Encased by the hard bone of the skull and surrounded by a cushioning fluid, the human brain is protected from everyday jostles and bumps. However, a severe impact to or sudden acceleration of the head can cause injury and disrupt normal brain function. The most common type of traumatic brain injury is a concussion, a temporary alteration in brain function resulting from head trauma. Concussions can range greatly in severity and are commonly a result of sports, motor vehicle accidents, and falls.

It is not known for sure what happens inside the brain when a concussion occurs: imaging techniques, such as computed tomography (CT) scans or magnetic resonance imaging (MRI) typically do not detect structural damage from a concussion. It may be that during concussion, the bundles of nerve fibers that make up the white matter of the brain are damaged, and these cannot be seen by standard imaging techniques.

Because the injury appears to disrupt the brain’s physiology more than its anatomy, diagnosing a concussion can be difficult. Diagnosis relies on the assessment of the signs and symptoms of concussion (such as loss of consciousness, confusion, amnesia, dizziness, and difficulty concentrating)—which can be subtle. Neuropsychological tests help evaluate concussion by testing various aspects of cognitive function such as reaction time, attention span, and working memory.

The assessment and management of concussions are important because of the potential consequences of repeated head injuries. There is evidence that damage from multiple concussions is cumulative and can result in permanent impairment, increased likelihood of additional concussions, longer recovery times, and earlier onset of Alzheimer’s disease. Although most concussions usually resolve within a short time, symptoms may persist for weeks, months, or years after the initial injury: this is known as post-concussion syndrome and may increase the risk of another concussion. Furthermore, a second concussion before complete recovery from the first can be fatal; second-impact syndrome is a rare condition in which the brain loses the ability to regulate its blood supply, causing it to swell dangerously. For athletic coaches who are often faced with the decision whether to let a player return to play after a potential injury, it is better to err on the side of caution rather than risk further injury.

A thorough neuropsychological evaluation is best performed in a quiet room without distractions, which is not always an option, so a number of new tools are being developed to detect concussion. For example, researchers have created a device consisting of a small computer and display system that also block external stimuli, which provides a portable and convenient way to assess injury. Another, goggle-like device featured in the video examines variations in the brain’s timing by measuring how consistently the eye tracks a dot traveling in a circular motion: the greater the variation, the greater the damage. These new devices can provide quick and accurate assessment of concussion, helping prevent potentially dangerous outcomes.

Print Background Essay