Abstracts

Rationale: To evaluate the utility of a bilateral multistage approach with intracranial EEG using subdural electrodes in epilepsy surgery. Methods: We reviewed the records of 11 patients (M 8/F 3, mean age 11.3 years, range 6 months-21 years) with medically intractable epilepsy who underwent bilateral invasive EEG monitoring at Cincinnati Children s Hospital Medical Center between October 2006 and November 2009. Clinical characteristics, presurgical evaluation, intracranial EEG findings, type of surgery, and surgical outcome were observed. Results: The reason for bilateral multistage approach included unlocalizing ictal onset on scalp EEG (5/11, 45%), bilateral independent ictal onset on scalp EEG (4/11, 36%), discordance between MRI abnormality and ictal onset on scalp EEG (1/11, 9%) and bilateral MRI abnormality (1/11, 9%). In six (55%) patients, subdural grid was placed in one selected hemisphere for the second stage, based on ictal EEG findings during bilateral monitoring as the first stage. Ten (91%) patients underwent resective surgery following bilateral invasive EEG monitoring, and five (50%) out of 10 achieved seizure-freedom at least 6 month follow-up. In one patient, subdural electrodes were removed without resective surgery since ictal EEG showed bilateral synchronous onset in both hemispheres. No patient experienced major complication due to subdural electrodes placement. Conclusions: Our results suggest that multistage approach using bilateral subdural electrodes is safe and effective in a challenging and selected epilepsy patient group.