What Is a Concussion? An Explanation for the NFL

The NFL and its cronies seem to have a very difficult time understanding this concept, so I’ll take a stab at providing an explanation. What is a concussion? Here’s the concise answer, focused on adults.

 

The Basic Concept

A concussion—sometimes referred to as mild traumatic brain injury—can occur as a consequence of direct or indirect (via whiplash) impact to the head. The result is a reversible syndrome with signs and symptoms that are directly attributable to alterations in the brain.

What seems on the surface like it should be a relatively simple diagnosis to make is not always so straightforward.

Why?

A few reasons.

First, the signs and symptoms—such as confusion, amnesia, headache, and dizziness—are sometimes subtle, not always immediate, and do not have to include loss of consciousness. Furthermore, routine imaging of the brain is often normal, and there is no single blood test to confirm or refute the diagnosis. The changes occurring in the brain are largely functional in nature, and any structural abnormalities are on a microscopic level (i.e. unable to be detected by the aforementioned imaging). As such, cognitive examinations, each with its own drawbacks, are often used to support the diagnosis.

For the record, despite these diagnostic challenges, when an NFL quarterback hits his head on the ground and is subsequently noted to be stumbling (click here for video), you’re probably dealing with a concussion.

 

Zooming In

So what exactly is going on in the brain at the microscopic level?

All sorts of things, none of which is desirable.

Neurotransmitters—the key molecules that help neurons (nerve cells) communicate with each other—are released in haphazard fashion. Ions, which are key in maintaining proper cellular function, end up in the wrong places. Alterations in blood flow can add to the chaos, and the end result is cell injury. In more severe cases, axons—the long appendages of neurons along which nerve impulses are transmitted—can experience structural damage.

In order to contend with the above, energy is required to make the necessary fixes. It turns out, however, that mitochondria—the energy producing structures in cells—might not function optimally under the circumstances. Compounding matters is the fact that all the injury can lead to inflammation, which can exacerbate the injury further.

Given the complexity of the human body, differences in genetic susceptibility to such changes can translate into a range of outcomes among individuals with seemingly similar head injuries.

 

Management

The overall goal of concussion management is to allow sufficient time for cellular function and structure to return to their previous state. And that involves allowing the cells to rest—in other words, both cognitive and physical rest (with exact instructions varying by the case).

What makes a determination regarding the timing of return to normal activity difficult is that what is being monitored—the course of symptoms—is a somewhat crude marker of what is going on at a molecular level.

Similarly, a decision regarding return to play for athletes is not formulaic and must take into account symptoms, prior concussions, the estimated risk of recurrent events, and other such factors that are not always simple to measure or predict.

 

Risks

Given what can often be a relatively mild and largely reversible situation, it’s easy to take a concussion lightly. Unfortunately, not all afflicted with the condition are so lucky, meaning that caution and common sense are warranted.

To start, a certain number of individuals who suffer a concussion can develop the so-called post-concussion syndrome, an occasionally prolonged entity defined by ongoing headaches, dizziness, and cognitive impairment that has many potential causes, including perhaps psychogenic ones.

Second, it is generally accepted that those who return to activity prematurely after a concussion are predisposed to additional events. In rare circumstances, what is termed the second impact syndrome can lead to dangerous brain swelling and even death.

And finally, those with repeated head injuries throughout life leave themselves at risk for chronic traumatic encephalopathy (CTE). This phenomenon gets back to the idea of microscopic changes and highlights the reality that such changes might not be completely reversible, especially when insults are cumulative. In the case of CTE, autopsy specimens reveal the abnormal handling and distribution of a protein called tau. During life, symptoms can include cognitive deficits, behavioral changes, and depression, though the ability to make a clean diagnosis (prior to having access to brain tissue at the time of death) is not possible.

 

So why, you might ask, would someone risk a premature return from a concussion? At play is the highly relatable human practice of placing short-term reward ahead of long-term consequence. But for those surrounding the person who opts to make such a decision, one other factor is usually required—an ulterior motive.