A football player is slammed hard, laid out cold, and carted off the field; a soldier in Afghanistan is blown off his feet by an explosion; a driver and passengers are pulled from the mangled frame of an automobile—these are the images that come to mind when most people think of traumatic brain injury.
But those dramatic incidents, often involving loss of consciousness, constitute only 10% of traumatic brain injuries. Most blows or jolts to the head that define the condition are mild (80%), shrugged off, and never brought to the attention of a physician. They need not result in permanent damage if the body is given sufficient time to heal.
Unfortunately, “it is becoming more and more apparent that if you have repetitive mild traumatic brain injury, repeated injury without allowing the brain to recover between the injuries, that can trigger a progressive neurodegenerative deterioration. It can result in behavioral and personality changes, memory loss and dementia, that can become worse and worse as the person ages,” said neurologist Ann McKee.
Ann McKee | Photos by Bob Roehr; © AAAS
She had come from the Bedford VA and Alzheimer’s Disease Center at Boston University for a Capitol Hill briefing on traumatic brain injury. The 6 October forum was the third and final event in a series on neuroscience, organized by the AAAS Office of Government Affairs and sponsored by the Dana Foundation.
The U.S. Centers for Disease Control and Prevention (CDC) estimates that 1.7 million Americans a year experience a traumatic brain injury and 52,000 die from that injury, said panel moderator Mark Frankel, director of the AAAS Scientific Responsibility, Human Rights and Law Program. Males are twice as likely as females to be affected by traumatic brain injury, with two peaks of incidence, one in the transition from adolescence to adulthood, which is associated with sports and exposure to risks through active lifestyles, and a second, in old age, associated with falls. The estimated cost in the United States in 2000 was $60 billion.
Acceleration and deceleration is the principle mechanism of injury, McKee told the briefing audience. “The brain is stretching, elongating, and injuring individual nerve cells and support cells inside the brain,” she said. The cumulative effect of smaller jolts to the brain at the microscopic cellular level, if unhealed, can have an equal or greater devastating effect on brain function as we age.
In addition to local injury due to cell damage and hemorrhaging, there also is “disruption of networks throughout the brain because these fiber tracks [of long nerves that connect the brain side to side and front to back] are also disrupted,” said Jordan Grafman. He directs the Traumatic Brain Injury Research Laboratory at the Kessler Foundation Research Center in West Orange, New Jersey.
Diffusion tensor imaging, a special form of MRI, allows researchers to look at fiber tracks and is beginning to serve as a diagnostic tool for traumatic brain injury, he said. This can help to guide surgical and other kinds of interventions for management of acute traumatic brain injury, a field where the military is doing a particularly good job of developing new tools.
Grafman has acquired much of his expertise in the field working with Vietnam veterans who suffered head injuries. He said the greater predictors of recovery “are what you were like before the brain injury, including your cognitive abilities, your genetic predisposition, and your upbringing.”
Veterans are unique in that they all have an induction intelligence test and other standardized evaluations throughout the course of their service. This serves as a good baseline evaluation, but it is seldom available for civilians who are similarly injured.
He also is intrigued by the genetic component of recovery from injury. Having one or another variant of a particular gene “predicts whether you look like a healthy [normal age-match normal control] or whether you are very impaired, compared to a healthy age-matched normal control.”
Grafman worries that insurance companies might someday use this type of genetic information to help direct, or in some instances limit, access to treatment and rehabilitation services.
The Chicago Bears’ hard-hitting all-pro safety Dave Duerson suffered numerous concussions throughout his career. His success on the gridiron was followed by success as a businessman, but life started to change in his 40s. He began to complain of headaches, and this progressed to slurred speech and blurred vision.
He committed suicide earlier this year at the age of 50 by shooting himself in the chest; he intentionally preserved his brain so that it could be donated to the Center for the Study of Traumatic Encephalopathy at Boston University. The center has become a leading repository for the study of sport-related brain injury.
In Duerson’s case, “there were tremendous abnormalities throughout the frontal cortex, which is the part of the brain that controls insight, judgment, and executive function,” McKee explained.
Many of the clinical symptoms of traumatic brain injury are similar to Alzheimer’s and it is difficult to distinguish between the two while the patient is alive. But on autopsy, “pathologically, it is a very distinct condition,” she said. Duerson’s brain had “no deposits of beta amyloid or neuritic plaques, which characterize Alzheimer’s disease.”
The same patterns of brain injury, “only 30 years younger,” were seen when McKee dissected the brain of Owen Thomas, the University of Pennsylvania football player who committed suicide last year at the age of 21.
There is some evidence that the still-developing brain, up to the age of about 25, is more vulnerable to traumatic brain injury than a more mature brain. Younger children have a longer recovery than older juveniles, McKee said. Second-impact syndrome, where a concussion is not recognized and the child continues to participate in a sport, is only seen in young adults. A second, mild concussion causes immediate brain swelling and “is very often fatal,” she said.
Added Grafman: “When a child has a brain injury and their brain is not fully developed and they are tested with age-appropriate tests, sometimes they look pretty good.” But later when that piece of the brain is supposed to further grow or develop, “they begin to show impairments. Often we see delayed effects in children.”
Research across-the-board is hampered by the fact that, in many instances, definitive diagnosis can only be made after death when the brain is sliced into microscopically thin cross-sections, stained, and observed under the microscope.
McKee said there is a need to better understand the basic biologic mechanisms of traumatic brain injury and develop biomarkers of when both injury and healing have occurred. There currently are no good interventions; she believes that rest and recovery are likely to be the best we can provide now, but that better therapeutic strategies are on the foreseeable horizon.
AAAS’s Frankel said there is a tremendous need for increased funding to pursue recent leads from basic and clinical research to address the challenges of traumatic brain injury. But that seems unlikely given the current fiscal climate in Washington, D.C.
The U.S. Department of Defense has funded a significant portion of research in this area. It may be difficult to sustain even that current level of activity given the cuts that the Pentagon is likely to face.
Learn more about the AAAS Office of Government Relations and the Scientific Responsibility, Human Rights and Law Program.
Learn more about the Dana Foundation, which supports brain research through grants and educates the public about brain research.