Association of Traumatic Brain Injury With Vestibular Dysfunction and Dizziness in Post-9/11 Veterans

Health conditions seen frequently in hospitalized United States Veterans who served after 9/11/2001: A scoping review

BACKGROUND

Hospitalists working outside the Veterans Affairs (VA) system frequently will serve Veterans receiving care for acute conditions and/or awaiting transfer to VA facilities.

OBJECTIVE

To perform a scoping review of health conditions and associated outcomes relevant to hospital medicine in US Veterans who served in active duty or reserve deployed roles after November 9, 2001.

METHODS

A search of MEDLINE and Embase was performed using a combination of terms related to military service period and health conditions, yielding 5634 citations published after January 1, 2013.

STUDY SELECTION AND DATA EXTRACTION

Two reviewers performed independent screening at the title/abstract and later at the full-text levels. Conflicts at both stages were resolved through discussion. Single reviewers extracted data and synthesized results into three categories: (1) mental health and nonblast trauma, (2) neurologic outcomes, and (3) other conditions, including cardiovascular and respiratory outcomes.

RESULTS

Of 85 included studies, 19 focused on cardiovascular, respiratory, autoimmune, and multisystem outcomes; 38 focused on mental health and nonblast trauma; and 28 focused on traumatic brain injury and neurologic outcomes. Studies showed high rates of comorbid mental health diagnoses and suicide-related behaviors relative to non-Veteran populations, as well as relatively younger incidence of cardiovascular and respiratory chronic conditions, such as atrial fibrillation.

CONCLUSIONS

Most studied health conditions among Veterans of post-9/11 conflicts have focused on areas of particular importance to the VA. However, significant gaps remain, particularly in understanding the correlation between specific exposures and clinical outcomes currently observed and to be anticipated in the future in this population.

Traumatic brain injury: molecular biomarkers, genetics, secondary consequences, and medical management

Traumatic brain injury (TBI) has reached epidemic proportions worldwide. The consequences of TBI can be severe even with repetitive mild trauma. If death and coma are avoided, the consequences of TBI in the long term typically involve dizziness, sleep disturbances, headache, seizures, cognitive impairment, focal deficits, depression, and anxiety. The severity of brain injury is a significant predictor of outcome. However, the heterogenous nature of the injury makes prognosis difficult. The present review of the literature focuses on the genetics of TBI including genome wide (GWAS) data and candidate gene associations, among them brain-derived neurotrophic factor (BDNF) with TBI and development of post-traumatic epilepsy (PTE). Molecular biomarkers of TBI are also discussed with a focus on proteins and the inflammatory protein IL1-β. The secondary medical sequela to TBI of cognitive impairment, PTE, headache and risk for neurodegenerative disorders is also discussed. This overview of TBI concludes with a review and discussion of the medical management of TBI and the medicines used for and being developed at the preclinical and clinical stages for the treatment of TBI and its host of life-debilitating symptoms.

Blast-related mild TBI: LIMBIC-CENC focused review with implications commentary

BACKGROUND

A significant factor for the high prevalence of traumatic brain injury (TBI) among U.S. service members is their exposure to explosive munitions leading to blast-related TBI. Our understanding of the specific clinical effects of mild TBI having a component of blast mechanism remains limited compared to pure blunt mechanisms.

OBJECTIVE

The purpose of this review is to provide a synopsis of clinical research findings on the long-term effects of blast-related mild TBI derived to date from the Long-Term Impact of Military-Relevant Brain Injury Consortium - Chronic Effects of Neurotrauma Consortium (LIMBIC-CENC).

METHODS

Publications on blast-related mild TBI from LIMBIC-CENC and the LIMBIC-CENC prospective longitudinal study (PLS) cohort were reviewed and their findings summarized. Findings from the broader literature on blast-related mild TBI that evaluate similar outcomes are additionally reviewed for a perspective on the state of the literature.

RESULTS

The most consistent and compelling evidence for long-term effects of blast-related TBI is for poorer psychological health, greater healthcare utilization and disability levels, neuroimaging impacts on brain structure and function, and greater headache impact on daily life. To date, evidence for chronic cognitive performance deficits from blast-related mild TBI is limited, but futher research including crucial longitudinal data is needed.

CONCLUSION

Commentary is provided on: how LIMBIC-CENC findings assimilate with the broader literature; ongoing research gaps alongside future research needs and priorities; how the scientific community can utilize the LIMBIC-CENC database for independent or collaborative research; and how the evidence from the clinical research should be assimilated into clinical practice.

Exploring the relationship between sleep apnea and vestibular symptoms following traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a complex health problem in military veterans and service members (V/SM) that often involves comorbid vestibular impairment. Sleep apnea is another comorbidity that may exacerbate, and/or be exacerbated by, vestibular dysfunction.

OBJECTIVE

To examine the relationship between sleep apnea and vestibular symptoms in V/SM diagnosed with TBI of any severity.

DESIGN

Multicenter cohort study; cross-sectional sample.

SETTING

In-patient TBI rehabilitation units within five Veterans Affairs (VA) Polytrauma Rehabilitation Centers.

PARTICIPANTS

V/SM with a diagnosis of TBI (N = 630) enrolled in the VA TBI Model Systems study.

INTERVENTION

Not applicable.

METHODS

A multivariable regression model was used to evaluate the association between sleep apnea and vestibular symptom severity while controlling for relevant covariates, for example, posttraumatic stress disorder (PTSD).

MAIN OUTCOME MEASURES

Lifetime history of sleep apnea was determined via best source reporting. Vestibular disturbances were measured with the 3-item Vestibular subscale of the Neurobehavioral Symptom Inventory (NSI).

RESULTS

One third (30.6%) of the sample had a self-reported sleep apnea diagnosis. Initial analysis showed that participants who had sleep apnea had more severe vestibular symptoms (M = 3.84, SD = 2.86) than those without sleep apnea (M = 2.88, SD = 2.67, p < .001). However, when the data was analyzed via a multiple regression model, sleep apnea no longer reached the threshold of significance as a factor associated with vestibular symptoms. PTSD severity was shown to be significantly associated with vestibular symptoms within this sample (p < .001).

CONCLUSION

Analysis of these data revealed a relationship between sleep apnea and vestibular symptoms in V/SM with TBI. The significance of this relationship was affected when PTSD symptoms were factored into a multivariable regression model. However, given that the mechanisms and directionality of these relationships are not yet well understood, we assert that in terms of clinical relevance, providers should emphasize screening for each of the three studied comorbidities (sleep apnea, vestibular symptoms, and PTSD).

Prevalence and Risk Factors of Self-reported Dizziness in Post-9/11 Service Members and Veterans

INTRODUCTION

Dizziness is prevalent in the general population, but little is known about its prevalence in the U.S. military population. Dizziness is commonly associated with blast exposure and traumatic brain injury (TBI), but the potential independent contributions of blast and TBI have yet to be evaluated. This study's goal was to estimate the prevalence of dizziness among post-9/11 service members and Veterans and to examine independent and joint associations between military TBI history, blast exposure, and self-reported dizziness.

MATERIALS AND METHODS

The study sample consisted of service members (n = 424) and recently separated (< ∼2.5 years) Veterans (n = 492) enrolled in the Noise Outcomes in Service members Epidemiology (NOISE) Study. We examined associations between self-reported history of probable TBI and blast exposure and recent dizziness using logistic regression. Models were stratified by service member versus Veteran status and adjusted to account for potentially confounding demographic and military characteristics.

RESULTS

Overall, 22% of service members and 31% of Veterans self-reported dizziness. Compared to those with neither TBI nor blast exposure history, both service members and Veterans with TBI (with or without blast) were three to four times more likely to self-report dizziness. Those with blast exposure but no TBI history were not more likely to self-report dizziness. There was no evidence of an interaction effect between blast exposure and a history of TBI on the occurrence of dizziness.

CONCLUSION

Self-reported dizziness was prevalent in this sample of service members and Veterans. Probable TBI history, with or without blast exposure, was associated with dizziness, but blast exposure without TBI history was not. This suggests that treatment guidelines for TBI-related dizziness may not need to be tailored to the injury mechanism. However, future efforts should be directed toward the understanding of the pathophysiology of TBI on self-reported dizziness, which is fundamental to the design of treatment strategies.

Wearable Sensors Detect Movement Differences in the Portable Warrior Test of Tactical Agility After mTBI in Service Members

INTRODUCTION

Assessment of functional recovery of service members following a concussion is central to their return to duty. Practical military-relevant performance-based tests are needed for identifying those who might need specialized rehabilitation, for evaluating the progress of recovery, and for making return-to-duty determinations. One such recently developed test is the 'Portable Warrior Test of Tactical Agility' (POWAR-TOTAL) assessment designed for use following concussion in an active duty population. This agility task involves maneuvers used in military training, such as rapid stand-to-prone and prone-to-stand transitions, combat rolls, and forward and backward running. The effect of concussion on the performance of such maneuvers has not been established.

MATERIALS AND METHODS

The Institutional Review Board-approved study was conducted at Ft. Bragg, North Carolina, on 57 healthy control (HC) service members (SMs) and 42 well-matched SMs who were diagnosed with concussion and were referred for physical therapy with the intent to return to duty. Each study participant performed five consecutive trials of the POWAR-TOTAL task at full exertion while wearing inertial sensors, which were used to identify the constituent task maneuvers, or phases, and measure their durations. Statistical analyses were performed on durations of three main phases: (1) rising from prone and running, (2) lowering from vertical to prone, and (3) combat rolls.

RESULTS

None of the three phases showed significant correlation with age (range 18-45 years) in either group. Gradual improvement in all three phase durations across five trials was observed in the HC group, but not in the concussed group. On average, control subjects performed significantly faster (P < .004 or less) than concussed subjects in all trials in the lowering and rolling phases, but less so in the rising/running phase. Membership in the concussed group had a strong effect on the lowering phase (Cohen's d = 1.05), medium effect on the rolling phase (d = 0.72), and small effect on the rising/running phase (d = 0.49). Individuals in the HC group who had a history of prior concussions were intermediate between the concussed group and the never-concussed group in the lowering and rolling phases. Duration of transitional movements (lowering from standing to prone and combat rolls) was better at differentiating individuals' performance by group (receiver operating characteristic area under the curve [AUC] = 0.83) than the duration of the entire POWAR-TOTAL task (AUC = 0.71).

CONCLUSIONS

Inertial sensor analysis reveals that rapid transitional movements (such as lowering from vertical to prone position and combat rolls) are particularly discriminative between SMs recovering from concussion and their concussion-free peers. This analysis supports the validity of POWAR-TOTAL as a useful tool for therapists who serve military SMs.

Dizziness After Traumatic Brain Injury: A Prospective TRACK-TBI Analysis of Risk Factors, Quality of Life, and Neurocognitive Effects

OBJECTIVE

To determine the longitudinal incidence of dizziness and its association with demographic factors, neurocognitive effects, functionality, and quality of life.

STUDY DESIGN

Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) is a prospective, longitudinal cohort study in which TBI patients were assessed at the emergency department and 2-week, 3-month, 6-month, and 12-month follow-up via telephone and/or in-person visits.

SETTING

Multicenter study in emergency departments of 18 academic medical centers in the United States.

PATIENTS

A total of 1,514 patients 17 years or older with a diagnosis of TBI, injury occurrence within 24 hours of admission, fluency in English or Spanish, and completed Rivermead Post-Concussion Symptoms Questionnaire (RPQ) at 12 months were enrolled between February 2014 and August 2018.

MAIN OUTCOME MEASURE

RPQ, Short Form-12 Version 2, Wechsler Adult Intelligence Scale IV, Trail Making Test, Patient Health Questionnaire-9, PROMIS-PAIN, and Glasgow Outcome Scale-Extended Revised. The primary outcome measure was a self-report of "feelings of dizziness" on RPQ at 12 months post-TBI.

RESULTS

Of the 1,514 participants, 1,002 (66%) were male and 512 (34%) were female. The mean age was 41.6 (SD, 17.4) years. At 12 months, 26% experienced dizziness, with 9% experiencing moderate or severe dizziness. Dizziness was strongly associated with headache (odds ratio [OR], 3.45; 95% confidence interval [CI], 2.92-4.07; p < 0.001), nausea (OR, 4.43; 95% CI, 3.45-5.69; p < 0.001), worse hearing (OR, 3.57; 95% CI, 2.64-4.82; p < 0.001), noise sensitivity (OR, 3.02; 95% CI, 2.54-3.59; p < 0.001), and light sensitivity (OR, 3.51; 95% CI, 2.91-4.23; p < 0.001). In multivariable regression models, participants with severe dizziness demonstrated lower performance compared with those without new or worse dizziness on the Wechsler Adult Intelligence Scale IV (-6.64; p < 0.001), Trail Making Test part A (7.90; p = 0.003) and part B (19.77; p = 0.028), and Short Form-12 physical (-13.60; p < 0.001) and mental health (-11.17; p < 0.001), after controlling for age, sex, education, and TBI severity.

CONCLUSION

Dizziness is common among TBI patients and relates to quality of life and neurocognitive performance.

Disruptive Dizziness Among Post-9/11 Veterans With Deployment-Related Traumatic Brain Injury

OBJECTIVE

To identify disruption due to dizziness symptoms following deployment-related traumatic brain injury (TBI) and factors associated with receiving diagnoses for these symptoms.

SETTING

Administrative medical record data from the Department of Veterans Affairs (VA).

PARTICIPANTS

Post-9/11 veterans with at least 3 years of VA care who reported at least occasional disruption due to dizziness symptoms on the comprehensive TBI evaluation.

DESIGN

A cross-sectional, retrospective, observational study.

MAIN MEASURES

International Classification of Diseases, Ninth Revision, Clinical Modification diagnosis codes of dizziness, vestibular dysfunction, and other postconcussive conditions; neurobehavioral Symptom Inventory.

RESULTS

Increased access to or utilization of specialty care at the VA was significant predictors of dizziness and/or vestibular dysfunction diagnoses in the fully adjusted model. Veterans who identified as Black non-Hispanic and those with substance use disorder diagnoses or care were substantially less likely to receive dizziness and vestibular dysfunction diagnoses.

CONCLUSIONS

Access to specialty care was the single best predictor of dizziness and vestibular dysfunction diagnoses, underscoring the importance of facilitating referrals to and utilization of specialized, comprehensive clinical facilities or experts for veterans who report disruptive dizziness following deployment-related TBI. There is a clear need for an evidence-based pathway to address disruptive symptoms of dizziness, given the substantial variation in audiovestibular tests utilized by US providers by region and clinical specialty. Further, the dearth of diagnoses among Black veterans and those in more rural areas underscores the potential for enhanced cultural competency among providers, telemedicine, and patient education to bridge existing gaps in the care of dizziness.

A Comparison of Generalized and Individualized Vestibular Rehabilitation Therapy in a Military TBI Sample

OBJECTIVE

To compare clinical outcomes between active duty service members receiving generalized versus individualized vestibular rehabilitation treatment (GVRT and IVRT, respectively) for persistent vestibular-related symptoms following mild traumatic brain injury (mTBI).

SETTING

An outpatient TBI rehabilitation clinic.

PARTICIPANTS

Fifty-seven participants with persistent vestibular-related symptoms following mTBI were randomly assigned to the GVRT (n = 28) or IVRT (n = 29) group, stratified by dizziness-related impairment severity. Forty-two participants (n = 21 per group) completed the posttreatment evaluation and were included in analyses.

DESIGN

We employed a single-site, randomized, pre-/posttest experimental design. The GVRT program consisted of eight 45-minute group-based treatment sessions and IVRT consisted of three 30-minute one-on-one treatment sessions both to be completed within 8 weeks. Group assignment was not blinded to study personnel or participants. Research evaluations were completed approximately 2 weeks prior to treatment initiation and following treatment completion.

MAIN MEASURES

Outcome measures included Dizziness Handicap Inventory (DHI) and Activities-specific Balance Confidence Scale (ABC) total scores, Sensory Organization Test (SOT) composite equilibrium and sensory input ratio scores, Head Shake SOT (HS-SOT) conditions 2 and 5, and horizontal and vertical Dynamic Visual Acuity. Separate mixed-effects models were used to compare clinical outcomes between the GVRT and IVRT groups.

RESULTS

Both groups demonstrated significant improvement from pre- to posttreatment on self-reported dizziness-related impairment (DHI [F(1,41) = 16.28, P < .001]) and balance performance with and without head movement (composite equilibrium score [F(1,41) = 16.58, P < .001, effect size [ES] = 0.43], somatosensory [F(1,41) = 6.79, P = .013, ES = 0.26], visual [F(1,41) = 6.49, P = .015, ES = 0.29], vestibular [F(1,41) = 22.31, P < .001, ES = 0.55], and HS-SOT condition 5 [F(1,38) = 23.98, P < .001, ES = 0.64]). Treatment effects did not differ between groups on any of the outcome measures.

CONCLUSIONS

We provide preliminary evidence that differences in clinical outcomes do not exist between participants receiving generalized versus individualized VR. Further research is needed to determine comparative effectiveness between these 2 treatment approaches for persistent vestibular-related symptoms following mTBI.

Clinical research findings from the long-term impact of military-relevant brain injury consortium-Chronic Effects of Neurotrauma Consortium (LIMBIC-CENC) 2013-2021

This is a summary of the published research from the 14 observational, longitudinal and big-data, epidemiological studies supported by the LIMBIC-CENC program from 2013-2021 examining the long-term effects of combat-related traumatic brain injury (TBI). Findings from these 43 primary and secondary analyses include: 1) unique fluid, advanced neuroimaging and electrophysiologic biomarkers associated with mild traumatic brain injury (mTBI), number of mTBIs and related dysfunction, 2) increases in a range of chronic difficulties, including neurosensory, sleep, pain, cognitive deficits, behavioral disorders, overall symptom burden, healthcare costs and service-connected disability, associated with mTBI, all-severity traumatic brain injury (TBI), blast exposure, and number of mTBIs, and 3) increases in the risk for suicide and neurodegeneration, including dementia and Parkinson's disease, associated with mTBI and all-severity TBI. Ongoing LIMBIC-CENC longitudinal and epidemiologic research will clarify, confirm and expand upon these findings.

The Impact of Deployment and Combat Exposure on Physical Health Among Military Personnel: A Systematic Review of Incidence, Prevalence, and Risks

OBJECTIVES

The impact of deployment and combat on mental health of military personnel is well described. Less evidence is available to demonstrate and summarize the incidence, prevalence, and risks of these exposures on physical health. This study aims to (1) systematically review the available literature to determine the incidence and prevalence of physical health conditions among military personnel during and after deployment and (2) investigate the risks of deployment and combat exposure on physical health.

METHODS

A systematic review using the PubMed and EMBASE databases was performed. The literature search was limited to articles written in English, published from 2000 through 2019. The quality of studies was assessed with the Joanna Briggs Institute Appraisal Checklist. The results were grouped per system or condition of physical health and presented by forest plots without a combined effect size estimate.

RESULTS

Thirty-two studies were found eligible for this review. We identified a wide variety of incidence and prevalence rates of numerous physical health conditions and a high heterogeneity across the included studies. Acute respiratory symptoms, diarrhea, musculoskeletal injuries, pain, and tinnitus were found to be the most incident or prevalent conditions. Except for hearing loss, no associations with deployment and physical health problems were observed. An increased risk for asthma, headache, hearing loss, and pain was reported in relation to the combat exposure.

CONCLUSION

Given the characteristics of included studies and extracted data, the magnitude of the found differences in incidence and prevalence rates is most likely to be due to methodological heterogeneity. The specific exposures (e.g., infrastructure, environmental conditions, and activities during deployment) are suggested to be the determinants of (post) deployment physical health problems and need to be addressed to decrease the impact of deployment. Findings from this systematic review highlight which conditions should be addressed in response to service members' health and wellness needs in the (post)deployment phase and may be used by clinicians, researchers, and policy-makers. However, knowledge gaps regarding the potential risk factors during deployment and combat still exist. Studies using consistent methods to define and measure the physical health conditions and specific exposures are needed.

The Enduring Health Consequences of Combat Trauma: a Legacy of Chronic Disease

BACKGROUND

A better understanding of the long-term health effects of combat injury is important for the management of veterans' health in the Department of Defense (DoD) and Veterans Affairs (VA) health care systems and may have implications for primary care management of civilian trauma patients.

OBJECTIVE

To determine the impact of traumatic injury on the subsequent development of hypertension (HTN), diabetes mellitus (DM), and coronary artery disease (CAD) after adjustment for sociodemographic, health behavior, and mental health factors.

DESIGN

Retrospective cohort study of current and former US military personnel with data obtained from both the DoD and VA health care systems.

PARTICIPANTS

Combat injured (n = 8727) service members between 1 February 2002 and 14 June 2016 randomly selected from the DoD Trauma Registry matched 1:1 based on year of birth, sex, and branch of service to subjects that deployed to a combat zone but were not injured.

MAIN MEASURES

Traumatic injury, stratified by severity, compared with no documented injury. Diagnoses of HTN, DM, and CAD defined by International Classification of Diseases 9th or 10th Revision Clinical Modification codes.

KEY RESULTS

After adjustment, severe traumatic injury was significantly associated with HTN (HR 2.78, 95% CI 2.18-3.55), DM (HR 4.45, 95% CI 2.15-9.18), and CAD (HR 4.87, 95% CI 2.11-11.25), compared with no injury. Less severe injury was associated with HTN (HR 1.14, 95% CI 1.05-1.24) and CAD (HR 1.62, 95% CI 1.11-2.37).

CONCLUSIONS

Severe traumatic injury is associated with the subsequent development of HTN, DM, and CAD. These findings have profound implications for the primary care of injured service members in both the DoD/VA health systems and may be applicable to civilian trauma patients as well. Further exploration of pathophysiologic, health behavior, and mental health changes after trauma is warranted to guide future intervention strategies.