What is a Concussion or Traumatic Brain Injury (TBI)?

A concussion is a type of traumatic brain injury (TBI) that occurs when the head experiences a sudden impact or jolt. This impact can cause the brain to move around inside the skull, leading to changes in brain function.

Concussions are caused by sudden acceleration/deceleration impacts to the head, neck, or body that are transmitted into the brain. This rapid change of direction of the brain inside the skull cavity causes overstretching of the brain cells, or neurons, and impedes their ability to communicate with one another properly. The overstretching leads to the opening of channels within the cells and turns the cells into a state of overexcitement.

This diffuse axonal injury to the brain cells causes the cells to send signals rapidly and randomly, depleting the energy stores within the brain and leaving the brain in an energy-deprived state, which is the source of many of the symptoms that occur after a mild TBI.

What are the Most Common Concussion Symptoms?

Many different symptoms can occur after sustaining a concussion, and they are generally broken down into 4 main categories: physical, cognitive, emotional, and sleep. Every concussion is unique, so there are no two concussions that are going to present the exact same in terms of what symptoms are experienced, the intensity of the symptoms, how long the symptoms take to develop, and how long until they resolve. Depending on the symptom, it may be present immediately following the traumatic brain injury, such as dizziness or feeling in a fog, and some will develop in the coming hours to days (within 48 hours). Therefore, it is essential to both keep track of what symptoms you are experiencing day to day and to get assessed by a qualified healthcare practitioner so they can determine if the symptoms you are experiencing are related to your concussion and help you with strategies about how to resolve them.

Physical Symptoms.

Woman suffering from physical concussion symptoms such as headache

Here are some of the most common concussion symptoms and how they may present:


Headache is the most common symptom that is experienced after a head injury, with 91% of patients experiencing this symptom. The reason headaches are very common after concussions is also why they can be hard to diagnose and treat: there are many causes and types of headaches. Common causes of post-traumatic headache include pain coming from the muscles or joints in the head or neck, changes in the function of the brain cells, changes in your brain’s ability to modulate pain, and activation of various nerves during the injury (1). It may be helpful to create a headache journal to keep a more accurate history of the headache triggers, which will aid your healthcare provider in a more accurate diagnosis of your specific type of headache.

Neck pain

Neck pain is a common symptom after a concussion due to the force that is required to cause a traumatic brain injury. It only takes 5Gs of force to cause whiplash, but can take up to 60-160Gs of force to cause a concussion. Therefore, by definition, every individual who has sustained a concussion has also sustained some level of whiplash injury and should be assessed for it with an in-depth physical examination. Furthermore, cervical spine dysfunction, characterized by pain and impaired function, can worsen other symptoms of concussion, such as headaches, dizziness, and nausea.

Sensitivity to light and noise

Due to the mechanism of concussion and the subsequent brain energy deficit, brain structures can become very sensitive to various stimuli in the recovery process, which commonly include bright light and loud sounds. Sensitivity to light is found in 43% of all concussion patients and is usually the worst in the first 1-3 weeks post-concussion (2). One analogy that can be used is thinking of the brain as a radio that has lost the ability to control the volume. Normally, your brain can turn down the volume on bright lights and loud sounds, but it is currently busy trying to recuperate from the injury and can be sensitive to intense stimuli during that time. That doesn’t mean that we should completely limit all exposure to light and sound during the recovery process, but it can be useful to use some strategies to buffer these symptoms, such as sunglasses outdoors, ear plugs in overwhelming environments, etc.

woman suffering from such post-concussion symptoms as light and noise sensitivity

Visual problems

Visual issues after a traumatic brain injury are extremely common and can have a detrimental effect on a patient’s ability to carry out their normal activities of daily living. Research has shown that as high as 69% of patients have some sort of visual dysfunction after head injuries (3). Visual dysfunction can include many symptoms but commonly includes one or more: double vision, blurred vision, decreased visual attention, abnormal pupillary dilation, and increased eye tracking movements.

To properly diagnose and treat the cause of the visual dysfunction, you should be assessed by a trained healthcare provider. It has been found that up to 40% of patients have a symptomatic visual (convergence) dysfunction that lasts longer than 1 month after their traumatic injury (4). Common triggers for visual disturbances include reading, driving, texting, and other complex eye movement tasks.

Dizziness and balance issues

Dizziness is second only to headache in terms of the most frequently reported symptom after traumatic brain injury. (5) Similar to headache, dizziness is a rather ill-defined symptom. It can be due to a variety of conditions. Still, the most common causes of post-concussion dizziness (PCD) include central vestibular disorders, Benign Paroxysmal Positional Vertigo (BPPV), Labyrinthine dehiscence/perilymph fistula syndrome, labyrinthine concussion, and temporal bone fractures.

Most cases of PCD, upwards of an estimated 85–90% will resolve in the first 3 weeks after injury without treatment. However, if dizziness lasts longer than 10 days, an assessment for BPPV or other vestibular system dysfunctions should be conducted to see if you would benefit from vestibular rehabilitation therapy.

Nausea and/ or vomiting

After a traumatic brain injury, nausea and vomiting can be BOTH a typical symptom of a concussion and also something that may be more worrisome if they are prolonged. Repeated vomiting following an impact is a red flag symptom and an indication to call an ambulance/go to the ER. Nausea can be caused by various conditions, each of which should be assessed during the intake process, as the specific treatment will be determined by the aggravating factors for your patient’s symptoms. Common symptoms that may be associated with nausea post-concussion include headache, dizziness, autonomic dysfunction, fatigue, etc.

Cognitive symptoms.

Cognitive changes are a very common symptom of post-traumatic brain injury but are understandably some of the most worrying to patients. The good news is, like other concussion symptoms, the majority of patients will have a resolution of their cognitive symptoms in the 3 months following their traumatic brain injury.

The most common cognitive symptoms that are experienced by patients include:

  • Memory issues
  • Difficulty concentrating
  • Confusion
  • Feeling slowed down
  • Feeling “in a fog”
  • Trouble thinking clearly

These symptoms can be very frustrating for patients with head injuries as they will affect many of their activities of daily living, including their ability to go to work or school. Areas that may be affected include attention/concentration, ability to process and understand information, memory, communication, planning, problem-solving, and decision-making. If you are struggling with cognitive symptoms affecting your daily activities, seeking medical care to determine the cause and severity of your symptoms will help determine the correct treatment course for your specific condition. This can include learning how to plan and prioritize your day so as not to overwhelm your brain and a variety of rehabilitation exercises that can help to retrain these specific brain areas. 

Emotional symptoms.

Difficulty regulating emotions or an increased intensity of emotions are both common TBI symptoms. Along with the other TBI symptoms that have already been discussed, emotional symptoms are multifactorial, and each individual will have unique symptoms and challenges. It is estimated that between 7% and 34% of people who experience a concussion will have some level of emotional dysregulation, with symptoms being more prominent and lasting longer in adolescents (6). Generally, these symptoms do not persist longer than 1-2 weeks, with only a minority of patients continuing to experience symptoms past one year.

Some common emotional symptoms include:

  • Anxiety
  • Nervousness
  • Depression
  • Sadness
  • Irritability
  • Unusual mood swings
  • More emotional

There is currently a lack of consensus on whether the increased emotional dysregulation is caused directly by the traumatic brain injury itself, is a secondary consequence of frustration and uncertainty involved with interruption of regular activities such as sports and school, or if there is some sort of pre-existing vulnerability in a subset of people that sustain a concussion. Regardless, if you are struggling with emotional problems after your concussion, you do not need to struggle on your own, and many concussion-literate mental health professionals can help you get back to feeling yourself again.

Sleep problems.

alarm clock illustrating a post-concussion symptom that makes it difficult to get up in the morning

Sleep disturbance is common following traumatic brain injury (TBI), affecting 30–70% of individuals, many occurring after mild injuries. Insomnia, fatigue, and sleepiness are the most frequent post-TBI sleep complaints. It is actually more common to experience trouble falling asleep after a mild TBI compared to more severe brain injuries (7)

Some common sleep-related concussion symptoms include:

  • Fatigue
  • Low energy
  • Sleeping more or less than normal
  • Difficulty falling asleep

Why is sleep affected after a head injury?

It is hypothesized that sleep is affected after a head injury because of functional changes in the brain regions responsible for the sleep-wake cycle. If there is a decrease in function in the wakefulness areas, you will experience an increase in sleep. If there are changes in the area that initiates sleep, you will experience insomnia. If there are alterations in the area that controls circadian rhythm, you can experience both insomnia and sleeping more than usual.

In addition, depression, anxiety, and pain are common TBI comorbidities with substantial influence on sleep quality, so they may also be playing a role in your energy levels or sleep-wake cycle.

Are there any symptoms that cause a longer recovery?

woman experiencing headache as one of her long-term concussion symptoms

The recovery from traumatic brain injury (TBI) can vary widely from person to person and is going to be unique to the person who has sustained the head injury. TBI symptoms vary depending on a variety of factors. Still, the research has suggested that a subset of characteristics may lead to a prolonged recovery, although the findings are generally mixed.

In a 2020 paper by Schilling et al. (8), 36.8% of diagnosed concussions experienced prolonged recovery, which was defined as symptom duration longer than 28 days. Children who took longer to recover were more likely to be female, be aged 16-18 years, have a prior history of concussion, and have a learning disorder (ADD, ADHD, etc).

Symptoms that increased recovery time included memory loss either before or after the concussion or immediate neck pain at the time of the injury. Patients with prolonged recovery also experienced more symptoms and more severe symptoms during their recovery, specifically more vestibular, ocular, and cognitive symptoms, and were more likely to have experienced anxiety about their concussion.

Further studies have also suggested that pre-existing mental health conditions may also delay recovery in some people (9).

Recently, there has also been research that suggests another large driver of prolonged recovery is the time to see a medical professional. Patients assessed by a healthcare provider within seven days of their injury recovered on average 20 days faster than patients who waited 14 days or longer. Therefore, seeing a trained medical professional such as those in the Complete Concussions clinical network is a great first step in preventing acute concussions from becoming chronic conditions. (10)

When do traumatic brain injuries become an emergency?

In the majority of cases, traumatic brain injuries do not require emergency medical care. They can be effectively treated through healthcare providers who have been trained in concussion-based rehabilitation, but there are some signs and symptoms that you should be aware of that are signs of more severe injuries.

If you are experiencing any of the following symptoms, please seek immediate medical attention for further testing, as it may point towards a more significant traumatic brain injury that requires medical evaluation and treatment. 

Signs and symptoms, including severe headaches, seizures, focal neurologic deficits, loss of consciousness, deterioration of mental status, and worsening symptoms, may indicate a more severe head injury and require immediate medical attention. These symptoms should be monitored for the first 48 hours after an injury. 

list of red flags that indicate a concussion or a traumatic brain injury (tbi)

Sport Concussion Assessment Tool 6 (SCAT6)British Journal of Sports Medicine 2023;57:622-631.

Severe or worsening headaches

Headache is the most common symptom following a concussion and can have a significant impact on your ability to carry out your daily activities. However, severe headaches and headaches that are progressively getting worse over time can be a sign that there is something more serious going on, such as a bleed occurring inside the skull that is putting pressure on your brain. You should seek immediate medical evaluation if your headache is severe, progressively worsening, and constant. This is also why it is recommended that you do not take pain medication in the first 48 hours following a concussion, as you do not want to risk masking a headache that may be a sign of a more severe or life-threatening condition. 

Focal neurologic deficits

Other signs that a more severe condition may develop are neurological deficits such as numbness, tingling, muscle weakness, slurring speech, balance and coordination problems, etc. These symptoms are characteristic of neurological disorders that go beyond the functional injury of a “normal” concussion. Progressive changes in vision, such as worsening double or blurry vision, are also signs of a neurological deficit and should be assessed.


Any person who presents with a seizure after a head injury needs to seek medical attention. It occurs in 2-17% of all head injuries and is more common in children (11). Signs of a seizure include uncontrollable shaking of the head, body, or limbs, altered levels of consciousness, decreased mental function, vacant staring, or becoming unresponsive. This was recently seen in a head injury that NFL quarterback Tua Tagovailoa sustained while on the field. 

Extreme drowsiness or inability to wake up

Extreme drowsiness, the inability to wake up, or any other minimally conscious state is a red flag sign that there are alterations in the brain’s ability to maintain consciousness. Increased sleep requirement is a common symptom of head injuries. Still, you should not have difficulty staying awake or being awoken or roused when you are sleeping.

Repeated vomiting

Vomiting is another symptom that is common after a concussion but should not be continuous. It is more common in children than in adults to have vomiting after a traumatic brain injury (TBI), but you should not be vomiting multiple times in the same hour or day. If there is repetitive vomiting, it is another sign that there may be a more moderate or severe TBI present, and you should seek medical attention.

Loss of consciousness 

Loss of consciousness is more rare than people think when it comes to traumatic brain injuries, with <10% of all traumatic brain injuries resulting in a loss of consciousness. More recent publications have suggested that any loss of consciousness following a head injury (even for a brief period) or having lost consciousness since the impact (in the hours or days to follow), can be a sign of something more serious and should get evaluated.

Severe neck pain

Although rare, fracture or dislocation of the cervical spine may present alongside a traumatic brain injury (TBI), depending on the mechanism of injury. It is more common in “high-risk” injuries such as falling from a height or a high-speed motor vehicle accident. Signs that there may be underlying damage to the bones of the neck include being unable to rotate your neck 45 degrees to either side, tenderness of the bones of the neck, or being in one of the “high-risk” injury categories.

Signs of skull fracture

Skull fractures require immediate medical treatment, so any signs of skull fracture must be investigated. Signs include severe swelling or indentation of the skull, clear fluid or blood running from the nose or ears, and/ or bruising around the eyes (raccoon eyes). While skull fractures are fairly rare in sports-related concussions, in one study, they did account for 5.3% of emergency department patients after a sports-related head injury. They should be carefully monitored in high-risk sports where the participant isn’t wearing a helmet (skateboarding, rugby, etc.).

In children, there are a few additional signs that can be used to assess traumatic brain injury severity. Signs of a severe TBI in children include:

  • Any signs and symptoms listed in the Emergency Signs & Symptoms of a Concussion list.
  • If a child will not stop crying and cannot be consoled.
  • If an infant or small child will not nurse or eat.


In conclusion, traumatic brain injuries can cause a variety of symptoms, and the symptom profile is going to be unique for every person. The most common symptoms of a mild TBI are broken into 4 main categories: physical, cognitive, emotional, and sleep. For the majority of patients with a mild concussion, symptoms will tend to peak within the first week after sustaining a concussion and will improve with brain healing. However, it is essential to know what the “red flag” symptoms are after a traumatic brain injury (TBI) as it may point towards a more severe TBI, which would require immediate medical attention. If you are ever unsure if your symptoms are “normal”, or if you need help managing your symptoms and supporting your recovery, you can use the Concussion Tracker app or the Clinic Finder Tool at https://clinics.completeconcussions.com to find a certified clinic in your area that can guide you along your path to recovery.

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