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'''Concussion''', from the [[Latin]] ''concussus'' ("to shake violently"),<ref name=cobb/> is the most common and least serious type of [[traumatic brain injury]]. The terms '''mild brain injury''', '''mild traumatic brain injury''', '''mild head injury''', and '''minor head trauma''' may be used interchangeably with concussion,<ref name="ncipc"/> but the latter is often treated as a narrower category.<ref name="BazarianJJ"/><ref name=sivak/> Commonly defined as a [[head injury]] with a transient loss of [[brain function]], concussion can cause a variety of physical, [[cognition|cognitive]], and emotional symptoms. The most often affected mental faculties are memory, attention, speed of information processing, and reaction time to stimuli.<ref name=moser>
'''Concussion''', from the [[Latin]] ''concussus'' ("to shake violently"),<ref name=cobb/> is the most common and least serious type of [[traumatic brain injury]]. The terms '''mild brain injury''', '''mild traumatic brain injury''', '''mild head injury''', and '''minor head trauma''' may be used interchangeably with concussion,<ref name="ncipc"/> but the latter is often treated as a narrower category.<ref name="BazarianJJ"/><ref name=sivak/> Commonly defined as a [[head injury]] with a transient loss of [[brain function]], concussion can cause a variety of physical, [[cognition|cognitive]], and emotional symptoms. The most often affected mental faculties include memory, attention, and speed of information processing.<ref name=moser>
{{
{{
cite journal|author=Moser RS, Iverson GL, Echemendia RJ, Lovell MR, Schatz P, Webbe FM ''et al.'' |date=2007 |title=Neuropsychological Evaluation in the Diagnosis and Management of Sports-Related Concussion |journal=Archives of Clinical Neuropsychology |volume=22 |issue=8 |pages=909–916 |pmid=17988831
cite journal|author=Moser RS, Iverson GL, Echemendia RJ, Lovell MR, Schatz P, Webbe FM ''et al.'' |date=2007 |title=Neuropsychological Evaluation in the Diagnosis and Management of Sports-Related Concussion |journal=Archives of Clinical Neuropsychology |volume=22 |issue=8 |pages=909–916 |pmid=17988831

Revision as of 22:44, 2 February 2008

"Cerebral Concussion" redirects here. For the band, see Devilyn.
Concussion
SpecialtyEmergency medicine, neurology Edit this on Wikidata

Concussion, from the Latin concussus ("to shake violently"),[1] is the most common and least serious type of traumatic brain injury. The terms mild brain injury, mild traumatic brain injury, mild head injury, and minor head trauma may be used interchangeably with concussion,[2] but the latter is often treated as a narrower category.[3][4] Commonly defined as a head injury with a transient loss of brain function, concussion can cause a variety of physical, cognitive, and emotional symptoms. The most often affected mental faculties include memory, attention, and speed of information processing.[5] Concussion may be caused by a blow to the head, or by acceleration or deceleration forces without a direct impact. Common causes include falls, motor vehicle accidents, and sports injuries.

Concussion can be diagnosed and assigned a level of severity based largely on symptoms. Treatment involves monitoring and rest. Symptoms usually go away entirely within three weeks, though they may persist, or complications may occur.[6] Repeated concussions can cause permanent, cumulative brain damage such as dementia pugilistica or severe complications such as second-impact syndrome.

A debate has long existed about whether the concussed brain is structurally damaged the way it is in other types of brain injury (albeit to a lesser extent) or whether concussion mainly entails a loss of function without structural changes.[7]

Definition

Concussion has been defined in several ways, with no single definition being universally accepted.[8] In 2001, a group of concussion experts defined the injury as "a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces."[9][10] 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.[6]

This definition of concussion as a clinical entity in which mental function is temporarily impaired after an impact is widely accepted.[8] According to the classic definition, no structural brain damage occurs in concussion;[11] 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.[6] However, in recent years researchers have included injuries in which structural damage does occur under the rubric of concussion. According to the National Institute for Health and Clinical Excellence definition, concussion may involve a physiological or physical disruption in the brain's synapses.[12]

In the 1990s, researchers began treating "mild traumatic brain injury" (mTBI) and "concussion" as synonyms, because the former has easily identifiable criteria, which can aid in creating consistency among multi-center studies.[13] However, mTBI has classically been defined as a traumatic brain injury associated with a Glasgow Coma score of 13 or higher,[2] which does not necessarily address the other criteria for concussion. In addition, other injuries such as intracranial hemorrhages (e.g. intra-axial hematoma, epidural hematoma, and subdural hematoma) are not necessarily precluded in mTBI.[6] "Concussion" can be considered to imply a state in which brain function is temporarily impaired and "mTBI" to imply a pathophysiological state, but in practice few researchers and clinicians distinguish between the terms.[6] It is not clear whether concussion is implied in mild brain injury or mild head injury.[14]

Controversy exists about whether the definition of concussion should include only those injuries in which loss of consciousness occurs.[15] The U.S. Centers for Disease Control and Prevention (CDC) and the American Academy of Neurology do not require a loss of consciousness for the diagnosis.[8][16] 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.[1]

Epidemiology

Most cases of traumatic brain injury are concussions. In the U.S., more than 85% of traumatic brain injuries are mild, with the yearly incidence of concussion at about 128 people per 100,000.[3] The lack of the highly noticeable signs and symptoms, such as coma, frequently present in other forms of head injury, could lead clinicians to miss the injury; this possibility has led to the suspicion that concussion may be under-diagnosed.[5][8] Underreporting may be another factor in an artificially low estimate of incidence; according to the CDC, less than a third of people with concussion see a doctor for it.[17]

Concussion primarily affects the young.[18] A U.S. study found that children under five had the highest rate of mTBI.[3] Another study found that the incidence of mTBI in Canada was 200 per 100,000 in people younger than 14 years; 160 per 100,000 in those aged 15 to 34; and 50 per 100,000 in those over 35.[19] Young people may be more likely to suffer concussion after a given blow than their older counterparts, and they may be at increased risk for suffering cumulative effects.[20]

Males suffer more concussions than females, especially among young adults.[19] However, in high school sports played by both sexes, a 2007 study found that girls reported suffering concussions at a greater rate and as a higher percentage of all injuries than did their male counterparts.[21]

Causes

A group studied records from 1338 Ontario school children with symptoms of concussion from recreation-related trauma and found that falls were the leading cause of the injury.[22]

Common causes of concussions include sports injuries, assaults, bicycle accidents, auto accidents,[18] and falls, with the latter two being the most frequent causes among adults.[23] Soldiers are at elevated risk for concussion from causes such as bomb blasts, with as many as 15% of U.S. infantry soldiers who return from the Iraq War meeting the criteria for mTBI.[24] For school-age children, a Canadian study of found that the most common cause of head trauma with concussion symptoms was falls, followed by sports and then assaults or rough play.[17] Another study analyzed the causes of recreation-related concussion in school children as shown in the chart at right.

In another Canadian study, sports were responsible for over half of reported concussions, and over 85% of those for people between the ages of 16 and 34.[19] Up to five percent of sports injuries are concussions.[25] The CDC estimates that 300,000 sports-related concussions occur yearly in the U.S.,[17][26] but that number includes only athletes who lost consciousness.[17] Since loss of consciousness is thought to occur in less than 10% of concussions,[27] this is likely an underestimate.[28] 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). In fact, the injury is so common in the latter that several medical groups have called for a ban on the sport, including the World Medical Association and the American Academy of Neurology.[29]

Mechanism

The brain is surrounded by cerebrospinal fluid (CSF), one of the functions of which is to protect it from light trauma such as jostling from walking or jumping. More severe impacts or the forces associated with rapid acceleration and deceleration may not be absorbed by this cushion. Concussion may be caused by impact forces, in which the head strikes or is struck by something, or impulsive forces, in which the head moves without itself being subject to blunt trauma (for example, when the chest hits something and the head snaps forward).[4]

File:Boxing.png
Rotational force is key in concussion. Punches in boxing deliver more rotational force to the head than do impacts in sports such as football,[30][31] and boxing carries a higher risk of concussion than does football.[31]

Forces may cause linear, rotational, or angular movement of the brain, or a combination of these types of motion.[4] In rotational movement, the head turns around its center of gravity, whereas in angular movement it turns on an axis other than its center of gravity.[4] Rotational acceleration may cause parts of the brain to slide against each other, increasing shearing stress, the same mechanism that causes diffuse axonal injury.[32][33] The amount of rotational force, thought to be the major type of force to cause concussion,[34] is the largest component in the severity of the concussive injury.[6] A 2007 study with athletes showed that the amount of force and the location of the impact is not necessarily correlated to the severity of the concussion or its symptoms.[35] For example, while concussion occurred after an impact with a force of about 60g,[35] it did not necessarily occur even with much harder impacts.[36]

The parts of the brain most affected by rotational forces are the midbrain and diencephalon.[23] It is thought that the forces from the injury disrupt the normal cellular activities in the reticular activating system located in these areas, and that this disruption produces the loss of consciousness seen in concussion.[23] Other areas of the brain that may be affected by concussion include the upper part of the brain stem, the fornix, the corpus callosum, the temporal lobe, and the frontal lobe.[37]

Pathophysiology

Concussion can alter the brain's physiology for a period of weeks, setting into motion a variety of pathological events.[38][39] In a large majority of affected brain cells, the metabolic processes that follow concussion are reversed within hours or days; however a small number of cells may die after the injury.[5]

Concussion is thought to unleash a metabolic cascade of events including impaired neurotransmission, loss of regulation of ions, deregulation of energy use and cellular metabolism, and a reduction in cerebral blood flow.[5][8][38] Excitatory neurotransmitters such as glutamate are released in excessive amounts as the result of the injury[25] and lead to an imbalance of ions such as potassium and calcium across the cell membranes of neurons like that seen in excitotoxicity.[38] The ionic imbalance leads to neuronal depolarization, which in turn causes the sodium-potassium pump to work more than it normally does in an attempt to restore resting potential.[38] For this, the pump requires greater-than-usual amounts of ATP, which causes cells to enter a state of hypermetabolism (to use more glucose than usual).[38] At the same time, cerebral blood flow is relatively reduced,[40] leading to an energy crisis for cells.[38]

For a period of minutes to days after a concussion, the brain is especially vulnerable to changes in intracranial pressure, blood flow, and particularly anoxia.[40] According to studies performed on animals, large numbers of neurons can die during this period in response to slight, normally innocuous changes in blood flow.[40] Animal studies have also found that a second concussion occurring during this window of time has severe effects on metabolism within the brain.[41]

Concussion involves diffuse brain injury[42] (as opposed to focal brain injury), meaning that the dysfunction occurs over a widespread area of the brain rather than in a particular spot. Concussion is thought to be a milder type of diffuse axonal injury because axons may be injured to a minor extent due to stretching.[4][5] Axonal damage has been found in the brains of concussion sufferers who died from other causes.[33] A stretched or damaged axon may be further damaged or killed by fluctuations of ions across the axonal membrane in the hours and days following the injury.

Signs and symptoms

File:Knock out.jpg
A Pradal Serey kickboxer is knocked out, and his opponent is declared the winner of the match. Brief loss of consciousness is one symptom of concussion.

Concussion can be associated with a variety of symptoms, which typically occur rapidly after the injury and resolve quickly.[9]

Physical

Headache is the most common symptom to be reported,[43] and dizziness is among the most commonly reported.[44] Symptoms also include nausea, vomiting, lack of motor coordination,[45] lightheadedness, difficulty balancing, or other problems with movement or sensation.[40] Visual symptoms include blurred vision, seeing bright lights,[40] double vision,[33] or a traveling migraine aura. Tinnitus, or a ringing in the ears, is also commonly reported.[40] In one in about seventy concussions, concussive convulsions occur, but these are not actual post-traumatic epilepsy, which is a symptom of more serious injury.[46] Concussive convulsions are thought to result from temporary loss of brain function rather than from structural damage and do not increase the likelihood of a bad outcome.[46][47][48]

Cognitive and emotional

Cognitive symptoms include disorientation, delayed responses to stimuli, and difficulty focusing attention.[45] Loss of consciousness may occur but is not necessarily correlated with the severity of the concussion if it is brief.[10] Lethargy, fatigue,[40] or changes sleeping patterns are other symptoms.[49]

Confusion is one of the most common symptoms of concussion.[44] A patient may, for example, repeatedly ask the same questions, respond slowly to questions or directions,[49] have a vacant stare,[50] or forget where he or she is. Speech may be slurred or incoherent.[45] Other symptoms include difficulty with reasoning,[33] concentrating, and performing everyday activities.[40]

Like confusion, amnesia is a hallmark of concussion.[49][43] It may be the best predictor of long-term or permanent problems, though there is not universal agreement on this point.[40] There are two types of amnesia: retrograde amnesia (loss of memories that were formed shortly before the injury) and anterograde amnesia (problems with creating new memories post-injury).[40] Both retrograde and anterograde forms may be referred to as "post-traumatic amnesia",[40] or the term may be used to refer only to anterograde amnesia.[4] Frequently the last symptom to ameliorate after a loss of consciousness,[40] anterograde amnesia is more the more common type in concussion. Amnesia may not become apparent until a day to a week after the injury. A common example in sports concussion is the quarterback who was able to conduct the complicated mental tasks of leading a football team after a concussion, but has no recollection the next day of the part of the game that took place after the injury. Amnesia sufferers may partially regain memory later.[40]

Affective results of concussion include mood disturbances, depression,[51] irritability, crankiness, loss of interest in favorite activities or items,[52] restlessness, tearfulness,[4] and displays of emotion that are inappropriate to the situation.[45]

Diagnosis

Diagnosis may be based on physical examination, symptoms, neuropsychological tests,[53] and the Glasgow Coma Scale, with concussion patients usually scoring 13 to 15 on the scale.[18] Several types of neuropsychological tests exist to measure cognitive function, for example memory, learning, speed of responses to stimuli,[53] recall of words, and speed of word retrieval.[54] The tests may be administered hours, days, or weeks after the injury, or at different times to determine whether there is a trend in the patient's condition.[5] Athletes may be tested before a sports season begins to provide a baseline comparison in the event of an injury.[5][55]

Head trauma sufferers are examined by health care providers to ensure that the injury is not a more severe medical emergency such as an intracranial hemorrhage. Indications of a more serious injury include worsening of symptoms[56] such as headache,[50] increasing disorientation or a deteriorating level of consciousness, persistent vomiting,[57] seizures, and unequal pupil size.[58] Patients with such symptoms, or who are at higher risk for a more serious brain injury, are given MRIs or CT scans and are observed by medical staff.

Health care providers make the decision about whether to give a CT scan using the Glasgow Coma Scale.[23] 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,[23] or younger than 16. Most concussions cannot be detected with MRI or CT scans;[4][34] however, Diffusion-weighted MRI has detectected changes in brains of about one in five concussion victims.[42] Changes in brain physiology can be detected using SPECT and PET scans.[42]

A decision about the severity of a concussion is retrospective, because it can only be made once symptoms have resolved completely.[56]

Grades

At least 16 systems exist to determine the severity, or grade, of a concussion,[59] and there is little agreement among professionals about which is the best.[13][40] Several of the systems use loss of consciousness and amnesia as the primary determinants of the severity of the concussion.[40]

The decision about when to allow athletes to return to contact sports is frequently based on the grade of concussion.[60] Injured athletes are prohibited from returning to play before they are symptom-free during rest and exertion and their neuropsychological tests are normal again, in order to avoid a risk of cumulative effects such as decline in mental function and second-impact syndrome due to multiple concussions received in a short time.

Three grading systems are followed most widely: one was developed by Robert Cantu, one by the Colorado Medical Society,[1][61] and a third by the American Academy of Neurology.[1][50] Each divides concussion into three grades, as summarized in the following table:[40]

Comparison of concussion grading scales
  Grade I Grade II Grade III
Cantu guidelines Post-traumatic amnesia <30 minutes, no loss of consciousness Loss of consciousness <5 minutes or amnesia lasting between 30 minutes 24 hours Loss of consciousness >5 minutes or amnesia >24 hours
Colorado Medical Society guidelines Confusion, no loss of consciousness Confusion, post-traumatic amnesia, no loss of consciousness Any loss of consciousness
American Academy of Neurology guidelines 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)

Cantu guidelines

The Cantu guidelines, published in 1986,[40] classify an injury associated with no loss of consciousness and less than 30 minutes of post-traumatic amnesia as grade I. In grade II, the patient loses consciousness for less than 5 minutes or experiences amnesia for between 30 minutes and 24 hours. In grade III, loss of consciousness lasts longer than 5 minutes or amnesia lasts longer than 24 hours.[40] The most commonly seen type of concussion is a grade I by this guideline.[42]

In a 2001 update, Cantu changed the guidelines to include other concussion signs and symptoms in addition to amnesia in the grading criteria.[40] He also changed the grade II criteria to include only concussions with loss of consciousness for less than 1 minute, and included those with loss of consciousness for greater than 1 minute, or with signs or symptoms lasting over a week, under grade III.[40] More than one grade III concussion during a professional or collegiate athlete's carreer may lead health professionals to recommend that the player cease playing the sport.[42]

Colorado Medical Society guidelines

The Colorado Medical Society guidelines were published in 1991 in response to the death of a high school student due to what was thought to be second-impact syndrome.[8] According to the guidelines, a grade I concussion consists of confusion only, grade II includes confusion and post-traumatic amnesia, and grade III involves a loss of consciousness.[40]

By these guidelines, an athlete who has suffered a concussion may return to sports after having been free of symptoms, both at rest and during exercise, as shown in the following table:[60][62]

Colorado Medical Society guidelines for return to play
Grade First concussion Subsequent concussions
I 15 minutes 1 week
II 1 week 2 weeks
III (unconscious
for seconds) 		1 week 1 month, with
physician approval
III (unconscious
for minutes) 		2 weeks 1 month, with
physician approval

American Academy of Neurology guidelines

The guidelines devised in 1997 by the American Academy of Neurology (AAN) are based on those by the Colorado Medical Society.[63] According to these guidelines, a grade I concussion is associated with no loss of consciousness and symptoms of confusion last less than 15 minutes. Grade II is the same, except symptoms last longer than 15 minutes. In grade III, loss of consciousness does occur.[40] Grade III can be further divided into grades IIIa and IIIb, with brief loss of consciousness (measured in seconds) and prolonged loss of consciousness (measured in minutes) respectively.[60] According to the AAN, permanent brain injury can occur with either Grade II or Grade III concussion.

By these guidelines, an athlete suffering a single, grade I concussion is given a neurological evaluation every five minutes starting immediately after the injury and may return to the competition if signs and symptoms resolve within a quarter of an hour.[49] Otherwise, the return to play rules are the same for the AAN and Colorado Medical Society guidelines.[49][60][62]

Prevention

Further information: Bicycle helmet, Football helmet, Hockey helmet, Motorcycle helmet, and Ski helmet

Prevention of concussion involves taking general measures to prevent traumatic brain injury, such as wearing seat belts. Older people are encouraged to try to prevent falls, for example by keeping floors free of clutter and wearing thin, flat, shoes with hard soles that do not interfere with balance.[52]

Use of protective equipment such as headgear has been found to reduce the number concussions in athletes.[31][64] Improvements in the design of protective athletic gear such as helmets may decrease the number of concussions athletes suffer.[65] Changes to the rules or the practices of enforcing existing rules in sports,[10] such as those against "head-down tackling", or "spearing", which is associated with a high injury rate, may also prevent concussions.[31]

Treatment

Usually symptoms go away without any treatment,[66][67] and there is no specific treatment for concussion. Traditionally, rest is prescribed,[68] including plenty of sleep at night plus rest during the day.[58] Health care providers recommend a gradual return to normal activities at a pace that does not cause symptoms to worsen.[58] Medications may be prescribed to treat symptoms such as sleep problems.[56] Analgesics such as acetaminophen can be taken for the headaches that frequently occur after concussion.[66] Concussed individuals are advised not to drink alcohol or take drugs that have not been approved by a doctor, as they could impede healing.[58]

Observation to monitor for worsening condition is an important part of treatment.[69] 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[23] or those which might indicate an emergent condition, like unconsciousness or altered mental status; convulsions; severe, persistent headache; extremity weakness; vomiting; or new bleeding or deafness in either or both ears.[70] Doctors recommend that the patient be observed repeatedly for the first 24 hours after concussion; however it is not known whether it is necessary to wake them up every few hours.[23]

Prognosis and lasting effects

The symptoms of most concussions are resolved within days or weeks,[24] but problems may persist.[56] Older people may take longer to heal from a concussion, as do those who have suffered a previous head injury[18] or have another, preexisting medical condition.[58] For unknown reasons, having had one concussion significantly increases a person's risk of having another.[5][43] Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms.[71]

The prognosis may differ between adults and children.[5] Little research has been done on concussion in the pediatric population, but concern exists that severe concussions could interfere with brain development in children.[5]

Post-concussion syndrome

Main article: Post-concussion syndrome

In post-concussion syndrome, symptoms do not resolve for weeks, months, or, in a small number of cases, years after a concussion. Symptoms, which usually peak four to six weeks after the concussion, may include headaches, light and sound sensitivity, memory and attention problems, dizziness, difficulty with directed movements, clinical depression, and anxiety. Physical therapy plus rest is the recommended recovery technique, and symptoms usually go away on their own. The question of whether the syndrome is due to structural damage or other factors such as psychological ones has long been the subject of intense debate.

Cumulative effects

Though cumulative effects are poorly understood,[72] 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.[73] Symptoms may be more severe and and changes in neurophysiology can occur with the third and subsequent concussions.[5] Studies have had conflicting findings on whether athletes have longer recovery times after repeat concussions[5][31][43] and whether cumulative effects occur. Athletes who have had multiple concussive injuries have been found to score lower on tests that examine cognition[74] and memory,[75] but a study published in 2006 did not show a link between repeat injuries and more severe concussions or symptoms.[31]

Cumulative effects may include psychiatric disorders and loss of long-term memory. For example, a 2007 study found that the risk of developing clinical depression was three times greater for retired football players with a history of three or more concussions than for those with no concussion history.[76] Study findings suggest a link between repeat concussions and earlier onset of Alzheimer's disease, but multiple concussions and the eventual development of the disease have not been conclusively shown to be linked.[72]

Dementia pugilistica

Main article: Dementia pugilistica

Chronic encephalopathy 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 called dementia pugilistica, or "punch drunk" syndrome, which is associated with boxers, can result in cognitive and physical deficits such as parkinsonism, speech problems, tremor, and inappropriate behavior. It shares features with Alzheimer's disease.

Second-impact syndrome

Main article: 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. 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.[5] The brain swells, intracranial pressure rapidly rises, and the brain can herniate. The brain stem can fail within five minutes.[27] Almost 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 the existence of the syndrome.

History and controversy

The Hippocratic Corpus mentioned concussion.[71]

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".[71] This idea of disruption of mental function by 'shaking of the brain' was the widely accepted understanding of concussion until the 19th century.[71] 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.[7] 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.[4] In the 13th centrury, the physician Lanfranc of Milan 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.[7] 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.[7] In the 16th century, the term "concussion" came into use, and symptoms such as confusion, lethargy, and memory problems were described.[7] The 16th century physician Ambroise Paré used the term commotio cerebri,[4] as well as "shaking of the brain", "commotion", and "concussion".[71]

Guillaume Dupuytren distinguished between concussion and unconsciousness associated with brain contusion.[71]

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.[7] 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.[7] 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.[7]

In 1839, Guillaume Dupuytren described brain injuries with many small hemorrhages (brain contusions) as contusio cerebri and showed the difference between unconsciousness associated with damage to the brain parenchyma and unconsciousness due to concussion, without such injury.[71] In 1941, animal experiments showed that no macroscopic damage occurs in concussion.[77]

The debate over whether concussion is a functional or structural phenomenon is ongoing today.[7] Researchers have claimed to have found structural damage in concussed brains.[5] Such changes in brain structure could be responsible for certain symptoms such as visual disturbances, but other sets of symptoms, especially psychological ones, are more likely to be caused by reversible pathophysiological changes in cellular function that occur after concussion, such as alterations in neurons' biochemistry.[6] These reversible changes could also explain why dysfunction is frequently temporary.[7] 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."[4][9]

References

  1. ^ a b c d Cobb S, Battin B (2004). "Second-Impact Syndrome". The Journal of School Nursing. 20 (5): 262–267. PMID 15469376.
  2. ^ a b National Center for Injury Prevention and Control (2003). "Report to Congress on Mild Traumatic Brain Injury in the United States: Steps to Prevent a Serious Public Health Problem" (PDF). Atlanta, GA: Centers for Disease Control and Prevention. Retrieved 2008-01-19. {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ a b c Bazarian JJ, McClung J, Shah MN, Cheng YT, Flesher W, Kraus J (2005). "Mild Traumatic Brain Injury in the United States, 1998-2000". Brain Injury. 19 (2): 85–91. PMID 15841752.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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