A concussion is a transient, functional disturbance that temporarily alters the way our brains work. The majority of concussed individuals (80-90%) have no symptoms within 7-10 days after injury (McCrory et al, 2013). Nevertheless, 10-15% of concussed individuals will experience symptoms longer than 10 days. The international classification of diseases (ICD-10) classifies post-concussion syndrome (PCS) as at least 3 symptoms present 4 weeks after injury. The symptoms listed in the ICD-10 are dizziness, fatigue, irritability, sleep/memory problems, emotional disturbance and difficulty concentrating. One of the objective measures healthcare providers use to elevate an individual with PCS is the post-concussion symptom scale (PCCS). PCCS consists of 22 symptoms. It is comprised of the most commonly seen symptoms seen in PCS individuals. The PCCS consists of somatic (headache), emotional (sadness) and cognitive (difficulty concentrating) symptoms. The goal of this post is to explain some of the proposed reasons for the correlation between concussions and difficulty concentrating.
Neck Pain, Whiplash, Concussions and Difficulty Concentrating
One of the proposed theories for post-concussion syndrome is chronic irritation from the muscles and joints of the neck. Broglio SP et al., 2011 found that 96.1 G’s of linear acceleration are required to cause a concussion. Whereas, only 4 G’s are required to cause a whiplash injury. It has been estimated that 15% of the symptoms experienced by individuals with post-concussion syndrome are attributed to the neck. Fakhran et al., 2016 showed a relationship between the muscles of the back of the neck (suboccipitals) and headaches experienced in PCS individuals. It should be no surprise that If an individual has neck pain or a headache than their ability to concentrate will be affected.
Visual Dysfunction after Concussions and Difficulty Concentrating
Another potential cause of concentration difficulties in PCS individuals is visual disturbance. Tractioning of the axons during a concussion causes functional disturbances in the nerves. These disturbances in the nerves can affect the muscles they supply. This includes the muscles of the eyes (oculomotor dysfunction). Cifu et al., 2014 were able to distinguish between PCS patients and a control population based on skipping (saccadic) eye movements. Patients with saccadic eye movements have difficulty with following an object in a smooth movement (smooth pursuit). Patients often complain of pressure around the eye and headaches when reading. This saccadic movement and corresponding pressure makes it difficult for PCS individuals to concentrate.
Psychological Impairments with Concussions and Difficulty Concentrating
Another proposed theory for post-concussion syndrome is psychological impairments. We have three modes when it comes to processing information: a default mode network (DMN), executive network (EN) and a salience network (SN). DMN refers to an individual’s internal dialogue (internally directed state). The DMN is responsible for thoughts about one’s self, upcoming events, mind wandering and past experiences. The EN is responsible for focusing on the task at hand (externally directed state). EN is also responsible for controlling your working memory, attention, and decision-making. The SN is responsible for actively switches between the DMN and EN (Van Der Horn et al., 2015).
Normally your brain uses the DMN when its idle and switches to the EN when there is a task or demand. Research has shown that a concussion, long-term stress and anxiety disrupt this balance and the DMN becomes hyperactive, suppressing the EN. Suppression of the EN leads to mental fatigue and poor cognitive performance. Typically patients express that they have a hard time focusing and feel like they’re in a fog or day dreaming. There has also been some research to suggest a connection between a hyper-active DMN and visual/noise sensitivity. Sensitivity to noise and sensitivity to sound are 2 of the symptoms on the PCSS.
Involvement of the Thalamus after Concussions and Difficulty Concentrating
DMN and thalamus: Some research has shown that there is a connection between the thalamus (deep brain structure) being hyper-active and over activation of the DMN. The thalamus becomes hyper-active as a result of changes to the nerve (axon) stretching after a concussion. Research has shown with very sensitive MRI’s (DTI) that nerve (axon) function normalizes after 30 days. Normalization of the axon at 30 days is important because it corresponds with NAA and energy levels in the brain, Giza et al., 2014.
Conclusion of Concussions and Difficulty Concentrating
Therefore, if a PCS individual is having persistent difficulty concentrating past 30 days it could be a result of anxiety, long term stress. lack of education in regards to an individuals condition can cause stress and anxiety leading to a hyper-active DMN. It could also be that you just haven’t trained the brain to switch off the DMN. There is emerging evidence that different cognitive activities and games are effective at shutting off the DMN.
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