery and ensure recovery. Recent literature suggests the use of objective evaluation strategies in a multifaceted approach to evaluate and manage these injuries. It is important to understand the relationships between the assessments and how best to utilize each assessment. The purpose of this study was to investigate if relationships exist between measures of vestibular function at baseline in assessments that may be used following sports-related concussions. Additionally, a secondary purpose was to determine if self-reported symptoms were related to performance on the assessments. This study aimed to identify if these assessments measured independent functions of the vestibulo-ocular reflex or if some redundancy existed among the assessment strategies.

DESIGN

A cross-sectional study design was used in a cohort of collegiate athletes ages 18-24.

METHODS

Participants completed demographics questionnaires, the Post-Concussion Symptom Scale, Gaze Stabilization Test, and Concussion Balance Test. Spearman rho correlations were used to examine the relationships between the measures.

RESULTS

One hundred and thirty-five collegiate athletes (82 males and 53 females) were included, representative of 3 sports (cheerleading, soccer, and football) with a mean age of 19.77 (1.42) years old. There were weak to moderate, significant relationships between measures of Gaze Stabilization Test and Concussion Balance Test errors (r = .20-.31, P = .001-.03).

CONCLUSIONS

The direction of these relationships indicated that greater Concussion Balance Test errors were associated with greater Gaze Stabilization Test performance. These relationships may be attributed to the difficulty created by the foam conditions and the integration of more complex sensory tasks required to maintain balance during the more difficult conditions.

Dizziness Directly Influences Postconcussion Symptoms and Is Predictive of Poorer Mental Health in UK Military Personnel: A Retrospective Analysis

OBJECTIVE

To investigate the contribution of dizziness to postconcussion symptoms, depression, and anxiety symptoms.

SETTING

Mild traumatic brain injury (mTBI) service, Defence Medical Rehabilitation Centre, Stanford Hall.

PARTICIPANTS

Two hundred eighty-three UK military personnel from the Royal Navy, Royal Airforce, Royal Marines, and British Army.

DESIGN

A retrospective analysis of data from the Ministry of Defence medical records database.

MAIN MEASURES

Sixteen-item Rivermead Post Concussion Symptoms Questionnaire, Generalized Anxiety Disorder 7-item scale, Patient Health Questionnaire-9, The Dizziness Handicap Inventory.

RESULTS

Injuries from sports or falls were the most common mechanism of mTBI, accounting for 23%, respectively. Chi-square analysis indicated that individuals with dizziness and postconcussion symptoms (PCS) had greater severity of PCS, depression, and anxiety than those with PCS alone. Mediation analysis showed dizziness directly and independently influenced the severity of PCS, despite the indirect effects of mediating depression and anxiety symptoms.

CONCLUSION

Comorbid dizziness and PCS were predictive of poorer mental health compared with PCS alone. In addition, dizziness directly influenced the severity of PCS irrespective of the indirect effects of mental health symptoms. These observations suggest that treating dizziness with vestibular rehabilitation may improve PCS and mental health.

Comparison of Vestibular/Ocular Motor Screening (VOMS) and Computerized Eye-tracking to Identify Exposure to Repetitive Head Impacts

INTRODUCTION

Military service members (SMs) are exposed to repetitive head impacts (RHIs) in combat and training that are purported to adversely affect brain health, including cognition, behavior, and function. Researchers have reported that RHI from blast-related exposure may affect both vestibular and ocular function, which in turn may be related to symptomology. As such, an examination of the effects of RHI on exposed military SMs should incorporate these domains. To date, researchers have not compared groups of exposed special operations forces (SOF) operators on combined clinical vestibular/ocular and eye-tracker-based outcomes. Therefore, the primary purpose of this study was to compare participant-reported symptoms and performance on the Vestibular/Ocular Motor Screening (VOMS) tool with performance on the computerized RightEye tracking system between SOF operators exposed to blast-related RHI and healthy controls without blast-related exposure. In addition, the study aimed to compare subgroups of snipers and breachers exposed to RHI to controls on the preceding metrics, as well as identify a subset of individual (demographic) factors, participant-reported symptoms, and performance metrics on VOMS and RightEye that best identify SOF operators exposed to RHI from unexposed controls.

MATERIALS AND METHODS

The study involved a cross-sectional design including 25 Canadian SOF SMs comprised of breachers (n = 9), snipers (n = 9), and healthy, unexposed controls (n = 7). The former 2 groups were combined into an RHI group (n = 18) and compared to controls (n = 7). Participants provided demographics and completed a self-reported concussion-related symptom report via the Military Acute Concussion Evaluation 2, the VOMS, and RightEye computerized eye-tracking assessments. Independent samples t-tests and ANOVAs were used to compare the groups on the outcomes, with receiver operating characteristic curve and area under the curve (AUC) analyses to identify predictors of blast exposure. This study was approved by the Defence Research Development Canada Human Research Ethics Committee and the Canadian Forces Surgeon General/Special Forces Command.

RESULTS

The results from t-tests supported group differences for age (P = .012), participant-reported symptoms (P = .006), and all VOMS items (P range = <.001-.02), with the RHI group being higher than healthy controls on all variables. ANOVA results supported group differences among snipers, breachers, and controls for age (P = .01), RightEye saccades (P = .04), participant-reported total symptom severity (P = .03), and VOMS total scores (P = .003). The results of the receiver operating characteristic curve analyses supported age (AUC = 0.81), Military Acute Concussion Evaluation 2 participant-reported total symptom severity (AUC = 0.87), and VOMS total scores (AUC = 0.92) as significant predictors of prior blast exposure.

CONCLUSIONS

Participant-reported concussion symptoms, VOMS scores, and age were useful in identifying SOF operators exposed to RHI from controls. RightEye metrics were not useful in differentiating RHI groups from controls. Differences between snipers and breachers warrant further research. Overall, the findings suggest that VOMS may be a useful tool for screening for the effects of exposure to RHI in SOF operators. Future investigations should be conducted on a larger sample of military SMs, consider additional factors (e.g., RHI exposure levels, medical history, and sex), and include additional assessment domains (e.g., balance, cognitive, and psychological).

The impact of different neurobehavioral symptoms on suicidal ideation and perceived likelihood of future suicidality

Existing literature suggests that psychological and functional impairment, independent of head injury severity, can increase suicide risk. This study explores the impacts of self-perceived dysfunction within four neurobehavioral symptom clusters-vestibular (e.g., dizziness, balance), somatosensory (e.g., headaches, nausea, vision), affective (e.g., anxious, irritable mood), and cognitive (e.g., concentration, memory, indecision)-on current suicidal ideation and the perceived likelihood of future suicidal ideation and attempts. Community participants (n = 309; Mage = 36.88; 51.6% female; 79.6% White) completed the Neurobehavioral Symptom Inventory (NSI) and the Self-Injurious Thoughts and Behaviors-Short Form (SITBI-SF). Quantile regression analysis was used to explore the effects of the four neurobehavioral symptom clusters at different levels of suicidal ideation intensity, perceived likelihood of future suicidal ideation, and self-perceived likelihood of future suicide attempt. Controlling for past head injuries and suicide attempts, affective symptoms were significantly associated with a moderate and high average intensity of current suicidal ideation. Somatosensory symptoms were significantly associated with a moderate perceived likelihood of future suicidal ideation. Finally, vestibular symptoms were significantly associated with a moderate perceived likelihood of a future suicide attempt. These findings highlight the critical need to consider a broader spectrum of symptoms, including chronic physical symptoms, when assessing suicide risk. Furthermore, they underscore the need to expand beyond affective symptoms as an explanation for increased suicidality and examine additional mechanisms through which chronic physical symptoms can increase suicide risk.

Association of Head Injury, Neck Injury or Acoustic Trauma on Phenotype of Ménière's Disease

The aim of the present study was to investigate adverse effects of head injury, neck trauma, and chronic noise exposure on the complaint profile in people with Ménière's disease (MD). The study used a retrospective design. Register data of 912 patients with MD from the Finnish Ménière Federation database were studied. The data comprised case histories of traumatic brain injury (TBI), neck trauma and occupational noise exposure, MD specific complaints, impact related questions, and the E-Qol health-related quality of life instrument. TBI was classified based on mild, moderate, and severe categories of transient loss of consciousness (TLoC). The mean age of the participants was 60.2 years, the mean duration of the disease was 12.6 years, and 78.7% were females. Logistic regression analysis, linear correlation, and pairwise comparisons were used in evaluating the associations. 19.2% of the participants with MD had a history of TBI. The phenotype of participants with TBI was associated with frequent vestibular drop attacks (VDA), presyncope, headache-associated vertigo, and a reduction in the E-QoL. Logistic regression analysis explained the variability of mild TBI in 6.8%. A history of neck trauma was present in 10.8% of the participants. Neck trauma associated with vertigo (NTwV) was seen in 47 and not associated with vertigo in 52 participants. The phenotype of NTwV was associated with balance problems, VDA, physical strain-induced vertigo, and hyperacusia. Logistic regression analysis explained 8.7% of the variability of the complaint profile. Occupational noise exposure was recorded in 25.4% of the participants and correlated with the greater impact of tinnitus, hyperacusis, and hearing loss. Neither the frequency, duration, or severity of vertigo or nausea were significantly different between the baseline group and the TBI, NTwV, or noise-exposure groups. The results indicate that TBI and NTwV are common among MD patients and may cause a confounder effect.

Blast Overpressures as a Military and Occupational Health Concern

PURPOSE

This tutorial reviews effects of environmental stressors like blast overpressures and other well-known acoustic contaminants (continuous, intermittent, and impulsive noise) on hearing, tinnitus, vestibular, and balance-related functions. Based on the overall outcome of these effects, detailed consideration is given to the health and well-being of individuals.

METHOD

Because hearing loss and tinnitus are consequential in affecting quality of life, novel neuromodulation paradigms are reviewed for their positive abatement and treatment-related effects. Examples of clinical data, research strategies, and methodological approaches focus on repetitive transcranial magnetic stimulation (rTMS) and electrical stimulation of the vagus nerve paired with tones (VNSt) for their unique contributions to this area.

RESULTS

Acoustic toxicants transmitted through the atmosphere are noteworthy for their propensity to induce hearing loss and tinnitus. Mounting evidence also indicates that high-level rapid onset changes in atmospheric sound pressure can significantly impact vestibular and balance function. Indeed, the risk of falling secondary to loss of, or damage to, sensory receptor cells in otolith organs (utricle and saccule) is a primary reason for this concern. As part of the complexities involved in VNSt treatment strategies, vocal dysfunction may also manifest. In addition, evaluation of temporospatial gait parameters is worthy of consideration based on their ability to detect and monitor incipient neurological disease, cognitive decline, and mortality.

CONCLUSION

Highlighting these respective areas underscores the need to enhance information exchange among scientists, clinicians, and caregivers on the benefits and complications of these outcomes.

Symptoms and Central Sensory Integration in People With Chronic mTBI: Clinical Implications

INTRODUCTION

Balance deficits in people with chronic mild traumatic brain injury (mTBI; ≥3 months post-mTBI), thought to relate to central sensory integration deficits, are subtle and often difficult to detect. The purpose of this study was to determine the sensitivity of the instrumented modified clinical test of sensory integration for balance (mCTSIB) in identifying such balance deficits in people with symptomatic, chronic mTBI and to establish the associations between balance and mTBI symptom scores in the chronic mTBI group.

METHODS

The Institutional Review Board approved these study methods. Forty-one people with chronic mTBI and balance complaints and 53 healthy controls performed the mCTSIB (eyes open/closed on firm/foam surfaces; EoFi, EcFi, EoFo, and EcFo) with a wearable sensor on their waist to quantify sway area (m2/s4). Sensory reweighting variables were calculated for the firm and foam stance conditions. A stopwatch provided the clinical outcome for the mCTSIB (time). Each participant completed the Neurobehavioral Symptom Inventory (NSI), which quantifies mTBI-related symptoms and provides a total score, as well as sub-scores on affective, cognitive, somatic, and vestibular domains.

RESULTS

The mTBI group reported significantly higher symptom scores across each NSI sub-score (all Ps < .001). The mTBI group had a significantly larger sway area than the control group across all mCTSIB conditions and the mTBI group had significantly higher sensory reweighting scores compared to the control group on both the firm (P = .01) and foam (P = .04) surfaces. Within the mTBI group, the NSI vestibular score significantly related to the mCTSIB sway area EcFi (r = 0.38; P = .02), sway area EcFo (r = 0.43; P = .006), sensory reweighting firm (r = 0.33; P = .04), and sensory reweighting foam (r = 0.38; P = .02). The average sway area across the 4 mCTSIB conditions was significantly (area under the curve: 0.77; P < .001) better at differentiating groups than the mCTSIB clinical total score. The average sway area across the 4 mCTSIB conditions had a sensitivity of 73% and a specificity of 71%. The clinical mCTSIB outcome scores were not different between groups.

CONCLUSION

People with chronic mTBI appear to have central sensory integration deficits detectable by instrumented measures of postural assessment. These findings suggest that central sensory integration should be targeted in rehabilitation for people with chronic mTBI.

A mathematical model for mechanical activation and compound action potential generation by the utricle in response to sound and vibration

Introduction

Calyx bearing vestibular afferent neurons innervating type I hair cells in the striolar region of the utricle are exquisitely sensitive to auditory-frequency air conducted sound (ACS) and bone conducted vibration (BCV). Here, we present experimental data and a mathematical model of utricular mechanics and vestibular compound action potential generation (vCAP) in response to clinically relevant levels of ACS and BCV. Vibration of the otoconial layer relative to the sensory epithelium was simulated using a Newtonian two-degree-of-freedom spring-mass-damper system, action potential timing was simulated using an empirical model, and vCAPs were simulated by convolving responses of the population of sensitive neurons with an empirical extracellular voltage kernel. The model was validated by comparison to macular vibration and vCAPs recorded in the guinea pig, in vivo.

Results

Transient stimuli evoked short-latency vCAPs that scaled in magnitude and timing with hair bundle mechanical shear rate for both ACS and BCV. For pulse BCV stimuli with durations &lt;0.8 ms, the vCAP magnitude increased in proportion to temporal bone acceleration, but for pulse durations &gt;0.9 ms the magnitude increased in proportion to temporal bone jerk. Once validated using ACS and BCV data, the model was applied to predict blast-induced hair bundle shear, with results predicting acute mechanical damage to bundles immediately upon exposure.

Discussion

Results demonstrate the switch from linear acceleration to linear jerk as the adequate stimulus arises entirely from mechanical factors controlling the dynamics of sensory hair bundle deflection. The model describes the switch in terms of the mechanical natural frequencies of vibration, which vary between species based on morphology and mechanical factors.

The Portable Warrior Test of Tactical Agility: A Novel Functional Assessment That Discriminates Service Members Diagnosed With Concussion From Controls

INTRODUCTION

Return-to-duty (RTD) readiness assessment for service members (SM) following concussion requires complex clinical considerations. The Portable Warrior Test of Tactical Agility (POWAR-TOTAL) is a functional assessment which improves on previous laboratory-based RTD assessments.

METHODS

Sixty-four SM diagnosed with concussion and 60 healthy control (HC) SM participated in this study. Group differences were analyzed to validate the POWAR-TOTAL. The High-level Mobility Assessment Test (HiMAT) was used to examine concurrent construct validity. An exploratory logistic regression analysis examined predictive validity.

RESULTS

The groups were demographically well-matched except for educational level. POWAR-TOTAL measures were statistically significantly different between the groups with moderate to large effect sizes. Concussed participants were less likely to be able to complete all trials of the POWAR-TOTAL. Motor scores correlated highly with HiMAT scores. POWAR-TOTAL motor task performance and membership in the control group was significantly associated with self-reported physical readiness to deploy.

CONCLUSION

The POWAR-TOTAL is a clinically feasible, military relevant assessment that is sensitive to differences between concussed and HC SM. This analysis supports the discriminant and construct validity of the POWAR-TOTAL, and may be useful for medical providers evaluating RTD readiness for SM who have sustained a concussion.

Patterns of vestibular dysfunction in chronic traumatic brain injury

Background

Dizziness and imbalance are common following traumatic brain injury (TBI). While these symptoms are often attributed to vestibular dysfunction, the relative contribution of peripheral vs. central mechanisms is unclear. This study investigated the prevalence of semicircular canal and otolith abnormalities in a cohort of patients with chronic TBI and symptoms of dizziness or imbalance. The relationship between vestibular, oculomotor and posturography results was further explored.

Methods

Clinical records of patients attending the New Zealand Dizziness and Balance Centre from January 2015 to December 2019 were reviewed for consideration in the study. Inclusion required: an age of 18–80 years, a diagnosed TBI, and vestibular assessment using three-dimensional video head impulses (vHIT), cervical and ocular vestibular-evoked myogenic potentials (c and o VEMPs, respectively) and caloric testing. Severe TBI, pre-existing vestibular diagnoses, and incomplete test results were excluded. Rates of abnormalities were determined for each test and compared with results of oculomotor function testing and postural control, measured using the sensory organization test (SOT).

Results

Of 158 reviewed records, 99 patients aged 49 ± 15 years (59 female) fulfilled criteria for inclusion in the study. The median time between the head injury and the clinical assessment was 12 (IQR 6–21) months. Abnormalities involving one or more components of the vestibular labyrinth and/or nerve divisions were identified in 33 of 99 patients (33.3%). The horizontal semicircular canal was most frequently affected (18.2%), followed by the saccule (14.1%), utricle (8.1%), posterior (7.1%) and anterior (2.0%) semicircular canals. Vestibular test abnormalities were associated with skull-base fractures, superior canal dehiscence, and focal ear trauma. Oculomotor dysfunction and postural instability were recorded in 41.1 and 75.5% of patients, respectively. Postural instability correlated with abnormal oculomotor function (p = 0.008) but not peripheral vestibular hypofunction (p = 0.336).

Conclusions

Dizziness and/or imbalance in chronic TBI was associated with impaired postural stability for tasks requiring high levels of use of vestibular and visual input for balance. Vestibular hypofunction identified through vHIT, VEMP and caloric testing was recorded but was less common, except when the injury involved a fractured skull-base. There was no specific pattern of end-organ or nerve involvement which characterized this group of patients.

The psychosocial burden of visible disfigurement following traumatic injury

Hundreds of thousands of individuals experience traumatic injuries each year. Some are mild to moderate in nature and patients experience full functional recovery and little change to their physical appearance. Others result in enduring, if not permanent, changes in physical functioning and appearance. Reconstructive plastic surgical procedures are viable treatments options for many patients who have experienced the spectrum of traumatic injuries. The goal of these procedures is to restore physical functioning and reduce the psychosocial burden of living with an appearance that may be viewed negatively by the patient or by others. Even after receipt of reconstructive procedures, many patients are left with residual disfigurement. In some, disability and disfigurement may be so profound that individuals are candidates for vascularized composite allotransplantation (VCA) procedures, i.e., the transplantation of a vascularized human body part containing multiple tissue types (skin, muscle, bone, nerves, and blood vessels) as an anatomical and/or structural unit. This narrative review paper summarizes the literature on the psychosocial burden experienced by those who have visible disfigurement. While many of these individuals experience stigma and discrimination, relatively few studies have employed a stigma framework to understand the psychosocial sequelea. This paper briefly addresses this framework. Last, particular focus is given to the psychosocial issues of individuals with particularly severe injuries who are potential candidates for VCA procedures.

Binocular Alignment Changes Between Sitting and Supine Positions in Patients with Dizziness

Vertical and torsional ocular misalignment can occur from mild traumatic brain injury or inner ear pathology, which may vary depending on head position. Here, we evaluate differences in a behavioral measure of binocular alignment in both upright and supine head position. Ocular perception of vertical and torsional alignment was measured using the torsional and vertical alignment nulling (TAN, VAN) task in N = 52 veterans with dizziness (N = 38 with traumatic brain injury), N = 41 civilians with vestibular schwannoma resection (UVD), and N = 33 healthy controls for both positions. The interquartile range within each group, regardless of head position, was greater for torsional compared to vertical misalignment. We use generalized estimating equations to compare average TAN (torsional) scores and VAN (vertical) scores between groups and test position. Compared to the healthy controls, TAN was significantly increased by + 0.4186° in veterans (P = 0.030) and by + 0.5747° in UVD (P = 0.010), but there was no difference with head position. For VAN, no difference was found between the three groups, but the misalignment did worsen by 0.0888° (P = 0.0070) as the head position moved from upright to supine. Head position had negligible effects on this behavioral measure of vertical and torsional binocular misalignment, and torsional misalignments were worse than controls in both veterans with dizziness and patients with vestibular nerve resection although neither reported torsional diplopia. Our data suggests that the tolerance for roll misalignment may be abnormally large in patients with dizziness. Alternatively, perceptual roll misalignments may be a manifest cause for dizziness, and therefore a useful proxy for distinguishing differences in putative otolith function in veterans with dizziness.

Post-concussive Dizziness: A Review and Clinical Approach to the Patient

Dizziness is a frequent complaint after head trauma. Among patients who suffer a concussion (mild traumatic brain injury or mTBI), dizziness is second only to headache in symptom frequency. The differential diagnosis of post-concussive dizziness (PCD) can be divided into non-vestibular, central vestibular and peripheral vestibular causes with growing recognition that patients frequently exhibit both central and peripheral findings on vestibular testing. Symptoms that traditionally have been ascribed to central vestibular dysfunction may be due to peripheral dysfunction. Further, our ability to test peripheral vestibular function has improved and has allowed us to identify peripheral disorders that in the past would have remained unnoticed. The importance of the identification of the peripheral component in PCD lies in our ability to remedy the peripheral vestibular component to a much greater extent than the central component. Unfortunately, many patients are not adequately evaluated for vestibular disorders until long after the onset of their symptoms. Among the diagnoses seen as causes for PCD are (1) Central vestibular disorders, (2) Benign Paroxysmal Positional Vertigo (BPPV), (3) Labyrinthine dehiscence/perilymph fistula syndrome, (4) labyrinthine concussion, (5) secondary endolymphatic hydrops, (6) Temporal bone fracture, and (7) Malingering (particularly when litigation is pending). These diagnoses are not mutually exclusive and PCD patients frequently exhibit a combination of these disorders. A review of the literature and a general approach to the patient with post-concussive dizziness will be detailed as well as a review of the above-mentioned diagnostic categories.

Traumatic brain injury induced by exposure to blast overpressure via ear canal

Exposure to explosive shockwave often leads to blast-induced traumatic brain injury in military and civilian populations. Unprotected ears are most often damaged following exposure to blasts. Although there is an association between tympanic membrane perforation and TBI in blast exposure victims, little is known about how and to what extent blast energy is transmitted to the central nervous system via the external ear canal. The present study investigated whether exposure to blasts directed through the ear canal causes brain injury in Long-Evans rats. Animals were exposed to a single blast (0-30 pounds per square inch (psi)) through the ear canal, and brain injury was evaluated by histological and behavioral outcomes at multiple time-points. Blast exposure not only caused tympanic membrane perforation but also produced substantial neuropathological changes in the brain, including increased expression of c-Fos, induction of a profound chronic neuroinflammatory response, and apoptosis of neurons. The blast-induced injury was not limited only to the brainstem most proximal to the source of the blast, but also affected the forebrain including the hippocampus, amygdala and the habenula, which are all involved in cognitive functions. Indeed, the animals exhibited long-term neurological deficits, including signs of anxiety in open field tests 2 months following blast exposure, and impaired learning and memory in an 8-arm maze 12 months following blast exposure. These results suggest that the unprotected ear canal provides a locus for blast waves to cause TBI. This study was approved by the Institutional Animal Care and Use Committee at the University of Mississippi Medical Center (Animal protocol# 0932E, approval date: September 30, 2016 and 0932F, approval date: September 27, 2019).

Altered Vestibular Balance Function in Combat Sport Athletes

Combat sports pose a risk for accumulative injuries to the nervous system, yet fighters have remained an understudied population. Here, our purpose was to determine whether repetitive blows to the head have an effect on vestibular balance reflexes in combat sports athletes. We compared lower-limb muscle responses evoked with electrical vestibular stimuluation (EVS) between fighters (boxing/muay thai) and non-fighter controls. Each participant received stochastic vestibular stimulation (0-25 Hz, ±3 mA) over their mastoid processes while they stood relaxed with their head to the left or right. Surface electromyography was recorded from the medial gastrocnemius and soleus muscles bilaterally. Short and medium latency response (SLR/MLR) peaks were significantly delayed in the fighter group compared to controls. SLR and MLR peak amplitudes were also significantly lower in fighters. Fighter-estimated cumulative repetitive head impact (RHI) events demonstrated strong positive correlations with the timing of SLR and MLR peaks. Cumulative RHI events also negatively correlated with peak MLR amplitude and response gain at frequencies above 5 Hz. Our results provide evidence of a progressive vestibular impairment in combat sports athletes, potentially resulting from blows to the head accumulated in sparring practice and competitive bouts throughout their careers. Taken together, EVS-based vestibular assessments may provide a valuable clinical diagnostic tool and help better inform "return-to-play" and career-length decisions for not only combat sports athletes, but potentially other populations at risk of RHIs.

Exploring persistent complaints of imbalance after mTBI: Oculomotor, peripheral vestibular and central sensory integration function

BACKGROUND

Little is known on the peripheral and central sensory contributions to persistent dizziness and imbalance following mild traumatic brain injury (mTBI).

OBJECTIVE

To identify peripheral vestibular, central integrative, and oculomotor causes for chronic symptoms following mTBI.

METHODS

Individuals with chronic mTBI symptoms and healthy controls (HC) completed a battery of oculomotor, peripheral vestibular and instrumented posturography evaluations and rated subjective symptoms on validated questionnaires. We defined abnormal oculomotor, peripheral vestibular, and central sensory integration for balance measures among mTBI participants as falling outside a 10-percentile cutoff determined from HC data. A X-squared test associated the proportion of normal and abnormal responses in each group. Partial Spearman's rank correlations evaluated the relationships between chronic symptoms and measures of oculomotor, peripheral vestibular, and central function for balance control.

RESULTS

The mTBI group (n = 58) had more abnormal measures of central sensory integration for balance than the HC (n = 61) group (mTBI: 41% -61%; HC: 10%, p's <  0.001), but no differences on oculomotor and peripheral vestibular function (p >  0.113). Symptom severities were negatively correlated with central sensory integration for balance scores (p's <  0.048).

CONCLUSIONS

Ongoing balance complaints in people with chronic mTBI are explained more by central sensory integration dysfunction rather than peripheral vestibular or oculomotor dysfunction.

Normative values for the Sensory Organization Test in an active duty military cohort

BACKGROUND

Computerized dynamic posturography is commonly used to assess balance in service members, but normative values for the military population have not been established.

RESEARCH QUESTION

What are the normative values for the Motor Control Test (MCT), Sensory Organization Test (SOT) and the enhanced SOT (eSOT) within the military population and at which point do they differ?

METHODS

Cross-sectional study. 237 active duty service members (78 % male) completed the MCT, SOT and the eSOT with the sway manipulated at a gain of 1.2, 1.4, 1.6, 1.8, or 2.0. A Mann-Whitney U test was used to compare the means of men and women for the SOT and MCT composite scores. A Kruskal-Wallis H test was used to compare the means of age groups for the SOT composite score. An independent t-test was used to compare the SOT composite scores from our military population to the manufacturer's normative (civilian) data. The means and standard deviations for the eSOT scores were reported for each gain. Paired-samples t-tests were performed to compare the SOT composite score with the eSOT composite score for each level of gain.

RESULTS

There was no difference between SOT composite scores for men and women (Mann-Whitney U = 4363.50, p = 0.19) or among age groups (Kruskal-Wallis = 2.77, p = 0.25). The mean SOT composite scores were not different from the manufacturer's normative values (p = 0.155). SOT composite scores were significantly higher than eSOT composite scores for gains of 1.4 (t = 3.16, p = 0.003), 1.6 (t = 5.73, p < 0.001), 1.8 (t = 5.26, p < 0.001) and 2.0 (t = 5.89, p < 0.001). MCT composite scores were lower in the 18-26 year old than the 36-45 year old age group (p = 0.013).

SIGNIFICANCE

This study establishes normative values for the MCT, SOT and eSOT in active duty military service members. The results suggest that the manufacturer's normal values are appropriate for making judgments about the postural stability of service members.

Characteristics and Impact of U.S. Military Blast-Related Mild Traumatic Brain Injury: A Systematic Review

As a result of armed conflict, head trauma from exposure to blasts is an increasing critical health issue, particularly among military service members. Whilst numerous studies examined the burden of blast-related brain injuries on service members', few systematic reviews have been published. This work provides a comprehensive summary of the evidence on blast-related mild traumatic brain injury (mTBI) burden in active U.S. military service members and inactive Veterans, describing characteristics and outcomes. Records published up to April 2017 were identified through a search of PubMed, Web of Science, Scopus, Ovid MEDLINE, and Cochrane Library. Records-based and original research reporting on U.S. military service members and Veterans with mild blast TBI were included. Data on subject characteristics, exposure, diagnostic criterion, and outcomes were extracted from included studies using a standardized extraction form and were presented narratively. Of the 2,290 references identified by the search, 106 studies with a total of 37,515 participants met inclusion criteria for blast-related mTBI. All but nine studies were based out of military or Veteran medical facilities. Unsurprisingly, men were over-represented (75–100%). The criteria used to define blast-related mTBI were consistent; however, the methodology used to ascertain whether individuals met those criteria for diagnosis were inconsistent. The diagnosis, most prevalent among the Army, heavily relied on self-reported histories. Commonly reported adverse outcomes included hearing disturbances and headaches. The most frequently associated comorbidities were post-traumatic stress disorder, depression, anxiety, sleep disorders, attention disorders, and cognitive disorders. The primary objective of this review was to provide a summary of descriptive data on blast-related mTBI in a U.S. military population. Low standardization of the methods for reaching diagnosis and problems in the study reporting emphasize the importance to collect high-quality data to fill knowledge gaps pertaining to blast-related mTBI.

Behavioral Deficits in Animal Models of Blast Traumatic Brain Injury

Blast exposure has been identified to be the most common cause for traumatic brain injury (TBI) in soldiers. Over the years, rodent models to mimic blast exposures and the behavioral outcomes observed in veterans have been developed extensively. However, blast tube design and varying experimental parameters lead to inconsistencies in the behavioral outcomes reported across research laboratories. This review aims to curate the behavioral outcomes reported in rodent models of blast TBI using shockwave tubes or open field detonations between the years 2008–2019 and highlight the important experimental parameters that affect behavioral outcome. Further, we discuss the role of various design parameters of the blast tube that can affect the nature of blast exposure experienced by the rodents. Finally, we assess the most common behavioral tests done to measure cognitive, motor, anxiety, auditory, and fear conditioning deficits in blast TBI (bTBI) and discuss the advantages and disadvantages of these tests.

Vestibular Assessment in Patients with Persistent Symptoms of Mild Traumatic Brain Injury

Aim

The estimated worldwide incidence of TBI is 10 million cases per year. Dizziness and imbalance are two common symptoms in mild TBI (mTBI). In about 10-15% of TBI patients, these symptoms remain for a long time and may show no recovery. These persistent symptoms may relate to different factors including vestibular abnormalities. The aim of this study is a vestibular assessment of patients with persistent symptoms of mTBI by different tests including computerized dynamic posturography.

Materials and Methods

21 patients with mTBI evaluated in this study. Patients were civilians with persistent symptoms. TBI did cause by blunt force trauma (mainly from falling) in the past 6 months. They had normal neurologic and musculoskeletal assessments and no temporal bone fracture. Several auditory and vestibular evaluations were performed for each patient. They included: case history, otoscopy, pure tone and speech audiometry, tympanometry, vestibular bedside examination (spontaneous nystagmus, gaze, saccade, pursuit, Dix-Hallpike maneuver, side-lying maneuver, roll, and Romberg test), cervical Vestibular Myogenic Evoked Potential (c-VEMP), Computerized Dynamic Posturography (CDP) and Dizziness Handicap Inventory (DHI).

Results

Patients showed hearing loss in 10 (47.6%) and tinnitus in 4 (19.0%) cases. In ocular motor tests, patients had the most abnormal results in the pursuit test. 6 patients also had Benign Paroxysmal Positional Vertigo (BPPV) in the posterior canal. c-VEMP showed abnormal saccular function in 14 patients. In CDP, the composite scores were decreased relative to normal populations.

Conclusion

vestibular tests showed abnormal results in most patients. Vestibular abnormality could relate to persisting symptoms of mTBI patients.

Exposure to blast shock waves via the ear canal induces deficits in vestibular afferent function in rats

The ears are air-filled structures that are directly impacted during blast exposure. In addition to hearing loss and tinnitus, blast victims often complain of vertigo, dizziness and unsteady posture, suggesting that blast exposure induces damage to the vestibular end organs in the inner ear. However, the underlying mechanisms remain to be elucidated. In this report, single vestibular afferent activity and the vestibulo-ocular reflex (VOR) were investigated before and after exposure to blast shock waves (∼20 PSI) delivered into the left external ear canals of anesthetized rats. Single vestibular afferent activity was recorded from the superior branch of the left vestibular nerves of the blast-treated and control rats one day after blast exposure. Blast exposure reduced the spontaneous discharge rates of the otolith and canal afferents. Blast exposure also reduced the sensitivity of irregular canal afferents to sinusoidal head rotation at 0.5-2Hz. Blast exposure, however, resulted in few changes in the VOR responses to sinusoidal head rotation and translation. To the best of our knowledge, this is the first study that reports blast exposure-induced damage to vestibular afferents in an animal model. These results provide insights that may be helpful in developing biomarkers for early diagnosis of blast-induced vestibular deficits in military and civilian populations.

Vestibular and Balance Dysfunction Following Sport-Related Concussion

Purpose

Sport-related concussion is a significant public health concern that requires a multidisciplinary team to appropriately manage. Athletes often report dizziness and imbalance following concussion, and these symptoms can predict increased time to recover. Vestibular diagnostic evaluations provide important information regarding the athlete's oculomotor, gaze stability, and balance function in order to identify deficits for rehabilitation. These measures also describe objective function helpful for determining when an athlete is ready to return to play. The purpose of this clinical focus article is to provide background on the current understanding of the effects of concussion on the peripheral and central vestibular system, as well as information on a protocol that can be used for acute concussion assessment. Case studies describing 3 common postconcussion presentations will highlight the usefulness of this protocol.

Conclusion

Sport-related concussion is a highly visible disorder with many symptoms that may be evaluated in the vestibular clinic. A thoughtful protocol evaluating the typical presentation of these patients may help guide the multidisciplinary team in determining appropriate management and clearance for return to sport.

Long-Term Effects of Blast Exposure: A Functional Study in Rats Using an Advanced Blast Simulator

Anecdotal observations of blast victims indicate that significant neuropathological and neurobehavioral defects may develop at later stages of life. To pre-clinically model this phenomenon, we have examined neurobehavioral changes in rats up to 1 year after exposure to single and tightly coupled repeated blasts using an advanced blast simulator. Neurobehavioral changes were monitored at acute, sub-acute, and chronic time-points using Morris water maze test of spatial learning and memory, novel object recognition test of short-term memory, open field exploratory activity as a test of anxiety/depression, a rotating pole test for vestibulomotor function, and a rotarod balance test for motor coordination. Single and repeated blasts resulted in significant functional deficits at both acute and chronic time-points. In most functional tests, rats exposed to repeated blasts performed more poorly than rats exposed to single blast. Interestingly, several functional deficits post-blast were most pronounced at 6 months and beyond. Significant neuromotor impairments occurred at early stages after blast exposure and the severity increased with repeated exposures. The novel object recognition testing revealed short-term memory deficits at 6 and 12 months post-blast. The water maze test revealed impairments at acute and chronic stages after blast exposure. The most substantial changes in the blast-exposed rats were observed with the center time and margin time legacies in the open field exploration test at 6, 9, and 12 months post-blast. Notably, these two outcome measures were minimally altered acutely, recovered during sub-acute stages, and were markedly affected during the chronic stages after blast exposures and may implicate development of chronic anxiety and depressive-like behaviors.

Outcomes Associated With Blast Versus Nonblast-Related Traumatic Brain Injury in US Military Service Members and Veterans: A Systematic Review

OBJECTIVES

To systematically review the literature on comparative clinical and functional outcomes following blast-related versus nonblast-related traumatic brain injury (TBI) among US service members and Veterans.

DESIGN

MEDLINE search (January 2001 to June 2016) supplemented with hand search of reference lists and input from peer reviewers.

RESULTS

Thirty-one studies (in 33 articles) reported on health outcomes; only 2 were rated low risk of bias. There was variation in outcomes reported and methods of assessment. Blast and nonblast TBI groups had similar rates of depression, sleep disorders, alcohol misuse, vision loss, vestibular dysfunction, and functional status. Comparative outcomes were inconsistent with regard to posttraumatic stress disorder diagnosis or symptoms, headache, hearing loss, and neurocognitive function. Mortality, burn, limb loss, and quality of life were each reported in few studies, most with small sample sizes. Only 4 studies reported outcomes by blast injury mechanism.

CONCLUSIONS

Most clinical and functional outcomes appeared comparable in military service members and Veterans with TBI, regardless of blast exposure. Inconsistent findings and limited outcomes reporting indicate that more research is needed to determine whether there is a distinct pattern of impairments and comorbidities associated with blast-related TBI.

Longitudinal study of hyperbaric oxygen intervention on balance and affective symptoms in military service members with persistent post-concussive symptoms

BACKGROUND

Dizziness and imbalance are common after mild traumatic brain injury (mTBI). Hyperbaric oxygen (HBO2) has been proposed for persistent post-concussive symptoms after mTBI, but its effect on vestibular function is unknown.

OBJECTIVE

To describe balance function in military service-members before and after intervention, and to explore the influence of post-traumatic stress disorder (PTSD), anxiety, and depression on vestibular outcomes.

METHODS

Seventy-one participants with mTBI and seventy-five healthy adults without brain injury were enrolled (NCT01611194 and NCT01925963). mTBI participants were randomized to 40 HBO2 sessions or 40 sham chamber sessions over 12 weeks. Normative controls received no intervention. Balance and neuropsychological function were measured at baseline, 13 weeks, and 6 months.

RESULTS

The mTBI cohort performed worse than healthy controls on balance and gait measures and reported more affective symptoms. Some within-group improvements were noted at 13 weeks and 6 months. Significant between-intervention differences on balance measures were minimal but effects on postural control generally favored HBO2. Those with affective symptoms, particularly PTSD, had the most improvement in postural control and otolith function following 13 weeks of HBO2.

CONCLUSION

HBO2 may influence balance function after mTBI, particularly in those with affective symptoms.

Inertial Sensor-Based Assessment of Central Sensory Integration for Balance After Mild Traumatic Brain Injury

Introduction

Optimal balance control requires a complex integration of sensory information from the visual, vestibular, and proprioceptive systems. The goal of this study is to determine if the instrumented modified Clinical Test of Sensory Integration and Balance (mCTSIB) was impaired acutely after mild traumatic brain injury (mTBI) when postural sway under varying sensory conditions was measured with a wearable inertial sensor.

Materials and Methods

Postural sway was assessed in athletes who had sustained a mTBI within the past 2-3 d (n = 38) and control athletes (n = 81). Postural sway was quantified with a wearable inertial sensor (Opal; APDM, Inc.) during four varying sensory conditions of quiet stance: (1) eyes open (EO) firm surface, (2) eyes closed (EC) firm surface, (3) eyes open (EO) foam surface, and (4) eyes closed (EC) foam surface. Sensory reweighting deficits were computed by comparing the postural sway area in eyes closed versus eyes open conditions for firm and foam condition.

Results

Postural sway was higher for mTBI compared with the control group during three of the four conditions of instrumented mCTSIB (EO firm, EC firm, and EC foam; p < 0.05). Sensory reweighting deficits were evident for mTBI individuals compared with control group on foam surface (EC firm vs EO firm; p < 0.05) and not on firm surface (EC firm vs EO firm; p = 0.63).

Conclusions

The results from this study highlight the importance of detecting postural sway deficits during sensorimotor integration in mild TBI individuals.

Vestibular Test Patterns in the NICoE Intensive Outpatient Program Patient Population

The National Intrepid Center of Excellence (NICoE), on the campus of Walter Reed National Military Medical Center, was developed to help improve the lives of active duty service members (SMs) with traumatic brain injury (TBI) and comorbid behavioral health (BH) conditions. During the NICoE intensive outpatient program, SM who have all been identified as having some degree of TBI, undergo extensive interdisciplinary evaluations, including comprehensive vestibular assessment. These SMs sometimes present with vestibular symptoms ranging from lightheadedness to vertigo associated with the dual TBI/BH diagnoses, and vestibular testing results reported elsewhere have varied among this population. The study's purpose was to collate the vestibular test results obtained from a sample of the NICoE patients to determine if specific tests have a tendency to be abnormal in these SMs. Results indicate that oculomotor tests, particularly pursuit and saccade, were most often abnormal. The vertical subtests of the pursuit and saccade tests were abnormal more frequently than the horizontal subtests, suggesting that the vertical subtests should be utilized when evaluating the TBI population. Overall, oculomotor tests of vertical pursuit and saccades, as well as tests of central vestibular function, appear useful for detecting neurologic changes in active duty SMs with chronic symptoms after TBI.

Veterans have greater variability in their perception of binocular alignment

Introduction

A significant population of our wounded veterans suffer long-term functional consequences of visual deficit, disorientation, dizziness, and an impaired ability to read. These symptoms may be related to damage within the otolith pathways that contribute to ocular alignment. The purpose of this study was to compare perception of vertical and torsional ocular alignment between veterans and healthy controls in an upright and supine test position.

Materials and methods

Veterans (n = 26) with reports of dizziness were recruited from the East Orange Veterans Administration Hospital. Healthy controls (n = 26) were recruited from both Johns Hopkins University and the East Orange VA. Each subject performed 20 trials each of a novel vertical and torsional binocular alignment perception test. Veterans underwent semicircular canal and otolith pathway function testing.

Results

88% of the Veterans had an absent otolith response. Only the veterans had an abnormally large variability in perception of both vertical and torsional ocular alignment, and in both upright and supine position. Neither post-traumatic stress disorder, nor depression contributed to the misperception in binocular alignment.

Conclusions

Our novel method of measuring vertical and torsional misalignment distinguishes veterans with dizziness from healthy controls. The high prevalence of absent otolith function seems to explain this result. Further studies are needed to better understand the fundamental mechanism responsible for the increased variability of perception of binocular alignment.

Rehabilitation Assessment and Management of Neurosensory Deficits After Traumatic Brain Injury in the Polytrauma Veteran

Neurosensory deficits after traumatic brain injury can frequently lead to disability; therefore, diagnosis and treatment are important. Posttraumatic headaches typically resemble migraines and are managed similarly, but adjuvant physical therapy may be beneficial. Sleep-related issues are treated pharmacologically based on the specific sleep-related complaint. Fatigue is difficult to treat; cognitive behavioral therapy and aquatic therapy can be beneficial. Additionally, methylphenidate and modafinil have been used. Peripheral and central vestibular dysfunction causes dizziness and balance dysfunction, and the mainstay of treatment is vestibular physical therapy. Visual dysfunction incorporates numerous different diagnoses, which are frequently treated with specific rehabilitation programs.

Autonomic responses to blast overpressure can be elicited by exclusively exposing the ear in rats

Blast overpressure has become an increasing cause of brain injuries in both military and civilian populations. Though blast's direct effects on the cochlea and vestibular organs are active areas of study, little attention has been given to the ear's contribution to the overall spectrum of blast injury. Acute autonomic responses to blast exposure, including bradycardia and hypotension, can cause hypoxia and contribute to blast-induced neurotrauma. Existing literature suggests that these autonomic responses are elicited through blast impacting the thorax and lungs. We hypothesize that the unprotected ear also provides a vulnerable locus for blast to cause autonomic responses. We designed a blast generator that delivers controlled overpressure waves into the ear canal without impacting surrounding tissues in order to study the ear's specific contribution to blast injury. Anesthetized adult rats' left ears were exposed to a single blast wave ranging from 0 to 110 PSI (0-758 kPa). Blast exposed rats exhibited decreased heart rates and blood pressures with increased blast intensity, similar to results gathered using shock tubes and whole-body exposure in the literature. While rats exposed to blasts below 50 PSI (345 kPa) exhibited increased respiratory rate with increased blast intensity, some rats exposed to blasts higher than 50 PSI (345 kPa) stopped breathing immediately and ultimately died. These autonomic responses were significantly reduced in vagally denervated rats, again similar to whole-body exposure literature. These results support the hypothesis that the unprotected ear contributes to the autonomic responses to blast.

Vestibular Injury After Low-Intensity Blast Exposure

The increased use of close range explosives has led to a higher incidence of exposure to blast-related head trauma. Exposure to primary blast waves is a significant cause of morbidity and mortality. Active service members and civilians who have experienced blast waves report high rates of vestibular dysfunction, such as vertigo, oscillopsia, imbalance, and dizziness. Accumulating evidence suggests that exposure to blast-wave trauma produces damage to both the peripheral and central vestibular system; similar to previous findings that blast exposure results in damage to auditory receptors. In this study, mice were exposed to a 63 kPa peak blast-wave over pressure and were examined for vestibular receptor damage as well as behavioral assays to identify vestibular dysfunction. We observed perforations to the tympanic membrane in all blast animals. We also observed significant loss of stereocilia on hair cells in the cristae and macule up to 1 month after blast-wave exposure; damage that is likely permanent. Significant reductions in the ability to perform the righting reflex and balance on a rotating rod that lasted several weeks after blast exposure were prominent behavioral effects. We also observed a significant reduction in horizontal vestibuloocular reflex gain and phase lags in the eye movement responses that lasted many weeks following a single blast exposure event. OKN responses were absent immediately following blast exposure, but began to return after several weeks’ recovery. These results show that blast-wave exposure can lead to peripheral vestibular damage (possibly central deficits as well) and provides some insight into causes of vestibular dysfunction in blast-trauma victims.

Abnormal Turning and Its Association with Self-Reported Symptoms in Chronic Mild Traumatic Brain Injury

Turning is common in daily activity and requires rapid, coordinated reorientation of the head, trunk, and pelvis toward the new direction of travel. Yet, turning gait has not been well explored in populations with mild traumatic brain injury (mTBI) who may alter their turning behavior according to self-perceived symptoms or motor dysfunction. The purpose of this study was to examine turning velocities and coordination in adults with chronic mTBI (>3 months post-injury and still reporting balance complaints) during a task simulating everyday ambulation. We hypothesized that individuals with chronic mTBI would reduce their angular velocity when turning and increase the variability of head-pelvis coordination compared with controls, and that the reduction in velocity and increased variability would be associated with their self-reported symptom score. Forty-two adults (14 chronic mTBI, 28 controls) completed the Neurobehavioral Symptom Inventory before walking 12 laps around a marked course containing two 45-degree turns, four 90-degree turns, and two 135-degree turns. Inertial sensors collected angular velocities of the head and pelvis. After adjusting for covariates, participants with chronic mTBI had significantly slower lap times and peak angular velocities of the pelvis (p < 0.01) compared with the control group. The peak velocity timing (PVT) between peak velocities of the head and pelvis, and the variability of that timing was significantly greater in participants with chronic mTBI (p < 0.01). Within the chronic mTBI group, somatosensory symptoms were associated with slower angular velocities of the head and pelvis (p = 0.03) and increased PVT variability (p < 0.01). The results suggest individuals with chronic mTBI with worse somatic symptoms have impaired head stabilization during turning in situations similar to everyday life. These results encourage future research on turning gait to examine the causal relationship between symptoms and daily locomotor function in adults with chronic mTBI.

Post-blast treatment with Nociceptin/Orphanin FQ peptide (NOP) receptor antagonist reduces brain injury-induced hypoxia and signaling proteins in vestibulomotor-related brain regions

Mild traumatic brain injury (mTBI) diagnoses have increased due to aggressive sports and blast-related injuries, but the cellular mechanisms and pathology underlying mTBI are not completely understood. Previous reports indicate that Nociceptin Orphanin/FQ (N/OFQ), an endogenous neuropeptide, contributes to post-injury ischemia following mechanical brain injury, yet its specific role in cerebral hypoxia, vestibulomotor function and injury marker expression following blast-induced TBI is not known. This study is the first to identify a direct association of N/OFQ and its N/OFQ peptide (NOP) receptor with TBI-induced changes following a single 80psi head blast exposure in male rats. N/OFQ and NOP receptor expression increased in brain tissue and plasma following TBI, concurrent with vestibular dysfunction but preceding hypoxia and appearance of injury markers compared to sham rats. A single post-blast treatment with the NOP receptor antagonist, SB-612111, transiently improved acute vestibulomotor performance. It also prevented increases in markers of TBI-induced hypoxia, pro-apoptotic proteins and injury seen 8-10days post-blast. This study reveals an apparent role for the N/OFQ-NOP receptor system in blast TBI and suggests potential therapeutic utility of NOP receptor antagonists for mTBI.

Visual-vestibular processing deficits in mild traumatic brain injury

BACKGROUND

The search for reliable and valid signs and symptoms of mild traumatic brain injury (mTBI), commonly synonymous with concussion, has lead to a growing body of evidence that individuals with long-lasting, unremitting impairments often experience visual and vestibular symptoms, such as dizziness, postural and gait disturbances.

OBJECTIVE

Investigate the role of visual-vestibular processing deficits following concussion.

METHODS

A number of clinically accepted vestibular, oculomotor, and balance assessments as well as a novel virtual reality (VR)-based balance assessment device were used to assess adults with post-acute concussion (n = 14) in comparison to a healthy age-matched cohort (n = 58).

RESULTS

Significant between-group differences were found with the VR-based balance device (p = 0.001), with dynamic visual motion emerging as the most discriminating balance condition. The symptom reports collected after performing the oculomotor and vestibular tests: rapid alternating horizontal eye saccades, optokinetic stimulation, and gaze stabilization, were all sensitive to health status (p < 0.05), despite the absence of oculomotor abnormalities being observed, except for near-point convergence. The BESS, King-Devick, and Dynamic Visual Acuity tests did not detect between-group differences.

CONCLUSION

Postural and visual-vestibular tasks most closely linked to spatial and self-motion perception had the greatest discriminatory outcomes. The current findings suggest that mesencephalic and parieto-occipital centers and pathways may be involved in concussion.

Sensory organization test principally reflects utricular function

CONCLUSION

Our study showed that sensory organization test (SOT) could principally reflect utricular function, and our cut-score of VEST ratio (the indicator of inputs from the vestibular system in balance performance) in SOT could help to screen patients with unilateral peripheral vestibular dysfunction in non-fallers.

OBJECTIVES

We aimed to know SOT reflects the function of which vestibular end organs and to assess the possibility of screening patients with peripheral vestibular dysfunction in non-fall population by means of SOT.

METHODS

A total of 75 patients with unilateral peripheral vestibular dysfunction underwent SOT, ocular vestibular-evoked myogenic potential (oVEMP), cervical vestibular-evoked myogenic potential (cVEMP) and caloric tests.

RESULTS

Regression model indicated that oVEMP, as an independent variable, exerted the greatest influence on VEST ratio, followed by age and cVEMP. There were no significant differences in VEST ratio among groups with different extents of peripheral vestibular involvement (p > .05). VEST ratio in the vestibular impairment groups was significantly lower than in the control group and significantly higher than in fall group (p < .01). VEST ratio in group with normal oVEMP was significantly higher than in group with abnormal oVEMP (p = .013). The cut-score between populations with functional and dysfunctional vestibule was 0.649.

Semicircular Canal Pressure Changes During High-intensity Acoustic Stimulation

HYPOTHESIS

Acoustic stimulation generates measurable sound pressure levels in the semicircular canals.

BACKGROUND

High-intensity acoustic stimuli can cause hearing loss and balance disruptions. To examine the propagation of acoustic stimuli to the vestibular end-organs, we simultaneously measured fluid pressure in the cochlea and semicircular canals during both air- and bone-conducted sound presentation.

METHODS

Five full-cephalic human cadaveric heads were prepared bilaterally with a mastoidectomy and extended facial recess. Vestibular pressures were measured within the superior, lateral, and posterior semicircular canals, and referenced to intracochlear pressure within the scala vestibuli with fiber-optic pressure probes. Pressures were measured concurrently with laser Doppler vibrometry measurements of stapes velocity during stimulation with both air- and bone-conduction. Stimuli were pure tones between 100 Hz and 14 kHz presented with custom closed-field loudspeakers for air-conducted sounds and via commercially available bone-anchored device for bone-conducted sounds.

RESULTS

Pressures recorded in the superior, lateral, and posterior semicircular canals in response to sound stimulation were equal to or greater in magnitude than those recorded in the scala vestibuli (up to 20 dB higher). The pressure magnitudes varied across canals in a frequency-dependent manner.

CONCLUSION

High sound pressure levels were recorded in the semicircular canals with sound stimulation, suggesting that similar acoustical energy is transmitted to the semicircular canals and the cochlea. Since these intralabyrinthine pressures exceed intracochlear pressure levels, our results suggest that the vestibular end-organs may also be at risk for injury during exposure to high-intensity acoustic stimuli known to cause trauma in the auditory system.

Vestibular disorders following different types of head and neck trauma

This review focuses on the published literature on vestibular disorders following different types of head and neck trauma. Current knowledge of the different causes and underlying mechanisms of vestibular disorders, as well as the sites of organic damage, is presented. Non-organic mechanisms are also surveyed. The frequency of occurrence of vestibular symptoms, and of other accompanying subjective complaints, associated with different types of trauma is presented and related to the specific causes. Hypotheses about the pathogenesis of traumatic vestibular disorders are presented, and the knowledge derived from animal experiments is also discussed. We believe this to be a very important topic, since vestibular complaints in traumatic patients often remain undiagnosed or underestimated in clinical practice. This review article aims to suggest directions for additional research and to provide guidance to both the scientific and clinical practice communities.

Symptoms Associated with Vestibular Impairment in Veterans with Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a chronic and disabling, anxiety disorder resulting from exposure to life threatening events such as a serious accident, abuse or combat (DSM IV definition). Among veterans with PTSD, a common complaint is dizziness, disorientation and/or postural imbalance in environments such as grocery stores and shopping malls. The etiology of these symptoms in PTSD is poorly understood and some attribute them to anxiety or traumatic brain injury. There is a possibility that an impaired vestibular system may contribute to these symptoms since, symptoms of an impaired vestibular system include dizziness, disorientation and postural imbalance. To our knowledge, this is the first report to describe the nature of vestibular related symptoms in veterans with and without PTSD. We measured PTSD symptoms using the Posttraumatic Stress Disorder Checklist (PCL-C) and compared it to responses on vestibular function scales including the Dizziness Handicap Inventory (DHI), the Vertigo Symptom Scale Short Form (VSS-SF), the Chambless Mobility Inventory (CMI), and the Neurobehavioral Scale Inventory (NSI) in order to identify vestibular-related symptoms. Our findings indicate that veterans with worse PTSD symptoms report increased vestibular related symptoms. Additionally veterans with PTSD reported 3 times more dizziness related handicap than veterans without PTSD. Veterans with increased avoidance reported more vertigo and dizziness related handicap than those with PTSD and reduced avoidance. We describe possible contributing factors to increased reports of vestibular symptoms in PTSD, namely, anxiety, a vestibular component as well as an interactive effect of anxiety and vestibular impairment. We also present some preliminary analyses regarding the contribution of TBI. This data suggests possible evidence for vestibular symptom reporting in veterans with PTSD, which may be explained by possible underlying vestibular impairment, worthy of further exploration.

The potential for animal models to provide insight into mild traumatic brain injury: Translational challenges and strategies

Mild traumatic brain injury (mTBI) is a common health problem. There is tremendous variability and heterogeneity in human mTBI, including mechanisms of injury, biomechanical forces, injury severity, spatial and temporal pathophysiology, genetic factors, pre-injury vulnerability and resilience factors, and clinical outcomes. Animal models greatly reduce this variability and heterogeneity, and provide a means to study mTBI in a rigorous, controlled, and efficient manner. Rodent models, in particular, are time- and cost-efficient, and they allow researchers to measure morphological, cellular, molecular, and behavioral variables in a single study. However, inter-species differences in anatomy, morphology, metabolism, neurobiology, and lifespan create translational challenges. Although the term "mild" TBI is used often in the pre-clinical literature, clearly defined criteria for mild, moderate, and severe TBI in animal models have not been agreed upon. In this review, we introduce current issues facing the mTBI field, summarize the available research methodologies and previous studies in mTBI animal models, and discuss how a translational research approach may be useful in advancing our understanding and management of mTBI.

The Application of the International Classification of Functioning, Disability and Health to Functional Auditory Consequences of Mild Traumatic Brain Injury

This article reviews the auditory consequences of mild traumatic brain injury (mTBI) within the context of the International Classification of Functioning, Disability and Health (ICF). Because of growing awareness of mTBI as a public health concern and the diverse and heterogeneous nature of the individual consequences, it is important to provide audiologists and other health care providers with a better understanding of potential implications in the assessment of levels of function and disability for individual interdisciplinary remediation planning. In consideration of body structures and function, the mechanisms of injury that may result in peripheral or central auditory dysfunction in mTBI are reviewed, along with a broader scope of effects of injury to the brain. The activity limitations and participation restrictions that may affect assessment and management in the context of an individual's personal factors and their environment are considered. Finally, a review of management strategies for mTBI from an audiological perspective as part of a multidisciplinary team is included.

Labyrinthine concussion following gunshot injury: A case report

OBJECTIVE

Labyrinthine concussion due to a postauricular gunshot wound has not been well reported.

DESIGN

Retrospective chart review.

STUDY SAMPLE

We describe an otherwise healthy 22-year-old male who received a gunshot wound to the left mastoid and subsequently reported hearing loss and rotational vertigo.

RESULTS

Audiometric testing demonstrated significant inverted scoop shaped sensorineural hearing loss. Vestibular diagnostic testing indicated a significant uncompensated left peripheral vestibulopathy. Imaging demonstrated no structural changes to the middle ear or labyrinth, suggesting that the auditory and vestibular losses noted on diagnostic examination were likely due to labyrinthine concussion.

CONCLUSIONS

Labyrinthine concussion may lead to reduced vestibular reflex pathway following gunshot wounds to the temporal bone. Clinical presentation is likely to vary significantly among cases.

Posttraumatic dizziness and vertigo

Traumatic brain injury is an increasingly common public health issue, with the mild variant most clinically relevant for this chapter. Common causes of mild traumatic brain injury (mTBI) include motor vehicle accidents, athletics, and military training/deployment. Despite a range of clinically available testing platforms, diagnosis of mTBI remains challenging. Symptoms are primarily neurosensory, and include dizziness, hearing problems, headaches, cognitive, and sleep disturbances. Dizziness is nearly universally present in all mTBI patients, and is the easiest symptom to objectify for diagnosis. Aside from a thorough history and physical exam, in the near future specialized vestibular function tests will be key to mTBI diagnosis. A battery of oculomotor (antisaccade, predictive saccade) and vestibular tasks (head impulse test) has been demonstrated to sensitively and specifically identify individuals with acute mTBI. Vestibular therapy and rehabilitation have shown improvements for mTBI patients in cognitive function, ability to return to activities of daily living, and ability to return to work. Dizziness, as a contributor to short- and long-term disability following mTBI, is ultimately crucial not only for diagnosis but also for treatment.

Static and dynamic postural stability in veterans with combat-related mild traumatic brain injury

Persistent post-concussive symptoms are reported by 10-15% of individuals who suffer mild traumatic brain injury (mTBI), but their basis is often uncertain. One such symptom is disequilibrium, a sensation of impaired balance during standing and walking. The hypothesis for this study was that this subjective symptom is associated with objective and measurable deficits in static and dynamic postural stability. An infrared motion tracking system was used to record body motion during quiet standing and in response to waist perturbations in fourteen veterans (age 22-40 years, 13 male) of the Operations Enduring Freedom (OEF) and Iraqi Freedom (OIF), who had a history of mTBI that occurred 7 months to 7 years prior to testing. We compared body sway between veterans with mTBI reporting persistent disequilibrium (TD, n=8) and those with no vestibular symptoms (n=6), as well as to a group of non-veterans with no balance symptoms (n=10). Static postural stability was reduced in TD veterans in comparison to each of the other two groups (p<0.0002), most notably on a compliant surface with eyes closed. The TD group also had decreased dynamic stability of the upper trunk (p<0.05) and enhanced postural oscillations (p<0.02) following waist perturbations. Our findings support a physiological basis for persistent disequilibrium after mTBI and are consistent with impaired vestibular processing. Disruption of semicircular canal inputs is unlikely to be the cause, as head impulse responses were normal in all groups. The unexpected finding of dynamic postural oscillations requires further study but may indicate enhanced instability in sensorimotor networks responsible for postural control.

Blast Overpressure Waves Induce Transient Anxiety and Regional Changes in Cerebral Glucose Metabolism and Delayed Hyperarousal in Rats

Physiological alterations, anxiety, and cognitive disorders are strongly associated with blast-induced traumatic brain injury (blast TBI), and are common symptoms in service personnel exposed to blasts. Since 2006, 25,000–30,000 new TBI cases are diagnosed annually in U.S. Service members; increasing evidence confirms that primary blast exposure causes diffuse axonal injury and is often accompanied by altered behavioral outcomes. Behavioral and acute metabolic effects resulting from blast to the head in the absence of thoracic contributions from the periphery were examined, following a single blast wave directed to the head of male Sprague-Dawley rats protected by a lead shield over the torso. An 80 psi head blast produced cognitive deficits that were detected in working memory. Blast TBI rats displayed increased anxiety as determined by elevated plus maze at day 9 post-blast compared to sham rats; blast TBI rats spent significantly more time than the sham controls in the closed arms (p < 0.05; n = 8–11). Interestingly, anxiety symptoms were absent at days 22 and 48 post-blast. Instead, blast TBI rats displayed increased rearing behavior at day 48 post-blast compared to sham rats. Blast TBI rats also exhibited suppressed acoustic startle responses, but similar pre-pulse inhibition at day 15 post-blast compared to sham rats. Acute physiological alterations in cerebral glucose metabolism were determined by positron emission tomography 1 and 9 days post-blast using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). Global glucose uptake in blast TBI rat brains increased at day 1 post-blast (p < 0.05; n = 4–6) and returned to sham levels by day 9. Our results indicate a transient increase in cerebral metabolism following a blast injury. Markers for reactive astrogliosis and neuronal damage were noted by immunoblotting motor cortex tissue from day 10 post-blast in blast TBI rats compared to sham controls (p < 0.05; n = 5–6).

Objective vestibular testing of children with dizziness and balance complaints following sports-related concussions

OBJECTIVE

To conduct objective assessment of children with balance and vestibular complaints following sports-related concussions and identify the underlying deficits by analyzing laboratory test outcomes.

STUDY DESIGNS

Case series with chart review.

SETTING

Pediatric tertiary care facility.

SUBJECTS AND METHODS

Medical records were reviewed of 42 pediatric patients with balance and/or vestibular complaints following sports-related concussions who underwent comprehensive laboratory testing on their balance and vestibular function. Patients' characteristics were summarized and results analyzed.

RESULTS

More than 90% of the children with protracted dizziness or imbalance following sports-related concussion had at least 1 abnormal finding from the comprehensive balance and vestibular evaluation. The most frequent deficit was found in dynamic visual acuity test, followed by Sensory Organization Test and rotational test. Patient's balance problem associated with concussion seemed to be primarily instigated by vestibular dysfunction. Furthermore, semicircular canal dysfunction was involved more often than dysfunction of otolith organs. Yet, <10% of the children experienced a hearing loss following sports-related concussion.

CONCLUSIONS

Vestibular impairment is common among children with protracted dizziness or imbalance following sports-related concussion. Our study demonstrated that proper and thorough evaluation is imperative to identify these underlying deficits and laboratory tests were helpful in the diagnosis and recommendation of following rehabilitations.