Concussions and Chronic Traumatic Encephalopathy (CTE)

An initial impact. The force from the impact causes your brain to strike against the inner surface of the skull and then rebound against the opposite side. The brain shifts and twists from the force. The brain swells over time and severe injury and damage result. These events all cause quick deceleration of the head and shifting of delicate brain tissue inside the skull. Rarely does an accident of this nature occur in a true-on or forward/backward direction. There is typically a rotational force, as would occur in one were struck on the right or the left side of the forehead. If the body is traveling forward or facing forward in a still position, and a force occurs off-center, the brain sustains a rotational sheer force, which causes more trauma to brain structures and therefore a more severe concussion.

A loss of consciousness and nausea at the time of the injury are normal signs that a rotational injury has occurred. Nerve signals in the brain of a person that has suffered a concussion are normally disrupted for at least 30 days after the injury. If one returns to the activity too soon, the likelihood of having another concussion goes up significantly. This is due to the reaction time and brain processing not operating normally. Post-concussion injured people are less likely to see a ball coming toward their heads during this vulnerable period. If more than one concussion occurs, the symptoms are typically worse and recovery time is increased.

The trauma to the brain caused by a concussion can result in abnormal vestibular system functioning, and the brain can receive abnormal signals regarding the position and movement of the head in space. When vestibular information is inaccurate, the brain most often relies on visual input to stabilize the head on the body. This means that the visual system becomes the most reliable system to quickly assess one’s position in space and remain balanced. Relying upon vision alone as the primary source of balance often leads to fatigue and difficulty performing routine daily activities.

Reliance on the visual system for balance can result in eye strain and tension headaches. If the vestibular system is delivering inaccurate information to the brain about the head’s position in space, the brain must rely on visual input and joint sensors to feel the body in space. Failure to effectively compensate with the use of visual references and being aware of the surface on which one is sitting or standing results in dizziness and a sense of instability.

Dizziness encourages a person to refrain from moving the head and leads to neck stiffness and headaches. The presence of a whiplash associated with the concussion further complicates the diagnosis and suddenly symptoms limit the ability to participate in life activities. Why do some people have few to no symptoms, some people develop symptoms over time, and others feel they cannot function after a concussion?

It can be normal to have no symptoms after a concussive event. In studies of athletes, almost all subjects are free of all symptoms by three days after the injury, while brain studies still show reduced nerve signal transmission and risk of injury for up to 30 days. Other people feel normal for two to three weeks, then have a steady increase in headaches, dizziness, or fatigue that at times are not recognized as being caused by the concussion. Fewer people have immediate and more severe concussive symptoms that last for prolonged time frames.

We now know some responses to concussions can be influenced by genetics. People who have a history of dementia or Alzheimer’s disease in their family can be more at risk for having a worse response after a concussion. This is because some people have proteins (Tau) in the brain that already place them at a risk for memory problems, which can be aggravated by concussion. This results in more cognitive difficulties with memory, concentration, and motivation after a concussion.  We will discuss the presence of (Tau) proteins further in-depth as the article goes on.

Due to the forces involved in concussion, it is very common to sustain a whiplash injury that is often not diagnosed with the concussion. As the head decelerates or receives the force of an incoming object, the neck muscles are strained. The effects of whiplash injury are not always immediate and can appear two to three weeks later with an increasing number of tension headaches and visual disturbances. Dizziness can also occur related to neck strain. This delayed increase in symptoms can interfere greatly with school and work performance.

Finally, many people have previous conditions that make the brain’s response to concussions more problematic. A prior history of migraine headaches can lead to complex migraines after experiencing a concussion. At times migraines can occur without a headache and produce only an aura that feels like vertigo and dizziness lasting for multiple hours or days. Failure to recognize and treat migraines activity can lead to prolonged symptoms and places more stress on the brain, limiting recovery.

A history of visual disturbances or childhood sensory processing issues affects one’s response to concussion. For example, if a person had difficulty with distance vision or depth perception before the injury, the brain adjusted to that problem. After the injury, the way in which the brain compensated for the visual problem may not work as well, and the ability to focus on static objects or follow moving objects may cause symptoms of dizziness, as well as integration problems and a history of motion sickness is present, a concussion can again cause increased difficulty for the brain to process vestibular information.

The concussion injury itself is “invisible”, as headache, dizziness, head fog, eye strain, and fatigue are rarely perceived by others. Thus, the disruption of the brain’s ability to process sensory input can result in extreme fatigue, frustration, and emotional instability. In children, this manifests itself as tantrums and outbursts. Highly visual activities overwhelm the brain, so crowded environments (work, school, stores, public events) can cause elevation of symptoms or anxiety.

Work and school performance can suffer as concentration and memory are affected. Adjusting visual focus from near and far can cause dizziness and headache. In schools, looking from the desk at PowerPoint presentations or to boards in front of the classroom is extremely challenging. Children and adults alike report difficulty remembering information and concentrating with reduced accuracy in work performance. Students have trouble completing homework and adults arrive home from work with extreme fatigue and a lack of energy to engage in family and household activities.

A complex visual environment elevates symptoms of headache, head pressure, dizziness, and imbalance, and can cause anxiety. Over time people tend to withdraw from outings and can become depressed from the inability to perform routine daily activities. Crowded places are difficult to navigate because of the movement of people and the complex visual background in the observer’s peripheral vision. These visual distractions cause a sense of imbalance and dizziness, often with head pressure, which can lead to panic attacks or avoidance of activity.

A concussion just doesn’t stop there. Prolonged years of repeat concussions can lead to even more severe problems. Chronic traumatic encephalopathy (CTE) affects people who are often involved in activities such as contact sports, military veterans, and MMA fighters/boxers. The repeated trauma from multiple head injuries and concussions seems to be the driving physiological mechanism that ultimately leads to CTE. The idea of chronic traumatic encephalopathy was thought to be a new idea, but this is not the case.

The actual findings of this disease date back to around the 1920s and 1930s. Researchers then discovered that professional fighters seemed to be slower on cognitive examination. This led to the term “punch drunk.” Often used to describe boxers during the time. In the 2000s it was discovered that many if not hundreds of former professional football players were displaying unique physiological findings postmortem on neurological examination. The detections and discovery of tau (pTau) and other amyloid proteins showed up in almost all brain dissections of these former football players. Correlating these findings with other findings when the players were alive has eventually led to the current status of CTE.

Findings when the players were alive were obtained and cross-referenced with a postmortem questionnaire of relatives found that all the players at some point had suffered multiple head trauma and concussions during their playing days in the league. The findings were: 1) mood changes 2) decreased cognitive awareness 3) increased aggression and anger 4) motor and sensory disease symptoms. Risk factors to develop CTE seem to be repeated head trauma exposure, the severity of the nature of the activity, lower age of the first occurrence, decrease cognition reserves, cerebrovascular health, and genetics all play a role in CTE development.

At this time, CTE and the neurodegenerative damage that it does can only be diagnosed via post-mortem. But, we do know that the acute consequences of mTBI lead to concussions, sub concussions, which lead to axonal injury, microvascular disruption, a further breach of the blood-brain barrier, neuroinflammation, and eventually deposits of tau (pTAU) into the brain matter.

In conclusion, there are a few takeaways. The best way to prevent subsequent concussions is to allow full recovery from any injury before resuming activities that are risky.  Full recovery means there are no symptoms with any activity, whether academic, work-related, leisure activities, or sports. Use any recommended safety equipment, ensure all coaches are fully trained in concussion avoidance, identification and treatment, and know your personal concussion history. Stop participating in sports or leisure activities if there is any indication of potential injury to the head or neck and seek medical attention.