There are many injury risks in football, but concussions are often the most discussed. While concussion risk in football is slightly higher than other contact sports, knowing concussion signs and symptoms can help protect players.

A simple concussion prevention strategy is concussion education for players, parents, and coaches. Concussion education must include the signs and symptoms, long-term consequences, and risks of playing with an untreated concussion. Proper concussion education in these groups can improve player disclosure of concussion symptoms. The quick removal from play and appropriate management not only improves outcomes but prevents further, catastrophic injuries.

This article will focus on the early signs and symptoms of a concussion along with the possible brain networks affected with specific symptoms. This information may seem unnecessary, but making these connections can improve understanding to better protect children and adolescents playing football.

Early Concussion Signs and Symptoms

Autonomic Symptoms

Cervical Symptoms

Migraine Symptoms

Emotional Symptoms

Cognitive Symptoms

Vestibular Symptoms

Ocular Symptoms

Early Concussion Signs and Symptoms

The initial signs and symptoms of concussions are due to direct forces to the brain.¹ When there is contact to the body or head leading to head rotation, the force causes the brain to slosh within the skull. The outer surface of the brain will hit against the hard skull causing blunt trauma. The rotation of the brain on top of the brainstem and spinal cord will produce shearing stress. This results in many possible signs and symptoms, with or without loss of consciousness.¹

It should be noted that signs are cues or actions that others recognize with the concussed individual, whereas symptoms are what the individual feels. Sometimes these can overlap as irritability can be a feeling but also seen over-reactivity. Below are possible symptoms that occur with a concussion:

• Visual disturbances (seeing stars)
• Headache
• Photophobia (sensitivity to light)
• Phonophobia (sensitivity to sound)
• Nausea
• Dizziness
• Neck pain
• Brain fog
• Mood disturbances
• Irritability
• Amnesia (memory loss)

Here are possible signs that an individual has sustained a concussion:

• Balance impairment
• Eye tracking abnormalities
• Slowed reaction time
• Abnormal speech or decreased response time
• Acting different from usual self

Some of these signs and symptoms may be due to the initial stunning of brain cells and decreased blood flow. These can resolve quickly within minutes to hours as the brain works to improve blood flow and nutrient delivery to the cells. However, some neurons and axons are physically damaged, so more repair is necessary, and these symptoms take longer to resolve.

At the same time, some symptoms may not be initially present and develop as secondary injuries from inflammation. These may go away within weeks as the inflammation decreases. Overall, the symptoms that occur in a concussion can evolve and may persist long-term in post-concussion syndrome.

The symptoms of a concussion can be categorized into the following types: autonomic, cervical, migraine, emotional, cognitive, vestibular, and ocular. These represent different networks in the brain with some overlapping symptoms in each category.

Autonomic Symptoms

Autonomic involvement is common with concussions.² Symptoms could be lightheadedness, exercise intolerance, lightheaded/dizziness, elevated heart rate, headache, fatigue, nausea, and brain fog. The general term for these symptoms is dysautonomia—literally, dysfunction of the autonomic nervous system. The autonomic nervous system is split into the sympathetic (‘fight or flight’) and parasympathetic (‘rest and digest’) nervous systems. It involves many brain areas.

The brainstem, located in the midline between the big brain and spinal cord, is vital to autonomic functions. It includes the ascending reticular activating system (ARAS), which sends axons up to the cerebrum (big brain) for alertness and motivation. Damage here along with the frontal lobe itself can cause fatigue and brain fog. At the same time, the brainstem is important in sleep, so disturbance to the brainstem can result in sleep problems like difficulty falling or staying asleep and overall sleep quality.

The brainstem and cerebellum (little brain at base of skull) also contain networks involving cardiovascular and vestibular function. Dysfunction can cause exercise intolerance, lightheadedness or dizziness, nausea, and headaches. It may even result in an abnormally elevated heart rate at rest or when standing from a lying or seated position.

For instance, postural orthostatic tachycardia syndrome (POTS) can result from a concussion.² It is characterized by a resting heart rate above 120 beats per minute (bpm) along with an increase in 30 bpm from lying to standing for adults (over 40 bpm for children/adolescents).³

Additionally, disruption to the vagus nerve (or its connections within the brainstem) can cause gastrointestinal symptoms like nausea, vomiting, diarrhea, constipation, and bloating. It may cause alterations in the gut microbiome resulting in dysbiosis and irritable bowel syndrome.

Cervical (Neck) Symptoms

A cervical or neck component can contribute to concussion symptoms.⁴ This could lead to neck stiffness, headaches, lightheadedness, dizziness, or balance problems.

Direct damage to the neck region can occur in a whiplash-type injury. The presence of both concussion and whiplash disorder are common and likely underestimated due to similarities in symptoms.⁵ Pain can occur due to directly activating pain receptors in muscles, joints, or nerves. Also, damage to the muscles and joints can lead to abnormal proprioception (muscle and joint sense) leading to lightheadedness and neck stiffness.⁴

At the same time, areas in the central nervous system that receive proprioception from the neck could be disrupted. This causes poor integration of information resulting in the same symptoms. Many areas in the brain could be involved including the cerebellum.

There is also the possibility of a spinal cord concussion. Rather than being in the brain, direct trauma and axonal shearing with inflammation occurs in the spinal cord.⁶ This would affect the neurons and axons in the area leading to similar symptoms along with possible issues in the arms and legs.

Migraine Symptoms

Migraine is another category that involves symptoms common with typical primary migraines. These include throbbing one-sided headache, dizziness, nausea, light and sound sensitivity, and possibly a visual aura/disturbance.

There are many different types of migraines with a variety of symptoms. Some do not even include head pain. How migraines occur is still debated, but the following is relatively accepted.

Migraines start with a slow spreading of depolarization (activation) of neurons in the cerebral cortex (big brain).⁷ The activation is followed by inhibition of these brain cells but activation of the trigeminal system in the brainstem that controls the vasculature. This causes an increase in vasodilation (opening of blood vessels) on the side of activation leading to increased blood flow resulting in the throbbing pain.

Areas involved in controlling vasculature, autonomics, and the visual system are affected in migraines. For instance, the midbrain is a central area for the sympathetic nervous system and reflex responses to light and sound. Dysfunction can contribute to the cortical spreading, vascular abnormalities, and decreased to increased blood flow present in migraines. This area also contributes to light and sound sensitivity.

The midbrain commonly contributes to concussion symptoms as it is within the midline at the top of the brainstem—ideal spot for axon shearing.

Emotional Symptoms

Emotional symptoms and mood disorders can also be present after a concussion.⁸ These are anxiety, depression, emotional instability, irritability, nervousness, and personality changes. Specific brain area dysfunction along with general neuroinflammation⁹ can result in these symptoms.

The limbic system, which is an evolutionarily conserved network deep in the brain, is involved in emotions and memory. For instance, the hypothalamus is the master regulator of neuroendocrine function within the limbic system. Dysfunction here can lead to changes in hormones like thyroid hormone involved in metabolism, sex hormones like testosterone and estrogen, cortisol involved in the stress response, and oxytocin involved in love and happiness.

Other areas are the hippocampus involved in memory and learning and amygdala involved in fear responses. Both may be implicated in conditions like post-traumatic stress disorder (PTSD). Additionally, the frontal lobe and cerebellum may be affected, which are important in response inhibition (having a filter) and coordinating emotions.

Along with brain-related changes and neuroinflammation, most adolescents with concussions also have poor experiential and social changes due to symptoms or inability to attend school or sport.¹⁰ These can greatly affect their overall mood and cause emotional symptoms. Identification and education of these social components are important in individualized management.

Cognitive Symptoms

Cognitive problems may be the most common symptom category following a concussion.¹¹ Symptoms include brain fog, poor concentration, attention deficit, slowed thinking, difficulty remembering, and poor school or work performance. Children may even get a diagnosis of attention deficit hyperactivity disorder (ADHD) following a concussion or TBI.

Dysfunction in the frontal lobe, just below the forehead, can cause these symptoms due to its role in attention, planning, organizing, and executive functioning. The frontal lobe also has connections to other brain regions; therefore, dysfunction in these regions or long connecting tracts can cause cognitive problems.

Brainstem dysfunction resulting in autonomic and vestibular issues can also cause cognitive symptoms. For instance, dysautonomia can cause decreased blood flow to the frontal lobe and other brain regions when one is trying to focus.¹² Without proper blood flow, there is a lack of nutrients like glucose and oxygen, which are needed to maintain proper neuronal function.

Additionally, the vestibular system is important for automatic movements and head awareness. Hence, vestibular dysfunction can cause the nervous system to be inefficient leading to cognitive issues.

Vestibular Symptoms

Vestibular symptoms are due to problems with the balance and equilibrium system. Classic vestibular symptoms like dizziness, vertigo, nausea, balance problems, motion sensitivity either visually or in a car, and headaches are common following a head injury.¹³

They may be due to dysfunction in the peripheral vestibular system like the fluid-filled canals and other sensors in the inner ear. With a concussion, the vestibular neurons and their connections in the brainstem, cerebellum, and higher centers in the brain are more frequently affected.

The vestibular sense is arguably the most important sense because it sets the foundation for every other sense to work from. It provides one’s sense of gravity and head in space to help map one’s body and surroundings.

For this reason, the vestibular system is involved in the autonomic nervous system,¹⁴ cognition and memory,¹⁵ and can contribute to anxiety and depression.¹⁶ Hence, the vestibular system and its connections are very important to understand, assess, and treat following a concussion.

Ocular Symptoms

The ocular symptoms deal with the eyes, vision, and eye movements following a concussion. These symptoms are eye strain, double/blurred vision, light sensitivity, difficulty reading, poor school/work performance, and headaches.¹⁷

The eyes are direct extensions from the center of the brain. Their connections are widely spread throughout the brain to integrate light and vision with the other senses.

Then, eye movements are essential to align the fovea in the proper direction to see clearly. Eye movements occur through the coordination of six small muscles on each eye, and they can be reflexive or voluntary and slow or fast. Many brain regions control eye movements like the brainstem, cerebellum, basal ganglia, and all lobes of the big brain.¹⁸

For this reason, observing the eyes is an important diagnostic tool in assessing proper brain function.¹⁷ Hence, the eyes are considered the windows into viewing the brain.

Summary

Every concussion is different and will present different signs and symptoms. Awareness of all the possibilities is important to best identify a concussion. Players, parents, and coaches all have a role in concussion identification. This hastens removal from play and necessary concussion management.

There are many similarities among symptoms and brain regions within the categories. Because the brain works in networks, damage to one area can affect other regions leading to overlap of symptoms.

Headache is one of the most common symptom and can affect up to 86% of individuals.¹⁹ The other more common symptoms are confusion, dizziness, imbalance, nausea, and difficulty concentrating. Because these may not be present in everyone, it is important to look for other signs and symptoms as well.

Overall, concussion signs and symptoms must be understood by all groups to better protect football players!

References

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