A storm of fast (40-150Hz) oscillations during hypsarrhythmia in West syndrome

Objective Fast oscillations (FOs) were first explored from scalp electroencephalographic (EEG) data from hypsarrhythmia in West syndrome (infantile spasms) to investigate the meaning of FOs in this epileptic encephalopathy. Methods In 17 infants with West syndrome, we conservatively detected fast frequency peaks that stood out from the time-frequency spectral background with square root power > 1µV (spectral criterion) and corresponded to clear FOs with at least 4 oscillations in the filtered EEG traces (waveform criterion) in sleep EEGs. Results We found a total of 1,519 interictal FOs that fulfilled both the spectral and waveform criteria. The FOs with a median frequency of 56.6Hz (range = 41.0–140.6Hz) were dense, with a median rate of 66 (range = 24–171) per minute before adrenocorticotropic hormone (ACTH) treatment, which was significantly higher than that in control infants without seizures (median = 1, p