CURRENT REVIEW IN BASIC SCIENCE Do Interictal Spikes Sustain Seizures and Epileptogenesis?

Interictal spiking is seen in the EEG of epileptic patients between seizures. To date, the roles played by interictal events in seizure occurrence and in epileptogenesis remain elusive. While interictal spikes may herald the onset of electrographic seizures, experimen-tal data indicate that hippocampus-driven interictal events pre-vent seizure precipitation. Even less clear than the role of interictal events in seizure occurrence is whether and how interictal spikes contribute to epileptogenesis. Thus, while plastic changes within limbic neuronal networks may result from ongoing interictal ac-tivity, experimental evidence supports the view that epileptogene-sis is accompanied by a decrease in hippocampus-driven interictal activity. The EEG of patients presenting with partial seizures is characterized by brief, epileptic spikes that are not associated with evident clinical symptoms. The interictal spiking is valu-able for diagnosing the epileptic condition, and when required, for localizing the epileptogenic area. Interictal and ictal dis-charges in animal models of epileptiform activity consist of similar (but for duration) neuronal depolarizations, leading to sustained action potential firing (1–4), suggesting that interictal and ictal events may reflect similar neuronal mechanisms. More-over, interictal spikes may herald the onset of electrographic seizures. However, the precise relationship between interictal and ictal activity remains ambiguous, as careful studies per