How Concussions Work

Concussions are a form of damage to the brain, the result of an impact with the inside of the skull.

In the waning years of American vaudeville, a comedy act -- later to be known as "The Three Stooges" -- entered the public's eye. Their slapstick routines regularly consisted of situations often leading to one or more of them being hit, jarred or rattled in the head, and their work was wildly popular.

While admittedly amusing in some fictional contexts, a concussion -- derived from the Latin word concutere, meaning "to shake violently" -- is never a laughing matter in real life. Imagine someone driving without a seatbelt into a concrete wall. When the vehicle suddenly stops, the driver keeps going, and that's what happens to the brain during a concussion. To put it simply: A concussion occurs when the skull stops and the brain keeps moving, resulting in a collision. In an ironic twist, the one bone structure specifically designed to shield our grey matter from injury ends up doing most of the damage [Source: Lew].


Nearly all cases of head trauma fall under the umbrella of what we call "mild traumatic brain injury" (MTBI), an expression that can be used interchangeably with "concussion." Concussions are among the lesser-understood injuries today, and their treatment still continues to evolve. Medical practitioners frequently disagree on how to diagnose and manage concussions of varying grades, or levels of severity. However, some aspects of these injuries aren't up for debate. Evidence has shown that their effects can be permanently debilitative in severe cases [Source: Lew].

Worst-case concussions can even result in death. And while there's a tendency to only associate these injuries with athletics, most cases in the United States are entirely unrelated to sports. So, it's important to understand concussions to facilitate preparedness in the event that you or someone close to you has one. Some of the details provided in this article cover the common causes, symptoms, treatment and prevention methods for mitigating their effects.

Keep reading to learn about some of the immediate and long-term concussion symptoms.


Symptoms of Concussion

How Concussions Work illustration

A concussion is a mild form of closed head trauma, so an injury that results in a skull fracture or subdural hematoma (bleeding between the brain and skull) can't be accurately described as a concussion. In other words, if bleeding is present in a computer topographic (CT) scan, then another type of brain injury is present [source: Cuhna]. Most mild brain injuries can't be detected by magnetic resonance imaging (MRI) or a computer topographic CT scan [sources: CINN, Yamamoto]. Even so, such procedures are often used to detect possible severe brain damage in patients who have experienced head trauma.

In addition to lasting cognitive and emotional effects, concussion victims typically exhibit several immediate signs and symptoms that can help you diagnose such an injury.


A few common characteristics of concussions include nausea, loss of coordination or balance, confusion, delayed reaction time, slurred speech and memory loss. Although it isn't necessarily required for diagnosis, loss of consciousness is among the most common signs that a concussion has occurred. However, some alteration of consciousness must take place in order to accurately classify an injury as a concussion [Source: Lew].

People commonly keep small alterations of consciousness to themselves, which can contribute to the underreporting of concussions. However, there are a few outward signs that a person typically displays after experiencing one. Among these symptoms are vacant facial expressions, delayed reaction times, loss of focus or inability to pay attention. Therefore, even if a victim adamantly denies having experienced a subtle change in consciousness, there are certain telltale signs that allow an experienced observer to detect when a concussion has occurred [source: Lew]. Later, we'll go into detail about the various tests you can administer someone that you suspect may have recently had a concussion.

Other common symptoms include headache, dizziness and visual disturbances. Examples of the kind of vision problems that concussions might cause include photophobia -- a strong aversion to bright lights -- as well as seeing stars or having double vision.

Auditory disturbance is another symptom of concussion. A victim may experience phonophobia -- an aversion to loud noises -- and ringing of the ears. Concussions can also be psychologically disruptive, and victims may exhibit irritability, anxiety and depression. They can also experience sleep disturbance and fatigue [source: Lew].

So far, we've mostly covered the physical effects of concussion, but concussions don't stop there -- they can also affect a person's ability to think, which can be especially debilitating. A person who has experienced a concussion can become confused and disorientated. He or she may also lack attentiveness or have difficulty concentrating. Concussions can impair memory and could even hamper a person's ability to learn. Post-traumatic or retrograde amnesia is not uncommon, and the centers of the brain that control planning, ability to follow instructions, verbal fluency and brain-eye coordination may all become discombobulated by concussion [source: Lew].


Common Causes of Concussions

Concussions can occur under a number of circumstances, and they happen frequently among athletes while playing sports. Staying focused and aware of your surroundings can help you avoid an inconvenient accident.
Hulton Archive/Archive Photos/Getty Images

Of the millions of estimated instances of concussion that occur annually in the United States, a significant number are sports-related. People of all ages participate in sports to stay active and in good health, but those benefits don't come without certain risks, and among them are the risks of head injury.

Bicycling straddles the realm of sports and non-sports activities -- while many ride exclusively for recreation, in some parts of the world bikes are the preferred mode of transportation. Bicycle accidents are among the top causes of concussions, so when riding, it's important to keep your wits about you. Always wear a helmet, and use extreme caution and maintain keen awareness of your surroundings and fellow travelers while riding on populated thoroughfares [source: Neurosurgery Today].


Motor-vehicle accidents also produce a large number of concussions each year. Today, auto makers design vehicles with safety standards to mitigate the risks of head injuries, but some cars have protective devices that specifically address the threat of front and rear impact while neglecting the sides of cars. Be aware of your vehicle's safety features, and know that the safest vehicles with regard to preventing traumatic brain injuries are those with not only front and rear, but also side airbag systems [source: Baird].

Each year, falling leads to more head injuries than any other activity. With respect to children who are still developing their motor skills, falling is especially dangerous. When kids are concerned, falls are the number-one cause of head injury, so make sure your young ones are well supervised, and when they're playing, be careful of tables and other objects on which they may hit their heads. Falling can lead to a vicious cycle of imbalance -- as a loss of balance can lead to the initial fall, and the ensuing concussion will further impair one's ability to balance oneself [source: Fusco].

Explosions affect a smaller demographic than some of the more common causes of concussion, but unfortunately for people in certain parts of the world, they're a part of everyday life. The U.S. military has done extensive studies and determined that explosions from improvised explosive devices and roadside bombs are responsible for concussions among servicemen and women, and the civilian populations they work to protect. Tragically, these threats are often difficult to predict and avoid, but thankfully, with proper treatment, victims can fully recover from most cases of concussion [source: Lew].

Next, we'll discuss appropriate treatment and possible complications of concussions.


Treatment and Complications of Concussion

A CT scan can be used to determine the seriousness of a concussion.

No matter how severe, the first response to any concussion is immediate cessation of the activity that led to the injury. Whether it was playing rugby, stocking groceries or dancing to heavy-metal music, the first thing you should do when you get a concussion is immediately stop whatever you were doing beforehand, and remove yourself from the danger zone. In other words: Don't get back on the horse.

If there's a question of whether trauma has caused a concussion or a more serious head injury, the victim should seek professional medical attention immediately. If an injury is more severe than a concussion, a CT scan or MRI can help to diagnose the extent of the damage. Severe head injuries are different from concussions, and they can involve hemorrhaging and other complications that require advanced treatment.


With regard to concussions, one complication that arises in a minority of cases is called post-concussion syndrome, which can last weeks to months after an accident, depending on the severity of the injury. There is controversy over whether the effects -- which can include symptoms like prolonged dizziness, fatigue, trouble sleeping, sensitivity to light and sound, anxiety, depression, memory loss and trouble concentrating -- are caused by physical factors, psychological factors, or by some combination of the two. There have also been very few studies evaluating the effectiveness of treating PCS. Currently, the consensus among practitioners is that the vast majority of uncomplicated concussions are resolved with rest alone, and patients typically recover fully. However, after consulting a physician, it may be determined that therapy or medication may help alleviate certain symptoms [source: Lew].

Perhaps you've heard of people saying that you're not supposed to go to sleep after a concussion, or maybe someone has told you that receiving a second concussion shortly after a first one can be devastating. The first statement, in fact, is a myth [source: Mitterando]. Sleep deprivation is not appropriate treatment for a concussion. However, there are severe consequences when someone has a second concussion before a prior concussion has fully run its course, so it's extremely important to fully recover before resuming the activity that caused the injury. In the event that someone has two concussions in a short period of time -- in a worst-case scenario -- the victim can experience what's known as second-impact syndrome [source: Lew].

Second-impact syndrome is rare but deadly. It occurs when a victim has already had a first concussion, and then, before that one has resolved itself, a second concussion triggers a chain reaction inside the head. It starts with disordered cerebral vascular autoregulation, which means that the brain loses its ability to keep the right amount of blood pressure flowing through the arteries in your organs [source: Anaethetist]. That leads to congestion in the arteries in your brain, creating pressure inside of your skull, and ultimately results in brain stem herniation and death [source: Lew]. Obviously, this situation should be avoided. That's why it's absolutely imperative to remove a concussion victim from whatever activity led to the injury until the symptoms have fully run their course.

Determining when that point has been reached may require clinical examination and can be a source of controversy among medical practitioners. However, there are several publicly available guidelines for making such judgments in the field. With time and rest, most concussions resolve themselves on their own.


Concussion Grading Systems

Tyler Hansen, quarterback for the University of Colorado, watches after being taken out of the game against the University of Oregon on Oct. 22, 2011, after sustaining a concussion. Experts say two concussions occurring closely together may be life threatening.
Justin Edmonds/Getty Images

There are three grades of concussions. Loosely speaking, determining which grade to assign a concussion depends on the duration of the loss of consciousness. The three primary systems used today were developed by Cantu, Colorado Medical Society, and American Academy of Neurology [source: Lew].

Using the Cantu scale, a concussion is categorized as grade one (mild) if there has been no loss of consciousness, and posttraumatic amnesia lasts for less than 30 minutes after the injury. If loss of consciousness occurs, but it last for less than five minutes, and posttraumatic amnesia lasts for more than half an hour, then Cantu classifies the injury as a grade-two (moderate) concussion. Finally, if the victim loses consciousness for more than five minutes, and posttraumatic amnesia persists for more than 24 hours, then the concussion is considered grade three (severe) [source: Lew].


The Colorado scale is simpler, and it says that a concussion that results in no loss of consciousness, no confusion and no amnesia should be classified as grade one. A concussion that results in no loss of consciousness, but some confusion and amnesia should be considered grade two. And a concussion that results in any loss of consciousness at all should be treated as a grade-three concussion [source: Lew].

The American Academy of Neurology's system is very similar to that of the Colorado Medical Society's. According to the AAN, a victim of a grade-one concussion may experience some transient confusion, but the concussion symptoms will resolve in less than 15 minutes, and no loss of consciousness will occur. A grade-two concussion is exactly the same, except the symptoms last for more than 15 minutes. A grade-three concussion, according to the AAN, is any that results in loss of consciousness, whether it lasts only a few seconds or several minutes [source: Lew].

There are cognitive tests for determining whether someone is experiencing concussion symptoms, and many of them provide their own "return to play" guidelines. AAN maintains that someone who has had a grade-one concussion may resume physical activity after 15 minutes of exhibiting no post-concussion symptoms. If someone has had a grade-two concussion, the victim can return to play after being symptom-free for one to two weeks and with clearance by a physician. But grade-three concussions require hospitalization, and the athletes must be asymptomatic for at least two to four weeks with a physician's clearance before returning to play [source: Lew].


Controversy Surrounding Concussions

Concussions are among the least understood medical maladies today, which is why they're hotly debated. One controversy surrounds the differing schools of thought regarding treatment and the assignment of concussion grades. In sports, most arguments center on when an athlete may return to play after experiencing a concussion.

The debate over the nature of concussion damage divides those who believe that the effects of concussions are structural or functional. Those in the first camp believe concussions result from physical alteration of the neurons in the brain. Their counterparts think that since concussion symptoms are typically short-lived and recovery is usually spontaneous and total, that the damage isn't consistent with structural damage to the brain, and therefore it must be functional [source: Peak Performance]. Both sides have valid points, and ongoing research continues to help the scientific community work toward drawing a firm conclusion.


Conflicts of interest are especially prevalent in cases of sports-related concussion. For a professional athlete, such an injury can affect one's livelihood, and that can lead to dangerous conflicts.

Underreporting of concussion is a major issue, and it's believed that a large number of concussions are never reported. Athletes may also downplay their symptoms to the best of their abilities in order to get the doctor's go-ahead for them to return to play. Because of such conflicts, companies like imPACT have developed complex tests and concussion management guidelines that are designed to detect and properly address every instance of concussion with precision and care [source: imPACT].

While most concussions resolve themselves, if they become complicated by post-concussion syndrome or second-impact syndrome, concussions can result in lifelong disabilities. Therefore, it is important to seriously evaluate each case and perhaps even consult several different tests and guidelines to ensure that a person isn't taking on undue risk or putting him- or herself in danger by resuming physical activity too quickly. Of course, while concussions can't always be avoided, the best practice is to prevent them from happening in the first place.


Concussion Prevention

Protective headgear can help mitigate the impact of collisions and reduce the risk of concussion.
Thomas Northcut/Lifesize/Thinkstock

For youngsters and old folks, falls are the number-one cause of head injuries, so keep your house free of clutter and well-lit to prevent tripping. You may even consider installing hand rails in certain places like the bathroom so that you can catch yourself if you take a spill on a slippery tile. Also, when selecting footwear, use common sense. While it may be fashionable to wear flat-soled loafers, if it's a rainy autumn day and there are wet leaves all over the ground, you may want to opt for shoes with more traction.

When you're engaging in any physical activity that may result in head injury, wearing protective headgear will vastly reduce your chances of experiencing a concussion. Wearing a helmet will also make your athletic experience more enjoyable, since you'll have one less thing to worry about. When swimming, never dive head-first into a body of water unless you know for a fact that it's too deep for you to reach the bottom.


Always wear your seatbelt, and if you're renting or purchasing a new vehicle, try to seek out one with side-impact airbags. It should become a reflexive movement to reach for your seatbelt anytime you sit in an automobile. Furthermore, you should encourage others to do so as well. If you're driving, don't put the car in gear until all of your passengers' seatbelts are securely fastened.

Seatbelts, airbags and helmets can all help prevent or at least lessen the damage of concussion. It's also important for those who are susceptible to falling to wear footwear with good traction to minimize the risk of slipping. And it's also important to keep a clean, clutter-free house to decrease the chances of tripping and hitting your head. The best preventative practice, however, is simply to use your head. If you're well-rested and alert at all times, you'll be more aware of your surroundings, and less likely to fall victim to a concussion-inducing accident [source: Mayo Clinic].

If you're interested in learning more about concussions, take a look at the links on the next page.


Lots More Information

Related Articles

More Great Links

  • Baird, Daniel. "Preventing Concussions." U of T Magazine. Winter 2011. (Dec. 21, 2011)
  • Chicago Institute of Neurosurgery and Neuroresearch. "Concussions." (Dec. 21, 2011)
  • Cunha, John P. "Concussion." 2011. (Dec. 16, 2011)
  • Fusco, Evan. "Head Injury." (Dec. 16, 2011)
  • ImPACT. "ImPACT Background." (Dec. 16, 2011)
  • Lew, Henry L., MD, PhD. "Review of sports-related concussion: Potential for application in military settings." Journal of Rehabilitation Research and Development. Vol. 44, No. 7. pp. 963-974. 2007. (Dec. 16, 2011)
  • Mayo Clinic. "Concussion Prevention." Deb. 22, 2011 (Dec. 16, 2011)
  • NEUROSURGERYTODAY. "Sports-Related Head Injury." December 2011. (Dec. 16, 2011)
  • Mitterando, Jim. "ASK THE DOCTOR: JUST THE FACTS - Common medical myths." 2002. (Dec. 16, 2011)
  • Peak Performance. "What should athletes do when concussion strikes?" (Dec. 16, 2011)
  • Smith, Stephanie. "What will happen to former NFL player's brain?" CNN. Feb. 26, 2011. (Dec. 21, 2011)
  • The Worldwide Physiologist. "Vascular Autoregulation." 2000. (Dec. 16, 2011)
  • Yamamoto, Loren G. "Tidbits on Raising Children -- Making Our Most Important Job Easier By Doing it Better: Chapter 56. Head Injuries, Concussions and CAT Scans." (Dec. 16, 2011)