https://www.mayoclinic.org/diseases-conditions/concussion/symptoms-causes/syc-20355594
Concussions are usually caused by a blow to the head. Violently shaking the head and upper body also can cause concussions.
Seek emergency care for an adult or child who experiences a head injury and symptoms such as:
Repeated vomiting
Your brain has the consistency of gelatin. It's cushioned from everyday jolts and bumps by cerebrospinal fluid inside your skull.
A violent blow to your head and neck or upper body can cause your brain to slide back and forth forcefully against the inner walls of your skull.
Sudden acceleration or deceleration of the head, caused by events such as a car crash or
being violently shaken, also can cause brain injury.
These injuries affect brain function, usually for a brief period, resulting in signs and symptoms of concussion.
This type of brain injury may lead to bleeding in or around your brain, causing symptoms such as prolonged drowsiness and confusion. These symptoms may develop immediately or later.
Such bleeding in your brain can be fatal. That's why anyone who experiences a brain injury needs monitoring in the hours afterward and emergency care if symptoms worsen.
Risk factors
Activities and factors that may increase your risk of a concussion include:
Falling, especially in young children and older adults
Participating in a high-risk sport, such as football, hockey, soccer, rugby, boxing or other contact sport
Participating in high-risk sports without proper safety equipment and supervision
Being involved in a motor vehicle collision
Being involved in a pedestrian or bicycle accident
Being a soldier involved in combat
Being a victim of physical abuse
Having had a previous concussion
Complications
Potential complications of concussion include:
Post-traumatic headaches. Some people experience headaches within a week to a few months after a brain injury.
Post-traumatic vertigo. Some people experience a sense of spinning or dizziness for days, week or months after a brain injury.
Post-concussion syndrome. Some people have symptoms such as headaches, dizziness and thinking difficulties a few days after a concussion. Symptoms may continue for weeks or months.
Cumulative effects of multiple brain injuries. It's possible that some people who have had one or more traumatic brain injuries over the course of their lives are at greater risk of developing lasting, possibly progressive, impairment that limits function. This is an area of active research.
Second impact syndrome.
Rarely, experiencing a second concussion before signs and symptoms of a first concussion have resolved may result in rapid and usually fatal brain swelling.
Concussion changes the levels of brain chemicals. It usually takes about a week for these levels to stabilize again, but recovery time varies.
