Recurrence

Fischer 2014 Recurrence risk is a function of time, such that the longer the time since the last seizure, the lower the risk. Otherwise, the Task Force did not agree on a specific interval of time between seizures that would “reset the clock” for counting an event as a second seizure. A rationale for setting such an interval might emerge from future research. Recurrence risk depends on the type of epilepsy, age, syndrome, etiology, treatment, and many other factors. The risk of seizure recurrence after unprovoked seizures diminishes with time, although the risk may never reach levels for normal individuals who have not had a prior seizure.Most relapses are early. After a single unprovoked seizure, 80%14,17 to 90%25 of those who had a second did so within 2 years. In one study,5 after a second unprovoked seizure, subsequent seizures occurred within 4 years, but none in the ensuing 3 years, suggesting that the risk may not be zero but is low. The National General Practice Study of Epilepsy in the United Kingdom14 identified a 3-year recurrence risk of 44% after a seizure-free period of 6 months, 32% after 12 months,and 17% after 18 months. No adequate data are available on seizure recurrence risk after being seizure-free and off medication for extended periods of time. Delayed relapses are rare after 5 years. By 10 years off antiseizure medicines, the annual risk for seizures probably is very low.