Electrographic high-frequency activity and epilepsy.

High-frequency electrographic activity (HFA) has a frequency of 80-600Hz. It can be observed interictally in epileptic foci and also at the onset of epileptic seizures. There are several hypotheses about how HFA is generated, and it has been suggested that the underlying mechanisms may play an important role in epileptogenesis and ictogenesis. The high specificity of HFA for epileptic foci is now used during presurgical evaluation to help localize epileptic focus. In this article we review the current state of knowledge regarding this phenomenon and challenges for the future studies focusing on HFA.