Abstracts

Rationale: Focal Cortical Dysplasia (FCD) is a major cause of intractable epilepsy of infants and children which usually results in catastrophic prognosis and severe developmental delay. Accurate diagnosis of FCDs are highest priority for child neurologist to provide patients the opportunity of surgical resection which can lead freedom from catastrophic seizures and normal development. Some of the FCDs should be found easily in MRI but the others are not and these cases are likely to have medication therapy which usually results in miserable prognosis. Our aim is to detect FCD directly by analyzing the shape of MEG spikes, using spatial filtering analysis: dynamic statistical parametric mapping (dSPM) which enables to show epileptiform activity with spatiotemporal source distribution with millisecond temporal resolution (Dale,2000). Methods: We studied 10 patients (mean±DS; 17.6±10.5 years old) with symptomatic localization-related epilepsy using a 204-channel, whole-head gradiometer system (Vecterview, Elektra Neuromag Inc., Stockholm, Sweden). We divided FCD group and Non-FCD group according to the pathologic diagnosis and existence of FCD in Magnetic resonance imaging (MRI). We selected 10 epileptic spikes from each patient and analyzed by dSPM. We projected the results to normal standard brain model to minimize the differences in shapes between the patients' brain. Thus, we investigated characteristic features of epileptic spikes by analyzing strength and temporal activity of epileptiform. Results: The form of epileptic spike in FCD group is single and sharp in peak, emerging and vanishing in a same location of the brain without expanding its area. In contrast, that of Non-FCD group is multiple and diverse, expanding the area to the circumference and vanishing toward different lobe. A case categorized as Non-FCD group with no lesion in MRI initially revealed to have the same epileptic activity as FCD group which indicates the existence of FCD. This patient underwent cortical resection and became seizure free. Conclusions: Functional analysis of MEG with dSPM can disclose the characteristic features of epileptic spikes with high spatial and temporal resolution. This method will help diagnose the existence of FCD as well as MRI invisible cases.