title: Analysis of generalized interictal discharges using quantitative EEG.
abstract: Experimental evidence from animal models of the absence seizures suggests a focal source for the initiation of generalized spike-and-wave (GSW) discharges. Furthermore, clinical studies indicate that patients diagnosed with idiopathic generalized epilepsy (IGE) exhibit focal electroencephalographic abnormalities, which involve the thalamo-cortical circuitry. This circuitry is a key network that has been implicated in the initiation of generalized discharges, and may contribute to the pathophysiology of GSW discharges. Quantitative electroencephalogram (qEEG) analysis may be able to detect abnormalities associated with the initiation of GSW discharges. The objective of this study was to determine whether interictal GSW discharges exhibit focal characteristics using qEEG analysis. In this study, 75 EEG recordings from 64 patients were analyzed. All EEG recordings analyzed contained at least one GSW discharge. EEG recordings were obtained by a 22-channel recorder with electrodes positioned according to the international 10-20 system of electrode placement. EEG activity was recorded for 20 min including photic stimulation and hyperventilation. The EEG recordings were visually inspected, and the first unequivocally confirmed generalized spike was marked for each discharge. Three methods of source imaging analysis were applied: dipole source imaging (DSI), classical LORETA analysis recursively applied (CLARA), and equivalent dipole of independent components with cluster analysis. A total of 753 GSW discharges were identified and spatiotemporally analyzed. Source evaluation analysis using all three techniques revealed that the frontal lobe was the principal source of GSW discharges (70%), followed by the parietal and occipital lobes (14%), and the basal ganglia (12%). The main anatomical sources of GSW discharges were the anterior cingulate cortex (36%) and the medial frontal gyrus (23%). Source analysis did not reveal a common focal source of GSW discharges. However, there was a predominance of GSW discharges originating from the cingulate gyrus and the frontal lobe.
authors.affiliation: Departamento de Neurologia, Psiquiatria e Psicologia Faculdade de Medicina de Botucatu - UNESP - Univ Estadual Paulista, Brazil.
authors.forename: Aline Marques
authors.initials: AM
authors.lastname: da Silva Braga
authors.affiliation: Departamento de Neurologia, Psiquiatria e Psicologia Faculdade de Medicina de Botucatu - UNESP - Univ Estadual Paulista, Brazil.
authors.forename: Elaine Keiko
authors.initials: EK
authors.lastname: Fujisao
authors.affiliation: Departamento de Neurologia, Psiquiatria e Psicologia Faculdade de Medicina de Botucatu - UNESP - Univ Estadual Paulista, Brazil. Electronic address: betting@fmb.unesp.br.
authors.forename: Luiz Eduardo
authors.initials: LE
authors.lastname: Betting
mesh_terms: D000328:Adult; D001921:Brain / Q000503:physiopathology*; D001931:Brain Mapping; D016000:Cluster Analysis; D004569:Electroencephalography / Q000379:methods*; D004829:Epilepsy, Generalized / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006985:Hyperventilation; D008297:Male; D010775:Photic Stimulation; D012815:Signal Processing, Computer-Assisted; D014054:Tomography / Q000379:methods
keywords: EEG; Electroencephalogram; Generalized spike-and-wave discharges; Idiopathic generalized epilepsy; Quantitative EEG; qEEG