Chronic traumatic encephalopathy (CTE) is the term used to describe brain degeneration likely caused by repeated head traumas. CTE is a diagnosis made only at autopsy by studying sections of the brain.

CTE is a rare disorder that is not yet well understood. CTE is not related to the immediate consequences of a late-life episode of head trauma. CTE has a complex relationship with head traumas such as persistent post-concussive symptoms and second impact syndrome that occur earlier in life.

Experts are still trying to understand how repeated head traumas — including how many head injuries and the severity of those injuries — and other factors might contribute to the changes in the brain that result in CTE.

CTE has been found in the brains of people who played football and other contact sports, including boxing. It may also occur in military personnel who were exposed to explosive blasts. Some signs and symptoms of CTE are thought to include difficulties with thinking (cognition) and emotions, physical problems and other behaviors. It's thought that these develop years to decades after head trauma occurs.

CTE cannot be made as a diagnosis during life except in those rare individuals with high-risk exposures. Researchers do not yet know the frequency of CTE in the population and do not understand the causes. There is no cure for CTE. Researchers are currently developing diagnostic biomarkers for CTE, but none has been validated yet.

There are no specific symptoms that have been clearly linked to CTE. Some of the possible signs and symptoms of CTE can occur in many other conditions. In the few people with proved CTE, signs and symptoms have included cognitive, behavioral, mood and motor changes.

Cognitive impairment

• Difficulty thinking (cognitive impairment)
• Memory loss
• Problems with planning, organization and carrying out tasks (executive function)

Behavioral changes

• Impulsive behavior
• Aggression

Mood disorders

• Depression or apathy
• Emotional instability
• Substance misuse
• Suicidal thoughts or behavior

Motor symptoms

• Parkinsonism
• Motor neuron disease

CTE symptoms don't develop right after a head injury, but experts believe that they might develop over years or decades after repeated head trauma. Experts currently believe that CTE symptoms appear in two forms. In early life between the late 20s and early 30s, the first form of CTE may cause mental health and behavioral issues including depression, anxiety, impulsivity and aggression. The second form of CTE is thought to cause symptoms later in life, around age 60. These signs and symptoms include memory and thinking problems that are likely to progress to dementia.

The full list of signs to look for in people with CTE at autopsy is still unknown. It is unclear what kind of symptoms, if any, CTE may cause during life. Little is known right now about how CTE progresses.

When to see a doctor

CTE is thought to develop over many years after repeated brain injuries that may be mild or severe. However, see your doctor in case of the following:

• Suicidal thoughts. Research shows that people with CTE may be at increased risk of suicide. If you have thoughts of hurting yourself, call 911, your local emergency number or the National Suicide Prevention Lifeline at 800-273-TALK (800-273-8255).
• Head injury. See your doctor if you've had a head injury, even if you didn't need emergency care. If your child has received a head injury that concerns you, call your child's doctor immediately. Depending on the signs and symptoms, your doctor may recommend seeking immediate medical care.
• Memory problems. See your doctor if you have concerns about your memory or other thinking (cognitive) or behavior problems.
• Personality or mood changes. See your doctor if depression, anxiety, aggression or impulsivity occur.

Repetitive head trauma is likely the cause of CTE. Football and ice hockey players, as well as military personnel serving in war zones, have been the focus of most CTE studies, though other sports and factors such as physical abuse also can lead to repetitive head injuries.

However, not all athletes and not everyone who experiences repeated concussions, including military personnel, go on to develop CTE. Some studies have shown no increased incidence of CTE in people exposed to repeated head injuries.

In brains with CTE, researchers have found that there is a buildup of a protein called tau around the blood vessels. Tau buildup in CTE is different from accumulations of tau found in Alzheimer's disease and other forms of dementia. CTE is thought to cause areas of the brain to waste away (atrophy). Injuries to the sections of nerve cells that conduct electrical impulses affect communication between cells.

It's possible that people with CTE may show signs of another neurodegenerative disease, including Alzheimer's disease, amyotrophic lateral sclerosis (ALS) — also known as Lou Gehrig's disease — Parkinson's disease or frontotemporal lobar degeneration (frontotemporal dementia).

Repeated exposure to traumatic brain injury is thought to increase the risk of CTE, but experts are still learning about the risk factors.

There is no treatment for CTE. But CTE may be prevented because it is associated with recurrent concussions. Individuals who have had one concussion are more likely to have another head injury. The current recommendation to prevent CTE is to reduce mild traumatic brain injuries and prevent additional injury after a concussion.

There is currently no way to diagnose CTE. It can only be suspected in people who are at high risk due to repeated head trauma over the course of years during their sports or military experiences. A diagnosis requires evidence of degeneration of brain tissue and deposits of tau and other proteins in the brain that can be seen only upon inspection after death (autopsy).

Some researchers are actively trying to find a test for CTE that can be used while people are alive. Others continue to study the brains of deceased individuals who may have had CTE, such as football players.

The hope is to eventually use a range of neuropsychological tests, brain imaging such as specialized MRI tests and biomarkers to diagnose CTE. In particular, imaging of amyloid and tau proteins will aid in diagnosis.

PET scans

A positron emission tomography (PET) scan uses a low-level radioactive tracer that is injected into a vein. Then, a scanner tracks the tracer's flow through the brain. Researchers are actively working to develop PET markers to detect tau abnormalities associated with neurodegenerative disease in people who are living.

Researchers are also working to develop tracers that target and bind to tau buildup and other proteins on PET scans. Studies are underway using these types of scans and tracers to look for tau buildup in the brains of retired athletes who experienced head injuries. These PET scans are in the research phase and not available for clinical testing.

Other tests

There's been little research on plasma or cerebral spinal fluid to diagnose the long-term disease processes of CTE. Some biomarkers that are used in Alzheimer's disease research may be useful for CTE because the conditions are similar. These biomarkers would need to identify brain degeneration from CTE separately from the original brain trauma.

CTE is a progressive, degenerative brain disease for which there is no treatment. More research on treatments is needed, but the current approach is to prevent head injury. It's also important to stay informed about the latest recommendations for detecting and managing traumatic brain injury.

You'll probably start by seeing your family doctor, who may refer you to a neurologist, psychiatrist, neuropsychologist or other specialist for further evaluation.

Because appointments can be brief and there's often a lot to discuss, prepare before your appointment.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance. Ask if you need to fast for blood tests.
• Write down any symptoms, including any that may seem unrelated to the reason for scheduling the appointment. Your doctor will want to know details about your concern for your mental function. Try to remember when you first started to suspect that something might be wrong. If you think your difficulties are getting worse, be ready to explain why, and be prepared to discuss specific examples.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, vitamins or supplements that you're taking.
• Make a list of your other medical conditions, including those you are currently being treated for, such as diabetes or heart disease, and those you've had in the past, such as strokes.
• Take a family member, friend or caregiver along, if possible. Sometimes it can be difficult to recall all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.

Preparing a list of questions will help make the most of your time with the doctor. Prioritize questions from most important to least important. Some basic questions to ask the doctor include:

• What is likely causing symptoms?
• Are there other possible causes for symptoms?
• What kinds of tests are needed?
• Is my condition likely temporary or chronic? How will it likely progress over time?
• What's the best course of action?
• What are the alternatives to the primary approach being suggested?
• I have other medical issues. How can they be managed together?
• Are there any clinical trials of experimental treatments I should consider?
• Are there any restrictions?
• If medication is being prescribed, is there a potential interaction with other medications I am taking?
• Are there any brochures or other printed material that I can take home with me? What websites do you recommend?
• Do I need to see a specialist? What will that cost, and will my insurance cover it? You may need to call your insurance provider for some of these answers.

If you've had a concussion, some basic questions to ask your doctor include:

• What is the risk of future concussions?
• When will it be safe to return to competitive sports?
• When will it be safe to resume vigorous exercise?
• Is it safe to return to school or work?
• Is it safe to drive a car or operate power equipment?

Don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor

The doctor may ask you a variety of questions.

Questions related to symptoms:

• What symptoms are you experiencing? Any trouble with word use, memory, focus, personality or directions?
• When did symptoms begin?
• Are symptoms steadily worsening, or are they sometimes better and sometimes worse?
• How severe are symptoms?
• Have you stopped doing certain activities, such as managing finances or shopping, because of difficulty thinking through them?
• What, if anything, seems to improve or worsen symptoms?
• Have you noticed any changes in the way you tend to react to people or events?
• Do you have more energy than usual, less than usual or about the same?
• Have you noticed any trembling or trouble walking?

Questions related to health history:

• Have you had your hearing and vision tested recently?
• Is there a family history of dementia or other neurological disease such as Alzheimer's, ALS or Parkinson's disease?
• What medications are you taking? Are you taking any vitamins or supplements?
• Do you drink alcohol? How much?
• What other medical conditions are you being treated for?

If you've had a concussion, your doctor may ask questions related to events surrounding the injury:

• Have you had any previous head injuries?
• Do you play contact sports?
• How did you get this injury?
• What symptoms did you experience immediately after the injury?
• Do you remember what happened right before and after the injury?
• Did you lose consciousness after the injury?
• Did you have seizures?

Questions related to physical signs and symptoms:

• Have you experienced nausea or vomiting since the injury?
• Have you been experiencing headaches? How soon after the injury did the headaches start?
• Have you noticed any difficulty with physical coordination since the injury?
• Have you noticed any sensitivity or problems with your vision and hearing?
• Have you noticed changes in your sense of smell or taste?
• How is your appetite?
• Have you felt lethargic or easily fatigued since the injury?
• Are you having trouble sleeping or waking from sleep?
• Do you have any dizziness or vertigo?

Questions related to cognitive or emotional signs and symptoms:

• Have you had any problems with memory or concentration since the injury?
• Have you had any mood changes, including irritability, anxiety or depression?
• Have you had any thoughts about hurting yourself or others?
• Have you noticed or have others commented that your personality has changed?
• What other signs or symptoms are you concerned about?