A coma is when a person is in such a deep state of unconsciousness that the individual is unable to be awakened. Severe illness and injuries such as concussions and brain trauma are the most frequent causes of comas. It derives from the Greek word koma, meaning 'deep sleep."
Helmets are a common accessory for many sports today. Research and public awareness about the dangers associated with head trauma mean individuals are donning better protection for bike riding, high-impact sports and many other recreations. When residents of Phoenix, Arizona, take a ski holiday, however, they should know that wearing a helmet while on the slopes may not prevent all accident-related brain injuries.