Visible fast oscillations recorded around periodic spasms. (a) Ictal encephalographic (EEG) recordings around the occurrence of periodic spasms. A mixture of sharp waves and slow waves were seen just before spasms at P4, T4, and T6 (time constant, 0.1 s). (b) Expansion of the EEG recording in Figure 2a encircled by the black line. Fast rhythmic waves were seen at C4, P4, T4, T6, and O2 (underlined) (band pass filter ranging from 5.7 to 120 Hz).