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Post-traumatic seizures (PTS) are seizures that result from traumatic brain injury (TBI), brain damage caused by physical trauma. PTS may be a risk factor for post-traumatic epilepsy (PTE), but a person who has a seizure or seizures due to traumatic brain injury does not necessarily have PTE, which is a form of epilepsy, a chronic condition in which seizures occur repeatedly. However, "PTS" and "PTE" may be used interchangeably in medical literature.〔 Seizures are usually an indication of a more severe TBI.〔 Seizures that occur shortly after a person suffers a brain injury may further damage the already vulnerable brain.〔 They may reduce the amount of oxygen available to the brain,〔 cause excitatory neurotransmitters to be released in excess, increase the brain's metabolic need, and raise the pressure within the intracranial space, further contributing to damage.〔 Thus, people who suffer severe head trauma are given anticonvulsant medications as a precaution against seizures.〔 Around 5–7% of people hospitalized with TBI have at least one seizure.〔 PTS are more likely to occur in more severe injuries, and certain types of injuries increase the risk further. The risk that a person will suffer PTS becomes progressively lower as time passes after the injury. However, TBI survivors may still be at risk over 15 years after the injury.〔 Children and older adults are at a higher risk for PTS. ==Classification== In the mid 1970s, PTS was first classified by Bryan Jennett into early and late seizures, those occurring within the first week of injury and those occurring after a week, respectively.〔 〕 Though the seven day cutoff for early seizures is used widely, it is arbitrary; seizures occurring after the first week but within the first month of injury may share characteristics with early seizures.〔 Some studies use a 30 day cutoff for early seizures instead.〔 〕 Later it became accepted to further divide seizures into immediate PTS, seizures occurring within 24 hours of injury; early PTS, with seizures between a day and a week after trauma; and late PTS, seizures more than one week after trauma.〔 Some consider late PTS to be synonymous with post-traumatic epilepsy.〔 〕 Early PTS occur at least once in about 4 or 5% of people hospitalized with TBI, and late PTS occur at some point in 5% of them.〔 〕 Of the seizures that occur within the first week of trauma, about half occur within the first 24 hours.〔 In children, early seizures are more likely to occur within an hour and a day of injury than in adults.〔 Of the seizures that occur within the first four weeks of head trauma, about 10% occur after the first week.〔 Late seizures occur at the highest rate in the first few weeks after injury.〔 About 40% of late seizures start within six months of injury, and 50% start within a year.〔 Especially in children and people with severe TBI, the life-threatening condition of persistent seizure called status epilepticus is a risk in early seizures; 10 to 20% of PTS develop into the condition.〔 In one study, 22% of children under 5 years old developed status seizures, while 11% of the whole TBI population studied did.〔 〕 Status seizures early after a TBI may heighten the chances that a person will suffer unprovoked seizures later.〔
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