Comprehensive concussion literature analysis lays foundation for evidence-based guidelines

Despite the plethora of peer-reviewed research, there is presently no evidence-based definition for concussion that is uniformly applied in clinical and research settings. Current imaging and biomarkers research show promise, but fall short of providing evidence to support the use of a physiologic marker to identify concussion.

"The goal of this extensive analysis was to identify the most prevalent signs, symptoms, and deficits, and their associations, following a force to the head, in athletic, hospital, and military populations," said Jamshid Ghajar, MD, PhD, president of the Brain Trauma Foundation, and director of the Stanford Concussion and Brain Trauma Center. "We compiled data from the strongest scientific research, which provides an evidence-based foundation for diagnostic and prognostic criteria, and eventually treatment guidelines," added lead study author Nancy Carney, PhD, of Oregon Health & Science University, who is director of research for the Brain Trauma Foundation.

Concussion Guidelines Step 1: Systematic Review of Prevalent Indicators is a special supplement of Neurosurgery, official journal of the Congress of Neurological Surgeons. It is authored by Nancy Carney, PhD; Jamshid Ghajar, MD, PhD; Andy Jagoda, MD; Steven Bedrick, PhD; Cynthia Davis-O'Reilly, BSc; Hugo du Coudray, PhD; Dallas Hack, MD; Nora Helfand; Amy Huddleston, MPA; Tracie Nettleton, MS; and Silvana Riggio, MD.

From 5437 abstracts, 1362 full-text publications were reviewed, of which 231 studies were included in the final library. Only 26 of these met stringent criteria required to be used for this analysis. Because of the lack of sufficient objective data from strong studies, concussion remains undefined. There was sufficient reliable information to compile the following:

The most prevalent indicators of concussion, observed in alert individuals (Glascow Coma Scale of 13 to 15) after a force to the head are:

·Observed and documented disorientation or confusion immediately after the event

·Impaired balance within 1 day after injury

·Slower reaction time within 2 days after injury

·Impaired verbal learning and memory within 2 days after injury

Key Findings -- Among the studies included in the review:

·Loss of Consciousness (LOC) ranged from 1% to 14.3%

·Posttraumatic amnesia (PTA) ranged from 2% to 29.7%

·Retrograde amnesia ranged from 7.4% to 53.3%

·Disorientation/confusion ranged from 18% to 44.7%

·The prevalence of balance deficits ranged from 23.8% to 36.5% within 24 hours of injury and decreased to 19.2% to 24% by day 2.

·The prevalence of slowed reaction time ranged from 41.7% to 71.4% within 24 hours of injury.

·Findings indicated that in the majority of cases, cognitive deficits resolved within one week.

Influence of Prior Concussions

There has been a good deal in the news about athletes who incur multiple concussions, and the permanent brain damage that may occur due to repeated hits to the head. This review identified two well-designed and executed studies that appear to provide evidence for greater vulnerability in individuals with multiple concussions:

·In one study, individuals with a history of previous concussions had lower baseline scores than those without previous concussions on tests of cognitive function.

·In another study, odds of sustaining a 14-point drop in a memory test within 5 days of injury were 7 to 8 times greater for athletes who sustained prior concussions.

"It is important to understand that the findings in this report are limited by the nature and quality of the available scientific studies. Clearly more research is needed in order to derive a comprehensive and evidence-based picture of concussion," Dr. Carney said.

"Most of the studies used to compile the evidence in this report about what are true indicators of concussion were conducted among athletes," Dr. Ghajar stated. "We know very little about hospital and military populations. We hope our report will inspire a new generation of strong studies designed to fill the gaps in information we discovered and identified. The forthcoming report in our series will focus on evidence-based diagnostic criteria for concussion."