Epileptic Seizures May Begin Clinical Study Hours in Advance of Clinical Onset: A Report of Five Patients

Summary In recent years, clinical epilepsy monitoring has en-abled studying human seizures quantitatively, as they Mechanisms underlying seizure generation are tradi- developinvivo.Thisefforthasbeenaidedbytechnologi- tionally thought to act over seconds to minutes before cal advances such as digital video-EEG monitoring sys- clinical seizure onset. We analyzed continuous 3- to temsthatcanprocessdatainrealtime,andsafe,reliable 14-day intracranial EEG recordings from five patients electrodes for implantation directly on or in the brain with mesial temporal lobe epilepsy obtained during (intracranial electrodes). Most work in quantitative anal- evaluation for epilepsy surgery. We found localized ysis of human seizures has focused on detecting their quantitativeEEGchangesidentifyingprolongedbursts electrical onset on EEG in the up to 10 s that may pre- of complexepileptiform dischargesthat becamemore cede their first clinical signs (clinical onset) (Gotman, prevalent 7 hr before seizures and highly localized