This is a summary of the first in a series of reports that will be generated by this working group that are intended to build an evidence base for concussion. This first report, Step 1, is a systematic review of prevalent indicators of concussion that used the highest-quality published literature and a rigorous process of publication selection, quality assessment, and data abstraction and synthesis. It is the foundation on which we will base future work to derive a classification system for concussion and guidelines for diagnosis, prognosis, and treatment.
Key questions were identified and electronic literature searches conducted from 1980 to September 2012. Publications meeting the prespecified inclusion criteria were assessed for potential for bias and confound and were rated as “low, medium, or high” potential for bias and confound. Data were abstracted from those publications meeting a minimum threshold of “medium.”
Of 5592 abstracts of potentially relevant studies, 1362 full-text publications were acquired and read for eligibility. Two hundred thirty-one met the prespecified criteria, and of those, 62 publications were rated as medium potential for bias and confound. Of the 62 publications, 26 had inclusive case definitions, reported data at fixed time points relevant to 1 or more of the key questions, and are included in the analysis. Eleven independent samples from 8 publications contributed data for the final analysis.
Indicators of concussion, observed in alert (alert: Glasgow Coma Scale Score, 13 to 15) individuals after a force to the head, are the following:
* Observed and documented disorientation or confusion (disorientation or confusion: loss of one's sense of direction, position, or relationship with one's surroundings) immediately after the event
* Impaired balance (balance: a state of body equilibrium) within 1 day after injury,
* Slower reaction time (reaction time: the interval of time between application of a stimulus and detection of a response) within 2 days after injury, and
* Impaired verbal learning and memory (verbal learning and memory: the acquisition, retention, and retrieval of verbal material; memory of words and other abstractions involving language) within 2 days after injury.
A concussion is a change in brain function after a force to the head that may be accompanied by temporary loss of consciousness but is identified in awake individuals with the use of measures of neurologic and cognitive dysfunction. At this time, there are no known physiologic measures to identify this change in function. Consequently, observed physiologic phenomena (signs), subjective reports (symptoms), and objective measures of neurologic and cognitive dysfunction (deficits) that may be indicators of the underlying change in brain function are used to identify individuals with a high likelihood of having a concussion.
The task of this project was to identify which signs, symptoms, and neurologic and cognitive deficits have the highest and most consistent prevalence in samples of individuals sustaining a potentially concussive event and to assess how they associate. From the available evidence, increased reaction time, impaired verbal learning and memory, impaired balance, and disorientation or confusion were found to be significantly prevalent in early samples of exposed individuals. There is insufficient evidence to assess the relationships among these measures.
Many of the publications not included in this review were well done and adequately addressed the investigators' prespecified research questions. They were not, however, designed to generate supporting evidence for the prevalence of indicators of concussion. Most of the studies were excluded primarily because of a lack of comparison groups, mixed patient populations, time from injury not specified, measures not validated, and data reported as composite scores. Of the included publications, many could not be used in the primary analysis because of high potential for bias and confound, exclusive case definitions, or lack of relevant and/or fixed time points for measures. Of those used in the analysis, key limitations included the lack of simple correlational analyses and the use of average scores to compare differences between groups.
What is needed next is a “decomplicated” body of information that provides simple counts of signs, symptoms, neurologic and cognitive deficits; and valid and reliable outcome measures; and that associates those measures across time in the form of proportions. The forthcoming report from this working group, “Concussion Guidelines Step 2: Diagnostic Criteria,” will serve to fill this information gap and will take the next step in developing guidelines for the diagnosis, prognosis, and treatment of concussion.
Dr Jagoda is a consultant for Banyan Biomarkers. The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article. There are no conflicts of interest. The Brain Trauma Foundation Concussion Guidelines project is supported by the US Army Contracting Command, Aberdeen Proving Ground, Natick Contracting Division, under contract No. W911QY-11-C-0074. The Brain Trauma Foundation provided funding for 2 meetings of the Panel of Technical Experts.