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 red flags are warning signs that may indicate a more serious problem and require immediate emergency medical attention red flag symptoms (emergent assessment required) seizure or convulsions worsening headache difficulty waking up (or loss of consciousness) seeing double problem recognizing people or places or confusion repeated vomiting numbness, weakness in extremities, or slurred speech not usual self, aggressive, or agitated behaviour neck pain or tenderness in the neck unequal pupil size is not a sign of concussion and can be a sign of a more serious brain injury. 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, persistent 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 (pta; 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 (loc), post-traumatic amnesia (pta), and the glasgow coma scale (gcs). 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 main article: prevention of concussions prevention of mtbi involves general measures such as wearing seat belts, using airbags in cars, protective equipment such as helmets for high-risk sports, and earthquake preparedness such as covering and holding under the table during an earthquake. 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