Concussion

A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include loss of consciousness; memory loss; headaches; difficulty with thinking, concentration, or balance; nausea; blurred vision; dizziness; sleep disturbances, and mood changes. Any of these symptoms may begin immediately, or appear days after the injury. Concussion should be suspected if a person indirectly or directly hits their head and experiences any of the symptoms of concussion. Symptoms of a concussion may be delayed by 1–2 days after the accident. It is not unusual for symptoms to last 2 weeks in adults and 4 weeks in children. Fewer than 10% of sports-related concussions among children are associated with loss of consciousness.

Common causes include motor vehicle collisions, falls, sports injuries, and bicycle accidents. Risk factors include physical violence, drinking alcohol and a prior history of concussion. The mechanism of injury involves either a direct blow to the head or forces elsewhere on the body that are transmitted to the head. This is believed to result in neuron dysfunction, as there are increased glucose requirements, but not enough blood supply. A thorough evaluation by a qualified medical provider working in their scope of practice (such as a physician or nurse practitioner) is required to rule out life-threatening head injuries, injuries to the cervical spine, and neurological conditions and to use information obtained from the medical evaluation to diagnose a concussion. Glasgow coma scale score 13 to 15, loss of consciousness for less than 30 minutes, and memory loss for less than 24 hours may be used to rule out moderate or severe traumatic brain injuries. Diagnostic imaging such as a CT scan or an MRI may be required to rule out severe head injuries. Routine imaging is not required to diagnose concussion.

Prevention of concussions includes the use of a helmet when bicycling or motorbiking. Treatment includes physical and mental rest for 1–2 days, with a gradual step-wise return to activities, school, and work. Prolonged periods of rest may slow recovery and result in greater depression and anxiety. Paracetamol (acetaminophen) or NSAIDs may be recommended to help with a headache. Prescribed aerobic exercise may improve recovery. Physiotherapy may be useful for persisting balance problems, headache, or whiplash; cognitive behavioral therapy may be useful for mood changes. Evidence to support the use of hyperbaric oxygen therapy and chiropractic therapy is lacking.

Worldwide, concussions are estimated to affect more than 3.5 per 1,000 people a year. Concussions are classified as mild traumatic brain injuries and are the most common type of TBIs. Males and young adults are most commonly affected. Outcomes are generally good. Another concussion before the symptoms of a prior concussion have resolved is associated with worse outcomes. Repeated concussions may also increase the risk in later life of chronic traumatic encephalopathy, Parkinson's disease and depression.

## Signs and symptoms

Concussion symptoms vary between people and include physical, cognitive, and emotional symptoms. Symptoms may appear immediately or be delayed by 1–2 days. Delayed onset of symptoms may still be serious and require a medical assessment. Up to one-third of people with concussion experience longer or persisting concussion symptoms, also known as post concussion syndrome or persisting symptoms after concussion, which is defined as concussion symptoms lasting for 4 weeks or longer in children and adolescents, and symptoms lasting for more than 14 days in an adult. The severity of the initial symptoms is the strongest predictor of recovery time in adults.

### Physical

Headaches are the most common mTBI symptom. Others include dizziness, vomiting, nausea, lack of motor coordination, difficulty balancing, or other problems with movement or sensation. Visual symptoms include light sensitivity, seeing bright lights, blurred vision, and double vision. Tinnitus, or a ringing in the ears, is also commonly reported. In one in about seventy concussions, concussive convulsions occur, but seizures that take place during or immediately after a concussion are not "post-traumatic seizures", and, unlike post-traumatic seizures, are not predictive of post-traumatic epilepsy, which requires some form of structural brain damage, not just a momentary disruption in normal brain functioning. Concussive convulsions are thought to result from temporary loss or inhibition of motor function and are not associated either with epilepsy or with more serious structural damage. They are not associated with any particular sequelae and have the same high rate of favorable outcomes as concussions without convulsions.

### Cognitive and emotional

Cognitive symptoms include confusion, disorientation, and difficulty focusing attention. Loss of consciousness may occur, but is not necessarily correlated with the severity of the concussion if it is brief. Post-traumatic amnesia, in which events following the injury cannot be recalled, is a hallmark of concussions. Confusion may be present immediately or may develop over several minutes. A person may repeat the same questions, be slow to respond to questions or directions, have a vacant stare, or have slurred or incoherent speech. Other concussion symptoms include changes in sleeping patterns and difficulty with reasoning, concentrating, and performing everyday activities.

A concussion can result in changes in mood including crankiness, loss of interest in favorite activities or items, tearfulness, and displays of emotion that are inappropriate to the situation. Common symptoms in concussed children include restlessness, lethargy, and irritability.

## Mechanism

### Forces

The brain is surrounded by cerebrospinal fluid, which protects it from light trauma. More severe impacts, or the forces associated with rapid acceleration, may not be absorbed by this cushion. Concussions, and other head-related injuries, occur when external forces acting on the head are transferred to the brain. Such forces can occur when the head is struck by an object or surface (a 'direct impact'), or when the torso rapidly changes position (i.e. from a body check) and force is transmitted to the head (an 'indirect impact').

Forces may cause linear, rotational, or angular movement of the brain or a combination of them. In rotational movement, the head turns around its center of gravity, and in angular movement, it turns on an axis, not through its center of gravity. The amount of rotational force is thought to be the major component in concussion and its severity. As of 2007, studies with athletes have shown that the amount of force and the location of the impact are not necessarily correlated with the severity of the concussion or its symptoms, and have called into question the threshold for concussion previously thought to exist at around 70–75 g.

The parts of the brain most affected by rotational forces are the midbrain and diencephalon. 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 often seen in concussion. Other areas of the brain that may be affected include the upper part of the brain stem, the fornix, the corpus callosum, the temporal lobe, and the frontal lobe. Angular accelerations of 4600, 5900, or 7900 rad/s2 are estimated to have 25, 50, or 80% risk of mTBI respectively.

### Pathophysiology

In both animals and humans, mTBI can alter the brain's physiology for hours to years, setting into motion a variety of pathological events. As one example, in animal models, after an initial increase in glucose metabolism, there is a subsequent reduced metabolic state which may persist for up to four weeks after injury. Though these events are thought to interfere with neuronal and brain function, the metabolic processes that follow concussion are reversible in a large majority of affected brain cells; however, a few cells may die after the injury.

Included in the cascade of events unleashed in the brain by concussion is impaired neurotransmission, loss of regulation of ions, deregulation of energy use and cellular metabolism, and a reduction in cerebral blood flow. Excitatory neurotransmitters, chemicals such as glutamate that serve to stimulate nerve cells, are released in excessive amounts. The resulting cellular excitation causes neurons to fire excessively. This creates an imbalance of ions such as potassium and calcium across the cell membranes of neurons (a process like excitotoxicity).

At the same time, cerebral blood flow is relatively reduced for unknown reasons, though the reduction in blood flow is not as severe as it is in ischemia. Thus cells get less glucose than they normally do, which causes an "energy crisis".

Concurrently with these processes, the activity of mitochondria may be reduced, which causes cells to rely on anaerobic metabolism to produce energy, increasing levels of the byproduct lactate.

For a period of minutes to days after a concussion, the brain is especially vulnerable to changes in intracranial pressure, blood flow, and anoxia. According to studies performed on animals (which are not always applicable to humans), large numbers of neurons can die during this period in response to slight, normally innocuous changes in blood flow.

Concussion involves diffuse (as opposed to focal) brain injury, meaning that the dysfunction occurs over a widespread area of the brain rather than in a particular spot. It is thought to be a milder type of diffuse axonal injury, because axons may be injured to a minor extent due to stretching. Animal studies in which rodents were concussed have revealed lifelong neuropathological consequences such as ongoing axonal degeneration and neuroinflammation in subcortical white matter tracts. Axonal damage has been found in the brains of concussion patients who died from other causes, but inadequate blood flow to the brain due to other injuries may have contributed. Findings from a study of the brains of deceased NFL athletes who received concussions suggest that lasting damage is done by such injuries. This damage, the severity of which increases with the cumulative number of concussions sustained, can lead to a variety of other health issues.

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 findings would apply 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."

Using animal studies, the pathology of a concussion seems to start with mechanical shearing and stretching forces disrupting the cell membrane of nerve cells through "mechanoporation". This results in potassium outflow from within the cell into the extracellular space with the subsequent release of excitatory neurotransmitters including glutamate which leads to enhanced potassium extrusion, in turn resulting in sustained depolarization, impaired nerve activity and potential nerve damage. Human studies have failed to identify changes in glutamate concentration immediately post-mTBI, though disruptions have been seen 3 days to 2 weeks post-injury. In an effort to restore ion balance, the sodium-potassium ion pumps increase activity, which results in excessive ATP (adenosine triphosphate) consumption and glucose utilization, quickly depleting glucose stores within the cells. Simultaneously, inefficient oxidative metabolism leads to anaerobic metabolism of glucose and increased lactate accumulation. There is a resultant local acidosis in the brain and increased cell membrane permeability, leading to local swelling. After this increase in glucose metabolism, there is a subsequent lower metabolic state which may persist for up to 4 weeks after injury. A completely separate pathway involves a large amount of calcium accumulating in cells, which may impair oxidative metabolism and begin further biochemical pathways that result in cell death. Again, both of these main pathways have been established from animal studies and the extent to which they apply to humans is still somewhat unclear.

## Diagnosis

Head trauma recipients are initially assessed to exclude a more severe emergency such as an intracranial hemorrhage or other serious head or neck injuries. This includes the "ABCs" (airway, breathing, circulation) and stabilization of the cervical spine which is assumed to be injured in any athlete who is found to be unconscious after head or neck injury. Indications that screening for more serious injury is needed include 'red flag symptoms' or 'concussion danger signs': worsening headaches, persisting vomiting, increasing disorientation or a deteriorating level of consciousness, seizures, and unequal pupil size. Those with such symptoms, or those who are at higher risk of a more serious brain injury, require an emergency medical assessment. Brain imaging such as a CT scan or MRI may be suggested, but should be avoided unless there are progressive neurological symptoms, focal neurological findings, or concern of skull fracture on exam.

Diagnosis of concussion requires an assessment performed by a physician or nurse practitioner to rule out severe injuries to the brain and cervical spine, mental health conditions, or other medical conditions. Diagnosis is based on physical and neurological examination findings, duration of unconsciousness (usually less than 30 minutes) and post-traumatic amnesia (usually less than 24 hours), and the Glasgow Coma Scale (people with mTBI have scores of 13 to 15). A CT scan or MRI is not required to diagnose concussion. Neuropsychological tests such as the SCAT5/child SCAT5 may be suggested measure cognitive function. Such tests may be administered hours, days, or weeks after the injury, or at different times to demonstrate any trend. Some athletes are also being tested pre-season (pre-season baseline testing) to provide a baseline for comparison in the event of an injury, though this may not reduce risk or affect return to play and baseline testing is not required or suggested for most children and adults.

If the Glasgow coma scale is less than 15 at two hours or less than 14 at any time, a CT is recommended. In addition, a CT scan is more likely to be performed if observation after discharge is not assured or intoxication is present, there is suspected increased risk for bleeding, age greater than 60, or less than 16. Most concussions, without complication, cannot be detected with MRI or CT scans. However, changes have been reported on MRI and SPECT imaging in those with concussion and normal CT scans, and post-concussion syndrome may be associated with abnormalities visible on SPECT and PET scans. Mild head injury may or may not produce abnormal EEG readings. A blood test known as the Brain Trauma Indicator was approved in the United States in 2018 and may be able to rule out the risk of intracranial bleeding and thus the need for a CT scan for adults.

Concussion may be under-diagnosed because of the lack of the highly noticeable signs and symptoms while athletes may minimize their injuries to remain in the competition. Direct impact to the head is not required for a concussion diagnosis, as other bodily impacts with a subsequent force transmission to the head are also causes. A retrospective survey in 2005 suggested that more than 88% of concussions are unrecognized. Particularly, many younger athletes struggle with identifying their concussions, which often result in the non-disclosure of concussions and consequently under-representing the incidence of concussions in the context of sport.

Diagnosis can be complex because concussion shares symptoms with other conditions. For example, post-concussion symptoms such as cognitive problems may be misattributed to brain injury when, in fact, due to post-traumatic stress disorder (PTSD).

There are no fluid biomarkers (i.e., blood or urine tests) that are validated for diagnosing concussion in children or adolescents.

### Classification

No single definition of concussion, minor head injury, or mild traumatic brain injury is universally accepted. In 2001, the expert Concussion in Sport Group of the first International Symposium on Concussion in Sport defined concussion as "a complex pathophysiological process affecting the brain, induced by traumatic biomechanical forces." It was agreed that concussion typically involves temporary impairment of neurological function that heals by itself within time, and that neuroimaging normally shows no gross structural changes to the brain as the result of the condition.

However, although no structural brain damage occurs according to the classic definition, some researchers have included injuries in which structural damage has occurred, and the National Institute for Health and Clinical Excellence definition includes physiological or physical disruption in the brain's synapses. Also, by definition, concussion has historically involved a loss of consciousness. However, the definition has evolved over time to include a change in consciousness, such as amnesia, although controversy continues about whether the definition should include only those injuries in which loss of consciousness occurs. This debate resurfaces in some of the best-known concussion grading scales, in which those episodes involving loss of consciousness are graded as being more severe than those without.

Definitions of mild traumatic brain injury (mTBI) were inconsistent until the World Health Organization's International Statistical Classification of Diseases and Related Health Problems (ICD-10) provided a consistent, authoritative definition across specialties in 1992. Since then, various organizations such as the American Congress of Rehabilitation Medicine and the American Psychiatric Association in its Diagnostic and Statistical Manual of Mental Disorders have defined mTBI using some combination of loss of consciousness, post-traumatic amnesia, and the Glasgow Coma Scale.

Concussion falls under the classification of mild TBI, but 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 other injuries such as intracranial hemorrhages (e.g. intra-axial hematoma, epidural hematoma, and subdural hematoma) are not necessarily precluded in mTBI or mild head injury, as they are in concussion. mTBI associated with abnormal neuroimaging may be considered "complicated mTBI". "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. Descriptions of the condition, including the severity and the area of the brain affected, are now used more often than "concussion" in clinical neurology.

## Prevention

Prevention of mTBI involves general measures such as wearing seat belts, using airbags in cars, and protective equipment such as helmets for high-risk sports. 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 helmets and other headgear and policy changes such as the banning of body checking in youth hockey leagues have been found to reduce the number and severity of concussions in athletes. Secondary prevention such as a Return to Play Protocol for an athlete may reduce the risk of repeat concussions. 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.

Educational interventions, such as handouts, videos, workshops, and lectures, can improve concussion knowledge of diverse groups, particularly youth athletes and coaches. Strong concussion knowledge may be associated with greater recognition of concussion symptoms, higher rates of concussion reporting behaviors, and reduced body checking-related penalties and injuries, thereby lowering risk of mTBI.

Due to the incidence of concussion in sport, younger athletes often do not disclose concussions and their symptoms. Common reasons for non-disclosure include a lack of awareness of the concussion, the belief that the concussion was not serious enough, and not wanting to leave the game or team due to their injury. Self-reported concussion rates among U-20 and elite rugby union players in Ireland are 45–48%, indicating that many concussions 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.

## Treatment

Adults and children with a suspected concussion require a medical assessment with a doctor or nurse practitioner to confirm the diagnosis of concussion and rule out more serious head injuries. After life-threatening head injuries, injuries to the cervical spine, and neurological conditions are ruled out, exclusion of neck or head 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 needed. Observation to monitor for worsening condition is an important part of treatment. People may be released after assessment from their primary care medical clinic, 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 ("red flag symptoms") such as change in consciousness, convulsions, severe headache, extremity weakness, vomiting, new bleeding or deafness in either or both ears. Education about symptoms, their management, and their normal time course, may lead to an improved outcome.

### Rest and return to physical and cognitive activity

Physical and cognitive rest is recommended for the first 24–48 hours following a concussion after which injured persons should gradually start gentle low-risk physical and cognitive activities that do not make current symptoms worse or bring on new symptoms. Any activity for which there is a risk of contact, falling, or bumping the head should be avoided until the person has clearance from a doctor or nurse practitioner. Low-risk activities can be started even while a person has symptoms, as long as the activity does not worsen existing symptoms or bring on new concussion symptoms. Resting completely for longer than 24–48 hours follow concussion has been shown to be associated with longer recovery.

### Return-to-school

The resumption of low-risk school activities should begin as soon as the student feels ready and has completed an initial period of cognitive rest of no more than 24–48 hours following the acute injury. Long absences from school are not suggested, however, the return to school should be gradual and step-wise. Prolonged complete mental or physical rest (beyond 24–48 hours after the accident that lead to the concussion) may worsen outcomes, however, rushing back to full school work load before the person is ready, has also been associated with longer-lasting symptoms and an extended recovery time. Students with a suspected concussion are required to see a doctor for an initial medical assessment and for suggestions on recovery, however, medical clearance is not required for a student to return to school. Since students may appear 'normal', continuing education of relevant school personnel may be needed to ensure appropriate accommodations are made such as part-days and extended deadlines. Accommodations should be based on the monitoring of symptoms that are present during the return-to-school transition including headaches, dizziness, vision problems, memory loss, difficulty concentrating, and abnormal behavior. Students must have completely resumed their school activities (without requiring concussion-related academic supports) before returning to full-contact or competitive sports.

### Return-to-sport

For persons participating in athletics, it is suggested that participants progress through a series of graded steps. These steps include:

- Stage 1 (Immediately after injury): 24–48 hours (maximum) of relative physical and cognitive rest. This can include gentle daily activities such as walking in the house, gentle housework, and light school work that do not make symptoms worse. No sports activities.
- Stage 2: Light aerobic activity such as walking or stationary cycling
- Stage 3: Sport-specific activities such as running drills and skating drills
- Stage 4: Non-contact training drills (exercise, coordination, and cognitive load)
- Stage 5: Full-contact practice (requires medical clearance)
- Stage 6: Return to full-contact sport or high-risk activities (requires medical clearance)

At each step, the person should not have worsening or new symptoms for at least 24 hours before progressing to the next. If symptoms worsen or new symptoms begin, athletes should drop back to the previous level for at least another 24 hours.

Intercollegiate or professional athletes, 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.

### Medications

Medications may be prescribed to treat headaches, sleep problems and depression. Analgesics such as ibuprofen can be taken for headaches, 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.

### Return to work

Determining the ideal time for a person to return to work will depend on personal factors and job-related factors including the intensity of the job and the risk of falling or hitting one's head at work during recovery. After the required initial recovery period of complete rest (24–48 hours after the concussion began), gradually and safely returning to the workplace with accommodations and support in place, should be prioritized over staying home and resting for long periods of time, to promote physical recovery and reduce the risk of people becoming socially isolated. The person should work with their employer to design a step-wise "return-to-work" plan. For those with a high-risk job, medical clearance may be required before resuming an activity that could lead to another head injury. Students should have completed the full return-to-school progression with no academic accommodations related to the concussion required before starting to return to part-time work.

## Prognosis

The majority of children and adults fully recover from a concussion, however some may experience a prolonged recovery. There is no single physical test, blood test (or fluid biomarkers), or imaging test that can be used to determine when a person has fully recovered from concussion.

A person's 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. 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. Other strong factors include participation in a contact sport and body mass size.

### Pediatric concussion

Most children recover completely from concussion in less than four weeks, however 15–30% of youth may experience symptoms that last longer than a month.

### People aged 65+ with concussion

Mild traumatic brain injury recovery time in people over age 65 may have increased complications due to elevated health concerns, or comorbidities. This often results in longer hospitalization duration, poorer cognitive outcomes, and higher mortality rates.

### Repeat concussion

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. 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.

### Post-concussion syndrome

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. Rest, a previously recommended recovery technique, has limited effectiveness. A recommended treatment in both children and adults with symptoms beyond 4 weeks involves an active rehabilitation program with reintroduction of non-contact aerobic activity. Progressive physical exercise has been shown to reduce long-term post-concussive symptoms. Symptoms usually go away on their own within months but may last for years. 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

As of 1999, cumulative effects of concussions were poorly understood, especially the effects on 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. As of 2006, studies 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 chronic traumatic encephalopathy, 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. An experience of three or more concussions is 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 disabilities 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

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.

## Epidemiology

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 under reporting 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 under reporting. At least 25% of people with mTBI 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.

### Age

Young children have the highest concussion rate among all age groups. However, most people with a 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 develop mTBI at about twice the rate of their female counterparts. However, female athletes may be at a higher risk of sustaining a concussion than their male counterparts.

### Sports

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 American football, the rugby codes, MMA 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 US, Australia, and Canada.

### Workplace

Concussions may also be common and occur in the workplace. According to the US Bureau of Labour Statistics, the most common causes of mTBI-related hospitalizations and deaths from the workplace are falls, force of heavy objects, and vehicular collisions. As a consequence, jobs in the construction, transportation, and natural resource industries (e.g. agriculture, fishing, mining) have more elevated mTBI incidence rates ranging from 10 to 20 cases per 100,000 workers. In particular, as vehicular collisions are the leading cause of workplace mTBI-related injuries, workers from the transportation sector often carry the most risk. Despite these findings, there still remain important gaps in data compilation on workplace-related mTBIs, which has raised questions about increased concussion surveillance and preventive measures in private industry.

## History

The Hippocratic Corpus, a 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. In the 10th century, the Persian physician Muhammad ibn Zakarīya Rāzi was the first to write about concussion as distinct from other types of head injury. 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, a 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

### Costs

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 is 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.

### Terminology

The terms mild brain injury, mild traumatic brain injury (mTBI), mild head injury (MHI), and concussion may be used interchangeably; although the term "concussion" is still used in sports literature as interchangeable with "MHI" or "mTBI", the general clinical medical literature uses "mTBI" instead, since a 2003 CDC report outlined it as an important strategy. In this article, "concussion" and "mTBI" are used interchangeably.

The term "concussion" is from Latin concutere, "to shake violently" or concussus, "action of striking together".

## Research

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.

### Grading systems

National and international clinical practice guidelines do not recommend a concussion grading system for use by medical professionals.

#### Historical information on grading systems

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:

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.

## See also

- Concussions in American football
- Concussions in rugby union
- Head injury criterion
- Helmet removal (sports)

Type of traumatic brain injury


Cold Feet (series 1)

The first series of the British comedy-drama television series Cold Feet was first broadcast on the ITV network from 15 November to 20 December 1998. The six episodes were written by series creator Mike Bullen, produced by Christine Langan, and directed by Declan Lowney, Mark Mylod and Nigel Cole. It follows the award-winning pilot episode, broadcast in 1997. The storylines focus on three couples: Adam Williams and Rachel Bradley, Pete and Jenny Gifford, and David and Karen Marsden. They are played by James Nesbitt, Helen Baxendale, John Thomson, Fay Ripley, Robert Bathurst and Hermione Norris respectively.

The storylines follow the three couples as they try to stay faithful to each other. They are held back by issues such as impotence, infidelity, and unplanned pregnancy. Their lives are further complicated by their jobs, money troubles, and moving in together. Bullen embellished the scripts with events from his own personal life. The directors and producers made additional contributions, with the intent to keep the fiction in the programme as true to life as possible. The series was filmed in Greater Manchester in the first half of 1998, using Granada Television's studios, and exterior locations.

Critical reaction to the first episodes was negative, with many reviewers not liking the characters and finding the comedy drama format unusual. As the series progressed, critics' opinions became more positive; the production values rated highly and the fantasy scenes, which became a hallmark of Cold Feet, were well received. An average of eight million viewers watched the series each week. The following year it won awards from the Royal Television Society, the Broadcasting Press Guild and the British Comedy Awards. It was also nominated for the Rose d'Or and a Banff Rockie Award. All six episodes have been released on VHS, DVD and internet media formats.

## Episodes

## Production

Cold Feets pilot episode was intended by Andy Harries, the executive producer and Granada Television's controller of comedy, to lead to a series commission from the ITV network. Poor ratings on its night of broadcast in March 1997 stalled a commission; Harries told writer and creator Mike Bullen and producer Christine Langan to "forget it". ITV's limited portfolio of comedy meant that although it was a ratings failure, the pilot was selected by default to represent the network at the Montreux Television Festival that year. The pilot won the Silver Rose for Humour and the Rose d'Or. ITV still did not commission a series, and in the meantime Granada received offers from the BBC and Channel 4 for a six-part series. In August 1997, David Liddiment, who had chaired the panel of judges at Montreux, became ITV's director of programming and pledged to rebrand the network's comedy output. This included six new episodes of Cold Feet, which were announced that August. Production began in January 1998. Each episode was budgeted at £500,000, a small amount for a 50-minute drama.

### Cast

All six main cast members from the pilot returned for the series; James Nesbitt and Helen Baxendale play Adam Williams and Rachel Bradley, a couple in a fledgling relationship; John Thomson and Fay Ripley play Pete and Jenny Gifford, a married couple whose first child is born in the first episode; Robert Bathurst and Hermione Norris play David and Karen Marsden, an upper-middle-class couple who are considering having a second child. Each had mixed feelings about whether there would be a series commission after the poor reception of the pilot; Ripley did not stop thinking about it, in contrast to Bathurst, who viewed it as just another failed pilot he had done.

Following the resolution of Karen and David's storyline in the pilot, in which David concedes that the couple need to hire a nanny, Jacey Salles was cast as Ramona Ramirez. Salles was a bit-part actress in BBC sitcoms and had previously appeared in the 1998 Granada film The Misadventures of Margaret, which was co-produced by Harries. In her Cold Feet audition she was required to have a loud argument with her boyfriend over the telephone. She embellished this with "a bit of comic bastardisation of the English language" and won the part. Initially contracted for only two episodes, Salles assumed the Marsdens would employ a new nanny every few episodes, though she made two more appearances in the first series and eventually appeared in every series. Lennie James made two guest appearances as Kris Bumstead, though his second appearance in Episode 6 was mostly in the form of flashbacks. James was keen to find out the resolution to the "who's the father?" cliffhanger, reportedly repeatedly asking the producers whether the baby was Kris's. Other actors to make appearances were Denis Lawson as Alexander Welch and Sam Kelly as Algernon Gifford. John Thomson was pleased to work with Kelly, as he was a big fan of Allo 'Allo!, a sitcom in which Kelly appeared.

### Writing

Storylines for a potential series had been drafted by writer Mike Bullen during production of the pilot. When production on the series began, producer Christine Langan worked with him to create detailed plots for all six episodes, also acting as a script editor to redraft Bullen's work. Many of the plots were drawn from his own life; Pete and Jenny bringing up their new baby paralleled Bullen and his wife, whose first child was born in late 1997. The scenes where Pete and Jenny attend the antenatal classes were written from Bullen's memory, when he and his wife were "given callipers, forceps and a suction cup to play with". The conclusion of the fourth episode, in which Pete's father dies on the way to his grandson's christening, was suggested by Harries, whose own experience of the death of his father taught him that people rarely have the opportunity to say goodbye to loved ones in real life. Not all storylines were based on real life: For Karen and David's marriage guidance scenes in Episode 5, Bullen consulted the relationship support charity Relate. Actors and directors also had input into the scripts; Bullen's original script for the marriage therapy scenes ended with David shouting and apparently using a fire extinguisher as an offensive weapon. Bathurst was not convinced that was something that his character would do, as David is "too much of a coward to do anything overtly" and would not leave himself so "exposed":

> "As David grapples with the fire extinguisher to remove the hose from the barrel, we hear running footsteps approaching. The door is suddenly flung open and two male colleagues of the counsellor's burst open into the room. In a second they take a look at the scene, and we see what they see—the counsellor looking lost, Karen looking shocked, and most significantly, David standing over the counsellor, brandishing a fire extinguisher in an apparently threatening manner. Presuming their colleague to be in danger, the two men hurl themselves at David, knocking him to the ground. He squeals as he goes down, and complains loudly as he's pinned to the floor."
> —Episode 5's marriage guidance scene as originally scripted. Robert Bathurst believed that the scene left his cowardly character "exposed", so Mike Bullen rewrote it.

When storylining the six episodes, Bullen and Langan planned to split up Adam and Rachel at the series' climax, as "If [they] had just left them all living happily in their homes in Didsbury, there would be a less compelling reason to revisit them [in the second series]". Harries opposed the idea, believing that the audience would want a happy ending for the characters. However, he allowed the writer and producer to proceed with their idea. Langan and Episode 6 director Nigel Cole wanted Adam to leave after finding out about Rachel's pregnancy. She would have followed him and proven her love to him by singing to him over the PA system of the train—similar to the pilot's conclusion. Bullen thought that this idea was "atrocious", so spent the Easter weekend drafting an end to the series. The genesis of Rachel becoming pregnant, possibly by Kris, came during the filming of the second episode. Langan suggested to Bullen that they return to Rachel's marriage later in the series, using an adage she had learned from working on a soap opera that if the "seeds" of a storyline are sown early on it can pay off later. The Brief Encounter homage was conceived close to filming. Bullen had not seen the film so had to rent it on video before writing the scene.

### Filming

The directors had twelve days to film two episodes each, equating to approximately five minutes of screen-time per day. Langan asked Father Ted director Declan Lowney to helm the first two episodes after his successful direction of the pilot. Lowney declined in order to shoot a film in Ireland with Terence Stamp; production on it was scheduled to begin in October 1997 and would have overrun into Cold Feet's production calendar. Funding for Lowney's film fell through and he took the two episodes of Cold Feet after Langan offered them to him a second time. The other two directors were Mark Mylod and Nigel Cole.

Sets were constructed at Granada's Blue Shed studios in Salford for interior filming, which ran over 14 weeks from March to May. Exterior filming and location shooting was done in and around the city from February. The climax to the first episode—where Rachel drives her Mini across a golf course to pick up Pete—was filmed at Withington Golf Club in West Didsbury. A long lens was used to film the Mini approaching Thomson and Bathurst, making it appear closer to them than it was and avoiding having to drive it on the green. Filming on Episode 1 came close to overrunning, so Lowney filmed most of Jenny's birth scene in one uninterrupted take, encouraging the actors to ad-lib. Ripley wore a prosthetic abdomen to simulate the appearance of pregnancy throughout the episode and had a pubic wig applied for the birth scene. The uncredited baby who played Baby Adam in that scene was a two-week-old child who had been born two weeks premature, giving it the appearance of a new-born baby. The conclusion of the first episode was originally scripted to feature Pete and Adam playing crazy golf indoors. Lowney did not like the scene, so made thirty minutes available at the very end of production and directed Nesbitt and Thomson to just "talk". The scene was used by Bullen and Langan as the basis for an attraction between Adam and Jenny, implied in the sixth episode and developed in the second series.

The scenes of Adam and Rachel having sex in a shop window in the third episode, inspired by one of Bullen's ex-girlfriends, was filmed in an empty shop unit near Piccadilly station. The unit was dressed to look like a charity shop, with various items and the bed added. Mylod and the stunt co-ordinator storyboarded the sequence where the car comes through the shop window before setting it up on location. Nesbitt and Baxendale were switched with stunt doubles and the car was propelled up a ramp through the window. Explosive charges were placed on the glass to achieve a shatter effect. As only one take could be done, Mylod trailed five cameras on the window. Filming ran from 8 p.m. to 6 a.m. the following day. The location was near several clubs and many passers-by inquired what was being filmed. To avoid giving away the plot they were told that Baxendale was filming a bed advertisement, capitalising on her exposure from appearing in Friends.

Another stunt scene was filmed for Episode 6; the charity ball scene was filmed over two days at a Masonic Lodge and concluded with a fight between Jenny and Natalie (played by Lorelei King). The shots of Jenny spraying Natalie with a fire extinguisher were limited to two takes because it took so long to re-apply King's make up. The table that Ripley and King's stunt doubles fall through had its legs weakened, and the glasses on the table were replaced with sugar glass. The Brief Encounter fantasy was filmed at a steam railway near Rochdale. Nigel Cole used the scene as an opportunity to make his mark as a television director. Most of the scene was filmed by Cole and the main crew. Establishing shots were filmed by Langan and the second unit, due to time constraints. The lighting and focus of the fantasy station was intended to be a direct contrast to the harsh modernity of Piccadilly, which appeared in the "real life" scenes.

## Reception

### Broadcast and ratings

ITV trailed Cold Feet between 3 and 12 November. The trailer featured clips from the pilot episode, including the scene where Adam sings with a rose clenched between his buttocks. Six people complained to the Independent Television Commission (ITC), the commercial television regulator, about the scene being inappropriate. Their complaints were not upheld; the ITC ruled that the trailer did not breach the programming code, as "the humour of the piece was apparent from the outset". A 96 Sheet billboard advertising campaign also preceded broadcast, featuring the strapline "A comedy about life & all that". The broadcast was sponsored by Cockburn's Port.

The series was broadcast on ITV from 15 November to 20 December 1998. Harries wanted the series to air in the 9 p.m. timeslot but ITV Network Centre wanted it on at 10 p.m. (the same time the pilot had been scheduled), because the 9 p.m. timeslot was traditionally what was referred to as "the ironing slot"—programmes that can be watched without viewers having to concentrate. David Liddiment compromised with Harries and scheduled Cold Feet for a 9.30 p.m. start. The BBC responded by scheduling Andrew Davies' adaptation of Vanity Fair at the same time. The first five episodes aired from 9.30 p.m. but Episode 6 began at 10 p.m. The main target audience was the "upmarket" ABC1's.

Episode 1 averaged 7.47 million viewers over its hour, peaking at 9.2 million with a low point of 6.9 million. The episode ranked as the thirty-fourth most-watched programme of the week and the sixth most-watched drama (excluding soap-operas). The second episode dropped seven places and 1.9% on the previous week with 7.33 million viewers. It recovered to 7.46 million the following week but still managed only fortieth place in the Top 70 most-watched programmes. The fourth week held steady at 7.44 million viewers and fortieth position again. It had its best figures with Episode 5, which was seen by 7.91 million, making thirty-second in the Top 70. The final episode of the series suffered from its schedule change, dropping to fifty-ninth and 6.77 million viewers. Over the six weeks, Cold Feet averaged a 34% audience share, which was six points below ITV's Sunday peak time average.

### Critical reaction

The series was welcomed as "the British Thirtysomething" and there was additional publicity generated off the back of Helen Baxendale's appearances in Friends. The first two episodes did not impress critics; The Independent's Nicholas Barber called Episode 1 "the most depressing programme [he'd] ever seen". Commenting on the ending, he observed that "in comedyland, the police's main duty is to taxi expectant fathers to hospital". Barber concluded his review with positive comments about the rest of the series, singling out Ripley as being "reminiscent of Elaine in Seinfeld". A.A. Gill also criticised that episode's conclusion, comparing it to a Norman Wisdom comedy. On The Late Review, Germaine Greer described Nesbitt's acting as "especially awful" and suggested that the series had been developed by a marketing department.

Critical reaction improved with the third episode; writing in New Statesman, Andrew Billen praised Episode 3 as being "intricately constructed as a farce", and commented positively on Ripley's and Nesbitt's acting. Billen compared the production and fantasy scenes with Thirtysomething and Ally McBeal. In the Evening Standard, following the conclusion of Vanity Fair and prior to the broadcast of Episode 6, Billen wrote, "The style is light, the narrative frequently inconsequential. The men go to the pub and lust after the barmaid. The women meet in the wine bar and make fun of the men for lusting after the barmaid. The great settings are DIY stores, antenatal classes and sitting rooms. Why should anyone be interested? If domestic trivia has now been outlawed by the BBC as a subject for sitcoms and if even soap operas rely on murders and armed sieges to keep up their figures, why should the travails of a set of ex-dinkies have become a minor cult?" He analysed the series in relation to its early-middle-aged viewers being "a forgotten people", comparing the storylines to real-life issues experienced by friends. He concluded:

> This is not the world of Ally McBeal. It is not about finding love remedially. This is a world in which too many of us are asking what use is love if you find it too late. Yet somehow, probably because the moral judgments are lightly made, superannuated singletons such as myself can look on and see an advertisement for, rather than a warning against, that famously honourable estate—just as we do when we gaze at the more benign marriages of our friends. In Vanity Fair, Thackeray deliberately wrote a novel without a hero. We respond to Cold Feet because it, on the contrary, does not despise its characters.

Of Episode 6, The Mirror's Charlie Catchpole wrote "Although I wouldn't want to bump into any of these people in a wine bar, I found I really cared about their unravelling relationships, their sad sexual misadventures, their petty jealousies" and concluded by calling the series "Exquisitely written, stylishly produced, superbly performed." In The Times, Paul Hoggart summarised all six episodes as "[walking] a tightrope between satire and sentimentality, frequently falling off on the sugary side", but wrote positively of the writing, directing, acting, and editing. He approved of the deliberately unhappy ending, looking forward to seeing how Rachel's departure would be resolved in the second series. Andy Harries attributed the mixed critical reaction to the unusual timeslot the series was given.

### Awards

It won in the Situation Comedy and Comedy Drama category at the Royal Television Society (RTS) Awards, the Best Entertainment award at the Broadcasting Press Guild Awards, and the award for Best TV Comedy Drama at the 1999 British Comedy Awards. Edward Mansell received an RTS nomination for Best Tape and Film Editing in Entertainment and Situation Comedy. The third episode was nominated for the Golden Rose of Montreux, though did not win. Ian Johnson, the publicist for the series, believed that the European judges did not understand the farcical humour in the episode, noting that the British delegates to the festival were "helpless with laughter". The same episode was nominated for the 1999 Banff Rockie Award for Best Comedy—the only non-American series to receive a nomination in that category. It lost to the Ally McBeal episode "Theme of Life".

## Home media

The first two episodes were released on a single VHS tape on 11 October 1999. The other four episodes were scheduled for release over two more videos, to be released on 1 November and 29 November but were cancelled; the two-tape release of the full series came on 15 November. It was released on 2-disc region 2 DVD on 25 September 2000. A re-release, with new packaging and menus, came on 26 March 2006. The DVD was released in Australia on 4 February 2002 and in the United States on 25 January 2005. The pilot and first series were made available as free streaming media on ITV's revamped itv.com website from July 2007 to August 2009. Additionally, it was one of the first batch of series from ITV's archives to be made available for purchase on ITV's iTunes Store shop, introduced in April 2008.

First series of the British comedy-drama television


King of the Four Corners

King of the Four Corners of the World (Sumerian: lugal-an-ub-da-limmu-ba, Akkadian: šarru kibrat 'arbaim, šar kibrāti arba'i, or šar kibrāt erbetti), alternatively translated as King of the Four Quarters of the World, King of the Heaven's Four Corners or King of the Four Corners of the Universe and often shortened to simply King of the Four Corners, was a title of great prestige claimed by powerful monarchs in ancient Mesopotamia. Though the term "four corners of the world" does refer to specific geographical places within and near Mesopotamia itself, these places were (at the time the title was first used) thought to represent locations near the actual edges of the world and as such, the title should be interpreted as something equivalent to "King of all the known world", a claim to universal rule over the entire world and everything within it.

The title was first used by Naram-Sin of the Akkadian Empire in the 23rd century BC and was later used by the rulers of the Neo-Sumerian Empire, after which it fell into disuse. It was revived as a title by a number of Assyrian rulers, becoming especially prominent during the Neo-Assyrian Empire. The final ruler to claim the title was the first Persian Achaemenid king, Cyrus the Great, after his conquest of Babylon in 539 BC.

It is possible, at least among Assyrian rulers, that the title of King of the Four Corners was not inherited through normal means. As the title is not attested for all Neo-Assyrian kings and for some only attested several years into their reign it is possible that it might have had to be earned by each king individually, possibly through completing successful military campaigns in all four points of the compass. The similar title of šar kiššatim ("King of Everything" or "King of the Universe"), also with Akkadian origins and attested for some of the Neo-Assyrian kings, may have required seven successful military campaigns. The difference between the exact meaning of the two titles may have been that "King of the Universe" laid claim to the cosmological realm whereas "King of the Four Corners of the World" laid claim to the terrestrial.

## Meaning of "Four Corners of the World"

The term "four corners of the world" appears in several ancient mythologies and cosmologies, wherein it roughly corresponds the four points of the compass. In most of these representations, four principal rivers run to these four corners, their water irrigating the four quadrants (or quarters) of the world. In the view of the Mesopotamian Akkadians, the term referred to four regions on the edge of the then known world; Subartu (probably corresponding to the region of Assyria) in the north, Martu (roughly corresponding to modern Syria) in the west, Elam in the east and Sumer in the south. To Naram-Sin of Akkad (r. 2254–2218 BC), the creator of the title, it probably, in geographical terms, expressed his dominion over the regions Elam, Subartu, Amurru and Akkad (representing east, north, west and south respectively).

The term thus covers a somewhat clear geographical region, corresponding to Mesopotamia and its surroundings, but should be understood as referring to the entire known world. At the point in time when the title was first used, the 2200s BC, the Mesopotamians would have equated all of Mesopotamia to the entire world; the region was highly productive, densely populated and was bordered on all sides by seemingly empty and uninhabited lands. A title the like of King of the Four Corners of the World should be taken as meaning that its holder was the ruler of the entire Earth and everything within it. The title can be interpreted as being equivalent to calling oneself "King of all the known world". Thus, the title is an example of merism, combining contrasting concepts to refer to an entirety (the four corners being on the edges of the world and the title referring to them and everything in between).

## History

### Background (2900–2334 BC)

During the Early Dynastic Period in Mesopotamia (c. 2900–2350 BC), the rulers of the various city-states in the region would often launch invasions into regions and cities far from their own, at most times with negligible consequences for themselves, in order to establish temporary and small empires to either gain of keep a superior position relative to the other city-states. This early empire-building was encouraged as the most powerful monarchs were often rewarded with the most prestigious titles, such as the title of lugal (literally "big man" but often interpreted as "king", probably with military connotations). Most of these early rulers had probably acquired these titles rather than inherited them.

Eventually this quest to be more prestigious and powerful than the other city-states resulted in a general ambition for universal rule. Since Mesopotamia was equated to correspond to the entire world and Sumerian cities had been built far and wide (cities the like of Susa, Mari and Assur were located near the perceived corners of the world) it seemed possible to reach the edges of the world (at this time thought to be the lower sea, the Persian gulf, and the upper sea, the Mediterranean).

Rulers attempting to reach a position of universal rule became more common during the Early Dynastic IIIb period (c. 2450–2350 BC) during which two prominent examples are attested. The first, Lugalannemundu, king of Adab, is claimed by the Sumerian King List (though this is a much later inscription, making the extensive rule of Lugalennemundu somewhat doubtful) to have created a great empire covering the entirety of Mesopotamia, reaching from modern Syria to Iran, saying that he "subjugated the Four Corners". The second, Lugalzaggesi, king of Uruk, conquered the entirety of Lower Mesopotamia and claimed (despite this not being the case) that his domain extended from the upper to the lower sea. Lugalzaggesi was originally titled as simply "King of Uruk" and adopted the title "King of the Land" (Sumerian: lugal-kalam-ma) to lay claim to universal rule. This title had also been employed by some earlier Sumerian kings claiming control over all of Sumer, such as Enshakushanna of Uruk.

### Sumerian Kings of the Four Corners (2334–2004 BC)

Sargon, king of Akkad, unified Lower and Upper Mesopotamia, creating the first true Mesopotamian empire. Though Sargon most commonly used the title "King of Akkad" (šar māt Akkadi), he also introduced the more boastful title of šar kiššatim ("King of Everything" or "King of the Universe"), used prominently by his successors. The title of "King of the Four Corners of the World" is first attested to have been used by the Akkadian king Naram-Sin, the grandson of Sargon of Akkad and the fourth ruler of the Akkadian Empire. Naram-Sin also proclaimed himself to be a living god (the first Mesopotamian king to do so), making his capital of Akkad not only the political but also the religious center of the empire. It is possible that Naram-Sin might have been inspired to claim the title following his conquest of the city Ebla, in which quadripartite divisions of the world and the universe were prominent parts of the city's ideology and beliefs.

The title of King of the Four Corners suggests that Naram-Sin viewed himself not merely as a Mesopotamian ruler but as a universal ruler who happened to conform to the usual Mesopotamian royal traditions, the monarch of a new empire that not only incorporated the city-states of Mesopotamia but the lands beyond as well. In particular, art made during the period starts to incorporate previously unseen objects such as highland plants and animals and mountains, previously seen as highly foreign objects. Their increasing appearance in art suggests that they were seen as belonging to the empire of Akkad as much as everything else did. It is possible that šar kiššatim referred to the authority to govern the cosmological realm whilst "King of the Four Corners" referred to the authority to govern the terrestrial. Eitherway, the implication of these titles was that the Mesopotamian king was the king of the entire world.

The title doesn't appear to have been used by any of Naram-Sin's direct successors of the Akkadian Empire, which began to collapse during the reign of Naram-Sin's son Shar-Kali-Sharri. In the 2100s BC, the Gutians attacked the Akkadian Empire and supplanted the ruling "Sargonic" dynasty, destroying the city of Akkad and establishing an empire of their own. By 2112 BC, the Gutians had been driven out and the city of Ur had become the center of a new Sumerian civilization, referred to as the Third Dynasty of Ur or the Neo-Sumerian Empire. The rulers of this empire emulated the previous monarchs from Akkad, referring to themselves as "Kings of Sumer and Akkad" and all of them—with the exception of the founder of the dynasty, Ur-Nammu—used the title of "King of the Four Corners of the World". Some ancient sources confer the title onto Ur-Nammu as well, referring to him as "King in Heaven and the Four Corners of the World", but these inscriptions date to centuries after his reign.

### Assyrian Kings of the Four Corners (1366–627 BC)

With the collapse of the Neo-Sumerian Empire in c. 2004 BC, the title fell into disuse once more. Except for the Babylonian king Hammurabi who claimed to be "the king who made the four corners of the Earth obedient" in 1776 BC, the title was not used until occasionally by Assyrian kings of the Middle-Assyrian Empire, often as "King of All the Four Corners of the World" (šar kullat kibrāt erbetti).

The first king of the Neo-Assyrian Empire, Adad-nirari II (r. 911–891 BC), used the title of "King of the Four Corners". The concept of a king governing the four corners of the world was well-established by the reign of the second king of the Neo-Assyrian Empire, Tukulti-Ninurta II (r. 891–884 BC), who claimed to have been "he whose honoured name he has pronounced forever for the four corners" (ana mu urut kibrāt erbetti ana dāriš išquru) and "governor of the four corners" (muma'er kibrāt erbetti). In Assyria, the deity Ashur was referred to as "[the one] who makes the king's kingship surpass the kings of the four quarters" (mušarbû šarrūtija eli šarrāni ša kibrāt erbetti).

Tukulti-Ninurta II's son and successor, Ashurnasirpal II (r. 883–859 BC) is in different inscriptions twice referred to as “King of the Totality of the Four Corners including all their rulers” (šar kiššat kibrāte ša napḫar malkī kalîšunu). The title is also attested for his son and successor, Shalmaneser III (r. 859–824 BC) and is the only title applied to this king by his successors.

The Kition stele, a large basalt stele discovered on Cyprus and the westernmost ancient Assyrian artifact known, identifies the king Sargon II, (r. 722–705 BC) with many titles, including "King of the Universe", "King of Assyria", "King of Sumer and Akkad", "Governor of Babylon" and "King of the Four Corners of the World". Sargon II's son and heir Sennacherib (r. 705–681 BC) did not immediately inherit the title, referring to himself simply as the "unrivaled king" at the beginning of his reign. Sennacherib conducted several military campaigns during his reign, after which he routinely added titles to his titulary. After his third campaign he added "king of the world" and after conquests in the Mediterranean Sea and Persian Gulf in 694 BC he added the title "King from the Upper Sea of the Setting Sun to the Lower Sea of the Rising Sun". It was only after Sennacherib had conducted campaigns to the south, east, west and north during his fifth campaign that he replaced the title of "unrivaled king" with "King of the Four Corners of the World". Sennacherib's son and heir, Esarhaddon (r. 681–669 BC) also used the title of "King of the Four Corners of the World" alongside that of "King of the Universe".

Unlike the apparent dynastic inheritance of the title during the Neo-Sumerian Empire, it is possible that the title of King of the Four Corners had to be earned by each Assyrian king individually, thus explaining why the title is not attested for every Neo-Assyrian king and why Sennacherib first used it several years into his reign. British historian Stephanie Dalley, specializing in the Ancient Near East proposed in 1998 that the title may have had to be earned through the king successfully campaigning in all four points of the compass. Dalley also proposed that the similar title of "King of the Universe", with a virtually identical meaning, would have been earned through seven (which would have been connected to totality in the eyes of the Assyrians) successful campaigns. It would thus not have been possible for the king to claim either title before the required military campaigns. Periods during which the title was not used, such as the \~80-year gap between Shalmaneser III and Tiglath-Pileser III, probably reflect periods during which the military activity of the country and its kings declined.

### Cyrus the Great (539 BC)

After the fall of the Neo-Assyrian Empire in 609 BC, the principal power in Mesopotamia was the Neo-Babylonian Empire. The founder of the Neo-Babylonian Empire, Nabopolassar, wished to associate himself with the previous Assyrian rulers to establish continuity and assumed many of the same titles such as šarru dannu ("mighty king") and the much older Sumerian "King of Sumer and Akkad" (which had been used by the Neo-Assyrian rulers as well) but do not appear to have assumed the title of King of the Four Corners. Unlike previous ruling dynasties in Mesopotamia, the Neo-Babylonians usually only employed one royal title on any one occasion. Only rarely are examples with more than one royal title in use found from the Neo-Babylonian period, which might explain the absence of "King of the Four Corners..." since this was an additional prestigious title rather than a primary royal title. Nabopolassar's successors abandoned most of the old Assyrian titles, even abandoning the "mighty king" used by Nabopolassar. The only Neo-Babylonian king to assume the title of "King of the Four Corners" was Nabonidus, who in other aspects also tried to emulate the Assyrian kings.

The Neo-Babylonian Empire ended with the conquest of Babylon by the Persian king Cyrus the Great, founder of the Achaemenid Persian Empire, in 539 BC. The Cyrus Cylinder is an ancient clay cylinder written in Akkadian cuneiform script in the name of Cyrus, made to be used as a foundation deposit and buried in the walls of Babylon. In the text of the cylinder, Cyrus assumes several traditional Mesopotamian titles including those of "King of Babylon", "King of Sumer and Akkad" and "King of the Four Corners of the World". The title was not used after the reign of Cyrus but his successors did adopt similar titles. The popular regnal title "King of Kings", used by monarchs of Iran until the modern age, was originally a title introduced by the Assyrian Tukulti-Ninurta I in the 13th century BC (rendered šar šarrāni in Akkadian). The title of "King of Lands", also used by Assyrian monarchs since at least Shalmaneser III, was also adopted by Cyrus the Great and his successors. Titles such as "King of Kings" and "Great-King" (šarru rabu), ancient titles with the connotation of holding supreme power in the lands surrounding Babylon, would remain in use up until the Sassanid dynasty in Persia of the 3rd to 7th centuries.

## Examples of rulers who used the title

Kings of the Four Corners in the Akkadian Empire:

- Naram-Sin (r. 2254–2218 BC)

Kings of the Four Corners of the Gutian dynasty of Sumer:

- Erridupizir

Kings of the Four Corners in the Neo-Sumerian Empire:

- Utu-hengal
- Shulgi (r. 2094–2047 BC)
- Amar-Sin (r. 2046–2038 BC)
- Shu-Sin (r. 2037–2029 BC)
- Ibbi-Sin (r. 2028–2004 BC)

Kings of the Four Corners in Babylonia:

- Hammurabi (r. 1810–1750 BC) – referred to as the "king who made the four corners of the Earth obedient" in 1776 BC.
- Marduk-nadin-ahhe (r. 1099–1082 BC)
- Marduk-shapik-zeri (r. 1082–1069 BC)

Kings of the Four Corners in the Middle Assyrian Empire:

- Tukulti-Ninurta I (r. 1233–1197 BC)
- Tiglath-Pileser I (r. 1114–1076 BC)
- Ashur-bel-kala (r. 1074–1056 BC)

Kings of the Four Corners in the Neo-Assyrian Empire:

- Adad-nirari II (r. 911–891 BC)
- Tukulti-Ninurta II (r. 891–884 BC)
- Ashurnasirpal II (r. 883–859 BC)
- Shalmaneser III (r. 859–824 BC)
- Shamshi-Adad V (r. 824–811 BC)
- Tiglath-Pileser III (r. 745–727 BC)
- Shalmaneser V (r. 727–722 BC)
- Sargon II (r. 722–705 BC)
- Sennacherib (r. 705–681 BC) – claimed the title from 697 BC.
- Esarhaddon (r. 681–669 BC)
- Ashurbanipal (r. 669–631 BC)
- Shamash-shum-ukin (Neo-Assyrian king of Babylon, r. 667–648 BC)
- Ashur-etil-ilani (r. 631–627 BC)

Kings of the Four Corners in the Neo-Babylonian Empire:

- Nabonidus (r. 556–539 BC)

Kings of the Four Corners in the Achaemenid Empire:

- Cyrus the Great (r. 559–530 BC) – claimed the title from 539 BC.

Prestigious title from ancient Mesopotamia