Single-pulse electrical stimulation helps to identify epileptogenic cortex in children

P>Purpose: The usefulness of single-pulse electrical stimulation (SPES) during intracranial recordings was evaluated in a pediatric population. This method is useful in identifying epileptogenic cortex in adult subjects. Methods: We studied 35 children who were undergoing intracranial electroencephalography (EEG) recordings from two hospitals (King's College Hospital and Great Ormond Street Hospital for Sick Children, London, United Kingdom). In each patient we studied all available contacts using a series of 10 or more single, brief (1 ms) electrical stimuli. The cortical responses were reviewed in detail. The data were examined for associations between response type, ictal onset zone, lesion boundary, and seizure outcome. Results: We identified cortical responses to SPES that were similar to those reported in adults. In agreement with previous studies we found that two types of responses ("delayed" and "repetitive" responses) were associated with the ictal onset zone and the area of the presumed epileptogenic lesion. When these responses were present (54% of cases), the removal of the entire area responsible for the abnormal responses to SPES was associated with good outcome. Conclusion: Cortical responses to SPES in children provide new and additional information in the investigation of epileptogenic cortex in children during assessment for epilepsy surgery. This may improve the outcome for this difficult but important group.