No effect of mild nonconcussive injury on neurocognitive functioning in U.S. Army soldiers deployed to Iraq.

UNLABELLED: With neurocognitive testing being heavily relied on for concussion assessments in the U.S. Warfighter, there is a need to investigate the impact of nonconcussive injury on neurocognitive functioning. OBJECTIVES: To determine if a nonconcussive injury may have a negative effect on neurocognitive functioning in a deployment setting. METHODS: The current study compared scores on computerized and traditional neurocognitive tests of 166 Soldiers deployed to Iraq. Performance on a battery of tests was compared between a group of healthy deployed Soldiers (n = 102) versus a group of deployed Soldiers seeking outpatient care for mild injuries not involving the head or blast exposure (n = 62). RESULTS: The injured group's performance was not significantly lower on any of the measures administered compared to healthy Soldiers. CONCLUSIONS: The results suggest that there was no significant effect of nonconcussive injury on neurocognitive functioning. Findings lend support to feasibility of using neurocognitive tests to evaluate the effects of concussion in theater.

The ANAM lacks utility as a diagnostic or screening tool for concussion more than 10 days following injury.

Congress has mandated that the Department of Defense perform screening for concussion, or mild traumatic brain injury, on all service members redeploying from Iraq and Afghanistan. However, the retrospective diagnosis of concussion is complicated by the subjective nature of the complaints, overlap of symptoms with other conditions, and the normally rapid recovery of neurocognitive function following a concussive event. One diagnostic and screening test in current use by the Department of Defense is the Automated Neuropsychological Assessment Metrics (ANAM). A team of researchers deployed to Iraq between January and April 2009 to test the validity of the ANAM for the diagnosis of concussion in the combat environment. Performance by concussed participants on all six ANAM subtests was compared with that of controls. The ANAM appears to have no utility as an individual diagnostic or population screening tool for the detection of neurocognitive dysfunction from a single, uncomplicated concussion when administered 10 or more days following injury. Further studies are required to determine the modalities providing optimal sensitivity and specificity for use as diagnostic or screening tests beyond the first 72-hour acute postinjury period.

Evaluation of the Military Acute Concussion Evaluation for use in combat operations more than 12 hours after injury.

The diagnosis and management of concussion can be difficult in a combat environment, especially in the absence of loss of consciousness or post-traumatic amnesia. As no validated test exists to diagnose or grade neurocognitive impairment from a concussion, the military currently employs the Military Acute Concussion Evaluation (MACE) in Iraq. This is a two-part test, which incorporates the standardized assessment of concussion (SAC) as its objective score, although it has not been shown to be valid unless administered shortly after injury. A research team deployed to Iraq between January and April 2009 to examine the validity of several tests of neurocognitive function following a concussion, including the MACE. When administered more than 12 hours after the concussive injury, the MACE lacked sufficient sensitivity and specificity to be clinically useful.

Repeated Low-Level Blast Exposure: A Descriptive Human Subjects Study.

The relationship between repeated exposure to blast overpressure and neurological function was examined in the context of breacher training at the U.S. Marine Corps Weapons Training Battalion Dynamic Entry School. During this training, Students are taught to apply explosive charges to achieve rapid ingress into secured buildings. For this study, both Students and Instructors participated in neurobehavioral testing, blood toxin screening, vestibular/auditory testing, and neuroimaging. Volunteers wore instrumentation during training to allow correlation of human response measurements and blast overpressure exposure. The key findings of this study were from high-memory demand tasks and were limited to the Instructors. Specific tests showing blast-related mean differences were California Verbal Learning Test II, Automated Neuropsychological Assessment Metrics subtests (Match-to-Sample, Code Substitution Delayed), and Delayed Matching-to-Sample 10-second delay condition. Importantly, apparent deficits were paralleled with functional magnetic resonance imaging using the n-back task. The findings of this study are suggestive, but not conclusive, owing to small sample size and effect. The observed changes yield descriptive evidence for potential neurological alterations in the subset of individuals with occupational history of repetitive blast exposure. This is the first study to integrate subject instrumentation for measurement of individual blast pressure exposure, neurocognitive testing, and neuroimaging.

No Significant Acute and Subacute Differences between Blast and Blunt Concussions across Multiple Neurocognitive Measures and Symptoms in Deployed Soldiers.

Seventy-one deployed U.S. Army soldiers who presented for concussion care due to either blast or blunt mechanisms within 72 h of injury were assessed using the Military Acute Concussion Evaluation, the Automated Neuropsychological Assessment Metrics (ANAM), traditional neuropsychological tests, and health status questionnaires. Follow-up ANAM testing was performed 10 d after initial testing (±5 d). Twenty-one soldiers were excluded: two for poor effort and 19 who had combined blast/blunt injuries. Of the remaining 50 male participants, 34 had blast injuries and 16 had blunt injuries. There were no statistically significant differences between blast injury and blunt injury participants in demographic, physical, or psychological health factors, concussive symptoms, or automated and traditional neurocognitive testing scores within 72 h post-injury. In addition, follow-up ANAM scores up to 15 d post-injury were not significantly different (available on 21 blast-injured and 13 blunt-injured subjects). Pre-injury baseline ANAM scores were compared where available, and revealed no statistically significant differences between 22 blast injury and eight blunt injury participants. These findings suggest there are no significant differences between mechanisms of injury during both the acute and subacute periods in neurobehavioral concussion sequelae while deployed in a combat environment. The current study supports the use of sports/mechanical concussion models for early concussion management in the deployed setting and exploration of variability in potential long-term outcomes.

No Effect of Deployment Environment in Establishing Baseline Neurocognitive Scores in U.S. Army Soldiers.

With heavy reliance on neurocognitive testing for concussion status assessments in the U.S. warfighter, there is a need to investigate the impact of testing environment on neurocognitive functioning. The current study compared scores on computerized neurocognitive tests of 166 soldiers who were deployed to Iraq. Predeployment baseline scores (n = 53) were compared to baseline scores collected while deployed (n = 113) on the battery of tests. There was no significant difference between baseline scores acquired from the predeployment group versus the deployed group. Furthermore, only one subtest revealed a significant difference in change scores from the follow-up test session when comparing the location of initial baseline testing. The results suggest that testing environment does not significantly influence baseline neurocognitive testing. The findings also provide support for the use of neurocognitive testing in a deployment environment.

Assessment of acute concussion in the combat environment.

Despite the prevalence of concussion in soldiers deployed to Iraq and Afghanistan, neuropsychological tests used to assist in concussion management have not been validated on the battlefield. This study evaluated the validity of the Automated Neuropsychological Assessment Metrics (ANAM) in the combat environment. Cases meeting criteria for concussion, healthy controls, and injured controls were assessed. Soldiers were administered the ANAM, traditional neuropsychological tests, and a background questionnaire. Cases were enrolled within 72 h of concussion. Cases exhibited poorer performance than controls on all ANAM subtests, with significant differences on simple reaction time (SRT), procedural reaction time (PRT), code substitution, and matching to sample (p<.001). Discriminant ability of scores on SRT and PRT subtests was 71%, which improved to 76% when pre-deployment baseline scores were available. An exploratory clinical decision tool incorporating ANAM scores and symptoms improved discriminant ability to 81%. Results provide initial validation of the ANAM for detecting acute effects of battlefield concussion.

Personality Assessment Inventory profiles of deployed combat troops: an empirical investigation of normative performance.

The present study examined the normative scores and psychometric properties of the Personality Assessment Inventory (PAI; Morey, 1991) within a non-treatment-seeking sample of soldiers deployed to combat zones in Iraq, compared with a sample of community adults matched with respect to age and gender. Results indicate the scores and properties of the PAI scales were generally quite similar in the Iraq and community samples, with modest differences emerging on only 3 subscales addressing antisocial behavior, issues with close relationships, and interpersonal vigilance. These results suggest that standard normative interpretation of PAI scales is appropriate even when the instrument is administered in a combat zone. In comparison with prior research, the results may suggest that documented mental health issues among combat veterans, when present, may be particularly likely to emerge postdeployment.