Concussion, persistent symptoms, dementia, and CTE: how are they different?
Clear definitions of four terms that often get mixed up after a head injury
Whether your injury came from a car crash or a tackle, you may hear four terms used almost interchangeably. They are concussion, lasting concussion symptoms, dementia and CTE. Headlines about former football players add to the worry. If your memory has not felt right since the injury, it is natural to wonder which of these you are dealing with.
These four terms describe different things. They differ in what they are, in how they are found, and in what usually happens over time. Knowing the differences can help you ask sharper questions and make sense of what your care team tells you.
This article walks through each term, explains where they overlap, and clears up some common mix ups about repeated head impacts.
Concussion: a mild brain injury
The CDC describes a traumatic brain injury (TBI) as an injury that changes the way the brain works [6]. A concussion is the mild form. It can come from a bump, blow or jolt to the head, or from a hit to the body that whips the head and brain quickly back and forth [6]. Falls, motor vehicle crashes, firearm injuries and assaults are the most common causes of TBI [7].
Symptoms can affect how you feel, think, act and sleep [1]. In the early days you might lose track of conversations, ask the same question twice, or forget why you walked into a room. The word mild refers to the injury itself. The symptoms can still be hard to live with.
According to the CDC, a concussion can be identified without a CT scan, though a scan may be used if there is a risk of bleeding in the brain [6]. A person can have a concussion even when it does not show up on tests [6].
Most people feel better within a couple of weeks [1]. People who have had several concussions may take longer to recover. Some go on to have lasting trouble with concentration, memory, headache or balance [6].
If memory or attention problems linger, ask your care team to check whether you are ready to drive before you get back behind the wheel. Rules about driving after a brain injury vary from state to state.
Persistent postconcussion symptoms
Sometimes symptoms hang on past the usual recovery window. Health care providers often call this persistent postconcussion symptoms. You may also hear the term postconcussion syndrome. The label describes symptoms that began with the injury and have not yet cleared.
An international consensus on sport concussion, agreed in Amsterdam in 2022, defines persisting symptoms as those lasting more than 4 weeks, at any age [8]. It adds that such symptoms may have been there before the injury, may come from the concussion, or both [8].
The 2021 VA and Department of Defense guideline for mild TBI takes a practical approach to lasting symptoms. It suggests care that focuses on symptoms and is led by primary care for most people [2]. If thinking problems such as poor memory, focus or planning hang on after other causes are addressed, it suggests a short course of cognitive rehabilitation [2]. For ongoing dizziness, it suggests vestibular rehabilitation, which uses exercises to retrain the balance system [2].
The guideline also says mental health conditions should be assessed and treated the same way whether or not a person has had a mild TBI [2]. It asks providers to take symptoms seriously and not write them off as purely psychological [2].
A composite example
Imagine a 29 year old who was rear ended on her way to work. Three months later she still loses her place in emails and forgets parts of meetings. After reading about CTE online, she starts to fear the worst.
Her care team finds poor sleep and neck pain, treats both, and refers her to a speech language pathologist for memory strategies. Her symptoms began with a single injury and have been slowly easing. That pattern is far from the one researchers use to describe traumatic encephalopathy syndrome, which requires substantial exposure to repeated head impacts and a course that gets worse over time [3].
Dementia: a broad term with many causes
Dementia is a broad label that covers many diseases. It describes a decline in memory and other thinking skills that becomes serious enough to limit a person’s independence. The TES research criteria, described later in this article, grade daily function in steps that run from independent, through mild limits, to mild, moderate and severe dementia [3].
Dementia has many causes. The 2024 Lancet Commission on dementia names strokes, Parkinson’s disease, HIV and syphilis as causes, and it discusses Alzheimer’s disease and Lewy body dementia [4]. Vascular dementia is usually tied to stroke [4]. About 57 million people worldwide were living with dementia in 2019, a number expected to reach 153 million by 2050 [4].
Where TBI fits
The commission counts TBI among 14 risk factors that people and societies can change or avoid [9]. Pooled studies found that people with a past TBI had about 1.66 times the dementia risk of people without one [4]. The commission concluded that TBI likely raises risk and may bring dementia on earlier [4]. It also lists CTE among the brain diseases that future scans and lab tests may help researchers tell apart [4].
A relative risk compares groups. It cannot tell you whether you yourself will develop dementia.
A brain injury can also change over the years. Two researchers argued in 2013 that TBI should be treated as a chronic health condition, noting that some people decline over time [10]. CDC figures on moderate and severe TBI come from people aged 16 or older who received inpatient rehabilitation. They were followed for five years after injury [11]. By then, 26% had improved and 22% stayed the same, while 30% had gotten worse and 22% had died [11].
CTE: a diagnosis made after death
Chronic traumatic encephalopathy, or CTE, is a pattern of brain damage seen when brain tissue is examined under a microscope. Its signature is a buildup of an abnormal form of a protein called tau inside nerve cells, gathered around small blood vessels [12]. In early stages, it shows up in patches deep in the folds of the brain’s surface [3].
Because it is defined by what tissue looks like, CTE can be confirmed only by examining the brain after death [3, 13]. The Amsterdam consensus calls these findings CTE neuropathologic change and states that this is not a clinical diagnosis [8]. The National Institutes of Health held its first consensus workshop on diagnosing CTE in Boston in 2015 [13]. The pathologists there agreed well on how to tell CTE apart from other diseases that involve tau [13]. CTE also differs from Alzheimer’s disease, in part because it lacks the amyloid protein that builds up in Alzheimer’s [12].
What is known about the cause
According to the NIH, CTE has so far been found only in people exposed to brain trauma, usually many times over [13]. American football players made up 73.4% of the published cases reviewed by the authors of the TES criteria [3]. In brain bank research those authors cite, each extra 2.6 years of football was tied to twice the odds of CTE [3].
What is not known
Researchers still do not know how common CTE is in the general population [3, 12]. They also cannot yet match the brain changes of CTE to specific symptoms or to a person’s future brain health [13]. Some people with CTE changes, especially early stage changes, may have no meaningful symptoms [3].
Traumatic encephalopathy syndrome: research criteria for living people
Because CTE cannot be confirmed in life, researchers needed a way to study people who might have it. In 2021, a panel of 20 clinician scientists, drawn from 11 academic centers, published NINDS criteria for traumatic encephalopathy syndrome, or TES [3]. The panel reached agreement through a structured process with four rounds of rating [3].
To meet the TES criteria, a person must have all of the following [3].
- Substantial exposure to repeated head impacts, such as from contact sports
- Problems with episodic memory (remembering events) or executive function (planning and organizing), or trouble controlling emotions and behavior
- A change from how the person used to function, with a course that gets worse over time
- Symptoms that other conditions do not fully explain
The criteria then rate how certain the link to CTE is, using four levels: suggestive, possible, probable and definite [3].
Three limits matter for readers. The authors say the criteria are meant mainly for research and should be used with caution in clinical care and in legal settings [3]. A TES diagnosis is not a CTE diagnosis [3]. And at this time, a single moderate to severe TBI does not meet the exposure requirement [3].
How TES differs from lasting concussion symptoms
Timing is one of the clearest differences. Lasting concussion symptoms start at the time of an injury. The TES criteria look for a change from a person’s usual level of functioning that follows a worsening course [3]. When symptoms are described as starting late, the criteria expect a clear stretch of stable functioning, lasting several years, before problems appear [3].
Exposure is the other big difference. Lasting concussion symptoms can follow one crash or one fall. TES requires substantial exposure to repeated head impacts, such as from contact sports [3].
Why memory problems alone cannot show CTE
Memory problems show up in every condition in this article. A concussion can affect thinking and remembering [1], many dementias affect memory. TES lists memory problems as a core feature [3]. That overlap is the main reason a memory problem cannot point to CTE by itself.
Other TES features overlap too. Trouble controlling mood and behavior is often seen in mental health conditions and in other brain diseases [3]. Brain imaging changes studied so far are not specific to CTE. The fluid markers researchers have studied are often raised in other brain diseases as well [5].
Research tools and clinical tests
No imaging test or fluid biomarker is approved for diagnosing CTE alone [5]. Tau PET, a scan that uses a tracer to light up tau protein, is being studied [5]. One widely used tracer still needs more testing before it could diagnose CTE in living people [5]. The TES authors judged that biomarkers were not yet ready to include in their criteria [3]. A clinic that claims to diagnose CTE with a scan today is going beyond the evidence in these sources [5, 3].
Why brain bank studies can mislead
Much of what is known about CTE comes from donated brains. Brain banks tend to include more older people and more people with dementia [12]. A bias toward contact sport athletes has also made it hard to judge how common CTE is [12]. The TES authors point out a further problem: brain bank studies often rely on clinical details collected after the person has died [3].
A widely cited 2017 study shows why this matters. Researchers examined the donated brains of 202 former American football players and found CTE in 177, including 110 of 111 who had played in the NFL [14]. The authors warned that players and families with symptoms may have been more likely to donate [14]. They said their brain bank does not represent all former players and cannot show how common CTE is [14].
The Amsterdam consensus reached a similar view. It found that CTE brain changes appear very uncommon in community samples and more common in brain banks of former professional athletes with heavy head impact exposure [8]. Those brain bank studies cannot show cause or measure risk [8]. The panel added that no one yet knows whether these brain changes cause specific symptoms or always get worse [8].
Comparison compiled by Safety Behind the Wheel Foundation
Four terms compared
| Term | What it is | How it is identified | What usually happens |
|---|---|---|---|
| Concussion | A mild TBI from a bump, blow or jolt | Symptoms and exam; a scan is not needed | Most people feel better in a couple of weeks |
| Persistent postconcussion symptoms | Concussion symptoms that last longer than usual | Symptoms and history after a concussion | Treated symptom by symptom, often in primary care |
| Dementia | Thinking decline that limits independence | Assessment of thinking and daily function | Depends on the cause |
| CTE | A pattern of tau buildup in brain tissue | Only by examining the brain after death | Link to symptoms not yet clear |
Sources: CDC [6, 1]; VA/DoD guideline summary [2]; Lancet Commission [4]; Katz et al. [3]; NINDS [13].
Common mix ups about repeated head impacts
A few other beliefs are worth checking against the evidence.
- Every former athlete with memory trouble has CTE. Researchers do not know how common CTE is. Memory problems have many causes [3].
- Brain bank numbers show how often CTE happens. Brain banks lean toward older people, people with dementia and contact sport athletes, so their numbers cannot be applied to everyone [12].
- CTE is just another name for Alzheimer’s disease. The two differ under the microscope, though a person can have both [12].
Protecting your brain from here
You cannot change past injuries, but you can lower the chance of new ones. Helmets on bikes and head protection in contact sports are both on the Lancet Commission’s list of recommendations [4]. It also calls for fewer high impact collisions in sport and no return to play right after a TBI [4]. On the road, buckle up on every trip.
If memory problems are affecting daily life, a full checkup can look for causes that can be treated. Use this checklist to prepare.
Checklist from Safety Behind the Wheel Foundation
- Write down when your symptoms started and whether they are improving, steady or getting worse.
- List every head injury you remember, from crashes, falls or sports.
- Note how many years you played contact sports, if any.
- List your medicines, sleep habits, mood and any pain.
- Bring someone who knows you well and has seen the changes.
- Ask whether your symptoms affect your safety to drive.
Get emergency care right away
Any of these CDC danger signs after a new head injury is a reason to dial 911 or go straight to an emergency department [1].
- A headache that gets steadily worse and will not go away
- Weakness, numbness, loss of coordination, convulsions or seizures
- Repeated vomiting
- Slurred speech or unusual behavior
- One pupil looking larger than the other one
- Failing to recognize familiar people or places, or acting confused, restless or agitated
- Passing out, seeming very drowsy, or being impossible to wake
Questions to ask your care team
Question checklist from Safety Behind the Wheel Foundation
- Do my symptoms fit a concussion that is still healing, or could something else be going on?
- What else could be affecting my memory, such as sleep, mood, pain or medicines?
- Would a short course of cognitive rehabilitation help me?
- How will we measure changes in my memory over time?
- Given my history of head impacts, is there anything specific I should watch for?
- Is there any test that can tell me whether I have CTE?
- Should I see a neurologist or a memory clinic?
- Is it safe for me to drive right now?
Frequently asked questions
Can a doctor test me for CTE while I am alive?
No. CTE can be confirmed only by examining the brain after death [3]. No scan or blood test is approved to diagnose it. Tau PET scans are still being studied [5].
Does one concussion from a car crash cause CTE?
So far, NIH reports that CTE has been found only in people exposed to brain trauma, usually many times [13]. Under the current TES research criteria, one moderate to severe TBI is not enough exposure to qualify [3]. A past TBI is linked with higher dementia risk on average, which is a separate question [4].
Is traumatic encephalopathy syndrome the same as CTE?
No. TES is a set of research criteria applied to living people with heavy exposure to repeated head impacts, while CTE is a finding in brain tissue after death [3]. The TES authors state plainly that a TES diagnosis is not a CTE diagnosis [3].
If my memory is still poor months later, does that mean I am getting dementia?
Not necessarily. Lasting symptoms after concussion are treated one symptom at a time. A short trial of cognitive rehabilitation is one option [2]. If your memory is getting worse over time, tell your care team so they can look for causes, which for dementia range from stroke to Parkinson’s disease [4].
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Concussion, lasting concussion symptoms, dementia and CTE share some symptoms, especially memory trouble. But they are different conditions with different outlooks. Most concussions improve within weeks, lasting symptoms can be treated, and dementia has many causes that a care team can look for.
CTE remains a diagnosis made after death. The research criteria for living people are meant mainly for studies [3]. If you are worried, bring your full injury history and a clear account of how your memory has changed to your next appointment.
Sources and further reading
- 1Centers for Disease Control and Prevention. Symptoms of mild TBI and concussion. Updated September 2025. cdc.gov/…/index.html
- 2American Speech-Language-Hearing Association. Evidence Maps summary: VA/DoD Clinical Practice Guideline for the Management and Rehabilitation of Post-acute Mild Traumatic Brain Injury, version 3.0. 2021. apps.asha.org/…/f28e156a-8117-ee11-8145-005…
- 3Katz DI, Bernick C, Dodick DW, et al. National Institute of Neurological Disorders and Stroke consensus diagnostic criteria for traumatic encephalopathy syndrome. Neurology. 2021;96(18):848-863. doi.org/10.1212/WNL.0000000000011850
- 4Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet. 2024;404:572-628. doi.org/10.1016/S0140-6736(2401296-0)
- 5Pierre K, Molina V, Shukla S, et al. Chronic traumatic encephalopathy: diagnostic updates and advances. AIMS Neuroscience. 2022;9(4):519-535. doi.org/10.3934/Neuroscience.2022030
- 6Centers for Disease Control and Prevention. About mild TBI and concussion. Updated September 2025. cdc.gov/…/index.html
- 7Centers for Disease Control and Prevention. Facts about TBI. Updated August 2025. cdc.gov/…/index.html
- 8Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport, Amsterdam, October 2022. British Journal of Sports Medicine. 2023;57(11):695-711. bjsm.bmj.com/content/57/11/695
- 9The Lancet. Nearly half of dementia cases could be prevented or delayed by tackling 14 risk factors starting in childhood (news release, EurekAlert). July 31, 2024. eurekalert.org/news-releases/1052982
- 10Corrigan JD, Hammond FM. Traumatic brain injury as a chronic health condition. Archives of Physical Medicine and Rehabilitation. 2013;94(6):1199-1201. doi:10.1016/j.apmr.2013.01.023. Abstract via Model Systems Knowledge Translation Center. msktc.org/…/traumatic-brain-injury-chro…
- 11Centers for Disease Control and Prevention. About moderate and severe TBI. Updated May 2024. cdc.gov/…/moderate-severe-tbi.html
- 12National Institute of Neurological Disorders and Stroke. The neuropathological diagnosis of chronic traumatic encephalopathy (CTE): next steps. Meeting summary. 2019. ninds.nih.gov/…/2019%20NINDS%20CTE%20Meetin…
- 13National Institute of Neurological Disorders and Stroke. NIH chronic traumatic encephalopathy diagnosis conference. Reviewed July 2022. ninds.nih.gov/…/nih-chronic-traumatic-encep…
- 14Mez J, Daneshvar DH, Kiernan PT, et al. Clinicopathological evaluation of chronic traumatic encephalopathy in players of American football. JAMA. 2017;318(4):360-370. pmc.ncbi.nlm.nih.gov/articles/PMC5807097
This article reflects the safety priorities of brain injury education and road safety. It is meant as general education, not medical advice, and it cannot diagnose any condition. Research on CTE and dementia is changing, so check official sources such as NIH and the CDC, and talk with your own care team about your symptoms. Reviewed October 2026.
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