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Concussion and Mild Traumatic Brain Injury

General Information


  • traumatic brain injury (TBI) is due to structural injury and/or physiologic disruption of brain function from blunt trauma, acceleration or deceleration forces, penetration of foreign body, or exposure to blast1
  • TBI characterized by new onset or worsening of1
    • any period of confusion, disorientation, change in consciousness, or amnesia that may or may not be transient
    • observed neurologic dysfunction
    • intracranial lesion
  • concussion is a type of mild TBI induced by biomechanical forces5
    • may be caused by direct blow to head, face, or neck, or blow to body with impulsive force transmitted to head
    • typically rapid onset of short-lived neurologic impairment that resolves spontaneously; however, symptoms and signs may evolve over minutes to hours in some cases
    • results in graded set of clinical symptoms with or without loss of consciousness
      • usually with sequential resolution of clinical and cognitive symptoms, but symptoms may be prolonged in some cases
      • symptoms and signs not explained by drug, alcohol, or medication use, other injuries such as vestibular dysfunction, or comorbidities
    • symptoms and signs reflect functional disturbance rather than structural injury; no abnormality on standard neuroimaging

Also called

  • closed head injury
  • sports concussion
  • sports-related concussion
  • athletic concussion
  • commotio cerebri


General references used

  1. Management of Concussion/Mild Traumatic Brain Injury Working Group. Veterans Affairs/Department of Defense clinical practice guideline for management of concussion/mild traumatic brain injury. VA/DoD 2016PDF
  2. National Institute for Health and Care Excellence. Head injury: assessment and early management. NICE 2014 Jan 22: CG176
  3. Lumba-Brown A, Yeates KO, Sarmiento K, et al. Centers for Disease Control and Prevention Guideline on the Diagnosis and Management of Mild Traumatic Brain Injury Among Children. JAMA Pediatr. 2018 Nov 1;172(11):e182853
  4. Halstead ME, Walter KD, Moffatt K, COUNCIL ON SPORTS MEDICINE AND FITNESS. Sport-Related Concussion in Children and Adolescents. Pediatrics. 2018 Dec;142(6):e20183074
  5. McCrory P, Meeuwisse W, Dvořák J, et al. Consensus statement on concussion in sport-the 5th international conference on concussion in sport held in Berlin, October 2016. Br J Sports Med. 2017 Jun;51(11):838-847
  6. Meehan WP 3rd, Bachur RG. Sport-related concussion. Pediatrics. 2009 Jan;123(1):114-23
  7. Giza CC, Kutcher JS, Ashwal S, et al. Summary of evidence-based guideline update: Evaluation and management of concussion in sports: report of the Guideline Development Subcommittee of the American Academy of Neurology. Neurology. 2013 Jun 11;80(24):2250-7full-text, editorial can be found in Neurology 2013 Jun 11;80(24):2178

Recommendation grading systems used

  • Centers for Disease Control and Prevention (CDC) uses American Academy of Neurology (AAN) levels of recommendation
    • strength of recommendation
      • Level A - recommendation almost always should be followed
      • Level B - recommendation usually should be followed
      • Level C - recommendation may sometimes be followed
      • Level U - insufficient evidence to make a recommendation
      • Level R - intervention generally should not be done outside research setting (applicable only to recommendations related to interventions)
    • level of confidence
      • High
      • Moderate
      • Low
      • Very low
    • Reference - CDC guideline on diagnosis and management of mild traumatic brain injury among children (JAMA Pediatr 2018 Nov 1;172(11):e182853)
  • American Academy of Neurology (AAN) levels of recommendation
    • Level A
      • clinician level of obligation - "must"
      • high confidence in evidence
      • large benefit relative to harm
    • Level B
      • clinician level of obligation - "should"
      • moderate confidence in evidence
      • moderate benefit relative to harm
    • Level C
      • clinician level of obligation - "might"
      • low confidence in evidence
      • small benefit relative to harm
    • Level U
      • no recommendation supported
      • very low confidence in evidence
      • benefit and harm judged to be the same or too close to call
    • Reference - AAN guideline on evaluation and management of concussion in sports (23508730Neurology 2013 Jun 11;80(24):2250full-text)
  • American College of Emergency Physicians (ACEP) grading system
    • levels of recommendation
      • Level A - generally accepted principles for patient management with high degree of clinical certainty (class I evidence or overwhelming class II evidence that directly addresses all the issues)
      • Level B - moderate clinical certainty (class II evidence that directly addresses the issue, decision analysis that directly addresses the issue, or strong consensus of class III studies)
      • Level C - based on preliminary, inconclusive, or conflicting evidence, or based on panel consensus without any published literature
    • classification of evidence
      • Class I studies
        • for therapy - randomized trial or meta-analysis of randomized trials
        • for diagnosis - prospective cohort using criteria standard
        • for prognosis - population prospective cohort study
      • Class II studies
        • for therapy - nonrandomized trial
        • for diagnosis - retrospective observational study
        • for prognosis - retrospective cohort or case-control study
      • Class III studies - case series, case report, or other (for example, consensus, review) for any type of study
    • Reference - ACEP and Centers for Disease Control and Prevention (CDC) clinical policy on neuroimaging and decision-making in adult mild traumatic brain injury in acute setting (19027497Ann Emerg Med 2008 Dec;52(6):714)
  • Department of Veterans Affairs/Department of Defense (VA/DoD) grading system for recommendations
    • Strong - work group highly confident desirable outcomes outweigh undesirable outcomes or vice versa
    • Weak - work group less confident of balance between desirable and undesirable outcomes
    • Reference - VA/DoD clinical practice guideline for management of concussion/mild traumatic brain injury (VA/DoD 2016PDF)
  • Eastern Association for the Surgery of Trauma (EAST) levels of recommendation
    • Level 1 - convincingly justifiable based on available scientific information alone
    • Level 2 - reasonably justifiable by available scientific evidence and strongly supported by expert opinion
    • Level 3 - supported by available data but adequate scientific evidence is lacking
    • Reference - EAST practice management guideline on evaluation and management of mild traumatic brain injury (23114486J Trauma Acute Care Surg 2012 Nov;73(5 Suppl 4):S307)

Synthesized Recommendation Grading System for DynaMed Content

  • The DynaMed Team systematically monitors clinical evidence to continuously provide a synthesis of the most valid relevant evidence to support clinical decision-making (see 7-Step Evidence-Based Methodology).
  • Guideline recommendations summarized in the body of a DynaMed topic are provided with the recommendation grading system used in the original guideline(s), and allow users to quickly see where guidelines agree and where guidelines differ from each other and from the current evidence.
  • In DynaMed content, we synthesize the current evidence, current guidelines from leading authorities, and clinical expertise to provide recommendations to support clinical decision-making in the Overview & Recommendations section.
  • We use the Grading of Recommendations Assessment, Development and Evaluation (GRADE) to classify synthesized recommendations as Strong or Weak.
    • Strong recommendations are used when, based on the available evidence, clinicians (without conflicts of interest) consistently have a high degree of confidence that the desirable consequences (health benefits, decreased costs and burdens) outweigh the undesirable consequences (harms, costs, burdens).
    • Weak recommendations are used when, based on the available evidence, clinicians believe that desirable and undesirable consequences are finely balanced, or appreciable uncertainty exists about the magnitude of expected consequences (benefits and harms). Weak recommendations are used when clinicians disagree in judgments of relative benefit and harm, or have limited confidence in their judgments. Weak recommendations are also used when the range of patient values and preferences suggests that informed patients are likely to make different choices.
  • DynaMed synthesized recommendations (in the Overview & Recommendations section) are determined with a systematic methodology:
    • Recommendations are initially drafted by clinical editors (including ≥ 1 with methodological expertise and ≥ 1 with content domain expertise) aware of the best current evidence for benefits and harms, and the recommendations from guidelines.
    • Recommendations are phrased to match the strength of recommendation. Strong recommendations use "should do" phrasing, or phrasing implying an expectation to perform the recommended action for most patients. Weak recommendations use "consider" or "suggested" phrasing.
    • Recommendations are explicitly labeled as Strong recommendations or Weak recommendations when a qualified group has explicitly deliberated on making such a recommendation. Group deliberation may occur during guideline development. When group deliberation occurs through DynaMed Team-initiated groups:
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      • Evidence will be summarized for recommendation panel review including for each outcome, the relative importance of the outcome, the estimated effects comparing intervention and comparison, the sample size, and the overall quality rating for the body of evidence.
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      • All recommendation panel members must disclose any potential conflicts of interest (professional, intellectual, and financial), and will not be included for the specific panel if a significant conflict exists for the recommendation in question.
      • Panel members will make Strong recommendations if and only if there is consistent agreement in a high confidence in the likelihood that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. Panel members will make Weak recommendations if there is limited confidence (or inconsistent assessment or dissenting opinions) that desirable consequences outweigh undesirable consequences across the majority of expected patient values and preferences. No recommendation will be made if there is insufficient confidence to make a recommendation.
      • All steps in this process (including evidence summaries which were shared with the panel, and identification of panel members) will be transparent and accessible in support of the recommendation.
    • Recommendations are verified by ≥ 1 editor with methodological expertise, not involved in recommendation drafting or development, with explicit confirmation that Strong recommendations are adequately supported.
    • Recommendations are published only after consensus is established with agreement in phrasing and strength of recommendation by all editors.
    • If consensus cannot be reached then the recommendation can be published with a notation of "dissenting commentary" and the dissenting commentary is included in the topic details.
    • If recommendations are questioned during peer review or post publication by a qualified individual, or reevaluation is warranted based on new information detected through systematic literature surveillance, the recommendation is subject to additional internal review.

DynaMed Editorial Process

  • DynaMed topics are created and maintained by the DynaMed Editorial Team and Process.
  • All editorial team members and reviewers have declared that they have no financial or other competing interests related to this topic, unless otherwise indicated.
  • DynaMed content includes Practice-Changing Updates, with support from our partners, McMaster University and F1000.

Special acknowledgements

On behalf of the American College of Physicians
  • Barbara Turner, MD, MSEd, MACP, ACP Deputy Editor, Clinical Decision Resource, as part of the ACP-EBSCO Health collaboration, managed the ACP peer review of the Overview and Recommendations section and related clinical content in this topic.
  • The American Academy of Neurology (Chris Giza, MD, PhD, AAN Concussion Guideline lead author; Julie Cox, MFA, AAN Staff; Thomas Getchius, AAN Staff) provides review for the incorporation of American Academy of Neurology guidelines.
  • Choosing Wisely Canada acknowledges dissemination of their recommendations through DynaMed Plus to reach the point of clinical decision-making.
  • The Canadian Association of Emergency Physicians provides review for the incorporation of Choosing Wisely Canada recommendations.
  • The Canadian Association of Radiologists provides review for the incorporation of Choosing Wisely Canada recommendations.
  • DynaMed topics are written and edited through the collaborative efforts of the above individuals. Deputy Editors, Section Editors, and Topic Editors are active in clinical or academic medical practice. Recommendations Editors are actively involved in development and/or evaluation of guidelines.
  • Editorial Team role definitions
    Topic Editors define the scope and focus of each topic by formulating a set of clinical questions and suggesting important guidelines, clinical trials, and other data to be addressed within each topic. Topic Editors also serve as consultants for the internal DynaMed Editorial Team during the writing and editing process, and review the final topic drafts prior to publication.
    Section Editors have similar responsibilities to Topic Editors but have a broader role that includes the review of multiple topics, oversight of Topic Editors, and systematic surveillance of the medical literature.
    Recommendations Editors provide explicit review of Overview and Recommendations sections to ensure that all recommendations are sound, supported, and evidence-based. This process is described in "Synthesized Recommendation Grading."
    Deputy Editors oversee DynaMed internal publishing groups. Each is responsible for all content published within that group, including supervising topic development at all stages of the writing and editing process, final review of all topics prior to publication, and direction of an internal team.

How to cite

National Library of Medicine, or "Vancouver style" (International Committee of Medical Journal Editors):

  • DynaMed [Internet]. Ipswich (MA): EBSCO Information Services. 1995 - . Record No. T116529, Concussion and Mild Traumatic Brain Injury; [updated 2018 Nov 30, cited place cited date here]. Available from Registration and login required.

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