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Most recent update: April 29, 2012 : This page is not written for or intended for use in legal endeavors.
Concussion comes from the Latin word, "to shake violently" (Webster). Most concussions in adults are caused by direct blows to the head. However, it is also accepted that occasionally, such as in the "shaken baby" syndrome, concussions can occur without a direct blow to the head after a very forceful acceleration/decelleration.
The American Academy of Neurology (AAN) defined concussion in 1997 as "any trauma-induced alteration in mental status that may or may not include loss of consciousness". In other words, they defined it as the combination of a change in mental status associated with "trauma". (Practice Paramater, 1997). We think that this definition is so all-inclusive as to be almost meaningless as by this a "concussion" could be a change in one's mood after an acorn fell on one's head. Other groups have been similarly vague. Sports reseachers in 2001, specified that a concussion must be caused by trauma that transmits an "impulsive" force to the head. At least they are saying that the head must be affected. What isn't so clear is how "impulsive" force is defined. They also indicated that concussion is typically associated with normal stuctural imaging studies. (Aubry et al, 2001).
Whether or not a concussion occured after in a "whiplash" type accident, where there was no or minimal force to the head, is often debated by attorneys. Considering the vagueness of the definitions adopted by the groups above, nearly anything (including feeling distressed after a ping-pong ball dropping on one's head) would qualify.
The neck is more vulnerable than the brain -- and it takes almost an order of magnitude more force to cause a significant brain injury than a neck injury (see whiplash page).
Concussion is thus a mental disturbance which follows a so-far undefined amount of movement of the head, without an identifiable etiology on imaging. It is a "wastebasket" diagnosis made by excluding other diagnoses. If an etiology can be determined for the cognitive symptoms, then the more specific diagnosis is used. However, concussion is a convenient term as it communicates the idea that the person hit their head, and now can't think as well as before.
Post concussion syndrome is often attributed to "Traumatic Brain Injury", or TBI, which is a general term for a head injury caused by trauma, affecting the brain. Again, there is considerable looseness to this term too.
To be reasonable, one must differentiate "significant", or maybe "real" concussions from events that meet the literature's criteria, but that no reasonable person would accept as being a cause impairment or disability.
Our general impression is that "significant" concussions are unlikely consequences of whiplash mechanism accidents. We are also dubious that significant cognitive symptoms should follow regularly after a head injury unaccompanied by a loss of consiousness. Not impossible, but we uncommon.
In any case, while dizziness and nausea symptoms accompanying the entity called "concussion" in the literature usually resolve over 6 weeks, cognitive symptoms and headaches persist longer. Hoffer et al (2004) suggested that symptoms persisted an average of 39 weeks -- about 9 months, and that return to work usually occured at about 16 weeks. Occasionally symptoms are permanent. As noted above, in many cases, chronic symptoms are psychological in origin. Balance symptoms after concussion generally (i.e. 50% of the time) resolve by 10 days (Peterson et al, 2003). Nevertheless, there are many persons who have longer lasting symptoms. Our experience has been that balance symptoms post neck injury can take much longer to resolve.
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