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Second-impact syndrome (SIS) occurs when the brain swells rapidly, and catastrophically, after a person has a second
concussion A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include headache, dizziness, difficulty with thinking and concentration, sleep disturbances, a brief ...
before symptoms from an earlier one have subsided. This second blow may occur minutes, days, or weeks after an initial concussion, and even the mildest grade of concussion can lead to second impact syndrome. The condition is often fatal, and almost everyone who is not killed is severely disabled. The cause of SIS is uncertain, but it is thought that the brain's
arteriole An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillary, capillaries. Arterioles have vascular smooth muscle, muscular walls (usually only one to two layers of smoo ...
s lose their ability to regulate their
diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...
, and therefore lose control over
cerebral blood flow Cerebral circulation is the movement of blood through a network of cerebral arteries and veins supplying the brain. The rate of cerebral blood flow in an adult human is typically 750 milliliters per minute, or about 15% of cardiac output. ...
, causing massive
cerebral edema Cerebral edema is excess accumulation of fluid ( edema) in the intracellular or extracellular spaces of the brain. This typically causes impaired nerve function, increased pressure within the skull, and can eventually lead to direct compres ...
. In order to prevent SIS, guidelines have been established to prohibit athletes from returning to a game prematurely. For example, professionals recommend that athletes not return to play before symptoms of an initial head injury have resolved.


Signs and symptoms

SIS is a potential complication from an athlete returning to a game before symptoms from a minor head injury have subsided. Such symptoms include headache, cognitive difficulties, or visual changes. The initial injury may be a concussion, or it may be another, more severe, type of head trauma, such as
cerebral contusion Cerebral contusion (), a form of traumatic brain injury, is a bruise of the brain tissue. Like bruises in other tissues, cerebral contusion can be associated with multiple microhemorrhages, small blood vessel leaks into brain tissue. Contusion ...
. However, the first concussion need not be severe for the second impact to cause SIS. Also, the second impact may be very minor, even a blow such as an impact to the chest that causes the head to jerk, thereby transmitting forces of
acceleration In mechanics, acceleration is the Rate (mathematics), rate of change of the velocity of an object with respect to time. Acceleration is one of several components of kinematics, the study of motion. Accelerations are Euclidean vector, vector ...
to the
brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
.
Loss of consciousness Unconsciousness is a state in which a living individual exhibits a complete, or near-complete, inability to maintain an awareness of self and environment or to respond to any human or environmental stimulus. Unconsciousness may occur as the re ...
during the second injury is not necessary for SIS to occur.Shaffrey M, Farace E (2003)
Sports concussions and second impact syndrome
. University of Virginia health system. Retrieved on 2008-01-01.
Both injuries may take place in the same game. The athlete may continue playing in the game after the second concussion, and may walk off the field without assistance, but symptoms quickly progress and the condition can rapidly worsen. Neurological collapse can occur within a short period, with rapid onset of dilating pupils, loss of eye movement, unconsciousness, and respiratory failure. Failure of the
brain stem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is co ...
frequently occurs between two and five minutes after the second impact, and death can follow shortly. SIS is sometimes associated with a small
subdural hematoma A subdural hematoma (SDH) is a type of bleeding in which a collection of blood—usually but not always associated with a traumatic brain injury—gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrou ...
.


Risk factors

Second-impact syndrome shares all the risk factors of a concussion; that is, those who are at increased risk for a concussion are also at higher risk for SIS. Thus, people who participate in sports such as
boxing Boxing is a combat sport and martial art. Taking place in a boxing ring, it involves two people – usually wearing protective equipment, such as boxing glove, protective gloves, hand wraps, and mouthguards – throwing Punch (combat), punch ...
,
Association football Association football, more commonly known as football or soccer, is a team sport played between two teams of 11 Football player, players who almost exclusively use their feet to propel a Ball (association football), ball around a rectangular f ...
,
American football American football, referred to simply as football in the United States and Canada and also known as gridiron football, is a team sport played by two teams of eleven players on a rectangular American football field, field with goalposts at e ...
,
baseball Baseball is a bat-and-ball games, bat-and-ball sport played between two team sport, teams of nine players each, taking turns batting (baseball), batting and Fielding (baseball), fielding. The game occurs over the course of several Pitch ...
,
rugby Rugby may refer to: Sport * Rugby football in many forms: ** Rugby union: 15 players per side *** American flag rugby *** Beach rugby *** Mini rugby *** Rugby sevens, 7 players per side *** Rugby tens, 10 players per side *** Snow rugby *** Tou ...
,
basketball Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular Basketball court, court, compete with the primary objective of #Shooting, shooting a basketball (ball), basketball (appro ...
,
ice hockey Ice hockey (or simply hockey in North America) is a team sport played on ice skates, usually on an Ice rink, ice skating rink with Ice hockey rink, lines and markings specific to the sport. It belongs to a family of sports called hockey. Tw ...
,
pro wrestling Professional wrestling, often shortened to either pro wrestling or wrestling,The term "wrestling" is most often widely used to specifically refer to modern scripted professional wrestling, though it is also used to refer to real-life wrest ...
,
horse riding Equestrianism (from Latin , , , 'horseman', 'horse'), commonly known as horse riding ( Commonwealth English) or horseback riding (American English), includes the disciplines of riding, driving, and vaulting. This broad description includes the ...
, and
skiing Skiing is the use of skis to glide on snow for basic transport, a recreational activity, or a competitive winter sport. Many types of competitive skiing events are recognized by the International Olympic Committee (IOC), and the International S ...
(especially
Alpine Alpine may refer to any mountainous region. It may also refer to: Places Europe * Alps, a European mountain range ** Alpine states, which overlap with the European range Australia * Alpine, New South Wales, a Northern Village * Alpine National P ...
) are at increased risk. The condition most commonly occurs in American football. Second-impact syndrome disproportionately affects teenagers. All documented cases occurred in people younger than 20 except in
boxing Boxing is a combat sport and martial art. Taking place in a boxing ring, it involves two people – usually wearing protective equipment, such as boxing glove, protective gloves, hand wraps, and mouthguards – throwing Punch (combat), punch ...
. As of 2000, the syndrome had never been reported in the medical literature in children younger than adolescent age. Young athletes have been found to be both more susceptible to concussions and more likely to get second-impact syndrome than their older counterparts. However, SIS is also a concern for adult athletes. Adolescent and young adult males who play American football or hockey, or who box or ski are the most common individuals with the condition. Most documented cases of SIS have occurred in males, but it is not known whether this is due to a special vulnerability or to a greater exposure of males to second impacts. In Canada, a law mandating concussion education for coaches, athletes, and medical practitioners was passed as a result of the death of Rowan Stringer, a female high school athlete who died after receiving three blows to the head in the course of one week in 2013. She showed only mild symptoms of headache following the first two impacts, but lost consciousness and never regained it following the third. Medical examiners found that SIS was the cause of her death.What is Rowan's Law and what does it mean for amateur sports? (2017, October 30). Retrieved from https://completeconcussions.com/2016/06/01/rowans-law/ Studies have found that people who have received one concussion are at a higher risk to receive a concussion in the future.


Pathophysiology

A concussion temporarily changes the brain's function. It is believed that the brain is left in a vulnerable state after a concussion and that a second blow is linked to SIS. The actual mechanism behind the catastrophic brain swelling is controversial. A second injury during this time is thought to unleash a series of metabolic events within the brain. Schwarz A (September 15, 2007)
Silence on concussions raises risks of injury
''New York Times'' Nytimes.com. Retrieved on 2008-01-01.
Changes indicative of SIS may begin occurring in the injured brain within 15 seconds of the second concussion.SIS: Second impact syndrome
brochure. El Dorado county public health and emergency medical services. Retrieved on 2007-12-30.
Pathophysiological changes in SIS can include a loss of
autoregulation Autoregulation is a process within many biological systems, resulting from an internal adaptive mechanism that works to adjust (or mitigate) that system's response to stimuli. While most systems of the body show some degree of autoregulation, i ...
of the brain's
blood vessel Blood vessels are the tubular structures of a circulatory system that transport blood throughout many Animal, animals’ bodies. Blood vessels transport blood cells, nutrients, and oxygen to most of the Tissue (biology), tissues of a Body (bi ...
s, which causes them to become congested. The vessels dilate, greatly increasing their diameter and leading to a large increase in
cerebral blood flow Cerebral circulation is the movement of blood through a network of cerebral arteries and veins supplying the brain. The rate of cerebral blood flow in an adult human is typically 750 milliliters per minute, or about 15% of cardiac output. ...
. Progressive cerebral edema may also occur. The increase of blood and brain volume within the skull causes a rapid and severe increase in
intracranial pressure Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adu ...
, which can in turn cause uncal and cerebellar brain herniation, a disastrous and potentially fatal condition in which the brain is squeezed past structures within the skull. Studies on animals have shown that the brain may be more vulnerable to a second concussive injury administered shortly after a first. In one such study, a mild impact administered within 24 hours of another one with minimal neurological impairment caused massive breakdown of the
blood brain barrier Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is compo ...
and subsequent brain swelling. Loss of this protective barrier could be responsible for the edema found in SIS. Animal studies have shown that the immature brain may be more vulnerable to brain trauma; these findings may provide clues as to why SIS primarily affects people under age 18.


Diagnosis

Magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...
and
computed tomography A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...
are the most useful imaging tools for detecting SIS. The congestion in the brain's blood vessels may be visible using
CT scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or ...
s. SIS is distinct from repetitive head injury syndrome, in which a person has a series of minor head injuries over time and experiences a slow decline in functions such as cognitive abilities. Unlike SIS, repetitive head injury syndrome may still occur even when symptoms from prior injuries have completely resolved. SIS is thought to be more severe than repetitive head injury syndrome in both the short- and long-term.


Prevention

Measures that prevent head injuries in general also prevent SIS. Thus athletes are advised to use protective gear such as helmets, though helmets do not entirely prevent the syndrome. Experts advise that athletes who have had one concussion and still complain of concussion-related symptoms be prohibited from returning to the game due to the possibility of developing SIS. Athletes are also discouraged from returning to play until after they have been evaluated and approved for resuming the sport by a healthcare provider skilled in evaluating concussion. Some athletes may deny concussion symptoms because they do not wish to be prevented from rejoining the game. An initial head injury may impair an athlete's judgment and ability to decide to refrain from participating in risky activity, so some healthcare providers encourage family members and other acquaintances to pressure an athlete not to return to play. Several different sets of return-to-play guidelines exist for athletes who have had minor head trauma. These exist in part to prevent the player from developing SIS. A variety of
concussion grading systems Concussion grading systems are sets of criteria used in sports medicine to determine the severity, or grade, of a concussion, the mildest form of traumatic brain injury. At least 16 such systems exist, and there is little agreement among prof ...
have been devised, in part to aid in this determination. Every return-to-play guideline recommends that an athlete not return to competition until all concussion symptoms are absent during both rest and exercise. The American Academy of Neurology recommends that young athletes be prohibited from returning to play for at least a week in most cases of concussion. The current return-to-play guidelines may not be strict enough to protect young athletes from SIS. On the other hand, they may be too strict for professional football players; evidence that the syndrome exists in this population is lacking.


Treatment

Treatment of the loss of autoregulation of the brain's blood vessels may be difficult or impossible. When SIS occurs,
surgery Surgery is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery s ...
does not help and there is little hope for recovery. Treatment requires immediate recognition and includes administration of
osmotic Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region o ...
agents and
hyperventilation Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blo ...
in order to lower intracranial pressure.


Prognosis

The mortality rate for SIS approaches 50%, and morbidity (
disability Disability is the experience of any condition that makes it more difficult for a person to do certain activities or have equitable access within a given society. Disabilities may be Cognitive disability, cognitive, Developmental disability, d ...
) is almost 100%. Since the condition is so rare, the connection between SIS and future disability has been difficult to establish and is therefore poorly understood. When SIS is not fatal, the effects are similar to those of severe traumatic brain injury can occur, including persistent
muscle spasm A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ, such as the bladder. A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a musc ...
s and tenseness, emotional instability,
hallucination A hallucination is a perception in the absence of an external stimulus that has the compelling sense of reality. They are distinguishable from several related phenomena, such as dreaming ( REM sleep), which does not involve wakefulness; pse ...
s,
post-traumatic epilepsy Post-traumatic epilepsy (PTE) is a form of acquired epilepsy that results from brain damage caused by physical trauma to the brain (traumatic brain injury, abbreviated TBI). A person with PTE experiences repeated post-traumatic seizures (PTS, se ...
, mental disability,
paralysis Paralysis (: paralyses; also known as plegia) is a loss of Motor skill, motor function in one or more Skeletal muscle, muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory d ...
,Tyler JH and Nelson ME (May 2000)
Second impact syndrome: Sports confront consequences of concussions
''USA Today'' (Society for the Advancement of Education). Retrieved through findarticles.com on 2007-12-16.
coma A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to Nociception, respond normally to Pain, painful stimuli, light, or sound, lacks a normal Circadian rhythm, sleep-wake cycle and does not initiate ...
, and
brain death Brain death is the permanent, irreversible, and complete loss of Electroencephalography, brain function, which may include cessation of involuntary activity (e.g., Control of ventilation#Control of respiratory rhythm, breathing) necessary to su ...
.


Epidemiology

Though the incidence of second-impact syndrome is unknown, the condition is rare; very few cases have been confirmed in medical literature. The controversy surrounding the existence of second impact syndrome may play a role in the known and recorded incidence. The United States seemingly has far more reported cases of second-impact syndrome than elsewhere. The patients affected most often include young adults and adolescents that are 16 to 19 years old. Adolescents who sustain a head injury that goes unrecognized could be placing themselves at a greater risk due to the effects of longer and more diffuse cerebral swelling that occurs in their body. The adolescent brain is 60 times more sensitive to components of the metabolic chain reaction that occurs after trauma, resulting in more diffuse cerebral swelling. After the initial concussion, the children and young adults are more likely to sustain a second impact within the first two weeks. In athletics, the susceptible population includes those that participate in contact sports such as American football, boxing and hockey. In the 13-year period from 1980 to 1993, 35
American football American football, referred to simply as football in the United States and Canada and also known as gridiron football, is a team sport played by two teams of eleven players on a rectangular American football field, field with goalposts at e ...
related cases of SIS were recorded; 17 of these were confirmed by
autopsy An autopsy (also referred to as post-mortem examination, obduction, necropsy, or autopsia cadaverum) is a surgical procedure that consists of a thorough examination of a corpse by dissection to determine the cause, mode, and manner of deat ...
or
surgery Surgery is a medical specialty that uses manual and instrumental techniques to diagnose or treat pathological conditions (e.g., trauma, disease, injury, malignancy), to alter bodily functions (e.g., malabsorption created by bariatric surgery s ...
and
magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...
to be due to SIS, and 18 cases were found to be probably SIS-related. Additionally, the initial trauma commonly goes unreported, adding to the confusion about how often the syndrome occurs. The prevalence of unreported trauma is common as a study showed that 25% of athletes thought that a concussion requires loss of consciousness. A study by Sullivan et al. found that 83% of male rugby athletes were aware of concussion signs and symptoms, but only 50% understood or were aware of the protocol to return to play after an injury. When coaches were surveyed, 45% of participants did not believe immediate removal from play is warranted after a concussion. Of this group surveyed, 62% identified proper post concussion management and this lack of proper post concussion management could lead to SIS. Both direct blows to the head and blows to the body can produce subdural hematomas, diffuse cerebral edema, subarachnoid hemorrhage, and ischemic stroke, all pathologies that can lead to death. By one estimate, the syndrome kills four to six people under the age of 18 per year.Bach G (2007),
Heads up
. ''SportingKid Magazine''. National Alliance for Youth Sports. Scientific Advisory Services, Ltd. Retrieved on 2007-12-30.
According to the
Centers for Disease Control The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency under the Department of Health and Human Services (HHS), and is headquartered in Atlanta, ...
, about 1.5 people die each year from a concussion in the US; in most of these cases, the person had received another concussion previously.Neurosurgery Today (November 2005)
Concussion
Neurosurgerytoday.org. Retrieved on 2008-01-02.
In the presence of second-impact syndrome, the mortality rate is at best 50% when diffuse cerebral swelling occurs. In part due to the poor documentation of the initial injury and continuing symptoms in recorded cases, some professionals think that the condition is over-diagnosed, and some doubt the validity of the diagnosis altogether. Due to the nature of the impact, the validity may be in question as subdural hematomas or other structural anomalies may directly affect the outcome.   Along with the short term effects that occur with second-impact syndrome, improper care for concussions can lead to longer term effects as well. These include early onset dementia or Alzheimer's, and early onset of Parkinson's disease. Increased loss of vision and risk of stroke can occur further on in their lives.


History

The condition was first described in 1973 by R.C. Schneider, and the term second-impact syndrome was coined in 1984. In 1984, R.L. Saunders described the death of a football player who had died after a second, unremarkable concussion and hypothesized that the second blow caused a catastrophic rise in ICP, possibly through loss of vasomotor tone, because the brain was in a vulnerable state. Between 1984 and 1991, only four cases were documented. Between 1992 and 1998, reports of the condition began to be made more frequently than they had before, a fact is thought to be due to wider recognition of the syndrome by clinicians. In 1991, J.P. Kelly and others reported another football death after repeated concussions and coined the term "vascular congestion syndrome". In 2005, Preston Plevretes, a football player for LaSalle University, had his life changed forever by second-impact syndrome. After undergoing a head-to-head hit at football practice, a university nurse practitioner diagnosed Plevretes with a concussion and two days later was told he was allowed to resume play. Three games after returning Plevretes sustained another concussion resulting in second-impact syndrome. He was rushed to the hospital where doctors cut the right side of his skull. Five years after the injury, he still struggles to do everyday activities. Because of Plevretes, the NCAA revised concussion guidelines. The NCAA strongly urges schools to have a concussion management plan. They also require that an athlete have clearance by a team doctor before being allowed to return. In 2006, Zachary Lystedt, a thirteen-year-old football player, had a concussion during one of his games. He shrugged off the hit and went back in the game a few plays later. At the end of the game, he collapsed on the field. Lystedt had second-impact syndrome. He was airlifted to a hospital where surgeons cut both sides of his skull so that the blood clot could be taken out. He was in the hospital for months and he still has trouble doing everyday things, such as walking. To prevent other families from going through what they went through, the Lystedt family made it their goal to make a law that athletes who are suspected of a concussion are not allowed to return to play unless he or she is cleared by a licensed physician. The law is now effective in over thirty states.ESPN (2012, February 1). Life Changed By Concussions
ideo file IDEO () is a design firm, design and consulting firm with offices in the U.S., England, and China. It was founded in Palo Alto, California, in 1991. The company's 500 staff uses a design thinking approach to design products, services, environmen ...
Retrieved from https://www.youtube.com/watch?v=wb6Bm5skuBA
By 2003, 21 cases of SIS had been reported in medical literature.


Controversy

The existence of SIS is in question and is somewhat controversial. The sudden collapse seen in patients may be due to a type of cerebral
edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...
that can follow an initial impact in children and teenagers, rather than to SIS. This type of edema, referred to as '' diffuse cerebral swelling'', may be the real reason for the collapse which young people sometimes experience and which is commonly thought to be due to SIS. Those who doubt the validity of the diagnosis cite the finding that diffuse cerebral swelling is more common in children and adolescents as an explanation for the greater frequency of SIS diagnoses in young people. One group found that of 17 previously identified cases of SIS, only 5 met their diagnostic criteria for the syndrome, with some cases not clearly involving a second impact. They found that diagnoses of SIS were frequently based on bystander accounts of previous injuries, which they showed to be unreliable. Teammates of players who are thought to have SIS may over-report the initial concussion, giving the appearance of a greater number of second impacts than actually exist. Thus critics argue that the small number of reported cases leaves the question of whether SIS really causes the brain to swell catastrophically unanswered. Whether a second impact is really involved in the diffuse cerebral swelling that occurs on rare occasions after a mild
traumatic brain injury A traumatic brain injury (TBI), also known as an intracranial injury, is an injury to the brain caused by an external force. TBI can be classified based on severity ranging from mild traumatic brain injury (mTBI/concussion) to severe traumati ...
is controversial, but some experts agree that such catastrophic brain swelling does occur after a very small number of mild brain injuries and that young age is associated with increased risk. It is also agreed that some people may be particularly vulnerable to catastrophic brain swelling as the result of multiple head injuries.


See also

*
Brain damage Brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating trauma-induced damage. A common ...
*
Dementia pugilistica Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease linked to repeated trauma to the head. The encephalopathy symptoms can include behavioral problems, mood problems, and problems with thinking. The disease often gets worse ...
(punch-drunk syndrome) *
Post-concussion syndrome Post-concussion syndrome (PCS), also known as persisting symptoms after concussion, is a set of symptoms that may continue for weeks, months, or years after a concussion. PCS is medically classified as a mild traumatic brain injury (TBI). About ...


References

{{Neurotrauma Neurotrauma Syndromes Sports injuries