Absences in adult seizure disorders.

From a phenomenological point of view, absence seizures refer to any type of epileptic event characterized by loss of awareness and responsiveness. However, a phenomenological definition of absence seizures is hampered by difficulties in conceptualizing consciousness and needs to take into account the electroclinical features and anatomical basis of seizures. Sensu stricto, absence seizures are defined as an electroclinical pattern of generalized 3/s spike-wave activity accompanied by loss of awareness and responsiveness. Although there is general belief that absences are most often encountered in childhood or early adolescence, a considerable number of patients suffer from absences late into adulthood, which are often refractory to antiepileptic drugs. These patients generally fall into one of two groups. The first group consists of those who have more or less typical absences in childhood or adolescence which continue into adulthood, and may be accompanied by other generalized seizures or neurological impairment. Few data are available addressing whether the seizure semiology of the absences in these patients changes over time or not. The second class of patients corresponds to those in whom absences emerge for the first time in adulthood or even in the senium. These need to be carefully distinguished from later aggravation or semiological transformation of undiagnosed childhood epilepsies and from certain complex focal seizures originating from the frontal or temporal lobe. A wide range of aetiologically and anatomically diverse processes may lead to the appearance of epileptic absences. It is important to note that absences also vary in their intensity, their impact on the ability of the subject to respond and react, and in particular in their natural history and their response to antiepileptic medication.