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Loss of Consciousness May Not Predict Concussion Severity
By: Laurie Barclay, MD
July 28, 2003 — Loss of consciousness does not seem to be helpful in determining the severity
of concussion, according to two presentations at the 29th annual meeting of the American
Orthopedic Society for Sports Medicine held in San Diego. Results of a neuropsychological test
battery, the Immediate Post-concussion Assessment and Cognitive Test (ImPACT), were similar in
patients with concussion who had loss of consciousness and those who did not, supporting the
recommendation that current guidelines for diagnosis of concussion are inadequate.
"Athletes may sustain a severe concussion without losing consciousness," lead author Mark R.
Lovell, PhD, ABPN, from the University of Pittsburgh Medical Center (UPMC) in Pennsylvania,
says in a news release. "Amnesia and confusion on the field after injury may be as important, if
not more important, in making a return-to-play decision."
Of 181 high school and college athletes with sports-related concussions, 30 had documented loss
of consciousness and 151 had no documented loss of consciousness. At 24 to 48 hours post injury,
there were no significant differences between these groups in performance on memory, reaction time,
and processing speed.
Existing systems for grading concussions, in which loss of consciousness is considered to be the
sole or primary indicator of serious injury, lack evidence-based support. According to these grading
systems, athletes with other symptoms of concussion, such as amnesia and confusion, may be permitted
to return to regular activities earlier than those who lost consciousness.
The recent Vienna consensus conference on concussion management questioned the role of loss of
consciousness, criticized the existing guidelines, and emphasized the value of individualized
evaluation and neuropsychological testing.
"We recommend that anyone who is thought to have had a concussion not be put back into athletic
contest until he or she has been thoroughly evaluated by a physician and undergone neuropsychological
testing," Dr. Lovell says. "This is especially important with athletes 18 years of age and younger
because their brains are still developing."
A second presentation by the same group reported on a simple, databased approach to measure concussion
severity using the 20-minute, computerized test. The ImPACT battery, which evaluates brain functions,
affected by concussion, including reaction time, processing speed, cognitive ability, and memory, is
used by many professional athletic organizations, as well as 250 U.S. colleges, universities, and high
schools. The normative database of ImPACT has been tested on more than 10,000 athletes.
"ImPACT is a brain physical," says lead author Michael W. Collins, PhD. "Following concussion the
brain slows and we can pick that up by measuring response time to various stimuli."
In a comparison of 231 concussed high school and college athletes with 50 non-concussed age- and
sex-matched controls, ImPACT accurately identified the concussed athletes. At two and five days after
injury, the concussed athletes performed significantly worse than the controls in memory, processing
speed, and reaction time, and memory deficits persisted in some athletes to the eighth post injury
day. Although many athletes report improved symptoms by the fifth day post injury, recovery time from
concussion could take up to 10 days.
"We are finding memory deficits and neurocognitive functioning deficits that last up until day 10 post
injury," Dr. Collins says. "The athletes are either feeling much better immediately following the injury
or they are minimizing their problems to get back earlier. Personally, I think it's a combination."
In a related pilot study, functional magnetic resonance imaging studies in six concussed athletes
showed abnormal brain activation patterns within 24 to 48 hours after injury. These abnormalities
resolved within eight days, on average.
"All concussions need to be taken seriously," Dr. Collins says. "A physician who is knowledgeable
about sports medicine should carefully evaluate concussed athletes. Neuropsychological tools like
ImPACT can quantify the injury and make evidence-based decisions about when an athlete should
return to play."