Mechanisms underlying seizure generation are traditionally thought to act over seconds to minutes before clinical seizure onset. We analyzed continuous 3- to 14-day intracranial EEG recordings from five patients with mesial temporal lobe epilepsy obtained during evaluation for epilepsy surgery. We found localized quantitative EEG changes identifying prolonged bursts of complex epileptiform discharges that became more prevalent 7 hr before seizures and highly localized subclinical seizure-like activity that became more frequent 2 hr prior to seizure onset. Accumulated energy increased in the 50 min before seizure onset, compared to baseline. These observations, from a small number of patients, suggest that epileptic seizures may begin as a cascade of electrophysiological events that evolve over hours and that quantitative measures of preseizure electrical activity could possibly be used to predict seizures far in advance of clinical onset.
Bibliographical noteFunding Information:
This work is supported by funding from the Whitaker Foundation, Epilepsy Foundation, American Epilepsy Society, University of Pennsylvania Research Foundation, Jim Jacoby, and the National Institutes of Health grant #MH-62298RO1. Drs. Litt, Esteller, Echauz, and Vachtsevanos are founders of a small company, IntelliMedix, which supports this research. The authors express their appreciation to Steven Cranstoun, Peter Crino, Francisco Gonzalez-Scarano, Steven Scherer, Dasakumar Navaratnam, Leif Finkel, and David Raizen for reviewing this manuscript.