Stereo-EEG: the Sainte-Anne experience in focal cortical dysplasias

Focal cortical dysplasias represent a cause of intractable epilepsy that can be cured by surgery if complete lesional resection can be performed. However, the lesional limits are difficult to assess by imaging, and some focal cortical dysplasias can be missed by magnetic resonance imaging. The combination of high-resolution magnetic resonance imaging and neurophysiological findings provided by direct intra-lesional recordings has greatly improved diagnosis and surgical outcome in focal cortical dysplasias. Stereo-EEG has demonstrated that dysplastic areas show continuous spiking activity persisting after diazepam injection and are the site of ictal discharge onset. Surgery guided by stereo-EEG made seizure-free outcome possible for all patients recently investigated and who had undergone surgery in our centre for extra-temporal partial epilepsy associated with focal cortical dysplasias (10 patients, mean follow-up: 15 months). Moreover, we demonstrated that limited resections can be performed safely in eloquent cortex without permanent disability. These results demonstrate the usefulness of stereo-EEG in surgical treatment for focal cortical dysplasias, despite the invasive nature of this procedure.