What is A Concussion?

Concussion defined

• The word concussion is derived from the Latin word "concutere", meaning to shake violently.
• A concussion is an injury to the brain that causes a measurable loss of normal brain function, which lasts for several days, weeks, or even months in some athletes and can have serious, long-term consequences.¹ 
• A concussion is a very complex physiologic event which interferes with brain function, not brain structure.
• A concussion is sometimes referred to as a mild traumatic brain injury (mTBI).  Whether it is appropriate to use the terms concussion and mTBI interchangeably has generated some controversy. A recent Canadian study argues that labeling a child's head injury as a "concussion" convey the wrong message to parents, athletes and athletic trainers about its seriousness, and that to encourage full reporting of head injuries in sports and to allow adequate management and recovery time MTBI be used in its place.  On the other hand, the American Academy of Pediatrics' 2010 Clinical Report on Concussions, and MomsTeam's pediatric sports concussion expert, Dr. William P. Meehan III, view  use of the terms interchangeably as inappropriate. 

How a concussion happens

• In layperson's terms, a concussion is caused by a bump or blow to the head or by a jolt to the body that causes the head to move rapidly back and forth.
• The  blow causes the brain - a jellylike structure which is normally protected from collisions with the skull by a tough, fluid-filled membrane - to be sent spinning in the opposite direction from the blow.  It is this rapid movement, acceleration, or "spinning" of the brain that causes it to malfunction, which has lead scientists to conclude that, in order to sustain a concussion, the head must be free to move.
• A concussion is like a break in the local cables in a television network that results in lengthy re-routing of the call, so that when it finally getsthrough, it's delayed and full of static.

Effects of concussion

Concussions can have short-term effects and long-term effects. 

Concussions can affect:

• Memory
• Judgment
• Reflexes
• Speech
• Balance
• Coordination
• Sleep
• Emotions

A head injury can result in serious complications, such as swelling, bruising or bleeding of the brain, which can cause permanent disability or death. If an athlete sustains a second head injury, even with a minor amount of force, prior to recovering from a concussion, he or she may be predisposed to these complications, including second impact syndrome.

Concussions can lead to long-term health problems, such as depression.

Common features of concussion

Every concussion is different, so that treatment and recovery time varies from individual to individual. But all concussions are alike in five ways:

1. Direct blow to head not required. A concussion can be caused by a direct blow to the head, face, neck, or elsewhere on the body with a force transmitted to the head.
2. Rapid onset and gradual resolution of symptoms. A concussion typically results in the rapid onset of symptoms of impaired neurological function which, in most cases, gradually disappear spontaneously with rest, usually within a week to 10 days but, in a small percentage of cases (between 5 and 10 percent), sometimes persist for weeks, months, or even years in some athletes.
3. Brain function disrupted. A concussion may result in neuropathological changes, but the acute clinical symptoms largely reflect disruption of the way the brain functions rather than injury to the brain itself.
4. Loss of consciousness not required. Concussions result in a set of clinical symptoms that may or may not involved loss of consciousness (LOC). Resolution of clinical and cognitive symptoms typically follow a sequential course, but in a small percentage of cases, post-concussive symptoms may be linger for a long period of time (post-concussion syndrome).
5. Normal MRI/CAT scans. Concussion is typically associated with grossly normal structural neuroimaging studies. In other words, unlike other injuries, concussions are usually injuries no one sees and, contrary to popular belief, don't show up on most magnetic resonance imaging (MRI) exams or CT scans. A brain CT - or, where available, MRI brain scan - should, however, be conducted if symptoms of a more serious brain injury are present.

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1. Koh, Linda, Concussion in High School Sports, Government Accountability Office (May 20, 2010)

2. Consensus Statement on Concussion in Sport: the 3rd International Conference onConcussion in Sport held in Zurich, November 2008, P. McCrory et. al, Br. J. Sports Med. 2009; 43; i76-i84.   

Additional source: Meehan WP. Kids, Sports, and Concussion (Praeger 2011).

Revised and updated January 28, 2012