At least 41 systems measure the severity, or grade, of a mild head injury, and there is little agreement about which is best. In an effort to simplify, the 2nd International Conference on Concussion in Sport, meeting in Prague in 2004, decided that these systems should be abandoned in favor of a 'simple' or 'complex' classification. However, the 2008 meeting in Zurich abandoned the simple versus complex terminology, although the participants did agree to keep the concept that most (80–90%) concussions resolve in a short period (7–10 days), and although the recovery time frame may be longer in children and adolescents.
In the past, the decision to allow athletes to return to participation was frequently based on the grade of concussion. However, current research and recommendations by professional organizations including the "National Athletic Trainers' Association recommend against such use of these grading systems. Currently, injured athletes are prohibited from returning to play before they are symptom-free during both rest and exertion and until results of the "neuropsychological tests have returned to pre-injury levels.
Three grading systems have been most widely followed: by Robert Cantu, the "Colorado Medical Society, and the "American Academy of Neurology. Each employs three grades, as summarized in the following table:
|Guidelines||Grade I||Grade II||Grade III|
|Cantu||Post-traumatic amnesia <30 minutes, no loss of consciousness||Loss of consciousness <5 minutes or amnesia lasting 30 minutes–24 hours||Loss of consciousness >5 minutes or amnesia >24 hours|
|Colorado Medical Society||Confusion, no loss of consciousness||Confusion, post-traumatic amnesia, no loss of consciousness||Any loss of consciousness|
|American Academy of Neurology||Confusion, symptoms last <15 minutes, no loss of consciousness||Symptoms last >15 minutes, no loss of consciousness||Loss of consciousness (IIIa, coma lasts seconds, IIIb for minutes)|
Prevention of MTBI involves general measures such as wearing "seat belts and using "airbags in cars. Older people are encouraged to reduce fall risk by keeping floors free of clutter and wearing thin, flat, shoes with hard soles that do not interfere with balance.
Protective equipment such as headgear has been found to reduce the number of concussions in athletes and improvements in the design of helmets may decrease the number and severity further. New "Head Impact Telemetry System" technology is being placed in helmets to study injury mechanisms and may generate knowledge that will potentially help reduce the risk of concussions among American Football players. Self-reported concussion rates among U-20 and elite rugby union players in Ireland are 45-48%. Half of these injuries go unreported. Changes to the rules or enforcing existing rules in sports, such as those against "head-down tackling", or "spearing", which is associated with a high injury rate, may also prevent concussions.
After exclusion of neck injury, observation should be continued for several hours. If repeated vomiting, worsening headache, dizziness, seizure activity, excessive drowsiness, double vision, slurred speech, unsteady walk, or weakness or numbness in arms or legs, or signs of "basilar skull fracture develop, immediate assessment in an emergency department is warranted. After this initial period has passed, there is debate as to whether it is necessary to awaken the person several times during the first night, as has traditionally been done, or whether there is more benefit from uninterrupted sleep.
Physical and cognitive rest should be continued until all symptoms have resolved with most (80–90%) concussions resolving in seven to ten days, although the recovery time may be longer in children and adolescents. Cognitive rest includes reducing activities which require concentration and attention such as school work, video games, and text messaging. It has been suggested that even leisure reading can commonly worsen symptoms in children and adolescents and proposals include time off from school and attending partial days. Since students may appear 'normal', continuing education of relevant school personnel may be needed.
Those with concussion are generally prescribed rest, including adequate nighttime sleep as well as daytime rest. Rest includes both physical and cognitive rest until symptoms clear and a gradual return to normal activities at a pace that does not cause symptoms to worsen is recommended. Education about symptoms, their management, and their normal time course, can lead to an improved outcome.
For persons participating in athletics, the 2008 Zurich Consensus Statement on Concussion in Sport recommends that participants be symptom free before restarting and then progress through a series of graded steps. These steps include:
- complete physical and cognitive rest
- light aerobic activity (less than 70% of maximum heart rate)
- sport-specific activities such as running drills and skating drills
- non-contact training drills (exercise, coordination, and cognitive load)
- full-contact practice
- full-contact games.
Only when symptom-free for 24 hours, should progression to the next step occur. If symptoms occur, the person should drop back to the previous asymptomatic level for at least another 24 hours. The emphasis is on remaining symptom free and taking it in medium steps, not on the steps themselves.
Medications may be prescribed to treat sleep problems and depression. "Analgesics such as "ibuprofen can be taken for headache, but "paracetamol (acetaminophen) is preferred to minimize the risk of intracranial hemorrhage. Concussed individuals are advised not to use "alcohol or other "drugs that have not been approved by a doctor as they can impede healing. Activation database-guided EEG biofeedback has been shown to return the memory abilities of the concussed individual to levels better than the control group.
About one percent of people who receive treatment for MTBI need surgery for a brain injury. Observation to monitor for worsening condition is an important part of treatment. "Health care providers recommend that those suffering from concussion return for further medical care and evaluation 24 to 72 hours after the concussive event if the symptoms worsen. Athletes, especially intercollegiate or "professional, are typically followed closely by team athletic trainers during this period but others may not have access to this level of health care and may be sent home with minimal monitoring.
People may be released after assessment from hospital or emergency room to the care of a trusted person with instructions to return if they display worsening symptoms or those that might indicate an emergent condition such as: change in consciousness, convulsions, severe headache, extremity weakness, vomiting, new bleeding or deafness in either or both ears.
People who have had a concussion seem more susceptible to another one, particularly if the new injury occurs before symptoms from the previous concussion have completely gone away. It is also a negative process if smaller impacts cause the same symptom severity. Repeated concussions may increase a person's risk in later life for dementia, Parkinson's disease, and depression.
MTBI has a mortality rate of almost zero. The symptoms of most concussions resolve within weeks, but problems may persist. These are seldom permanent, and outcome is usually excellent. The overall prognosis for recovery may be influenced by a variety of factors that include age at the time of injury, intellectual abilities, family environment, social support system, occupational status, coping strategies, and financial circumstances. People over age 55 may take longer to heal from MTBI or may heal incompletely. Similarly, factors such as a previous head injury or a coexisting medical condition have been found to predict longer-lasting post-concussion symptoms. Other factors that may lengthen recovery time after MTBI include psychological problems such as "substance abuse or "clinical depression, poor health before the injury or additional injuries sustained during it, and life stress. Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms. For unknown reasons, having had one concussion significantly increases a person's risk of having another. Having previously sustained a sports concussion has been found to be a strong factor increasing the likelihood of a concussion in the future. Other strong factors include participation in a contact sport and body mass size. The prognosis may differ between concussed adults and children; little research has been done on concussion in the "pediatric population, but concern exists that severe concussions could interfere with "brain development in children.
A 2009 study found that individuals with a history of concussions might demonstrate a decline in both physical and mental performance for longer than 30 years. Compared to their peers with no history of brain trauma, sufferers of concussion exhibited effects including loss of "episodic memory and "reduced muscle speed.
In post-concussion syndrome, symptoms do not resolve for weeks, months, or years after a concussion, and may occasionally be permanent. About 10% to 20% of people have post concussion syndrome for more than a month. Symptoms may include headaches, dizziness, fatigue, "anxiety, memory and attention problems, sleep problems, and irritability. There is no scientifically established treatment, and rest, a recommended recovery technique, has limited effectiveness. Symptoms usually go away on their own within months. The question of whether the syndrome is due to structural damage or other factors such as psychological ones, or a combination of these, has long been the subject of debate.
Cumulative effects of concussions are poorly understood, with this being even more true in children. The severity of concussions and their symptoms may worsen with successive injuries, even if a subsequent injury occurs months or years after an initial one. Symptoms may be more severe and changes in "neurophysiology can occur with the third and subsequent concussions. Studies have had conflicting findings on whether athletes have longer recovery times after repeat concussions and whether cumulative effects such as impairment in cognition and memory occur.
Cumulative effects may include "psychiatric disorders and loss of "long-term memory. For example, the risk of developing clinical depression has been found to be significantly greater for retired "American football players with a history of three or more concussions than for those with no concussion history. Three or more concussions is also associated with a fivefold greater chance of developing "Alzheimer's disease earlier and a threefold greater chance of developing "memory deficits.
Chronic traumatic encephalopathy, or "CTE", is an example of the cumulative damage that can occur as the result of multiple concussions or less severe blows to the head. The condition was previously referred to as ""dementia pugilistica", or "punch drunk" syndrome, as it was first noted in boxers. The disease can lead to cognitive and physical handicaps such as "parkinsonism, speech and memory problems, slowed mental processing, tremor, depression, and inappropriate behavior. It shares features with Alzheimer's disease.
Second-impact syndrome, in which the brain swells dangerously after a minor blow, may occur in very rare cases. The condition may develop in people who receive a second blow days or weeks after an initial concussion, before its symptoms have gone away. No one is certain of the cause of this often fatal complication, but it is commonly thought that the swelling occurs because the brain's "arterioles lose the ability to regulate their diameter, causing a loss of control over cerebral blood flow. As the brain "swells, intracranial pressure rapidly rises. The brain can "herniate, and the brain stem can fail within five minutes. Except in boxing, all cases have occurred in athletes under age 20. Due to the very small number of documented cases, the diagnosis is controversial, and doubt exists about its validity. A 2010 Pediatrics review article stated that there is debate whether the brain swelling is due to two separate hits or to just one hit, but in either case, catastrophic football head injuries are three times more likely in high school athletes than in college athletes.
Most cases of traumatic brain injury are concussions. A World Health Organization (WHO) study estimated that between 70 and 90% of head injuries that receive treatment are mild. However, due to underreporting and to the widely varying definitions of concussion and MTBI, it is difficult to estimate how common the condition is. Estimates of the incidence of concussion may be artificially low, for example due to underreporting. At least 25% of MTBI sufferers fail to get assessed by a medical professional. The WHO group reviewed studies on the epidemiology of MTBI and found a hospital treatment rate of 1–3 per 1000 people, but since not all concussions are treated in hospitals, they estimated that the rate per year in the general population is over 6 per 1000 people.
Young children have the highest concussion rate among all age groups. However, most people who suffer concussion are young adults. A Canadian study found that the yearly "incidence of MTBI is lower in older age groups (graph at right). Studies suggest males suffer MTBI at about twice the rate of their female counterparts. However, female athletes may be at a higher risk for suffering concussion than their male counterparts.
Up to five percent of "sports injuries are concussions. The U.S. "Centers for Disease Control and Prevention estimates that 300,000 sports-related concussions occur yearly in the U.S., but that number includes only athletes who lost consciousness. Since loss of consciousness is thought to occur in less than 10% of concussions, the CDC estimate is likely lower than the real number. Sports in which concussion is particularly common include football and boxing (a boxer aims to ""knock out", i.e. give a mild traumatic brain injury to, the opponent). The injury is so common in the latter that several medical groups have called for a ban on the sport, including the American Academy of Neurology, the "World Medical Association, and the medical associations of the UK, the U.S., Australia, and Canada.
Due to the lack of a consistent definition, the economic costs of MTBI are not known, but they are estimated to be very high. These high costs are due in part to the large percentage of hospital admissions for head injury that are due to mild head trauma, but indirect costs such as lost work time and early retirement account for the bulk of the costs. These direct and indirect costs cause the expense of mild brain trauma to rival that of moderate and severe head injuries.
The Hippocratic Corpus, collection of medical works from ancient Greece, mentions concussion, later translated to commotio cerebri, and discusses loss of speech, hearing and sight that can result from "commotion of the brain". This idea of disruption of mental function by "shaking of the brain" remained the widely accepted understanding of concussion until the 19th century. The Persian physician "Muhammad ibn Zakarīya Rāzi was the first to write about concussion as distinct from other types of head injury in the 10th century AD. He may have been the first to use the term "cerebral concussion", and his definition of the condition, a transient loss of function with no physical damage, set the stage for the medical understanding of the condition for centuries. In the 13th century, the physician "Lanfranc of Milan's Chiurgia Magna described concussion as brain "commotion", also recognizing a difference between concussion and other types of traumatic brain injury (though many of his contemporaries did not), and discussing the transience of post-concussion symptoms as a result of temporary loss of function from the injury. In the 14th century, the surgeon "Guy de Chauliac pointed out the relatively good prognosis of concussion as compared to more severe types of head trauma such as "skull fractures and "penetrating head trauma. In the 16th century, the term "concussion" came into use, and symptoms such as confusion, lethargy, and memory problems were described. The 16th century physician "Ambroise Paré used the term commotio cerebri, as well as "shaking of the brain", "commotion", and "concussion".
Until the 17th century, concussion was usually described by its clinical features, but after the invention of the microscope, more physicians began exploring underlying physical and structural mechanisms. However, the prevailing view in the 17th century was that the injury did not result from physical damage, and this view continued to be widely held throughout the 18th century. The word "concussion" was used at the time to describe the state of unconsciousness and other functional problems that resulted from the impact, rather than a physiological condition.
In 1839, Guillaume Dupuytren described brain contusions, which involve many small hemorrhages, as contusio cerebri and showed the difference between unconsciousness associated with damage to the brain "parenchyma and that due to concussion, without such injury. In 1941, animal experiments showed that no "macroscopic damage occurs in concussion.
Society and culture
The terms mild brain injury, mild traumatic brain injury (MTBI), mild head injury (MHI), and concussion may be used interchangeably, although the last is often treated as a narrower category. Although the term "concussion" is still used in sports literature as interchangeable with "MHI" or "MTBI", the general clinical medical literature now uses "MTBI" instead. In this article, "concussion" and "MTBI" are used interchangeably.
The term is from the "Latin concutere meaning "to shake violently" or concussus meaning "action of striking together".
"Minocycline, "lithium and "N-acetylcysteine show tentative success in animal models.
Measurement of predictive visual tracking is being studied as a screening technique to identify mild traumatic brain injury. A "head-mounted display unit with "eye-tracking capability shows a moving object in a predictive pattern for the person to follow with their eyes. People without brain injury will be able to track the moving object with "smooth pursuit eye movements and correct "trajectory while it is hypothesized that those with mild traumatic brain injury cannot.
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- "Facts about Concussion and Brain Injury and Where to Get Help" "US Centers for Disease Control and Prevention
- "Concussion in High School Sports" "US Centers for Disease Control and Prevention
- Concussions and Our Kids: America's Leading Expert On How To Protect Young Athletes and Keep Sports Safe, Robert Cantu, M.D. and Mark Hyman, New York: Houghton Mifflin Harcourt, 2012. Dr. Cantu is a neurologist and Mr. Hyman, a sports journalist. They have written a book for the interested layperson.