Concussion 

  • Author: David T Bernhardt, MD; Chief Editor: Sherwin SW Ho, MD   more...
 
Updated: Nov 15, 2011
 

Background

Concussion has many different meanings to patients, families, and physicians.[1, 2, 3, 4] One definition of concussion is a condition in which there is a traumatically induced alteration in mental status, with or without an associated loss of consciousness (LOC).[4] A broader definition for concussion is a traumatically induced physiologic disruption in brain function that is manifest by LOC, memory loss, alteration of mental state or personality, or focal neurologic deficits.[4] Concussions usually result in relatively temporary impairment of neurologic function.[3, 5, 6]

Concussion or mild traumatic brain injury (MTBI) is common among most contact and collision sports participants.[4, 7, 8, 9, 10, 11, 12] For many physicians, even those who specialize in MTBI, this area is confusing due to the paucity of scientific evidence to support much of the clinical decision making that is faced in the office.[1, 2, 9, 13, 14] The inconsiderable amount of good scientific research in the area of MTBI is due to problems with ambiguous definitions of concussion, inconsistent criteria when selecting patients to study, variability of injury mechanisms and locations, and differing means of measuring cognitive function.[15, 16] The purpose of this article is to review the epidemiology and diagnosis (but not necessarily the classification) of MTBI, as well as the role of imaging studies, issues regarding return to play, and complications surrounding MTBI.

For excellent patient education resources, see the Back, Ribs, Neck, and Head Center, Brain and Nervous System, and Dementia Center, as well as Concussion, Head Injury, and Dementia in Head Injury.

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Epidemiology

Frequency

United States

The incidence of head injury varies with the sport and the age of the participants; many head injuries are likely unreported due to their supposed mild nature; mild concussions may go unnoticed by teammates, coaches, and even the athletes themselves.[4] An athlete's fear of medical disqualification may also lead to underreporting. Studies of high school athletes show the rate of concussions per 1000 exposures as follows: 0.59 for football (boys), 0.25 for wrestling (boys), 0.18 for soccer (boys; 0.23 for girls), 0.09 for field hockey (girls), and 0.11 for basketball (boys; 0.16 for girls). The data from one study noted that concussions account for nearly 15% of all sport-related injuries in high school athletes.[17]

Among National Collegiate Athletic Association (NCAA) soccer players, the rate of injury has been reported as 0.4-0.6 per 1000 athlete exposures[11] ; 72% of these injuries were described as mild and were almost always secondary to direct contact with an opponent. None of the injuries in this group of Atlantic Coast Conference (ACC) soccer players was noted to be a direct result of heading the ball. In contrast, boxing is the sport with the highest rate of head injuries and has more deaths than any other organized athletic activity. At the professional level, many of the boxing bouts end with a technical knockout (ie, brain injury).

Sports activities that place the athlete at high risk for a head injury include boxing, football, ice hockey, wrestling, rugby, and soccer. Physicians and other allied health providers who are responsible for the medical care of such contact or collision sports participants should be adept at evaluating, treating, and making playability decisions related to the short- and long-term consequences of an injury to the brain.

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Sport-Specific Biomechanics

The mechanisms of brain injury may differ among sports activities. Possible mechanisms of injury include compressive forces, which may directly injure the brain at the point of contact (coup); tensile forces produce injury at the point opposite the injury (contrecoup) because the axons and nerves are stretched; finally, rotational forces may result in a shearing of axons. Therefore, the direct force at the point of contact may not be solely responsible for the severity of an injury if a high rotational component with a significant shear effect occurs.

All of the different mechanisms may result in biochemical changes related to perfusion, energy demand, and utilization at the site of injury that are not well understood. At this time, it is unclear whether any experimental animal model or human studies on more severe brain-injured patients accurately reflect the pathophysiology of the typical mild traumatic alteration in brain function.

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Contributor Information and Disclosures
Author

David T Bernhardt, MD  Director of Adolescent and Sports Medicine Fellowship, Associate Professor, Department of Pediatrics/Ortho and Rehab, Division of Sports Medicine, University of Wisconsin School of Medicine and Public Health

David T Bernhardt, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Sports Medicine, and American Medical Society for Sports Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Joseph P Garry, MD, FACSM, FAAFP  Associate Professor, Sports Medicine Faculty, Department of Family and Community Medicine, University of Minnesota Medical School

Joseph P Garry, MD, FACSM, FAAFP is a member of the following medical societies: American Academy of Family Physicians, American College of Sports Medicine, American Heart Association, American Medical Society for Sports Medicine, and North American Primary Care Research Group

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Jon B Whitehurst, MD  Clinical Instructor of Surgery, University of Illinois College of Medicine; Partner, Rockford Orthopedic Associates; Orthopedic Chairman, Rockford Memorial Hospital

Jon B Whitehurst, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Society for Sports Medicine, and Arthroscopy Association of North America

Disclosure: Nothing to disclose.

Chief Editor

Sherwin SW Ho, MD  Associate Professor, Department of Surgery, Section of Orthopedic Surgery and Rehabilitation Medicine, University of Chicago Division of the Biological Sciences, The Pritzker School of Medicine

Sherwin SW Ho, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Society for Sports Medicine, Arthroscopy Association of North America, and Herodicus Society

Disclosure: Breg, Inc. Consulting fee Consulting; Biomet, Inc. Consulting fee Consulting; GMV, Inc. Arthroscopy Simulator Evaluation and teaching; Smith and Nephew Grant/research funds Fellowship funding; DJ Ortho Grant/research funds Course funding; Athletico Physical Therapy Grant/research funds Course, research funding

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