You know it when you see it, yet it’s still hard to define.
While many people can recognize a concussion when they see it, it can actually be a challenge to define exactly. That’s partially because a concussion is another name for a “mild” traumatic brain injury (TBI)—and it’s not always easy to determine what counts as mild.
“There are a lot of definitions of what a concussion is. It's kind of mind-boggling; it sort of adds to the confusion of what concussion is,” says Steven Flanagan, MD, chair of the Department of Rehabilitation Medicine at NYU Langone Health.
The Centers for Disease Control and Prevention (CDC) defines a TBI as a “bump, blow or jolt to the head … that disrupts the normal function of the brain,” and if it’s mild, it simply results in “a brief change in mental status or consciousness.” This still leaves some room for interpretation: What is brief? What is normal?
“If there's loss of consciousness, by definition, it has to be less than 30 minutes,” says Dr. Flanagan, “and the symptoms generally resolve within hours, days, weeks, [or] sometimes a little bit longer.”
When loss of consciousness is prolonged, then it’s considered a moderate or severe TBI. These are life-threatening emergencies and they can cause long-term effects on the body. Thankfully, severe TBIs are much less common than mild ones, or concussions. (Here are warning signs that a TBI is an emergency.)
A concussion is often defined by its symptoms, such as memory and thinking problems, mood changes, headaches, sleepiness, and sensitivity to light or noise. (Learn more symptoms of concussion here.) However, it helps to understand what causes a concussion. While a severe TBI may include penetration of the skull and brain—an obvious injury—a concussion can be a lot more subtle.
“The brain is actually very soft. It has the consistency of formed Jello,” says Dr. Flanagan. “When your head gets jerked backwards and forwards and sort of to the side, the brain can actually compress on itself, stretch, [and] twist a little bit.”
This unnatural twisting and stretching doesn’t just hurt the brain tissue, but it stretches out a part of your nerve cells called axons. “The axons are like telephone wires, or like wires in a computer network. If they're stretched, there's going to be a period of time where they're just not gonna work properly, and they're not gonna transmit information properly,” says Dr. Flanagan.
These injuries to the axons is what leads to the telltale signs of concussion. For example, if the coordination between your eyes and ears are off because of axon malfunction, your balance is going to be off.
But the good news about a concussion is that most people can recover without any major issues. Learn more here about concussion recovery here.
Dr. Flanagan is the chair of the Department of Rehabilitation Medicine at NYU Langone Health. He specializes in brain injury rehabilitation.
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There are a lot of definitions of what a concussion is.
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It's kind of mind-boggling.
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It sort of adds to the confusion of what concussion is.
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Most definitions will say that if there's loss of consciousness,
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it's less than 30 minutes.
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Typically, oftentimes, there isn't loss of consciousness,
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and symptoms generally, not always, resolve within days to weeks,
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sometimes a little bit longer.
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So a concussion is a traumatic brain injury,
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but it's considered on the milder end of the spectrum continuum.
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So if there's loss of consciousness, by definition,
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it has to be less than 30 minutes, based on most definitions,
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and the symptoms generally resolve within hours, days,
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weeks, sometimes a little bit longer.
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When there's an injury to the brain, let's say a concussion,
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the first thing to realize is the brain is actually very soft.
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It has the consistency of formed Jello.
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And when your head gets jerked backwards and forwards
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and sort of to the side, the brain can actually compress on itself,
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stretch, can twist a little bit,
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and that compression, that stretching, the twisting,
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will actually stretch all of the nerve cells,
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or part of the nerve cells called the axons,
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and the axons are like telephone wires,
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or like wires in a computer network.
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If they're stretched, there's going to be a period of time
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where they're just not gonna work properly,
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and they're not gonna transmit information properly.
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And in order for us to do what we would normally do as humans—
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think, remember, concentrate, maintain our balance,
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have our eyes and our ears coordinate properly
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so our balance doesn't go awry—
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all of that's gonna be off or it could be off,
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and those are the symptoms of concussion,
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and it's explained by the stretching of those nerve cells.
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Eventually, in the vast majority of cases
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after mild traumatic brain injury, things settle down,
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and then your symptoms resolve.
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Acute mild traumatic brain injury (concussion) in adults. Waltham, MA: UpToDate, 2020. (Accessed on March 31, 2020 at https://www.uptodate.com/contents/acute-mild-traumatic-brain-injury-concussion-in-adults.)
Severe TBI. Atlanta, GA: Centers for Disease Control and Prevention, 2019. (Accessed on March 31, 2020 at https://www.cdc.gov/traumaticbraininjury/severe.html.)
Symptoms of traumatic brain injury (TBI). Atlanta, GA: Centers for Disease Control and Prevention, 2019. (Accessed on March 31, 2020 at https://www.cdc.gov/traumaticbraininjury/symptoms.html.)
Traumatic brain injury & concussion. Atlanta, GA: Centers for Disease Control and Prevention, 2019. (Accessed on March 31, 2020 at https://www.cdc.gov/traumaticbraininjury/index.html.)