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For Young Athletes With Concussion, On-The-Field Amnesia, Not Loss Of Consciousness, Predictive Of Post-Injury Symptom Severity

PITTSBURGH, July 10, 2003 In a University of Pittsburgh Medical Center (UPMC) study of high school and college athletes with concussion, on-the-field amnesia, not loss of consciousness, as long thought, was predictive of post-injury symptom severity and neurocognitive deficits. The study was conducted by the UPMC Sports Medicine Concussion Program and is published in the July 10 issue of the Clinical Journal of Sport Medicine. It is the first published study to examine the relationship of on-the-field concussion severity markers to post-injury symptom and deficit severity in high school and college athletes.

Our study results strongly indicate that young concussed athletes who demonstrate any degree of amnesia immediately following injury or any other prolonged symptoms should not return to play before undergoing comprehensive assessment by a physician, beyond the sideline evaluation, said Michael (Micky) Collins, Ph.D., a neuropsychologist who is the studys principal investigator and assistant director of the UPMC Sports Medicine Concussion Program.

Our analysis also underscores the need for further refinement of currently used sports concussion symptom grading scales because almost all of them base injury severity and return-to-play recommendations on the presence of on-the-field loss of consciousness, not amnesia or other symptoms, said Dr. Collins.

In the study, concussed athletes who scored poor on symptom and mental deficit testing at two days post-injury were 10 times more likely to have exhibited retrograde amnesia when compared to concussed athletes who scored good on day two post-injury testing. Retrograde amnesia is the inability to recall events during a period of time preceding injury. The concern with this result is that no current concussion grading system explicitly includes retrograde amnesia as a criterion for injury severity, explained Dr. Collins.

Similarly, athletes in the poor group were four times more likely to have experienced post-traumatic amnesia when compared to the good group. Post-traumatic amnesia is a loss of memory after the time of injury.

Meanwhile, study results also showed no differences between the good and poor groups in terms of on-the-field loss of consciousness. Yet, almost all current concussion grading systems consider loss of consciousness more severe than amnesia and other symptoms, said Dr. Collins. The genesis of the assumption that greater morbidity and worse outcome is associated with loss of consciousness may be mostly attributed to the decades of neurological research into long-term loss of consciousness following more serious traumatic brain injury. However, extrapolating from this data to aptly describe the subtle effects of sports concussion may be potentially erroneous and misleading, he said.

An estimated 300,000 sports-related concussions occur each year in the United States. Concussion is defined as any change in mental status that is caused by the brain being violently rocked inside the skull due to a blow to the head or upper body. Symptoms may include confusion, disorientation, amnesia, headache, nausea, uncoordinated hand-eye movements and, in some cases, loss of consciousness.

Concussion may be the most elusive injury to the sports medicine community because symptoms are not always straightforward or easily measured objectively and not always reported by the athlete, said Mark Lovell, Ph.D., a neuropsychologist, study investigator and director of UPMCs sports concussion program. Most athletes who sustain an initial concussion can recover completely as long as they do not sustain a second concussion before the brain has had time to heal from the first one. Previous studies have shown that there is a period of time following concussion when the brain is much more susceptible to further, more serious injury. Therefore, it is absolutely essential that the brain has had time to heal and the athlete is symptom-free before returning to play, said Dr. Lovell.

Currently there is no consensus on the definitive diagnosis of concussion, the parameters regarding return-to-play following injury, or the short- and long-term neurological consequences associated with concussion, said John Norwig, M.Ed., ATC, the head certified athletic trainer for the Pittsburgh Steelers and study investigator. This is the first study that correlates post-injury outcome to initial on-the-field symptoms. The lack of a scientific foundation in this area is a main reason that there are numerous different concussion severity grading scales currently in use, each with its own numeric value for various symptoms and corresponding return-to-play recommendations, said Norwig.

There is a need for continued refinement of grading scales, clearer consensus of return-to-play guidelines and further scientific research into the short- and long-term symptoms and deficits associated with sports concussion, Norwig stressed.

The UPMC study involved 78 high school and college athletes with concussions. Researchers evaluated the symptoms and neurocognitive deficits of the athletes, on average, two days following injury, using ImPACT (Immediate Post-Concussion Assessment and Cognitive Testing). ImPACT, developed by UPMC sports concussion researchers, is the first computerized concussion evaluation system that involves the collection of pre-season baseline neurocognitive function data that is stored and compared to post-injury data by re-testing the athlete after concussion. ImPACT helps to accurately and objectively measure the effects of concussion as well as help determine when it is safe for an athlete to return to sports following injury. Generally, only when post-injury ImPACT scores match the athletes baseline scores is the athlete cleared to return to play.

All of the 78 athletes had undergone pre-season baseline ImPACT testing. In the study, 44 of the 78 athletes demonstrated good post-injury presentation with ImPACT as compared to their baseline scores. Thirty-four of the 78 athletes demonstrated poor post-injury presentation. Athletes in the poor presentation group were 10 times more likely to have exhibited retrograde amnesia and four times more likely to experience post-traumatic amnesia when compared to athletes in the good presentation group. There were no differences between the groups in terms of on-the-field loss of consciousness.

Of the 78 study participants, 61 were high school athletes and 17 were in college; 88.5 percent of them were male; the average age was 16.8 years; 69.2 percent were football players; the remaining represented soccer, hockey, basketball, lacrosse and baseball. The athletes were from Pennsylvania, Illinois and Maine. All of the athletes in the study were evaluated by participants in the UPMC Sports Medicine Concussion Program, an internationally recognized program whose main focus is the proper management of sports-related concussion and the development and implementation of methods, such as ImPACT, to accurately measure the effects of concussion and determine when it is safe for athletes to return to play following concussion.

For more information on concussion research at UPMC, please access the concussion archives.

Other investigators in the study were Grant Iverson, Ph.D., University of British Columbia, Vancouver, Canada; Douglas McKeag, M.D., Indiana University School of Medicine; and Joseph Maroon, M.D., University of Pittsburgh School of Medicine.

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