Ann-Christine Duhaime

Classification of Traumatic Brain Injury for Targeted Therapies

The heterogeneity of traumatic brain injury (TBI) is considered one of the most significant barriers to finding effective therapeutic interventions. In October, 2007, the National Institute of Neurological Disorders and Stroke, with support from the Brain Injury Association of America, the Defense and Veterans Brain Injury Center, and the National Institute of Disability and Rehabilitation Research, convened a workshop to outline the steps needed to develop a reliable, efficient and valid classification system for TBI that could be used to link specific patterns of brain and neurovascular injury with appropriate therapeutic interventions. Currently, the Glasgow Coma Scale (GCS) is the primary selection criterion for inclusion in most TBI clinical trials. While the GCS is extremely useful in the clinical management and prognosis of TBI, it does not provide specific information about the pathophysiologic mechanisms which are responsible for neurological deficits and targeted by interventions. On the premise that brain injuries with similar pathoanatomic features are likely to share common pathophysiologic mechanisms, participants proposed that a new, multidimensional classification system should be developed for TBI clinical trials. It was agreed that preclinical models were vital in establishing pathophysiologic mechanisms relevant to specific pathoanatomic types of TBI and verifying that a given therapeutic approach improves outcome in these targeted TBI types. In a clinical trial, patients with the targeted pathoanatomic injury type would be selected using an initial diagnostic entry criterion, including their severity of injury. Coexisting brain injury types would be identified and multivariate prognostic modeling used for refinement of inclusion/exclusion criteria and patient stratification. Outcome assessment would utilize endpoints relevant to the targeted injury type. Advantages and disadvantages of currently available diagnostic, monitoring, and assessment tools were discussed. Recommendations were made for enhancing the utility of available or emerging tools in order to facilitate implementation of a pathoanatomic classification approach for clinical trials.

Frequency and Location of Head Impact Exposures in Individual Collegiate Football Players

CONTEXT Measuring head impact exposure is a critical step toward understanding the mechanism and prevention of sport-related mild traumatic brain (concussion) injury, as well as the possible effects of repeated subconcussive impacts. OBJECTIVE To quantify the frequency and location of head impacts that individual players received in 1 season among 3 collegiate teams, between practice and game sessions, and among player positions. DESIGN Cohort study. SETTING Collegiate football field. PATIENTS OR OTHER PARTICIPANTS One hundred eighty-eight players from 3 National Collegiate Athletic Association football teams. INTERVENTION(S) Participants wore football helmets instrumented with an accelerometer-based system during the 2007 fall season. MAIN OUTCOME MEASURE(S) The number of head impacts greater than 10 g and location of the impacts on the players helmet were recorded and analyzed for trends and interactions among teams (A, B, or C), session types, and player positions using Kaplan-Meier survival curves. RESULTS The total number of impacts players received was nonnormally distributed and varied by team, session type, and player position. The maximum number of head impacts for a single player on each team was 1022 (team A), 1412 (team B), and 1444 (team C). The median number of head impacts on each team was 4.8 (team A), 7.5 (team B), and 6.6 (team C) impacts per practice and 12.1 (team A), 14.6 (team B), and 16.3 (team C) impacts per game. Linemen and linebackers had the largest number of impacts per practice and per game. Offensive linemen had a higher percentage of impacts to the front than to the back of the helmet, whereas quarterbacks had a higher percentage to the back than to the front of the helmet. CONCLUSIONS The frequency of head impacts and the location on the helmet where the impacts occur are functions of player position and session type. These data provide a basis for quantifying specific head impact exposure for studies related to understanding the biomechanics and clinical aspects of concussion injury, as well as the possible effects of repeated subconcussive impacts in football.

Long-Term Outcome in Infants with the Shaking-Impact Syndrome

Nonaccidental injury accounts for nearly one quarter of all hospital admissions for head injury in infancy, and is associated with significant morbidity and mortality. Long-term outcome in survivors, however, has been incompletely studied. In this series, 84 infants 2 years of age and younger with the shaking-impact syndrome consecutively admitted to a single hospital between 1978 and 1988 were identified. A questionnaire detailing current medical, developmental, and behavioral status was developed, and attempts were made to locate the 62 children surviving the acute injury. Family instability and strict confidentiality restrictions precluded locating the majority of children, but 14 children with demographic and injury characteristics similar to those of the overall group were contacted at an average of 9 years after injury. Seven children were severely disabled or vegetative, 2 were moderately disabled, and 5 had a good outcome. Of the latter group, 3 had repeated grades and/or required tutoring. Acute factors associated with poor outcome included unresponsiveness on admission, need for intubation, age less than 6 months, and bilateral or unilateral diffuse hypodensity on CT scan. All children with bilateral diffuse hypodensity and loss of gray-white differentiation on CT scan remained blind, retarded, nonverbal, and nonambulatory in spite of aggressive medical and surgical management. This study suggests that the majority of children surviving the shaking-impact syndrome suffer major permanent morbidity, and that acute factors predicting long-term outcome may help guide aggressiveness of care.

Head impact exposure in collegiate football players

In American football, impacts to the helmet and the resulting head accelerations are the primary cause of concussion injury and potentially chronic brain injury. The purpose of this study was to quantify exposures to impacts to the head (frequency, location and magnitude) for individual collegiate football players and to investigate differences in head impact exposure by player position. A total of 314 players were enrolled at three institutions and 286,636 head impacts were recorded over three seasons. The 95th percentile peak linear and rotational acceleration and HITsp (a composite severity measure) were 62.7g, 4378rad/s(2) and 32.6, respectively. These exposure measures as well as the frequency of impacts varied significantly by player position and by helmet impact location. Running backs (RB) and quarter backs (QB) received the greatest magnitude head impacts, while defensive line (DL), offensive line (OL) and line backers (LB) received the most frequent head impacts (more than twice as many than any other position). Impacts to the top of the helmet had the lowest peak rotational acceleration (2387rad/s(2)), but the greatest peak linear acceleration (72.4g), and were the least frequent of all locations (13.7%) among all positions. OL and QB had the highest (49.2%) and the lowest (23.7%) frequency, respectively, of front impacts. QB received the greatest magnitude (70.8g and 5428rad/s(2)) and the most frequent (44% and 38.9%) impacts to the back of the helmet. This study quantified head impact exposure in collegiate football, providing data that is critical to advancing the understanding of the biomechanics of concussive injuries and sub-concussive head impacts.

Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes

Objective: To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes. Methods: This is a prospective cohort study at 3 Division I National Collegiate Athletic Association athletic programs. Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 45 noncontact sport athletes. All athletes were assessed prior to and shortly after the season with a cognitive screening battery (ImPACT) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery. Results: Few cognitive differences were found between the athlete groups at the preseason or postseason assessments. However, a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning (California Verbal Learning Test) compared to the noncontact athletes (24% vs 3.6%; p < 0.006). On 2 postseason cognitive measures (ImPACT Reaction Time and Trails 4/B), poorer performance was significantly associated with higher scores on several head impact exposure metrics. Conclusion: Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes. Further work is needed to assess whether such effects are short term or persistent.

Traumatic brain injury in children.

Head trauma is a common occurrence in childhood, and the spectrum of its consequences is broad. Depending on the severity, type, and location of the injury, outcome may range from complete recovery in children with mild injuries to severe disability in children with more serious injuries. Potential deficits are multiple and include motor, communicative, cognitive, sensory, behavioral, and emotional problems. Optimizing function in those areas is the goal of neurorehabilitation, and this may require medical, therapeutic, and educational interventions. An even more important goal is prevention, and here, too, the pediatrician can play an essential role.

Abusive head trauma.

Child physical abuse that results in injury to the head or brain has been described using many terms, including battered child syndrome, whiplash injuries, shaken infant or shaken impact syndrome, and nonmechanistic terms such as abusive head trauma or nonaccidental trauma. These injuries sustained by child abuse victims are discussed in detail in this article, including information about diagnosis, management and outcomes. The use of forensics, the use imaging studies, and associated injuries are also detailed.

Common data elements in radiologic imaging of traumatic brain injury.

Traumatic brain injury (TBI) has a poorly understood pathology. Patients suffer from a variety of physical and cognitive effects that worsen as the type of trauma worsens. Some noninvasive insights into the pathophysiology of TBI are possible using magnetic resonance imaging (MRI), computed tomography (CT), and many other forms of imaging as well. A recent workshop was convened to evaluate the common data elements (CDEs) that cut across the imaging field and given the charge to review the contributions of the various imaging modalities to TBI and to prepare an overview of the various clinical manifestations of TBI and their interpretation. Technical details regarding state‐of‐the‐art protocols for both MRI and CT are also presented with the hope of guiding current and future research efforts as to what is possible in the field. Stress was also placed on the potential to create a database of CDEs as a means to best record information from a given patient from the reading of the images. J. Magn. Reson. Imaging 2010;32:516–543.

Common data elements in radiologic imaging of traumatic brain injury

Radiologic brain imaging is the most useful means of visualizing and categorizing the location, nature, and degree of damage to the central nervous system sustained by patients with traumatic brain injury (TBI). In addition to determining acute patient management and prognosis, imaging is crucial for the characterization and classification of injuries for natural history studies and clinical trials. This article is the initial result of a workshop convened by multiple national health care agencies in March 2009 to begin to make recommendations for potential data elements dealing with specific radiologic features and definitions needed to characterize injuries, as well as specific techniques and parameters needed to optimize radiologic data acquisition. The neuroimaging work group included professionals with expertise in basic imaging research and physics, clinical neuroradiology, neurosurgery, neurology, physiatry, psychiatry, TBI research, and research database formation. This article outlines the rationale and overview of their specific recommendations. In addition, we review the contributions of various imaging modalities to the understanding of TBI and the general principles needed for database flexibility and evolution over time to accommodate technical advances.

Large Animal Models of Traumatic Injury to the Immature Brain

Large animal models have been used much less frequently than rodent models to study traumatic brain injury. However, large animal models offer distinct advantages in replicating specific mechanisms, morphology and maturational stages relevant to age-dependent injury responses. This paper reviews how each of these features is relevant in matching a model to a particular scientific question and discusses various scaling strategies, advantages and disadvantages of large animal models for studying traumatic brain injury in infants and children. Progress to date and future directions are outlined.