Spatiotemporal relationship between seizure activity and interictal spikes in temporal lobe epilepsy

Purpose: To analyze the spatio-temporal relationship between seizure propagation and interictal epileptiform discharges (IEDs) in patients with bitemporal epilepsy. Methods: We investigated 18 adult patients with intractable temporal lobe epilepsy (TLE) who had undergone continuos video-EEG monitoring during presurgical evaluation. Only those patients were selected who had independent IEDs over both temporal lobes. Two authors evaluated the ictal and interictal EEG data independently. Results: We analyzed 52 lateralized seizures of 18 patients. Thirty-one seizures showed ipsilateral seizure spread exclusively, whereas in 21 seizures the contralateral. hemisphere was also involved. In lateralized seizures without contralateral propagation, we found that spikes ipsilateral to the seizure onset occurred postictally in a greater ratio than preictally (P < 0.001). In lateralized seizures with contralateral propagation, we found no significant changes in the postictal spike distribution. Conclusions: Our findings showed that the lateralization of IEDs may depend on the brain areas involved by the preceding seizures, suggesting that spikes can be influenced by the seizure activity, and are not independent signs of epileptogenicity. (C) 2001 Elsevier Science B.V. All rights reserved.