brain health · Mar 26, 2025

Understanding the 4 Stages of Chronic Traumatic Encephalopathy

doctor looking at mri scan results next to head injury patient in wheelchair

By Liad Stearns, MS

Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease linked to the cumulative effects of repeated head trauma over time. When scientists first identified CTE in boxers in the 1920s, they referred to it as “punch drunk syndrome” — a term historically used to describe symptoms such as memory loss, unsteady gait, and speech difficulties resulting from repeated blows to the head [1].

What makes CTE so devastating is the way it progresses over time. What begins as mild cognitive impairment and subtle mood and behavioral changes will eventually lead to severe dementia and loss of independence. While there is no cure, taking preventative steps early on can significantly improve symptom management and quality of life. In this article, we’ll explore the four stages of CTE, its symptoms, diagnostic challenges, and emerging strategies to slow disease progression and enhance brain health for those affected.

What Causes Chronic Traumatic Encephalopathy?

CTE is associated with repeated traumatic brain injuries (TBIs), including concussions and subconcussions (symptomless brain injuries). Every impact to your head increases your risk of developing CTE, even if you don’t notice any immediate side effects. This is because head injuries damage the cells and blood vessels in your brain,, leading to microscopic hemorrhages (microbleeds), disrupted neuronal connections, and neuroinflammation.

Over time, your brain’s tau proteins — which help transport nutrients and signaling molecules within your nerve cells — become hyperphosphorylated and misfold into toxic clumps, called neurofibrillary tangles. These abnormal tangles disrupt communication between neurons, trigger inflammation, and ultimately lead to cell death and brain atrophy [2]. Researchers have observed this process primarily in the frontal and temporal lobes of the brain, regions responsible for everyday cognitive, emotional, and motor functioning. Tau tangles are notably seen in other neurological disorders, the most well-established being Alzheimer’s disease.

CTE most commonly affects athletes participating in contact and collision sports such as football, boxing, hockey, and rugby, as well as military personnel who experience blast-related injuries. Since the accumulation of tau tangles leads to cognitive decline and emotional disturbances over time, it’s crucial to take proactive measures to identify and manage the symptoms of CTE if you fall into one of these high-risk groups.

What Are the Symptoms of CTE?

The symptoms of CTE often emerge years — or even decades — after the initial injuries and progressively worsen over time [3, 7]. While they tend to appear in a patient’s 60s or 70s, they may appear earlier than that, during midlife [8].

Early symptoms

Cognitive impairments: Mild memory loss, confusion, difficulty concentrating, headaches, and dizziness.
Behavioral changes: Impulsive or erratic behavior, and impaired judgment.
Mood disorders: Depression, anxiety, aggression, and mood swings.

Advanced symptoms

Severe cognitive decline: Significant memory loss and progressive dementia.
Motor dysfunction: Lack of coordination, tremors, difficulty walking, speech difficulties.

The 4 Stages of CTE

CTE progression is categorized into four stages, each marked by the increasing severity of cognitive, emotional, and motor impairment.

Stage I

Stage I of CTE involves mild symptoms that often go unnoticed or are mistaken for normal aging or stress. Individuals may experience headaches, difficulty with attention and concentration, and early signs of short-term memory loss. Mood swings, mild depression, anxiety, and some impulsivity or aggression may also occur.

Symptoms are usually subtle and don’t interfere with daily functioning at this stage. Individuals often maintain their normal routines, although some executive function issues and emotional changes may emerge [4].

Stage II

Stage II of CTE is characterized by moderate symptoms, with more significant changes in mood and behavior. Individuals may experience increased depression, irritability, and short-term memory loss. Impulse control issues including reckless behavior and aggression may become more evident, in addition to more severe dizziness and headaches [4]. A smaller portion of individuals may experience issues with language and suicidal thoughts during this stage.

In Stage II, symptoms become more evident and disruptive to daily life. Behavioral changes may be mistaken for psychiatric disorders like depression or bipolar disorder, as the symptoms become more disruptive and challenging to ignore.

Stage III

Stage III of CTE is marked by advanced cognitive decline and notable personality changes. Individuals exhibit significant memory loss, confusion, and increased difficulty with attention and concentration. Symptoms like aggression, impulsivity, and depression intensify, while motor issues including tremors, lack of coordination, and speech difficulties emerge.

Daily life becomes increasingly difficult in this stage as individuals may begin to show little or no motivation to engage in normal activities. The risk of self-harm rises due to the worsening mood and cognitive decline.

Stage IV

The final stage of CTE is characterized by severe cognitive decline and memory loss, often progressing to advanced-stage dementia. Symptoms in this stage include severe difficulty with attention and concentration, intense paranoia, aggression, depression, and difficulties with gait and spatial awareness. Executive function, language skills, and motor control are all significantly impaired. Some individuals may develop Parkinsonian symptoms that affect their physical movement, impairing their ability to walk [4].

At this stage, individuals are no longer able to care for themselves and often require full-time care. The disease is typically fatal at this stage, often due to complications like infections, falls, or malnutrition.

How Is CTE Diagnosed?

A diagnosis of CTE requires evidence of brain tissue degeneration and the accumulation of tau proteins, which can only be definitively confirmed with an autopsy after death. In a living person, imaging techniques including Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) are being explored to investigate the associated markers. MRI is used to detect structural changes in the brain linked to head trauma, including brain atrophy in the frontal and temporal lobes, white matter damage, and cerebral microbleeds. PET scans, particularly those using specific tau protein tracers, are under investigation as an experimental method to identify the accumulation of tau protein tangles. PET scans are also used to assess glucose metabolism, as they can detect areas of decreased activity that typically indicate neurodegeneration.

Scientists are working to identify biomarkers — such as blood tests, cerebrospinal fluid (CSF) analysis, and more advanced imaging techniques — to detect CTE in living patients. Until such tools become reliable, CTE diagnosis remains based on clinical symptom patterns, with confirmation requiring post-mortem brain analysis.

How Do You Treat CTE?

Treating CTE is focused on managing symptoms and improving quality of life, as there is no definitive cure. A combination of therapy, lifestyle modifications, medication, and supplementation can be used to address and minimize the cognitive, emotional, and physical challenges associated with the condition.

Symptom management

Counseling and therapy: Cognitive behavioral therapy (CBT) and counseling can assist in managing mood disorders, depression, anxiety, and impulse control.
Medications: Commonly prescribed medications include antidepressants, antipsychotics, mood stabilizers, sleep aids, and anti-anxiety medications.
Speech therapy: Speech and language rehabilitation strategies are used to improve articulation, language processing, and verbal expression.
Memory exercises: Techniques including mnemonic devices, mindfulness and attention training, and cognitive programs are used to improve memory recall, enhance focus and awareness, and improve cognitive flexibility.

Lifestyle strategies

Nutrition: Whole foods rich in antioxidants, omega-3 fatty acids, healthy fats, and anti-inflammatory compounds can help support brain health. A study published in Frontiers in Aging Neuroscience highlighted that the Mediterranean diet, which includes high amounts of fruits, vegetables, fish, and healthy fats, is linked to improved cognitive function and a reduced risk of dementia [9].
Sleep: Quality and consistent sleep supports the brain’s waste-clearance system, reduces neuroinflammation, supports memory and cognitive function, and regulates mood and emotional health. Prioritize 7–9 hours of quality sleep per night and practice stress management techniques such as mindfulness, meditation, or deep breathing exercises to protect your brain.
Exercise: Regular aerobic exercise and strength training stimulate the production of brain-derived neurotrophic factor (BDNF) — a key protein that supports neuronal growth and synaptic plasticity — which enhances learning, memory, and cognitive resilience. Aim for at least 150 minutes of moderate aerobic activity per week, such as brisk walking, cycling, or swimming, to support brain function and neurogenesis.
Stress management: Mindfulness, meditation, and relaxation techniques help lower cortisol levels, decrease neuroinflammation, and strengthen emotional resilience. A study published in Nature Reviews Neuroscience found that chronic stress impairs neurogenesis and contributes to cognitive decline, while adequate sleep enhances brain plasticity and memory retention [10].
Supplementation: Nouro by Tonum is a promising supplement formulated to support memory and cognitive function. In studies conducted alongside Duke University, Nouro has been demonstrated to increase BDNF, prevent brain shrinkage, and lower glial fibrillary acidic protein (a biomarker for brain injury and neuroinflammation) in mice [5, 6].

While these approaches can help slow symptom progression and improve daily functioning, ongoing research is needed to develop targeted treatments for CTE. Managing the condition is best done through a comprehensive, multidisciplinary approach that adapts to individual needs.

Takeaways

CTE is a neurodegenerative disease caused by repeated head trauma, with symptoms progressively worsening through four stages.
Although there is no cure for the disease, symptom management through cognitive behavioral therapy, speech therapy, medication, and memory exercises has been shown effective in addressing the related mood disorders, improving communication, and enhancing cognitive function.
Nutrition and exercise play a crucial role in supporting brain health. A diet rich in antioxidants, omega-3 fatty acids, and healthy fats, combined with regular exercise, increases BDNF production, reduces inflammation, and improves cognitive function, learning, and memory. Taking clinically researched supplements such as Nouro can also be effective in addition to a brain-healthy diet.
Quality sleep and active stress reduction techniques are important to support memory functions and the brain’s waste-clearance systems, as well as strengthen emotional resilience.
Prevention is important. Reducing head injuries through improved safety measures in sports and military settings is essential for preventing CTE.
Further research is needed to identify diagnostic criteria for CTE in living patients, allowing for earlier detection and more effective, targeted treatments.

References

Liad Stearns, MS is a freelance health and science writer based in San Francisco, CA. She holds a master’s degree in neuroscience from Tulane University and has experience in product development within the glucose monitoring space, as well as working as a health coach in a functional medicine practice.