Most people in the general population will have at least a vague idea of what the diagnosis of a concussion entails, at least to the extent of knowing that it is due to a head injury. Truly understanding what a concussion is, however, depends on a more detailed definition of what takes the diagnosis from just a simple bump of the head to an actual concussion.

One very significant distinction that makes a brain injury a concussion is that there is change in the brain function, not the actual structure itself. A variety of causing factors, from being hit in the head to whiplash, can trigger changes in the brain that affect normal functioning. This is a large reason why so much focus is put into concussion prevention for young children, since this functional change could affect their developmental growth.

Although a concussion can be labeled as a mild traumatic brain injury, it actually involves a very complex pathophysiological process, which affects the brain. This process interferes with the regular function of the brain, which can be the part of the concussion that is most alarming to individuals suffering from a concussion. There are metabolic changes that take place within the brain following the concussion.

Loss of consciousness should not be the sole diagnosing factor for any head injury, particularly concussions. In order to be thorough in the diagnosis, a health care provider might perform a physical exam, focusing on behaviors that might be affected by a concussions. This includes thinking abilities, coordination, and reflexes. If necessary, this could be followed up by an EEG, MRI, or CT scan of the head to determine whether there is further damage. Recovery from such injuries depends on the severity of the particular case and specific symptoms that the patient experiences.

For a general definition, one should understand that concussions could produce symptoms in many different ways. The neurobiological changes can affect the injured person in multiple ways mentally, whether by hindering their memory, by making it difficult to concentrate, or a variety of other ailments that will be discussed later. There are also physical symptoms that can occur, from headaches to lack of energy. On top of these two primary affected areas, the injured person might also suffer from emotional conflicts or sleep disturbance. Symptoms in patients are also shown to worsen significantly with repeated concussions or head injuries, as the injured person is already at significant neurobiological risk. Taking the right steps towards prevention is the primary method for the safety and protection against concussions.

Other topics that will be discussed in-depth in later chapters are specific symptoms, causes, risk factors, and complications of concussions. Each of these have many potential outcomes for an individual who suffers a brain injury, so it is important to know all of the possible outcomes before somebody puts their future at risk by playing sports with a brain injury.

General Overview:

Here is a brief outline, including some of what has been mentioned above just to provide a thorough overview of what is to come:

• The Brain: Understanding the structure and function of the human brain can help paint a complete picture for how a concussion or any brain injury truly affects the hurt individual. As mentioned above, the changes occurring are functional rather than structural, and this article explains how these changes take place. Making the connection between these neurobiological changes and the symptoms experienced can shed a new light on why certain symptoms take place.

• Symptoms: The symptoms for a single concussion are often mild and go away after a short period of time, typically anywhere from a week to a month. If symptoms persist, however, this could be indicative of more severe injury or a developing condition such as CTE. There are also more mild conditions, such as post-concussion syndrome, that will typically resolve themselves in six months to a year. Knowing the symptoms is the first step in raising awareness, as it allows hurt individuals, teammates, coaches, family, and bystanders to be aware when somebody might be suffering from a concussion. Without this awareness of symptoms, a hurt individual might not seek medical help for what they are experiencing and instead continue to put themselves at risk for further injury.

• Causes: There are numerous ways in which a concussion can occur. Some of the most common causes found are accidental falls, contact sports, automobile accidents, and recreational activities. Certain precautionary measures can be taken in these areas to reduce the number of concussions as a result.

• Risk Factors: What might put an individual more at risk for serious brain injuries? There are different variables and risk factors, all of which can change depending on age, sex, and occupation.

• Complications: Brain injuries are no simple matter, no matter how mild the injury is. There are numerous complications that can arise for somebody with a brain injury.

• Treatment and drugs: The most common treatment for a concussion is simply rest, in order to allow the brain the time it needs to recover. For some, such as those suffering from CTE or worse conditions, treatment might be focused more on easing the damage rather than healing entirely, as this condition is irreversible.

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• Prevention: The best step towards dealing with concussions is prevention, and awareness is the key factor of this.Raising awareness about the risks of multiple concussions is the best way to keep individuals from suffering from worse degenerative brain conditions, such as CTE.

• Long-term Effects: Mild, one-time concussions won't often incur long-term effects. If they do, this often indicates that there is something worse than just a mild injury. Brain damage can lead to loss of occupational and emotional skills, both of which can have a negative impact on certain aspects of an individual's life.

• Costs: Treating a brain injury is no cheap matter. For somebody with a serious condition, these costs can add up to over a million dollars long-term. Since medical attention is necessary and can't be avoided for someone with brain damage, these costs can create a huge financial burden for the individual and his or her family. With long-term conditions, rehabilitation and therapy could be necessary costs in order to regain skills or recover from certain symptoms. Rehabilitation over a long period of time can incur great financial costs.

Concussions cause neurobiological changes within the brain. In order to understand concussions on a deeper scientific level, it is necessary to dive into the biology behind the changes that the brain undergoes with a mild traumatic brain injury (TBI). The details and connections behind these changes can unveil correlations between injuries and symptoms or why specific precautions are necessary to take regarding concussions. The damage caused by a concussion is specific to functional changes not structural damage within the brain, and these functional changes manifest in different ways and in different degrees depending upon the severity of the injury.

• The Initial Impact

Beginning with that first blow to the head or the jolt that moves the body, it is believed that this sudden movement or impact creates a wave of energy that passes through the brain tissue.¹ This initiates a cascade within the brain that affects areas of ionic, metabolic, and physiologic function. If the concussion is less severe, then these issues should correct themselves in a short amount of time and be back to normal. The initial impact that causes the concussion is not fatal in itself, but it is the following aftereffects that present potential health problems.

In ordinary circumstances, the skull is present to protect the brain from damage or injury. In the event of a concussion, however, the skull is actually doing the reverse by being a blockade for the brain to ram into. Imagine a car accident, in which the car runs into a wall and stops moving, but the motion propels the driver's body forward still. This is typically the case with a concussion as well, in which the skull stops moving but the wave of energy propels the brain still, and it has a rough impact with the skull. In this case, the body part intended to protect the brain is actually harming it. Studies have shown that the brain can actually stretch or twist during this motion and this contortion of the brain strains many of the parts that deliver important functions. This puts stress on the brain, as will be discussed in more detail below.

• Role of Recovery Time

The length of time that recovery takes plays a role in the vulnerability of the brain to a second injury. The quicker the brain can recover, the quicker blood flow increases back to the brain. However, during the recovery process, the cerebral blood flow is reduced and this can present many issues. The lack of sufficient blood to the brain contributes to cell dysfunction, which also increases the cell's vulnerability to a second injury. Repeated damage in such a short amount of time, before the brain has had the chance to fully recover, creates further problems and worsens the damage from the first impact. A closer look at the damage that repeat concussions can cause will be explored later in the article, but first it is necessary to understand just what is happening with cell dysfunction and the changes that concussions cause.

• Cell Dysfunction

As mentioned, the recovery period after the initial impact can result in what is called cell dysfunction. In order to understand what is different about the function of the brain after a concussion, one must first understand what it is like in regular functioning circumstances, or before the concussion occurs.

When the neuron process is disrupted by an injury, the fragile axons are likely to swell and even break away from the cell body and degenerate. This disrupts the cell communication, as the axons are the means of communication from neuron to neuron, and the degeneration of an axon releases toxic levels of the neurotransmitters mentioned above into the rest of the cell. Even after the injury, damage can continue to take place, as neurons surrounding the injured area can continue to die and worsen the injury over the next day. The contortion of the brain during the initial impact can also contort all of these neurons and axons, which in turn impacts the function ability of the brain.

The sudden, overwhelming release of neurotoxins creates an energy crisis in the brain, which explains why the pace of the brain is much slower following a concussion. The brain is then forced to work harder to accomplish ordinary tasks, so the injured person will experience a sluggish state until recovery is fully accomplished. Many of the symptoms experienced during this stage can be attributed to this energy crisis and the overworking of the brain while it attempts to recover.

Cognitive function is impaired because many of the neural pathways are either damaged or destroyed, which makes it difficult to access certain memories. In a properly functioning brain, the pathways between neurons would be the way that a person remembers certain words or shapes, so with the axons either twisted or degenerated, this pathway is inaccessible.²

An individual suffering from a concussion might experience difficulty remembering what happened in the minutes following the initial impact, or they might have difficult with comprehension or finding the right words to say. This confusion and incomprehensiveness is the first evident sign to bystanders that the injured person is experiencing a concussion, although no outward physical signs are evident.

• Science of Recovery

With all of this damage occurring and causing a cascade of further problems, how does the brain begin to repair itself? Under normal function, the neurons operate properly by maintaining a certain concentration of specific ions on either side of their cellular membrane. These ions are primarily composed of Sodium (Na+) and Potassium (K+). The most common state for neurons is having a higher concentration of these ions outside of the cell membrane, meaning that the inside has a more negative charge than the outside does. One can imagine a neuron at rest as being comparable to a battery, which has two ends of opposite charge, one end being positive (+) and the other negative (-). This is called polarization. The state of polarization provides potential for a flow between the two ends to produce enough charge or energy to send chemical messages across the axon.

In order for a neuron to send a message, since that is the job of the axons, it is necessary to excite the ions by removing the neuron from this resting state of polarization. This involves making the inside of the cell membrane more positively charged, which is accomplished by sodium-potassium pumps that move ions in and out of the cell membrane. For the ions to enter the axon, there are multiple ion channels within the axon that allow for this to occur.

During a concussion, however, these ion channels are not carefully maintained as they usually are, and they instead open to release the ions from within the axon. This forces the cell to kick into overdrive and try to restore the ion level back to normal, which can use a lot of the brain's already limited energy. This restorative process requires time and nutrients that the brain may have difficulty acquiring, due to so many pathways and functions being shut down.

• Repeated Concussions and CTE

While the obvious answer might be that an individual with a concussion should just rest to avoid further damage, a critical factor playing a role is the fact that so many concussions go undiagnosed. Without the obvious display of loss of consciousness, many young people or children may not realize that their head trauma was truly a concussion. Without any further injuries, this concussion would heal over time and return to normal. However, if they are unaware of the vulnerability of their injured brain, the individual may not take the necessary caution or give their brain the rest it needs to recover. This unawareness exposes them to potential accidents or injuries, and the severity of a second concussion could be far worse. Many young athletes are simply unaware of what exactly determines a concussion, so these brain injuries continue to go underdiagnosed. Athletes at risk may also be afraid to report a concussion in fear of losing their status or position on their team, and thus continue to put themselves in danger despite a concussion.

Awareness of the dangers of repeated concussions has increased in the last couple of decades, as medical issues have arisen surrounding boxers, football players, and other sports players who have experienced multiple concussions. The rise in awareness of a condition called chronic traumatic encephalopathy (CTE) has sparked further interest and research into the changes that the brain undergoes with multiple concussions. CTE can be difficult to diagnose because the symptoms manifest in behavioral mechanisms, often similar to the symptoms of other brain disorders such as Alzheimer's or Parkinson's.³ Symptoms affect emotions, memory, and mood, just to name a few of the primary reactions.

Due to the many neurobiological changes caused by concussions, the brain responds by what is called cerebral atrophy, which is also seen in Alzheimer's. This is, put simply, the actual shrinking of the brain. Along with this is the development of neurofibrillary tangles, which are formed by a protein called tau. Further research is still necessary to fully understand these tau tangles, because much remains unknown by scientists and researchers about the precise details regarding this formation. Regardless of lack of details, research does show that these neurofibrillary tangles are present in all cases of Alzheimer's and CTE.

• The Challenge in Studying the Changes