The relation between lesions and localization of sources of slow biphasic complexes in encephalitis

Abstract

Slow biphasic complexes (SBC) were found in the electroencephalogram (EEG) of patients with inflammations of the brain. We have developed an automated method to identify them and proved that they represent a sensitive marker of the severity of encephalitis. Here we focus on another property of SBCs, i.e., the localization of their sources. We present two encephalitic patients, showing lesions in the magnetic resonance images, which are either spread in the brain or focused on the left hemisphere, respectively. Applying a source localization algorithm to the identified SBCs, we found either a diffused or a left-focused distribution, respectively. This result further suggests a relation between neuroinflammation and appearance of SBCs, indicating that their distribution reflects in part the localization of brain lesions. This promising result extends the information that can be extracted from EEG, promoting the reduction of expensive or invasive measurements in encephalitic patients.

Automated diagnosis of encephalitis in pediatric patients using EEG rhythms and slow biphasic complexes

“…Further studies are needed to assess other interesting properties of the SBCs. For example, their sources could be investigated, by estimating their locations [17,18], which could be then correlated with the lesions found in neuroimages (some promising results were obtained recently [56]). Deepening the study of SBCs could also be of help in improving their identification by adding some a-priori constraints to the processing algorithm.…”

Functional Connectivity of EEG in Encephalitis during Slow Biphasic Complexes

“…The slow biphasic complex (SBC) has been observed for decades in the EEG of patients with different brain inflammations [16][17][18]: Rasmussen's syndrome [19][20][21][22][23][24], human immunodeficiency virus (HIV) [25][26][27], West syndrome [17,18] and encephalitis [25]. Interesting properties of SBCs have been recently discovered, based on an automated method to identify them [28], which has allowed the quantifying of their appearance, amplitude, distribution and their relation with the severity of encephalitis [28,29], localization of lesions [30] and EEG rhythms [31]. Specifically, it was found that their number and cumulative amplitude increase with severity [28,29] and that the distribution of their sources is related to the regions in which lesions are detected in magnetic resonance images [30].…”

“…Interesting properties of SBCs have been recently discovered, based on an automated method to identify them [28], which has allowed the quantifying of their appearance, amplitude, distribution and their relation with the severity of encephalitis [28,29], localization of lesions [30] and EEG rhythms [31]. Specifically, it was found that their number and cumulative amplitude increase with severity [28,29] and that the distribution of their sources is related to the regions in which lesions are detected in magnetic resonance images [30]. Moreover, it was recently observed that the EEG is slower in short epochs before the onset of an SBC than in the rest of the trace [31].…”