Description Traumatic brain injury or TBI, results from external forces that impact the head, although shock waves from explosions, such as occur in the military, may also result in TBI. Common causes of TBI include head injuries from falls, motor vehicle accidents, sports-related injuries, violence, or, as noted above, explosive blasts. Physically, the head is jolted and there is an acceleration and deceleration following the impact to the head that results in the brain hitting against the skull. This can result in mild, moderate or severe TBI, depending upon the impact to the brain (see below under Classification). There are approximately 2.5 million people who experience a TBI in the United States each year, although this may be an underestimate because many of the more mild cases of TBI, also called concussion, often go unreported because the person is either not seen by a physician or sees a private physician rather than being seen in an emergency room of a hospital. Fortunately, 80% of traumatic brain injuries are mild, with most people recovering within days to weeks. There is, however, a small minority of those who experience a concussion who go on to have what are called post-concussive symptoms, and these symptoms can last for months or even years, and in some cases can lead to an inability to work. Mild TBI is also sometimes questioned in terms of being separate from depression or post-traumatic stress disorder because often there is no radiological evidence using conventional computed axial tomography (CT) scans or conventional magnetic resonance imaging (MRI). The goal today is to use more sophisticated tools to diagnose mild TBI including diffusion tensor imaging, which is sensitive to detecting damage to white matter in the brain, the cables that connect neurons. Diffuse axonal injury, or injury to these white matter cables in the brain, is the most common injury in mild TBI and new techniques are important to evaluate these more subtle changes in the brain that are often missed with more conventional methods of imaging (see Classification below for more information). Classification TBI is classified into mild, moderate, and severe categories although the range may be more continuous than just three categories. The Glascow Comma Scale (GCS) is the most common scale used to classify the severity of TBI into mild, moderate, or severe, and it is based on the level of consciousness, measured from verbal, motor, and eye-opening reactions to stimuli. Mild TBI is classified as having a GCS score between 13 and 15. Here there may be post-traumatic amnesia of less than 1 day, or not, and a loss of consciousness of less than 30 minutes, although there may be no loss of consciousness. Moderate TBI is classified as having a GCS score between 9 and 12. Post-traumatic amnesia may be greater than 1 day but less than 7. Loss of consciousness for more than 30 minutes may also be present although the criterion for this score is loss of consciousness for less than 24 hours. A score of less than 8 is classified as severe TBI with post-traumatic amnesia greater than 7 days and loss of consciousness greater than 24 hours. Often, as noted above, for mild TBI there may be no abnormal findings on CT or MRI scans, although now, with more sophisticated imaging such as diffusion imaging, evidence of diffuse axonal injury, resulting from the stretching or sheering of the white matter in the brain may be observed. In moderate TBI there are findings with CT and MRI including contusions or bruises to the brain and bleeding or hemorrhaging that is sometimes confined to subdural hematoma – blood at the surface of the brain. In severe TBI there may be more serious injuries with contusions, convulsions, seizures, clear fluids draining from the nose or ears, profound confusion, agitation, and slurred speech. Here we will focus more on mTBI as this is the area that work in our laboratory has been primarily focused upon since it is the area most in need of further research in order to diagnose concussion based on radiological evidence and to be able to track the course of illness over time in order to develop prognostic information that will enable us to predict early those who are more likely to recover versus those who are at risk for experiencing further symptoms that either take months or years to recover or where recovery does not happen. Symptoms There are varied symptoms with TBI and not everyone experiences the same symptoms. These symptoms include physical, cognitive, emotional, and behavioral symptoms. For example some of the physical symptoms that are experienced with TBI include headaches, blurred vision, trouble hearing, sensitivity to light, change in taste or smell, a feeling of loss of energy, sleeping too little or too much, and dizziness or a sense of loss of balance, to name just a few. Cognitive symptoms may include problems concentrating, problems with attention and focusing on things, and problems in making decisions that previously had been easy to make. Emotion or mood disturbances include feeling irritable, getting angry with others, feeling sad or anxious, getting easily frustrated, and not feeling oneself. With increasing severity the symptoms may be worse and include confusion or problems speaking (see links included in Helpful Resources). Most of the symptoms become attenuated over time in mild TBI, with most symptoms resolved at 3 months. For a small number of those with mTBI, however, the symptoms do not improve and these individuals continue to suffer. It is here that research will likely be most helpful in developing radiological evidence that can be followed over time in order to understand what subtle brain changes show reparative changes and which may not resolve over time. Heterogeneity of the Disorder Another characteristic of TBI is that it is a heterogeneous disorder, meaning that it is not the same across individuals. This makes sense because the injuries are different, i.e., if you fall and hit the back of your head this is different than hitting the front of the head in a motor vehicle accident. The injuries are located in different places and the force of the impact may be different as well. This adds to what is already a complex disorder in that comparing a group of individuals with mild TBI to healthy controls may not be the best approach to discerning differences in the brain since many of the individuals in the TBI group have very different injuries and symptoms and thus lumping them together to compare them to a group of controls may not be as informative as we would like. Work by Dr. Sylvain Bouix in our laboratory has focused on developing a brain atlas of healthy controls so that individuals with mild TBI can be compared to the atlas in order to determine an individual profile of injury that may be useful to the treating physician, as it will provide a signature of the injury (see Bouix et al., 2013). This is a relatively new approach that has a great deal of potential in detected subtle brain injuries in individuals who suffer from post-concussive symptoms and do not improve over time as most of those who experience a concussion do. Genetics Genetics are also of interest in evaluating TBI, particularly with respect to reparative processes versus those with more progressive disease. There is, for example, some evidence that moderate to severe head injury may lead to a higher susceptibility to Alzheimer’s disease although to-date there is no evidence that a single mild TBI is any more likely to lead to Alzheimer’s disease than would be the case for someone who never experienced a concussion. Attention has been paid, however, to cases of repetitive head trauma that may lead to chronic traumatic encephalopathy (CTE: see “What is Chronic Traumatic Encephalopathy?”). Currently, CTE can only be diagnosed from histology studies of brain tissue from those who are deceased. However, there appears to be a build up of something known as hyperphosphylated tau protein that is also observed in Alzheimer’s patients, although some researchers believe that the there is more tau protein in deep sulci and less amyloid-beta plaques than are observed in Alzheimer’s disease. Why some individuals with repetitive brain trauma from such activities as sports-related concussions from professional football will go on to develop neurodegenerative disease presumed to be CTE and why others do not remains a mystery although having a possible genetic predisposition such as carrying the apolipoprotein E (APO E) gene, which is carried on chromosome 19 and comes in several forms, one of which is APOE4, where having the double allele is a risk factor for Alzheimer’s disease. Forty percent of those with Alzheimer’s disease have this type of allele, and thus it is a risk factor. Having the APOE4 allele may also be associated with why some football players go on to develop neurodegenerative diseases while others do not. More research, however, is needed to make these determinations. Another area of investigation that is promising is to examine an aggregate of tau genes to determine whether or not having a particular genetic profile will lead one to being more susceptible to CTE than others who do not have such a genetic profile. Here research is important as we cannot prevent disease until we can detect, or diagnosis the disease, and understand further some of the risk factors and neurobiological underpinnings that may change over time. Being able to follow the course of brain changes using more advanced imaging technology as well as combining this with information from genetics may help us to determine who is at most risk for potential permanent brain changes versus those who recover following rest. Advanced Imaging As alluded to previously, more advanced imaging techniques today make it possible to detect radiological evidence of brain injury in mild TBI. These techniques are also useful in moderate and severe brain trauma where the main imaging is CT to determine whether or not neurosurgery is needed. The template does not need to be refined in these cases as the major decision is whether to intervene surgically or not. For mild TBI it is more difficult to detect brain alterations and here imaging approaches that include diffusion imaging are needed to discern diffuse axonal injury. It is also important to follow these injuries over time in order to determine whether there are some indicators within the first few hours of injury that predict full recovery versus those in the minority who will experience incomplete or no recovery. Today we have the technology to make such determinations although there is much in the research realm that needs further validation before it reaches the clinic. The translation of research such as using atlases to compare individual profiles of injury are important as using such techniques we can follow the changes in an individual patient over time. This information will also be important for the clinician once these tools are validated. Many imaging centers affiliated with medical schools use diffusion imaging to look for evidence of diffuse axonal injury today and this is most helpful as it leads to more conservative treatments that include more rest and not returning to normal activities right away whereas if there is no evidence of injury from conventional scans a person with mild TBI might be told they are fine for returning to normal activities sooner than they should and this might interfere with full recovery or even set the stage for a secondary impact in a sports-related injury which may be catastrophic if there is not time for the brain to recover from the initial injury. Today and The Future Today there is a great deal of attention on TBI. Newspapers report the injuries of professional football players, hockey players, and soccer players. There are also soldiers returning from Iraq and Afghanistan who have experienced both impact injuries such as motor vehicle accidents as well as being close to an explosive device when it exploded. Children under the age of 4, young people 14 to 25, and those over the age of 70 are at most risk for head injury. Moreover, and particularly with mild TBI, we did not have good radiological evidence of brain injury and this is changing with the first more modern imaging techniques being applied to mild TBI in 2002. The field is thus in its infancy in terms of utilizing sophisticated, advanced imaging technology to detect, to follow the course of brain changes over time, and ultimately to be able to predict those who are at most risk for having a favorable versus a poor outcome so that we can intervene early and move towards full recovery for all of those experiencing a mild TBI. For more severe cases there is also hope as the brain shows far more plasticity than has previously been thought and there is thus hope for assisting those with more severe trauma to compensate by using different networks in the brain as well as perhaps brain exercises in the future that may be helpful in the recovery process. Helpful Resources. Below are several links that may be helpful concerning traumatic brain injury. We encourage you to follow up on the knowledge provided in these links. Traumatic brain injury or TBI, results from external forces that impact the head, although shock waves from explosions, such as occur in the military, may also result in TBI. Common causes of TBI include head injuries from falls, motor vehicle accidents, sports-related injuries, violence, or, as noted above, explosive blasts. Physically, the head is jolted and there is an acceleration and deceleration following the impact to the head that results in the brain hitting against the skull. This can result in mild, moderate or severe TBI, depending upon the impact to the brain (see below under Classification). There are approximately 2.5 million people who experience a TBI in the United States each year, although this may be an underestimate because many of the more mild cases of TBI, also called concussion, often go unreported because the person is either not seen by a physician or sees a private physician rather than being seen in an emergency room of a hospital. Fortunately, 80% of traumatic brain injuries are mild, with most people recovering within days to weeks. There is, however, a small minority of those who experience a concussion who go on to have what are called post-concussive symptoms, and these symptoms can last for months or even years, and in some cases can lead to an inability to work. Mild TBI is also sometimes questioned in terms of being separate from depression or post-traumatic stress disorder because often there is no radiological evidence using conventional computed axial tomography (CT) scans or conventional magnetic resonance imaging (MRI). The goal today is to use more sophisticated imaging tools to diagnose mild TBI using such advanced imaging techniques as diffusion imaging that is sensitive to damage to white matter in the brain, the cables that connect neurons. Diffuse axonal injury, or injury to these white matter cables in the brain, is the most common injury in mild TBI and new techniques are important to evaluate these more subtle changes in the brain that are often missed with more conventional methods of imaging (see Classification below for more information). There are varied symptoms with TBI and not everyone experiences the same symptoms. These symptoms include physical, cognitive, emotional, and behavioral symptoms. For example some of the physical symptoms that are experienced with TBI include headaches, blurred vision, trouble hearing, sensitivity to light, change in taste or smell, a feeling of loss of energy, sleeping too little or too much, and dizziness or a sense of loss of balance, to name just a few. Cognitive symptoms may include problems concentrating, problems with attention and focusing on things, and problems in making decisions that previously had been easy to make. Emotion or mood disturbances include feeling irritable, getting angry with others, feeling sad or anxious, getting easily frustrated, and not feeling oneself. With increasing severity the symptoms may be worse and include confusion or problems speaking (see links included in Helpful Resources). Most of the symptoms become attenuated over time in mild TBI, with most symptoms resolved at 3 months. For a small number of those with mTBI, however, the symptoms do not improve and these individuals continue to suffer. It is here that research will likely be most helpful in developing radiological evidence that can be followed over time in order to understand what subtle brain changes show reparative changes and which may not resolve over time. Another characteristic of TBI is that it is a heterogeneous disorder, meaning that it is not the same across individuals. This makes sense because the injuries are different, i.e., if you fall and hit the back of your head this is different than hitting the front of the head in a motor vehicle accident. The injuries are located in different places and the force of the impact may be different as well. This adds to what is already a complex disorder in that comparing a group of individuals with mild TBI to healthy controls may not be the best approach to discerning differences in the brain since many of the individuals in the TBI group have very different injuries and symptoms and thus lumping them together to compare them to a group of controls may not be as informative as we would like. Work by Dr. Sylvain Bouix in our laboratory has focused on developing a brain atlas of healthy controls so that individuals with mild TBI can be compared to the atlas in order to determine an individual profile of injury that may be useful to the treating physician, as it will provide a signature of the injury (see Bouix et al., 2013). This is a relatively new approach that has a great deal of potential in detected subtle brain injuries in individuals who suffer from post-concussive symptoms and do not improve over time as most of those who experience a concussion do. Genetics are also of interest in evaluating TBI, particularly with respect to reparative processes versus those with more progressive disease. There is, for example, some evidence that moderate to severe head injury may lead to a higher susceptibility to Alzheimer’s disease although to-date there is no evidence that a single mild TBI is any more likely to lead to Alzheimer’s disease than would be the case for someone who never experienced a concussion. Attention has been paid, however, to cases of repetitive head trauma that may lead to chronic traumatic encephalopathy (CTE: see “What is Chronic Traumatic Encephalopathy?”). Currently, CTE can only be diagnosed from histology studies of brain tissue from those who are deceased. However, there appears to be a build up of something known as hyperphosphylated tau protein that is also observed in Alzheimer’s patients, although some researchers believe that the there is more tau protein in deep sulci and less amyloid-beta plaques than are observed in Alzheimer’s disease. Why some individuals with repetitive brain trauma from such activities as sports-related concussions from professional football will go on to develop neurodegenerative disease presumed to be CTE and why others do not remains a mystery although having a possible genetic predisposition such as carrying the apolipoprotein E (APO E) gene, which is carried on chromosome 19 and comes in several forms, one of which is APOE4, where having the double allele is a risk factor for Alzheimer’s disease. Forty percent of those with Alzheimer’s disease have this type of allele, and thus it is a risk factor. Having the APOE4 allele may also be associated with why some football players go on to develop neurodegenerative diseases while others do not. More research, however, is needed to make these determinations. Another area of investigation that is promising is to examine an aggregate of tau genes to determine whether or not having a particular genetic profile will lead one to being more susceptible to CTE than others who do not have such a genetic profile. Here research is important as we cannot prevent disease until we can detect, or diagnosis the disease, and understand further some of the risk factors and neurobiological underpinnings that may change over time. Being able to follow the course of brain changes using more advanced imaging technology as well as combining this with information from genetics may help us to determine who is at most risk for potential permanent brain changes versus those who recover following rest. As alluded to previously, more advanced imaging techniques today make it possible to detect radiological evidence of brain injury in mild TBI. These techniques are also useful in moderate and severe brain trauma where the main imaging is CT to determine whether or not neurosurgery is needed. The template does not need to be refined in these cases as the major decision is whether to intervene surgically or not. For mild TBI it is more difficult to detect brain alterations and here imaging approaches that include diffusion imaging are needed to discern diffuse axonal injury. It is also important to follow these injuries over time in order to determine whether there are some indicators within the first few hours of injury that predict full recovery versus those in the minority who will experience incomplete or no recovery. Today we have the technology to make such determinations although there is much in the research realm that needs further validation before it reaches the clinic. The translation of research such as using atlases to compare individual profiles of injury are important as using such techniques we can follow the changes in an individual patient over time. This information will also be important for the clinician once these tools are validated. Many imaging centers affiliated with medical schools use diffusion imaging to look for evidence of diffuse axonal injury today and this is most helpful as it leads to more conservative treatments that include more rest and not returning to normal activities right away whereas if there is no evidence of injury from conventional scans a person with mild TBI might be told they are fine for returning to normal activities sooner than they should and this might interfere with full recovery or even set the stage for a secondary impact in a sports-related injury which may be catastrophic if there is not time for the brain to recover from the initial injury. Today there is a great deal of attention on TBI. Newspapers report the injuries of professional football players, hockey players, and soccer players. There are also soldiers returning from Iraq and Afghanistan who have experienced both impact injuries such as motor vehicle accidents as well as being close to an explosive device when it exploded. Children under the age of 4, young people 14 to 25, and those over the age of 70 are at most risk for head injury. Moreover, and particularly with mild TBI, we did not have good radiological evidence of brain injury and this is changing with the first more modern imaging techniques being applied to mild TBI in 2002. The field is thus in its infancy in terms of utilizing sophisticated, advanced imaging technology to detect, to follow the course of brain changes over time, and ultimately to be able to predict those who are at most risk for having a favorable versus a poor outcome so that we can intervene early and move towards full recovery for all of those experiencing a mild TBI. For more severe cases there is also hope as the brain shows far more plasticity than has previously been thought and there is thus hope for assisting those with more severe trauma to compensate by using different networks in the brain as well as perhaps brain exercises in the future that may be helpful in the recovery process. Below are several links that may be helpful concerning traumatic brain injury. We encourage you to follow up on the knowledge provided in these links.
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