How Concussions Are Diagnosed

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Diagnosing a concussion can be tricky. Although any degree of head trauma can cause one, the most common concussions—those that result from mild head injuries—do not involve identifiable bleeding or bruising in the brain.

This means an imaging technology such as magnetic resonance imaging (MRI) or computed tomography (CT) that can diagnose a severe traumatic brain injury (TBI), isn't a viable way to diagnose a concussion.

Since brain scans can identify bruising or bleeding in the brain, but not the cellular damage thought to cause concussion symptoms, doctors must rely on a careful assessment of symptoms and neuropsychological function.

Sometimes this is done on-site, immediately after an injury, when an athlete experiences a blow or jolt to the head and a decision must be made quickly about whether he or she can safely get back into the game.

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Concussion Testing

The symptoms of a concussion can vary greatly. Sometimes it's quite obvious that someone may have one. But just as often the symptoms are vague and subtle.

A person may simply feel "off" or as if they're not "getting" things. In any case, getting a definitive diagnosis of a concussion typically requires looking at several factors.

Because there's no simple test for diagnosing a concussion, several steps are involved. The Weill Cornell Brain and Spine Center, for example, narrow it down to these: 

Interview testing for various types of amnesia: These include the documentation of the presence and extent of any retrograde amnesia, which refers to a lack of memory about what happened just before a brain injury occurred, loss of consciousness, and post-traumatic amnesia. Post-traumatic amnesia refers to loss of memory for events after the trauma and is especially important because it will tell a doctor the most information about a patient's prognosis.

Determination of the severity of symptoms and how extensive they are: Often this is part of an on-site assessment of an athlete who's been injured on the field and uses a standardized scale. The most common of these, the Sideline Concussion Assessment Tool, or SCAT-2, looks at symptoms, attention, memory, recent events in the game or event, and checks for problems with balance and coordination.

Examination of neurological symptoms: This may involve tests of strength, sensation, reflexes, coordination, and other neurological functions.

Concussion Doctor Discussion Guide

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Pre-Concussion Testing

Besides diagnosing an initial concussion at the time of an injury, it's important for people who are going to participate in an activity—especially student athletes who want to participate in a high-impact team sport such as football—to undergo pre-concussion testing. In fact, this usually is a requirement of high schools, colleges, and highly competitive travel teams. 

The main reason an athlete needs pre-concussion testing is if they subsequently have a suspected concussion, their functioning and injury effect can be compared to the athlete's baseline, allowing for better management decisions.

This means that performance on a post-concussion test is not necessarily "good" or "bad" on its own, but must be based on whether or not there is a significant decline in comparison to the baseline that was set prior to the head injury.

If a student athlete has a slower response or lower accuracy on a post-concussion test after a head injury, then the lower score could be a sign of a concussion. Along with a neurological examination and overall symptoms such as sleepiness, pain, or trouble concentrating, the results of a post-concussion test can be used to help determine whether the athlete has suffered a concussion.

Pre-concussion testing generally includes a set of neuropsychological exams developed to assess and score a young athlete on skills that involve several aspects of his or her brain function. Pre-concussion tests include tasks that evaluate problem-solving, response time, speed, vision, and coordination.

There's no gold standard pre-concussion screening tool required by an authoritative medical or sports association. There are a variety of ways to establish a pre-concussion score, though, including an in-person clinical evaluation or a pre-set questionnaire. There also are a number of available skills tests on the market that can be used to establish a baseline score for a player before the season begins.

Pre-concussion tests may be scored by a computer or by a medical professional, depending on the type of examination and on the rules of the league or the school. 

The baseline results are recorded and saved so that if an athlete suffers from a suspected concussion, he or she can take a repeat test for comparison.

An example of the computer-scored test was developed by researchers at the University of Pittsburgh's Sports Medicine Center and is called Immediate Post-Concussion Assessment and Cognitive Testing system, or ImPACT. This test measures an athlete's memory, reaction time, and processing speed in order to help determine when they can safely return to sports after a head injury. The ImPACT program is currently used at many high schools and colleges as well as by the National Football League (NFL) and National Hockey League (NHL).

Frequently Asked Questions

  • Can I self-diagnose a concussion?

    Only a doctor can definitively diagnose a concussion. That said, certain symptoms may develop after a blow to the head that point to a concussion, including a headache, nausea and/or vomiting, dizziness, feeling hazy or groggy, and sensitivity to light or noise.

  • How can I tell if my child has a concussion?

    Some people lose consciousness after sustaining a concussion, often for a very brief time, but this doesn't always happen. Signs to look for in your child (or anyone else) that indicate they may have a concussion include:

    • Inability to remember things that happened either before a hit or fall or afterwards
    • Seeming dazed or stunned
    • Tending to forget things they're asked to do
    • Moving clumsily
    • Taking a long time to respond to or answer questions
    • Having changes in mood, behavior, or personality
  • Is a concussion the same as a TBI?

    A concussion is regarded as less severe as a TBI (traumatic brain injury); in fact, the term "mild TBI" often is used synonymously with concussion. Even so, concussions are serious injuries, especially when a person has more than one. They are not life-threatening but can have long-lasting effects and so should be diagnosed by a doctor and treated.

  • How many concussions are diagnosed each year?

    According to the Brain Injury Research Institute, each year, between 1.6 and 3.8 million people sustain a concussion related to a sport or recreational activity. It's unknown how many people experience concussions not related to a sport or physical activity, as it's believed many of these are never diagnosed.

16 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  16. Wellspan Health. Non-sports related concussions often go undiagnosed.

Additional Reading

By Heidi Moawad, MD
Heidi Moawad is a neurologist and expert in the field of brain health and neurological disorders. Dr. Moawad regularly writes and edits health and career content for medical books and publications.