Nov 30, · Age younger than 16 years: The risk in this age group is almost double the risk of recurrent seizures in adolescents and adults aged years. Remote symptomatic seizure [10, 11, 12]: In the case of seizures after a first stroke, lesion location and stroke subtype are strong predictors of early seizure risk, and early . Known Causes of Seizures in Adults. by DR. TINA M. ST. JOHN Aug. 14, The occurrence of new onset seizure activity in an adult may be a symptom of a brain tumor. A seizure is a burst of electrical activity in your brain. A seizure may start in one part of your brain, or both sides may be affected. The seizure may last a few seconds or up to 5 minutes. A new-onset seizure is a seizure that happens for the first time. You have a higher risk for another seizure.