• Concussion is defined as trauma induced alteration in mental status (= not thinking right) that may or may not involve loss of consciousness.
  • 1.6-3.8 million concussions per year occur in the United States.
  • Those who experience a concussion with loss of consciousness are 6 times more likely to have another concussion (compared to controls).
  • Chronic Traumatic Encephalopathy is a condition that occurs in some people who have had repeated concussions. It is not certain how frequent this condition occurs or how many concussions are needed. Patients with this condition are noted to have neurologic decline that is usually noted several  years or even decades after retiring from contact sports. The patients are noted to have decline in their memory, mood, and movements. Some develop a Parkinsons like syndrome. Some go on to develop severe dementia.
  • Neuropsychological testing is considered a very useful tool to assess a patient with concussion.
  • Protocols to have a baseline neuropsychological test (for example, at the beginning of the season) are being developed. If a patient has a concussion, the patient can have another neuropsychological test- and compare it to the baseline test.
  • CT scan of the brain is the most commonly used imaging modality in patients with concussion. Other imaging possibilities: MRI, magnet source imaging, and fMRI.
  • There is data to support that NFL players who have experienced repeated concussions during their careers can develop Chronic Traumatic Encephalopathy (CTE). However, the studies so far do not answer the most critical questions, including how much of a risk do NFL players face for serious memory problems in their retirement- specifically, what are the percentage of players who develop CTE?
  • According to the latest research, there is not a clear relationship between repeatedly heading a soccer ball and having memory problems or other cognitive issues. This issue is still being studied.
  • Players should not return to play after a head injury until all symptoms of the concussion have completely resolved.


Concussion is a hot-topic. Reports on concussion are common in neurology journals, newspaper articles and news programs. Public interest in concussion has been sparked by such controversial issues as: 1) dementia has been noted to develop in retired NFL players who have experienced repeated concussions during their careers; and 2) questions about a possible link between repeatedly heading a soccer ball and memory problems. It should be noted that the frequency of dementia in NFL players is really not known (see below for details—I review the data). Also, the most recent research does not support the concept that heading a soccer ball causes cognitive problems (again- see below- I review the data). These news stories highlight the public’s concerns about head trauma, especially sports related concussions, on cognitive function.

The goal of this article is to describe the short-term and long-term impact of concussion. By summarizing key information on concussion, I hope to underscore how important it is to get expert advice when a patient has head injury- in order to provide the best possible outcome and to avoid potentially devastating long-term sequelae.


photo: xedos4

Concussion is defined as trauma induced alteration in mental status (= not thinking right) that may or may not involve loss of consciousness (Meehan, Pediatrics, 2009).  Sports and bicycle accidents account for the majority of concussions in 5- to 14-year-olds, whereas falls and motor vehicle accidents account for the majority of concussions in adults (Ropper, NEJM, 2007). Concussion is very common. An estimated 1.6-3.8 million sports- and recreation-related concussions occur in the United States each year. This is an estimate- since many concussions are not recognized or reported. In addition, players in collision sports such as American football may experience many hits to the head during the season that are not full concussions, but considered subconcussive impacts (impacts that do not cause symptoms that the player is aware of). For example, a lineman in football may experience 1400 impacts during a season (Stern, PM&R, 2011).

There is often amnesia with the head trauma. Anterograde amnesia (the inability to retain new information) and retrograde amnesia (inability to recall what happened before the head injury) are often seen. The more severe trauma is associated with longer periods of amnesia.

Did you know: Those who experience concussion with loss of consciousness are 6 times more likely to have another concussion, compared to those who have never lost consciousness (Delaney, Clin J Sport Med, 2000). The reason for this is complex- it could be that once an athlete has a concussion, the athlete’s brain may be more susceptible to injury. It could also be that patients who have concussions have more aggressive playing styles- resulting in increased risk for further head trauma.

The clinical course of a patient with a concussion has several possible outcomes.

  • QUICK RECOVERY (< 7-10 days): The overwhelming majority of patients with concussion recover quickly and completely.
  • POSTCONCUSSION SYNDROME: Some patients- weeks or months of headache, dizziness, irritability.
  • SERIOUS NEUROLOGICAL DEFICITS: For example, bleeding in the brain. Uncommon.
  • CHRONIC TRAUMATIC ENCEPHALOPATHY: Develops years or even decades after repeated concussions. Symptoms can include a serious decline in function- memory problems, depression, parkinsons like symptoms (tremor, slow walking) and even dementia. This is uncommon.

Most patients experience quick and complete recovery: After concussion, patients will often have mild symptoms, including headache, cognitive problems (concentration and memory complaints), dizziness, and/or fatigue for approximately 7-10 days. At this point, the overwhelming number of patients with concussion have completely recovered to baseline.

Postconcussion Syndrome: Some patients are noted to have these symptoms persist for several weeks or months. Such patients are diagnosed with Postconcussion Syndrome. The headaches can be described by the patient as very severe and essentially continuous. Concentration is one of the most prominent complaints. A mild degree of dizziness/poor balance is often described. In addition, depression and anxiety are often prominent. The symptoms will vary as to how long they persist. Although not the typical course, some patients can have these symptoms continue for > 1 year.

Serious neurological deficits: Head injury can be associated with serious neurological impairment. Intracranial hemorrhage (= bleeding in the brain) is a serious issue for some patients. Bleeding in the brain can lead to a build-up in pressure in the brain. This can cause the brain to shift. The patient may develop weakness on one side of the body, seizure activity and coma (among other symptoms). This can be a neurosurgical emergency-the surgeon may be called on to immediately open the skull and remove the blood and repair the damaged blood vessels. Because of the potential for serious neurological impairment, patients with significant concussions need a thorough evaluation.

An example of a very worrisome scenario: Person has significant head injury after falling off her bike and hitting her head- she is knocked unconscious for 5 minutes. She recovers, but has mild headache and is mildly unsteady. Two hours after the trauma, she experiences  a steadily increasingly severe headache, difficulty with speech, has right arm and leg weakness. This patient is found to have an epidural hematoma on the left side of her brain (a rapidly expanding mass of blood from a torn blood vessel). This requires emergency neurosurgery to remove the expanding blood and to repair the damage.

Chronic Traumatic Encephalopathy (CTE):

It has been observed that some people who have experienced repeated concussions in their life-time are at risk to develop neurological problems years or even decades after their last head trauma (Gavett, Clin Sports Med, 2011)(Stern, PM&R, 2011). For example, a hockey player who has had many concussions during his career may appear to be quite healthy for several years after he stops playing the sport. He may start to have memory problems developing in his early 50’s. Over the next 10 years, he may slowly decline in his function- developing slow movements and eventual dementia.

The early neurological problems for CTE include problems with memory, multitasking, organization, depression, and impulse control. The patient may have trouble taking care of their finances. Impulse control problems can lead to severe anger outbursts or illicit drug use. Depression is common. Some patients commit suicide. Late symptoms include worsening in memory function, language impairment and movement problems (similar to Parkinson’s Disease). Patients may develop dementia. Their walking may be stooped with a slow shuffling gait. The patient may be very slow to answer questions. The symptoms of CTE are usually slowly progressive over many years. Ultimately, the patient can be very limited with movements and can have severe dementia.

The link between repeated concussions and later neurological problems has been known for many years. In 1928, a group of boxers were noted to have a condition that included mental confusion and clumsy movements (Martland, JAMA, 1928). The symptoms appeared to be related to the repeated blows to the head the boxers had experienced in their careers. The term used to describe this constellation of symptoms was “punch drunk.”Over the years, more groups of boxers were described with this symptom spectrum. With further research, it was determined that activities other than boxing could produce the symptoms- this lead to the term CTE. Activities that have been associated with CTE include American football, soccer, wrestling and hockey, to name a few. In addition, victims of child abuse and patients with epilepsy have been described with CTE.

A consistent finding of CTE is a history of repeated head trauma. It has not yet been determined how many concussions or the severity of the concussions that are necessary to result in CTE. For example, it is not clear whether a few severe concussions are the most likely predisposing factor to develop CTE or whether a long history of many less severe blows to the head (such as experienced by a linemen in football) would lead to CTE. Also, it should be stressed, not all people who have repeated concussion develop CTE. It is possible that underlying genetic predisposition may lead to a higher likelihood for developing CTE. This is an important area of research!

The mechanism for developing CTE is not well understood. It has been hypothesized that stretching of neurons in the brain could lead to a cascade of events that ultimately leads to neuronal death. Pathology examination reveals that large regions of brain are shrunken- due to neurons shrinking or dying off. Microscopic examination reveals clumps of abnormal protein in various regions of the brain. These clumps of abnormal protein are called tau and are deposited in the brain in the form of neurofibrillary tangles, neuropil neurites and glial tangles. The abnormalities are prominent in the temporal lobes—which explains the problems with memory; and the frontal lobes- which explains the problems with organization and disinhibited behavior (Gavett, Clin Sports Med, 2011).

CTE is an important area of research. A better understanding of the following would be incredibly helpful: 1) what types of head trauma lead to CTE; 2) who is most likely to develop CTE; 3) how do we prevent the development of CTE in at risk people. Given that millions of athletes take part in contact sports and that large numbers of military personnel experience concussions, CTE represents an important public health issue (Stern, PM&R, 2011).


photo: nattavut

Patients who have a concussion may experience cognitive impairment. Neuropsychological testing can be a very valuable tool to measure these impairments. Neuropsychological testing in patients with a recent concussion reveals cognitive deficits in the following areas (Putukian, PM&R, 2011):

  • Memory
  • Learning
  • Attention
  • Ability to process information
  • Reaction time
  • Problem solving

Neuropsychological testing can be administered and interpreted by a trained neuropsychologist. Comprehensive testing is very thorough- it can involve 6-8 hours of testing. Tests of memory (verbal and visual memory), problem solving, and attention are administered. Shorter examinations, including computerized testing, are alternatives. Currently, the optimal testing procedures are being studied.

A very interesting idea is to obtain baseline testing, especially in high risk individuals such as athletes in contact sports. A certain percentage of these athletes will have a concussion. Comparing the cognitive testing before the concussion (baseline test) to the testing after the concussion is an excellent way to determine what cognitive impairment is new.

For example, all players on a team could have neuropsychological testing at the beginning of the season- this is the baseline test. Then, any player who had a concussion would have undergo a repeat neuropsychological exam. The baseline test and the post – trauma test could then be compared. This would, of course, provide very good information on what problems in cognition were the results of the head trauma.

The above procedure (baseline testing at beginning of season/comparison testing if head trauma) has been done on sports teams already—and good information has been provided (Erlanger, J Athl Train, 2001). Currently, leaders in the field are discussing the optimal testing strategy. The concerns about the cognitive problems caused by concussion make optimal neuropsychological testing a high priority!


Not all patients with concussion undergo brain imaging. Patients with mild head trauma with rapid recovery may simply be observed. More severe trauma, especially with longer periods of loss of consciousness or in patients with neurological deficits (such as weakness on one side of the body, for example) may need a brain scan. The clinician evaluating the patient will make the decision. The following are some of the options for brain imaging:

  • CT scan: CT scans are the most commonly used brain imaging procedure after concussion. CT provides a picture of the brain’s structure. CT scans are readily available to most emergency rooms. The scans can be done quickly- which is useful in a patient who is in significant pain. CT will identify the most critical abnormalities, including bone fractures and bleeding problems. Blood expanding in the brain is one of the most important reasons to do a brain scan after concussion. Expanding blood can be lethal if it is not surgically corrected.
  • MRI: Provides a picture of the brain’s structure. The picture provided by MRI is superior to CT. Thus, MRI is used to identify more subtle brain lesions not identified with CT. MRI takes much longer than a CT to perform—that is one of the main reasons that CT is performed more often than MRI in the emergency room setting. MRIs are sometimes obtained on patients who are having cognitive problems for several days or weeks after the concussion.
  • Magnet Source Imaging: This is a procedure which measures the brain’s electrical activity. Neurons in the brain produce electricity as part of their normal function. The scan will light-up when the area of the brain responsible for a function is in use. For example, if a patient is thinking of a word, the area of the brain for language will light-up. Pretty interesting! Subtle electrical abnormalities can be identified with Magnetic Source Imaging. It has been suggested that this procedure can help study: 1) the brain’s injury after concussion; and 2) to study the recovery of neuronal functional. Magnetic source imaging is currently being studied for its potential usefulness after concussion.
  • Functional MRI: This is a procedure that provides information about the function of the brain. Similar to magnet source imaging, the functional mri scan will light-up when the area of the brain responsible for a given function is in use. Functional MRI measures blood flow. Similar to magnetic source imaging, this procedure is being studied for its potential usefulness after concussion.


photo: freedigitalphotos

Studies on NFL players have raised concerns that repeated head trauma can lead to memory problems and even dementia (with some similarities to Alzheimer’s Disease), after the players have retired. It has been demonstrated that some players do develop dementia—see above discussion on Chronic Traumatic Encephalopathy (CTE). However, the percentage of NFL players that develop the memory problems/dementia is not clear.

Some information is provided by the “NFL’s brain bank.” This is also known as the Boston University Center for the Study of Traumatic Encephalopathy (BU CSTE). This brain bank is located at the Bedford VA Medical Center. This is the largest “brain bank” for CTE. This center has recently reported that 14 out of 15 NFL players that have so far been studied have been diagnosed with CTE.

14 out of 15- this sounds like an incredibly high number! Does this mean that 93% of NFL players are doomed to develop CTE? The answer is NO! Remember, these 15 brains had to be donated by the deceased player’s family for study at autopsy. This leads to a very important selection bias: families are much more likely to donate their loved one’s body to autopsy if they are concerned about CTE. Thus, there is likely an overrepresentation of CTE in “NFL’s brain bank.” Regardless, it does illustrate how repeated head trauma can produce serious and devastating long-term cognitive problems. It is extremely important to determine an accurate estimation of the frequency of CTE in athletes. This research is hopefully going to be accomplished- since there are so many important questions that need to be answered.

The 14th NFL player (from above study) to be diagnosed with CTE was Dave Duerson. Dave Duerson played safety for 11 seasons with the Chicago Bears, NY Giants and Phoenix Cardinals. He committed suicide at age 50 years. Prior to his death, he noted problems with his memory, spelling, vision and emotional control. He expressed concerns to family and friends that he may have CTE. He left a suicide note that read: “Please, see that my brain is given to the NFL’s Brain Bank.” He committed suicide by shooting himself in the chest, presumably to preserve his brain for neuropathological examination (BU CSTE website).

In addition to the data from the brain bank, there has been other data suggesting that NFL players are at increased risk for cognitive problems after they have retired. For example, one study reported the results of a general health questionnaire completed by 2552 retired professional football players (Guskiewicz KM, Neurosurgery, 2005). A second questionnaire focusing on memory related questions was completed by 758 players. The study found that retired players with 3 or more concussions during their careers had a higher incidence (fivefold increase) of significant memory problems, compared to players without a history of concussion. The authors concluded that repeated concussions during a players’ career could have serious consequences on the player’s cognitive function later in life. It should be noted that this study has been criticized for methodological problems (Casson, Neurology Today, 2010).

In summary, there is data to support that NFL players who have experienced repeated concussions during their careers can develop CTE. However, the studies so far do not answer the most critical questions, including how much of a risk do NFL players face for serious memory problems in their retirement- specifically, what are the percentage of players who develop CTE? Well designed, long-term, prospective studies with large numbers of players are needed to answer the most critical questions. We are not there yet, but studies are being undertaken/designed to answer these questions.


photo: master isolated ima

The possibility that heading a soccer ball repeatedly may result in memory and other cognitive problems has been the focus of much intense media attention. This is understandable- can you imagine if simply heading a soccer ball over and over resulted in children and young adults not reaching their potential! This would be a serious problem, especially given the huge numbers of athletes heading the soccer ball across the entire world. The concerns about heading a soccer ball were raised in part after the death of Jeffrey Astle, a legendary soccer player known for his heading of the ball. He died at age 59 after several years of dementia (Spiotta A, Neurosurgery, 2012). He was found to have Chronic Traumatic Encephalopathy (CTE, see above for description).

In addition, during the 1980’s and 1990’s, multiple studies had reported a link between heading a soccer ball and cognitive problems. These studies, it should be noted, have been criticized for methodological limitations. They were also carried out at a time when the soccer ball was heavier—leather balls were used that would get very heavy, especially when wet. A major problem with these earlier studies was that there were limitations on clarifying which patients had full concussions. Consider how that would complicate these studies—if significant concussions are not controlled for, then how can you assess the milder effects of heading a soccer ball?

More recent studies have examined whether heading a soccer ball results in neurocognitive problems. These studies have not shown an association between heading a soccer ball and memory or other cognitive problems (Spiotta A, Neurosurgery, 2012).

Thus, at this time, there is not a clear relationship between repeatedly heading a soccer ball and having memory problems or other cognitive issues. This issue is still being studied. It is thought that good heading technique is important to reduce head injuries. Also, reducing player-to-player head contact and player-to-goal post collisions would also be important- it is these types of crashes that cause the symptomatic concussions—and severe concussions certainly can adversely impact cognition.



A big decision occurs every day in the world of sports- when a player has a concussion, when can they return to the game? A generally accepted management principle is that players should not return to play until all symptoms of the concussion have completely resolved (Meehan, Pediatrics, 2009). For most players, the dizziness, concentration problems and memory difficulties that were caused by the concussion will resolve in less than 7-10 days. For some players, longer periods of time will be required. In order to determine if a patient is recovered, a careful history and exam is needed. Also, neuropsychological testing can be performed. Ideally, the patient would have baseline neuropsychological data for comparison-before the concussion (for example, a baseline neuropsychological test obtained at the beginning of the season). It has been suggested that the patient not return to play until the neuropsychological testing is equal to baseline scores.

There is a condition known as “second impact syndrome.” This tragic condition was described in a 19 year-old college football player who returned to the game after a concussion, despite still having symptoms (Saunders, JAMA, 1984). He experienced some minor trauma during the remainder of the game, but not unusual contact. He walked off the field, collapsed and died. His brain had massive swelling. Although second impact syndrome is rare and controversial (some experts question if it is a real phenomena), the message is clear to most experts—conservative management of concussion is likely a good idea.

The days of having a significant concussion and then returning to the game with symptoms—for example feeling unsteady on the feet and having trouble thinking- are hopefully over. It used to be considered a sign of courage to return to the game with symptoms of a head injury. Now, such actions are strongly discouraged.


photo: salvatore vuono

Concussion is a common and important issue. Fortunately, most patients recover fully after a concussion. Some patients may not have full recovery, especially after relatively severe head trauma. Cognitive problems after concussion include headaches, concentration issues, memory problems and impaired mood (depression and irritability). Patients should not return to play until they have fully recovered from a concussion. Coaches, schools, players and families are becoming much more aware of the seriousness of head injury. Repeated concussion in sports such as boxing, football and hockey, can result in Chronic Traumatic Encephalopathy (CTE)- this usually develops several years after retiring from contact sports. CTE results in a decline in neurologic function that can be severe.

There are many important questions to be answered about concussion. For example: 1) What are the best ways to prevent concussion? 2) Are there people who are predisposed to get concussions? 3) What testing is most appropriate- before and after concussion?  4) What kind of trauma results in CTE? Research to answer these important questions is ongoing.


BU CSTE website

Casson IR. Do the facts really support an association between NFL players’ concussions, dementia and depression. Neurology Today 2010.

Delaney JS, Lacroix VJ, Leclerc S, Johnston KM. Concussions during the 1997 Canadian Football League season. Clin J Sport Med 2000;10:9-14.

Gavett BE, Stern RA, Mckee AC. Chronic traumatic encephalopathy: a potential late effect of sport-related concussive and subconcussive head trauma. Clin Sports Med 2011;30:1-10.

Martland HS. Punch drunk. JAMA 1928;91:1103-1107.

Meehand W, Bachur RG. Sport-related concussion. Pediatrics 2009;123:114-123.

Putukian M. Neuropsychological testing as it relates to recovery from sports-related concussion. PM&R 2011;3:S425-S432.

Ropper AH, Gorson KC. Concussion. N Engl J Med 2007;356:166-72.

Spiotta AM, Bartsch AJ, Benzel EC. Heading in soccer:dangerous play? Neurosurgery 2012;70:1-11.

Stern R, Riley DO, Daneshvar DH, et al. Long-term consequences of repetitive brain trauma: chronic traumatic encephalopathy. PM&R 2011;3:S460-S467.

Xedos4 (Sport photo)

Nattavut’s (Numbers in brain photo)

Football helmet photo

Master isolated image (figure and soccer ball)

Naypong (whistle and ball photo)

Salvatore Vuono (skier sign photo)