Current Source Distribution of Periodic Lateralized Epileptiform Discharge: Comparison With Diffusion-Wighted MR Imaging in Viral Encephalitis

ABSTRACT

BACKGROUND: Periodic lateralized epileptiform discharges (PLEDs) are the main electroencephalograph (EEG) findings that imply the existence of acute or subacute structural lesions. The purpose of this study was to investigate the electrophysiologic characteristics of PLEDs by identifying the relationship between the current-source distribution (CSD) of PLEDs and the high signal intensity of diffusion-weighted magnetic resonance imaging (MRI; HSI-DWI) in viral encephalitis. METHODS: Six patients were enrolled. Twenty typical EEG, 1-s epochs, including the negative peak of the PLEDs, were averaged into an averaged-PLED (a-PLED). The CSD at the negative peak point of the a-PLED was located on the Talairach human brain map in each patient. The CSDs of the patients were compared with the anatomic locations of encephalitic lesions observed on diffusion-weighted MRI. RESULTS: In all patients, the locations with HSI-DWI were observed in the cortical areas. In two out of the six patients the locations of CSD and those of HSI-DWI were matched. In the other patients, they were partly matched. The matched areas were observed in the frontal, temporal, and parietal areas. The additional areas of CSD were in both insular areas, and those of HSI-DWI were in the frontal, temporal, parietal, and occipital areas. CONCLUSIONS: This study showed that the CSDs of PLEDs in viral encephalitis were mostly matched with the HSI-DWI in the cortical area of the frontal, temporal, and parietal areas. The cortical lesion itself in viral encephalitis may be part of the neural generator of PLEDs.