Concussion – Causes, Signs and symptoms


Also called: Cerebral Concussion, Brain Concussion, Head Concussion


A concussion is a type of head injury caused by a heavy blow to or violent shake of the head. It occurs when the brain is shifted from its usual position and comes into contact with the hard bones of the skull. Concussions are often mild, although they can sometimes cause more severe brain damage.

Concussions are a common injury among children and adolescents, especially those who participate in contact sports. Concussion is also a common injury sustained during accidents involving vehicles. Although it may not always be possible to avoid concussion, the risk of sustaining a concussion can be reduced by wearing protective head gear while playing sports and taking necessary safety precautions while on the road, as a driver, passenger or pedestrian.

The most common symptoms of concussion include:

  • Headache
  • Short-term confusion
  • Dizziness or lightheadedness
  • Nausea
  • Feelings of irritability or lethargy
  • Blurred vision
  • Ringing in the ears (tinnitus)
  • Memory loss

These symptoms usually go away after a short period of time. However, in some cases, the symptoms of concussion become more severe. This may be an indication of a more serious brain injury. People who have a head injury and experience any of the following symptoms should call emergency medical services as soon as possible:

  • Increasing sleepiness or confusion
  • Persistent vomiting
  • Paralysis of one or more limbs
  • Inability to speak coherently
  • Lack of coordination
  • Clear fluid (cerebrospinal fluid) draining from nose or mouth

In diagnosing a concussion, physicians will conduct a medical history and a physical examination. A physician may ask about the circumstances of the injury and questions designed to assess the patient’s level of consciousness. Physicians may also use imaging tests to assess the extent of a head injury. Imaging tests, such as x-rays, computed axial tomography (CAT) scans and magnetic resonance imaging (MRI), can help physicians to identify any damage that may have been sustained to the skull or brain.

The most effective treatment for a concussion is rest because the brain needs time to recover after an injury. Some people may experience the mild symptoms of concussion for several months. This is called postconcussive syndrome. Postconcussive syndrome is not usually an indication of severe brain injury, although it can be distressing and disruptive for the patient.

About concussion

A concussion is a type of head injury caused by a sharp blow to the head by a blunt object. Concussions are one of the most common types of closed head injury, which means that the bones of the skull remain intact and there is no visible damage to the head (as opposed to an open head injury where the interior of the head is exposed). A concussion can also occur when the head is moved violently such as in whiplash or shaken baby syndrome. There are more than 1 million cases of concussion each year in the United States, according to the National Institutes of Health (NIH).

The brain is protected by the thick bones of the skull and a layer of tissue called the meninges, which surrounds and cushions the brain and spinal cord. If the head is hit with sufficient force, the brain can move inside the skull and come into contact with hard bone. Depending on the force of the impact, this can result in mild to severe disturbance in brain function.

Concussion can result in a loss of consciousness for a short period of time. However, not all cases of concussion involve a loss of consciousness. Sometimes the patient develops a headache and feels dizzy, disoriented and nauseated. Concussion, or the injury that produced the concussion, can result in other injuries to the head and brain. These may include:

  • Skull fracture – break or crack in the skull
  • Contusion – bruising of the brain
  • Diffuse axonal injury – damage to the nerve cells in the brain
  • Hematoma – bleeding in the brain

Some people experience amnesia (loss of memory) following a concussion and may not be able to remember the events immediately before or after the concussion. Most times, this is temporary. However, in some cases, these memories may never be recovered.

Concussion is common in children and adolescents, because they are more likely to experience head injuries from falls and accidents. Children and adolescents are also more likely to sustain injuries while playing sports such as football, basketball and baseball. People who play contact sports are especially at risk for a potentially fatal condition called second impact syndrome. This condition sometimes occurs when the brain sustains a series of minor concussions within a short space of time, causing the entire brain to swell. Second impact syndrome can lead to permanent brain damage and, in some cases, death. Therefore, it is important that people who have a concussion, no matter how mild, refrain from playing contact sports until symptoms have disappeared and the player has been cleared to play by a physician.

In cases of sports-related concussion, a grading system is sometimes used to define the severity of the concussion:

  • Grade one. The player is confused and displays some mental status abnormalities that resolve within 15 minutes. The player does not lose consciousness.

  • Grade two. The player is confused and displays some mental status abnormalities that last longer than 15 minutes. The player does not lose consciousness.

  • Grade three. The player loses consciousness. Can be brief (seconds) or prolonged (minutes).

Most cases of concussion are mild and the symptoms resolve within hours or days. However, some people experience the physical and emotional symptoms of concussion for several weeks following their initial injury. This is called postconcussive syndrome. Studies have shown that the occurrence of postconcussive syndrome may not be related to the severity of the initial injury and may not be an indication that serious brain damage has taken place. Instead, it may be caused by psychological factors or subtle changes in brain chemistry.

Potential causes of concussion

A concussion occurs when the head is struck with significant force by a blunt object or when the head is violently shaken. Concussion is often associated with head injuries that are sustained while playing contact sports, from impact with the ground, another player or equipment (e.g., ball or puck). It is estimated that 300,000 head injuries occur in the United States each year as a result of sport-related accidents, according to the Centers for Disease Control and Prevention (CDC). Most of these injuries are concussions. People who play sports such as football, hockey, boxing, skiing and baseball are particularly at risk. Athletes are also more likely to sustain multiple concussions over time because each concussion increases the chance of a further concussion.

Motor vehicle accidents are another major cause of concussions. Concussion and whiplash (which can cause concussion) are common injuries sustained during a road accident. Vehicle-related accidents are the most common cause of brain injury in people under the age of 75, according to the National Institute of Neurological Disorders and Stroke (NINDS).

Falls and other accidents are common causes of concussion among children and older adults. Even small falls or minor accidents can cause concussion.

Signs and symptoms of concussion

A concussion can result in a variety of symptoms depending on the force of the blow. Signs and symptoms may last for a few hours or days and may include:

  • Loss of consciousness
  • Headache
  • General confusion (poor attention and concentration, lack of awareness of surroundings)
  • Loss of memory
  • Nausea
  • Vomiting
  • Slurred speech
  • Ringing in the ears (tinnitus)
  • Dilation in one or both pupils
  • Seizures
  • Difficulty sleeping
  • Muscle weakness
  • Irritability
  • Depression
  • Intolerance of light and noises

People experiencing these symptoms following a head injury should consult with a physician. Symptoms that do not resolve themselves after a few days, or that become more severe, may indicate a more severe head injury and require immediate treatment.

Diagnosis and treatment of concussion

People who experience concussion are encouraged to consult a physician following the injury. The physician may conduct a medical history, which may include questions relating to the circumstances of the concussion, and physical examination. If the physician is present immediately following the injury, the patient may be asked simple questions designed to assess whether the patient is alert and oriented, such as the patient’s name or the current date.  

When consulting a physician after a concussion, it is important that patients inform the physician of all the symptoms they have experienced, no matter how minor. These could include headaches, nausea, confusion or changes in mood. People who sustain a concussion often complain of vague feelings of malaise or “not feeling right.” These feelings should also be discussed with the physician.

The physician may recommend imaging tests to assess the extent of head injury following a concussion. This may especially be the case if the patient experiences symptoms that last several days. Further tests may include:

  • Computed axial tomography (CAT) scan. A CAT scan is a noninvasive or minimally invasive test that uses a rotating x-ray device to create detailed cross-sectional images (or slices) of different body parts, including the brain. CAT scans can be used to diagnose numerous conditions and complications which may arise from or be related to a concussion, such as blood clots, hematomas and skull fractures.

  • Magnetic resonance imaging (MRI). MRI is a noninvasive procedure that uses powerful magnets and radio waves to produce clear cross-sectional or three-dimensional images of the body’s tissues. MRIs are useful in cases of concussion because they can assess how the brain is functioning. Another type of MRI is called a functional MRI (fMRI). During an fMRI, the patient may be asked to perform a task while the machine scans the brain and records brain activity. This can then be used to gauge which parts of the brain may be damaged.

The most effective treatment for concussion is rest. The physician may recommend that another person observe the patient for 24 hours to ensure that the symptoms do not worsen. Painkillers may be recommended to treat headaches or neck pain. However, it is important to consult a physician before taking any medication as people with concussion may be more sensitive to the side effects of certain medications. People who are diagnosed with more severe brain injuries may be required to undergo forms of rehabilitation.

Prevention methods for concussion

Accidents that cause concussions may not be preventable. However, many of the causes of concussion can be prevented by taking suitable precautions, including:

  • Wearing protective head gear when riding a motorcycle or bicycle, or when in-line skating, skateboarding, snowboarding or skiing. Suitable head and mouth gear should also be used when playing sports such as football, baseball, boxing or hockey. Helmets should be undamaged, fit properly, and appropriate to the sport. Damaged helmets may be ineffective in protecting against concussion.

  • Always wearing a seatbelt when driving or riding in a car. Children should be buckled into an appropriate car seat or booster seat. Seatbelts should be worn at an appropriate height, using both the lap belt and shoulder harness, if available.

  • Avoiding alcohol and other drugs when operating a vehicle or playing sports. Alcohol impairs cognitive function and may make people take unnecessary risks, which increase the risk of concussion.

  • Ensuring that the home is safe. Concussions caused by falls (specifically among older people and young children) can be prevented by ensuring that the home is safe. People should be especially concerned with stairways, bathtubs and windows because these are the areas where most falling accidents occur.  

When to call 911

If a person does not lose consciousness or does so for a very brief period of time after a blow, a mild concussion rarely requires emergency treatment. However, if a person is unconscious or stops breathing, even for seconds, it may result in brain damage. In this case, someone should call emergency medical services (usually 911).

The following symptoms may occur up to several days after the head injury took place. They suggest that the brain has been seriously damaged. People who observe these symptoms in someone who has recently sustained a head injury should call 911:

  • Increasing sleepiness or confusion
  • Persistent vomiting
  • Paralysis of one or more limbs
  • Inability to speak coherently
  • Lack of coordination
  • Clear fluid (cerebrospinal fluid) draining from nose or mouth

Parents of children with a concussion are encouraged to be especially vigilant. If a child loses consciousness, even for a short period of time, emergency services should be called. Even if loss of consciousness does not take place, parents should remain alert for symptoms of serious damage such as:

  • Abnormal breathing patterns
  • Persistent crying
  • Trouble waking the child

Parents who observe any of these symptoms following a head injury should call 911.

Questions for your doctor regarding concussion

Preparing questions in advance can help patients have more meaningful discussions with healthcare professionalsregarding their condition. Patients may wish to ask their doctor the following concussion-related questions:

  1. Could my symptoms be caused by something other than a concussion?
  2. When will I be able to resume normal activities?
  3. How soon will I be able to start playing sports again?
  4. Will there be any long-term effects from my concussion?
  5. What methods will you use to assess the extent of my concussion?
  6. Should I stop taking my usual medications?
  7. What should I look out for if my child has a concussion?
  8. Should I stop my child from participating in certain activities following a concussion?
  9. Will a concussion affect my pregnancy?
  10. Am I more susceptible to concussions after experiencing the first one?
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