What it looks like
Transients that stand out from the background, with a sharp peak, an asymmetric rise and fall, an after-going slow wave and a believable field. Spikes last 20–70 ms, sharp waves 70–200 ms; the distinction has no clinical weight. 3,4
What it means at the bedside
In the right clinical setting these support a diagnosis of focal epilepsy; alone they do not make one. Around 0.5% of healthy adults carry epileptiform discharges. 21 Switch montage in the viewer: the phase reversal at F7/T7 in the bipolar chain becomes the largest deflection in the average reference.