Soldiers with Occult Traumatic Brain Injury

The AURORA Study: a longitudinal, multimodal library of brain biology and function after traumatic stress exposure

Adverse posttraumatic neuropsychiatric sequelae (APNS) are common among civilian trauma survivors and military veterans. These APNS, as traditionally classified, include posttraumatic stress, postconcussion syndrome, depression, and regional or widespread pain. Traditional classifications have come to hamper scientific progress because they artificially fragment APNS into siloed, syndromic diagnoses unmoored to discrete components of brain functioning and studied in isolation. These limitations in classification and ontology slow the discovery of pathophysiologic mechanisms, biobehavioral markers, risk prediction tools, and preventive/treatment interventions. Progress in overcoming these limitations has been challenging because such progress would require studies that both evaluate a broad spectrum of posttraumatic sequelae (to overcome fragmentation) and also perform in-depth biobehavioral evaluation (to index sequelae to domains of brain function). This article summarizes the methods of the Advancing Understanding of RecOvery afteR traumA (AURORA) Study. AURORA conducts a large-scale (n = 5000 target sample) in-depth assessment of APNS development using a state-of-the-art battery of self-report, neurocognitive, physiologic, digital phenotyping, psychophysical, neuroimaging, and genomic assessments, beginning in the early aftermath of trauma and continuing for 1 year. The goals of AURORA are to achieve improved phenotypes, prediction tools, and understanding of molecular mechanisms to inform the future development and testing of preventive and treatment interventions.

Acute Assessment of Traumatic Brain Injury and Post-Traumatic Stress After Exposure to a Deployment-Related Explosive Blast

Introduction

Traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD) are two of the signature injuries in military service members who have been exposed to explosive blasts during deployments to Iraq and Afghanistan. Acute stress disorder (ASD), which occurs within 2–30 d after trauma exposure, is a more immediate psychological reaction predictive of the later development of PTSD. Most previous studies have evaluated service members after their return from deployment, which is often months or years after the initial blast exposure. The current study is the first large study to collect psychological and neuropsychological data from active duty service members within a few days after blast exposure.

Materials and Methods

Recruitment for blast-injured TBI patients occurred at the Air Force Theater Hospital, 332nd Air Expeditionary Wing, Joint Base Balad, Iraq. Patients were referred from across the combat theater and evaluated as part of routine clinical assessment of psychiatric and neuropsychological symptoms after exposure to an explosive blast. Four measures of neuropsychological functioning were used: the Military Acute Concussion Evaluation (MACE); the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS); the Headminder Cognitive Stability Index (CSI); and the Automated Neuropsychological Assessment Metrics, Version 4.0 (ANAM4). Three measures of combat exposure and psychological functioning were used: the Combat Experiences Scale (CES); the PTSD Checklist-Military Version (PCL-M); and the Acute Stress Disorder Scale (ASDS). Assessments were completed by a deployed clinical psychologist, clinical social worker, or mental health technician.

Results

A total of 894 patients were evaluated. Data from 93 patients were removed from the data set for analysis because they experienced a head injury due to an event that was not an explosive blast (n = 84) or they were only assessed for psychiatric symptoms (n = 9). This resulted in a total of 801 blast-exposed patients for data analysis. Because data were collected in-theater for the initial purpose of clinical evaluation, sample size varied widely between measures, from 565 patients who completed the MACE to 154 who completed the CES. Bivariate correlations revealed that the majority of psychological measures were significantly correlated with each other (ps ≤ 0.01), neuropsychological measures were correlated with each other (ps ≤ 0.05), and psychological and neuropsychological measures were also correlated with each other (ps ≤ 0.05).

Conclusions

This paper provides one of the first descriptions of psychological and neuropsychological functioning (and their inter-correlation) within days after blast exposure in a large sample of military personnel. Furthermore, this report describes the methodology used to gather data for the acute assessment of TBI, PTSD, and ASD after exposure to an explosive blast in the combat theater. Future analyses will examine the common and unique symptoms of TBI and PTSD, which will be instrumental in developing new assessment approaches and intervention strategies.

A Compact Blast-Induced Traumatic Brain Injury Model in Mice

Blast-induced traumatic brain injury (bTBI) is a common injury on the battlefield and often results in permanent cognitive and neurological abnormalities. We report a novel compact device that creates graded bTBI in mice. The injury severity can be controlled by precise pressures that mimic Friedlander shockwave curves. The mouse head was stabilized with a head fixator, and the body was protected with a metal shield; shockwave durations were 3 to 4 milliseconds. Reflective shockwave peak readings at the position of the mouse head were 12 6 2.6 psi, 50 6 20.3 psi, and 100 6 33.1 psi at 100, 200, and 250 psi predetermined driver chamber pressures, respectively. The bTBIs of 250 psi caused 80% mortality, which decreased to 27% with the metal shield. Brain and lung damage depended on the shockwave duration and amplitude. Cognitive deficits were assessed using the Morris water maze, Y-maze, and open-field tests. Pathological changes in the brain included disruption of the blood-brain barrier, multifocal neuronal and axonal degeneration, and reactive gliosis assessed by Evans Blue dye extravasation, silver and Fluoro-Jade B staining, and glial fibrillary acidic protein immunohistochemistry, respectively. Behavioral and pathological changes were injury severity-dependent. This mouse bTBI model may be useful for investigating injury mechanisms and therapeutic strategies associated with bTBI.

Blast-Associated Shock Waves Result in Increased Brain Vascular Leakage and Elevated ROS Levels in a Rat Model of Traumatic Brain Injury

Blast-associated shock wave-induced traumatic brain injury (bTBI) remains a persistent risk for armed forces worldwide, yet its detailed pathophysiology remains to be fully investigated. In this study, we have designed and characterized a laboratory-scale shock tube to develop a rodent model of bTBI. Our blast tube, driven by a mixture of oxygen and acetylene, effectively generates blast overpressures of 20–130 psi, with pressure-time profiles similar to those of free-field blast waves. We tested our shock tube for brain injury response to various blast wave conditions in rats. The results show that blast waves cause diffuse vascular brain damage, as determined using a sensitive optical imaging method based on the fluorescence signal of Evans Blue dye extravasation developed in our laboratory. Vascular leakage increased with increasing blast overpressures and mapping of the brain slices for optical signal intensity indicated nonhomogeneous damage to the cerebral vasculature. We confirmed vascular leakage due to disruption in the blood-brain barrier (BBB) integrity following blast exposure. Reactive oxygen species (ROS) levels in the brain also increased with increasing blast pressures and with time post-blast wave exposure. Immunohistochemical analysis of the brain sections analyzed at different time points post blast exposure demonstrated astrocytosis and cell apoptosis, confirming sustained neuronal injury response. The main advantages of our shock-tube design are minimal jet effect and no requirement for specialized equipment or facilities, and effectively generate blast-associated shock waves that are relevant to battle-field conditions. Overall data suggest that increased oxidative stress and BBB disruption could be the crucial factors in the propagation and spread of neuronal degeneration following blast injury. Further studies are required to determine the interplay between increased ROS activity and BBB disruption to develop effective therapeutic strategies that can prevent the resulting cascade of neurodegeneration.

Traumatic brain injury detection using electrophysiological methods

Measuring neuronal activity with electrophysiological methods may be useful in detecting neurological dysfunctions, such as mild traumatic brain injury (mTBI). This approach may be particularly valuable for rapid detection in at-risk populations including military service members and athletes. Electrophysiological methods, such as quantitative electroencephalography (qEEG) and recording event-related potentials (ERPs) may be promising; however, the field is nascent and significant controversy exists on the efficacy and accuracy of the approaches as diagnostic tools. For example, the specific measures derived from an electroencephalogram (EEG) that are most suitable as markers of dysfunction have not been clearly established. A study was conducted to summarize and evaluate the statistical rigor of evidence on the overall utility of qEEG as an mTBI detection tool. The analysis evaluated qEEG measures/parameters that may be most suitable as fieldable diagnostic tools, identified other types of EEG measures and analysis methods of promise, recommended specific measures and analysis methods for further development as mTBI detection tools, identified research gaps in the field, and recommended future research and development thrust areas. The qEEG study group formed the following conclusions: (1) Individual qEEG measures provide limited diagnostic utility for mTBI. However, many measures can be important features of qEEG discriminant functions, which do show significant promise as mTBI detection tools. (2) ERPs offer utility in mTBI detection. In fact, evidence indicates that ERPs can identify abnormalities in cases where EEGs alone are non-disclosing. (3) The standard mathematical procedures used in the characterization of mTBI EEGs should be expanded to incorporate newer methods of analysis including non-linear dynamical analysis, complexity measures, analysis of causal interactions, graph theory, and information dynamics. (4) Reports of high specificity in qEEG evaluations of TBI must be interpreted with care. High specificities have been reported in carefully constructed clinical studies in which healthy controls were compared against a carefully selected TBI population. The published literature indicates, however, that similar abnormalities in qEEG measures are observed in other neuropsychiatric disorders. While it may be possible to distinguish a clinical patient from a healthy control participant with this technology, these measures are unlikely to discriminate between, for example, major depressive disorder, bipolar disorder, or TBI. The specificities observed in these clinical studies may well be lost in real world clinical practice. (5) The absence of specificity does not preclude clinical utility. The possibility of use as a longitudinal measure of treatment response remains. However, efficacy as a longitudinal clinical measure does require acceptable test-retest reliability. To date, very few test-retest reliability studies have been published with qEEG data obtained from TBI patients or from healthy controls. This is a particular concern because high variability is a known characteristic of the injured central nervous system.

Chronic visual dysfunction after blast-induced mild traumatic brain injury

The purpose of this study was to investigate the long-term visual dysfunction in patients after blast-induced mild traumatic brain injury (mbTBI) using a retrospective case series of 31 patients with mbTBI (>12 mo prior) without eye injuries. Time since mbTBI was 50.5 +/- 19.8 mo. Age at the time of injury was 30.0 +/- 8.3 yr. Mean corrected visual acuity was 20/20. Of the patients, 71% (n = 22) experienced loss of consciousness; 68% (n = 15) of patients in this subgroup were dismounted during the blast injury. Overall, 68% (n = 21) of patients had visual complaints. The most common complaints were photophobia (55%) and difficulty with reading (32%). Of all patients, 25% were diagnosed with convergence insufficiency and 23% had accommodative insufficiency. Patients with more than one mbTBI had a higher rate of visual complaints (87.5%). Asymptomatic patients had a significantly longer time (62.5 +/- 6.2 mo) since the mbTBI than symptomatic patients (42.0 +/- 16.4 mo, p < 0.004). Long-term visual dysfunction after mbTBI is common even years after injury despite excellent distance visual acuity and is more frequent if more than one incidence of mbTBI occurred. We recommend obtaining a careful medical history, evaluation of symptoms, and binocular vision assessment during routine eye examinations in this prepresbyopic patient population.

Traumatic brain injury using mouse models

The use of mouse models in traumatic brain injury (TBI) has several advantages compared to other animal models including low cost of breeding, easy maintenance, and innovative technology to create genetically modified strains. Studies using knockout and transgenic mice demonstrating functional gain or loss of molecules provide insight into basic mechanisms of TBI. Mouse models provide powerful tools to screen for putative therapeutic targets in TBI. This article reviews currently available mouse models that replicate several clinical features of TBI such as closed head injuries (CHI), penetrating head injuries, and a combination of both. CHI may be caused by direct trauma creating cerebral concussion or contusion. Sudden acceleration-deceleration injuries of the head without direct trauma may also cause intracranial injury by the transmission of shock waves to the brain. Recapitulation of temporary cavities that are induced by high-velocity penetrating objects in the mouse brain are difficult to produce, but slow brain penetration injuries in mice are reviewed. Synergistic damaging effects on the brain following systemic complications are also described. Advantages and disadvantages of CHI mouse models induced by weight drop, fluid percussion, and controlled cortical impact injuries are compared. Differences in the anatomy, biomechanics, and behavioral evaluations between mice and humans are discussed. Although the use of mouse models for TBI research is promising, further development of these techniques is warranted.

Patient Characterization Protocols for Psychophysiological Studies of Traumatic Brain Injury and Post-TBI Psychiatric Disorders

Psychophysiological investigations of traumatic brain injury (TBI) are being conducted for several reasons, including the objective of learning more about the underlying physiological mechanisms of the pathological processes that can be initiated by a head injury. Additional goals include the development of objective physiologically based measures that can be used to monitor the response to treatment and to identify minimally symptomatic individuals who are at risk of delayed-onset neuropsychiatric disorders following injury. Research programs studying TBI search for relationships between psychophysiological measures, particularly ERP (event-related potential) component properties (e.g., timing, amplitude, scalp distribution), and a participant's clinical condition. Moreover, the complex relationships between brain injury and psychiatric disorders are receiving increased research attention, and ERP technologies are making contributions to this effort. This review has two objectives supporting such research efforts. The first is to review evidence indicating that TBI is a significant risk factor for post-injury neuropsychiatric disorders. The second objective is to introduce ERP researchers who are not familiar with neuropsychiatric assessment to the instruments that are available for characterizing TBI, post-concussion syndrome, and psychiatric disorders. Specific recommendations within this very large literature are made. We have proceeded on the assumption that, as is typically the case in an ERP laboratory, the investigators are not clinically qualified and that they will not have access to participant medical records.

Performance on the Green Word Memory Test following Operation Enduring Freedom/Operation Iraqi Freedom-era military service: Test failure is related to evaluation context

This study investigates prior reports of high neuropsychological symptom validity test (SVT) failure rates in post-deployed Operation Enduring Freedom/Operation Iraqi Freedom (OEF/OIF) active and veteran military personnel, using a large, multi-site sample (N = 214) drawn from three levels of the Department of Defense/Department of Veterans Affairs (VA) Polytrauma System of Care. The sample failure rate and its relationship to research versus dual research/clinical context of evaluation were examined, in addition to secondary variables explored in prior studies. Results yielded an overall failure rate of 25%, lower than prior reports describing OEF/OIF active-duty and veteran military personnel. Findings also supported the hypothesis that SVT failure rates would differ by context (dual > research). Participants with traumatic brain injury (TBI) failed more frequently than those without TBI in the dual context but not in the research context. Secondary analyses revealed that failure rates increased in the presence of depression, posttraumatic stress disorder, and male sex but were unrelated to active versus veteran military status, service connection (SC) or percentage of SC, age, education, or ethnicity. Further research is required to elucidate the underpinnings of these findings in light of the limited literature and variability between OEF/OIF-related SVT studies, as well as the substantial diagnostic and treatment implications for VA.

A case of frontal neuropsychological and neuroimaging signs following multiple primary-blast exposure

Blast-related traumatic brain injury (TBI) from the Afghanistan and Iraq wars represents a significant medical concern for troops and veterans. To better understand the consequences of primary-blast injury in humans, we present a case of a Marine exposed to multiple primary blasts during his 14-year military career. The neuropsychological profile of this formerly high-functioning veteran suggested primarily executive dysfunction. Diffusion-tensor imaging revealed white-matter pathology in long fiber tracks compared with a composite fractional-anisotropy template derived from a veteran reference control group without TBI. This study supports the existence of primary blast-induced neurotrauma in humans and introduces a neuroimaging technique with potential to discriminate multiple-blast TBI.

Managing traumatic brain injury secondary to explosions

Explosions and bombings are the most common deliberate cause of disasters with large numbers of casualties. Despite this fact, disaster medical response training has traditionally focused on the management of injuries following natural disasters and terrorist attacks with biological, chemical, and nuclear agents. The following article is a clinical primer for physicians regarding traumatic brain injury (TBI) caused by explosions and bombings. The history, physics, and treatment of TBI are outlined.

Biomechanics of single cortical neurons

This study presents experimental results and computational analysis of the large strain dynamic behavior of single neurons in vitro with the objective of formulating a novel quantitative framework for the biomechanics of cortical neurons. Relying on the atomic force microscopy (AFM) technique, novel testing protocols are developed to enable the characterization of neural soma deformability over a range of indentation rates spanning three orders of magnitude, 10, 1, and 0.1 μm s(-1). Modified spherical AFM probes were utilized to compress the cell bodies of neonatal rat cortical neurons in load, unload, reload and relaxation conditions. The cell response showed marked hysteretic features, strong non-linearities, and substantial time/rate dependencies. The rheological data were complemented with geometrical measurements of cell body morphology, i.e. cross-diameter and height estimates. A constitutive model, validated by the present experiments, is proposed to quantify the mechanical behavior of cortical neurons. The model aimed to correlate empirical findings with measurable degrees of (hyper)elastic resilience and viscosity at the cell level. The proposed formulation, predicated upon previous constitutive model developments undertaken at the cortical tissue level, was implemented in a three-dimensional finite element framework. The simulated cell response was calibrated to the experimental measurements under the selected test conditions, providing a novel single cell model that could form the basis for further refinements.

Visual dysfunction following blast-related traumatic brain injury from the battlefield

PRIMARY OBJECTIVE

To assess the occurrence of ocular and visual disorders following blast-related traumatic brain injury (TBI) in Operation Iraqi Freedom.

RESEARCH DESIGN

Retrospective cohort study.

METHODS AND PROCEDURES

A total of 2254 US service members with blast-related combat injuries were identified for analysis from the Expeditionary Medical Encounter Database. Medical record information near the point of injury was used to assess factors associated with the diagnosis of ocular/visual disorder within 12 months after injury, including severity of TBI.

MAIN OUTCOMES AND RESULTS

Of 2254 service members, 837 (37.1%) suffered a blast-related TBI and 1417 (62.9%) had other blast-related injuries. Two-hundred and one (8.9%) were diagnosed with an ocular or visual disorder within 12 months after blast injury. Compared with service members with other injuries, odds of ocular/visual disorder were significantly higher for service members with moderate TBI (odds ratio (OR) = 1.58, 95% confidence interval (CI) = 1.02-2.45) and serious to critical TBI (OR = 14.26, 95% CI = 7.00-29.07).

CONCLUSIONS

Blast-related TBI is strongly associated with visual dysfunction within 1 year after injury and the odds of disorder appears to increase with severity of brain injury. Comprehensive vision examinations following TBI in theatre may be necessary.

Psychological Problems Associated With Operation Enduring Freedom/Operation Iraqi Freedom Deployment

Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF) are the longest sustained ground combat operations involving American forces since the Vietnam era. Our continued involvement in these conflicts has yielded an experienced fighting force; however, to meet the demands of these wars, soldiers are often being asked to complete multiple tours of duty, thus increasing the probability they will experience a combat-related physical injury or experience one or more potentially traumatic events. This article addresses the major psychological issues of concern associated with OEF/OIF deployment and combat. A central aim of this review is to focus on posttraumatic stress disorder, but the authors also address other frequently observed conditions, such as chronic pain, traumatic brain injury, substance abuse, and depression, all of which can have a negative effect on soldiers’ and veterans’ functioning and quality of life. Evidence-based assessment and treatment approaches are reviewed, and relevant resources for health care professionals are identified.

Biomarkers of blast-induced neurotrauma: profiling molecular and cellular mechanisms of blast brain injury

The nature of warfare in the 21st century has led to a significant increase in primary blast or over-pressurization injuries to the whole body and head, which manifest as a complex of neuro-somatic damage, including traumatic brain injury (TBI). Identifying relevant pathogenic pathways in reproducible experimental models of primary blast wave exposure is therefore vital to the development of biomarkers for diagnostics of blast brain injury. Comparative analysis of mechanisms and putative biomarkers of blast brain injury is complicated by a deficiency of experimental studies. In this article, we present an overview of current TBI biomarkers, as well as outline experimental strategies to investigate molecular signatures of blast neurotrauma and to develop a pathway network map for novel biomarker discovery. These biomarkers will be effective for triaging and managing both combat and civilian casualities.

In the line of fire: traumatic brain injury among Iraq War veterans

Soldiers returning home from Iraq are experiencing an increased number of head injuries related to blasts and explosions compared to soldiers of previous conflicts. These injuries are often undetected until the soldiers return home and have difficulty functioning as they did prior to the war. It is therefore important for occupational health nurses to understand blast injury, its pathophysiology, methods for detecting traumatic brain injury, and how these soldiers can be treated.

In the Line of Fire

Soldiers returning home from Iraq are experiencing an increased number of head injuries related to blasts and explosions compared to soldiers of previous conflicts. These injuries are often undetected until the soldiers return home and have difficulty functioning as they did prior to the war. It is therefore important for occupational health nurses to understand blast injury, its pathophysiology, methods for detecting traumatic brain injury, and how these soldiers can be treated.

Blast Injury in a Civilian Trauma Setting is Associated with a Delay in Diagnosis of Traumatic Brain Injury

High-pressure waves (blast) account for the majority of combat injuries and are becoming increasingly common in terrorist attacks. To our knowledge, there are no data evaluating the epidemiology of blast injury in a domestic nonterrorist setting. Data were analyzed retrospectively on patients admitted with any type of blast injury over a 10-year period at a busy urban trauma center. Injuries were classified by etiology of explosion and anatomical location. Eighty-nine cases of blast injury were identified in 57,392 patients (0.2%) treated over the study period. The majority of patients were male (78%) with a mean age of 40 ± 17 years. The mean Injury Severity Score was 13 ± 11 with an admission Trauma and Injury Severity Score of 0.9 ± 0.2 and Revised Trauma Score of 7.5 ± 0.8. The mean intensive care unit and hospital length of stay was 2 ± 7 days and 4.6 ± 10 days, respectively, with an overall mortality rate of 4.5 per cent. Private dwelling explosion [n = 31 (35%)] was the most common etiology followed by industrial pressure blast [n = 20 (22%)], industrial gas explosion [n = 16 (18%)], military training-related explosion [n = 15 (17%)], home explosive device [n = 8 (9%)], and fireworks explosion [n = 1 (1%)]. Maxillofacial injuries were the most common injury (n = 78) followed by upper extremity orthopedic (n = 29), head injury (n = 32), abdominal (n = 30), lower extremity orthopedic (n = 29), and thoracic (n = 19). The majority of patients with head injury [28 of 32 (88%)] presented with a Glasgow Coma Scale score of 15. CT scans on admission were initially positive for brain injury in 14 of 28 patients (50%). Seven patients (25%) who did not have a CT scan on admission had a CT performed later in their hospital course as a result of mental status change and were positive for traumatic brain injury (TBI). Three patients (11%) had a negative admission CT with a subsequently positive CT for TBI over the next 48 hours. The remaining four patients (14%) were diagnosed with skull fractures. All patients (n = 4) with an admission Glasgow Coma Scale score of less than 8 died from diffuse axonal injury. Blast injury is a complicated disease process, which may evolve over time, particularly with TBI. The missed injury rate for TBI in patients with a Glasgow Coma Scale score of 15 was 36 per cent. More studies are needed in the area of blast injury to better understand this disease process.

Provider perspectives on rehabilitation of patients with polytrauma

OBJECTIVES

To describe, from the perspective of U.S. Department of Veterans Affairs (VA) polytrauma rehabilitation providers, (1) patients with combat-related polytrauma and their rehabilitation, (2) polytrauma patient family member involvement in rehabilitation, and (3) the impact on providers of providing polytrauma rehabilitation.

DESIGN

Qualitative study based on rapid assessment process methodology, which included semistructured interviews, observation, and use of a field liaison.

SETTING

The 4 VA polytrauma rehabilitation centers (PRCs).

PARTICIPANTS

Fifty-six purposefully selected PRC providers and providers from consulting services.

INTERVENTIONS

Not applicable.

MAIN OUTCOMES MEASURES

Provider self-report of polytrauma patient characteristics, polytrauma patient family member involvement in rehabilitation, and the impact of polytrauma rehabilitation on providers themselves.

RESULTS

According to PRC providers, polytrauma patients are younger than VA rehabilitation patients. Strong military identities affect rehabilitation needs and reactions to severe injury. The public and the media have particular interest in war-injured patients. Patients with blast-related polytrauma have unique constellations of visible (including amputations, craniectomies, and burns) and invisible (including traumatic brain injury, pain, and posttraumatic stress disorder) injuries. Providers have adjusted treatment strategies and involved services outside of rehabilitation because of this clinical complexity. Family members are intensely involved in rehabilitation and have service needs that may surpass those of families of rehabilitation patients without polytrauma. Sources of provider stress include new responsibilities, media attention, increased oversight, and emotional costs associated with treating severely injured young patients and their families. Providers also described the work as deeply rewarding.

CONCLUSIONS

The VA should prioritize the identification or development and implementation of strategies to address family member needs and to monitor and ensure that PRC providers have access to appropriate resources. Future research should determine whether findings generalize to patients injured in other wars and to people who sustain polytraumatic injuries outside of a war zone, including victims of terrorist attacks.

The Effects of Increasing Stimulus Complexity in Event-Related Potentials and Reaction Time Testing: Clinical Applications in Evaluating Patients with Traumatic Brain Injury

This study compared the effectiveness of P300 event related potentials (ERPs) and reaction time (RT) in discriminating patients with traumatic brain injury (TBI) from healthy control subjects. In particular, we examined how the use of more complex, ecologically relevant stimuli may affect the clinical utility of these tasks. We also evaluated how length of posttraumatic amnesia (PTA) and loss of consciousness (LOC) related to P300 and RT measures in our patient sample. There were 22 subjects (11 patients with TBI and 11 age-matched healthy control subjects). Four stimulus detection procedures were used: two using simple, conventional stimuli (auditory tone discrimination, AT; visual color discrimination, VC), and two using complex, ecologically relevant stimuli in the auditory and visual modalities (auditory word category discrimination, AWC; visual facial affect discrimination, VFA). Our results showed that RT measures were more effective in identifying TBI patients when complex stimuli were used (AWC and VFA). On the other hand, ERP measures were more effective in identifying TBI patients when simple stimuli were used (AT and VC). We also found a remarkably high correlation between duration of PTA and P300 amplitude.

Prognostic value of evoked and event-related potentials in moderate to severe brain injury

Clinicians are often expected to project patients' clinical outcomes to allow effective planning for future care. This can be a challenge in patients with moderate to severe traumatic brain injury (TBI) who are often unable to participate reliably in clinical evaluations. With recent advances in computer instrumentation and signal processing, evoked potentials and event-related potentials show increasing promise as powerful tools for prognosticating the trajectory of recovery and ultimate outcome from the TBI. Short- and middle-latency evoked potentials can now effectively predict coma outcomes in patients with acute TBI. Long-latency event-related potential components hold promise in predicting recovery of higher order cognitive abilities.