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If we had a warning that a seizure was about to happen we might be able to do something to prevent it. Neither clinical observation nor conventional electroencephalography analysis is able to give adequate warning. The standard electroencephalogram (EEG) pattern is either interictal or ictal. Now researchers in France and Belgium (Michel Le Van Quyen and colleagues.Lancet2001;357:183–8; see also commentary, Ibid:160–1) have described a preictal phase lasting for several minutes. The detection of this preictal phase depends on non-linear analysis and the measurement of similarity between segments of the EEG recording distanced in time. Using this technique a preictal phase, detected using intracranial electrode recordings, was described in 1998. The observation has now been extended to standard scalp electrode recordings. Twenty three patients with refractory temporal lobe epilepsy (ages not stated) were studied, 18 using scalp electrodes only and five using both scalp and intracranial electrodes. Twenty six recordings beginning 30–60 minutes before a seizure were analysed and a preictal phase was detected in 25. This phase lasted 1–20 minutes (mean 7 minutes) before the onset of clinical or EEG seizure activity. The findings using scalp and deep electrodes were similar. More work needs to be done to establish the sensitivity and specificity of these changes and whether they are found in other forms of epilepsy. Nevertheless, the possibilities arise of long term monitoring and preseizure intervention by automated drug administration or intracranial stimulation, or the use of cognitive techniques.