Investigators at Universities of Cincinnati, OH, and Birmingham, Alabama; and Montreal Neurological Institute, Canada, studied the EEG and functional magnetic resonance imaging (fMRI) in 89 patients with idiopathic generalized epilepsy (IGE), (25 with generalized spike and wave discharges (GSWD) identified in EEG), and compared patients with valproate (VPA)-refractory and VPA-responsive IGE. The fMRI blood oxygen-level dependent (BOLD) correlates of GSWD in the entire group of patients involved midline thalamus, frontal regions and temporal lobes. A comparison of VPA-responsive and VPA-resistant patients showed BOLD signal increases in the VPA-resistant patients in medial frontal cortex, along the paracingulate gyrus and anterior insula bilaterally. VPA-resistant and VPA-responsive patients have different GSWD generators that may explain the reason for different responses and resistance to VPA in some cases. [1]
COMMENT. The combining of EEG and fMRI is a noninvasive method of investigation of brain regions involved at the time of epileptic discharges [2]. Neuronal discharges during an interictal spike or spike-wave burst result in increased metabolism and blood flow, reflected in the blood oxygen-level dependent (BOLD) signal measured by fMRI. EEG-fMRI helps localize epileptic foci in nonlesional frontal lobe epilepsy; it also demonstrates thalamic involvement in generalized epileptic discharges.