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60-430: The term is often associated with a sudden traumatic loss of consciousness caused by a physical blow. Single powerful blows to the head (particularly the jawline and temple) can produce a cerebral concussion or a carotid sinus reflex with syncope and cause a sudden, dramatic KO. Body blows, particularly the liver punch , can cause progressive, debilitating pain that can also result in a KO. In boxing and kickboxing,

120-425: A broken bone ), air, cancer cells or clumps of bacteria (usually from infectious endocarditis ). Because an embolus arises from elsewhere, local therapy solves the problem only temporarily. Thus, the source of the embolus must be identified. Because the embolic blockage is sudden in onset, symptoms are usually maximal at the start. Also, symptoms may be transient as the embolus is partially resorbed and moves to

180-405: A severe headache . The symptoms of stroke can be permanent. Long-term complications may include pneumonia and loss of bladder control . The biggest risk factor for stroke is high blood pressure . Other risk factors include high blood cholesterol , tobacco smoking , obesity , diabetes mellitus , a previous TIA , end-stage kidney disease , and atrial fibrillation . Ischemic stroke

240-473: A CT scan. Other tests such as an electrocardiogram (ECG) and blood tests are done to determine risk factors and possible causes. Low blood sugar may cause similar symptoms. Prevention includes decreasing risk factors, surgery to open up the arteries to the brain in those with problematic carotid narrowing , and anticoagulant medication in people with atrial fibrillation . Aspirin or statins may be recommended by physicians for prevention. Stroke

300-463: A boxer automatically wins by TKO if his opponent is knocked down four times in an entire match. In MMA bouts, the referee may declare a TKO if a fighter cannot intelligently defend themselves while being repeatedly struck. A double knockout (DKO), both in real-life combat sports and in fighting -based video games , occurs when both fighters trade blows and knock each other out simultaneously and are both unable to continue fighting. In such cases,

360-444: A complete blockage of one of the carotid arteries, the risk of stroke on that side is about one percent per year. A special form of embolic stroke is the embolic stroke of undetermined source (ESUS). This subset of cryptogenic stroke is defined as a non-lacunar brain infarct without proximal arterial stenosis or cardioembolic sources. About one out of six cases of ischemic stroke could be classified as ESUS. Cerebral hypoperfusion

420-441: A different location or dissipates altogether. Emboli most commonly arise from the heart (especially in atrial fibrillation ) but may originate from elsewhere in the arterial tree. In paradoxical embolism , a deep vein thrombosis embolizes through an atrial or ventricular septal defect in the heart into the brain. Causes of stroke related to the heart can be distinguished between high- and low-risk: Among those who have

480-400: A high risk for ischemic stroke. There are two main types of hemorrhagic stroke: The above two main types of hemorrhagic stroke are also two different forms of intracranial hemorrhage , which is the accumulation of blood anywhere within the cranial vault ; but the other forms of intracranial hemorrhage, such as epidural hematoma (bleeding between the skull and the dura mater , which is

540-517: A knockout is usually awarded when one participant falls to the canvas and is unable to rise to their feet within a specified period of time, typically because of exhaustion, pain, disorientation, or unconsciousness . For example, if a boxer is knocked down and is unable to continue the fight within a ten-second count, they are counted as having been knocked out and their opponent is awarded the KO victory. In mixed martial arts (MMA) competitions, no time count

600-441: A person, when asked to raise both arms, involuntarily lets one arm drift downward) and abnormal speech are the findings most likely to lead to the correct identification of a case of stroke, increasing the likelihood by 5.5 when at least one of these is present. Similarly, when all three of these are absent, the likelihood of stroke is decreased (– likelihood ratio of 0.39). While these findings are not perfect for diagnosing stroke,

660-452: A problem. Its appearance makes it advisable to seek medical review and to consider prevention against stroke . In thrombotic stroke, a thrombus (blood clot) usually forms around atherosclerotic plaques. Since blockage of the artery is gradual, onset of symptomatic thrombotic stroke is slower than that of hemorrhagic stroke. A thrombus itself (even if it does not completely block the blood vessel) can lead to an embolic stroke (see below) if

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720-540: A severe headache known as a thunderclap headache ) or reveal evidence of a previous head injury . Stroke may be preceded by premonitory symptoms, which may indicate a stroke is imminent. These symptoms may include dizziness, dysarthria (speech disorder), exhaustion, hemiparesis (weakness on one side of the body), paresthesia (tingling, pricking, chilling, burning, numbness of the skin), pathological laughter, seizure that turns into paralysis, "thunderclap" headache, or vomiting. Premonitory symptoms are not diagnostic of

780-443: A situation can be accepted as a defense; it can vary from case to case. Hence epileptic seizures , neurological dysfunctions and sleepwalking may be considered acceptable excusing conditions because the loss of control is not foreseeable, but falling asleep (especially while driving or during any other safety-critical activity) may not, because natural sleep rarely overcomes an ordinary person without warning. In many countries, it

840-432: A stroke, and may be a sign of other illness. Assessing onset (gradual or sudden), duration, and the presence of other associated symptoms are important, and premonitory symptoms may not appear at all or may vary depending on the type of stroke. Stroke symptoms typically start suddenly, over seconds to minutes, and in most cases do not progress further. The symptoms depend on the area of the brain affected. The more extensive

900-519: A stroke. In 2021, stroke was the third biggest cause of death, responsible for approximately 10% of total deaths. In 2015, there were about 42.4 million people who had previously had stroke and were still alive. Between 1990 and 2010 the annual incidence of stroke decreased by approximately 10% in the developed world , but increased by 10% in the developing world. In 2015, stroke was the second most frequent cause of death after coronary artery disease , accounting for 6.3 million deaths (11% of

960-415: A subarachnoid hemorrhage or an embolic stroke. If the area of the brain affected includes one of the three prominent central nervous system pathways —the spinothalamic tract , corticospinal tract , and the dorsal column–medial lemniscus pathway , symptoms may include: In most cases, the symptoms affect only one side of the body (unilateral). The defect in the brain is usually on the opposite side of

1020-445: Is a medical emergency. Ischemic strokes, if detected within three to four-and-a-half hours, may be treatable with medication that can break down the clot , while hemorrhagic strokes sometimes benefit from surgery . Treatment to attempt recovery of lost function is called stroke rehabilitation , and ideally takes place in a stroke unit; however, these are not available in much of the world. In 2023, 15 million people worldwide had

1080-400: Is a related syndrome of stroke symptoms that resolve completely within 24 hours. With the availability of treatments that can reduce stroke severity when given early, many now prefer alternative terminology, such as "brain attack" and "acute ischemic cerebrovascular syndrome" (modeled after heart attack and acute coronary syndrome , respectively), to reflect the urgency of stroke symptoms and

1140-407: 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 result of traumatic brain injury , brain hypoxia (inadequate oxygen, possibly due to a brain infarction or cardiac arrest ), severe intoxication with drugs that depress

1200-461: Is also used if the fighter is hanging on to the ropes, caught between the ropes, or is hanging over the ropes and is unable to fall to the floor and cannot protect himself. A knockdown triggers a count by the referee (normally to 10); if the fighter fails the count, then the fight is ended as a KO. A flash knockdown is a knockdown in which the fighter hits the canvas but is not noticeably hurt or affected. Unconsciousness Unconsciousness

1260-409: Is an irritant which could potentially destroy cells since it is an acid and disrupts the normal acid-base balance in the brain. The ischemia area is referred to as the "ischemic penumbra ". After the initial ischemic event the penumbra transitions from a tissue remodeling characterized by damage to a remodeling characterized by repair. As oxygen or glucose becomes depleted in ischemic brain tissue,

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1320-643: Is declared when the referee decides during a round that a fighter cannot safely continue the match for any reason. Certain sanctioning bodies also allow the official attending physician at ringside to stop the fight as well. In amateur boxing, and in many regions professionally, including championship fights sanctioned by the World Boxing Association (WBA), a TKO is declared when a fighter is knocked down three times in one round (called an "automatic knockout" in WBA rules). Furthermore, in amateur boxing,

1380-412: Is given after a knockdown, as the sport allows submission grappling as well as ground and pound . If a fighter loses consciousness ("goes limp") as a result of legal strikes, it is declared a KO. Even if the fighter loses consciousness for a brief moment and wakes up again to continue to fight, the fight is stopped and a KO is declared. As many MMA fights can take place on the mat rather than standing, it

1440-442: Is less reliable in the recognition of posterior circulation stroke. The revised mnemonic BE FAST , which adds balance (sudden trouble keeping balance while walking or standing) and eyesight (new onset of blurry or double vision or sudden, painless loss of sight) to the assessment, has been proposed to address this shortcoming and improve early detection of stroke even further. Other scales for prehospital detection of stroke include

1500-416: Is possible to score a KO via ground and pound, a common victory for grapplers . In fighting games such as Street Fighter and Tekken , a player scores a knockout by fully depleting the opponent's health bar , with the victor being awarded the round. The player who wins the most rounds, either by scoring the most knockouts or by having more vitality remaining when time expires during each round, wins

1560-513: Is presumed that someone who is less than fully conscious cannot give consent to anything. This can be relevant in cases of sexual assault , euthanasia , or patients giving informed consent with regard to starting or stopping a medical treatment. Stroke Stroke is a medical condition in which poor blood flow to a part of the brain causes cell death . There are two main types of stroke: ischemic , due to lack of blood flow, and hemorrhagic , due to bleeding . Both cause parts of

1620-409: Is the reduction of blood flow to all parts of the brain. The reduction could be to a particular part of the brain depending on the cause. It is most commonly due to heart failure from cardiac arrest or arrhythmias , or from reduced cardiac output as a result of myocardial infarction , pulmonary embolism , pericardial effusion , or bleeding. Hypoxemia (low blood oxygen content) may precipitate

1680-447: Is the second leading cause of death in people under 20 with sickle-cell anemia. Air pollution may also increase stroke risk. An embolic stroke refers to an arterial embolism (a blockage of an artery) by an embolus , a traveling particle or debris in the arterial bloodstream originating from elsewhere. An embolus is most frequently a thrombus, but it can also be a number of other substances including fat (e.g., from bone marrow in

1740-522: Is typically caused by blockage of a blood vessel, though there are also less common causes. Hemorrhagic stroke is caused by either bleeding directly into the brain or into the space between the brain's membranes . Bleeding may occur due to a ruptured brain aneurysm . Diagnosis is typically based on a physical exam and supported by medical imaging such as a CT scan or MRI scan . A CT scan can rule out bleeding, but may not necessarily rule out ischemia, which early on typically does not show up on

1800-422: The cerebral cortex is involved, the central nervous system pathways can again be affected, but can also produce the following symptoms: If the cerebellum is involved, ataxia might be present and this includes: In the days before a stroke (generally in the previous 7 days, even the previous one), a considerable proportion of patients have a "sentinel headache": a severe and unusual headache that indicates

1860-650: The Los Angeles Prehospital Stroke Screen (LAPSS) and the Cincinnati Prehospital Stroke Scale (CPSS), on which the FAST method was based. Use of these scales is recommended by professional guidelines. For people referred to the emergency room , early recognition of stroke is deemed important as this can expedite diagnostic tests and treatments. A scoring system called ROSIER (recognition of stroke in

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1920-538: The World Health Organization defined "stroke" as a "neurological deficit of cerebrovascular cause that persists beyond 24 hours or is interrupted by death within 24 hours", although the word "stroke" is centuries old. This definition was supposed to reflect the reversibility of tissue damage and was devised for the purpose, with the time frame of 24 hours being chosen arbitrarily. The 24-hour limit divides stroke from transient ischemic attack , which

1980-487: The ventricular system , CSF or the pial surface. A third of intracerebral bleed is into the brain's ventricles. ICH has a mortality rate of 44 percent after 30 days, higher than ischemic stroke or subarachnoid hemorrhage (which technically may also be classified as a type of stroke ). Other causes may include spasm of an artery. This may occur due to cocaine . Cancer is also another well recognized potential cause of stroke. Although, malignancy in general can increase

2040-461: The Bamford or Oxford classification) relies primarily on the initial symptoms; based on the extent of the symptoms, the stroke episode is classified as total anterior circulation infarct (TACI), partial anterior circulation infarct (PACI), lacunar infarct (LACI) or posterior circulation infarct (POCI). These four entities predict the extent of the stroke, the area of the brain that is affected,

2100-464: The activity of the central nervous system (e.g., alcohol and other hypnotic or sedative drugs), severe fatigue , pain , anaesthesia , and other causes. Loss of consciousness should not be confused with the notion of the psychoanalytic unconscious , cognitive processes that take place outside awareness (e.g., implicit cognition ), and with altered states of consciousness such as sleep , delirium , hypnosis , and other altered states in which

2160-501: The area of the brain affected, the more functions that are likely to be lost. Some forms of stroke can cause additional symptoms. For example, in intracranial hemorrhage, the affected area may compress other structures. Most forms of stroke are not associated with a headache , apart from subarachnoid hemorrhage and cerebral venous thrombosis and occasionally intracerebral hemorrhage. Systems have been proposed to increase recognition of stroke. Sudden-onset face weakness, arm drift (i.e., if

2220-408: The blood supply to the brain, while hemorrhagic stroke results from the rupture of a blood vessel or an abnormal vascular structure . About 87% of stroke is ischemic, with the rest being hemorrhagic. Bleeding can develop inside areas of ischemia, a condition known as " hemorrhagic transformation ." It is unknown how many cases of hemorrhagic stroke actually start as ischemic stroke. In the 1970s

2280-401: The blood supply by narrowing the lumen of blood vessels leading to a reduction of blood flow by causing the formation of blood clots within the vessel or by releasing showers of small emboli through the disintegration of atherosclerotic plaques. Embolic infarction occurs when emboli formed elsewhere in the circulatory system, typically in the heart as a consequence of atrial fibrillation, or in

2340-471: The body. However, since these pathways also travel in the spinal cord and any lesion there can also produce these symptoms, the presence of any one of these symptoms does not necessarily indicate stroke. In addition to the above central nervous system pathways, the brainstem gives rise to most of the twelve cranial nerves . A brainstem stroke affecting the brainstem and brain, therefore, can produce symptoms relating to deficits in these cranial nerves: If

2400-567: The brain and places the person at increased risk for both transient ischemic attack and major stroke in the future. Conversely, those who have had major stroke are also at risk of having silent stroke. In a broad study in 1998, more than 11 million people were estimated to have experienced stroke in the United States. Approximately 770,000 of these were symptomatic and 11 million were first-ever silent MRI infarcts or hemorrhages . Silent stroke typically causes lesions which are detected via

2460-461: The brain to stop functioning properly. Signs and symptoms of stroke may include an inability to move or feel on one side of the body , problems understanding or speaking , dizziness , or loss of vision to one side . Signs and symptoms often appear soon after the stroke has occurred. If symptoms last less than 24 hours, the stroke is a transient ischemic attack (TIA), also called a mini-stroke. Hemorrhagic stroke may also be associated with

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2520-426: The carotid arteries, break off, enter the cerebral circulation, then lodge in and block brain blood vessels. Since blood vessels in the brain are now blocked, the brain becomes low in energy, and thus it resorts to using anaerobic metabolism within the region of brain tissue affected by ischemia. Anaerobic metabolism produces less adenosine triphosphate (ATP) but releases a by-product called lactic acid . Lactic acid

2580-424: The cells of the nervous system is normally kept low by so-called uptake carriers, which are powered by the concentration gradients of ions (mainly Na ) across the cell membrane. However, stroke cuts off the supply of oxygen and glucose which powers the ion pumps maintaining these gradients. As a result, the transmembrane ion gradients run down, and glutamate transporters reverse their direction, releasing glutamate into

2640-411: The emergency room) is recommended for this purpose; it is based on features from the medical history and physical examination. Loss of consciousness , headache , and vomiting usually occur more often in hemorrhagic stroke than in thrombosis because of the increased intracranial pressure from the leaking blood compressing the brain. If symptoms are maximal at onset, the cause is more likely to be

2700-516: The face and the chin tucked in. This may still be ineffective if the opponent punches effectively to the solar plexus . A fighter who becomes unconscious from a strike with sufficient knockout power is referred to as having been knocked out or KO'd ( kay-ohd ). Losing balance without losing consciousness is referred to as being knocked down ("down but not out"). Repeated blows to the head, regardless of whether they cause loss of consciousness, may in severe cases cause strokes or paralysis in

2760-721: The fact that they can be evaluated relatively rapidly and easily make them very valuable in the acute setting. A mnemonic to remember the warning signs of stroke is FAST (facial droop, arm weakness, speech difficulty, and time to call emergency services), as advocated by the Department of Health (United Kingdom) and the Stroke Association , the American Stroke Association , and the National Stroke Association (US). FAST

2820-535: The hypoperfusion. Because the reduction in blood flow is global, all parts of the brain may be affected, especially vulnerable "watershed" areas—border zone regions supplied by the major cerebral arteries. A watershed stroke refers to the condition when the blood supply to these areas is compromised. Blood flow to these areas does not necessarily stop, but instead it may lessen to the point where brain damage can occur. Cerebral venous sinus thrombosis leads to stroke due to locally increased venous pressure, which exceeds

2880-423: The immediacy, and over time have been linked to permanent neurodegenerative diseases such as chronic traumatic encephalopathy ("punch-drunk syndrome"). Because of this, many physicians advise against sports involving knockouts. A knockdown occurs when a fighter touches the floor of the ring with any part of the body other than the feet following a hit, but is able to rise back up and continue fighting. The term

2940-431: The match is declared a draw. Little is known as to what exactly causes one to be knocked unconscious, but many agree it is related to trauma to the brain stem . This usually happens when the head rotates sharply, often as a result of a strike. There are three general manifestations of such trauma: A basic principle of boxing and other combat sports is to defend against this vulnerability by keeping both hands raised about

3000-464: The match. This differs from combat sports in reality, where a knockout ends the match immediately. However, some fighting games aim for a more realistic experience, with titles like Fight Night adhering to the rules of professional boxing, although technically they are classified as sports games , and share many of the same features as NFL and NBA video games. A technical knockout ( TKO or T.K.O. ), stoppage , or referee stopped contest (RSC)

3060-482: The need to act swiftly. During ischemic stroke, blood supply to part of the brain is decreased, leading to dysfunction of the brain tissue in that area. There are four reasons why this might happen: Stroke without an obvious explanation is termed cryptogenic stroke ( idiopathic ); this constitutes 30–40% of all cases of ischemic stroke. There are classification systems for acute ischemic stroke. The Oxford Community Stroke Project classification (OCSP, also known as

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3120-479: The person responds to stimuli, including trance and psychedelic experiences . This is not a complete list. In jurisprudence , unconsciousness may entitle the criminal defendant to the defense of automatism , i.e. a state without control of one's own actions, an excusing condition that allows a defendant to argue that they should not be held criminally liable for their actions or omissions . In most countries, courts must consider whether unconsciousness in

3180-721: The pressure generated by the arteries. Infarcts are more likely to undergo hemorrhagic transformation (leaking of blood into the damaged area) than other types of ischemic stroke. It generally occurs in small arteries or arterioles and is commonly due to hypertension, intracranial vascular malformations (including cavernous angiomas or arteriovenous malformations ), cerebral amyloid angiopathy , or infarcts into which secondary hemorrhage has occurred. Other potential causes are trauma, bleeding disorders , amyloid angiopathy , illicit drug use (e.g., amphetamines or cocaine ). The hematoma enlarges until pressure from surrounding tissue limits its growth, or until it decompresses by emptying into

3240-423: The production of high energy phosphate compounds such as adenosine triphosphate (ATP) fails, leading to failure of energy-dependent processes (such as ion pumping) necessary for tissue cell survival. This sets off a series of interrelated events that result in cellular injury and death. A major cause of neuronal injury is the release of the excitatory neurotransmitter glutamate. The concentration of glutamate outside

3300-462: The risk of stroke, certain types of cancer such as pancreatic, lung and gastric are typically associated with a higher thromboembolism risk. The mechanism with which cancer increases stroke risk is thought to be secondary to an acquired hypercoagulability . Silent stroke is stroke that does not have any outward symptoms, and people are typically unaware they had experienced stroke. Despite not causing identifiable symptoms, silent stroke still damages

3360-592: The thick outermost layer of the meninges that surround the brain) and subdural hematoma (bleeding in the subdural space ), are not considered "hemorrhagic stroke". Hemorrhagic stroke may occur on the background of alterations to the blood vessels in the brain, such as cerebral amyloid angiopathy , cerebral arteriovenous malformation and an intracranial aneurysm , which can cause intraparenchymal or subarachnoid hemorrhage. In addition to neurological impairment, hemorrhagic stroke usually causes specific symptoms (for instance, subarachnoid hemorrhage classically causes

3420-479: The thrombus breaks off and travels in the bloodstream, at which point it is called an embolus . Two types of thrombosis can cause stroke: Anemia causes increase blood flow in the blood circulatory system. This causes the endothelial cells of the blood vessels to express adhesion factors which encourages the clotting of blood and formation of thrombus. Sickle-cell anemia , which can cause blood cells to clump up and block blood vessels, can also lead to stroke. Stroke

3480-402: The total). About 3.0 million deaths resulted from ischemic stroke while 3.3 million deaths resulted from hemorrhagic stroke. About half of people who have had stroke live less than one year. Overall, two thirds of cases of stroke occurred in those over 65 years old. Stroke can be classified into two major categories: ischemic and hemorrhagic . Ischemic stroke is caused by interruption of

3540-691: The underlying cause, and the prognosis. The TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification is based on clinical symptoms as well as results of further investigations; on this basis, stroke is classified as being due to (1) thrombosis or embolism due to atherosclerosis of a large artery, (2) an embolism originating in the heart , (3) complete blockage of a small blood vessel, (4) other determined cause, (5) undetermined cause (two possible causes, no cause identified, or incomplete investigation). Users of stimulants such as cocaine and methamphetamine are at

3600-407: The use of neuroimaging such as MRI . Silent stroke is estimated to occur at five times the rate of symptomatic stroke. The risk of silent stroke increases with age, but they may also affect younger adults and children, especially those with acute anemia . Ischemic stroke occurs because of a loss of blood supply to part of the brain, initiating the ischemic cascade . Atherosclerosis may disrupt

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