One of the main symptoms people struggle with after sustaining a concussion is neurofatigue or brain fog. This is the feeling you get when even after a good night’s sleep, you can’t muster up the energy to tackle the day like you used to. Some days even the simplest tasks seem overwhelming and can leave you feeling drained.
Neurofatigue is one of the most common complaints in people with persistent concussion symptoms. Your brain will have less energy. Even after a little effort, you may feel worn out and unable to continue. Your brain is telling you that you need a rest, and you might wonder why?
When you sustain a concussion, the brain movement within the skull causes an over-activation of the neurons. There is an initial excitation phase that uses more energy in the brain. After this the brain gets to a minimum of energy stores at approximately five days post-injury. Following a concussion, the brain’s mitochondria (the powerhouses of the cell) become dysfunctional, and there is an increased demand for ATP (the body’s energy).
Sure, being tired is expected at first, and it makes sense! In the acute stage of concussion, the initial energy deficit in the brain causes us to feel tired and more sleepy than usual.
Overall, neuro-fatigue following a concussion results from a combination of brain dysfunction, neurochemical changes, metabolic stress, and psychological factors. These processes may overlap and interact, making it difficult to pinpoint a single cause. But it’s when this fatigue persists beyond the initial couple of weeks, or even months, that we start to wonder… why am I still so tired? Well, there may be a reason for this fatigue:
1. Brain Energy Disruption
- Metabolic Changes: A concussion disrupts the brain’s normal energy metabolism. After the injury, there is an increased demand for energy in neurons, which is not always met. This energy imbalance, especially in the brain’s neurons, may lead to fatigue.
- Cerebral Blood Flow: Concussions can impair blood flow regulation to the brain, affecting its oxygen and nutrient supply. This can lead to overall brain fatigue as it becomes harder to meet the metabolic demands of brain tissue.
2. Neurochemical Imbalances
- Neurotransmitter Disruption: Concussions often affect the levels of key neurotransmitters (such as serotonin, dopamine, and glutamate), which are crucial for regulating mood, cognition, and energy. An imbalance in neurotransmitters can contribute to feelings of mental fatigue and cognitive difficulties.
- Ion Imbalance: The concussion-induced disruption in neuronal membrane integrity leads to abnormal ion flux, which requires the brain to expend more energy to maintain homeostasis, contributing to fatigue.
3. Inflammatory Response
- Neuroinflammation: After a concussion, inflammation occurs in the brain as part of the body’s healing process. This inflammation can affect neuronal function, leading to cognitive deficits and tiredness. Inflammatory molecules can alter brain function and contribute to persistent fatigue.
4. Disrupted Sleep Patterns
- Sleep Disruptions: Concussions can interfere with sleep patterns, causing insomnia or disturbed sleep. Poor or insufficient sleep significantly worsens neuro-fatigue, as the brain does not get the necessary rest it needs to recover.
- Circadian Rhythm Disruption: The concussion may affect the body’s natural circadian rhythm, leading to increased feelings of tiredness and disorientation during the day.
5. Disruption of Neural Networks
- Brain Connectivity Changes: Concussions can impair communication between different brain networks. This disruption in neural networks leads to cognitive difficulties and reduced processing speed, which can cause feelings of mental exhaustion.
Brain Networks
Two main “brain networks” work opposite one another, and there is a switch to move between each. The first is called the Default Mode Network. It is essentially our self-talk. These are our random thoughts throughout the day when we aren’t actively engaged in a task. It allows us to think about past events or speculate about future events.
The second is called the Executive Network. This kicks in when we focus on planning, problem-solving, and decision-making tasks. The switch between these two networks is the Salience Network, the controller between the Default Mode Network and the Executive Network. When this controller is not working appropriately, both networks may work simultaneously, causing energy to be wasted and mental fatigue.
When we activate the Executive Network (our task-oriented network), our Default Mode Network (the background self-talk) shuts down; or at least it’s supposed to. Similar to the autonomic nervous system, the sympathetic and parasympathetic branches work opposite each other.
Persistent Concussion Symptoms
Researchers have found that some people with persistent concussion symptoms fail to shut down their Default Mode Network when performing a task. Functional MRI images of these people show that both networks (Executive and Default) are active at the same time, a problem termed Default Mode Interference.
The Default Mode creeps up when trying to concentrate and perform a specific task. This can lead to distraction, inattentiveness, and ultimately poor performance. When both networks are active simultaneously, they burn twice the energy. Ultimately, you burn more energy with minimal cognitive activity, also known as, you guessed it… neurofatigue.
Default Mode Interference is not only limited to people with concussions. It has also been found in patients struggling with chronic pain, post-traumatic stress disorder (PTSD), generalized anxiety disorder and depression.
Good Old Days Bias
One factor that can lead you to believe you have reduced cognitive ability post-concussion is the “Good Old Days Bias.” This bias occurs when you view your mental capacity, memory and concentration as flawless, even though it may not have been.
For example, you may report that you always remembered your keys and wallet and never lost any train of thought. However, you likely had some average memory lapse but never paid attention to this.
This bias can warp your perception of your past abilities. This gives you the impression that the concussion is the cause of reduced memory, attention and focus.
Treatment
Calming your internal dialogue (the Default Mode Network) can improve your ability to use the Executive Network. This can be achieved through techniques like meditation and mindfulness.
Psychological interventions, such as cognitive behavioural therapy (CBT), can effectively teach strategies to shut down the default mode network and improve task performance.
Conclusion
A comprehensive approach is needed to manage neurocognitive fatigue. Increasing positive self-talk, mindfulness, and meditation can improve cognitive performance post-concussion. This will reduce the amount of mental energy you are using and reserve it for the cognitive tasks you need to do.
References
- van der Horn HJ, Liemburg EJ, Scheenen ME, de Koning ME, Spikman JM, van der Naalt J. Post-concussive complaints after mild traumatic brain injury associated with altered brain networks during working memory performance. Brain Imaging Behav. 2016;10(4):1243-1253. doi:10.1007/s11682-015-9489-y
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