Right now, there is no definitive way to confirm CTE in a living person. Chronic traumatic encephalopathy can only be diagnosed with certainty after death, when brain tissue is examined under a microscope for a specific pattern of abnormal protein buildup. But that doesn’t mean you’re stuck with zero answers. Clinicians can evaluate your symptoms, history, and brain function to determine whether you likely have what’s now called Traumatic Encephalopathy Syndrome (TES), which is the clinical term for probable CTE in someone who is still alive.
What Doctors Actually Look For
A set of diagnostic criteria called Traumatic Encephalopathy Syndrome was developed to capture the clinical picture of CTE. To meet the criteria, you need all four of the following: a substantial history of repetitive head impacts, cognitive impairment in memory or executive function (or behavioral and emotional dysregulation), a progressive worsening of symptoms over time, and no other condition that better explains what’s happening.
That last point is important. Doctors have to rule out Alzheimer’s disease, frontotemporal dementia, depression, substance abuse, sleep disorders, and other conditions that can cause overlapping symptoms. CTE doesn’t have a single telltale sign that separates it from everything else, which is why the diagnostic process involves multiple types of evaluation.
Symptoms That Raise Concern
CTE symptoms tend to fall into three categories: cognitive, behavioral, and motor. The cognitive changes typically involve difficulty with judgment, reasoning, problem solving, and memory. The behavioral changes are often what people notice first. Impulsivity, aggression, emotional volatility, and depression are common. Motor symptoms, including balance problems and difficulty with coordination, can develop as the disease progresses.
One of the most distinguishing features of CTE is when those symptoms appear. They generally show up in a person’s 40s, sometimes earlier, often years or even decades after the person stopped playing contact sports or experiencing head impacts. This is different from Alzheimer’s, which typically surfaces in the 60s and starts primarily with memory loss. CTE more commonly begins with changes in judgment, impulse control, and emotional regulation before memory problems become prominent.
It’s also different from post-concussion syndrome. Post-concussion symptoms start right after a specific concussive event and can linger for months or longer. CTE, by contrast, doesn’t trace back to one hit. It emerges insidiously after a latent period with no obvious trigger, which is part of what makes it so unsettling for people trying to figure out what’s wrong.
How Exposure History Factors In
Your history of head impacts is central to any CTE evaluation. A 2019 study of 266 deceased former football players found that for every year of playing tackle football, a person’s risk of developing CTE increased by 30 percent. The risk doubled for roughly every 2.6 years of play. Players who participated for fewer than 4.5 years were 10 times less likely to have CTE than those who played longer, while those with careers exceeding 14.5 years were 10 times more likely to have it.
Among players who did develop CTE, the severity of symptoms doubled for every additional 5.3 years of football played. This isn’t limited to football. Boxing, hockey, soccer, rugby, and military service with blast exposure all carry risk. The key factor isn’t necessarily concussions you remember. It’s the cumulative total of repetitive head impacts, including the hundreds or thousands of subconcussive hits that never caused obvious symptoms at the time.
What a Clinical Evaluation Involves
If you bring these concerns to a specialist, the workup will likely involve several components. A neurological examination checks balance, eye movements, coordination, and mental status. Neuropsychological testing is more detailed: you’ll complete tasks that measure memory (recalling word lists or stories after a delay), executive function (problem solving, mental flexibility, impulse control), attention, and processing speed. Some evaluations also include tests of your sense of smell, since impaired odor identification has been linked to the type of brain damage seen in CTE.
Brain imaging plays a supporting role. MRI scans can reveal brain shrinkage or structural abnormalities but can’t confirm CTE on their own. More specialized imaging techniques can detect signs of prior damage, including evidence of tiny bleeds from past impacts or changes in how well different brain regions connect to each other. PET scans that use tracers sensitive to abnormal protein buildup are the most promising imaging tool. In research settings, these scans have been able to distinguish patterns of brain pathology in people with histories of repetitive head trauma from those of healthy controls and from people with Alzheimer’s. The scans can identify increased protein signals in deep brain structures like the amygdala and midbrain, areas that align with where CTE pathology concentrates. But this type of PET imaging is not yet available as a standard clinical diagnostic tool.
Why Confirmation Still Requires Autopsy
The defining feature of CTE is a very specific pattern: abnormal, heavily modified tau protein accumulating around small blood vessels and in the folds of the brain’s outer surface. This pattern is distinct from Alzheimer’s and other neurodegenerative diseases, but it can only be seen by examining brain tissue under a microscope. Research from Boston University’s CTE Center, which has studied the largest brain bank of former contact sport athletes, found CTE in 345 of 376 former NFL players examined, a rate of 91.7 percent. That figure reflects a donated brain bank, so it skews toward people who had symptoms, but it underscores how common the disease is among those with extensive exposure.
Blood-based biomarkers that could detect signs of brain degeneration are in development, but they face a fundamental limitation: they can signal that something neurodegenerative is happening without revealing where in the brain or what specific disease is responsible. Brain imaging biomarkers are considered more informative because they show the geographic pattern of damage, which is what distinguishes CTE from other conditions.
What You Can Do Right Now
If you have a history of contact sports or repetitive head impacts and you’re noticing progressive changes in your thinking, mood, or behavior, the most practical step is a comprehensive neurological and neuropsychological evaluation. This won’t give you a definitive CTE diagnosis, but it can document your cognitive baseline, track whether symptoms are worsening over time, and rule out treatable conditions like depression, sleep apnea, or thyroid disorders that can mimic CTE symptoms.
Tracking progression matters because it’s a core diagnostic criterion. If your symptoms are stable rather than worsening, CTE becomes less likely as an explanation. Keeping a record of when symptoms started, how they’ve changed, and how they affect your daily functioning gives clinicians far more to work with than a single snapshot evaluation. Some specialty clinics affiliated with major research centers also offer enrollment in longitudinal studies, which provide ongoing monitoring and access to the latest diagnostic tools as they become available.