Doctor Dave Explains Concussions and Head Trauma

Dave Siebert, M.D.@DaveMSiebertFeatured ColumnistOctober 8, 2013

"Football is on trial. Because I believe in the game, I want to do all I can to save it."

Those were the words of President Theodore Roosevelt on Oct. 9, 1905 at a White House meeting in which Roosevelt engineered a number of football changes, such as legalizing the forward pass, in an attempt to make the game safer. That same year, 18 players died of football-related injuries and 159 suffered severe injuries on the field.

The changes worked—relative to the state of medical knowledge at the time—and the game trekked onward into the decades that followed.

As San Diego Chargers wide receiver Malcom Floyd knows all too well, football is an inherently dangerous game.
As San Diego Chargers wide receiver Malcom Floyd knows all too well, football is an inherently dangerous game.Rich Schultz/Getty Images

However, roughly 100 years later, the NFL finds itself at yet another crossroad, as the concussion crisis of the 21st century continues to loom large in pro football.

In order to truly understand what the NFL is up against, one must first possess a thorough understanding of concussions. What exactly are they, and what are the short-term and long-term effects?

Most importantly, can they be prevented?

To answer those questions and more, let's take a closer look at the nature of concussions.

The Biomechanics of Concussions

Scientists used to think that concussions were brain "bruises," but that thinking is now outdated. These days, doctors realize that concussions likely occur as a result of the brain moving within the skull.

Concussions occur when the brain moves within the skull. It elongates, rotates and deforms, but it does not necessarily need to contact the inside of the skull as once thought. Photo from Wikimedia Commons.
Concussions occur when the brain moves within the skull. It elongates, rotates and deforms, but it does not necessarily need to contact the inside of the skull as once thought. Photo from Wikimedia Commons.

Think of a bowl of Jell-O, with the bowl representing the skull and the Jell-O representing the brain. Now, imagine shaking the bowl back and forth.

While such an image is not pretty, it somewhat resembles what happens when a blow to the head abruptly changes the momentum of a player's skull. Whereas the skull quickly stops or changes directions, the brain—floating within a buffer of cerebrospinal fluid (CSF)—continues to move in the original direction.

The brain floats within a small buffer of cerebrospinal fluid (CSF). Photo courtesy of
The brain floats within a small buffer of cerebrospinal fluid (CSF). Photo courtesy of

Ordinarily, CSF absorbs small shifts or changes in brain position without much difficulty. However, the speed and magnitude of helmet-to-helmet hits in the NFL can easily overcome the CSF's cushioning capabilities. As a result, the brain experiences a brief period of linear, angular or rotational movement after impact.

Interestingly, current theory generally holds that rotational and angular movements are more culpable than linear ones.

When those motions take place, the brain undergoes immediate biochemical changes such as:

  • Disruption of the normal activity of neurotransmitters—the molecules that carry signals from neuron to neuron;
  • Decreased blood flow to the brain;
  • An impaired ability of neurons to use glucose as fuel.

Precisely why those changes take place after brain movement remains a bit of a mystery. Numerous theories exist, such as the stretching of neurons or neuronal membrane shearing, but many questions are still unanswered and make up one of the hottest areas of research in sports medicine today.

That said, that body of research is growing quickly.

In 2007, a study by Warren Hardy and his colleagues at Wayne State University suggested that the brain does not need to move much to cause a concussion.

In the study, Hardy subjected cadavers—preserved bodies of those willing to donate themselves for scientific research—to blows to the head similar in magnitude to those that football players may experience during games.

Without getting into too much detail, Hardy found that the cadavers' brains moved an average of less than seven millimeters upon impact.

In other words, it's possible that very small amounts of movement are to blame for the symptoms that result.

Linear Versus Rotational Forces

As mentioned, rotational forces likely play a larger role in concussions when compared to linear ones.

For evidence, let's look at New England Patriots running back Stevan Ridley's concussion from last season's playoffs.

As seen, Ridley sustains a blow to the side of his head, sending him spinning to the ground. His skull stops and changes directions very abruptly, transmitting a large change in angular momentum to his brain.

The above collision sent Stevan Ridley spinning backward and to his right. As a result, his brain experienced a large amount of rotational force.
The above collision sent Stevan Ridley spinning backward and to his right. As a result, his brain experienced a large amount of rotational force.

Conversely, Baltimore Ravens safety Bernard Pollard moves right through Ridley. His head experiences only minimal momentum change to the left, and it continues forward after the collision. Pollard did not suffer a concussion on the play.

Admittedly, innumerable other variables play into why Ridley went down while Pollard did not, but this particular example clearly demonstrates a play where the presence of angular momentum shifts—or lack thereof—likely influenced the outcome of the collision.

That is not to say that significant shifts in linear momentum cannot cause concussions, such as in the classic linear coup-contrecoup injury mechanism seen below.

Image via The Evidence Store
Image via The Evidence Store

Concussion Symptoms

Concussions result in global brain dysfunction. As such, all types of neurological function may suffer.

Immediately after receiving a concussion, most players experience some degree of amnesia. In fact, many will not remember the hit taking place.

Sometimes, players will also forget the events just prior to the injury—called retrograde amnesia—or the minutes and hours that follow, known as anterograde amnesia.

While a hit may also knock a player out altogether, a loss of consciousness does not accompany the vast majority of concussions. However, the condition of profound confusion does. Specifically, a concussed athlete may become disoriented and unable to recall the date, location, his or her name or other basic pieces of information.

Headache, nausea, blurry vision and poor balance are also common in the acute phase.

In the hours and days after a concussion, symptoms of sleep disturbances, changes in mood, trouble concentrating and emotional lability may develop.

Concussion Evaluation

A player does not necessarily require a blow to the head in order to suffer a concussion. A hit to the neck or body that results in sharp movement of the head—similar to whiplash, for instance—can also cause a concussion.

Following a suspicious hit, sideline athletic trainers or doctors will advise a coach to pull the player from the field if he or she has not done so already. Medical personnel will then use any of a number of standardized assessment tools to gauge just what is going on inside a player's head.

According to, the NFL utilizes its own Sideline Concussion Assessment Tool, based on the Standardized Concussion Assessment Tool 2 (SCAT2) published by McCrory and colleagues in the British Journal of Sports Medicine in 2009. A SCAT3, based largely on the same principles, came out in 2013.

Briefly, the SCATs employ standard questions and tests to tease out any neurological deficits that may exist.

One example would be asking an athlete to recite a list of numbers backward to test concentration. Another method involves attempting to recall a list of words to assess memory or using three different balance tests to elicit difficulties with coordination.

The SCATs also ask a player to report any subjective symptoms that he or she may be experiencing, such as a headache. A player's own report of symptoms is the single most important part of making a concussion diagnosis.

Concussion Return-to-Play Protocol

If a player's SCAT scores differ significantly from a baseline test that he took previously, a doctor or trainer may decide to remove him from the game. Comparing the two scores allows for a better—but nowhere near perfect—determination of the effects of a potential concussion-causing hit.

However, a poor SCAT test is not always necessary. Loss of consciousness essentially diagnoses a concussion outright.

An intracranial bleed—seen on this CT as a white spot amongst normal, gray brain tissue—can necessitate emergency surgery. Photo from Wikimedia Commons.
An intracranial bleed—seen on this CT as a white spot amongst normal, gray brain tissue—can necessitate emergency surgery. Photo from Wikimedia Commons.

Furthermore, if any of a number of other neurological tests beyond the scope of this article—pupil reactivity, for example—hint at a bleeding within the brain, emergency medical personnel may need to take the player to a hospital for further evaluation.

Assuming only a simple concussion takes place, generally accepted protocol states that a player must begin a period of complete physical and cognitive rest until symptoms subside.

According to David Barron of the Houston Chronicle, the NFL follows a similar process. Barron notes that after a concussion, players must leave the field:

Any player diagnosed with a concussion must be escorted to the locker room or training room for observation and cannot return to the field under any circumstances under league rules. After the game, it is determined whether he can return home and under what circumstances.

Once symptoms resolve, a concussed player can then begin a series of tests that put the body under steadily increasing amounts of stress, gauging the brain's response to higher physical demands. It is a safe assumption that the NFL follows a sequence similar to the one below:

  1. Complete physical and cognitive rest;
  2. Light activity such as stationary biking;
  3. Heavier activity such as running and cutting;
  4. Non-contact practice;
  5. Full-contact practice.

A player must pass each step without the recurrence of symptoms before returning to play. According to Barron, the player can also complete no more than two phases per day.

If symptoms do return, however, the player must rest and resume the process once symptoms resolve. Some protocols call for the resumption to start at one level lower than where the symptoms recurred.

In addition to physical tasks, doctors use further cognitive testing to determine when an athlete returns to his mental baseline.

Specifically, many NFL teams use the ImPACT test to analyze items such as spatial memory, verbal memory and reaction time.

Once a player can perform maximum physical activity without symptoms, as well as demonstrate the full recovery of his cognitive capacity, he or she can return to the field, as long as the player receives clearance from an independent neurologist.

Why We Care: Second-Impact Syndrome

Not long ago, players returned to the field shortly after losing consciousness in games, dismissing the incident as merely "having their bell rung."

Those days are forever gone.

Emerging evidence continues to show that improper treatment of concussions carries serious, and sometimes even deadly, consequences.

For instance, the dreaded Second-Impact Syndrome (SIS) represents a catastrophic consequence of a poorly managed concussion.

In SIS, an athlete returns to the field too quickly following an undiagnosed or improperly dismissed concussion. He or she then receives a second significant blow to the head and the brain swells.

There is only so much room within the skull, so when the brain swells, it begins to push on the brain stem—the part of the brain responsible for controlling the vital functions of the body, such as the heartbeat.

If the brain stem receives enough pressure, it moves downward into the neck, pressing on and cutting off its own blood supply. Death follows shortly thereafter—potentially within minutes—unless doctors perform emergency brain surgery to relieve the pressure.

Fortunately, as scary as it sounds, SIS is extremely rare—some even debate its true existence. However, the consequences of SIS are so significant that even the mere possibility is frightening enough to warrant careful monitoring and care.

Why We Care: Post-Concussion Syndrome

Long-term effects of concussions also carry significant weight.

Sidney Crosby battled concussion symptoms for over a year.
Sidney Crosby battled concussion symptoms for over a year.Gregory Shamus/Getty Images

Many physicians believe that repeated concussions lower an athlete's "concussion threshold"—the magnitude of a hit needed to produce symptoms. They can also lead to more severe and longer-lasting symptoms with each successive injury.

In the worst-case scenario, post-concussion syndrome (PCS) develops. In PCS, concussion symptoms persist for weeks, months or years.

NHL player Sidney Crosby likely battled his own version of PCS for over a year, and it seems that Buffalo Bills quarterback Kevin Kolb is looking to avoid doing the same.

No standard magic number of concussions exists beyond which PCS syndrome sets in, and each athlete carries his or her own unique profile, as discussed below.

Why We Care: Unclear Long-term Effects and the Rise of Chronic Traumatic Encephalopathy

Although the long-term effects of repeated concussions are still shrouded in relative obscurity, the newly described disease chronic traumatic encephalopathy (CTE) may represent the tip of a very troubling iceberg.

Junior Seau's suicide shocked and devastated the NFL community. Doctors later discovered he suffered from CTE.
Junior Seau's suicide shocked and devastated the NFL community. Doctors later discovered he suffered from CTE.Elsa/Getty Images

Boston University's Center for the Study of Traumatic Encephalopathy describes CTE as "a progressive degenerative disease of the brain found in athletes (and others) with a history of repetitive brain trauma, including symptomatic concussions as well as asymptomatic subconcussive hits to the head."

According to the BU center, symptoms of CTE include "memory loss, confusion, impaired judgment, impulse control problems, aggression, depression, and, eventually, progressive dementia."

As CTE's name suggests, these symptoms could turn permanent and require long-term, chronic treatment.

Nevertheless, evidence definitively connecting concussions to CTE does not yet exist, and the two remain distinct entities for now—though that may one day change.

To explain it another way, researchers can only assume correlation rather than causation at this point. The official statement from the Fourth International Conference on Concussion in Sport elaborates further:

As such, the speculation that repeated concussion or subconcussive impacts cause CTE remains unproven. The extent to which age-related changes, psychiatric or mental health illness, alcohol/drug use or co-existing medical or dementing illnesses contribute to this process is largely unaccounted for in the published literature. At present, the interpretation of causation in the modern CTE case studies should proceed cautiously.

Why We Care: Youth Football Programs

Excellent programs such as USA Football's Heads Up Football campaign are doing what they can to limit the prevalence of concussions throughout youth football programs, as well as to further educate the public about the injury.

Keeping the game as safe as possible for its youngest players is the first step toward preserving the sport as a whole.

All too often, a high school player will wait to report symptoms of a concussion until after the conclusion of a game or even the next day. Many believe it is the responsibility of the educated adult and coach to protect youth players from themselves.

Professional players can also help, as they are role models to young athletes. Messages such as that of Green Bay Packers tight end Jermichael Finley are valuable tools to spread concussion awareness to all levels of athletics.

Future Directions and Research

Relatively, concussion research is still in its infancy, and mountains of data will continue to accumulate over the coming years.

Eventually, patterns may begin to form.

Earlier this year, renowned concussion specialist Dr. Beth Pieroth noted the peculiarity in concussions that seem to treat every player differently.

“Plenty of guys who play football, even professionally, have no injuries or problems,” Pieroth told Rick Kambic of the Lake County News-Sun. “Some people are predisposed to injuries."

Pieroth also hinted at the direction that research may take one day.

"In 10 years, we will be genetically testing kids to see if they are susceptible to certain injuries,” Pieroth said.

It is not difficult to imagine the development of genetic tests aimed at determining an individual athlete's concussion threshold.

Helmet sensors allow researchers to track the force and direction of hits to the head.
Helmet sensors allow researchers to track the force and direction of hits to the head.Mike Ehrmann/Getty Images

Elsewhere, perhaps blood tests—such as the one developed by Drs. Jeffrey Bazarian, Nicola Marchi and Damir Janigro and later described by David Epstein for Sports Illustrated—will shed light on when damage has occurred.

Additionally, helmet impact sensors are continuing to provide information about hit directions and magnitudes to researchers across the country. Potential goals of impact sensors include identifying when a hit is significant, as well as measuring the cumulative amount of force a player experiences during a game.

Bottom Line

Unfortunately, the aforementioned research angles are still in their very early stages.

Whether or not any of those angles will prove instrumental in identifying and treating concussions may also remain unclear for years. As a result, the concussion problem remains as active as it's ever been, and there is no end in sight.

That said, some combination of medical tests, treatment protocols, safety equipment and education—a combination that allows the game to be played safely while still retaining its edge—may still exist. It's up to the football and scientific communities, however, to work together to find it.

After all, Roosevelt and the leaders of college football came up with a satisfactory solution over 100 years ago—at least given the level of knowledge that existed at the time.

A century later, the question begs asking: Why can't we?

Dr. Dave Siebert is a resident physician at the University of Washington with a particular interest in concussions and Primary Care Sports Medicine. He has evaluated concussions on the sideline and in the outpatient, emergency room and training room settings. Find more of his work at the Under the Knife blog.


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