Electroencephalographic spiking activity, drug levels, and seizure occurrence in epileptic patients.

We investigated the relationships among the electroencephalographic spiking rate, drug levels, and seizure occurrence in 44 patients with focal epilepsy. Seizure occurrence was continuously monitored by personnel or videorecording and spiking rate was quantified by an automatic detection method. Results indicate that drug levels do not influence spiking rate, and spiking rate does not change before seizures but increases markedly after them, particularly secondarily generalized seizures. This increase can last several days and is observed during wakefulness and sleep. High or low spiking rates do not influence the occurrence of seizures. We suggest that interictal spikes may passively reflect damage to the brain, a damage which is worsened by further seizures. Spikes may not be directly related to seizure generation.