- Symptomatic febrile seizures [6] In Simple febrile seizure is single generalized seizure and lasts less than 15 minutes, The child is otherwise neurologically healthy and without neurologic abnormality by examination or by developmental history and not caused by meningitis, encephalitis, or any other illness affecting the brain . [6] Complex febrile seizure: This seizure is either focal or prolonged (ie, >15 min), or multiple seizures occur in close succession.[6]