A simple absence seizure causes a vacant stare, which may be mistaken for a brief lapse in attention. The seizure lasts about 10 seconds, though it may last as long as 30 seconds. There's no confusion, headache or drowsiness after the seizure. Symptoms of absence seizures include: A sudden stop in activity without falling. Lip smacking. Eyelid flutters. Chewing motions. Finger rubbing. Small movements of both hands.