Post-traumatic Seizure - Epidemiology

Epidemiology

Research has found that the incidence of PTS varies widely based on the population studied; it may be as low as 4.4% or as high as 53%. Of all TBI patients who are hospitalized, 5 to 7% have PTS. PTS occur in about 3.1% of traumatic brain injuries, but the severity of injury affects the likelihood of occurrence.

The most important factor in whether a person will develop early and late seizures is the extent of the damage to the brain. More severe brain injury also confers a risk for developing PTS for a longer time after the event. One study found that the probability that seizures will occur within 5 years of injury is in 0.5% of mild traumatic brain injuries (defined as no skull fracture and less than 30 minutes of post-traumatic amnesia, abbreviated PTA, or loss of consciousness, abbreviated LOC); 1.2% of moderate injuries (skull fracture or PTA or LOC lasting between 30 minutes and 24 hours); and 10.0% of severe injuries (cerebral contusion, intracranial hematoma, or LOC or PTA for over 24 hours). Another study found that the risk of seizures 5 years after TBI is 1.5% in mild (defined as PTA or LOC for less than 30 minutes), 2.9% in moderate (LOC lasting between 30 minutes and 1 day), and 17.2% in severe TBI (cerebral contusion, subdural hematoma, or LOC for over a day; image at right).

Immediate seizures have an incidence of 1 to 4%, that of early seizures is 4 to 25%, and that of late seizures is 9 to 42%.

Age influences the risk for PTS. As age increases, risk of early and late seizures decreases; one study found that early PTS occurred in 30.8% of children age 7 or under, 20% of children between ages 8 and 16, and 8.4% of people who were over 16 at the time they were injured (graph at right). Early seizures occur up to twice as frequently in brain injured children as they do in their adult counterparts. In one study, children under five with trivial brain injuries (those with no LOC, no PTA, no depressed skull fracture, and no hemorrhage) suffered an early seizure 17% of the time, while people over age 5 did so only 2% of the time. Children under age five also have seizures within one hour of injury more often than adults do. One study found the incidence of early seizures to be highest among infants younger than one year and particularly high among those who suffered perinatal injury. However, adults are at higher risk than children are for late seizures. People over age 65 are also at greater risk for developing PTS after an injury, with a PTS risk that is 2.5 times higher than that of their younger counterparts.