Intra-lesional stereo-EEG activity in Taylor 's focal cortical dysplasia.

Focal cortical dysplasia are a frequent histological finding in epilepsy surgery series. Among the different types of focal cortical dysplasia, distinctive anatomical, electrical and clinical details have been identified for Taylor's focal cortical dysplasia, and in a recent article we reported a better post-surgical outcome in Taylor's focal cortical dysplasia than in other histological subtypes of cortical dysplasias. In the present study, we analysed the intra-lesional electrical activity directly recorded inside Taylor's focal cortical dysplasia during a stereo-EEG diagnostic procedure in 21 patients selected from among the 27 cases in which post-operative neuropathological examination demonstrated this kind of lesion. Our data show the existence of a peculiar interictal pattern characterised by the presence of repetitive and rhythmic spike and poly-spike and wave, frequently associated with short bursts of fusiform micro poly-spikes. Moreover, an almost pathognomonic ictal pattern (mid-amplitude 14-18 Hz rhythmic activity followed by a low voltage recruiting fast activity) is present in 12 of these 21 patients. These electrical peculiarities suggest a high level of epileptogenicity of Taylor's focal cortical dysplasia and could possibly explain the high percentage of post-surgical success among patients with this kind of lesion.