Typically, this type of seizure lasts between 10 and 30 seconds. The person, most often a child aged 5 to 15, abruptly stops whatever he's doing (talking, walking) and appears to "stare into space." Absence seizures rarely cause a true convulsion in which the person falls down or collapses. Despite briefly losing consciousness, the person recovers fully with no lingering confusion or other ill effects. These "spells" may occur infrequently or several times per hour.
Absence seizures with age-related onset is genetic. About 15-40% of patients with these epilepsies have a family history of epilepsy; overall concordance in monozygotic twins is 74%, with a 100% concordance during the peak age of phenotypic expression. Family members may have other forms of idiopathic or genetic epilepsy (eg, febrile convulsions, generalized tonic-clonic seizures).