AskDefine | Define concussion

Dictionary Definition



1 injury to the brain caused by a blow; usually resulting in loss of consciousness
2 any violent blow

User Contributed Dictionary



  1. a violent collision or shock
  2. an injury to part of the body, most especially the brain, caused by a violent blow, followed by loss of function


a violent collision or shock
an injury to part of the body, most especially the brain

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Extensive Definition

Concussion, from the Latin concutere ("to shake violently"), is the most common and least serious type of traumatic brain injury. The terms mild brain injury, mild traumatic brain injury (MTBI), mild head injury (MHI), and minor head trauma and concussion may be used interchangeably, Repeated concussions can cause cumulative brain damage such as dementia pugilistica or severe complications such as second-impact syndrome.
Due to factors such as widely varying definitions and possible underreporting of concussion, the rate at which it occurs annually is not known; however it may be more than 6 per 1000 people. Cellular damage has reportedly been found in concussed brains, but it may have been due to artifacts from the studies. or mild traumatic brain injury is universally accepted, though a variety of definitions have been offered. In 2001, the first International Symposium on Concussion in Sport was organized by the International Olympic Committee Medical Commission and other sports federations. They agreed that concussion typically involves temporary impairment of neurological function which quickly resolves by itself, and that neuroimaging normally shows no gross structural changes to the brain as the result of the condition. it is a functional state, meaning that symptoms are caused primarily by temporary biochemical changes in neurons, taking place for example at their cell membranes and synapses.
Definitions of mild traumatic brain injury (M.T.B.I) have been inconsistent since the 1970s, but the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD-10) described MTBI-related conditions in 1992, providing a consistent, authoritative definition across specialties. In 1994, the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders defined MTBI using PTA and LOC. It is not clear whether concussion is implied in mild brain injury or mild head injury. "MTBI" and "concussion" are often treated as synonyms in medical literature. but they are in concussion. MTBI associated with abnormal neuroimaging may be considered "complicated MTBI".
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.
Controversy exists about whether the definition of concussion should include only those injuries in which loss of consciousness occurs. The best-known concussion grading scales count head injuries in which loss of consciousness does not occur to be mild concussions and those in which it does to be more severe.
The relative contribution of causes of mild head injury differs by region, gender, and age.
The parts of the brain most affected by rotational forces are the midbrain and diencephalon.


In both animals and humans, MTBI can alter the brain's physiology for hours to weeks, setting into motion a variety of pathological events. Though these events are thought to interfere with neuronal and brain function, the metabolic processes that follow concussion are reversed in a large majority of affected brain cells; however a few cells may die after the injury. This creates an imbalance of ions such as potassium and calcium across the cell membranes of neurons (a process like excitotoxicity). Concussion is thought to be a milder type of diffuse axonal injury because axons may be injured to a minor extent due to stretching. Axonal damage has been found in the brains of concussion sufferers who died from other causes, but inadequate blood flow to the brain due to other injuries may have contributed to the damage.

Signs and symptoms

Health care providers examine head trauma survivors to ensure that the injury is not a more severe medical emergency such as an intracranial hemorrhage. Indications that screening for more serious injury is needed include worsening of symptoms such as headache, persistent vomiting, increasing disorientation or a deteriorating level of consciousness, seizures, and unequal pupil size. Patients with such symptoms, or who are at higher risk for a more serious brain injury, are given MRIs or CT scans to detect brain lesions and are observed by medical staff.
Health care providers make the decision about whether to give a CT scan using the Glasgow Coma Scale. In addition, they may be more likely to perform a CT scan on people who would be difficult to observe after discharge or those who are intoxicated, at risk for bleeding, older than 60, However, changes have been reported to show up on MRI and SPECT imaging in concussed people with normal CT scans, and post-concussion syndrome may be associated with abnormalities visible on SPECT and PET scans.
Concussion may be under-diagnosed. The lack of the highly noticeable signs and symptoms that are frequently present in other forms of head injury could lead clinicians to miss the injury, and athletes may cover up their injuries in order to be allowed to remain in the competition.
Diagnosis of concussion can be complicated because it shares symptoms with other conditions. For example, post-concussion symptoms such as cognitive problems may be misattributed to brain injury when they are in fact due to post-traumatic stress disorder (PTSD). Several of the systems use loss of consciousness and amnesia as the primary determinants of the severity of the concussion. Each divides concussion into three grades, as summarized in the following table:
Use of protective equipment such as headgear has been found to reduce the number of concussions in athletes. Changes to the rules or the practices of 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. and no specific treatment exists. Traditionally, concussion sufferers are prescribed rest, including plenty of sleep at night plus rest during the day. 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 athletes, are typically followed closely by team trainers during this period. But others may not have access to this level of health care and may be sent home with no medical person monitoring them unless the situation gets worse. Patients may be released from the hospital to the care of a trusted person with orders to return if they display worsening symptoms Repeated observation for the first 24 hours after concussion is recommended; however it is not known whether it is necessary to wake the patient up every few hours. Similarly, factors such as a previous head injury or a coexisting medical condition have been found to predict longer-lasting post-concussion symptoms. Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms. 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.

Cumulative effects

Cumulative effects of concussions are poorly understood. 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.
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 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 five-fold greater chance of developing Alzheimer's disease earlier and a three-fold greater chance of developing memory deficits. It shares features with Alzheimer's disease.

Second-impact syndrome

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.


[[Image:MTBI incidince bar graph.svg|thumb|right|210px|Annual incidence of MTBI by age group in Canada 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.
Young children have the highest concussion rate among all age groups. Studies suggest males suffer MTBI at about twice the rate of their female 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. 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,

History and controversy

thumb|right|The [[Hippocratic Corpus mentioned concussion. This idea of disruption of mental function by 'shaking of the brain' remained the widely accepted understanding of concussion until the 19th century. 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.
The debate over whether concussion is a functional or structural phenomenon is ongoing. Structural damage has been found in the mildly traumatically injured brains of animals, but it is not clear whether these changes would be applicable to humans. Such changes in brain structure could be responsible for certain symptoms such as visual disturbances, but other sets of symptoms, especially those of a psychological nature, are more likely to be caused by reversible pathophysiological changes in cellular function that occur after concussion, such as alterations in neurons' biochemistry. These reversible changes could also explain why dysfunction is frequently temporary. A task force of head injury experts called the Concussion In Sport Group met in 2001 and decided that "concussion may result in neuropathological changes but the acute clinical symptoms largely reflect a functional disturbance rather than structural injury."


concussion in Danish: Hjernerystelse
concussion in German: Schädel-Hirn-Trauma
concussion in Modern Greek (1453-): Εγκεφαλική διάσειση
concussion in French: Traumatisme crânien
concussion in Italian: Commozione cerebrale
concussion in Hebrew: זעזוע מוח
concussion in Kazakh: Ми соққы
concussion in Dutch: Hersenschudding
concussion in Japanese: 脳震盪
concussion in Norwegian: Hjernerystelse
concussion in Finnish: Aivotärähdys
concussion in Swedish: Hjärnskakning
concussion in Ukrainian: Струс мозку
concussion in Chinese: 腦震盪

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