Abstracts

Idiopathic generalized epilepsies (IGE) are a group of epilepsies with generalized onset of the seizures. According to the main seizure type IGE are divided in subsyndromes. Routine magnetic resonance imaging (MRI) is normal. The EEG supports the diagnosis when it shows the typical generalized spike and wave (GSW) discharges with normal background. Despite of these features, sometimes focal epileptiform discharges may be registered in the EEG. Some authors believe that these focalities represent fragmented GSW discharges but the pathophysiology of the focalities is still under investigation. Voxel-based morphometry (VBM) is a quantitative technique of MRI analysis that allows automatic comparison between images. This method also increases the sensibility to detect small areas of structural abnormalities. The objective of this study was to investigate the focalities present on the EEG records of patients with IGE using VBM., Patients were classified according to clinical and EEG features following previous recommendations. All patients had at least one EEG with typical GSW discharges and one with clear focal epileptiform discharges. All patients were submitted to MRI evaluation in a 2T MRI scanner (Elscint, Haifa, Israel). A 3D T1 gradient echo sequence with 1 mm isotropic voxels was used for VBM analysis. Images were previously processed using the software SPM2 (www.fil.ion.ucl.ac.uk). All images were submitted to spatial normalization, automatic segmentation, modulation and smoothing. The images of each patient were individually compared with a group of 47 controls (23 women, mean age 32 [plusmn] 14, range 19-67). Statistical analysis was performed searching for areas of gray matter concentration (GMC) abnormalities. The statistical level selected was a corrected [italic]p[/italic][lt]0.05 (false discovery rate). The localization of the focal discharges on the EEG was compared to the VBM results., Twenty-two patients with IGE diagnosis were evaluated. Nine had juvenile myoclonic epilepsy (JME), 6 patients had absence epilepsy (AE) and 7 had generalized tonic-clonic seizures on awakening (GTCS). Eight of the 9 (89%) patients with JME presented areas of GMC abnormalities. EEG analysis showed correspondence in 6 of 8 patients (75%). Five of 6 (83%) patients with AE presented areas of GMC abnormalities. EEG analysis showed correspondence in 3 of 5 patients (60%). Five of 7 (71%) patients with GTCS presented areas of GMC abnormalities. EEG analysis showed correspondence in 2 of 5 patients (40%)., This study supports that subtle structural abnormalities characterized mainly by increased GMC may be responsible for the focal epileptiform discharges observed in the EEG of IGE. These focalities are also probably involved in the pathophysiology of the IGE., (Supported by Funda[ccedil][atilde]o de Amparo [agrave] Pesquisa do Estado de S[atilde]o Paulo (FAPESP) and Coordena[ccedil][atilde]o de Aperfei[ccedil]oamento de Pessoal de N[iacute]vel Superior (CAPES).)