Significance of focal and lateralized beta activity in the EEG.

In a group of 16,432 EEGs studied in a five year period, a total of 43 with focal, lateralized or paroxysmal beta activity were noted. The focal beta activity was mainly seen in children suffering from intractable seizures secondary to A-V malformation, porencephalic cysts or tumors. This was practically an epileptiform discharge with a high clinical pathologic correlation. The lateralized beta activity was seen mainly in adults suffering from cerebrovascular disease or tumor. In the cerebrovascular group the lateralized activity was seen on the contra-lateral side of the lesion. The paroxysmal beta activity is a rare phenomenon seen purely as an ictal manifestation, and mainly seen in children with Lennox-Gastaut Syndrome or infantile spasms. The importance of proper technique to record such abnormalities is emphasized.