What is a concussion?
A change in mental state -- confusion, dizziness, loss of consciousness -- brought about when the brain slams against the sides of the skull.

What causes it?
A blow to the head, face or jaw, or a whiplash effect on the neck.

Are all concussions the same?
No. There are two degrees of the injury:

First degree - sensation of a bell being rung, involves no loss of consciousness. Confusion might follow. If symptoms persist, then the concussion is considered second-degree. Even in first degree, though, a player should be referred to a doctor.

Second degree - if no loss of consciousness, second degree considered when symptoms of a first-degree concussion last longer than 15 minutes. The player must be referred to a doctor, and may need to be hospitalized.

What are the symptoms?
Symptoms vary according to the kind and severity of the injury, but here are some of the more common ones:

• "bell rung"
• headache
• dizziness/feeling light-headed
• vacant stare
• seeing stars or lights
• disoriented
• delayed response to questions
• confused and easily distracted
• slurred speech
• poor co-ordination
• fatigue
• nausea, vomiting