• A violent blow to the head and neck or upper body can cause the brain to slide back and forth.
• Sudden acceleration or deceleration of the head, caused by events such as a car crash, or sudden jerky movements
• Risk factors include:
• Previous history of concussion
• Participating in high-risk sports such as football and basketball, without proper safety equipment and supervision

If untreated for a prolonged period it may lead to

• Post-traumatic headaches: People experience headaches within a week to 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.
• Cumulative effects of multiple brain injuries: Progressive impairment of cognitive function.
• Second impact syndrome: Experiencing a second concussion before symptoms of the first concussion have resolved, may result in rapid and usually fatal brain swelling.