Driving, biking and contact sports such as football, boxing or wrestling can result in an injury to the head. While your head is designed to protect the brain from minor blows, it is important to know the warning signs and effects of a more traumatic brain injury.

The brain is soft and fragile, protected by two layers: spinal fluid and the skull. With a strong enough blow, the brain may pierce the protective fluid layer and strike the inside of your skull, causing a concussion, the most common type of brain injury.

Sometimes, a person with a concussion may lose consciousness but symptoms are not always that obvious. Other signs of concussion include:

• Difficulty thinking and remembering
• Headaches
• Nausea, vomiting and dizziness
• Difficulty with balance
• Lack of energy
• Blurred vision
• Abnormal mood changes and sleep patterns

An extreme example of the seriousness of brain injury is the case of pro-wrestler Chris Benoit. In 2007, Benoit shocked the country when he murdered his wife and son, and then killed himself. While it is impossible to know exactly what motivated the killings, Benoit had received many concussions over the course of his 22-year wrestling career, and post-mortem study of his brain revealed extensive damage.

Today, the major North American sports leagues all have policies in place in order to detect concussions and monitor injured players. The NFL, for example, requires a player who has a concussion to be cleared by an independent neurologist before returning to play.

High school and college athletes are also at risk. A frequently cited study by the National Center for Injury Prevention found that 47% of high school football players suffer a concussion each season.

Symptoms of concussion or other head injuries do not always manifest themselves immediately.  If you have been involved in an accident where you received a blow to the head, seek medical attention immediately.