Periodic Lateralized Epileptiform Discharges

Figure 1. Electroencephalography in a 13-year-old boy with fever, altered sensorium, and sudden onset of seizures reveals complex repetitive discharges composed of spiky elements mixed with slower waveforms (Panel A). They are seen diffusely in the left (L) hemisphere (leads 1 to 8), occurring at intervals of approximately 2.5 seconds (arrows). The right (R) hemisphere (leads 11 to 18) shows abnormally slow background activity of 2 Hz per second (delta rhythm) compatible with the presence of acute encephalopathy. For comparison, an electroencephalogram obtained in a normal, awake subject is shown in Panel B. There is normal background activity of 11 . . .