Could you have a concussion and not know it?

A concussion is easier to miss than you think—unless you know the signs.

a middle aged Black woman is examined by an older white male doctor in a hospital room; the doctor shines a light in the patient's eyes to check for signs of a concussion

Updated on April 19, 2024.

A famous 2017 study published in JAMA of the brains of 202 deceased football players—from high school players to pros—found evidence of chronic traumatic encephalopathy (CTE) in 87 percent of them. That included 110 out of 111 brains of NFL players.

How does CTE develop? One way is through repeated concussions.

The kind of head injuries sustained by football players can be violent and obvious to all witnessing and experiencing them.  

But a lot of concussion symptoms are very subtle, says Scott Scherr, MD, an emergency medicine specialist in Las Vegas. What’s more, people may not make the connection between the symptoms and the injury. Here’s what to look out for after you’ve received a blow or bump to the head, no matter how small.

Concussions and your brain

A concussion is a type of traumatic brain injury (TBI), explains Dr. Scherr. “Anything can cause a concussion, from a minor bump to a major blow to the head,” he says.

A concussion comprises two parts: the initial hit and then the brain shifting inside the skull. That stretches and damages brain cells and could disrupt the connections between them.

How concussions happen

Age is a factor in who’s at greatest risk for having a concussion, according to Scherr. “Car accidents are generally the most common causes of concussions,” he says. “In very young population you see a lot of falls. Once kids start doing sports, concussions tend to be related to sports. For elderly patients you start seeing falls again.” 

If you’re in a car accident or have a bad fall you’ll know if you have a concussion, right?

Not necessarily. Symptoms may start right away, though they may emerge days or even weeks after an injury. Delayed symptoms might make it difficult to connect your injury with the symptoms you’re experiencing.

“Some people complain of mild dizziness, nausea or vomiting and just blow it off,” Scherr adds.

Concussion symptoms

“The first thing we look for when someone sustains a blow to the head is cognitive impairment,” Scherr says. “Short term memory loss, when someone can’t remember the injury or what happened before it, is common.”

Other common symptoms include headache, neck pain, nausea, dizziness, fatigue and feeling dazed. Depression, anxiety, loss of appetite and problems sleeping may appear after a concussion.

See a healthcare provider (HCP) within one or two days of a suspected head injury, and immediately if you experience any of these more serious symptoms:

  • Seizures
  • Drowsiness or inability to wake up
  • Confusion
  • Slurred speech
  • Loss of consciousness
  • Headache, nausea, or vomiting that does not go away

Concussion myths

Having a concussion is not like what you might see in the movies, where the good guy punches the bad guy in the head and the bad guy jumps up good as new a few minutes later. In real life, if someone loses consciousness for more than 30 seconds, they should be checked out in an emergency department.

It’s commonly said that you should never fall asleep after a concussion or you’re likely to slip into a coma or die. That myth probably stems from misunderstanding what’s known as the “lucid interval.” This is a temporary period during which someone with brain bleeding wakes up from unconsciousness and seems fine, but then soon slips into a coma.

Instead of keeping someone who has had a concussion awake, let the person sleep but wake them up every few hours to make sure they wake up easily and their condition isn’t getting worse.

Treatment for concussions

Symptoms of concussions should go away on their own. But Scherr says there’s no standard length of time for symptoms to stick around.

“It could be days to weeks to months,” he says. “It depends on how severe the injury is and how your body reacts.”

The most important thing you can do after a concussion is rest. Rest helps the brain heal. Other recovery tips include:

  • Get plenty of sleep at night
  • Avoid activities that are physically or mentally demanding
  • Return to normal activities gradually and only with your HCPs approval
  • Avoid alcohol and drugs
  • Try not to multitask, in order to rest your brain
  • Try to avoid computers and screens as much as you can, to rest your brain. Light may also trigger certain symptoms.

“Once you get a concussion you want to do what you can to prevent a second concussion,” says Scherr. “On a cellular level, once a concussion happens you get a lot of changes in the brain. With a second concussion, there’s even more changes, and you may start to become more sensitive to TBIs.”

Article sources open article sources

American Association of Neurological Surgeons. Traumatic Brain Injury. Edited on February 3, 2020.
Centers for Disease Control and Prevention. What Is a Concussion? Last Reviewed: February 12, 2019.
Cleveland Clinic. Brain Bleed, Hemorrhage (Intracranial Hemorrhage). Last reviewed on December 4, 2023.
Mayo Clinic. Concussion. January 12, 2024.
MedlinePlus. Concussion. Accessed April 19, 2024.
Xiao H, Yang Y, Xi JH, Chen ZQ. Structural and functional connectivity in traumatic brain injury [published correction appears in Neural Regen Res. 2017 Oct;12(10):1562]. Neural Regen Res. 2015;10(12):2062-2071.
Zhou Y, Kierans A, Kenul D, et al. Mild traumatic brain injury: longitudinal regional brain volume changes. Radiology. 2013;267(3):880-890.

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