Abstracts

Rationale: The aim of this study was to retrospectively examine whether video electroencephalography (vEEG) is really necessary as a diagnostic tool to help localize seizure foci in patients who have evidence of mesial temporal sclerosis (MTS) on MRI testing and other signs of temporal lobe epilepsy from seizure semiology, EEG and Neuropsychological testing.Methods: 79 patients from the Epilepsy Programme at the University of Western Ontario in London, Ontario, Canada over the past 20 years fit our study’s inclusion criteria which consisted of patients having undergone a temporal lobectomy or selective amygdala hippocampectomy who had evidence of MTS on presurgical MRI testing. Information on their age of seizure onset, age at evaluation, handedness, seizure semiology, EEG results, Neuropsychological test results , vEEG results, MRI results and location and type of surgery were recorded. Two epileptologists who were blinded to the actual final surgical decisions and each other’s decisions were presented with the same workup information without the video-EEG results and they either decided which side the patient should be operated on or whether the patient would needed further diagnostic tests (e.g. video-EEG and/or subdural electrodes) to localize the seizure foci for the purpose of surgical resection. The doctors then compared seizure localization decisions with each other and came up with an agreed upon decision for each patient. This was then compared to what was actually done for the patient.Results: There was “fair agreement” between the two epileptologists (Kappa score of 0.244) who were blinded to the video-EEG results and actual decision made. The combined decision by the two doctors on 40 out of the 79 patients were the same as what was actually done. Of the remaining 39 who they felt needed video-EEG to help localize the seizure foci for resection, 11 needed even further invasive testing (namely subdural electrodes) before planning for surgical resection could be completed.Conclusions: In 50% of people with epilepsy with neuropsychological tests, and EEG and evidence of mesial temporal sclerosis on MRI, it seems like video-EEG is not needed for seizure foci localization. Of the remaining 50% though that need video-EEG, around 1/3 require even further invasive testing (subdural electrodes) for localization.