Diagnostic yield of high-density versus low-density EEG: The effect of spatial sampling, timing and duration of recording.

Objective: To investigate the effect of spatial sampling and of recording duration on the diagnostic yield of EEG for identification of interictal epileptiform discharges (IEDs). Previous studies demonstrated that high-density (HD) recordings increased accuracy of localization compared to low-density (LD) recordings.

Methods: We have prospectively evaluated the effect of spatial sampling and of recording duration in patients who had short-term (ST) recordings with a HD array of 256 electrodes following long-term (LT) recordings with a LD array consisting of the standard IFCN array of 25 electrodes.

The slow-wave component of the interictal epileptiform EEG discharges.

The interictal epileptiform discharges (IEDs) consist of a fast component (FC; spike or sharp-wave) followed by a slow-wave component (SC). Our purpose was to assess the intra-individual variance, the diagnostic significance and the effect of sleep on the SC. Ninety-nine EEG recordings from 50 consecutive patients with IEDs were analysed.