Garret McIntyre lands on injured list with head injury

The Ravens won by a large margin, 34-17.

Concussions are not a bruise to the brain and do not cause bleeding nor swelling, as some mistakenly believe. Rather, a concussion happens when the head is accelerated quickly then abruptly stopped, causing the head and brain to shake violently. Concussions are also caused by a strike to the head or a fall.

Concussions are usually the result of a head injury, especially to those playing American football. Neurologists state that once a person has one concussion, his or her chances of acquiring another concussion increase up to four times. In addition, once someone has suffered several concussions, it takes less of a hit to cause another concussion and takes longer to recover.

Concussions can cause the following:

* Confusion

* Blurred vision

* Memory loss

* Nausea

* Occasionally, unconsciousness

NFL concussion studies; Continue reading; http://sports.yahoo.com