"He was never quite 'himself' after that accident": exploring the long-term consequences of mild traumatic brain injury.

Patients seek medical care after traumatic brain injury (TBI) roughly 2 million times per year in the United States. Eighty percent of these injuries can be classified as ''mild''. The real incidence of TBI is, however, unknown, because victims of mild TBI often do not see a physician. Having your ''bell rung'' or ''seeing stars'' is an experience that a high percentage of us could talk about from personal experience. During athletics, these are injuries that fall into the ''shake it off'' category. In this issue, Hofman et al (page 441) report their study of victims of mild TBI, which used MR imaging , single-photon emmission CT (SPECT), and formal neurocognitive testing. Seventy-seven percent of these patients had abnormalities seen on MR or SPECT studies or both. The question is: can you ''shake off'' such abnormalities manifested by brain imaging and physiological changes? One would think that we should know the answer to this question, but there is little science to support an adequate response. What we do know about the clinical consequences of mild TBI is that a poorly defined subset of patients will have persistent symptoms that often are referred to as the ''postconcussive syndrome''. In some cases, headaches , difficulties with memory or concentration, and behavioral changes can be quite debilitating. We also know that for people who carry the apo-lipoprotein-e4 allele, mild TBI is a risk factor for the development of Alzheimer disease (1). What are the implications of this when we learn that every high school football team in America averages almost two mild TBIs per season (2)? The annual national estimate of mild TBI among 10 high school sports (boys' sports: baseball, basketball, football, soccer, wrestling; girls' sports: basketball, field hockey, softball, soccer, volleyball) is 66,816 cases (2). One difficulty with studying these patients is that they tend to ''fall through the cracks'' in clinical science. Head-injured patients are often cared for by neurosurgeons, because an early risk to these patients is the development of a delayed hematoma. Consequently, most studies of clinical management are focused on more severe TBI. Patients with mild TBI and few outward signs of injury often have difficulty finding an experienced physician interested in treating them after the risk of developing a delayed hematoma has passed. Therefore, those researchers who have an interest in mild TBI come from a wide range of backgrounds including psychiatry , rehabilitation medicine, neurology, …