Abstracts

Rationale: Periodic lateralized epileptiform discharges (PLEDs) is an EEG finding and it may imply acute or subacute structural lesions. The lesions may be in the cortical gray matter. Current source analysis (CSA) for PLEDs has been received little attention. The purpose of this study is to analyze the current source distribution of PLEDs in encephalitic patients and correlate that with the structural lesions. Methods: Five encephalitic patients with PLEDs were enrolled in this study. Typical 1 sec epochs including the negative peak of PLEDs were selected from the EEGs. These selected epochs were averaged into a single averaged lateralized epileptiform discharge (av-LED). The current source densities (CSDs) of the negative peak points of the av-LEDs were located on the Talairach human brain map. The CSDs were compared with the anatomic locations of encephalitic lesions observed in diffusion-weighted MRI (DWI). Results: In all five patients, the encephalitic lesions in DWI are observed in the cortical areas but not in the subcortical areas. In one of five patients the locations of CSDs and the locations of high signal intensities of DWI (HSI-DWI) are exactly matched and those were in the medial and lateral temporal areas. In two of five patients, the more areas of CSDs were observed than the areas of HSI-DWI. Vice versa was observed in the other two patients. The matched areas observed in all five patients were in the cortical areas of the medial and lateral frontal, and medial and lateral temporal areas. And the mismatched areas of HIS-DWI were in the medial and lateral parietal, lateral temporal and medial parietooccipital areas. The mismatched areas of CSDs were in the medial frontal, anterior and lateral temporal, lateral parietal and medial frontoparietal areas. Conclusions: This study revealed that the CSDs of PLEDs were matched with the HSI-DWI of encephalitis in frontal and temporal areas but not in the parietal and occipital areas. Thus PLEDs may be easily generated when the encephalitic lesions are located in the frontal or temporal cortex of the cerebral hemisphere. In encephalitis, the cortical lesions involving frontal and/or temporal area may be the neural generators for PLEDs.