Abstracts

Magnetoencephalography (MEG) is increasingly used for mapping interictal spikes as a part of pre-surgical evaluation of epilepsy. However, the reliability and relative importance of this method are not studied well. We retrospectively investigated pre-surgical MRI and MEG findings in relation to post-operative seizure outcome in patients with refractory temporal lobe epilepsy (TLE)., Medical records were reviewed for 42 consecutive patients with medically refractory TLE who 1) had interictal MEG recording as a routine pre-surgical evaluation and 2) had resective surgery of temporal lobe between January 2002 and October 2004 at our institution. The relationship of pre-operative MRI and MEG findings to post-operative seizure outcome was investigated., Hippocampal atrophy on pre-operative MRI or MEG spike localization was not significantly associated with post-operative outcome. In patients with hippocampal atrophy (n=28), all cases (n=15) with anterior temporal (AT) spikes underwent standard anterior temporal lobectomy (ATL), and those with non-AT spikes (n=11) underwent either ATL alone (n=6) or ATL combined with multiple subpial transection (MST) or tailored neocortical resection (n=5) based on intra-operative elecrocorticogram (ECoG) findings, resulting in similar seizure outcome in both groups. In patients without hippocampal atrophy, surgical strategy was various among patients depending on location of lesion and intra-operative ECoG findings. MEG spike pattern was not strongly associated with post-operative outcome., Our case series did not reveal significant relationship between MEG spike patterns and post-operative seizure outcome, partly because of small size of study. However, in patients with hippocampal atrophy, non-AT spikes were associated with the use of MST or tailored cortical resection in addition to the standard temporal lobectomy. This suggests that MEG is not always critical in defining the epileptogenic zone or in predicting post-operative outcome in TLE, but may be useful in modifying surgical strategy for better seizure outcome.,