Abstracts

Epilepsy Surgery is a standard of care in the treatment of intractable epilepsy. Intracranial electrodes can help identify surgical candidates when discordant information is present from the extracranial evaluation. We analyzed our experience with intracranial electrodes over 6 years., Two-hundred and fifty-eight resective epilepsy surgeries were performed from 2000-2006, with a mean follow-up of 2.6 years (range 2-65 months). Twenty-nine females and 21 males with a mean age of 29.4 years were implanted using an electrode array based upon the results of a standardized, non-invasive, pre-surgical evaluation. All patients were implanted at a single tertiary care epilepsy center between 2000-2006 by one neurosurgeon. Discordant information following a non-invasive evaluation including scalp-based video-EEG monitoring was obtained in each case. Resective surgical procedures, implanted array, and outcome were assessed. Outcome was reported as seizure-free, seizure improved ([gt]50% of baseline), and no improvement, and was based upon information obtained at the time of last contact., Fifty epilepsy patients (19.4%) were implanted with intracranial electrodes. Twenty-four patients (48%) had bitemporal placement, 15/50 (30%) were unilateral, and 11/50 were bilateral-extratemporal (22%). Thirty-seven (74%) underwent resective epilepsy surgery, and 13/50 (26%) were rejected as surgical candidates. Seizure freedom or improvement was noted in 9/14 (64.3%) implanted with unilateral electrodes, 14/24 (58.3%) with bitemporal electrodes, and 4/10 (40.0%) with bilateral-extratemporal electrodes.
Resections were temporal in 27/37 (73.0%), and extratemporal in 10/37 (27%) including frontal in 6/37 (12.5%), multi-lobar in 2/37 (5.4%), parietal in one (2.7%), and occipital in one. At last follow-up, 21/27 (81.4%) of the temporal resections were either seizure free (33.3%) or seizure improved (48.1%). Only 5/27 (13.5%) failed temporal surgery, compared with 3/8 (37.5%) extratemporal resections. MRI demonstrated an abnormality in 19/50 (38%) with neuronal migrational disorders accounting for the most common cause. The presence of a lesion did not have a more favorable outcome (8/19; 42.9%) than those with cryptogenic causes (18/29; 62.1%) (p=0.24, Fisher[apos]s exact test)., Most epilepsy patients requiring intracranial electrodes will be candidates for resective surgery. Bitemporal electrode placement for lateralization, and temporal resections were the most frequent surgeries performed. Patients implanted only with bitemporal electrodes, were not more likely than those with a lateralized array to benefit from resective surgery. Those with lesional epilepsy had no more favorable outcome than those with a cryptogenic etiology in our series.,